ZOOLOGICAL PHILOSOPHY

ZOOLOGICAL
PHILOSOPHY

3

LI

AN EXPOSITION WITH REGARD TO THE
NATURAL HISTORY OF ANIMALS

THE DIVERSITY OK THEIR ORGANISATION AND THE FACULTIES WHICH THEY

DERIVE FROM IT: THE PHYSICAL CAUSES WHICH MAINTAIN LIFE WITHIN

THEM AND GIVE RISE TO THEIR VARIOUS MOVEMENTS ; LASTLY, THOSE WHICH

PRODUCE FEELING AND INTELLIGENCE IN SOME AMONG THEM

BY

J. B. LAMARCK

TRANSLATED, WITH AN INTRODUCTION, BY

HUGH ELLIOT

AUTHOR OF "modern SCIENCF. AND THE ILLUSIONS OP PROFESSOR BERGSON '
EDITOR OF "the LETTERS OF JOHN STUAKT MILL," ETC., ETC.

H

HAFNER PUBLISHING COMPANY

New York and London
1963

Originally published in 1914
by Macmillan and Co., Ltd.

Reprinted by Arrangment

Printed and Published by

HAFNER PUBLISHING CO., INC.

31 East 10th Street

New York 3, N.Y.

Library of Congress Catalog Card Number: 63-10745

Printed in U.S.A. by

NOBLE OFFSET PRINTERS, INC.
NEW YORK 3, N. Y.

TABLE OF CONTENTS

PaOC

Introduction xvii

Life — The Philosophie Zoologique — Zoology — Evolution — In-
heritance of acquired characters — Classification — Physiology —
Psychology — Conclusion.

Preface

Object of the work, and general observations on the subjects
dealt with in it.

Preliminary Discourse 9

Some general considerations on the interest of the study of
animals and their organisation, especially among the most
imperfect.

PAKT I.

CONSIDERATIONS ON THE NATURAL HISTORY OF ANIMALS, THEIR
CHARACTERS, AFFINITIES, ORGANISATION. CLASSIFICATION
AND SPECIES.

CHAP.

I. On Artificial Devices in dealing with the Pro-
ductions OF Nature 19

How schematic classifications, classes, orders, families, genera
and nomenclature are only artificial devices.

II. Importance of the Consideration of Affinities - 29

How a knowledge of the afl&nities between the known natural
productions lies at the base of natural science, and is the funda-
mental factor in a general classification of animals.

III. Of Species among Living Bodies, and the Idea that

WE should attach to that word - - - 35

That it is not true that Species are as old as Nature, and have
aU been in existence for an equal period ; but that it is true that
they have been formed one after another, that they have only a rela-
tive constancy, and are only invariable temporarily.

viii TABLE OF CONTENTS

CHAP. PAOB

IV. General Principles concerning Animals - - - 47

The actions of animals only take place by means of movements
that are stimulated, and not transmitted from without. Irri-
tability is a faculty which they all possess, and is not found except
in animals : it is the source of their actions. It is not true that
all animals possess feeling, nor the faculty of carrying out acts
of will.

V. On the True Arrangement and Classification of

Animals 56

That animals may be arranged, as regards their larger groups,
in a series which exhibits a gradually increasing complexity of
organisation ; that the knowledge of the affinities between the
various animals is our only guide in determining this series, and
that the use of this method dispenses with arbitrary judgments ;
lastly, that the number of the lines of demarcation, by which
classes are established, has to be increased in correspondence with
our knowledge of the different systems of organisation, so that the
series now presents fourteen distinct classes, of great service in
the study of animals.

VI. Degradation and Simplification of Organisation,
from one Extremity to the other of the Ani-
mal Chain, proceeding from the most complex

TO THE simplest - - 68

That it is a positive fact that on following the animal chain in
the usual direction from the most perfect to the most imperfect
animals, we observe an increasing degradation and simplification
of organisation ; that, consequently on traversing the animal
scale in the opposite direction, that is to say, in the same order
as Nature's, we shall find an increasing complexity in the organisa-
tion of animals, a complexity which would advance with evenness
and regularity, if the environmental conditions, mode of life, etc.,
did not occasion many anomalies in it.

VII. Of the Influence of the Environment on the
Activities and Habits of Animals, and the
Influence of the Activities and Habits of these
Living Bodies in modifying their Organisation
and Structure - ■ 106

How the environment acts upon the organisation, general form
and structure of animals ; how changes subsequently occurring
in their environment, mode of life, etc., involve corresponding
changes in the activities of animals ; lastly, how a change in the
activities, which has become permanent, involves on the one
hand more frequent use of certain parts of the animal, thus
developing and enlarging them proportionally ; while, on the
other hand, this same change diminishes and sometimes abolishes

TABLE OF CONTENTS ix

CHAP. PAOB

the use of certain other parts, thus acting unfavourably on their
development, reducing them, and finally causing their disappear-
ance.

(See the Additions at the end of Part I.)

VIII. Of the Natural Order of Animals, and the way
in which their classification should be drawn
up, so as to be in conformity with the actual
Order of Nature - 128

That the natural order of animals constitutes a series, which
we should traverse from the most imperfect animals to the most
perfect, in order to be in harmony with the order of Nature ; for
Nature did not bring them all into existence at the same moment.
Since she had to form them in turn, she was obUged to begin with
the simplest, and only produced at the end those with the most
complex organisation. That the classification presented here-
with is unquestionably the one that approaches most nearly to
the order of Nature ; so that if there are any corrections to be
made in it, it can only be in matters of detail ; 1 believe, for
instance, that the Naked Polyps should form the third order of
the class, and the Floating Polyps the fourth.

Additions to the Subject-matter of Chaps. VII. and VIII. 173

PART II.

AN ENQUIRY INTO THE PHYSICAL CAUSES OF LIFE, THE CON-
DITIONS REQUIRED FOR ITS EXISTENCE, THE EXCITING FORCE
OF ITS MOVEMENTS, THE FACULTIES WHICH IT CONFERS ON
BODIES POSSESSING IT, AND THE RESULTS OF ITS PRESENCE
IN THOSE BODIES.

Introduction - - - - - - - - - - 183

Some general considerations on nature, and her power to create
life and organisation, and subsequently to increase the complexity
of the latter. In all these operations, she works only by the action
of various moving fluids on supple bodies, which are modified,
organised, and animated by these fluids.

I. Comparison of Inorganic Bodies with Living Bodies,

FOLLOWED BY A PARALLEL BETWEEN AnIMALS

AND Plants 191

That there is a great difference between living bodies and inor-
ganic bodies. That animals are essentially distinguished from
plants by Irritability, which is possessed exclusively by the former,
and which enables their parts to make sudden movements, repeated
as often as they are stimulated by exciting causes, — a pecuharity
which does not occur in any plant.

TABLE OF CONTENTS

II. Of Life, what it consists of, and the Conditions of

ITS Existence in a Body 201

That life in itself is a purely physical phenomenon, which
gradually gives rise to many other phenomena, and which is due
exclusively to the relations existing between the adapted con-
taining parts of a body, the contained fluids moving in them, and
the exciting cause of the movements and changes which take
place in the body.

III. Of the Exciting Cause of Organic Movements - 211

That the organic movements, as also the movements which
constitute the actions of animals, are not communicated, but
etimulated by the activity of an exciting cause, which is not part
of the bodies it animates and does not perish like them ; that
this cause resides in the invisible, subtle, expansive fluids, con-
stantly in agitation, which penetrate into, or are incessantly
being developed in the bodies which they animate.

IV. Of Orgasm and Irritability 219

That the exciting cause of organic movements sets up in the
supple parts of living bodies, especially of animals, an orgasm
which is essential for the preservation of life ; and which, in the
case of animals, confers on the parts which possess it the faculty of
being irritable.

That Irritability is a faculty belonging exclusively to the supple
parts of animals, that it confers on them the power of producing
local manifestations which are repeated as often as the instigating
cause is brought to bear ; lastly, that this faculty is essentially
distinct from that of feeling.

V. Of Cellular Tissue, regarded as the Matrix in

which all Organisation has been cast - - 230

That cellular tissue is the universal matrix of aU organisation,
and that the movement of fluids in this tissue is the means employed
by nature for the creation and gradual development of the organs,
at the expense of the tissue in question.

VI. Of Direct or Spontaneous Generation - - - 236

That, since all living bodies are productions of nature, she
must herself have organised the simplest of such bodies, endowed
them directly with life, and with the faculties pecuHar to living
bodies.

That by means of these direct generations formed at the
beginning both of the animal and vegetable scales, nature has
ultimately conferred existence on all other living bodies in turn.

VII. Of the Immediate Results of Life in a Body - - 249

That it is not true that living bodies have the faculty of resisting
the laws and forces to which all non-living bodies are subject, nor

TABLE OF CONTENTS xi

CHAP. PAOK

that they are controlled by laws peculiar to themselves ; but, on
the contrary, that it is true that the laws, which regulate the
changes occurring in bodies, meet with very different conditions
in living bodies from those that they find in lifeless bodies, and
hence work upon the former results very different from those
worked upon the latter.

That living bodies have the faculty of building up their own
substance for themselves and thus forming combinations which
would never have come into existence without them ; hence their
remains furnish the material which serves for the formation of the
various minerals.

VIII. Of the Faculties common to all Living Bodies - 259

That life endows all bodies which possess it with certain faculties
in common, and that the production of these faculties requires no
special organ whatever, but only such a state of things in the
parts of these bodies as may enable life to exist in them.

IX. Of the Faculties peculiar to certain Living Bodies 265

That, in addition to the faculties conferred by life on all living
bodies, some living bodies have faculties which are altogether
peculiar to themselves. Now observation shows that these latter
faculties only arise, when special organs, capable of producing
them, exist in the animals possessing such faculties.

Summary of Part IL 280

PAET III.

AN ENQUIRY INTO THE PHYSICAL CAUSES OF FEELING, INTO THE
FORCE WHICH PRODUCES ACTIONS, AND LASTLY INTO THE
origin OF THE ACTS OF INTELLIGENCE OBSERVED IN
VARIOUS ANIMALS.

Introduction -285

Some general observations on the means possessed by nature,
for giving rise in living bodies to the phenomena known as sensa-
tions, ideas and the various acts of intelligence.

I. Of the Nervous System, its Formation, and the 291
various sorts of Functions that it can fulfil

That the system of organs, called the nervous system, is limited
to certain animals, and that among those which possess it, it is
found in different degrees of complexity and perfection ; that

xii TABLE OF CONTENTS

this system confers on some animals only the faculty of muscular
movement, on others this faculty together with that of feehng,
and on others again these two faculties together with that of forming
ideas, and of carrying out by this means various acts of intelli-
gence.

That the system of organs under examination fulfils four very
different kinds of functions, but only when it has reached a com-
plexity sufficient to give it the power of doing so.

II. Of the Nervous Fluid 314

That there is developed in the bodies of certain animals a very
subtle, invisible, containable fluid, remarkable for the rapidity
of its movements ; that this fluid has the faculty of exciting
muscular movement, and that by its means nerves which are
affected produce feeling ; that, when its entire mass is agitated, it
gives rise to inner emotions ; and that finally it is the singular
agent by which ideas and all intellectual acts are formed.

III. Of Physical Sensibility and the Mechanism op

Sensations - - - 321

That it is not true that any matter, or any part of a living body,
can have in itself the faculty of feeling ; but that it is true that
feeling is a phenomenon resulting from the functions of a special
system of organs capable of giving rise to it.

That feeling is the result of action upon the subtle nervous
fluid of an affected nerve, which is propagated throughout the
nervous fluid of the sensitive system, and is terminated by a
general reaction which is carried back to the individual's inner
feeling and to the point affected.

IV. Of the Inner Feeling, the Emotions that it may

experience, and the Power which it thence
derives for the production of actions - - 332

That the inner feeling results from the totality of internal
sensations produced by the vital movements, and from the fact
that all parts of the nervous fluid are in communication so as to
form a single though divided whole, which is capable of acquiring
those general agitations termed emotions.

That this inner feeling is the bond of union between the
physical and moral, and the origin of both ; that the feeling in
question on the one hand acquaints the individual with sensations
that he experiences (whence the physical) ; and, on the other
hand, gives him consciousness of his ideas and thoughts (whence
the moral) ; and lastly, as a result of emotions aroused by needs,
causes the individual to act without any participation of his will
(whence instinct).

TABLE OF CONTENTS xiii

CHAP. PAGE

V. Of the Force which produces the Actions of Ani-
mals, AND OF certain PECULIAR FACTS RESULTING
FROM THE USE OF THIS FORCE - - . - 343

That since muscular action is a power fully adequate for the
production of the movements performed by animals, and since
nervous influence is able to excite that muscular action, such
animals as have physical feeling possess in their inner feeling a
power quite capable of driving to the muscles the fluid which
excites their movements ; and it is in fact by its emotions that
this feeling obtains the force to work the muscles.

Of THE Consumption and Drainage of the Nervous

Fluid in the Production of Animal Actions - 348

Of the Origin of the Propensity towards repeating

THE Same Actions --.-.. 349

Of Instinct in Animals - 350

Of Skill in Certain Animals 353

VI. Of the Will -------- 355

That, since the will always results from a judgment, and since
a judgment necessarily arises from a comparison of ideas, a
thought, or some impression that causes it, every act of will is
an act of intelligence, and that consequently only animals with
a special organ for intelligence can carry out acts of will.

That, since the will always depends on a judgment, not only
is it never really free, but, since judgments are liable to numerous
causes of error, the will resulting from them is less reliable than
instinct in the inner feeling driven by some need.

VII. Of the Understanding, its Origin, and the Origin

of Ideas - - 362

That all acts of the understanding require a special system of
organs for their execution ; that acquired ideas are the material
of all operations of the understanding ; that although every idea
is originally a sensation, every sensation need not become an
idea, since a special organ is necessary for its formation, and the
sensation, moreover, has to be noticed ; finally, that, in all acts of
intelligence, the nervous fluid is the only active factor, in that it
moves in the organ concerned, while the organ itself remains
passive, simply providing for the diversity of the operations by
the diversity of its parts.

xiv TABLE OF CONTENTS

CHAP. PAQB

VIII. Op the Principal Acts of the Understanding, or

THOSE OF THE FiRST OrDER FROM WHICH ALL THE

REST ARE DERIVED 379

That the principal acts of the understanding are attention, a
special preparatory state of the organ, without which none of its
acts could be produced ; thought, from which spring complex
ideas of all orders ; memory, whose acts, named recollections,
recall ideas of any kind, by bringing them again to the inner
feeling, or consciousness of the individual ; and judgments, which
are the most important acts of the understanding, and without
which no reasoning, or act of will could be produced, nor any
knowledge be acquired.

Of Imagination - 388

Of Reason, and its Comparison with Instinct - 401

Index - 407

GLOSSARY

Giving the original French of some of the more important worda
used in the course of this translation.

KNOLI3H.

French.

affective,

affectant.

affinities.

(biol.) rapports.

(chem.) affinités.

amphibian,

amphibie.

analytic,

décomposant.

arbitrary opinion,

arbitraire.

argument,

raisonnement.

artificial devices,

parties de Vart.

centre of communication.

centre de rapport.

classification.

distribution, classification.

complexity.

composition.

crude,

brut.

crura cerebri.

pyramides du cerveau.

digression,

écart.

ego.

moi.

environment,

circonstances, milieux environnants, etc.

erethism.

éréthisme.

exciting cause,

cause excitatrice.

factor,

cause influente, cause essentielle, etc.

faculty.

faculté.

feeling.

sentiment.

function.

(zool. ) faculté, fonction.

fungus,

champignon.

ganglionic longitudinal cord.

moelle longitudinale noueuse.

hypocephalon,

hypocéphale.

inclination.

penchant.

inference.

conséquence.

inner feeling,

sentiment intérieur.

integral molecule,

molécule intégrante.

intellect,

intelligence.

kinship.

parente'.

laburnum.

cytise.

lacteals,

vaisseaux chyleux.

limb,

membre.

main medullary mass.

masse médullaire principale.

matrix.

gangue, matrice.

XVI

GLOSSARY

medulla oblongata,

mind,

monas,

natural order,

need,

nucleus (of sensations),

orgasm,

peduncles of the cerebellum,

pelvis,

procedure of nature,

propensity,

proteus,

reproduction,

rudiment,

scale of nature,

schematic classification,

sensibility,

sensitive,

serum,

skill,

soft radiarian,

soul,

spinal cord,

spirits,

spontaneous generation,

synthetic,

radiarian,

root-collar,

unguiculate,

ungulate,

vital knot,

vital principle,

volatile,

zoological philosophy,

French.
moelle allongée,
esprit,
monade,
ordre naturel,
besom,
foyer,
orgasme.

jambes du cervelet,
bassiii.

marche de la nature,
penchant,
protée.
génération,
ébauche.

échelle de la nature,
distribution systématique,
sensibilité,
sensible,
sanie.
industrie,
radiaire molasse,
âme.

moelle épinière.
esprits.

génération directe or spontanée,
degré,
composant,
radiaire.

collet de la racine,
onguiculé,
ongulé,
nœud vital,
arche-vitale,
coercible,
philosophie zoologique.

INTRODUCTION.

§ I. Life.

Jean-Baptiste-Pierre-Antoine de Monet de Lamarck
was born on Aug. 1st, 1744, at Bazantin, a village in Picardy,
now known as the Department of the Somme. He was
the eleventh and youngest child of his parents, and belonged
to a family of nobility which had for generations past been
devoted to military pursuits. A number of his brothers
carried on the family tradition by entering the French
army ; but Jean himself was destined by his father for an
ecclesiastical career, and was entered as a student at the
Jesuit College at Amiens. Yet he himself had no inclination
to the calling desired by his father ; and on the death of
the latter in 1760, he made immediate use of his new liberty
to leave the Jesuit College and join the French army, which
was then in Germany, near the end of the Seven Years' War.
He bought a horse and rode through France and part of
Germany, until he reached the French lines on the eve of
the Battle of Fissingshausen. He carried with him a letter
of introduction to the colonel of one of the infantry regiments ;
and on the following morning placed himself in a company
of Grenadiers. The battle of Fissingshausen was fought and
lost : the French retreated : all the officers of Lamarck's
company were killed, and the command fell upon him. His
courage was such that his colonel took him that very evening
to the Field-Marshal, by whom he was appointed an officer .^

^ This at least is the story told by all Lamarck's biographers. I venture nevertheless
to suggest that it can hardly be accepted in the unquestioning way usually followed.
The story is founded upon Cuvier's Eloge de M. de Lamarck, and that again is doubtless

b

yVM

xviii INTRODUCTION

Shortly afterwards Lamarck was promoted to the rank
of lieutenant. Peace being declared, he spent five years in
garrison, first at Toulon, then at Monaco. While at Monaco,
one of his comrades in horseplay lifted him up by the head.
Inflammation of the lymphatic glands of the neck ensued.
He had to abandon his profession, and proceeded to Paris,
where after some delay a complicated operation was per-
formed, which cured him at the expense of deep and per-
manent scars. ^

Lamarck was now thrown upon the world at the age of
22, damaged in health, and with no other resources than a
pension of 400 francs a year. For a year he lived in a garret
in Paris, and earned a living as a clerk in a bank. Then he
entered upon a course of medicine lasting, according to
Bourguin, four years, during part of which time he lived
with his eldest brother in a village near Paris. While in
garrison, Lamarck had already acquired an interest in
botany, and when studying medicine, developed his know-
ledge of it. It was through this means that he came into
contact with Jean-Jacques Rousseau ; and the two
philosophers made botanical excursions together. It was
possibly through Rousseau's influence that Lamarck thought
of devoting himself entirely to music ; but he was dissuaded
by his brother. Botany, however, absorbed him to such
an extent that he abandoned medicine, and entered upon
a course of botanical study lasting ten years, at the end of
which he published his Flore Française, with a preface by
Daubenton.

France was now at the zenith of her philosophic career.
Scientific and philosophic subjects were discussed even in
the world of fashionable society : and the publication of
Lamarck's work, in which also BufTon had assisted, brought

based upon a letter written by Lamarck's son in 1830, shortly after his death, giving
Cuvier certain biographical particulars. This letter was only published in 1909 :
I have read it, and find in it every disposition towards magnifying Lamarck's achieve-
ments and enhancing the family glory. I do not wish to throw doubt on a pleasing
story : I merely wish to indicate that it comes from a distinctly biassed source, and
scarcely justifies the confident relation of it hitherto given by Lamarck's biographers.

' This is Cuvier's account, which differs somewhat from that of Lamarck's son.

LIFE xix

him into immediate fame. In 1779 he was elected into the
Academy of Sciences over the head of Descemet.

Two years later Buifon obtained for Lamarck a commis-
sion from the king to visit a number of foreign botanical
gardens and museums. In company with Buffon's son he
travelled through Germany, Hungary and Holland, collecting
rare plants, meeting eminent foreign botanists, and making
notes for the use of the Jardin du Roi at Paris. On his
return in 1782, when he was 38, he still had no salaried
position, but was shortly afterwards appointed keeper of
the Herbarium at the Jardin du Roi, with the wretched
salary of 1000 francs a year. But even this position was
very insecure, and in 1790 its suppression was recommended
by the Comité des Finances to the Assemblée Nationale.
Lamarck published two pamphlets to emphasise the necessity
for continuing the office ; to state his own claims for being
restored to it ; and to submit to the Assemblée a general
scheme for the reorganisation of the Jardin du Roi, by which
it should become of general use to science, the arts and
commerce.

For another two or three years he appears to have held
some botanical position in the Jardin du Roi, or, as it became
about this time, the Jardin des Plantes. But at last, in 1793,
the scheme of reorganisation was carried by the National
Convention, and the Muséum d'Histoire Naturelle was founded.

There is not much clue to Lamarck's views on the Revolu-
tion, although it is stated by de Mortillet that the change
of name of the Jardin du Roi was at the instigation of
Lamarck. There is no doubt, moreover, that Lamarck's
scheme of reorganisation, written in 1790, was to a great
extent embodied in the scheme actually voted by the Con-
vention three years later : under which the Muséum
d'Histoire Naturelle received the constitution which it
still possesses at the present day. Two chairs of zoology
were created : one of which was devoted to mammals, birds,
reptiles and fishes, while the other was devoted to the
*' inferior animals " (the insects and worms of Linnaeus),

XX INTRODUCTION

or, as Michelet called it, " Vinconnu.^^ To the first chair,
Geoffroy Saint-Hilaire was appointed, then a young man of
22. For the second chair, containing the unknown part of
the Animal Kingdom, there were no obviously suitable
candidates. Lamarck was a botanist of 25 years standing,
but the chair of botany had passed to Desfontaine, and
there now seemed nothing suitable remaining for him except
this chair of zoological remnants, to which accordingly he
was appointed at a salary of 2868 livres, 6 sous, 8 deniers.
The record of persons attached to the Museum d'Histoire
Naturelle in 1794 contains the title of his chair : " Lamarck
— fifty years old ; married for the second time ; wife
enceinte ; six children ; professor of zoology, insects, worms
and microscopic animals." ^ Nevertheless, Lamarck passed
the remainder of his life in straitened circumstances : he
married altogether four times, and had seven children.

The collection of invertebrate animals already accumulated
at the Museum was immense, and Lamarck soon found that
his share of the Animal Kingdom included by far the greater
number of all existing species. His knowledge of zoology
was limited to the sphere of conchology, where he had
acquired some information, partly through intercourse with
his friend Bruguiere, and partly through a collection of
shells that he had formed for himself. From the date of
his appointment, however, he practically abandoned botany,
and threw himself fervently into the study of invertebrate
zoology. The results of his researches were published in
seven volumes in his great work Histoire Naturelle des
Animaux sans vertèbres, 1815-1822. Lamarck's other works
included a number of publications on meteorology, a subject
in which he had taken an interest from early days, when
from his garret window at the top of a high house in Paris,
he could see nothing but the clouds passing by, and lay
speculating on their varied shapes and movements. But,
like Goethe with his Farbenlehre, Lamarck failed on this
subject either to reach any important conclusion or to secure

' Lamarck, by A. S. Packard, New York, 1901.

LIFE xxi

the approval of his contemporaries. He attacked the
chemistry of Lavoisier and Berthollet, which further com-
pleted the discredit in which his excursions outside biology-
involved him. His only remaining great work is the
Philosophie Zoologique, published in 1809, the translation of
which is herewith presented to the public, and to which I
shall confine the remaining sections of my Introduction.
Lamarck died at the end of 1829, at the age of 85. The
end of his life was passed in melancholy circimastances.
During his last ten years, he became totally blind ; this was
due, it was said, to constant strain of eyesight in microscopic
work. But he was faithfully attended by his two daughters,
to one of whom he dictated the final portion of the Animaux
sans vertèbres. The scientific world of his time rejected his
theories of transformism ; Cuvier, who was firmly convinced
of the fixity of species, became the most famous and fashion-
able biologist of the time, and Lamarck's influence was
completely overshadowed. Arago, in his Histoire de ma
Jeunesse, relates the story of his meeting with Napoleon.
The Emperor was receiving the Members of the Institute
at the Tuileries, and Lamarck attended, carrying with him
his latest work, which happened to be the Philosophie
Zoologique, to present to Napoleon. Napoleon first spoke to
Arago, who had just been elected to the Institute, and then
passed to Lamarck. " Napoleon," says Arago, " passed
from me to another member of the Institute : a naturalist
famous for his brilliant and important discoveries, M.
Lamarck. The old man presented Napoleon with a book.
' What is this ? ' said the Emperor. ' Is it your absurd
Météorologie with which you are disgracing your old age ?
Write on natural history, and I will receive your works with
pleasure. This volume I only accept out of consideration
for your grey hair. Here ! ' " and he handed the book to
an aide-de-camp. Lamarck, who had been vainly endeavour-
ing to explain that it was a work on natural history, was
weak enough to burst into tears.^

^ Lamarck, par G. Revault D'Allonnes, Paris.

xxii INTRODUCTION

Od his death, no permanent grave was provided for him.
His remains were carried to the cemetery of Montparnasse ;
but for some reason no burial lot was obtained. His body
was placed in a trench, cleared out once every five years
for the reception of new bodies. No monument marked the
site : but an unknown hand wrote on the margin of the
register : "To the left of M. Dassas." The position of the
trench is thus known, but Lamarck's bones have probably
long since been removed, and their identity irretrievably
lost among vast quantities of others thrown together in
the Catacombs of Paris.

§ 2. The Philosophie Zoologique.

Few names have been so extensively quoted in modern
biological controversies as that of Lamarck ; yet of those
who quote him scarcely any have taken the trouble to read
his work. His name has come to be associated almost
exclusively with the doctrine of the inheritance of acquired
characters : the modern upholders of that doctrine are
commonly referred to as neo-Lamarckians, and among those
there are some who look up to Lamarck as the greatest
biological teacher that has ever lived. Partly on these
grounds, and partly on the grounds of the great historical
interest attaching to the work, it has been held desirable to
publish a complete English translation of his famous
philosophical treatise. For it is to be observed that the
Zoological Philosophy, from the purely historical stand-
point, represents the most advanced philosophical position
taken up by men of science in the pre-Darwinian era. We
most of us in these days do not believe in the inheritance of
acquired characters ; but we all of us believe in evolution.
The Zoological Philosophy was published exactly half a
century before the Origin of Species : and by far its most
outstanding feature is its defence of the theory of the muta-
bility of species against the theory of special creations for
each species, then almost universally current. That inherit-

PHILOSOPHIE ZOOLOGIQUE xxiii

ance of acquired characters was one of the main factors
supposed by Lamarck to account for that evolution, I do
not wish to deny ; but that the reputation of Lamarck is to
stand or fall by that one theory is a suggestion which can
scarcely be made by anyone who closely studies the present
translation. But to that I shall come shortly.

Before beginning the translation, I had to consider on
what principles I should carry it out. The style of writing
and the mode of thinking that prevailed a century ago are
radically different from those that prevail at the present day.
As regards the style, Lamarck is lucid but ponderous. His
sentences are of great length, carrying numbers of sub-
ordinate clauses : his language is precise and carefully in
accordance with logical forms. All this is novel and more
or less disagreeable to modern readers. The formality of his
language soon becomes tedious ; we get lost in the relentless
prohxity of his sentences ; we do not care a snap for logical
forms. One further characteristic of Lamarck's style — and
this one unquestionably a vice — is that of redundancy.
Many favourite doctrines are repeated with such insistence,
and in so many different forms, that the student finds the
most abundant justification for frequent skipping.

The mode of thought is not less contrasted with modern
modes, than is the style of writing. Every sort of scientific
or literary production is a product of its age, almost as much
as of the individual who attaches his name to them. In
the literature of any period there are current a certain
number of more or less established ideas. Those ideas
circulate through society, undergoing changes but slowly.
Each new book that is issued represents certain of those
ideas in a setting that is perhaps more or less new ; and if
it is an original work, of somewhat rare order, it may even
contain one or two ideas not previously current in society.
And these ideas, not being previously current, are not
understood ; if they advance at all, they can only do so
slowly.

Hence the difficulty with which we are confronted on

xxiv INTRODUCTION

plunging into a scientific work of more than a century
ago. We are suddenly in an entirely new milieu ; for
in science, above all things, the rapidity of advance has
been immense. We find ourselves in the presence not merely
of one or two ideas that are new and therefore difficult to
us ; but we are surrounded on all sides by strange and
unfamiliar conceptions, embodied in a language that is
modelled on a scheme we have never heard of. And the
associations which we carry with us from our own age are
often misleading. The difficulty is comparable to that of
learning the elements of a new science or of a new language.
Here then are very substantial and solid reasons to account
for the undoubted fact that Lamarck, although extensively
referred to, is scarcely ever read at the present day. And
these reasons had to be carefully considered in deciding upon
the mode in which the work was to be presented to the
English-reading public. Yet I could not disguise from myself
the fact that the main interest of this translation is historical,
and that any tampering with the text, in the hope of making
it more intelligible, would gravely damage its value from
the historical standpoint. I therefore determined to carry
out what should be in the main an extremely literal trans-
lation, and to leave its natural asperities of thought and
style without softening. On the other hand, I determined
to write by way of introduction a brief précis of the whole
work, stating as far as possible the sum of Lamarck's doc-
trines in my own words for the use of persons accustomed
to the style of writing and to the mode of thought prevalent
in this twentieth century.

I have said that the translation is extremely literal ; yet
it is not absolutely so, I have not hesitated, especially in
the earlier part of the work, to break up some of the longer
sentences, in accordance with modern taste. I have even
translated such a word as " generation " by " reproduc-
tion," in all cases where Lamarck meant by the former word
exactly what we mean by the latter. I am aware of course
that the connotations of these two words are not precisely

PHILOSOPHIE ZOOLOOIQUE xxv

the same, and indeed that the more modern word superseded
the older, in correspondence with the growth of a more
correct theory of the process indicated. But as a general
rule, Lamarck does not intend the word " génération " to
imply any theory excluded by the word " reproduction " :
to translate it by " generation " would at the present day
carry suggestions which are irrelevant to his issue, and be
more confusing than the name which has now become
familiar. But of course where he does intend it to carry a
connotation, not borne by the word " reproduction," I have
translated it accordingly.

Other difficulties arise from the need for expressing the
forgotten concepts of a century ago in a language adapted
for the conveyance of the concepts of to-day. Lamarck's
concept embodied in the French word distribution long ago
became extinct ; the word itself has since come to be utilised
for a wholly different purpose, with geographical connota-
tions : its extinct meaning has now to be expressed by a
periphrasis or some other single word, intrinsically less suit-
able, but more comprehensible. In other cases, a certain
alliteration in the original has to be sacrificed for the sake
of clearness. It would be impossible to translate " parties
de l'art " as " parts of the art " ; for few biologists would
guess what the part of an art might be.

The Zoological Philosophy is divided into three parts, the
first of which is devoted to zoology, the second to physiology,
and the third to psychology, using these three terms in their
modern sense. I shall now proceed without further pre-
liminaries to a description of Lamarck's doctrines on these
subjects.

§ 3. Zoology.

The first doctrine set forth by Lamarck is that animals
in nature are arranged in a " natural order," to discover
which is the duty of the systematic zoologist. Lamarck
held that if all living species of animals were known, they
would be found to fall into a linear series, exhibiting a few

xxvi INTRODUCTION

small collateral branches : a characteristic of this series
would be that each species would differ from the neighbouring
species by gradations so small as to be imperceptible. From
species to species, however, organisation gradually develops,
so that there are conspicuous differences discernible when
we compare two animals situated at some little distance
from one another in the scale of nature. The scale begins
with Monas and ends with Man : these two infinitely different
creatures being connected by the entire series of animal
species, each one differing from its neighbours only in minute
details. Lamarck attributed the large gaps which appear
in various parts of the scale to undiscovered species ; for,
as we shall shortly see, he did not believe that species had
ever become extinct. Between the various orders of birds
or mammals, for instance, there often seems no obvious
connecting link : and the gap between these two classes
themselves is a wide and apparently impassible one. The
discovery at the end of the eighteenth century of Ornitho-
rhyncus and Echidna, which possess many of the characters
both of mammals and birds, naturally appeared to Lamarck
strong confirmation of his theory that the gaps existing in
the linear series of animals, merely represent the existence
of living species, hitherto undiscovered, either because
they belong to unexplored lands or to the bottom of the
ocean. Lamarck's scale of nature was thus to a certain
extent analogous with the modern periodic classification of
the elements. In each case, gaps occur which are liable,
as knowledge advances, to be filled up by new species or
new elements, possessing properties that can be prophesied
in advance.

If there is in reality no hiatus or gap in the progressive
linear series of animals, then, argued Lamarck, there cannot
be any isolated groups of animals, nor is there any objective
justification for breaking up the animal kingdom into classes,
orders, families, genera, etc. In fact, all such classifications
must be purely arbitrary. They may indeed set forth any
portion of the animal series, arranging the species in their

ZOOLOGY xxvii

true order ; and in so far as they do this, they are valid and
useful. But the hues of demarcation between these groups
are regarded by Lamarck as wholly arbitrary. You may,
for instance, take the first hundred species of the scale and
call it Class L : the second hundred species you may call
Class n. : but you would have been equally justified in
taking the first 120 species and calling them Class L, and
the second 120 Class IL In short, there is no real division
or break in the scale of animal nature.

Hence, Lamarck refers to classes, orders, families, genera
as " parties de l'art," or devices introduced by art for human
convenience, and not corresponding to anything real in
nature. Yet he regarded these devices as absolutely essential
for introducing order into what would otherwise be a chaotic
jumble. We are thus forced to adopt either a schematic
classification or a " natural " classification : the former is
a mere grouping of animals by respect to certain characters
of no fundamental taxonomic importance ; the latter repre-
sents the series of species in their true order, and is only
artificial, says Lamarck, in so far as it breaks them into
groups. Since such subdivision of the series is a practical
necessity, he held that it is wise to apportion our classes,
orders, etc., in such a way that the gaps in our knowledge
fall between them, and do in fact create apparent groupings
in the animal world.

Lamarck then proceeds to trace the essentials of a natural
classification, which shall be in correspondence with the
order of nature. The guiding principle must be the true
alB&nities (rapports) between animals. Their contiguity in
the series is to be determined, mainly by the resemblance
existing between their most " essential " organs, and to a
lesser degree by the resemblance between less " essential '*
systems of organs. By " essential " Lamarck means, in the
case of animals, essential to the maintenance of individual
life, and in the case of plants essential to reproduction.
He says that the most essential system, in the determination
of affinities, is the " organ of feeling," or nervous system ;

xxviii INTRODUCTION

after that comes the respiratory system ; and third, the
circulatory system. This order of importance is arrived at
in the following way. Starting from the higher extremity
of the animal series, where man is placed, he descends the
series of gradually simplifying animals. One after another,
he finds the different systems of organs dying out : and the
importance of each system is judged by the distance he has
to travel down the series before that system becomes extinct.
Thus the circulatory system extends throughout Lamarck's
eight highest classes, viz. : — mammals, birds, reptiles, fishes,
molluscs, cirrhipedes, annelids and crustaceans, and there
ends. The respiratory and nervous systems extend through
these and also the two succeeding classes of arachnids and
insects. They are therefore held to be more essential than
the circulatory system. Of these two again, the nervous
system is the more essential, since " it has produced the most
exalted of animal faculties, and is necessary to muscular
activity." I confess it is not obvious why the alimentary
system does not take precedence of all others, for it is
described as extending through the three further classes
of worms, radiarians and polyps, only ending at the in-
fusorians. Since Lamarck (as I shall shortly explain)
believed in an evolution from the simplest to the most com-
plex animals, he naturally assumed that the earliest system
of organs to be developed in the course of that evolution
must be the system most essential to life in the higher animals.
The least essential of the features to be considered in the
determination of affinities are, in his opinion, the external
characters of animals : differences of external characters
are therefore to be used only for the determination of species.
For more fundamental distinctions, more essential characters
are to be considered.

Lamarck found the " productions of nature " commonly
divided into the three kingdoms of animal, vegetable and
mineral. He proposed the abolition of this scheme, and the
substitution of another in which all bodies were to be divided
into organic and inorganic. For the science which deals

ZOOLOGY xxix

with organic bodies, both Lamarck and Treviranus proposed
the name " biology " in the year 1802. Lamarck further
commits himself to the statement that all inorganic sub-
stances are derived from the exuviae of living bodies. He
believed that nature originally created only the most
elementary forms of life. These by evolution upwards led
to the animal and plant kingdoms : the decomposition of
these two types of organism gave rise to the third kingdom,
chiefly composed of minerals.

He then has to define the difference between animals and
plants : he finds that irritability, or the power of response to
external stimuli, is a universal property of animals, and a
property which is invariably lacking in plants. Mimosa
pudica, the sensitive plant, gives him a certain amount of
trouble, but the apparent exception is explained by an
ingenious though (even for his time) highly speculative
theory. True irritability, characterised by an immediate
€ontraction on contact with a foreign body, is a property
which according to Lamarck is found in some part of every
living animal. In the second line of differentiation, he
names digestion and the power of locomotion as being charac-
teristic of the great majority of animals and wholly absent
in plants.

Lamarck sees a new instance of the wisdom of the " sub-
lime author of all things " in the arrangements made for
preventing overpopulation of the earth by any one species.
Small animals, though multiplying with great rapidity, are
kept down by an immense mortality, in which they are
involved by the accidents of life, more especially the acci-
dent of being eaten by a larger animal. The larger animals,
which are not liable to serve as food for others, are main-
tained within their proper limits by a low rate of reproduc-
tion. Man alone might well multiply to cover the surface
of the earth : but he is himself his own executioner ; for
with the development of intellect comes the development of
passions, which ever lead to the reduction and limitation of
his own species.

XXX INTRODUCTION

§ 4. Evolution.

The most fundamental purpose of Lamarck's zoological
work was to controvert the belief in fixity of species. It
was at that time almost universally held that all species
had been created at the beginning of the universe by special
acts of creation. They were thus supposed to be all of
equal antiquity, and to be " as old as Nature." They were
supposed further to have subsisted without any sort of
structural change since the moment of their creation.

These propositions Lamarck attacks. He holds that
species can only maintain their constancy of form so long
as their environment remains constant. Any change in the
environment necessitates a corresponding change in the
species. In support of this doctrine, he cites the case of
domesticated animals, and the altered shape which has in
their case followed upon an altered environment : the same
thing is found in cultivated plants. He draws attention
further to the linear series of animals arranged in order of
gradually-increasing complexity, so as to form a continuous
whole, strongly suggesting development. He is far from
wishing to attack the conceptions of theology. If " the
sublime author of the universe " can create all the different
species by separate acts of creation, so too, says Lamarck,
he can surely create one or two species to begin with, and
confer upon them the power of evolving into the rest.

Lamarck held that as long as the environment remained
unaltered, the species living in it might also remain unaltered.
Geoffroy Saint-Hilaire had recently brought from Egypt an
extensive collection of mummified animals of great antiquity .
An examination of these animals revealed the fact that they
were in every respect identical with the existing fauna of
that country ; and this discovery was used as an argument
in favour of the permanent fixity of species. Lamarck's
position, however, was unaffected by it : for he pointed out
that there was every reason to believe that there had been
no change in the climate and conditions prevaihng in Egypt

EVOLUTION xxxi

during the last few thousand years : hence no change need
have been expected in the animals living there.

Lamarck then considers the question whether it is true
that any species have ever become extinct. The evidence
of fossils certainly seems to suggest it, for they exhibit
innumerable forms no longer found among living animals.
Yet Lamarck finds it very difficult to believe that nature
could be so imperfect as to permit of the complete extinction
of any species. He was not wholly emancipated from that
vicious tendency — of which Plato was the prototype — towards
imagining, that because a thing was not beautiful, or har-
monious, or otherwise agreeable, it could not be true. Hence
he inferred that, in the case of many fossils of apparently
extinct species, the species would still be found living in
unexplored countries, or on the sea-bottom, or other unknown
regions. He believed furthermore that many of these fossils
had evolved into existing known species ; but that the
changes undergone during evolution, in correspondence with
a changing environment, had been so great that the existing
species were no longer recognisable as descendants of the
fossils.

If any species have become extinct it is, he said, at all
events only the larger species of land animals, such as
Cuvier's Palaeotherium, Anoplotherium, Mastodon, etc. : and
their extermination, if a fact, is exclusively due to human
agency. But no species of water animals, nor any of the
smaller species of land animals, can possibly have become
extinct. Lamarck very shrewdly perceived that the fossils
showing most analogy with living forms are usually the
least ancient. And this strange admixture of good and
bad philosophy then ends in an attack upon the theory of
a general catastrophe in nature — a theory invoked to explain
among other things the divergence of fossils from existing
forms of life. Throughout this part of Lamarck's work, we
find much in which his philosophy was several generations
in advance of his contemporaries, and indeed was not far
short of our own : mixed with much else in which his

xxxii INTRODUCTION

philosophy was far behind that taught by many of his greater
contemporaries and forerunners.

The method by which Lamarck beheved evolution to have
been brought about was by the inheritance of minute
variations : and he was altogether opposed to any belief in
those larger variations which we now call mutations. " If
the procedure of nature is attentively examined," he writes,
" it will be seen that in creating or giving existence to her
productions, she has never acted suddenly or by a single
leap, but has always worked by degrees towards a gradual
and imperceptible development." For the explanation of
this belief we have to remember that the current notions of
his time were of the catastrophic type. Species were sup-
posed to have been individually created by single and
instantaneous acts : the surface of the earth was likewise
regarded as having been exposed to a series of violent
catastrophes, so that the changes which have visibly enough
come over it were due, not to slow and gradual processes,
but to a succession of sudden large breaks.

Now those who upheld the standard of uniformitarianism
were inclined to state their position in the most uncom-
promising way. They adduced such maxims as " Natura
non facit saltum," and endeavoured to show that evolution
proceeded invariably by minute and imperceptible gradations.
It is possible that they went too far : nevertheless, we have
to remember that they never envisaged the modern problem
of the mutation theory. For them the antithesis was
between catastrophic transformations and transformations
by imperceptible gradations. Even should the doctrine
of Bateson and De Vries be well founded, the evolutionists
of a century ago must be held as its ancestors in a direct
line.

In the same way that uniformitarianism, though a true
principle, was not propounded in precisely correct terms, so
also transformism tended to be asserted in somewhat too
extreme a fashion. By reaction against the doctrine that
species were immutable, the evolutionists of the time under

EVOLUTION xxxiii

consideration believed in a greater mutability than has been
found to be the case. Lamarck believed that an alteration
of the environment would within a few generations effect a
permanent alteration in the structure of a species. Of
this I shall adduce a number of instances in the following
section. He perceived how easily domestic races evolved
out of wild species ; but he apparently did not know how
easily they also lapsed into the wild state ; nor that varia-
tions, so conspicuous to the eye, are highly unstable and
superficial. By reaction against the doctrine of the per-
manent stability of species, he adopted an altogether exag-
gerated view of their instability. Indeed, his views on this
subject are scarcely consistent : and Sir Ray Lankester
has already urged that his first and second laws are
incompatible.

Given the fact of evolution, the question at once arose as
to what are the physical causes of it. Of natural selection
Lamarck had not the slightest conception. The only passage
that is even remotely suggestive of it, is when he deplores
the inequality of intellectual capacity among men ; for
those with higher intellects gain an advantage over the
others, and hence these others, constituting the great
majority, must suffer. He regarded the equalisation of
intellectual capacity as the greatest social reform required.
It is plain how little he guessed at the theory of natural
selection.

He held that evolution was due to the co-operation of
two factors. The first and most fundamental was due to
an innate tendency to evolve towards increasing complexity
of structure : this tendency being conferred upon the low-
liest animals at the moment of their spontaneous generation.
I shall describe Lamarck's opinion as to the physical causes
of the tendency, as also of spontaneous generation itself, in
a later section deaHng with his physiology. For the present,
it suffices to observe that Lamarck beheved that various
portions of inorganic matter are constantly being vitalised
or endowed with life by a process of spontaneous generation,

f

xxxiv INTRODUCTION

that in this way worms and infusorians come into being,
and that these organisms are at the same moment endowed
with a tendency to evolve, till they ultimately give rise to
all the higher races of animals.

The second factor, which, according to Lamarck, operated
in the evolution of species, is that with which his name has
come to be so closely associated, namely, the inheritance of
acquired characters. This doctrine appears to have been
first enunciated in detail by Lamarck himself : it is natural
therefore, that he should dwell upon it at great length in
the present work. We must, however, recollect that he
looked upon it as subordinate to the main factor, just as
Darwin invoked it as subordinate to natural selection.i
His position was far indeed from that occupied, for instance,
by Herbert Spencer in 1852, when some evolutionists en-
deavoured to account for evolution with exclusive reference
to direct action of the environment. I shall deal with this
alleged factor in my next section : for the present I confine
myself to an account of Lamarck's views of the evolutionary
process.

Lamarck held, then, that if it were not for the effects of
environmental influences, the innate tendency to develop
would be the exclusive factor in operation. We should
then see the linear series of animals to be a perfectly regular
and even progress in complexity of organisation from Monas
termo to man. Each animal born would presumably be
slightly more complex than its parent. If we could trace
the ancestry of man, we should find as we went backwards
that each individual was to an excessively small degree less
complex than its immediate neighbour, till finally we ended
with the infusorians. All existing animals are on the road
of development from Monas to man, and man's ancestors
include every existing species of animal. Not only had he
bird, reptile and fish ancestors, but also arachnid, insect,

^ Professor Charles Martins in his introduction to the 1873 reprint of the Philosophie
Zoologique is so intent upon making out a ease for inheritance of acquired characters,
that he omits to make any mention whatever of Lamarck's primary factor. He has
thus helped to perpetuate a common error regarding Lamarck's views.

EVOLUTION XXXV

worm, starfish, etc., ancestors. ^ He passed through the
stage of being a scorpion and a spider. He traversed in
turn every known species of insect. He was a tapeworm,
a sea-anemone, a polyp and an amoeba. For myself, I fail
to see how he could have been an intestinal worm when
there were no such things as intestines, or a liver-fluke
when there were no such things as livers. His existence as
a flea must have been precarious, when there was nothing
more substantial to live upon than jelly-fishes, starfishes,
and parasitic worms. Indeed, the doctrine is wholly absurd
the moment it is consistently thought out. It was to remedy
absurdities of a somewhat different kind that Lamarck in-
vented his factor of use-inheritance : and it is that factor
which he would have at once invoked to explain away such
difficulties as I have named.

The fact remains however that, leaving aside for the
moment the influence of environment, Lamarck assumed a
perfectly even development to proceed in a straight line
throughout the animal scale : and he assumed that this
development was due to an innate power conferred upon the
lowest of animals at the moment of their spontaneous genera-
tion. Accordingly, one of the longest chapters in the whole
work is devoted to an account of the gradual progress in
organisation observed as we pass along the animal scale.
In point of fact, Lamarck inverts the natural order, and
begins with the highest mammals, proceeding to the lowest
infusorians. Thus, instead of a gradually increasing com-
plexity, he finds a gradually diminishing complexity, as he
passes along, or as he calls it a " degradation of organisation."
That Lamarck should have traversed the series in the wrong
direction is doubtless due to the fact, that from the time
of Aristotle to the time of Lamarck, every systematist,
including even Linnaeus, had commenced his classification
with the highest animals and finished it with the lowest.

^ I am here alluding to the classification presented in the main work. This classifica-
tion was greatly improved in the " Additions " to Part I., as I shall show later ; and
many of these animals were then referred by Lamarck to collateral branches, off the
main line of development leading to man.

xxxvi INTRODUCTION

Lamarck was merely following a precedent, of which he
fully realised the inappropriateness. In his own classi-
fication, he strikes out a new line, and begins his animal
scale with the simplest existing animals.

The degradation noted by Lamarck as he passed along the
scale from mammals to infusorians is traced throughout the
various systems of organs. The skeleton is lost, on passing
the fishes ; the nervous system, on passing the insects ;
respiration comes to an end with the radiarians, and so on
with the circulatory, digestive and other systems. So, too,
the lungs of mammals gradually deteriorate through the birds
to the reptiles and fishes, where they are replaced by " less
perfect " respiratory organs, in the shape of gills. These
again vanish farther on, and give place to the still more
imperfect system of tracheae in the insects and arachnids :
while lower down the scale, respiration is entirely lost.

The bilateral symmetry which characterises all animals
down to the insects similarly gives way to a radiating shape
in Lamarck's class of " radiarians," and these merge into
amorphous infusoria. Polyps represent the intermediate
state : for they have radiating tentacles around the mouth,
but are not otherwise of definite shape. Nature has, accord-
ing to Lamarck, just started in them that radiating form,
which is carried to its highest perfection in the echinoderms.

A few observations on special points may be made before
I pass on to the subject of use-inheritance. Lamarck, as
we shall see in dealing with his physiology, assumed the
existence of " subtle, invisible fluids," which like spirits in
the past, and like vital forces or bio tic energy in the present,
served to explain anything which remained a mystery before
materialistic methods. They were useful for instance for
explaining the physical origin of the radiating form of cer-
tain animals. " The subtle surrounding fluids which enter
the alimentary canal are expansive, and must by incessant
repulsion from the centre towards every point of the circum-
ference give rise to this radiating arrangement of the parts."

In much the same way he explains why birds have feathers

EVOLUTION xxxvii

instead of hair. When a bird flies, it fills its lungs with air
" in order to increase their volume and make itself lighter."
But the lung being warm causes the air to expand, and
piercing through the lung, penetrate every region of the
body, including the bones and hair. The result of the
expansion of air within the bird's hair is to make it blossom
forth into feathers. Lamarck did not fail to see the diffi-
culties of his theory. Why have bats not got feathers ?
Because they have a complete diaphragm, which prevents
the swelling and piercing of the lungs. Why then have
flying insects not got feathers ? Each difficulty is met by
Lamarck with unshaken confidence in his hypothesis.

Lamarck did not believe in spontaneous generation,
except in the most elementary animals, but he held that
among them it is always in progress. Like much else in
his work, this is a deduction based on false premises. All
infusorians, he says, die in cold weather : they are much
too delicate either to survive or to leave any spores or ger-
minal material that could last through a winter. Yet, on
the return of warm weather, we find them swarming in
stagnant water and other places : hence they are spon-
taneously generated.

The progress made towards " perfection " of organisa-
tion as we advance along the animal scale must be
understood to mean a progress in the direction of human
organisation. For Lamarck the organisation of man is the
type of perfection ; and perfection or imperfection of
organisation is judged by its approach towards or depar-
ture from the human. Lamarck recognised, however, that
a high organisation was characterised by the concentra-
tion of organs and functions in special places, whereas in a
lower organisation they tend to be more generalised through-
out the body. He thus anticipated von Baer's famous law,
that development proceeds from the homogeneous to the
heterogeneous, upon which was founded one of the most
important clauses in Spencer's formula of evolution.

It must have been quite obvious from the first that the

xxxviii INTRODUCTION

kind of evolution above described could not possibly account
for all the varied shapes of existing animals. The series is
full of anomalies. Birds, for instance, are lower in the
scale than mammals. Yet their pectoral muscles and
sternum are developed out of all proportion to their proper
place in the series. Then, again, whales have no legs ; yet
legs reappear farther down the series, for birds have them,
and so do many reptiles, not to speak of lower animals.
If evolution was solely as hitherto described, we should
expect legs to vanish gradually as we passed down the
scale ; and having vanished, not to reappear again.

Within a single class, such as reptiles, the same anomaly
is seen. Frogs (for Lamarck included amphibians with
reptiles) breathe by gills when first born : hence they are
inferior to snakes which never have anything but lungs.
Yet snakes have no legs, while frogs have legs : that is to
say, the lower animal is better oif for legs than the higher.
Whence these numerous anomalies ? It is to Lamarck's
solution of this problem that we must now turn our attention.

§ 5. Inheritance of Acquired Characters.

Acquired modifications, as distinct from the so-called
spontaneous variations, are of two different kinds. In the
first place, there are those modifications which are due to
the direct action of the environment, without reference to
any active efforts on the part of the organism. Such, for
instance, are various modifications in colour, etc., of the
superficial layer of the body, due to the application of light
or heat : such, again, are mutilations. In the second place,
there are those modifications which arise from the greater
or lesser use of any part, due to some environmental cause,
which requires the organism to exert certain parts to a
greater or lesser extent than the average. This latter type is
referred to as functionally-produced modifications, and their
inheritance is often called use-inheritance. It is this latter
type alone that Lamarck regarded as being a factor in

ACQUIRED CHARACTERS xxxix

organic evolution ; he expressly excludes direct action as
an operative cause. But before dealing with Lamarck's
general views on this subject, I propose to cite a number of
the facts upon which he relied for the proof of his theory.

Domestic races, both of animals and plants, are very
different from the ancestral wild races from which they spring.
When the environment is greatly altered, the structure of
the organism undergoes a corresponding alteration. Take,
for instance, the various races of dogs. They are, according
to Lamarck, all descended from an animal something like a
wolf. They became domesticated by man, and were trans-
ported by him to different parts of the earth, where the
environment was very different from their natural home.
Accordingly, they underwent modifications in each locality,
which brought them into harmony with the conditions pre-
vailing in that locality. These modifications, being inherited
through many generations, acquired comparative stability ;
and the new varieties, when imported into a new country
or great city, would for a long period retain their general
characteristics. These would be further complicated by
inter-breeding, and thus give rise to the many different
varieties with which we are acquainted. So argued Lamarck.

Where an animal does not use its teeth, these dwindle
and disappear. Such, for instance, is the case with right-
whales and ant-eaters, although Geoffroy Saint-Hilaire dis-
covered rudimentary teeth in the foetus of right-whales.
The same applies to birds, where teeth have become still
more completely extinct.

Animals which do not use their eyes, such as moles, after
a time lose the use of that organ either completely or
partially.

Snakes would be impeded by legs, and have consequently
lost them. Their mode of life requires them to hide in
grass, and to pass through narrow crevices. Hence, urges
Lamarck, their bodies become narrow and long. Long legs
would greatly interfere with their mode of life : short legs
would be incapable of supporting them, since (being reptiles)

xl INTRODUCTION

they could not have more than four. Similarly, insects
which do not fly have undergone a degeneration of the
wings.

Birds, to continue Lamarck's examples, acquire webbed
feet by constant efforts to swim. In the course of these
efforts, the skin uniting the base of the digits is constantly
on the stretch. It therefore develops, and, in course of
many generations, birds are produced with complete webs.

Other birds perch on trees, and by continual effort to
grasp the branches, develop long hooked claws. Others,
again, feed on water-animals or plants, but have a strong
objection to wetting their bodies. Hence they are constantly
stretching their legs, to keep their bodies above water when
standing in it. After many generations, long legs become
established, without feathers and adapted for standing in
water. For the same reason long necks were developed by
constant stretching. In the case of birds like swans, which
have no objection to swimming on the water, long necks
are estabhshed without long legs.

Where the tongue is much used for reaching objects in
front, it also lengthens, as in the ant-eater or woodpecker :
where it has to grasp or palpate such objects, it becomes
cleft, as in humming-birds, lizards, and snakes.

Flat fishes normally swim in the vertical plane, with one
eye on each side of their heads. In certain species, however,
the fish desires to come as near as possible to the shore ;
and in the case of a shelving beach, it can approach much
nearer land by turning on to its side and swimming in the
horizontal plane. One eye, being then on the under-surface,
where there is really nothing worth looking at, is perpetually
being strained or twisted, round to see what is going on
overhead. Hence, after many generations, it moves bodily
round to the upper side, as in soles, turbots and dabs.

Herbivores are commonly massive because they spend
all their time eating : some, however, such as gazelles, are
liable to be pursued by carnivores, and hence acquire legs
capable of rapid locomotion ; others, such as deer, develop

ACQUIRED CHARACTERS xli

in a similar manner, owing to pursuit by man. All these
creatures are liable to fits of anger, in which they desire to
fight ; but, since neither their legs nor their mouths are
suitable for use as weapons, they are reduced to butting
each other with the crowns of their heads. This causes an
additional flow of fluids to that region, with a deposit of
horny matter : hence the development of horns and antlers.

Giraffes live in barren countries, where the only available
food is in the leaves of trees. By constantly stretching
their necks to reach these leaves, they acquire the strange
conformation characteristic of them. Kangaroos likewise
acquire a powerful pair of hind-legs and tail.

The sloth is drawn upon likewise for an explanation of
its slovenly habits. Originally a dweller on the ground,
and then capable of moving with the ordinary rapidity,
it took to climbing trees, where food was found in such
abundance as to require very little movement. More move-
ment than necessary would be injurious, partly owing to
the heat of the climate in which it lives, and partly because
by sitting still and doing nothing it would run fewer risks
of falling off and hurting itself. By constant disuse of its
locomotive structures, continues Lamarck, it gradually lost
the power of moving on the ground, where it is said to be
able to take not more than fifty steps in a day.

Lamarck even adduces an instance from man himself.
One, Tenon, had recently stated that the intestine of habitual
drunkards is greatly shortened. Now habitual drunkards
(he continues) consume a smaller quantity of solid food than
ordinary people : there would be less work for their intestine
to do, and a corresponding diminution in its length. Such
are the facts on w^hich Lamarck bases his theory of the
inheritance of functionally-produced modifications.

Now it is quite clear that all these facts can be explained
as easily or more easily on the theory of natural selection,
than on that of the inheritance of acquired characters. If
it is true that rapid moving among trees is dangerous to
sloths, then natural selection would soon ordain that all

xlii INTRODUCTION

sloths should become inactive. Rash sloths, which moved
about rapidly and hence fell to the ground, would be injured
and more or less incapacitated for reproduction. They
therefore leave no progeny of rash sloths, similar to them-
selves. Cautious sloths, on the other hand, which move
as little as possible, run fewer risks of falling off and getting
hurt ; they are therefore likely to leave progeny, and this
progeny will consist of cautious sloths like their parents.
Thus there is a perpetual tendency for the species to be
recruited from the cautious and prudent sloths, and for the
extinction of the rash sloths. In course of time, none but
cautious sloths will remain.

The case is similar with the giraffe's neck. In time of
stress, giraffes with unusually long necks will have access to
a better supply of food than giraffes with short necks. The
latter will die out, while the former will survive. On this
assumption, there is no necessity for any inheritance of
acquired characters. The unusual length of neck is a
spontaneous congenital variation, arising by pure chance ;
it is preserved and inherited.

From the à priori view, there does not seem a great deal
to choose between the theories ; and it was the à priori view
that was adopted by Lamarck. Many of the known facts of
evolution might be accounted for either by use-inheritance
or by natural selection. If it is true that acquired characters
are inherited, then the giraffe might well have developed his
neck through that agency. The hypothesis fits the facts.
But so also does the hypothesis of special creation ; for if
God manufactured the giraffe, neck and all, just as we find
him, we immediately reach the goal of our researches on the
matter. Similarly, again, "natural selection is equally satis-
factory as an à priori hypothesis. If congenital variations
are inherited, and if favourable variations have a real sur-
vival-value for the individual, then natural selection might
well have been the true method.

The fact is, of course, that the above mode of reasoning
is a grave abuse of the deductive method. Few, indeed, are

ACQUIRED CHARACTERS xliii

the people who are competent to judge of the correct use of
deduction in difficult biological inquiries. It is not enough
to invent a hypothesis, which covers the facts, and then
regard it as true without further study. In the present case
the facts are covered by at least three different and mutually-
exclusive hypotheses, special creation, inheritance of acquired
characters and natural selection. The à priori method
breaks down hopelessly, and we must resort to the à 'posteriori
method.

Now, no one has ever seen or heard of a genuine instance
of special creation. The doctrine of creation is a pure inven-
tion, fabricated to explain the facts. I think it could very
easily be proved that as a matter of fact it does not afford
the least glimmerings of an explanation of any of the facts ;
but that is by the way. It implies a disruption in nature ;
it is directly and immediately opposed to everything that
we know of natural phenomena ; it has deservedly fallen
to the last degree of discredit among aU who have the sHghtest
knowledge of the subject. Special creation may be left out
of account, because it is an unknown factor in natural events.

Inheritance of acquired characters is a hypothesis that
may be dealt with on the same lines. Many are the attacks
which have been levelled against the theory that acquired
characters can be inherited. One of the most famous is
that of Weismann, with his theory of the continuity of the
germ-plasm. The germinal material, or germ-plasm, he
said, is totally separate and cut off from the body-material
or soma-plasm. Hence, he argued, modifications of the
soma during life cannot by any possible means affect the
germ-plasm : there can be no use-inheritance, because there
is no way in the organism by which it could be accomplished.

This again is a pure deduction : and a dangerous one.
It does not follow in biology that because we cannot see
how a thing works, therefore it cannot work. Some physio-
logists indeed do think they see how the soma-plasm may
specifically affect the germ-plasm. But while we remain
in our present ignorance as to the causes of development,

xliv INTRODUCTION

and of the extraordinary and specific influence which the
pituitary, thyroid, reproductive and other glands exert upon
remote parts of the body, and indeed of many other remark-
able correlations existing between apparently disconnected
parts, our empirical knowledge is surely far too slight to
offer any kind of firm basis for a large-reaching deduction
like that of Weismann.^

The advocates of use-inheritance have in all cases devoted
themselves to proving that it might be the true factor in
evolution : they have then assumed that it is the true
factor. Weismann equally has opposed them on the first
groimd, denying that it might be the true factor. From
this shifting and dubious morass of argumentation, we may
advisedly transfer our attention to the simple question of
fact and experience. And once on this solid ground we
find that not one single proved genuine instance of use-inheri-
tance has ever at any time been discovered.

I have not forgotten, indeed, about the guinea-pigs of
Brown-Séquard, and am well acquainted with the nimierous
alleged facts brought forward by investigators of all kinds.
Not one of them but is susceptible of some other explanation.
It is difficult to deny that use-inheritance often appears the
easiest and most straightforward method : it is just that
very facihty of explanation which gives it such an enormous
hold on untrained minds. Yet the trained biologist will
attach not the shghtest importance to that straightforward
and plausible air, for he well knows that nature's methods
are rarely of the kind that a human being regards as simple
or straightforward. In short, all this is simply going back
to the tiresome question as to whether use-inheritance
might happen. We do not want the production of cases in

* Since the above was printed, I have received advance proofs of Professor MacBride's
forthcoming work on the Embryology of the Invertebrates, through the courtesy of
Mr. Walter Heape, F.R.S., the general editor of a series of text-books of Embryology
shortly to be published. Professor MacBride suggests that the discovery of hormones
by Professor Starling may afford a clue as to a possible modus operandi of the inheritance
of acquired characters. He quotes Professor Langley to the effect that if an animal
changes its structure in response to a changed environment the hormones produced
by the altered organs will be changed : and these altered hormones circulate in the
blood and bathe the growing and maturing genital cells.

ACQUIRED CHARACTERS xlv

which use-inheritance might be the factor concerned, for we
are prepared to admit all along that it may be a factor.
What we want is one indubitable instance that it is a factor —
one case in which the process takes place under our eyes,
in which use-inheritance is not claimed merely as the most
probable of several rival explanations, but in which it is
obviously the only real and true explanation. Nothing
short of this is of the slightest use for throwing light on the
problem before us.

Use-inheritance is so plausible a theory, that if a single
case were brought forward to prove that it is actually a
process occurring in nature, it might well be accepted thence-
forward as an important factor in evolution. At present,
the inductive philosopher must not only refuse to accept it ;
he must regard it as being in contradiction to the probabilities
of the case. For the search for supporting facts has now
been long in progress. The theory was suggested by Lamarck
more than a century ago ; and in the last half-century it
has been discussed with the greatest detail and publicity.
The fact that no instances have been discovered cannot but
suggest, as a reason, that there are none to discover.

The third factor which I named, that of natural selec-
tion, differs profoundly in this respect from the other two.
A priori, it is quite satisfactory : it unquestionably might
explain organic evolution. But we can go much farther :
we know that new races actually do arise by selection ;
we are able to witness the actual process. Hence, selection
is proved to be a vera causa. Like use-inheritance it is
competent theoretically to account for a great part of the
evolutionary process ; unHke use-inheritance it is not invented
for the occasion, but is a process which may actually be
observed to take place.

Lamarck committed the error, eminently excusable in
the age in which he lived, of assuming that when he has
formed a theory which will fit the facts, and when he can
think of no other theory which will also fit the facts, then
that theory must be true. I shall adduce an even more

xlvi INTRODUCTION

striking instance of this tendency when I come to deal with
his physiology ; for in physiology it led him to views much
more conspicuously erroneous than it did in zoology ; yet
we shall find it still harder to condemn him for this particular
paralogism in physiology, since there are a few physiologists
even at the present day (as I shall show) who are addicted
to false reasoning of a similar kind.

That Lamarck should have believed in the inheritance of
acquired characters was, indeed, almost inevitable. Not
only so, but the invention of this hypothesis was a very
remarkable and honourable achievement. Before a true
theory is discovered, the usual routine is for many hypo-
theses to be invented and tested. The discovery of a true
hypothesis is only effected after the rejection of a multitude
of false hypotheses. The invention of a hypothesis such as
the inheritance of acquired characters required a genius of
no ordinary kind : had it not been for this invention, bio-
logists might not yet have reached a knowledge of the great
importance attaching to the discrimination between acquired
and congenital characters. Consider how the facts must
have presented themselves to Lamarck. He saw that all
progeny possess a structure closely resembling that of their
parents : he saw that when one of the parents possessed some
striking feature, not peculiar to its species, some variation
in short, that variation was very commonly transmitted
to the offspring ; once again, he saw that use or disuse of
any part by an individual affected the structure of that
part in that individual, causing it to increase or diminish
in physical size and capacity, so as to produce a variation
from the normal, not distinguishable by any external examina-
tion from the congenital variations. Is it not then perfectly
natural that he should have assumed such acquired variations
to be inheritable ? What possible grounds can he have had
for supposing that variations from the normal are of two
utterly different kinds, one of which is capable of being
inherited, while the other is not ? Is not this just one of
those traps which, as Darwin remarked, nature seems to

ACQUIRED CHARACTERS xlvii

have set up for the express purpose of deceiving investigators,
and which a pioneer is almost dead certain to fall into ?
Why should it have occurred to Lamarck to inquire whether
the origin of a variation may affect its heritabihty ? In
point of fact it never did occur to him. The problem of
inheritance of acquired characters never presented itself to
his mind : he never differentiated them from congenital
variations. There was for him no antithesis between the
two : the antithesis to use-inheritance was for him special
creation and fixity of species. It was these latter doctrines
that he mainly desired to attack, in the interests of an
evolutionary theory ; and he could not understand how
evolution could have occurred without use-inheritance.
But he never had before him the elements of the problem,
as presented to modern minds. Had he lived in modern
times, it is just as likely that he would have been a neo-
Darwinian as a neo-Lamarckian. He saw that structures
were adapted to their functions : hence, he argued, either
the structure must create the function, involving special
creation and design, or else the function must create the
structure, involving inheritance of acquired characters.
When once the problem is stated in this way, we see that
Lamarck unquestionably chose the less untenable and
more plausible of the two theories.

How natural this oversight was, is borne in upon us by
the fact that at the present time almost everyone who is
not a biologist holds just the same opinion as Lamarck did,
on hearing the theory stated for the first time. Disbelief
in the inheritance of acquired characters is almost limited
to trained biologists, though among them it is almost universal.
Lamarck then committed an exceedingly natural and par-
donable oversight, when he failed to observe that variations
from the mean specific type are not all on a par, but are of
two wholly different kinds. And it may even be that the
future will determine that the two kinds are not after all
so different as is commonly held. We now believe that
the congenital variations — strictly called variations — are

xlviii INTRODUCTION

spontaneous, while the variations acquired by the action of
the environment during life — strictly called modifications — are
due to the definite influence of surrounding circumstances.
But it is of course merely âfaçoti de parler to call any variation
spontaneous. A variation must have some cause, and that
cause must be of physico-chemical nature : this is one of
the most fundamental axioms of science. Darwin, when
he spoke of variations as spontaneous, did not mean that
they rose up like a phoenix out of nothing : he meant that
they occurred in a purely fortuitous manner, without any
reference whatever to the preservation either of the species
or of the individual which developed them. He meant that
they had no purpose or design behind them, and in fact
used the word in opposition to finalism or teleology in the
old sense. Nevertheless, congenital variations must have
some physico-chemical cause, and it yet remains to be
proved that that physico-chemical cause is of different
character from the cause which produces acquired modifica-
tions. It may indeed be pointed out that modifications
are purposive, or adapted to meet the individual's special
needs, whereas variations are fortuitous. But the observa-
tion is of no relevance : for natural selection would speedily
extinguish all races where the modifications acquired were
not adapted to the individual's special needs ; moreover,
the distinction between purpose and chance is at best a
shallow and subjective one.

It may further be pointed out that the factor causing
an acquired modification acts on a particular organ or tissue,
whereas in a congenital variation it acts upon the undif-
ferentiated protoplasm of the germ. For inheritance to
take place in the former . case, the somatic modification
would have to be conveyed to the germ-plasm, whereas
in the latter case it is impressed there from the first. But
this is merely a repetition of Weismann's argument that it
is very difi&cult to see how a somatic modification can affect
the germ-plasm in a corresponding specific sense : it is
difficult to see, no doubt ; but nature's methods are not

ACQUIRED CHARACTERS xlix

limited to those that we may easily discern. We do not
at present know the determining factor and immediate
physico-chemical cause of growth and development. We
know only the mediate or more remote causes, such as
nutrition, increased blood-supply, etc. Hence it may quite
well turn out that the immediate cause of an acquired modifi-
cation is of the same nature as that which impresses on the
germ-plasm the tendency towards a specific variation.

If the development of an individual is controlled by the
environmental factors, and if those factors are in the last
analysis of physico-chemical nature, then there seems reason
to suspect that the fundamental difference between a varia-
tion and a modification is not related to any difference in
their aetiology, or in the factors which produce them, but
is dependent almost wholly on the period of the individual's
life at which these factors operate. If they come into
action after birth or before it in the course of development,
they produce a modification apparently not heritable. If
they come into action before development begins, they
produce a variation which is heritable.

Now, if we define the span of an individual's life as the
period contained between the moment of fertilisation of
the ovum and the moment of death, it is obvious that the
rate of development is exceedingly different at different
periods of this life. Take, for instance, a mammal. While
still in the uterus, it passes through every stage of develop-
ment from the protozoon to its own specific type. Before
it is even born, it has traversed with extreme rapidity and
many short-cuts the various stages passed through in the
course of past evolution by the species to which it belongs.
If therefore we judge of the maturity of an individual, not
by the time elapsed since fertilisation, but by the stage of
development attained at any given moment, it is clear that
a mammal, when born, has already passed through by far
the greater part of its life- journey : its career has already
reached the final stage, and verges on complete maturity.
The remainder of its independent career is doubtless, when

1 INTRODUCTION

measured by time, by far the longer portion : but it is really
a mere lingering over the final stage of maturity : as measured
by development, the animal's career at the moment of birth
is very near its termination. The various tissues and organs
are set hard in very nearly their final shape : the morpho-
logical polarisation can no longer be altered except in minute
details. Now it is in this developmentally late stage of an
animal's career that modifications due to environment
are chiefly acquired. How, then, is it to be supposed that
such modifications should leave a deep organic impress ?

Supposing once more we shift attention from the life of
the individual to the life of the race ; and regard a species
as synonymous, not with the mature individuals composing
it, but with the germ-plasm from which they sprout. This
germ-plasm is potentially immortal. Countless millions of
years ago that same germ-plasm which we now carry in our
bodies was already in existence : but it had not then the
power of budding forth a mammal. It had originally
no power of budding forth anything at all. It was
a protozoon, and perpetuated itself as it still does
by division of the one cell into two. But gradually new
qualities were added to this aboriginal germ-cell. The
daughter-cells were not in all cases completely separated
from their parent, and excrescences came to be formed on
the germ-cell, as the evolution of the metazoa was attained.
It is these excrescences only that are mortal. In the progress
of evolution, the character of the excrescence growing from
the germ-cell has greatly altered ; until in some cases it
has assumed the shape of a mammal. But the germ-cell of
the mammal is just the same germ-cell as that which existed
at the outset of evolution. It has innumerable times been
divided in half, and one half has been cast away : but there
has been no other discontinuity either in the individuality
or substance of the cell.

Hence we may regard the germ-cell of a mammal as
having lived and preserved its personality for myriads of
years. During that time it has greatly changed the kind

ACQUIRED CHARACTERS li

of soma that grows upon it : its soma-growing potentialities
have radically altered. These potentialities have been
acquired and modified by intercourse with the environment
through many million years : using the term environment
in the widest possible sense to denote any kind of physico-
chemical cause that produces variation in the germ-cell.
If now some modification is impressed upon the soma of
any individual, and if that modification does really induce
a corresponding alteration of the germ-plasm, it would appear
that such alteration could only be of infinitesimal extent,
since it is brought into contact with a germ-plasm whose
constitution has been moulded into its present form by
factors which have worked for many million years. An
analogy will make my meaning clear.

Suppose that a bullet was fired from one of the nearest
fixed stars such as a. Centauri directly at the centre of London,
and suppose that it travelled the entire distance in a straight
line. Now, when it is starting its journey, suppose that
a new environmental force operates in such a way as slightly
to deflect the bullet from its course. Suppose that this
variation is so excessively small that after travelling on-
wards for a further quarter of a million miles, it is still only
one inch out of its original course. Yet the total journey
before it is so inconceivably great, that it is easy to calculate
that this minute deflection may cause the bullet, not only
to fail striking London, but to miss the Earth altogether.

Now we may compare the career of this bullet through
space with the career of the germ-plasm through time. We
may compare the successive miles accomplished by the
bullet with the successive generations of its parasitic soma ta.
We may compare the force which deflects it from its course
with the factor that causes a variation in the germ-plasm.
And the application is at once obvious. Environmental
factors which have been in operation millions of generations
have caused in the germ-cell a great and permanent varia-
tion : environmental factors which have only just come into
operation will influence the germ-cell to an infinitely minute

lii INTRODUCTION

extent ; and even the continued operation of those factors
through a long succession of generations will cause the
germ-cell to swerve quite inappreciably from its inherited
career.

I do not adduce this analogy for the purpose of defending
the inheritance of acquired characters : far from it. I
adduce it for the following purpose. We find that the
bodies of animals and plants are adapted to their environ-
ment, and we may affirm that they have been moulded into
their present shape by exposure to the forces of the environ-
ment throughout vast periods of time. We may affirm this
without raising any question of the process by which the
moulding occurs : — whether it is exclusively of an indirect
character (like natural selection), or whether more direct
factors are in operation. In any case the structure of the
organism is an expression of the sum-total of the forces
which have acted upon the germ-cell, ever since that early
time when it first became differentiated from inorganic
matter. Now an acquired modification, impressed upon the
soma, can affect the germ, if at all, only as one new force,
whose individual effects will surely be totally obscured
amidst the multitude of the older forces. Yet those effects
may be registered in the hereditary qualities of the germ :
and a gradual repetition of them in the course of innumerable
generations may give rise to a specific and visible variation.

That a functionally-produced modification should so deeply
impress the germ-cell as to leave visible effects on the soma
of the next generation is at present a discredited h5rpothesis.
Indeed, the direct environmental influence has to be con-
tinued for some little time before it can produce any functional
reaction or modification of the soma at all. A physiological
somatic modification can only be caused by a factor which
operates for an appreciable proportion of the life of the
soma. Now the organism consists of two parts : — of the
newly-developed and ephemeral soma, and of the germ-cell
which has existed from the most extreme antiquity. If
such germ-cell can be affected by direct specific influence,

ACQUIRED CHARACTERS liii

we may perhaps assume that that influence has likewise
to be maintained in operation for an appreciable proportion
of the life of the germ : and no proportion would be appreci-
able, at all events among the higher animals, unless it extended
over many thousand somatic generations.

I am fully aware of the hazardous character of such a
speculation. Indeed, it would scarcely be worth mentioning
at all were it not for the suggestion which it involves, that
inheritance of acquired characters, if not entirely fictitious,
is likely to be true only to this extremely mitigated degree.
It suggests, moreover, that the search for evidence would be
more fruitful among protozoa and the lower types of metazoa
than among more complex forms : for in these primitive
animals the soma (where there is one) is less remote from
the germ : it has travelled a far shorter way on its develop-
mental career. It is indeed among such animals and among
plants that the most plausible cases have been cited. But
until the process can be actually observed to occur in at
least one undoubted instance, use-inheritance must continue
to be regarded as an altogether illegitimate hypothesis, and
to be rigidly excluded from our account of the factors of
organic evolution.

§ 6. Classification.

In his classification of animals, Lamarck had recourse to
two fundamentally different methods. If animals in nature
fall into a linear series, it is obviously a matter of first-rate
importance to ascertain the true order in which the species
are arranged in this series. In so doing, no divisions or
groups of any kind are needed. All that has to be done is
to determine the position of each species with reference to
other species, and to ascertain the exact point of the series
which must be allotted to it. This is what Lamarck means by
a distribution générale of animals.

A second important function of his classification is to
draw the lines in the series, which mark off genera,

]iv INTRODUCTION

families, orders and classes from one another. This is
what Lamarck calls classification. Since the series represents
an even and regular progress in complexity of organisation,
the selection of the points on the scale where our lines of
demarcation shall be drawn is purely arbitrary : such divisions
have no objective reality. Thus classification, as Lamarck
conceived it, is not a science, but an art : it involves a
question not of truth or error, but merely of convenience.
Distribution, on the other hand, is a genuine science, not
dependant on our convenience : our attempts at distribu-
tion are either true or false : if true, they correspond to
an order which has actual objective existence.

The word " classification " in modern biology does not
exactly correspond to either of these two terms. We no
longer believe in a linear series of animals : on the other
hand, the groupings and divisions which we make among
animals are not regarded as subjective conveniences, but as
objective realities. The entire collection of living animals
is broken up into discontinuous groups : and the gaps
between these groups are not gaps in our minds, but gaps
in external nature. Hence, modern classification is a true
science. To this extent it resembles Lamarck's distribution
and differs from his classification. I have allowed myself a
certain degree of latitude in deciding when either of these
words is to be translated by the English " classification,"
a word that inevitably carries with it to modern readers all
its modern biological connotations.

It remains only to indicate the services which Lamarck
rendered to classification ; and they were undoubtedly very
great. It was certainly unfortunate that he should have
adopted the conception of a linear series. He not only adopts
it, but most energetically defends it :

" Man is condemned to exhaust all possible errors when
he examines any set of facts, before he recognises the truth.
Thus it has been denied that [animals] can really be arranged
in a true series according to their affinities. . . . Several
naturalists have imagined that the affinities among animals

CLASSIFICATION Iv

may be represented something after the manner of the
different points of a compass. This idea, which some modern
writers think subhme, is clearly a mistake, and is certain to
be dispelled when we have a deeper and wider knowledge of
organisation." Yet it is now known to represent the
facts much more nearly than the linear arrangement of
Lamarck.

The first great service of Lamarck to classification was
in establishing the distinction between vertebrates and
invertebrates. Aristotle, indeed, had detected the profound
difference between these two groups : but he had taken as
his standard of differentiation the presence or absence of
blood : a highly defective standard which was not to any
great extent improved by Linnaeus. It was reserved for
Lamarck, in his course of lectures at the Muséum in 1794, to
direct attention to the immense taxonomic importance of
the vertebral column, and to set up that great primary
division of the animal kingdom, which was long regarded
as final.

The remainder of Lamarck's achievements in classification
lie within the realm of Invertebrata : for it was with these
animals that his professional work at the Muséum was
exclusively concerned. At the time when he assumed the
task of organising the vast collection of animals accumulated
there, Linnseus's classification of invertebrates into insects
and worms was still current. In that same course of lectures
in 1794, he broke up the class of worms to form four new
classes : molluscs, worms, echinoderms, and polyps. These
divisions had already been suggested by Bruguière as orders
in the old class of worms. Lamarck did not then touch
Linnaeus's class of insects, which comprised the whole phylum
of arthropods.

The arrival of Cuvier in Paris in 1795 produced a general
stimulation of biology, from which Lamarck was not slow
to profit. The medusae and other radiating coelenterates
had been grouped by Linnaeus with the molluscs, and that
classification was still maintained. Lamarck removed them

hi INTRODUCTION

from the molluscs, and combined them with his class of
echinoderms to form the class of radiarians.^

In 1799 Lamarck removed the crustaceans from among
the insects, and erected them into a separate class. This
innovation was not recognised for some years. In the follow-
ing year he performed a still more remarkable achievement,
in separating the arachnids from the insects, and conferring
class-distinction on them also. Up to the date of publica-
tion of the Philosophie Zoologique, this class had not been
admitted in the work of any other naturalist. Lamarck
further reduced the old class of worms by separating from
them the new class which he called annelids. This important
innovation likewise took some years before it received general
recognition. Lastly, he established the class of infusorians,
as distinct from his previous class of polyps. Lamarck's
infusorians correspond of course to what we now call Proto-
zoa ; but there was a good deal of confusion as to what
animals were infusorians and what polyps, owing to deficiency
of observation. Minor improvements in classification were
also numerous. He removed the cirrhipedes, for instance,
from the neighbourhood of annelids and molluscs : he
recognised the gastropod affinities of pteropods, etc., etc.

In the present work, Lamarck gives a list of all genera
known at his time, arranged in their proper order and
classification. The names of the genera are not given in
Latin, but in French ; and for a large number of them
Lamarck himself appears to have invented popular names,
based on the scientific names. It has therefore been a
matter of considerable difficulty to ascertain precisely to
what animals he is alluding in each case. The difficulty is-
still further increased by the fact that many of these genera
are no longer recognised : a large proportion of them in
fact are far more allied to what we should call families than

^ Professor Packard, who some years ago published in America extremely literal
translations of certain parts of Lamarck's work, translates radiaires as radiata. This
is somewhat ambiguous ; for Cuvier's class of radiata is far wider than Lamarck's
class of radiaires, and includes infusorians, polyps and many worms. The correct
translation is radiarian. I preserve the popular style.

CLASSIFICATION Ivii

to modem genera. Lamarck did not intend his list to be
precise, or indeed do more than give a general idea of the
extent of the animal kingdom. Hence his use of trivial
names. In order to find out what animals he meant by
these names, I have in the case of invertebrates referred to
each one in Lamarck's later work, Animaux sans Vertèbres,
second edition, 11 vols., where the French name is almost
always given in conjunction with the Latin name. For
vertebrates I have used Duméril's Zoologie Analytique,
1806. In a few cases, I have traced the meaning through
Cuvier's Règne Animal, or through the Encyclopédie Méthod-
ique, 196 vols., 1782-1832, to which Lamarck himself con-
tributed. Having ascertained to what genus Lamarck
refers, I have translated it by the current English name,
where there is one, so as to preserve the resemblance to the
French original. In other cases, I have employed the Latin
generic name to which Lamarck's French name was intended
to correspond. As I have already said, it often corresponds
to no genus now recognised, as, for instance, the "Pongo " ;
in other cases it much more resembles a family than a genus.
Readers must not therefore expect to find any precision in
this classification that would satisfy modern standards.
The names are often not precise enough to designate clearly
any particular group, and the groups themselves are often
similarly vague and undetermined, or even altogether
mythical. As an instance, let me take Lamarck's genus
" fasciole," belonging to the order of " flat worms." I find
that the generic name which he intended to suggest was
" Fasciola," and I find further that this was a genus
founded by Linnaeus, and appHed by him to three different
animals, the liver-fluke, a cestode, and a triclad, which he
confused together, on account of a superficial resemblance.
Lamarck's first class is that of infusorians, with its two
orders of naked and appendiculate infusorians. The former
mainly correspond to our Protozoa : the latter includes
Cercaria, now known to be a larval form of trematodes.
Lamarck also regarded the human spermatozoon as an

Iviii INTRODUCTION

infusorian : — a view which continued to subsist down to the
early researches of KolHker.

His second class is that of polyps, the first order of which
is the rotifers : among them he includes Vorticella, which is
a real infusorian. The second order include the polyps, which
form polyparies. This corresponds to a mixture of Hydro-
zoa and Anthozoa with Polyzoa. It includes the sponges
as one genus, a few Algae, including Corallina, an echinoderm,
an arthropod, the ascidian Botryllics, etc. The last genus
of polyps, the genus therefore which Lamarck regarded as
having advanced farthest in development, is the sea-anem.one.

Lamarck's third class are the radiarians, with two orders.
The first order, or soft radiarians, contain all varieties of
coelenterates, except Anthozoa. They are grouped together
on account of their radiating structure, with the medusa as
a type. This order includes also the tunicate Pyrosoma.
The second order of radiarians are the echinoderms. La-
marck includes Sipunculus — a gephyrean — as an echino-
derm, on account of its resemblance to holothurians : and
this classification was still retained as late as 1841 by Forbes
in his British Starfishes. It constitutes Lamarck's highest
genus of radiarians.

Class IV. contains the worms, divided into three orders
of round worms, bladder-worms, and flat-worms. Among
the latter is included Linguatula (an arthropod), and Fasciola
already mentioned. The round worms are chiefly nematodes,
but include also turbellarians, cestodes, etc., and one genus
" Scolex " (the tape-worm's head). Among the bladder-
worms is placed an animal under the name of bicorne. On
reference to the Animaux sans Vertèbres, I find it alluded
to as Ditrachyceros. I believe that the separate segments of
tape-worms were referred to under this name, being taken for
independent individuals. At a certain stage, the segments do
sometimes show two horn-hke processes.

Class V. contains the insects, divided into much the same
orders as at the present day.^ The next higher class, Class

^ There are a few minor inaccuracies, such as the statement that the Hemiptera

CLASSIFICATION lix

VI., consists of the arachnids, estabhshed for the first time
by Lamarck himself. It comprises two orders, the first of
which corresponds to our modern class of arachnids, while
the second (" arachnids with antennae ") includes our
modern myriapods, together with one or two insects such
as the louse and silver-fish.

Class VII. are the crustaceans, divided into the two orders
of those whose eyes are at the end of stalks, and those whose
eyes are sessile. In the next class, that of the annelids,
Lamarck discerns the commencement of a tendency on the
part of nature to abandon the articulatory type in favour
of the vertebrate type. Thus he finds that annelids no
longer have jointed legs, as in the classes immediately pre-
ceding. The class is divided by Lamarck into two orders,
of which the first — ^the Cryptobranch annelids — is a mixture
of various ill-assorted animals, including a triclad and two
copepods.^ The order includes Lumbricus and Nais : though
curiously enough, in his later and more systematic work,
Lamarck restored Nais to his class of worms, removing it
from the annelids. The second order, the Gymnobranch
annelids, consists of polychaets, with the addition of two
molluscs at the end.

Class IX. are the cirrhipedes, with only four known genera.
They are intermediate between the annelids and Class X.
containing the molluscs. Lamarck regarded the molluscs
as the highest class of invertebrates. For some time, he
says, Nature had been making preparations for originating
the vertebrate plan of organisation. In the molluscs those
preparations are completed. The articulatory system ac-
cordingly vanishes : and the slow movements of molluscs
are due to the fact that the class is midway on the road of
development from an external to an internal skeleton, and
therefore possesses the advantages of neither. It is to be
noted that Lamarck had a very clear conception of the

have three setae in their sucking-organ. As a matter of fact they always have four ;
though two are often united together, so as to give the appearance of only three.

^ The triclad (Planaria) is removed to its proper position in the Animaux sana
Vertèbres.

Ix INTRODUCTION

arthropod type, and if his scheme of classification had
admitted of groups superior to classes, there is no doubt
that he would have combined the insects, arachnids and
crustaceans into one phylum, altogether separate from the
molluscs, though the annelids and cirrhipedes are regarded
by him as intermediate forms.

Lamarck divides molluscs into two orders of Cephalic and
Acephalic. The latter of course consist mainly of the
modern lamellibranchs. One section of this order, however,
contains the brachiopods, and another section the tunicates,
which he took to be molluscs. Lamarck's Order II. are the
Cephalic molluscs. It is divided into the three sections of
pteropods, gastropods and cephalopods. Nearly half the
animals included by Lamarck under the name of cephalopods,
consist of Foraminifera ; most of the remainder are genuine
cephalopods. One of the Foraminifera, which Lamarck
mistook for a cephalopod, is Orbulites, which here occurs
for the second time in his animal scale ; for this animal had
already been once named as belonging to the polyps.

These are the main features of Lamarck's classification of
the invertebrates. That he should have evolved these ten
classes, with their various orders, out of Linnseus's insects
and worms is an achievement of no small magnitude. We
now come to the vertebrates, to whose classification Lamarck
never made any contribution. I may therefore rapidly
run through the classification which he here adopts from
what he believed to be the best authority of his time.

Class XL contains the fishes. They are divided into two
orders of Cartilaginous and Bony fishes ; though Lamarck
includes among the Cartilaginous fishes a number of our
modern ganoids and teleosts. This order commences with
the hagfish and lamprey, correctly placed together as cyclo-
stomes : Linnaeus had previously regarded the hagfish as
a worm. The second order of Bony fishes mainly consist of
" Holobranchs," or fishes with complete gills. These holo-
branchs are divided into thirty sections, largely determined
by the character and position of the fins, as also by the gills.

CLASSIFICATION Ixi

opercula, general shape, etc. This classification has now
been altogether discarded, and the modern subdivisions of the
Fishes are on quite different lines. Lamarck terminates the
class with the " ophichthians " or " snake-fishes," doubtless
because they seem to come nearest to the next class of reptiles.

The reptiles, Lamarck's Class XII., are divided by him
into four orders. The first order of " Batrachian reptiles "
are what we now call amphibians, and are not reptiles at
all. The second order is the snakes, the third lizards, and
the fourth chelonians or tortoises, which apparently Lamarck
regarded as the nearest approach to Birds. The birds to
which Class XIII. is devoted were divided by Lamarck into
the seven orders of Climbers, Birds of Prey, Passeres, Col-
umbae, Gallinaceans, Waders and Palmipeds. The further
subdivisions of these orders are largely dependent on the
character of the beak. The four orders which Lamarck
placed first, and therefore regarded as most primitive or
" least perfect," contain birds which depend on their parents
for food, etc., after being hatched. The last three orders,
which he regarded as the highest, contain the birds which
can look after themselves as soon as they are out of the
egg. He thus completely inverted the true significance of
this particular criterion of development ; for we now know
that it is the most highly evolved animals in which the young
are least capable of looking after themselves. In the case
of man, it is many years before the new individual can reach
a state of independence.

Following the birds, Lamarck introduces the monotremes,
including Ornithorhyncus and Echidna, as being half-way
between birds and mammals. His fourteenth, and last class,
contains the mammals, which are divided into the four
orders of exungulate, amphibian, ungulate and unguiculate
mammals. The exungulate are what we call the cetaceans.
The amphibians comprise the seal, walrus, dugong and
manatee. The ungulates correspond to the modern order
of that name ; and the remainder of the mammals are
included among the unguiculates. The sub-divisions of

Ixii INTRODUCTION

this order are not uninteresting. He recognised the families
of edentates, rodents, and Chiroptera, and referred genera
to these families, on the whole with fair accuracy. He also
recognised the marsupials, under the name of Pedimana.
His highest, or " quadrumanous," family corresponds to
our Primates. But the remainder of the exunguiculate
mammals are divided into tardigrade, plantigrade and
digitigrade, according to their method of walking. The
tardigrade or slow- walker contains the solitary ^enus of the
sloth, which Lamarck thus separated from the edentates,
although placing it in contiguity with that group. The
plantigrade and digitigrade mammals are those which walk
respectively on their whole feet, or on their toes. Lamarck
thus had no conception either of the Carnivora or of the
Insectivora. The Carnivora he divides up among the planti-
grades and digitigrades. The Insectivora fall to the family
of plantigrades, with the exception of Galeopithecus, which
he somewhat excusably referred to the Chiroptera. The
anthropoid apes are represented by the " Pongo " and the
" Orang," both very vague genera. There were said to be
two species of Orang, the Orang of the Indies, and the Orang
of Angola, the latter no doubt being the Chimpanzee.

It is not quite clear how Lamarck thought that man was
related to the animal scale. Throughout the work he con-
stantly refers to man and animal in antithetical terms. He
did not regard man as an animal, in the same sense as other
animals ; but he perceived that by confining his attention
entirely to a study of structure, man might be classified as
one family of mammals. This family he calls " Bimanous,"
and divides into six varieties — Caucasian, Hyperborean, Mon-
golian, American, Malayan, and Ethiopian or Negro.

It appears highly probable that Lamarck recognised the
common origin of man and other animals, but that he did
not venture to proclaim it. He elaborates a hypothesis as
to how man might have developed, if he were only distinguished
from other animals by his structure and organisation. Ac-
cording to this hypothesis, the evolution of man would be

CLASSIFICATION Ixiii

due to inheritance of acquired characters. Lamarck supposes
that some race of apes conceived a desire to obtain distant
views over the country, and for that reason contracted the
habit of standing up on their hind legs, to get a better view.
The constant assumption of this posture would, according
to Lamarck, produce suitable modifications of structure,
which would be inherited : in course of many generations,
the erect position would become the normal one. The modi-
fications of feet and jaws are accounted for on similar lines.
Lamarck assumes that as the human race became dominant,
it would everywhere be brought in contact with a new
environment, develop new wants, and make efforts for the
satisfaction of these wants. These efforts would result in
corresponding structural alterations, which would be inherited.
Thus, he regards the origin of language as due to the constant
efforts to impart ideas. These efforts, by use-inheritance,
would cause the necessary development of the throat, mouth
and lips. When once language had been acquired, and
conventional signs agreed upon, man had scattered over the
earth, varieties of the original language had arisen, until
ultimately the existing diversity of languages was attained.
Meanwhile the development of other races of apes would be
hindered by that of man, for man would persecute them and
drive them from the hospitable regions of the earth. But
all this is merely put forward as an hypothesis, to explain
how the structure of man might have been derived from
simian ancestry by ordinary biological laws : but Lamarck
cautiously repudiates at the end any suggestion that he did
arise from simian ancestry.

In his later classification, printed in the " Additions " to
Part I., Lamarck made certain improvements in his classifica-
tion, in the direction of abandoning the linear series. He
held that the animal kingdom originated by spontaneous
generation in two independent roots, the infusorians and
the worms. From the former were derived the polyps and
radiarians alone. The worms, on the other hand, or at

Ixiv INTRODUCTION

least the aquatic worms, as opposed to the parasitic worms,
Gordius, for instance,^ led straight to the annelids, and
through them to the cirrhipedes and molluscs. Other
aquatic worms took to the air and gave rise to the insects
via gnats and mayflies. Insects, adopting soHtary habits,
became arachnids ; and arachnids, taking once again to
water, became crustaceans.

The molluscs, continuing Lamarck's exposition, led to the
fishes through a regular gradation of other molluscs still
remaining to be discovered : and the fishes to the reptiles.
The reptiles, he said, were differentiated by environmental
action into two divisions, of which one led to the birds,
via the chelonians or tortoises, and thence to the mono-
tremes ; while the other led to the Amphibian mammals
via the saurians, especially of the crocodile type. Of the
Amphibian mammals, some took to feeding on grass on the
sea-shore, like the walrus and manatee,^ and so brought
about the development of the ungulates. Others, such as
the seal, confined themselves to an animal diet, and thus
led to the unguiculates.

§ 7. Physiology.

On approaching a work of philosophical physiology written
a century ago, the point to which we look with the greatest
interest is the attitude of the writer towards the ancient
problem now bearing the modern name of vitalism. Through-
out last century, controversy was ever returning to that
great and fundamental question as to whether organic pro-
cesses or functions are due exclusively to the ordinary laws
of physics and chemistry, or whether those laws are sup-
plemented by others of a spiritual or non-material character.
When the problem is looked at with an exclusively physio-
logical interest, the opposite schools are referred to as vitalism

* He referred, no doubt, to the free sexual form.

• This is, of course, a mistaken observation. The walrus is almost or completely
carnivorous, while the manatee feeds exclusively on aquatic plants below the surface
of the water. Neither animal has the habit alleged by Lamarck.

PHYSIOLOGY Ixv

and mechanism. But this physiological question has a far
deeper philosophical interest ; and when the problem is
regarded from that wider point of view, the opposite schools
are those loosely described as spiritualism and materialism.

The method of science is now, and always has been,
exclusively materialistic : that is to say, the sole data of its
investigations are matter and energy ; every event, that
receives a scientific explanation, is analysed into some par-
ticular combination of matter and material energy. Now it
happened at the dawn of civihsation that men began to
speculate about the causes of things long before they had
any science or organised knowledge to guide them ; long,
therefore, before there was any possibiHty of their finding
those causes. In this position the mental craving was met
by the invention of a new kind of entity, different from
matter, and called spirit. All difficulties were immediately
levelled : What causes disease ? An evil demon. Why do
the winds blow ? A spirit is responsible. What is the
origin of the universe ? A god or gods made it ; and so on.
Thus all things received an easy explanation. I need not
recite the oft-told story of the dechne of spirits and the rise
of materiahsm in conjunction with the advance of civilisa-
tion. In no instance did the progress of knowledge reveal
the true existence of any entity apart from matter. One by
one the spirits were driven from the field of explanation : at
the present time they are all but banished from scientific
method, and survive only in extremely mitigated form in
the imaginations of the vulgar.

Nowhere has the struggle been more strenuous than in
the region of physiology. Of all subjects which have excited
the curiosity of man, few are more enthralling, and few more
beset with difficulties, than the causes of the manifestations
of hfe and movement by which certain portions of matter,
named organisms, are differentiated from inorganic matter.
The difficulty was of course met in olden times by the hypo-
statisation of a new entity, often called the soul, but assuming
a vast variety of different shapes and conditions according

Ixvi INTRODUCTION

to the fancy of the inventor. There is no longer any reason
to doubt that physiological processes are exclusively material,
like all other processes in the universe ; and that there exists
no independent entity of this character, as was assumed in
times of ignorance. Nevertheless, so highly complex is the
subject, and so pressing is the demand for some immediate
explanation, that there are still a few physiologists remaining
who invoke spirits to assist them in accounting for certain
phenomena that have yet been scarcely reached by the
rising tide of materialistic science. It is true that they are
not often rash enough to invoke an actual spiritual sub-
stance. They prefer to speak of " biotic energy " or " vital
force " : that is to say, they invent a spiritual form of
energy, rather than a spiritual form of substance. But
there is no essential difference whatever between the two.^
If they affirm the existence of any kind of vital or spiritual
force, of non-material character, they are inexorably com-
mitted to a belief in souls or some such spiritual bodies.
Notwithstanding their protestations to the contrary, they
have no logical escape from the position. These physio-
logists urge vitalism almost exclusively on the grounds that,
without the assumption of a vital force, it is impossible to
explain certain of the more complex manifestations of
intelligence, voluntary movement, choice, etc. Now it is
but a short time back that even quite simple nervous pro-
cesses, such as reflex action, were impossible to explain by
mechanical or physico-chemical methods. It is now known
that these simple processes are in point of fact of a purely
mechanical nature ; and it is also very widely believed by
the great majority of physiologists that the more complex
cerebral operations are based entirely upon the reflex prin-
ciple, and indeed are nothing more than reflex action,
multipUed and compounded to a high degree of complexity.
So far then from there being any apparent impossibility
about explaining the highest mental manifestations on

^ On this point, v. my article in Bedrock for October, 1912, with the ensuing con-
troversy.

PHYSIOLOGY Ixvii

mechanical principles, those principles would appear, even
at the outset of the discussion, to offer by far the most pro-
bable solution. But, in any case, the argument from impossi-
bility is one that has no weight whatever.

I take it that one of the chief values of a historical study
such as the present is to establish a comparison between the
methods of the past and the methods of the present, so that
we may know not only where our ancestors failed, but why
they failed, and how we may avoid a similar fate. " Nur
durch Werden wird das Gewordene erkannt." In describing
Lamarck's physiological philosophy, I shall therefore pay
special attention to certain instances of the modern use of
the same type of argument, which led in his hands to so
miserable a failure.

Lamarck held that three things are necessary for the
constitution of Hfe. There must be the soHd parts of the
organism, the liquid parts, and the " exciting cause " of
" organic movement." The solid and liquid parts require
little illustration. Lamarck describes the solid parts as
being " supple " and " containing," and the liquid parts as
*' contained." Life is constituted by organic movements,
or movements of the contained liquids through the containing
solid tissues. The liquids to which he referred were of
course the blood and other visible fluids of the organism.
But in order to maintain this movement an " exciting cause "
or stimulus was needed, and to this exciting cause we must
pay further attention.

Let me do Lamarck the justice to say that he repudiated
altogether a " vital principle." "The ancient philosophers,"
he says, " felt the necessity for a special exciting cause of
organic movements ; but not having sufficiently studied
nature, they sought it beyond her ; they imagined a vital
principle, a perishable soul for animals, and even attributed
the same to plants ; thus in place of positive knowledge,
which they could not attain from want of observations, they
created mere words to which are attached only vague and
unreal ideas.

Ixviii INTRODUCTION

" Whenever we abandon nature, and give ourselves up to
the fantastic flights of our imagination, we become lost in
vagueness and our efforts culminate only in errors. The
only knowledge that it is possible for us to acquire is and
always will be confimd to what we have derived from a
continued study of nature's laws ; beyond nature all is
bewilderment and delusion : such is my belief."

Lamarck thus affirms the mechanistic position, but he
goes on to say that the " exciting cause " is composed of
two factors, caloric and electricity. These he regarded as
subtle, invisible fluids which penetrate every part of the
organism. Its life is mainly due, he says, to caloric, and
its active movements to the electric fluid, or, in the case
of the more complex, to the galvanic fluid. These fluids
may indeed be somewhat specialised within the organism,
and other subtle invisible fluids may co-operate with them,
but Lamarck looked upon it as quite certain that they
were the chief components of the exciting cause, that en-
dows bodies with life. Now this exciting cause is obviously
analogous to those spiritual factors, which Lamarck is so
careful to exclude. It is descended directly from the
" animal spirits " of more ancient writers, like Galen, and
it has strong vitalistic implications ; he goes so far as to
refer to heat, the most important of the subtle, invisible
fluids, as the " material soul of living bodies." Yet we
must remember that the so-called subtle, invisible fluids
were recognised by the physics of Lamarck's day. When
invoking the aid of these fluids for the explanation of physio-
logical phenomena, he was drawing on what he believed to
be a purely physical source, and he constantly impresses upon
the reader that his explanations are exclusively physico-
chemical. The fact is that physics was at that time
imperfectly differentiated from metaphysics : Lamarck de-
rived his " exciting cause " from metaphysical elements,
which have since been entirely discarded : and he fell into
a semi-vitalistic mode of explanation, in spite of his desire
to keep free from it. Lamarck comes nearest to the modern

PHYSIOLOGY Ixix

vitalistic writers when he attempts to describe the physiology
of the nervous impulse. He attributes it to a " nervous
fluid," and this, he says, is no other than electric fluid which
becomes modified and " animalised " on entering into the
bodies of the higher animals.

By what reasoning did Lamarck reach this conclusion ?
The facts before him consisted mainly in the rapid trans-
mission, of some kind of impulse from or to the brain from
remote regions of the body. Lamarck considers how this
transmission could be accomplished : he passes in review
all possible alternatives : Eicherand had refuted the sugges-
tion that some vibration of the nerves conveyed the mysterious
impulse : there remained only two possible alternatives :

(1) that the impulse should be carried by the visible or
" essential " fluids of the animal, such as blood and lymph ;

(2) that it should be carried by invisible fluids analogous or
identical with the electric, galvanic and magnetic fluids.
The first alternative is ruled out by many facts : in the
first place no such movement of the visible fluids can be
detected in nervous action : in the second place, the visible
fluids are too gross and heavy to move with the required
velocity, which Lamarck affirms (quite wrongly of course) to
be nearly equal to that of light : and so on. All conceivable
alternatives being thus ruled out, it follows, says Lamarck,
that the one remaining unrefuted possibility must be the
true explanation : there must be a subtle, invisible fluid of
the character named above.

Now I wish to point out that this argument is identical
in every particular with that by which Hans Driesch and all
other vitalists of our time prove the existence of a vital force.
Driesch names the argument 'per exclusionem. Like Lamarck,
he takes three or four conceivable alternatives ; though I
need hardly say that the conceivable alternatives of to-day
are radically different from the conceivable alternatives of
a hundred years ago. He then refutes all possible alterna-
tives but one : and thereupon announces that that one (the
vital or spiritual force) is the true explanation, conferring

!xx INTRODUCTION

upon his argument the title of a " proof of vitalism." Now
this argument fer exclusionem is sound, upon one condition
only ; and that is that all possible alternatives have really
been marshalled together at the outset of the argument.
This is a condition which, in the present state of physio-
logy, is entirely impossible to satisfy. It is interesting to
note that, of the various possibilities named by Lamarck,
not one figures in the list of possibilities named by Driesch.
A century has swept them all away, and brought out a
whole series of new possibilities, never dreamt of by Lamarck.
Few students of the history of science can doubt that another
century, or much less (for things move faster now) will
sweep away no less effectively Driesch's list of possibilities.
In order to name every conceivable mode of explanation of
any phenomenon, it is necessary to know infinitely more
about the conditions of that phenomenon than is at present
possible in any branch of physiology. We have to know
that we have exhausted every possible alternative ; we have
to know that there is nothing more to be known ; and that
is a condition of the most extreme stringency. This argu-
ment, or some attempt at it, has served as proof of every
kind of erroneous explanation of the universe, and all things
in it, great and small. The ancients vaguely used that
method when they affirmed the existence of animal spirits :
by the same method, Lamarck proved the existence of a
subtle, invisible nervous fluid racing up and down the
nervous system : by this method again, Driesch proves the
existence of a vital force. I challenge anyone to find the
slightest difference between Lamarck's method of proving
the existence of the nervous fluid, and Driesch's method of
proving the existence of the vital force. This logical method,
dignified by the name of per exclusionem, is indeed a method
of argument by which nearly all untrained minds, and a
great many trained minds, are wont to establish propositions
they desire, in place of the disagreeable confession of ignorance
or agnosticism. It is at the bottom of every vitalistic theory.
*' Here is a process difi&cult to explain : it cannot be caused

PHYSIOLOGY Ixxi

this way, or that way, or the other way : hence the only
remaining conceivable explanation must be the true one."
And then ensues some ridiculous theory, always depending on
a new, mysterious, and invisible agency : it has to be invisible
of course, since no power of microscope or balance can dis-
cover it. Hence we get spirits, animal spirits, souls, subtle
fluids, vital forces and other " monstrous products begotten
by the imagination," as Lamarck himself well calls them
elsewhere. These agencies are in turn relegated to the
sphere of superstition, as science grows. Lamarck claimed
the support of science for the existence of subtle invisible
fluids : science has entirely disposed of them. The nervous
impulse is still not properly explained : and doubtless until
it is, it will continue to be regarded as a suitable playground
for spiritualistic fancies and desires. But year by year
these phantoms find it harder to discover any dark and
unexplored corners of science, where they may obtain a
momentary respite from the ever-advancing tide of material-
istic knowledge.

To do Lamarck justice, his theory was not so outrageous
as is that of the modern vitalists. He invoked a factor,
which he imagined (wrongly no doubt) to be equally instru-
mental in the inorganic world. His subtle fluid was not
invented ad hoc ; it was recognised as a real existence by
many physicists of his time. But the modern vitalists
invent a factor that is wholly and unutterably new to science,
and to every branch of knowledge or history. Their plunge
into the unknown is far wilder and more furious than his.
Their search for a hypothesis has led them to the most remote
regions of primitive superstition ; it has led them to invent
a factor out of hand for the purposes of their own theorisa-
tion — a factor unknown to any branch of science, a factor
unrecorded in any trustworthy history, a factor which breaks
down utterly and immediately under analysis, and lastly a
factor which, so far from explaining the facts it is supposed
to explain, throws over them an impenetrable cloud of
mystery ami obscurity.

Ixxii INTRODUCTION

Lamarck begins his physiological section with an account
of the distinguishing features between the organic and the
inorganic. He reduces the differences to nine. An organism
has an individuality of its own : it is necessarily heterogene-
ous : it comprises solid parts and fluid parts : its different
parts are mutually dependent on one another : it undergoes
what we should now term metabolism : it grows, not by
external accumulation of matter, but by " intro-susception " ;
it feeds ; it reproduces itself ; and it dies. None of these
peculiarities, says Lamarck, are exhibited by inorganic
matter. Lamarck's next task is to differentiate between
animals and plants. The most important distinction, he
says, is that the former possess irritability, while the latter
do not. By irritability, he means an immediate reaction ta
contact of a foreign body : the point of the organism where
the contact occurs, contracts with neighbouring parts : but
upon cessation of the stimulus, the parts are immediately
restored to their former condition, ready to respond again
to any new stimulus.

Lamarck's theory of irritability is based upon his theory
of " orgasm." I have already said that he regarded an
organism as essentially composed of solid and supple " con-
taining " parts, through which travel the " contained "
visible fluids. Now the solid and supple parts were regarded
by Lamarck as being permanently in a state of distention,
due to the presence within them of caloric and other subtle
invisible fluids. These fluids were " expansive " ; so that
the supple parts to which they had penetrated were thrown
into a condition of distention, or, as Lamarck calls it,
*' orgasm." When very intense, the orgasm gives rise to
erethism : when insufficiently intense, to atony.

From his theory of orgasm, naturally flowed his theory of
irritability. On contact of a foreign body, the subtle invisible
fluids are promptly dispersed in the neighbourhood of the
point touched. The orgasm or distention is reheved, and
the parts concerned immediately collapse or contract. On
cessation of the stimulus, the subtle fluids promptly suffuse

PHYSIOLOGY Ixxiii

once more the part in question, and restore to it its orgasm
and readiness for a new contraction on application of a nevr
stimulus.

Lamarck regarded life as synonymous with " vital move-
ments," that is to say, with the movements of the visible
contained fluids through the supple containing parts. The
function of the " exciting cause " is purely to keep the fluids
moving, though exactly how it does this is left unexplained.
But the entire phenomena of life, its origin, development,
and evolution, are attributed by Lamarck to the movement
of the fluids through the solids, under the mysterious influence
of the exciting cause.

As regards the origin of life, Lamarck held that it came
about in this way : gelatinous or mucilaginous particles are
lying about in nature : it happens that some of these consist
of solid and fluid parts, and are in all other respects fitted
for the reception of life ; thereupon the subtle invisible
fluids, which he imagined to be spread everywhere over the
surface of the earth penetrated these particles, and acted as
the " exciting cause " which starts the visible fluids moving
through the supple solid parts : and that is the commence-
ment of life. The particles of gelatinous character become
primitive animals ; those of mucilaginous character become
primitive plants.

When once the fluids begin to move, they soon create hollow
spaces or " cells " within the solid matter ; and Lamarck
very warmly defended the theory that all organic matter is
either cellular or the product of cells. In this respect he
entirely anticipated Schwann ; unfortunately his cellular
theory was mixed up with too many crudities to secure
the scientific approval of his time. This is but one instance
of many in which Lamarck anticipated the knowledge of
a future age.

Lamarck, having accounted for the origin of life by
means of the " vital movement " of the visible or essential
fluids, proceeds to account for development on the same
principle. The fluids carve out canals and hollows of all

Ixxiv INTRODUCTION

kinds : whence we get the various vessels and cavities of
the interior. Moreover, they deposit certain substances,
formed within them. These deposited substances begin to
accumulate in special places, giving rise to the formation of
organs.

Lamarck held that spontaneous generation took place in
the way described above. He held that it still continues to
take place, wherever there happens to be lying about a
particle of matter of gelatinous or mucilaginous consistency,
suitable for vitalization by the ubiquitous invisible fluids. He
held that the organisms at the beginning of the animal and
vegetable scales are produced by spontaneous generation,
which as regards animals he was at first inclined to limit to the
infusorians, but subsequently extended to the worms. At first
the reproduction was by buds or gemmae ; subsequently it
became sexual. Lamarck regarded sexual fertilisation not as
the initiating point of development, but as a preliminary opera-
tion by which a gelatinous or mucilaginous particle of matter
was rendered fit for the reception of life. He considered that
it did not even confer life : the unfertilised ovum was not a
living thing, nor capable of " possessing life " : after fer-
tilisation, it was still not living, though now it had become
fit for Hfe. Life itself, he beHeved, was conferred by the
subsequent application of a gentle warmth of the nature of
incubation. This view naturally follows from the identifica-
tion of life with a movement of the contained fluids.

It is not clear how Lamarck supposed that fertilisation
prepared the ovum for the reception of life. He conceived
that fertilisation consisted in the emanation of a " subtle
penetrating vapour " which escaped from the sperm and
penetrated the ovum. This " invisible flame or subtle and
expansive vapour " was the " aura vitalis," which Spallanzani
had long previously disproved. Spallanzani clothed a male
frog during cohabitation in a pair of trousers through which
subtle penetrating vapours could pass, but no organic matter :
no fertilisation was found to ensue. Spallanzani thus com-
pletely proved the materiality of the process of sexual

PHYSIOLOGY Ixxv

reproduction, and Lamarck's revival of the " aura vitalis "
or semi-spiritual theory constitutes a grave indictment of
his scientific judgment. It is possible, however, that he
was not aware of Spallanzani's experiment, though he
mentions that savant in another connection.

Lamarck's chemistry was that which prevailed before
Dalton had formulated the Atomic theory, and is con-
sequently by no means easy for a modern reader to
understand. It is enough, however, to observe that he
regarded the sum-total of living things as being (as indeed
they are) an immense and ever-active laboratory. He held
that all substances, organic and inorganic, were the produce
of organisms. In their bodies, he says, are elaborated all
known complex substances ; from their decomposing remains
spring all inorganic and mineral substances. How the first
gelatinous or mucilaginous corpuscle came to be lying about,
when there was nothing for it to lie about on, is unexplained :
but perhaps it is unfair to approach too nearly to first causes.

The subtle invisible fluids which become the " exciting
€ause " of life, and hence of chemical synthesis in organic
matter, behave in exactly the opposite way in inorganic
matter, which they ever tend to decompose into its elements
or " principles." Lamarck's theory as to the causes of
death is not without interest. The solid parts of the organism
■are composed of various substances, and are subject to a
constant metabolism. In the course of katabolism, the less
solid and more volatile parts would be given off most freely.
In anabolism, the new substances brought would be only of
the average consistency. Since the most volatile parts are
thus constantly being replaced by less volatile parts, the
substance of the organism tends to an increasing rigidity
and hardness ; it can support only a diminished distention
from orgasm, and finally becomes incapable of the further
maintenance of life.

The rest of Lamarck's physiology is of no special interest.
He held that there are certain " faculties " common to all
living bodies, such as growth, nutrition, reproduction ; and

Ixxvi INTRODUCTION

that there are others limited to some living bodies only, such
as respiration, circulation, sexual reproduction, intelligence,,
etc. Each of these " faculties " begins at a certain point
in the animal scale. Subsequent to that point it develops
with tolerable regularity in its progress towards perfection ;
anterior to that point it is completely wanting.

§ 8. Psychology.

Of the various philosophical questions agitated among the
group of materialists in the latter half of the eighteenth cen-
tury, none occurred more frequently than this : " Can matter
think ?" A man is made of matter ; a man can think :
hence matter must be able to think. A syllogism of this kind
was at the basis of the question. Yet it was found very hard
to admit that matter can think. The question was mainly
agitated among the men of science and the materialistic
philosophers : the spiritualistic philosophers got out of the
difficulty by inventing a new entity, to which they gave the
name of soul, spirit or mind, and saying that it is this entity
which thinks.

Of course, by this facile method, there need never remain
any difficulty in any possible sphere of inquiry. All things
are susceptible of " explanation " by the invention of a
factitious entity of non-material qualities. Lamarck, how-
ever, knew too much to slide out of the idfficulty by such
discredited methods. Holding his views, it was inevitable
that one of his earliest psychological problems must have
been the old question : " Can matter think ?" He put it
squarely to himself, and decided that matter did not think ;
thought was only an " effect." Although probably the whole
subject remained rather vague in his mind, as it is in his
writings, he scarcely could have got farther in his time.

Lamarck's psychology is of the kind that is spoken of at
the present day as physiological psychology. He did not
indeed employ the experimental method introduced by Helni-
holtz, Fechner and Wundt ; but he based his psychology

PSYCHOLOGY Ixxvii

on such knowledge as he possessed of the physiology of the
nervous system. Doubtless that knowledge was scanty and
almost evanescent : even in our time physiology is only
just beginning to reach a development sufficient for the
foundation of a thoroughly scientific psychology. Lamarck
went far in the direction of materialism, though the
imperfect physiology of his day led him into a materialism
almost as crude as was the spiritualism of his day. He
denied the existence of the " peculiar entity called mind "
(esprit). " In this factitious entity," he continues, " which
is not like anything else in nature, I see a mere invention for
the purpose of resolving the difficulties that follow from
inadequate knowledge of the laws of nature." Mental mani-
festations are simply " effects " of cerebral processes, not
manifestations of a separate entity. He could hardly have
expressed it better. The whole of Lamarck's psychology is
thus reduced to an investigation of the physical or cerebral
processes which are correlated with mental processes.

So far, Lamarck's method is admirable. His classification
of the functions of the nervous system is also excellent : he
says there are four : (1) the production of muscular move-
ment, (2) of sensation, (3) of emotion, (4) of intellect ; a
classification which is obviously in close correspondence with
the modern tripartite division of mind. More especially is
he to be praised for the prominence which he gives to emo-
tion : — the importance of which has always been grotesquely
underestimated or altogether overlooked by the metaphysical
schools of psychology.

But, having said so much, I have said about all that can
be said for Lamarck's psychology. He wished to base his
psychology on the physiology of the nervous system : and
so far he was right. But his knowledge of that physiology
was worse than non-existent : his ideas on the subject were
extensively and radically erroneous ; the greater part of his
positive statements are altogether untrue.

Lamarck held that the nervous ^stem consisted of three
kinds of substance, the medullary pulp, the aponeurotic

Ixxviu INTRODUCTION

investment, and the nervous fluid. The medullary pulp cor-
responds to the grey and white matter of the brain and
spinal cord, and the nervous tissue generally ; all he says
says about it is that it consists of an " albumino-gelatinous "
substance. The aponeurotic investment is, I suppose, the
pia mater. But the entire body of Lamarck's psychology is
based on the assumption of the existence of the third kind
of substance, namely the nervous fluid, which, as I have
already said, was electric fluid supposed to become modified
and " animalised " on entering into the bodies of the higher
animals. The main result of this animalisation is apparently
that, instead of being uncontainable, and free to permeate
the whole of the animal's body, it becomes containable ;
that is to say, there are certain tissues that it cannot traverse,
and the most important of such tissues is the aponeurotic
investment in which the entire medullary pulp is enclosed.
It can, however, still move rapidly within the medullary
pulp itself, without needing any visible channels. The
nervous fluid is thus encased within the aponeurotic invest-
ment of the nervous system : it precisely corresponds to the
" animal spirits " of the ancients.

Lamarck held that in animals more primitive than insects
any nervous system which might exist had no other function
than that of exciting muscular movement. The system, he
imagined, then consisted of isolated ganglia, from which
nerves travelled to the muscles. He attributed the origin
of nerves to the expansive efforts of the nervous fluid within
the ganglia ; long nervous threads being thus thrust out by
the nervous fluid in its efforts to escape. In the insects
according to his view, the nervous system became sufliciently
integrated to endow the animal with feeling or sensation.
But it is not until we reach the lowest vertebrates, that is
to say, the fishes, that any kind of intellectual operation or
intelligent activity can be carried out. The existence of
sensation begins when the nervous system is united into one,
with a " main medullary mass " and a common nucleus
(foyer) for all the afferent nerves. The existence of intelli-

PSYCHOLOGY Ixxix

gence begins with the appearance of the cerebral hemispheres.
Lamarck cites direct introspection as evidence that thought,
etc., takes place in the anterior region of the hemispheres.

In dealing with the force in animals which confers upon
them the power of activity, Lamarck finds that it has two
distinct sources. In animals that have no nervous system,
the activating power is stated to be the subtle fluids of the
environment, notably caloric and electricity. These keep
the visible or " essential " fluids in motion, and entirely
dispense with any need for a nervous system to excite activity.
But Lamarck, influenced no doubt by Descartes, believed
that all such animals were pure machines, that had no feeling,
and were fatally driven by their environment into one or
other form of activity. They had no muscular system, but
only possessed irritability, aroused by contact with an external
object. As nervous and muscular systems were acquired,
however, the source of their motion gradually ceased ta
be the subtle fluids of the environment, and the nervous
fluid was substituted for them.

In this second form of activity, therefore, Lamarck speaks
of nature as having transferred the source of motion from
being outside the animal, to within it. He held that there
was a central " reservoir " of the nervous fluid ; and that
when any muscles were to be acted upon, the process con-
sisted in the simple despatch of nervous fluid from the
reservoir down the nerve which led to the muscle in question.
When the muscular contraction was no longer desired,
the nervous fluid returned to the reservoir by a natural
recoil.

Lamarck next had to consider by what physical processes
the reservoir could issue some of its fluid to the correct
muscles. He says it is by means of " emotions " : and that
the emotions again are due either to sensation or to thought,
to physical sensibility or to moral sensibility. We are thus
brought face to face with Lamarck's curious theory of the
physical aspects of sensation, emotion, and thought ; which
I shall now endeavour to indicate.

Ixxx INTRODUCTION

In addition to the reservoir of nervous fluid already men-
tioned, Lamarck imagined a nucleus {foyer) at which all the
afferent nerves meet. It is to be understood that he con-
sidered what we should now call the afferent and efferent
portions of the nervous system to be two entirely distinct
systems, though with a channel of communication for the
passage of nervous fluid between them. The efferent nerves
issued from their common reservoir ; the afferent nerves
terminated in a common nucleus, situated, he believed, in the
medulla oblongata. The relation between the nucleus and
the reservoir is nowhere definitely stated.

Lamarck's idea of sensation, then, was as follows : some
stimulus affects a nerve-ending in some part of the body ;
say the stimulus of contact by some foreign body. The
nervous fluid at the termination of the nerve affected is
immediately thrown into agitation ; and this agitation travels
up the nerve till it reaches the nucleus. Thereupon it is
propagated through the nucleus into every other sensitive
or afferent nerve in the body. The disturbance is carried
down all these nerves to their endings ; it then recoils and
returns along them till once more it arrives at the nucleus.
Hence there is a simultaneous reaction upon the nucleus by
all the afferent nerves, save that which brought in the original
agitation. This nerve alone remains passive, while the rest
are undergoing the action and reaction of the disturbance
which it aroused. Hence when the reaction reaches the
nucleus, and thus throws it for the second time into agitation,
the entire effect of that second agitation is concentrated on
the single nerve, which alone had not reacted because it
brought the original impression. The agitation now travels
back along that nerve to its ending, where the original
stimulus was applied. Hence the location of sensation at
the point of the body first stimulated : but such localisation
is regarded by Lamarck as an illusion, for sensation is a
general effect depending upon an agitation throughout every
portion of the sensitive system, and not upon processes
occurring in any single part of that system. It is worth

PSYCHOLOGY Ixxxi

noting that Lamarck presumed the quantity of sensation to
be proportional to the strength of the stimulus, and thus at
all events formulated one of the greatest problems of physio-
logical psychology in later times. It is now known that the
presumption is incorrect. It is more accurate to say that
the quantity of sensation is proportional to the logarithm of
the stimulus, but even this is only a very rough approxima-
tion, and the latest researches tend to limit more and more
the sphere of application of the law. When Lamarck speaks
of feeling, he means sensation, not emotion.

Coming now to emotions, Lamarck postulated for their
explanation the existence of an entity which he variously
calls the " feeling of existence," the " inner feeling," the
" moi " or ego. Even so close a student as Professor Packard
seems doubtful what Lamarck meant by this " feeling."
It is stated to be due to the summation of a large number of
indefinite sensations reaching the nucleus from all parts of
the body : the summation of these stimuli, individually
very weak, gives rise to an " inner feeling " of appreciable
magnitude. An emotion was understood by Lamarck to be
an affection or condition of this inner feeling, and he usually
speaks of it as an " emotion of the inner feeling."

I cannot resist from drawing attention once more to that
constantly alluring temptation to explain difficulties by the
manufacture of a psychical entity. Lamarck fails to under-
stand what an emotion is : he therefore invents an " inner
feeling " and affirms that emotion is a special state of this
entity. I am far indeed from wishing to raise the question
of the true existence of an " inner feeling," which has been
defended by William James and many other psychologists.
But unquestionably it has no such peculiar relation to the
emotions as that alleged by Lamarck, and for which purpose
he invented it. An emotion is not rendered more intelligible
by being regarded as a special state of some psychical entity.
The point is exactly analogous to the postulate of " mind "
as a special entity, in modern psychology. We are ac-
quainted with various mental processes, such as emotions.

Ixxxii INTRODUCTION

perceptions, reasoning, memory, will, etc. We cannot
straight away explain them ; and hence we immediately postu-
late an entity called " mind," of which they are special states.
To the physiologist, the additional entity merely cumbers
the ground : it explains nothing : it stands in the way of
true physiological explanations of those " mental pro-
cesses " : and, worst perhaps of all, it litters up the whole
subject with a false system of terminology. The very name
" mental process," which I am compelled to use, implies a
process of an entity called mind, whose existence I am
compelled to deny. When once false ideas become current
in any subject, the terminology of that subject becomes
correspondingly false. The false ideas become frozen into
a permanent language : and their displacement is far more
difficult than in a fluid condition.

The influence of language upon thought is largely, I should
suppose, in the direction which it inevitably gives to the
attention of the student. When he comes fresh to the new
subject, all is disorder and confusion. The terminology
comprises, however, a system of names which indicate or
should indicate the prominent and significant facts and
principles to be noted in reducing the subject to order. Now,
if that terminology is wrong, the whole subject will be
wrongly focussed : what should be prominent remains
unnoticed : what is really insignificant is held to be an
important foundation principle : the attention is wrongly
directed throughout.

These remarks apply with overwhelming force to psycho-
logy. Until recent times, the relative importance of different
sections of the subject were grossly misinterpreted. The
accents were all on the wrong parts. People gaped at the
problem of free-will and determinism : they thought it a
fundamental and genuine issue : they ranged themselves as
free-willists and necessitarians. In point of fact, the problem
is neither fundamental nor genuine : it does not even indicate
a true cleavage of opinion among philosophers. It is a
factitious paradox, as foolish as that of Achilles and the

PSYCHOLOGY Ixxxiii

tortoise. You can create difi&culties about almost anything,
even about a running man overtaking a tortoise. Such
difficulties are analogous to those mechanical puzzles, which
are often extremely difficult to make out, though based on
the most simple and elementary of principles : the main
law to be observed in making a puzzle (as also in conjuring)
is to draw attention q^ the significant feature, and, if
possible, to direct it on to insignificant features.

Now this is just precisely what has happened in psychology.
Attention is thrown on to the irrelevant, and withdrawn
from the relevant : and the language of centuries has securely
fixed the resulting false outlook. Hence we do not find, on
studying psychology, a set of simple laws and great principles
such as we meet with in physics and chemistry. We find a
collection of puzzles of the free-will type — which are only
puzzles because they so ingeniously draw attention from
every relevant feature in the discussion. And what should
be a mere psychological toy becomes the heading of an
important chapter of the science.

Modern psychologists have many such vexatious follies to
deal with. We have inherited a psychology that is sodden
with metaphysics, and perpetually haunted with unreal
entities. We have to discuss it in a terminology framed by
our opponents, and wholly unsuited to a true science. Let
us firmly assail the pestilential and slovenly habit of attri-
buting all things unknown to some psychical entity, invented
by ourselves for the occasion, or more usually inherited from
our savage ancestors. Lamarck offers us at any rate a
valuable object lesson. Convinced as he was of the fallacy
to which I have been alluding ; earnest as he was in his
attempt to avoid it ; he yet constantly fell into it. He
materialised a nervous fluid, with a reservoir, a nucleus, etc.
He materialised an " inner feeling " to explain emotions,
just as we materiahse a " mind " to explain the various
so-called mental processes. He materialised " nature " in
much the same way that Bergson does " time," as though
they were so many material things. Truly the materialism

Ixxxiv INTRODUCTION

of science is far from the grosser materialism of the common
behefs.

Lamarck believed that " emotions of the inner feehng "
might be aroused either through sensation or through thought.
The physical characteristic of an emotion aroused by sensa-
tion is simply an agitation or " emotion " of the nervous
fluid in the nucleus. An emotion differs from a sensation
in that it involves no reaction from other sensitive nerves.
The original agitation is conveyed to the nucleus by a single
nerve, as in a sensation ; and the commotion or emotion
there produced has no further active effect. If it acts on
any nerves, it is upon motor nerves which give rise to muscular
action. Every need (besoin) excites an emotion, either
through the medium of sensation or of thought. The
emotion, then acting upon the motor nerves, gives rise to
just those actions necessary for the satisfaction of the
need felt.

Lamarck explains habit by the tendency of the subtle
fluids constantly to traverse the same routes through the
organism. The first passage of the fluids facilitates sub-
sequent passages along the same channel, so that similar
actions tend to be repeated. He regarded instinct as originat-
ing in acquired habits. The habit once acquired would,
according to Lamarck, be inherited, and in course of
time become an instinct. In both these doctrines, he
anticipated two of the leading principles in Spencer's
Principles of Psychology. The idea of instinct as habit,
acquired and inherited, is indeed almost universally attri-
buted to Spencer. There is but little interest in determin-
ing the priority, however ; for the idea itself is certainly
erroneous.

Lamarck also based upon his nervous fluid a theory of
fatigue. The fluid, he says, is used up while functioning,
and has to be made good. Hence the necessity for rest
before further activities can be undertaken.

Lamarck regarded the will as an intellectual faculty,
though not in the first rank of importance. Here again he

PSYCHOLOGY Ixxxv

deserves great credit ; for throughout the history of philo-
sophy, almost up to modern times, the will has been accorded
an altogether undue prominence and significance. He placed
it approximately in its correct rank : he pointed out that
the extraordinary instincts of various insects has nothing
whatever to do with will or any conscious effort : he rightly
aflSrmed that conscious will has infinitely less to do with
initiating even human activities than it is supposed to
have. He denied the so-called free-will altogether, saying
that any volition flowed as necessarily from antecedent
conditions as the quotient in an arithmetical sum. In
all this he has been thoroughly justified by modern
knowledge.

Lamarck regarded the cerebral hemispheres, which he
called the hypocephalon, as the special intellectual organ,
and to a great extent cut off from the remainder of the
brain. He held that " ideas " were the material of every
kind of intellectual operation : and with that restless craving
for the manufacture of semi-material entities to explain away
difficulties, he affirmed that an idea was a tracing or engraving
actually impressed physically upon the soft substance of the
hemispheres. He recognised that the white matter of the
hemispheres is composed of nerve-fibres, which he imagined
to be hollow tubes containing the nervous fluid. He believed
that each fibre terminated in a minute cavity in the cortex,
too small to be visible. Now, when some impression is made
on our external senses, say the sight of a fish, the nervous
fluid contained in the optic nerve becomes agitated, as I
have already mentioned in describing Lamarck's views of
sensation. Now, Lamarck continues, if attention is turned to
the cause of tlie sensation, the sensation does not immediately
pass away, but, by a second reaction, subsequent to that
constituting the sensation, it reaches the brain, and there
becomes pigeon-holed as an idea. The agitation in the
original afferent nerve, in this case the optic nerve, passes
up to the cerebral cortex, and there (if I understand Lamarck
aright) engraves on the walls of the cavity at the end of the

Ixxxvi INTRODUCTION

nerve, an exact image of the fish which caused the sensation.
On this theory, therefore, the hemispheres become a vast
storehouse of miniature engravings, containing all the ideas
which the individual has ever formed.

Let not the reader too hastily deride this fantastic specula-
tion. Its difficulties, and indeed absurdities, are in our day
so obvious that it is hard to remember that they were
not always obvious. Nearly all Lamarck's errors may be
matched by similar errors current at the present day, and
not always confined to vulgar people. His present error is
no exception. It is not uncommon to hear people of passable
education exhibiting exactly the same ignorance as to the
relations of the physical and the psychical. An external
object, at which we look, forms an image on the retina :
and since the light has to pass through the lens, the image
is inverted. Now it is quite a common thing to hear people
wondering how the inverted image on the retina can give
rise to an optical sensation of the object as being right
way up. It is even said very often that we do see
the object upside down, and rectify it unconsciously and
automatically.

Now people who argue thus, or who see any unusual
difficulty in the matter, are in no better case than Lamarck
was a century ago, with his engravings in cavities of the
cerebral cortex. In each case, the psychical image is con-
fused with a physical image of the object : and whatever
the relation of psychical to physical may be, it is certainly
infinitely different from any such elementary analogy as
the above. Both illustrate that vicious tendency to hypo-
statisation, or manufacture of spiritual, material, or spirito-
material entities, which I have already so often endeavoured
to stigmatise.

Lamarck was a follower of Locke and the empirical school.
He believed that all ideas were acquired, and that there
were no such things as innate ideas. Since he traced all
intellect to ideas, and all ideas to sensations, he must be
reckoned as a sensationalist ; probably he was influenced by

PSYCHOLOGY Ixxxvii

Condillac. But he is careful to say that though every idea
is derived from a sensation, not every sensation yields an
idea. It is only when attention is fixed upon the sensation,
at the moment when it is experienced, that an idea of more or
less permanence remains.

On this theory of physically-existing ideas Lamarck bases
his whole theory of intellect. When the nervous fluid
traverses the outlines of an idea in the cortex, it is thrown
once more into the same type of agitation as when
it first engraved that idea. This agitation, being con-
veyed back to the nucleus of sensations, gives rise to a
fainter repetition of the original sensation : thus we have
memory.

When the nervous fluid passes over several graven ideas
at the same time, each portion of the fluid is agitated in a
mode corresponding to the idea traversed. When these
different streams of fluid, each with its special agitation or
mode of motion, reach the nucleus at the same moment,
their motions are compounded so as to form a " complex "
idea, which is then laid down in the cortex separately from
its constituents. Complex ideas may be further combined,
and thus Lamarck endeavours to give a physical interpreta-
tion of comparison and reasoning. Dreaming is accounted
for as an aberrant or haphazard wandering of the nervous
fluid, owing to failure of control by the " inner feeling."
Dehrium and syncope are similarly explained. But it is
needless to enter into further detail on Lamarck's psychology,
or to follow out all his apphcations of the general principles
cited above.

§ 9. Conclusion.

It is an unhappy but necessary characteristic of social
evolution that those great leaders of thought and action,
who at one time exercise profound influence over their
generation, are apt to be unduly criticised by those of
a succeeding generation. The works of great men are

Ixxxviii INTRODUCTION

commonly such as to arouse emotion, as often disagreeable
as agreeable. Their writings cannot be studied with indiffer-
ence : they do not leave us cold, as do the works of lesser
men. If we agree with them, we agree warmly ; if we
disagree with them, we are animated by a desire to attack
or abuse them.

The apphcation of this tendency to Lamarck is obvious.
He defended the doctrine of organic evolution at a time
when it was opposed not only to the entire authority of the
Church and people, but also to the judgment of the leading
men of science. For half a century his writings stood as
almost the only public representation of a beHef which
no one now questions. Then came the Origin of Species :
a work which naturally and immediately superseded every
earlier publication, a work moreover which perhaps aroused
more emotion than any other work of science ever published.
Almost inevitably, discipleship of Darwin engendered anta-
gonism to Lamarck. Once evolution became an accepted
fact, no one studied Lamarck to be convinced of it. His
arguments in favour of it ceased to excite interest : and
attention became concentrated on minor details as to the
process itself. Lamarck was at once seen to have offered
a very different account from that of Darwin, and the whole
energy of Darwinian discipleship was roused to antagonism
by the concentration of attention on the anti-Darwinian
elements of the older theory.

The scene has now changed once more : the reaction has
in various quarters turned against Darwin, while Lamarck
himself is slowly entering upon the final stage of oblivion.
The time is ripe for appreciating his true position in the
history of knowledge.

As a philosopher, he was decidedly of the second rank.
He appears to have been an agnostic by reason, and a deist
by desire. " Since I can have no positive knowledge on
this subject," he writes, " I prefer to think that the whole
of nature is only an effect : hence I imagine and like to
believe in a first cause or in short a supreme power which

CONCLUSION Ixxxix

brought nature into existence and made it such as it is."
He regarded the universe as having some goal or purpose,
known only to its sublime author. His philosophy throughout
is far inferior to that of many of his elder contemporaries;
such as Diderot or d'Holbach.

As a pure zoologist, he has not the reputation of
Cuvier. At the same time his judgment and method were
of a very high order, as shown by the groups estabHshed
by him and still recognised at the present day ; e.g.
Annelids, Arachnids, Myriapods, Vertebrates. We must,
remember that he upheld against overwhelming odds the
banner of organic evolution. There can be no justifica-
tion for the contempt with which many people now
speak of Lamarck, merely because his idea of the
evolutionary process differed from ours. So great a truth
can only be discovered by the efforts of several genera-
tions. While therefore he was not a first-class philosopher
or perhaps zoologist, yet he derived a certain advantage
and width of view from the combination of these two
interests. He was able to draw his conclusions from a
wider basis than would have been possible to a more limited
specialism.

I am aware that there are many who repudiate all sug-
gestion of a philosophical treatment of scientific problems.
Such a view cannot for a moment be defended. It arises
from the fact that the name philosophy is so often used
as synonymous with metaphysics : and that the most in-
accessible problems of science have been so often treated to
bushels of high-sounding words from which no genuine
solutions can issue. Yet it remains indisputable that only
by a large knowledge of general principles, as well as of
details, can any true progress result. A man may be in-
timately versed in the anatomy, physiology, classification
and distribution of earwigs, and yet be entirely destitute
of biological judgment : just as a mechanic may know the
minutest details of his machine, and yet be wholly unable
to improve it ; while the engineer who has never seen it

xc INTRODUCTION

before, but is guided by the general laws and principles
of mechanics, will quickly succeed in raising its efficiency.
So it is in science : a knowledge of the great general
principles confers a judgment and grasp of essentials, which
is denied to the mere scientific artisan.

In the foregoing pages I have endeavoured to draw certain
rules of scientific method from an analysis of the causes of
the errors into which Lamarck fell. These rules are neither
new nor startling ; yet their importance is so great as to bear
almost endless repetition.

The first principle is one which has never ceased to be
preached since the time of Bacon : it emphasises the truth
that the methods of science are those of observation and
experiment : and that as soon as we travel outside these
methods, we become involved in hopeless error and confusion.
The second follows from the first : it enjoins upon us the
principle, never to seek the explanation of some difficult
problem by the manufacture of a new and unknown
entity. In every case where Lamarck abandoned this rule
he came to grief. I do not mean that we should only believe
in the existence of what we can see or feel ; I mean that
when we form some hypothesis to explain a process or event,
and when that hypothesis involves us in the assumption of
some existence not appreciable to our senses, that existence
must be invested with similar properties to those possessed
by other existences which are appreciable to our senses.
That is to say, it must either have the properties of matter,
or of material force or energy : and therefore must be
capable, theoretically at least, of being some day removed
from the sphere of hypothesis to that of observation. To
this rule there has never been any exception in the history
of science. Wherever any suggested hypothesis has included
any factor of a difi'erent order from those known to us by
observation and experiment, that hypothesis has ultimately
decayed or been refuted. The unbroken record of history
suffices in itself to establish this general philosophic law,
which indeed is thrust upon us with equal force from many

CONCLUSION xci

other sides. Yet it is disregarded every day, even by men
of science ; and science suffers in consequence. How then
can it be denied that some knowledge of the philosophy
of science is essential to true advance and to sound
judgment ?

Undoubtedly, however, too much stress on the philosophy
or general principles is no less dangerous than too much
application to the details. The former error leads to pre-
mature generalisations and excessive deduction : the latter
to a heavy weight of meaningless and undigested facts, not
qualitatively different from the crammed learning of a well-
flogged schoolboy. The unfortunate truth remains that either
of these subjects — an apprehension of the essential prin-
ciples on the one hand, and a mastery over the facts on the
other hand — is in itself a sufficient task for any ordinary
man. They cannot be fruitfully combined, except by a
fine genius, and then only with a life of hard and unremitting
toil. Whatever we may think as to the former, there is no
doubt that Lamarck abundantly satisfied the latter condi-
tion. He never exploited science for his own advantage.
At all times there are many who follow science with the
view of gaining from it money or honour : there are others,
who have derived from nature a curious and inquiring mind,
and who are wholly bound up with the desire to discover
new truth, and to know new things, merely and solely for
the interest of them. Such a one was Lamarck : he
fulfilled the true function of the philosopher by wandering
over all the sciences and prying into every corner of nature,
with the hope of grasping certain general principles or out-
lines of natural laws. He fulfilled the true function of the
man of science by an intimate and minute study of the
details known in a single part of the sphere of possible know-
ledge. Whether his powers were equal to so vast and uni-
versal an inquiry is a question that may properly be asked :
at any rate, he gave to the work all that any man can give :
he shattered his health, lost his eyesight, and abandoned
his reputation in his immovable resolve to find the truth.

xcii INTRODUCTION

Had he been a soldier, and suffered thus for the sake of his
country, how great would have been the honour that would
have rewarded so deep a devotion ! But he was the soldier
of no country : he was the soldier of humanity and truth
alone. To my pen falls the lot of vindicating the memory
of one who, if he had laboured to destroy his fellow-men
instead of to enlighten them, would have received all the
glories of a national hero.

H. E.

PREFACE.

Experience in teaching has made me feel how useful a philosophical
zoology would be at the present tiriie. By this I mean a body of
rules and principles, relative to the study of animals, and applicable
even to the other divisions of the natural sciences ; for our know-
ledge of zoological facts has made considerable progress during the
last thirty years.

I have in consequence endeavoured to sketch such a philosophy
for use in my lessons, and to help me in teaching my pupils ; nor had
I any other aim in view. But in order to fix the principles and
establish rules for guidance in study, I found myself compelled to
consider the organisation of the various known animals, to pay attention
to the singular différences which it presents in those of each family,
each order, and especially each class ; to compare the faculties which
these animals derive according to its degree of complexity in each
race, and finally to investigate the most general phenomena presented
in the principal cases. I was therefore led to embark upon successive
inquiries of the greatest interest to science, and to examine the most
difficult of zoological questions.

How, indeed, could I understand that singular degradation which
is found in the organisation of animals as we pass along the series
of them from the most perfect to the most imperfect, without en
quiring as to the bearings of so positive and so remarkable a fact,
founded upon the most convincing proofs ? How could I avoid
the conclusion that nature had successively produced the different
bodies endowed with life, from the simplest worm upwards ? For
in ascending the animal scale, starting from the most imperfect animals,
organisation gradually increases in complexity in an extremely remark-
able manner.

I was greatly strengthened in this behef, moreover, when I recognised
that in the simplest of all organisations there were no special organs
whatever, and that the body had no special faculty but only those
which are the property of all living things. As nature successively

2 ZOOLOGICAL PHILOSOPHY

creates the different special organs, and thus builds up the animal
organisation, special functions arise to a corresponding degree, and
in the most perfect animals these are numerous and highly developed.

These reflections, which I was bound to take into consideration,
led me further to enquire as to what life really consists of, and what
are the conditions necessary for the production of this natural pheno-
menon and its power of dwelling in a body. I made the less resistance
to the temptation to enter upon this research, in that I was then con-
vinced that it was only in the simplest of all organisations that the
solution of this apparently difficult problem was to be found. For
it is only the simplest organisation that presents all the conditions
necessary to the existence of life and nothing else beyond, which might
mislead the enquirer.

The conditions necessary to the existence of life are all present
in the lowest organisations, and they are here also reduced to their
simplest expression. It became therefore of importance to know
how this organisation, by some sort of change, had succeeded in giving
rise to others less simple, and indeed to the gradually increasing com-
plexity observed throughout the animal scale. By means of the two
following principles, to which observation had led me, I beUeved I
perceived the solution of the problem at issue.

Firstly, a number of known facts proves that the continued use of
any organ leads to its development, strengthens it and even enlarges
it, while permanent disuse of any organ is injurious to its develop-
ment, causes it to deteriorate and ultimately disappear if the disuse
continues for a long period through successive generations. Hence
we may infer that when some change in the environment leads to a
change of habit in some race of animals, the organs that are less used
die away little by little, while those which are more used develop
better, and acquire a vigour and size proportional to their use.

Secondly, when reflecting upon the power of the movement of the
fluids in the very supple parts which contain them, I soon became
convinced that, according as this movement is accelerated, the fluids
modify the cellular tissue in which they move, open passages in them,
form various canals, and finally create different organs, according
to the state of the organisation in which they are placed.

Arguing from these two principles, I looked upon it as certain
that, firstly, the movement of the fluids within animals — a move-
ment which is progressively accelerated with the increasing complexity
of the organisation — and. secondly, the influence of the environment,
in so far as animals are exposed to it in spreading throughout all
habitable places, were the two general causes which have brought
the various animals to the state in which we now see them.

PREFACE 3

I have not merely confined myself in the present work to setting
forth the conditions essential to the existence of life in the simplest
organisations, and the causes which have given rise to the growing
complexity of animal organisation from the most imperfect to the most
perfect of animals ; but, believing that there is some possibility of
recognising the physical causes of feeUng, which is possessed by so
many animals, I have not hesitated to take up this question also.

I was indeed convinced that matter can never possess in itself
the property of feeling ; and I imagined that feehng itself is only a
phenomenon resulting from the workings of an orderly system capable
of producing it. I enquired therefore what the organic mechanism
might be which could give rise to this wonderful phenomenon, and I
believe I have discovered it.

On marshalling together the best observations on this subject, I
recognised that for the production of feeling the nervous system
must be highly complex, though not so highly as for the phenomena
of intelUgence.

Following out these observations, I have become convinced that
the nervous system, when it is in the extremely imperfect condition
characteristic of more or less primitive animals, is only adapted to
the excitation of muscular movements, and that it cannot at this
stage produce feehng. In this particular stage it consists merely of
ganglia, from which issue threads. It does not present any gang-
lionic longitudinal cord, nor any spinal cord, the anterior extremity
of which expands into a brain which contains the nucleus of sensations
and gives origin to the nerves of the special senses, or at least to some
of them. When the nervous system reaches this stage, the animals
possessing it then have the faculty of feeling.

Finally, I endeavoured to determine the mechanism by which
a sensation was achieved ; and I have shown that nothing more
than a perception can be produced in an individual which has no
special organs, and moreover, that a sensation produces nothing
more than a perception whenever it is not specially remarked.

I am in truth undecided as to whether sensation is achieved by a
transmission of the nervous fluid starting from the point affected,
or merely by a communication of movement in that fluid. The fact,
however, that the duration of certain sensations is dependent upon
that of the impressions which cause them, make me lean towards
the latter opinion. My observations would not have thrown any
satisfactory light upon the subjects treated, if I had not recognised
and been able to prove that feeling and irritabiUty are two very different
organic phenomena. They have by no means a common origin, as
has been supposed ; the former of these phenomena constitutes a

4 ZOOLOGICAL PHILOSOPHY

faculty peculiar to certain animals, and demanding a special system
of organs, while the latter, which does not require any special system,
is exclusively the property of all animal organisation.

So long therefore as these two phenomena continue to be confused
as to their origin and results, it will be only too easy to make mistakes
in proffering explanations of the causes of the general phenomena
of animal organisation. It will be so especially in making experiments
for the purpose of investigating the principle of feeling and of move-
ment, and finally the seat of that principle in the animals which possess
these faculties.

For instance, if we decapitate certain very young animals, or cut
the spinal cord between the occiput and the first vertebra, or push
in a probe, there occur various movements excited by the pumping
of air into the lungs. These have been taken as proof of the revival
of feehng by dint of artificial respiration ; whereas these effects
are due partly to the irritabihty not being extinct, for it is known that
it continues to exist sometime after the death of the individual, and
partly to certain muscular movements which can still be excited
by the inhalation of air when the spinal cord has not been altogether
destroyed by the introduction of a long probe right down its
canal.

I recognised that the organic act which gives rise to the movement
of the parts is altogether independent of that which produces feeling,
although in both cases nervous influence is necessary. I notice
that I can work several of my muscles without experiencing any
sensation, and that I can receive a sensation without any movement
resulting from it. But for these observations, I too might have taken
the movements occurring in a young decapitated animal, or in one whose
brain had been removed, as signs of feehng, and I should have fallen
into error.

I think that if the individual is disabled by its nature or otherwise
from giving an account of a sensation which it experiences, and that
if it only indicates by cries the pain which it is made to undergo,
we have no certain sign for inferring that it receives sensation except
from knowing that the system. of organs which gives it the faculty
of feeling is not destroyed, but retains its integrity. Muscular move-
ments excited from without cannot in themselves prove an act
of feeling.

Having fixed my ideas on these interesting objects, I gave attention
to the inner feeling, that is to say, that feehng of existence which is
possessed only by animals which enjoy the faculty of feeling. I
brought to bear on the problem such known facts as are relevant, in
addition to my own observations, and I soon became convinced

PREFACE 5

that this inner feeling constituted a power which it was essential to
take into consideration.

Nothing in fact seems to me so important as the feeling which I
have named, considered both in man and in the animals which possess
a nervous system capable of producing it. It is a feeUng which can
be aroused by physical and moral needs, and which becomes the source
whence movements and actions derive their means of execution.
No one that I know had paid any attention to it ; and this gap in our
knowledge of one of the most powerful causes of the principal pheno-
mena of animal organisation rendered all explanations inadequate
to account for these phenomena. We have, however, a sort of clue
to the existence of that inner power when we speak of the agitations
which we ourselves are constantly experiencing ; for the word emotion,
which I did not create, is often enough pronounced in conversation
to express the observed facts.

When I had considered that the inner feeling was susceptible of
being arou,sed by different causes, and that it then constituted a
power capable of exciting actions, I was so to speak struck by the
multitude of known facts which attest the actual existence of that
power ; the difficulties which had long puzzled me with regard to the
exciting cause of actions appeared to me entirely surmounted.

Admitting that I had been fortunate enough to aUght upon a
truth in attributing to the inner feeling of animals which have it the
power which produces their movements, I had still only surmounted
a part of the difficulties by which this research is hampered. For
it is obvious that not all known animals do or can possess a nervous
system ; consequently, all animals do not possess the inner feeling
of which I am speaking ; and in the case of those which are destitute
of it, the movements which they are seen to execute must have another
origin.

I had reached this point when I reflected that without internal
excitations plant life would not exist at all, nor be able to maintain
itself in activity. I recognised the fact that the same consideration
appUed to a large number of animals ; and as I had very frequently
observed that nature varies her means when necessary in order to
attain the same end, I had no further doubt about the matter.

I think therefore that the very imperfect animals which have no
nervous system live only by the help of excitations which they receive
from the exterior. That is to say, subtle and ever moving fluids
contained in the environment incessantly penetrate these organised
bodies and maintain life in them, so long as the state of these bodies
permits of it. Now this thought is one which I have many times
considered, which many facts appear to me to confirm, against which

6 ZOOLOGICAL PHILOSOPHY

none of those that are known to me seem to conflict, and finally which
appears to me obviously borne out by plant life. It was therefore
for me a flood of light which disclosed to me the principal cause which
maintains movements and the life of organised bodies, and to which
animals owe all that animates them.

I combined this consideration with the two preceding ones, namely,
that which concerns the result of the movement of fluids in the interior
of animals and that which deals with the effects of a change that is
maintained in the environment and habits of these beings. I could
thus seize the thread which connects the numerous causes of the
phenomena presented in animal organisation, and I soon perceived
the importance of this power in nature which preserves in new in-
dividuals all the changes in organisation acquired by their ancestors
as a result of their life and environment.

Now I remarked that the movements of animals are never directly
communicated, but that they are always excited ; hence I recognised
that nature, although obliged at first to borrow from the environ-
ment the excitatory power for vital movements and the actions of
imperfect animals, was able by a further elaboration of the animal
organisation to convey that power right into the interior of these
beings, and that finally she reached the point of placing that same
power at the disposal of the individual.

Such are the principal conclusions which I have endeavoured to
establish and develop in this work.

This Zoological Philosophy thus sets forth the results of my studies
on animals, their characters both general and special, their organisa-
tion, the causes of their development and diversity, and the faculties
which they thence derive. In its composition I have made use of
the bulk of the material which I was collecting for a projected work
on living bodies under the title of Biology. This work will now remain,
so far as I am concerned, unwritten.

The facts which I name are very numerous and definite, and the
inferences which I have drawn from them appeared to me sound
and necessary ; I am convinced therefore that it will be found difficult
to replace them by any others.

The number of new theories expounded in the present work are
likely to give the reader an unfavourable impression, if only from
the fact that the commonly received beliefs do not readily give
way to any new ones which tend to contradict them. Now, since
the predominance of old ideas over new favour this prejudice,
especially when there is some contributory personal interest, it follows
that, whatever difficulties there may be in the discovery of new truths
in nature, there are still greater difficulties in getting them recognised.

PREFACE 7

But these difficulties, arising from various causes, are on the whole
more advantageous than otherwise to the general progress of know-
ledge. By means of a rigorous hostility to the admission of new
ideas as truths, a multitude of more or less specious but unfounded
ideas which appear, soon after fall into oblivion. Sometimes, on
the other hand, excellent opinions and solid thoughts are for the same
reasons discarded or neglected ; but it is better that a truth once
perceived should have a long struggle before obtaining the attention
it deserves, than that all that is produced by the ardent imagination
of man should be too readily received.

The more I meditate on this subject, and particularly on the numerous
causes which may bring about a change in our opinions, the more am
I convinced, that except for the physical and moral facts ^ that no
one can question, all else is but opinion or argument ; and we well
know that arguments can always be met by others. Thus, although
it is obvious that there are great differences in the probability and
even the value of the opinions of different men, it seems to me that
we should be wrong to blame those who refuse to adopt our own.

Should we recognise as well founded only those opinions that are
most widely accepted ? Experience shows clearly enough that
persons with the most developed intellect and the highest wisdom
constitute at all times an extremely small minority. The fact can
scarcely be questioned. Authorities in the sphere of knowledge
should weigh one another's worth and not count one another's numbers,
although indeed a true estimation is very difficult.

Seeing how numerous and rigorous are the conditions required
for forming a sound judgment, it is still uncertain whether the judg-
ment of individuals who have been set up as authorities by public
opinion is perfectly sound on the topics on which they pronounce.

There are then few positive truths on which mankind can firmly
rely. They include the facts which he can observe, and not the in-
ferences that he draws from them ; they include the existence of nature,
which presents him with these facts, as also the laws which regulate
the movements and changes of its parts. Beyond that all is un-
certain, although some conclusions, theories, opinions, etc., have much
greater probabihty than others.

We cannot rely on any argument, inference or theory, since the
authors of these intellectual acts can never be certain that they have
taken into account the true data, nor that they have admitted these

* By moral facts I mean mathematical truths ; that is to say, the results of
calculations whether of quantities or forces, and the results of measurements ; since
it is through intelligence and not through the senses that these facts become known
to us. Now these morai facts are just as much positive truths as are those relating
to the existence of bodies that we can observe.

8 ZOOLOGICAL PHILOSOPHY

only. There is nothing that we can be positive about, except the
existence of bodies which affect our senses, and of the real qualities
which belong to them, and finally the physical and moral facts of
which we are able to acquire a knowledge. The thoughts, argu-
ments and explanations set forth in the present work should therefore
be looked upon merely as opinions which I propose, with the intention
of setting forth what appears to me to be true, and what may indeed
actually be true.

However this may be, in giving myself up to the observations
from which my theories have arisen, I have obtained the pleasure
which their resemblance to truth has brought me, and I have obtained
also the recompense for the fatigues entailed upon me by my studies
and meditations. In publishing these observations, together with
the conclusions that I have drawn from them, my purpose is to invite
enlightened men who love the study of nature to follow them out,
verify them, and draw from them on their side whatever conclusions
they think justified.

This path appears to me the only one that can lead to a knowledge
of truth or of what comes nearest it, and it is clear that such know-
ledge is more profitable to us than the error which might fill its place.
I cannot doubt therefore that it is this path which we must follow.

It may be noticed that I have dwelt with special pleasure on the
exposition of the second and especially of the third part of this work,
and that I have been greatly interested in them. None the less,
the principles bearing on natural history which I have studied in
the first part should be looked upon as possibly the most useful to
science, since they are in general most in harmony with the opinions
hitherto received.

I might have considerably extended this work by developing under
each heading all the interesting matter that it permits of ; but I
have preferred to confine myself to such exposition as is strictly
necessary for the adequate comprehension of my observations. I
have thus spared my readers' time without exposing them to the
risk of failing to understand me.

I shall have attained my end if those who love natural science
find in this work any views and" principles that are useful to them ;
if the observations which I have set forth, and which are my own,
are confirmed or approved by those who have had occasion to study
the same objects ; and if the ideas which they succeed in giving
rise to, whatever they may be, advance our knowledge or set us on
the way to reach unknown truths.

PRELIMINARY DISCOURSE.

To observe nature, to study her productions in their general and
special relationships, and finally to endeavour to grasp the order
which she everywhere introduces, as well as her progress, her laws,
and the infinitely varied means which she uses to give effect to that
order : these are in my opinion the methods of acquiring the only
positive knowledge that is open to us, — the only knowledge moreover
which can be really useful to us. It is at the same time a means to
the most deUghtful pleasures, and eminently suitable to indemnify
us for the inevitable pains of life.

And in the observation of nature what can be more interesting
than the study of animals ? There is the question of the affinities
of their organisation with that of man, there is the question of the
power possessed by their habits, modes of life, climates and places
of habitation, to modify their organs, functions and characters. There
is the examination of the different systems of organisation which are
to be observed among them, and which guide us in the determina-
tion of the greater or lesser relationships that fix the place of each
in the scheme of nature. There is finally the general classification
that we make of these animals from considerations of the greater
or lesser complexity of their organisation ; and this classification
may even lead us to a knowledge of the order followed by nature in
bringing the various species into existence.

Assuredly however, it cannot be disputed that all these enquiries,
and others also to which the study of animals necessarily leads, are
of very great interest to anyone who loves nature and seeks the
truth in all things.

It is a pecuUar circumstance that the most important phenomena
for us to consider have only been available since the time when
attention was devoted to the study of the least perfect animals, and
since the researches on the various complications in the organisation
of these animals became the main object of study.

It is no less curious that the most important discoveries of the

10 ZOOLOGICAL PHILOSOPHY

laws, methods and progress of nature have nearly always sprung from
the examination of the smallest objects which she contains, and from
apparently the most insignificant enquiries. This truth, already
established by many remarkable facts, will receive in the course of this
work a new accession of evidence, and should convince us more than
ever that in the study of nature no object whatever can be dis-
regarded.

The purpose of the study of animals is not merely to ascertain their
different races, nor to determine all the distinctions among them by
specifying their special characters. This study further aims at
acquiring a knowledge of the functions which animals possess, the
causes of the presence and maintenance of life in them, and of the
remarkable progression which they exhibit in the complexity of their
organisation, as well as in the number and development of their
functions.

At bottom, the 'physical and moral are without doubt one and the
same thing. It is by a study of the organisation of the different orders
of known animals that this truth can be set in the strongest light. Now
since these products from a common origin, at first hardly separated,
become eventually divided into two entirely distinct orders, these
two orders when examined at their greatest divergence have seemed
to us and still seem to many persons to have nothing in common.

The influence of the physical on the moral has however already
been recognised,^ but it seems to me that sufficient attention has not
yet been given to the influence of the moral on the physical. Now
these two orders of things which have a common origin re-act upon
one another, especially when they appear the most widely separated ;
and we are now in a position to prove that each affects the variations
of the other.

It seems to me that we have gone the wrong way to work in the en-
deavour to show the common origin of the two orders of results which,
in their highest divergence, constitute what is called the 'physical
and the moral.

For the study of these two kinds of objects, apparently so distinct,
has been initiated in man himself. Now his organisation, having
reached the limit of complexity and perfection, exhibits the greatest
complication in the causes of the phenomena of life, feeUng and
function. It is consequently the most difiicult from which to infer
the origin of so many phenomena.

After the organisation of man had been so well studied, as was the
case, it was a mistake to examine that organisation for the purposes of

* See the interesting work of M. Cabania entitled Rapport du physique et du
moral de V homme.

PRELIMINARY DISCOURSE II

an enquiry into the causes of life, of physical and moral sensitiveness,
and, in short, of the lofty functions which he possesses. It was first
necessary to try to acquire knowledge of the organisation of the other
animals. It was necessary to consider the differences which exist
among them in this respect, as well as the relationships which are
found between their special functions and the organisation with which
they are endowed.

These different objects should have been compared with one another
and with what is known of man. An examination should have been
made of the progression which is disclosed in the complexity of organisa-
tion from the simplest animal up to man, where it is the most complex
and perfect. The progression should also have been noted in the
successive acquisition of the different special organs, and consequently
of as many new functions as of new organs obtained. It might then
have been perceived how needs, at first absent and afterwards gradually
increasing in number, have brought about an incUnation towards
the actions appropriate to their satisfaction ; how actions becoming
habitual and energetic have occasioned the development of the organs
which execute them ; how the force which stimulates organic move-
ments can in the most imperfect animals exist outside of them and
yet animate them ; how that force has been subsequently transported
and fixed in the animal itself ; and, finally, how it has become the source
of sensibihty, and last of all of acts of intelUgence.

I may add that if this method had been followed, feeling would
certainly not have been looked upon as the general and immediate
cause of organic movements. It would never have been said that
life is a consequence of movements executed by virtue of sensations
received by various organs or otherwise ; nor that all vital move-
ments are brought about by impressions received by sensitive parts
{Rapport du physique et du moral de Vhomme, pp. 38 to 39, and 85).

This cause would appear to be justified up to a certain point in the
most perfect animals, but if it held good with regard to all bodies
which enjoy life, they would all possess the faculty of feeUng. Now
it could hardly be shown that this is the case in plants ; it could hardly
even be proved that it is the case in all known animals.

The supposition of such a general cause does not seem to me justified
by the real methods of nature. When constituting life, she had no
power to endow with that faculty the imperfect animals of the earlier
classes of the animal kingdom.

With regard to living bodies, it is no longer possible to doubt that
nature has done everything little by little and successively.

Hence, among the various subjects which I intend to discuss in
the present work, I shall endeavour to make clear by the citation

12 ZOOLOGICAL PHILOSOPHY

of recognised facts that nature, while ever increasing the complexity
of animal organisation, has created in order the different special organs,
as also the fimctions which the animals possess.

The behef has long been held that there exists a sort of scale or
graduated chain among living bodies. Bonnet has developed this-
view ; but he did not prove it by facts derived from their organisa-
tion ; yet this was necessary especially with regard to animals. He
was unable to prove it, since at the time when he Uved the means did
not exist.

In the study of all classes of animals there are many other things
to be seen besides the animal complexity. Among the subjects of
greatest importance in framing a rational philosophy are the effect
of the environment in the creation of new needs ; the effect of the needs
in giving rise to actions, and of repeated actions in creating habits,
and incUnations ; the results of increased or diminished use of any
organ, and the means adopted by nature to maintain and to perfect
all that has been acquired in organisation.

But this study of animals, especially of the least perfect animals,
was long neglected ; since no suspicion existed of the great interest
which they exhibit. Moreover, what has been started in this respect
is still so new that we may anticipate much more light from its further
development.

When the study of natural history was actually begun, and
naturalists inquired into both kingdoms, those who devoted their
researches to the animal kingdom studied chiefly the vertebrate animals,
that is to say mammals, birds, reptiles and, lastly, fishes. In these
classes of animals the species are in general larger, and have their
parts and functions better developed and more easily ascertainable
than the species of invertebrate animals. Their study, therefore,
seemed to present more of interest.

In fact the majority of invertebrate animals are extremely small,
their functions are Umited, and their organs much more remote from
those of man than is the case of the more perfect animals. As a
result, they have been to some extent despised by the vulgar, and
down to our own time have only reahsed a very moderate amount
of interest on the part of most naturalists.

We are beginning, however, to get over a prejudice so harmful to
the progress of knowledge. During the few years that these singular
animals have been closely examined, we have been compelled to
recognise that the study of them is highly interesting to the naturalist
and philosopher, because it sheds light, that could scarcely be other-
wise obtained, on a number of problems in natural history and animal
physics. It has been my duty in the Natural History Museum to

PRELIMINARY DISCOURSE 13

attend to the exhibit of the animals which I called invertebrate,
on account of the absence in them of a vertebral column. My re-
searches on these numerous animals, the accumulated observations
and facts, and finally the increased knowledge of comparative anatomy
which I gained from them, soon inspired me with the highest interest
in the subject.

The study of invertebrate animals must, in fact, be of special interest
to the naturalist for four reasons : — (1) The number of the species
of these animals in nature is much greater than that of vertebrate
animals. (2) Since they are more numerous, they are necessarily
more varied. (3) The variations in their organisation are much
greater, more sharply defined and more remarkable. (4) The order
observed by nature in the successive formation of the different organs
of animals is much better expressed in the mutations which these
organs undergo in invertebrate animals. Moreover, their study is
more fertile in helping us to understand the origin of organisa-
tion, with its complexity and its developments, than could possibly
be the case in more perfect animals such as vertebrates.

Convinced of these truths I felt that, in the instruction of my
pupils, I should not plunge into detail straight away, but should
above all show them the general principles which hold good of all
animals. I tried to give them a view of the whole and of the essentials
which appertained to it, with the intention of taking subsequent
note of the main groups into which that whole appears to be divided
for purposes of comparison and more intimate knowledge.

The real way, no doubt, of acquiring a thorough knowledge of an
object, even in its smallest details, is to begin by inspecting it in its
entirety. We should examine first its bulk, extent, and the various
parts which compose it. We should enquire into its nature and
origin, and its connection with other known objects. In short, we
should enquire into the general principles involved, from all possible
points of view. The subject is then divided into its chief parts for
separate study and examination in all the bearings likely to be in-
structive. By further dividing and sub-dividing these parts, and
inspecting each successively, we arrive at the smallest, where we do
not neglect the least details. Once these re-searches finished, the effects
have to be deduced from them, so that little by little the philosophy
of science is established, modified and perfected.

It is by this method alone that human intelligence can gain know-
ledge (in any science) that is at once vast, solid and coherent. It
is solely by this kind of analysis that science makes real progress,
so that aUied objects are never confused, but can be perfectly
known.

14 ZOOLOGICAL PHILOSOPHY

Unfortunately this method is not sufficiently used in the study
of natural history. The recognised necessity for close observation
of special objects has produced a habit of not going beyond these
objects with their smallest details. They have thus become for most
naturaUsts the chief subjects of study. This would, however, not
really be a drawback for natural science, were it not for the steady
refusal to see in the observed objects anything besides their form,
dimensions, external parts, colour, etc., but those who give themselves
up to such a study are contemptuous of the higher ideals, such as the
enquiry into the nature of the objects which occupy them, into the
causes of the modifications or variations which these objects undergo,
and into the relations of these same objects with each other and with
all other known objects, etc., etc.

It is because the method which I have just named is insufficiently
followed out that we find so much divergence in what is taught on
this subject, both in works on natural history and elsewhere. Those
who have gone in exclusively for the study of species find it very
difficult to grasp the general affinities among objects ; they do not
in the least appreciate nature's true plan, and they perceive hardly
any of her laws.

I am convinced that it is wrong to follow a method which so greatly
limits ideas. I find myself on the other hand obliged to bring out
a new edition of my Système des animaux sans vertèbres, since the
rapid progress of comparative anatomy and the new discoveries of
zoologists, together with my own observations, enable me to improve
that work. I have accordingly collected into a special work, under
the title of Zoological Philosophy, (1) the general principles at stake
in the study of the animal kingdom ; (2) the observed facts which
require to be considered in that study ; (3) the principles which
regulate the most suitable classification of animals, and an arrange-
ment of them in their natural order ; (4) lastly, the most important of
the results which flow naturally from the accumulated observations
and facts, and which constitute the true foundation of the philosophy
of science.

The Zoological Philosophy is nothing but a new edition, re-cast,
corrected and much enlarged, of my work entitled Recherches sur
les corps vivants. It is divided into three main divisions, and each
of these divisions is broken up into separate chapters.

Thus, in the first division, which sets forth the essential observed
facts and the general principles of the natural sciences, I shall begin
by a discussion of what I call artificial devices used among the sciences
in question. I shall deal with the importance of the consideration
of affinities, and with the notion that should be conveyed, when

PRELIMINARY DISCOURSE 15

we speak of species among living bodies. Afterwards, when I have
treated of the general principles which concern animals, I shall adduce
proof of the degradation of organisation which runs through the entire
animal scale, placing the most perfect animals at the anterior extremity
of that scale. On the other hand I shall show the influence of en-
vironment and habit on the organs of animals, as being the factors
which favour or arrest their development. I shall conclude this
division by a discussion of the natural order of animals, and by an
account of their most suitable arrangement and classification.

In the second division I shall put forward my ideas as to the order
and state of things which constitute the essence of animal Ufe ; and I
shall indicate the conditions necessary for the existence of this wonder-
ful natural phenomenon. Afterwards, I shall endeavour to ascertain
the exciting cause of organic movements ; of orgasm and of irrita-
bihty ; the properties of cellular tissue ; the sole condition under
which spontaneous generation can occur ; the obvious effects of vital
actions, etc.

Lastlv. the third division will state my opinion as to the physical
causes of feehng, of the power to act, and of the acts of the intelligence
found in certain animals.

In this di\àsion I shall treat : 1st, the origin and formation of the
nervous system ; 2nd, the nervous fluid, which can only be known
indirectlv, but whose existence is attested by phenomena that it
alone can produce ; 3rd, physical sensibility and the mechanism
of sensations ; 4th, the reproductive power of animals ; 5th, the
origin of the will and the faculty of wilUng ; 6th, ideas and the different
kinds of them ; 7th, lastly, certain peculiar acts of the understanding,
such as attention, thoughts, imagination, memory, etc.

The reflections set forth in the 2nd and 3rd divisions doubtless
comprise subjects that are very difficult to examine, and may
even appear insoluble ; but they are so full of interest that such
attempts may possibly be profitable, either in the disclosure of un-
perceived truths or in pointing out the direction in which they may
be sought.

PART I.

CONSIDERATIONS ON THE NATURAL HISTORY OF ANIMALS,

THEIR CHARACTERS, AFFINITIES, ORGANISATION,

CLASSIFICATION AND SPECIES.

CHAPTER I.

ON ARTIFICIAL DEVICES IN DEALING WITH THE
PRODUCTIONS OF NATURE.

Throughout nature, wherever man strives to acquire knowledge
he finds himself under the necessity of using special methods, 1st,
to bring order among the infinitely numerous and varied objects
which he has before him ; 2nd, to distinguish, without danget of
confusion, among this immense multitude of objects, either groups
of those in which he is interested, or particular individuals among
them ; 3rd, to pass on to his fellows all that he has learnt, seen and
thought on the subject. Now the methods which he uses for this
purpose are what I call the artificial devices in natural science, — devices
which we must beware of confusing with the laws and acts of nature
herself.

It is not merely necessary to distinguish in natural science what
belongs to artifice and what to nature. We have to distinguish as
well two very different interests which incite us to the acquisition
of knowledge.

The first is an interest which I call economic, because it derives
its impetus from the economic and utilitarian needs of man in deal-
ing with the productions of nature which he wants to turn to his
own use. From this point of view he is only interested in what
he thinks may be useful to him.

The other, very different from the first, is that philosophic interest
through which we desire to know nature for her own sake, in order
to grasp her procedure, her laws and operations, and to gain an ider
of what she actually brings into existence. This, in short, is the kind of
knowledge which constitutes the true naturalist. Those who approach
the subject from this point of view are naturally few ; they are in-
terested impartially in all natural productions that they can observe.

To begin with, economic and utilitarian requirements resulted
in the successive invention of the various artificial devices employed

20 ZOOLOGICAL PHILOSOPHY

in natural science. When the interest of studying and knowing
nature was first felt, these artificial devices continued to be of assist-
ance in the prosecution of that study. These same artificial devices
have therefore an indispensable utility, not only for helping us to a
knowledge of special objects, but for faciUtating study and the pro-
gress of natural science, and for enabling us to find our way about
among the enormous quantity of different objects that we have to
deal with.

Now the 'philosophic interest embodied by the sciences in question,
although less widespread than that which relates to our economic
requirements, compels us to separate what belongs to artifice from
what is the sphere of nature. We have to confine within reason-
able limits the consideration due to the first set of objects, and attach
to the second all the importance that they deserve.

The artificial devices in natural science are as follows :

(1) Schematic classifications, both general and special.

(2) Classes.

(3) Orders.

(4) Families.

(5) Genera.

(6) The nomenclature of various groups of individual objects.
These six kinds of devices, commonly used in natural science, are

purely artificial aids which we have to use in the arrangement and
division of the various observed natural productions ; to put us in
the way of studying, comparing, recognising and citing them. Nature
has made nothing of this kind : and instead of deceiving ourselves
into confusing our works with hers, we should recognise that classes,
orders, families, genera and nomenclatures are weapons of our own
invention. We could not do without them, but we must use them
with discretion and determine them in accordance with settled
principles, in order to avoid arbitrary changes which destroy all the
advantages they bestow.

It was no doubt indispensable to break up the productions of nature
into groups, and to establish different kinds of divisions among them,
such as classes, orders, families and genera. It was, moreover, necessary
to fix what are called species, and to assign special names to these
various sorts of objects. This is required on account of the limitations
of our faculties ; some such means are necessary for helping us to fix
the knowledge which we gain from that prodigious multitude of
natural bodies which we can observe in their infinite diversity.

But these groupings, of which several have been so happily drawn
up by naturalists, are altogether artificial, as also are the divisions
and sub-divisions which they present. Let me repeat that nothing

ARTIFICIAL DEVICES 21

of the kind is to be found in nature, notwithstanding the justification
which they appear to derive from certain apparently isolated portions
of the natural series with which we are acquainted. We may, there-
fore, rest assured that among her productions nature has not really
formed either classes, orders, families, genera or constant species,
but only individuals who succeed one another and resemble those
from which they sprung. Now these individuals belong to infinitely
diversified races, which blend together every variety of form and degree
of organisation ; and this is maintained by each without variation,
so long as no cause of change acts upon them.

Let us proceed to a few brief observations with respect to each
of the six artificial devices employed in natural science.

Schematic classifications. — By schematic classifications, general or
special, I mean any series of animals or plants that is drawn up un-
conformably to nature, that is to say, which does not represent
either her entire order or some portion of it. It is consequently
not based on a consideration of ascertained affinities.

The belief is now thoroughly justified that an order estabUshed by
nature exists among her productions in each kingdom of living bodies :
this is the order on which each of these bodies was originally formed.

This same order is individual and essentially without divisions
in each organic kingdom. It becomes known to us through the
affinities, special and general, existing among the different objects
of which these two kingdoms consist. The living bodies at the two
extremities of that order have essentially the fewest affinities, and
exhibit the greatest possible differences in their organisation and
structure.

It is this same order, as we come to know it, that will have to replace
those schematic or artificial classifications that we have been forced
to create in order to arrange conveniently the different natural
bodies that we have observed.

With regard to the various organised bodies recognised by observa-
tion, there was at first no other thought beyond convenience and ease
of distinction between these objects ; and it has taken the longer to
seek out the actual order of nature in their classification, inasmuch
as there was not even a suspicion of the existence of such an
order.

Hence arose groupings of every kind, artificial systems and methods,
based upon considerations of such an arbitrary character that they
underwent almost as many changes in their principles and nature as
there were authors to work upon them.

With regard to plants, the sexual system of Linnaeus, ingenious
as it is, presents a general schematic classification : and, with regard

22 ZOOLOGICAL PHILOSOPHY

to insects, the entomology of Fabricius presents a special schematic
classification. All the progress made in recent times by the philo-
sophy of natural science has been necessary, in France at least, to carry
the conviction that the natural method should be studied. Our
classifications should conform to the exact order found in nature,
for that order is the only one which remains stable, independent of
arbitrary opinion, and worthy of the attention of the naturalist.

Among plants, the natural method is extremely difiicult to
estabUsh, on account of the obscurity prevailing in the character
of the internal organisation of these living bodies, and of the differences
presented by plants of different families. Since the learned observa-
tions of M. Antoine-Laurent de Jussieu, however, a great step has
been made in botany in the direction of the natural method ; many
families have been constituted with direct reference to their affinities ;
but the general position of all these families among themselves, and
consequently of the whole order, remains to be determined. The fact
is that we have found the beginning of that order ; but the
middle, and especially the end, are still at the mercy of arbitrary
opinion.

The case is different with regard to animals ; their organisation
is much more pronounced, and presents different systems that are easier
to grasp. The work has, therefore, in their case made greater pro-
gress ; as a result, the actual order of nature in the animal kingdom
is now sketched out in its main outlines in a stable and satisfactory
manner. It is only the boundaries of classes and their orders, of
families and genera, that are still abandoned to arbitrary opinion.

If schematic classifications are still found among animals, these
classifications are only minor, since they deal with objects belonging
to one class. Thus, the hitherto received classifications of fishes and
birds are still schematic classifications.

With regard to living bodies, the farther one descends from the
general to the particular the less constant become the characters
serving to determine affinities, and the more difficult to recognise
is the actual order of nature.

Classes. — The name class is given to the highest kind of general
divisions that are established in a kingdom. The further divisions
of these receive other names : we shall speak of them directly. The
more complete is our knowledge of the affinities between the objects
composing a kingdom, the better and more natural are the classes
established as the primary divisions of that kingdom, so long
as attention has been paid to recognised affinities in forming them.
Nevertheless, the boundaries of these classes, even the best of them,
are clearly artificial ; they will therefore continue to undergo

ARTIFICIAL DEVICES 23

arbitrary variations at the hands of authors so long as naturahsts
will not agree and submit themselves to certain general principles
on the subject.

Thus, even though the order of nature in a kingdom should be
thoroughly known, the classes which we are obliged to establish
in it will always be fundamentally artificial divisions.

It is true, especially in the animal kingdom, that several of these
divisions appear to be really marked out by nature herself ; and it is
certainly difficult to believe that mammals, birds, etc. , are not sharply
isolated classes formed by nature. This is none the less a pure illusion,
and a consequence of the limitation of our knowledge of existing
or past animals. The further we extend our observations the more
proofs do we acquire that the boundaries of the classes, even appar-
ently most isolated, are not unlikely to be effaced by our new discoveries.
Already the Ornithorhyncus and the Echidna seem to indicate the exist-
ence of animals intermediate between birds and mammals. How
greatly natural science would profit if the vast region of Australia
and many others were better known to us !

If classes are the first kind of division that can be established in a
kingdom, it follows that the divisions which can be established among
the objects of one class cannot themselves be classes ; for it is obviously
inappropriate to set up class within class ; that, however, is just what
has been done : Brisson, in his Ornithologie, has divided the class of
birds into various special classes.

Just as nature is everywhere governed by laws, so too artifice should
be subjected to rules. If there are none, or if they are not followed,
its products will be vacillating and its purpose fail.

Some modern naturalists have introduced the custom of dividing a
class into several sub-classes, while others again have carried out the
idea even with genera ; so that they make up not only sub-classes
but sub-genera as well. We shall soon reach not only sub-classes
but sub-orders, sub-families, sub-genera and sub-species. Now this
is a thoughtless misuse of artifice, for it destroys the hierarchy and
simplicity of the divisions, which had been set up by Linnaeus
and generally adopted.

The diversity of the objects belonging to a class either of animals or
plants is sometimes so great as to necessitate the formation of many
divisions and sub-divisions among the objects of that class ; but it
is to the interest of science that artificial devices should always have
the greatest possible simplicity. Now that interest allows, no doubt,
of any divisions and sub-divisions that may be necessary; but it is
opposed to each division having a special denomination. A stop
must be put to the abuses of nomenclature ; otherwise the nomen-

24 ZOOLOGICAL PHILOSOPHY

clature would become more difficult to understand than the objects
themselves.

Orders. — ^The name order should be given to the main divisions of
the first rank into which a class is broken up. If these divisions
leave scope for the formation of others by further sub-division, these
sub-divisions are no longer orders ; and it would be very inappro-
priate to give them the name.

The class of molluscs, for example, are easily divided into two large
main groups, one having a head, eyes, etc., and reproducing by
copulation, while the other has no head, eyes, etc., and carry out no
copulation to reproduce themselves. Cephalic and acephalic molluscs
should be regarded as the two orders of that class ; meanwhile, each
of these orders can be broken up into several remarkable groups.
Now this fact is no sufficient reason for giving the name order or
even sub-order to each of the groups concerned. These groups, there-
fore, into which orders are divided should be regarded as sections
or as large families, themselves susceptible of still further sub-
divisions.

Let us maintain in our artifical devices the great simpUcity and
beautiful hierarchy established by Linnaeus. If we are under the
necessity to make many sub-divisions of orders, that is to say, of the
principle divisions of a class, by all means let us make as many as
may be necessary, but do not let us assign to them any special
denomination.

The orders into which a class is divided should be determined
by the presence of important characters extending throughout the
objects comprised in each order ; but no special name should be
assigned to them that is applicable to the objects themselves.

The same thing appUes with regard to the sections that we have
to form among the orders of one class.

Families. — The name family is given to recognised parts of the
order of nature in either of the two kingdoms of living bodies. These
parts of the natural order are, on the one hand, smaller than classes
and even than orders, but, on the other hand, they are larger than
genera. But however natural families may be and however well
constituted their genera are according to their true affinities, the
boundaries of these families are always artificial. The more indeed
that the productions of nature are studied, and new ones observed,
the greater the continual variations in the boundaries of families
that are made by naturalists. Some divide one family into several
new ones, others combine several families into one, while others
again make additions to a family already known, increase it, and thua
thrust back the boundaries which had been assigned to it.

ARTIFICIAL DEVICES 25

If all the races (so-called species) belonging to a kingdom of living
bodies were thoroughly known, as well as their true affinities, so that
the sorting out of these races and their allocation in various groups
were in conformity with their natural affinities, the classes, orders,
sections and genera would be families of different sizes, for all these
divisions would be larger or smaller parts of the natural order.

On such an assumption, nothing doubtless would be more difficult
than to assign the boundaries between these different divisions ;
arbitrary opinion would produce incessant variation, and there would
be no agreement except where gaps in the series made clear demarca-
tions.

Fortunately for the practicability of the artifice which we have to
introduce into our classifications, there are many races of animals
and plants that are still unknown to us, and will probably remain so,
since insuperable obstacles are placed in our way by the places where
they Uve and other circumstances. The gaps thence arising in the
series, whether of animals or plants, will leave us for a long time still,
and perhaps for ever, the means of setting up the majority of the
divisions.

Custom and indeed necessity require that a special name should
be given to each family and to each genus so as to be applicable to
the objects it contains. It follows that alterations in the boundaries,
extent and determination of families will always cause a change in
their nomenclature.

Genera. — The name of genus is given to combinations of races or
so-called species that have been united on account of their affinities,
and constitute a number of small series marked out by characters
arbitrarily selected for the purpose.

When a genus is well made, all the races or species comprised in it
resemble one another in their most essential and numerous characters.
They differ only among themselves in characters less important,
but sufficient to distinguish them.

Well made genera are thus really small families, that is to say, real
parts of the actual order of nature.

Now we have seen that the series to which we give the name of
family are liable to vary as to their boundaries and extent, according
to the opinions of authors who arbitrarily change their guiding
principles. In the same way the boundaries of genera are exposed
to infinite variation because different authors change at will the
characters employed to determine them. Now a special name has to
be assigned to each genus ; and every change in the constitution
of a genus involves nearly always a change of name. It is difficult
therefore to exaggerate the injury done to natural science by

26 ZOOLOGICAL PHILOSOPHY

perpetual alterations of genera, which multiply synonymy, overburden
nomenclature, and make the study of these sciences difiScult and
disagreeable.

When will naturalists agree to abide by general principles for uniform
guidance in the constitution of genera, etc., etc. ? The natural
affinities, which they recognise among the objects which they have
brought together, mislead them nearly all into the belief that their
genera, families, orders and classes actually exist in nature. They
do not notice that the good series which they succeed in forming
by study of affinities do in truth exist in nature, for they are large
or small parts of her order, but that the lines of demarcation which
they are obliged to set up at intervals do not by any means so exist.

Consequently, genera, families, sections of various kinds, orders
and even classes are in truth artificial devices, however natural may
be the series which constitute these different groups. No doubt they
are necessary and have an obvious and indispensable utility ; but if
the advantages, which these devices bring, are not to be cancelled
by constant misuse, the constitution of every group must be in accord-
ance with principles and rules that naturalists once for all have agreed
to follow.

Nomenclature. — We come now to the sixth of the artificial devices
which have to be employed in natural science. By nomenclature
is meant the system of names assigned either to special objects,
such as a race or a species, or to groups of these objects, such as a
genus, family or class.

Now nomenclature is confined to the names given to species, genera,
families and classes. It has therefore to be distinguished from that
other artificial device called technology, which refers solely to the
denominations applied to the parts of natural bodies.

" All the discoveries and observations of naturalists would
necessarily have fallen into oblivion and been lost to society, if the
objects observed and determined had not each received a name to serve
as a recognition mark when speaking of them or quoting them."
{Did. de Botanique, art. "Nomenclature.")

It is quite clear that nomenclature in natural history is an artificial
device, and is a means that we have to resort to for fixing our ideas in
the sphere of natural observed productions, and to enable us to pass
on either these ideas or our observations on the objects concerned.

No doubt this artificial device should like the others be controlled
by settled rules that are generally adhered to ; but I am bound to
remark that its universal misuse, of which complaints are so justly
made, arises principally from extrinsic causes which daily increase
also in the other artificial devices already named.

ARTIFICIAL DEVICES 27

In fact, lack of settled rules as to the formation of genera, families
and even classes, exposes these artificial devices to all the vagaries
of arbitrary judgment ; nomenclature undergoes a continuous succession
of changes. It never can be fixed so long as this lack of rules con-
tinues ; and synonymy, already immense, will continue to grow and
become more and more incapable of repairing a confusion which
annihilates all the advantages of science.

This would never have happened if it had been recognised that
all the lines of demarcation in the series of objects composing a king-
dom of living bodies are really artificial, except those which result
from gaps to be filled. But this was not perceived : there was not
even a suspicion of it. Almost to the present day naturalists have
had no further object in view than that of setting up distinctions.
Here is evidence of what I mean :

" In fact, in order to procure and keep for ourselves the services of
all natural bodies within our reach, that we can subordinate to our
needs, it was felt that an exact and precise determination of the
characters of each body was necessary, and consequently that the
details of organisation, structure, form, proportion, etc., etc., should
be sought out and determined, so that they could for all time be
recognised and distinguished from one another. This is what
naturalists are now doing up to a certain point.

" This part of the work of naturalists has made the most advance.
Immense efforts have rightly been made for about a century and a
half to perfect it, because it assists us to a knowledge of what
has been newly observed, and serves as reminder of what was
previously known. Moreover, it fixes our knowledge with regard
to objects whose properties are or will hereafter become of use
to us.

" But naturalists attach too much weight to forming lines of
demarcation in the general series both of animals and plants ; they
devote themselves almost exclusively to this kind of work, without
considering it under its true aspect or coming to any agreement as
to the framing of settled rules in this great enterprise for fixing the
principles of determination. Hence the intrusion of many abuses ;
for each one arbitrarily changes the principles for the formation of
classes, orders and genera : and numerous different groupings are
incessantly being set before the public. Genera undergo continual
variation without limit, and the names given to nature's pro-
ductions are constantly being changed as a result of this thoughtless
proceeding.

" As a result, synonomy in natural history is now terribly wide-
spread. Science every day becomes more obscure ; she is surrounded

28 ZOOLOGICAL PHILOSOPHY

by almost insurmountable difficulties ; and the finest effort of man
to set up the means of recognising and distinguishing the works of
nature is changed into an immense maze, into which most men
naturally hesitate to plunge." {Discours d'ouvert, du cours de 1806,
pp. 5 and 6.)

Here we have a picture of the results of omitting to distinguish
what really belongs to artifice from what is in nature, and of not having
endeavoured to discover rules for the less arbitrary determination
of the divisions which have to be established.

CHAPTEK II.

IMPORTANCE OF THE CONSIDERATION OF AFFINITIES.

Among living bodies the name affinity has been given to features of
analogy or resemblance between two objects, that are compared in
their totality, but with special stress on the most essential parts.
The closer and more extensive the resemblance, the greater the
affinities. They indicate a sort of kinship between the living bodies
which exhibit them ; and oblige us in our classification to place
these bodies in a proximity proportional to their affinities.

How great has been the progress of natural science since serious
attention began to be given to affinities, and especially since their
true underlying principles have been determined !

Before this change, our botanical classifications were entirely at
the mercy of arbitrary opinion, and of artificial systems of any
author. In the animal kingdom the invertebrate animals comprising
the larger part of all known animals were classified into the most
heterogeneous groups, some under the name of insects, some under the
name of worms ; where the animals included are from the point of
view of affinity widely different from one another.

Happily this state of affairs is now changed ; and, henceforth, if
the study of natural history is continued, its progress is assured.

The principle of natural affinities removes all arbitrariness from
our attempts at a methodical classification of organised bodies. We
have here the law of nature which should guide us to the natural
method. Naturalists are forced to agree as to the rank which they
assign, firstly to the main groups of their classification, and after-
wards to the individuals of which these groups are composed ; finally,
they are obliged to follow the actual order observed by nature in
giving birth to her productions.

Thus, everything that concerns the affinities of the various animals
should be the chief object of our researches, before making any division
or classification among them.

30 ZOOLOGICAL PHILOSOPHY

The question of affinities does not apply only to species ; for we
have also to fix the general affinities of all the orders into which groups
are united or divided from the comparative point of view.

Affinities, although possessing very different values according to the
importance of the parts exhibiting them, can none the less be extended
to the conformation of the external parts. If the affinities are so great
that not only the essential parts, but also the external parts present
no determinable difference, then the objects in question are only
individuals of the same species. If on the other hand, notwith-
standing a large degree of affinity, the external parts exhibit appreci-
able differences, though less than the essential resemblances ; then
the objects in question are different species of the same genus.

The important study of affinities is not limited to a comparison
of classes, families, or even of species ; it includes also a considera-
tion of the parts of which individuals are composed. By comparison
together of corresponding parts we obtain a firm basis for recognis-
ing either the identity of individuals of the same race or the difference
between individuals of distinct races.

It has, in truth, been noted that the proportions and relations of
the parts of all individuals composing a species or a race always
remain the same, and so appear to be preserved forever. From this
it has been rightly inferred that, by examining detached parts of an
individual, one could decide to what species, old or new, these parts
belong.

This power is very favourable to the progress of knowledge at the
present time. But the conclusions drawn from it can only hold good
for a limited period ; since the races themselves undergo changes
in their parts, in proportion to any considerable change in the circum-
stances which affect them. As a matter of fact, since these changes
only take place with an extreme slowness, which makes them always
imperceptible, the proportions and relations of the parts always appear
the same to the observer, who does not really see them change.
Hence, when he comes across any species which have undergone
these changes, he imagines that the differences which he perceives
have always existed.

It is none the less quite true that by a comparison of corresponding
parts in different individuals, their affinities, nearer or more remote,
can be easily and certainly determined. It can therefore be known
whether these parts belong to individuals of the same race or of
different races.

It is only the general inference that is unsound, having been drawn
too hastily. This I shall have more than one opportunity of proving
in the course of the present work.

IMPORTANCE OF AFFINITIES 31

AfiBnities are always incomplete when they apply only in an isolated
case ; that is to say, when they are decided from an examination
of a single part taken by itself. But, although incomplete, the value
of affinities based upon a single part depends upon the extent to which
the part from which they are taken is essential, and vice versa.

There are then determinable differences among affinities, and various
degrees of importance among the parts which display them ; in
fact, the knowledge of affinities would have had no application or
utility unless the more important parts of living bodies had been
distinguished from the less important, and unless a principle had been
found for estimating the true values of these important parts.

The most important parts for exhibiting the chief affinities are,
among animals, the parts essential to the maintenance of life, and
among plants, the parts essential to reproduction.

In animals, therefore, it is always the internal organisation that will
guide us in deciding the chief affinities. And. in plants, it will be
in the parts of fructification that affinities will be sought.

But in both cases the parts most important for seeking out affinities
vary. The only principle to be used for determining the importance
of any part, without arbitrary assumptions, consists in enquiring
either how much use nature makes of it, or else the importance to the
animal of the function of that part.

Among animals, whose affinities are mainly determined by their
internal organisation, three kinds of special organs have rightly been
chosen from among the others as the most suitable for disclosing
the most important affinities. They are, in order of importance, as
follows :

(1) TJie organ of feeling. The nerves which meet at a centre, either
single as in animals with a brain, or multiple as in those with a
ganglionic longitudinal cord.

(2) The organ of respiration. The lungs, gilLs and tracheae.

(3) The organ of circulation. The arteries and veins, which usually
have a centre of action in the heart.

The first two of these organs are more widely used by nature, and
therefore more important than the third, that is to say, the organ of
circulation ; for the latter disappears in the series after the crustaceans,
while the two former extend to animals of the two classes which follow
the crustaceans.

Finally, of the two first, the organ of feeling has the more import-
ance from the point of view of affinities, for it has produced the most
exalted of animal faculties, and moreover without that organ muscular
activity could not take place.

If I were to refer to plants, among which the reproductive parts

32 ZOOLOGICAL PHILOSOPHY

alone are of importance in deciding affinities, I should set forth these
parts in their order of importance as follows :

(1) The embryo, its accessories (cotyledons, perisperm) and the
seed which contains it.

(2) The sexual parts of flowers, such as the pistil and stamens.

(3) The envelopes of the sexual parts ; the corolla, calyx, etc.

(4) The pericarp, or envelope of the seed.

(5) The reproductive bodies which do not require fertilisation.
These generally received principles give to natural science a coherence

and solidity that it did not previously possess. Affinities are no longer
at the mercy of changes of opinion ; our general classifications become
necessary inferences ; and according as we perfect them by this
method they approach ever more closely to the actual order of
nature.

It was, in fact, due to the perception of the importance of affinities that
the attempts of the last few years were originated to determine what
is called the natural method ; a method which is only a tracing by
man of nature's procedure in bringing her productions into existence.

No importance is now attached in France to those artificial systems
which ignore the natural affinities among objects ; for these systems
give rise to divisions and classifications harmful to the progress of
natural knowledge.

With regard to animals, there is no longer any doubt that it is purely
from their organisation that their natural affinities can be determined.
It is, in consequence, chiefly from comparative anatomy that zoology
will obtain the data for such determination. But we should pay
more attention to the facts collected in the works of anatomists than
to the inferences which they draw from them ; for too often they hold
views which might mislead us and prevent us from grasping the
laws and true plan of nature. It seems to be the case that whenever
man observes any new fact he is always condemned to rush headlong
into error in attempting to explain it ; so fertile is his imagination
in the creation of ideas. He is not sufficiently careful to guide his
judgment by the general principles derived from other facts and
observations.

When we consider the natural affinities between objects, and make
a sound estimate of them, we can combine species on this principle,
and associate groups with definite boundaries forming what are
called genera. Genera can be similarly associated on the principle of
affinities, and united into higher groups forming what are called
families. These families, associated in the same way and on the same
principle, make up orders. These again are the primary divisions of
classes, while classes are the chief divisions of each kingdom.

IMPORTANCE OF AFFINITIES 33

We must then be guided everywhere by natural affinities in composing
the groups which result by dividing each kingdom into classes, each
class into orders, each order into sections or famihes, each family
into genera, and each genus into different species if there is occasion
for it.

There is thorough justification for the belief that the complete series
of beings making up a kingdom represents the actual order of nature,
when it is classified with direct reference to affinities ; but, as I have
already pointed out, the different kinds of divisions which have to
be set up in that series to help us to distinguish objects with greater
ease do not belong to nature at all. They are truly artificial although
they exhibit natural portions of the actual order instituted by
nature.

It should be added that in the animal kingdom, affinities should
be decided mainly from a study of organisation. The principles
employed for settling these affinities should not admit of the smallest
doubt. We shall thus obtain a solid basis for zoological philosophy.

It is known that every science must have its philosophy, and that
it cannot make real progress in any other way. It is in vain that
naturalists fill their time in describing new species, in grasping all
the shades and small details of their varieties, in enlarging the immense
list of catalogued species, in establishing genera, and in making incessant
changes in the principles which they use. If the philosophy of science
is neglected her progress will be unreal, and the entire work will
remain imperfect.

It is indeed only since the attempt has been made to fix the extent
of affinity between the productions of nature that natural science
has obtained any coherence in its principles, and a philosophy to make
it really a science.

What progress towards perfection is made every day in our classi-
fications since they were founded upon the study of affinities !

It was through the study of affinities that I recognised that in-
fusorian animals could no longer be put in the same class as polyps ;
that radiarians also should not be confused with polyps ; and that
soft creatures, such as medusae and neighbouring genera, which
Linnaeus and even Bruguière placed among the molluscs, were essen-
tially allied to the echinoderms, and should form a special class with
them.

It was again the study of affinities which convinced me that worms
were a separate group, comprising animals very different from
radiarians, and still more from polyps ; that arachnids could no longer
be classed with insects, and that cirrhipedes were neither annelids nor
molluscs.

34 ZOOLOGICAL PHILOSOPHY

Finally, it was through the study of affinities that I succeeded in
effecting a number of necessary alterations even in the classification
of molluscs, and that I recognised that the pteropods, which are closely
allied to but distinct from the gastropods, should not be placed
between the gastropods and the cephalapods, but between the ace-
phalic molluscs and the gastropods ; since these pteropods, like all
acephalic animals, have no eyes and are almost without a head, not
even excepting Hyalea. (F. the special classification of molluscs
in Chap. VIII., at the end of Part I.)

When the study of affinities among the different known families
of plants has made us better acquainted with the rank held by each
in the general series, then the classification of these living bodies
will leave nothing more to arbitrary judgment, but will come more
closely into conformity with the actual order of nature.

The study of the affinities among observed objects is thus clearly
80 important that it should now be regarded as the chief instrument
for the progress of natural science.

CHAPTER III.

OF SPECIES AMONG LIVING BODIES AND THE IDEA THAT WE
SHOULD ATTACH TO THAT WORD.

It is not a futile purpose to decide definitely what we mean by the
so-called species among living bodies, and to enquire if it is true that
species are of absolute constancy, as old as nature, and have all existed
from the beginning just as we see them to-day ; or if, as a result of
changes in their environment, albeit extremely slow, they have not
in course of time changed their characters and shape.

The solution of this question is of importance not only for our
knowledge of zoology and botany, but also for the history of the
world.

I shall show in one of the following chapters that every species has
derived from the action of the environment in which it has long been
placed the habits which we find in it. These habits have themselves
influenced the parts of every individual in the species, to the extent
of modifying those parts and bringing them into relation with the
acquired habits. Let us first see what is meant by the name of species.

Any collection of like individuals which were produced by others
similar to themselves is called a species.

This definition is exact ; for every individual possessing life always
resembles very closely those from which it sprang ; but to this definition
is added the allegation that the individuals composing a species never
vary in their specific characters, and consequently that species have
an absolute constancy in nature.

It is just this allegation that I propose to attack, since clear proofs
drawn from observation show that it is ill-founded.

The almost universally received belief is that living bodies con-
stitute species distinguished from one another by unchangeable
characteristics, and that the existence of these species is as old as
nature herself. This belief became established at a time when no
sufficient observations had been taken, and when natural science

36 ZOOLOGICAL PHILOSOPHY

was still almost negligible. It is continually being discredited for
those who have seen much, who have long watched nature, and who
have consulted with profit the rich collections of our museums.

Moreover, all those who are much occupied with the study of natural
history, know that naturalists now find it extremely difficult to decide
what objects should be regarded as species.

They are in fact not aware that species have really only a constancy
relative to the duration of the conditions in which are placed the
individuals composing it ; nor that some of these individuals have
varied, and constitute races which shade gradually into some other
neighbouring species. Hence, naturalists come to arbitrary decisions
about individuals observed in various countries and diverse con-
ditions, sometimes calling them varieties and sometimes species. The
work connected with the determination of species therefore becomes
daily more defective, that is to say, more complicated and confused.

It has indeed long been observed that collections of individuals
exist which resemble one another in their organisation and in the
sum total of their parts, and which have kept in the same condition
from generation to generation, ever since they have been known.
So much so that there seemed a justification for regarding any col-
lection of like individuals as constituting so many invariable species.
Now attention was not paid to the fact that the individuals of the
species perpetuate themselves without variation only so long as the
conditions of their existence do not vary in essential particulars.
Since existing prejudices harmonise well with these successive
regenerations of like individuals, it has been imagined that every
species is invariable and as old as nature, and that it was specially
created by the Supreme Author of all existing things.

Doubtless, nothing exists but by the will of the Sublime Author
of all things, but can we set rules for him in the execution of his will,
or fix the routine for him to observe ? Could not his infinite power
create an order of things which gave existence successively to all that
we see as well as to all that exists but that we do not see ?

Assuredly, whatever his will may have been, the immensity of his
power is always the same, and in whatever manner that supreme
will may have asserted itself, nothing can diminish its grandeur.

I shall then respect the decrees of that infinite wisdom and con-
fine myself to the sphere of a pure observer of nature. If I succeed
in unravelling anything in her methods, I shall say without fear of
error that it has pleased the Author of nature to endow her with that
faculty and power.

The idea formed of species among living bodies was quite simple,
easy to understand, and seemed confirmed by the constancy in the

OF SPECIES 37

shapes of individuals, perpetuated by reproduction or generation.
Such are a great number of these alleged species that we see every day.

Meanwhile, the farther we advance in our knowledge of the various
organised bodies which cover almost every part of the earth's surface,
the greater becomes our difficulty in determining what should be
regarded as a species, and still more in finding the boundaries and
distinctions of genera.

According as the productions of nature are collected and our
museums grow richer, we see nearly all the gaps filled up and the Unes
of demarcation effaced. We find ourselves reduced to an arbitrary
decision which sometimes leads us to take the smallest differences
of varieties and erect them into what we call species, and sometimes
leads us to describe as a variety of some species slightly differing
individuals which others regard as constituting a separate species.

Let me repeat that the richer our collections grow, the more proofs
do we find that everything is more or less merged into everything
else, that noticeable differences disappear, and that nature usually
leaves us nothing but minute, nay puerile, details on which to found
our distinctions.

How many genera there are both among animals and plants, among
which the number of species referred to them is so great that the study
and determination of these species are well nigh impracticable ! The
species of these genera, arranged in series according to their natural
affinities, exhibit such slight differences from those next them as to
coalesce with them. These species merge more or less into one another,
so that there is no means of stating the small differences that dis-
tinguish them.

It is only those who have long and diligently studied the question
of species, and who have examined rich collections, that are in a
position to know to what extent species among living bodies merge
into one another. And no one else can know that species only appear
to be isolated, because others are lacking which are close to them
but have not yet been collected.

I do not mean that existing animals form a very simple series,
regularly graded throughout ; but I do mean that they form a branch-
ing series, irregularly graded and free from discontinuity, or at least
once free from it. For it is alleged that there is now occasional dis-
continuity, owing to some species having been lost. It follows that
the species terminating each branch of the general series are connected
on one side at least with other neighbouring species which merge into
them. This I am now able to prove by means of well-known facts.

I require no hypothesis or supposition ; I call all observing
naturalists to witness.

38 ZOOLOGICAL PHILOSOPHY

Not only many genera but entire orders, and sometimes even classes,
furnish instances of almost complete portions of the series which I
have just indicated.

When in these cases the species have been arranged in series, and
are all properly placed according to their natural afiSnities, if you
choose one, and then, jumping over several others, take another a little
way off, these two species when compared will exhibit great differ-
ences. It is thus in the first instance that we began to see such of
nature's productions as lay nearest to us. Generic and specific dis-
tinctions were then quite easy to establish ; but now that our collec-
tions are very rich, if you follow the above-mentioned series from the
first species chosen to the second, which is very different from it, you
reach it by slow gradations without having observed any noticeable
distinctions.

I ask, where is the experienced zoologist or botanist who is not
convinced of the truth of what I state ?

How great the difficulty now is of studying and satisfactorily
deciding on species among that multitude of every kind of polyps,
radiarians, worms, and especially insects, such as butterflies, Phalaena,
Noctua, Tinea, flies. Ichneumon, Curculio, Cerambix, chafers, rose-
chafers, etc. ! These genera alone possess so many species which
merge indefinably into one another.

What a swarm of mollusc shells are furnished by every country
and every sea, eluding our means of distinction and draining our
resources.

Consider again, fishes, reptiles, birds and even mammals ; you
will see that except for gaps still to be filled, neighbouring species
and even genera are separated by the finest differences, so that we have
scarcely any foothold for setting up sound distinctions.

Is there not an exactly similar state of affairs in the case of botany,
which deals with the other series, consisting of plants ?

How great indeed are the difficulties of the study and determina-
tion of species in the genera Lichen, Fucus, Carex, Poa, Piper,
Euphorbia, Erica, Hieracium, Solanum, Geranium, Mimosa, etc., etc.

When these genera were constituted only a small number of species
belonging to them were known, and it was then easy to distinguish
them ; but now that nearly all the gaps are filled, our specific
differences are necessarily minute and usually inadequate.

Let us see what are the causes which have given rise to this un-
doubted state of affairs ; let us see if nature affords any explanation,
and whether observation can help us.

We learn from a number of facts that, according as the individuals
of one of our species change their abode, climate, habits, or manner

OF SPECIES 39

of life, they become subject to influences which little by little alter the
consistency and proportions of their parts, their shape, properties and
even their organisation ; so that in course of time everything in them
shares in these mutations.

In the same climate, very different habitats and conditions at first
merely cause variations in the individuals exposed to them ; but
in course of time the continued change of habitat in the individuals
of which I speak, living and reproducing in these new conditions,
induces alterations in them which become more or less essential to
their being ; thus, after a long succession of generations these in-
dividuals, originally belonging to one species, become at length
transformed into a new species distinct from the first.

Suppose, for example, that the seeds of a grass or any other plant
that grows normally in a damp meadow, are somehow conveyed
first to the slope of a neighbouring hill where the ground although
higher is still rich enough to allow the plant to maintain its existence.
Suppose that then, after living there and reproducing itself many times,
it reaches little by little the dry and almost barren ground of a mountain
side. If the plant succeeds in living there and perpetuating itself
for a number of generations, it will have become so altered that botanists
who come across it will erect it into a separate species.

The same thing happens in the case of animals that are forced
by circumstances to change their climate, habits, and manner of
life : but in their case more time is required to work any noticeable
change than in the case of plants.

The idea of bringing together under the name of species a collection
of like individuals, which perpetuate themselves unchanged by re-
production and are as old as nature, involved the assumption that the
individuals of one species could not unite in reproductive acts with
individuals of a different species.

Unfortunately, observation has proved and continues every day to
prove that this assumption is unwarranted ; for the hybrids so common
among plants, and the copulations so often noticed between animals
of very different species, disclose the fact that the boundaries between
these alleged constant species are not so impassable as had been
imagined.

It is true that often nothing results from these strange copulations,
especially when the animals are very disparate ; and when any-
thing does happen the resulting individuals are usually infertile ;
but we also know that when there is less disparity these defects do not
occur. Now this cause is by itself sufficient gradually to create
varieties, which then become races, and in course of time constitute
what we call species.

40 ZOOLOGICAL PHILOSOPHY

To assist us to a judgment as to whether the idea of species has
any real foundation, let us revert to the principles already set forth ;
they show :

(1) That all the organised bodies of our earth are true productions
of nature, wrought successively throughout long periods of time.

(2) That in her procedure, nature began'^and still begins by fashion-
ing the simplest of organised bodies, and that it is these alone which
she fashions immediately, that is to say, only the rudiments of
organisation indicated in the term spontaneous generation.

(3) That, since the rudiments of the animal and plant were
fashioned in suitable places and conditions, the properties of a com-
mencing life and estabUshed organic movement necessarily caused
a gradual development of the organs, and in course of time produced
diversity in them as in the Umbs.

(4) That the property of growth is inherent in every part of the
organised body, from the earliest manifestations of life ; and then
gave rise to different kinds of multiphcation and reproduction, so
that the increase of complexity of organisation, and of the shape and
variety of the parts, has been preserved.

(5) That with the help of time, of conditions that necessarily were
favourable, of the changes successively undergone by every part of
the earth's surface, and, finally, of the power of new conditions and
habits to modify the organs of Uving bodies, all those which now exist
have imperceptibly been fashioned such as we see them.

(6) That, finally, in this state of affairs every living body underwent
greater or smaller changes in its organisation and its parts ; so that what
we call species were imperceptibly fashioned among them one after
another and have only a relative constancy, and are not as old as nature.

But objections may be raised to the allegation that nature has
little by httle fashioned the various animals known to us by the aid
of much time and an infinite variation of environment. It may be
asked whether this allegation is not refuted by the single fact of the
wonderful variety observed in the instinct of various animals, and in
the marvellous skill of all kinds which they exhibit.

Will anyone, it may be asked, venture to carry his love of system
so far as to say that nature has created single-handed that astonishing
diversity of powers, artifice, cunning, foresight, patience and skill,
of which we find so many examples among animals ? Is not what
we see in the single class of insects far more than enough to convince
us that nature cannot herself produce so many wonders ; and to
compel the most obstinate philosopher to recognise that the will of the
Supreme Author of all things must be here invoked, and could alone
suffice for bringing into existence so many wonderful things ?

OF SPECIES 41

No doubt he would be a bold man, or rather a complete lunatic,
who should propose to set limits to the power of the first Author of all
things ; but for this very reason no one can venture to deny that
this infinite power may have willed what nature herself shows us it
has willed.

This being so, if I find that nature herself works all the wonders
just mentioned ; that she has created organisation, life and even
feehng, that she has multiplied and diversified within unknown limits
the organs and faculties of the organised bodies whose existence she
subserves or propagates ; that by the sole instrumentality of needs,
establishing and controlHng habits, she has created in animals the
fountain of all their acts and all their faculties, from the simplest
to instinct, to skill, and finally to reason ; if I find all this, should I
not recognise in this power of nature, that is to say in the order of exist-
ing things, the execution of the will of her Sublime Author, who was
able to will that she should have this power ?

Shall I admire the greatness of the power of this first cause of every-
thing any the less if it has pleased him that things should be so,
than if his will by separate acts had occupied itself and still continued
to occupy itself with the details of all the special creations, variations,
developments, destructions and renewals, in short, with all the muta-
tions which take place at large among existing things ?

Now I hope to prove that nature possesses the necessary powers
and faculties for producing herself that so much excite our wonder.

The objection is still raised however that everything we see in living
bodies indicates an unchangeable constancy in the preservation of
their form. It is held that all animals whose history has come down
to us for two or three thousand years have always been the same, and
neither lost nor acquired anything in the perfection of their organs
and the shape of their parts.

Not only had this apparent stabihty passed for an undoubted fact,
but an attempt has recently been made to find special proofs of it
in a report on the natural history collections brought from Egypt
by M. Geoffroy. The authors of the report express themselves as
follows :

" The collection has in the first place this peculiarity, that it may
be said to contain animals of all periods. It has long been asked
whether species change their shape in the course of time. This
question, apparently so futile, is none the less necessary for the history
of the world, and consequently for the solution of innumerable other
questions which are not foreign to the gravest subjects of human
worship.

" We have never been in so good a position to settle this question,

42 ZOOLOGICAL PHILOSOPHY

in so far as concerns a large number of remarkable species and some
thousands that are not remarkable. It appears as though the super-
stition of the ancient Egyptians were inspired by nature for the purpose
of leaving a record of her history."

" It is impossible," continue the authors of the report, " to control
our flights of imagination, on seeing still preserved with its smallest
bones and hair, perfectly recognisable, an animal which two or three
thousand years ago had in Thebes or Memphis its priests and altars.
But without giving rein to all the ideas suggested by this approach
to antiquity, we shall confine ourselves to the announcement that
this part of M. Geoffroy's collection shows that these animals are
exactly similar to those of to-day." {Annales du Muséum d'Hist.
natur., vol. i. pp. 235 and 236.)

I do not refuse to believe in the close resemblance of these animals
with individuals of the same species living to-day. Thus, the birds
that were worshipped and embalmed by the Egyptians two or three
thousand years ago are still exactly like those which now live in that
country.

It would indeed be very odd if it were otherwise ; for the position
and climate of Egypt are still very nearly what they were in those
times. Now the birds which live there, being still in the same conditions
as they were formerly, could not possibly have been forced into a change
of habits.

Furthermore, it is obvious that birds, since they can travel so easily
and choose the places which suit them, are less hable than many other
animals to suffer from variations in local conditions, and hence
less hindered in their habits.

Indeed there is nothing in the observation now cited that is con-
trary to the principles which I have set forth on this subject ; or
which proves that the animals concerned have existed in nature for
all time ; it proves only that they inhabited Egypt two or three
thousand years ago ; and every man who has any habit of reflection
and at the same time of observing the monuments of nature's
antiquity will easily appreciate the import of a duration of two or three
thousand years in comparison with it.

Hence we may be sure that this appearance of stability of the
things in nature will by the vulgar always be taken for reality ;
because people in general judge everything with reference to themselves.

For the man who forms his judgment only with reference to the
changes that he himself perceives, t-he eras of these mutations are
stationary states which appear to him to be unlimited, on account
of the shortness of the existence of individuals of his own species.

OF SPECIES 43

Moreover, we must remember that the records of his observations,
and the notes of facts which he has been able to register, only extend
back a few thousand years ; which is a time infinitely great with
reference to himself, but very small with reference to the time occupied
by the great changes occurring on the surface of the earth. Every-
thing seems to him to be stable in the planet which he inhabits ;
and he is led to repudiate the signs which exist everywhere in the
monuments heaped up around him, or buried in the soil which he
tramples underfoot.

Magnitudes are relative both in space and time : let man take that
truth to heart, and he will then be more reserved in his judgments
on the stability which he attributes to the state of things that he observes
in nature. (See the Appendix, p. 141, of my Recherches sur les corps
vivants.)

In order to admit the imperceptible changing of species, and the
modifications which their individuals undergo according as they
are forced to change their habits and contract" new ones, we are
not reduced to a mere consideration of the very short spaces of
time comprised in our observations ; for, in addition to this induc-
tion, a number of facts collected many years ago throw enough light
on the question to free it from doubt ; and I can now affirm that our
observations are so far advanced that the solution sought for is
patent.

Indeed not only do we know the results of anomalous fertilisations,
but we also now know positively that a compulsory and sustained
alteration in the habitats and manner of life of animals works after
a sufficient time a very remarkable mutation in the individuals exposed
to it.

Consider the animal which normally lives in freedom in plains
where it habitually exerts itself by swift running ; or the bird which
is compelled by its needs to pass incessantly through large spaces
in the air. When they find themselves imprisoned, the one in the
dens of a menagerie or in our stables, the other in our cages or back
yards, they undergo in course of time striking alterations, especially
after a succession of generations in their new state.

The former loses a great part of his swiftness and agility ; his body
thickens, the strength and subtleness of his Mmbs diminish, and his
faculties are no longer the same ; the latter becomes heavy, can
scarcely fly, and takes on more flesh in all his parts.

In Chapter VI. of this Part I., I shall have occasion to prove by
well-known facts the power of changes of conditions for giving to
animals new needs, and leading them on to new actions ; the power
of new actions when repeated to induce new habits and inclinations ;

44 ZOOLOGICAL PHILOSOPHY

finally, the power resulting from the more or less frequent use of any
organ to modify that organ either by strengthening, developing and
increasing it, or by weakening, reducing, attenuating it, and even
making it disappear.

With regard to plants, the same thing may be seen as a result of
new conditions on their manner of life and the state of their parts ;
so that we shall no longer be astonished to see the considerable changes
that we have brought about in those that we have long cultivated.

Thus, among living bodies, nature, as I have already said, definitely
contains nothing but individuals which succeed one another by
reproduction and spring from one another ; but the species among
them have only a relative constancy and are only invariable tem-
porarily.

Nevertheless, to facilitate the study and knowledge of so many
different bodies it is useful to give the name of species to any col-
lection of like individuals perpetuated by reproduction without change,
so long as their environment does not alter enough to cause varia-
tions in their habits, character and shape.

Of the Species Alleged to be Lost.

I am still doubtful whether the means adopted by nature to ensure
the preservation of species or races have been so inadequate that entire
races are now extinct or lost.

Yet the fossil remains that we find buried iii the soil in so many
different places show us the remains of a multitude of different animals
which have existed, and among which are found only a very small
number of which we now know any living analogues exactly alike.

Does this fact really furnish any grounds for inferring that the species
which we find in the fossil state, and of which no living individual
completely similar is known to us, no longer exist in nature ? There
are many parts of the earth's surface to which we have never pene-
trated, many others that men capable of observing have merely
passed through, and many others again, like the various parts of the
sea-bottom, in which we have few means of discovering the animals
living there. The species that we do not know might well remain
hidden in these various places. .

If there really are lost species, it can doubtless only be among the
large animals which live on the dry parts of the earth ; where man
exercises absolute sway, and has compassed the destruction of all
the individuals of some species which he has not wished to preserve
or domesticate. Hence arises the possibility that animals of the genera
Palaeotherium, Anoplothermm, Megalonix, MegatJierium, Mastodon,
of M. Cuvier, and some other species of genera previously known,

OF SPECIES 45

are no longer extant in nature : this however is nothing more than
a possibiHty.

But animals living in the waters, especially the sea waters, and
in addition all the races of small sizes Hving on the surface of the earth
and breathing air, are protected from the destruction of their species
by man. Their multiplication is so rapid and their means of evading
pursuit or traps are so great, that there is no likelihood of his being
able to destroy the entire species of any of these animals.

It is then only the large terrestrial animals that are liable to exter-
mination by man. This extermination may actually have occurred ;
but its existence is not yet completely proved.

Nevertheless, among the fossil remains found of animals which
existed in the past, there are a very large number belonging to animals
of which no hving and exactly similar analogue is known ; and among
these the majority belong to molluscs with shells, since it is only the
shells of these animals which remain to us.

Now, if a quantity of these fossil shells exhibit differences which
prevent us, in accordance with prevailing opinion, from regarding
them as the representatives of similar species that we know, does it
necessarily follow that these shells belong to species actually lost ? Why,
moreover, should they be lost, since man cannot have compassed their
destruction ? May it not be possible on the other hand, that the fossils
in question belonged to species still existing, but which have changed
since that time and become converted into the similar species that we
now actually find. The following consideration, and our observations
throughout this work, will give much probability to such an assumption.

Every quahfied observer knows that nothing on the surface of the
earth remains permanently in the same state. Everything in time
undergoes various mutations, more or less rapid according to the
nature of the objects and the conditions ; elevated ground is
constantly being denuded by the combined action of the sun, rain-
waters and yet other causes ; everything detached from it is carried
to lower ground ; the beds of streams, of rivers, even of seas change
in shape and depth, and shift imperceptibly ; in short, everything on
the surface of the earth changes its situation, shape, nature and appear-
ance, and even climates are not more stable.

Now I shall endeavour to show that variations in the environment
induce changes in the needs, habits and mode of life of living beings,
and especially of animals ; and that these changes give rise to modi-
fications or developments in their organs and the shape of their parts.
If this is so, it is difficult to deny that the shape or external characters
of every hving body whatever must vary imperceptibly, although
that variation only becomes perceptible after a considerable time.

46 ZOOLOGICAL PHILOSOPHY

Let us then no longer be astonished that among the numerous fossils
found in all the dry parts of the world, and constituting the remains
of so many animals which formerly existed, there are so few of which
we recognise the living representatives.

What we should wonder at, on the contrary, is finding amongst
these numerous fossil remains of once living bodies, any of which the
still existing analogues are known to us. This fact, proved by our
collections of fossils, suggests that the fossil remains of animals whose
living analogues we know are the least ancient fossils. The species
to which each of them belongs doubtless has not had time to undergo
variation.

Naturalists who did not perceive the changes undergone by most
animals in course of time tried to explain the facts connected with
fossils, as well as the commotions known to have occurred in different
parts of the earth's surface, by the supposition of a universal
catastrophe which took place on our globe. They imagined that
everything had been displaced by it, and that a great number of the
species then existing had been destroyed.

Unfortunately this facile method of explaining the operations of
nature, when we cannot see their causes, has no basis beyond the
imagination which created it, and cannot be supported by proof.

Local catastrophes, it is true, such as those produced by earth-
quakes, volcanoes and other special causes are well known, and we
can observe the disorder ensuing from them.

But why are we to assume without proof a universal catastrophe,
when the better known procedure of nature suffices to account for
all the facts which we can observe ?

Consider on the one hand that in all nature's works nothing is done
abruptly, but that she acts everywhere slowly and by successive
stages ; and on the other hand that the special or local causes of dis-
orders, commotions, displacements, etc., can account for everything
that we observe on the surface of the earth, while still remaining subject
to nature's laws and general procedure. It will then be recognised
that there is no necessity whatever to imagine that a universal
catastrophe came to overthrow everything, and destroy a great part
of nature's own works.

I have said enough on a subject which presents no difficulty. Let
us now consider the general principles and essential characters of
animals.

CHAPTER IV.

GENERAL PRINCIPLES CONCERNING ANIMALS.

Animals in general are living beings with very curious properties,
well calculated to astonish us and excite our study. These beings,
infinitely varied in shape, organisation, and faculties, are capable of
moving themselves or some of their parts without the impulse of any
movement from without. Their irritability is due to an exciting
cause which in some originates from within, while in others it comes
entirely from without. Most of them possess the property of loco-
motion, and all have parts that are highly irritable.

We find that in their movements some crawl, walk, run or leap ;
others fly, rising into the atmosphere and passing through wide spaces ;
others again five in the waters and swim about there freely.

Animals are not, Uke plants, able to find close by within their reach
the material on which they feed ; and the predatory animals are
actually obUged to go forth and to hunt, chase and seize their prey.
It was necessary therefore that they should have the power of motion
and even of locomotion, in order to procure the food which they
require.

Moreover, those among animals which multiply by sexual repro-
duction are not hermaphrodite enough to be sufficient to themselves.
Hence it was farther necessary that they should be able to travel
about for the purpose of effecting acts of fertilisation, and that the
environment should provide facilities for it to those which, like
oysters, cannot change their position.

Thus the needs of animals have endowed them with the property
of moving parts of their bodies, and of carrying out locomotion which
subserves their own survival and that of their races.

In Part II. we shall enquire into the origin of this extraordinary
faculty, as of the other important faculties found among them ;
but it suffices at present to draw attention to certain obvious
points.

48 ZOOLOGICAL PHILOSOPHY

(1) Some only move themselves or their parts when their irrita-
bility has been stimulated ; but they experience no feeling : these
are the most imperfect animals ;

(2) Others, in addition to the movements that their parts can
undergo through stimulated irritability are capable of experiencing
sensations, and possess a very vague inner feeling of their existence ;
but they only act by the internal impulse of an inclination which
leads them towards some or other object ; so that their will is always
dependent and controlled ;

(3) Others again not only exhibit in some of their parts movements
resulting from their stimulated irritability ; not only are they capable
of receiving sensations, and possess an inner feehng of their existence,
but they have besides the faculty of forming ideas, although confused
ones, and of acting by a free will, subject however to inclinations which
lead them exclusively towards certain special objects ;

(4) Finally, others (and these are the most perfect) possess in a
high degree all the aforementioned faculties ; in addition they are
able to form clear and precise ideas of the objects which aifect their
senses and attract their attention ; to compare and combine their
ideas up to a certain point ; to form judgments and complex ideas ;
in short to think, and to have a will that is less bound down and permits
them to introduce more or less variation into their activities.

Life in the most imperfect animals has no energy of movement ;
and irritabihty alone suffices for the execution of vital movements.
But since vital energy increases in proportion to complexity of organisa-
tion, there arrives a time when nature has to improve her methods
in order to provide for the necessary activity of vital movements ;
for this purpose she has utilised muscular activity in establishing the
circulatory system, so that the fluids can move with greater rapidity.
This rapidity itself is increased in proportion to the increase of the
muscular power which works it. Finally, since no muscular activity
can take place without nervous influence, this has become every-
where necessary for the acceleration of the fluids in question.

Thus nature has been able to add muscular activity and nervous
influence to an irritability which was no longer adequate. But this
nervous influence, which gives rise to muscular activity, never does
so by means of feeling, as I hope to show in Part II. I shall then
prove that sensibility is by no means necessary to the execution
of vital movements, even in the most perfect animals.

The various animals which exist are thus clearly distinguished
from one another, not only by peculiarities of external shape, con-
sistency of body, size, etc., but, in addition, by the faculties which
they possess. Some, such as the most imperfect, are extremely limited

GENERAL PRINCIPLES 49

in that respect, having no other faculty but those of life in general,
and being unable to move except by a power outside thera ; Avhile
others have faculties, progressively more numerous and important,
up to the most perfect animals, which exhibit a capacity calculated
to excite our wonder.

These remarkable facts no longer surprise us, when we recognise
that every faculty is based upon some special organ or system of organs,
and when we observe that organisation gradually becomes more
complex as we pass from the most imperfect animal, which has no
special organ whatever and consequently no faculty but those of
life in general, to the most perfect and richly endowed animal. Thus
all the organs, even the most important, arise one after the other in
the animal scale, and afterwards become successively more perfect
through the modifications impressed on them, by which these organs
come to harmonise with the state of organisation of which they are
part. Hence, by their combination in the most perfect animals,
they constitute the highest degree of organisation, giving rise to the
most numerous and important faculties.

The examination of the internal organisation of animals ; of the
various systems presented by that organisation in the animal scale ;
and, finally, of the special organs, is then the subject of study most
deserving of our attention.

If animals, considered as productions of nature, are rendered
extremely remarkable by their faculty of locomotion, a great many of
them are still more so by their faculty of feeling.

I have said that this faculty of locomotion is very limited in the most
imperfect animals, among which it is not voluntary and is only carried
out by external stimuli. It then becomes gradually more perfect
and ultimately takes its source within the animal itself, and becomes
at length subject to its will. In just the same way, the faculty of feeling
is still very obscure and limited in the animals among which it begins
to exist ; but it then develops gradually, and when it has reached its
highest development it ultimately gives rise in the animal to the
faculties which constitute intelligence.

Indeed the most perfect among animals have simple and even com-
plex ideas ; they have passions and memory and they dream, that is
to say, they experience involuntary recurrences of their ideas and
even of their thoughts ; and they are up to a certain point capable
of learning. How wonderful is this result of the power of nature !

Nature thus succeeds in endowing a living body with the faculty
of locomotion, without the impulse of an external force ; of perceiving
objects external to it ; of forming ideas by comparison of impres-
sions received from one object with those received from others ; of

50 ZOOLOGICAL PHILOSOPHY

comparing or combining these ideas, and of forming judgments which
are merely ideas of another order ; in short, of thinking. Not only is
this the greatest marvel that the power of nature has attained, but it
is besides a proof of the lapse of a considerable time ; since nature
has done nothing but by slow degrees.

As compared to the periods which we look upon as great in our
ordinary calculations, an enormous time and wide variation in successive
conditions must doubtless have been required to enable nature to bring
the organisation of animals to that degree of complexity and develop-
ment in which we see it at its perfection. If an inspection of the
numerous diverse strata composing the external crust of the earth
furnishes unimpeachable testimony of its great antiquity ; if the very
slow but continuous displacement of the sea-bottom,^ certified by the
numerous monuments left everywhere about, gives further confirmation
of its prodigious antiquity ; then the belief is justified that the state of
perfection at which the organisation of the most perfect animals has
arrived, contributes to exhibit that truth in the strongest possible light.

But in order that this new proof may be securely based, it will first
be necessary to bring into evidence the facts concerning the actual
progress of organisation ; it will be necessary to verify if possible
the reahty of that progress ; finally, it will be necessary to collect
the best established facts and to identify nature's methods in bring-
ing her productions into existence.

Meanwhile, let us note that although the term productions of nature
is generally accepted for indicating the beings which constitute each
kingdom, it seems none the less that no definite idea is attached to that
expression. Apparently, prejudices of special origin prevent the
recognition of the fact that nature possesses the faculty of herself
bringing so many different beings into existence ; of causing incessant
though very slow variations in living races ; and of maintaining
everywhere the general order that we observe.

Let us leave aside all opinion whatever on these great subjects ;
and to avoid any error of imagination let us everywhere consult
nature's own works.

In order to be able to bring under our attention the totahty of exist-
ing animals, and to place these animals under an aspect easily under-
stood, we must remember that all the natural productions that we can
observe have long been divided by naturalists into three kingdoms,
under the name of animal kingdom, vegetable kingdom and mineral
kingdom. By this division, the existences comprised in each of these
kingdoms are compared together under a common standard ; although
some have a very different origin from others.
' Hydrogéologie, p. 41 et seq.

GENERAL PRINCIPLES 51

For some time past I have found it more convenient to employ
another primary division which is better calculated to give an idea
of the beings dealt with. Thus, I distinguish the natural productions
comprised in the three aforementioned kingdoms into two main
branches :

1. Organised living bodies ;

2. Crude bodies without life.

Living beings, such as animals and plants, constitute the first of these
two branches of the productions of nature. They possess, as every-
one knows, the faculties of alimentation, development, reproduction,
and they are subject to death.

But what is not known so well, since the fashionable hypotheses
do not permit of the belief, is that Uving bodies form for themselves
their own substances and secretions, as a result of the activity and
functions of their organs and of the mutations wrought in them
by organic movements {Hydrogéologie, p. 112). What is still less
known is that the exuviae of these living bodies give rise to all the
composite matters, crude or inorganic, that are to be foimd in nature,
matters of which the various kinds increase in course of time and
according to the conditions, by reason of the disintegration which
they imperceptibly undergo. For this disintegration simplifies them
more and more, and after a long period leads to the complete
separation of their constituent principles.

These are the various crude and hfeless matters, both sohd and
liquid, which compose the second branch of the productions of
nature, and most of which are known under the name of minerals.

It may be said that an immense hiatus exists between crude matters
and living bodies, and that this hiatus does not permit of a linear
arrangement of these two kinds of bodies, nor of any attempt to
unite them by a link, as has been vainly attempted.

All known hving bodies are sharply divided into two special kingdoms,
based on the essential differences which distinguish animals from
plants ; and in spite of what has been said I am convinced that these
two kingdoms do not really merge into one another at any point,
and consequently that there are no animal-plants, as impUed by the
word zoophyte, nor plant-animals.

Irritability in all or some of their parts is the most general charac-
teristic of animals ; it is more general than the faculty of voluntary
movements and of feehng, more even than that of digestion. Now
all plants, as I have elsewhere shown, are completely destitute of
irritability, not even excepting the so-called sensitive plants nor those
which move certain of their parts on being touched or brought into
contact with the air.

52 ZOOLOGICAL PHILOSOPHY

It is known that irritability is a faculty essential to the parts or to
certain parts of animals, and that it is never suspended or annihilated
so long as the animal is alive and the part possessing it has suffered
no injury. Its effect is seen in a contraction which takes place
instantly throughout the irritable part on contact with a foreign
body ; a contraction which ends with its cause, and which is renewed
whenever the part after relaxation is irritated by new contacts. Now
nothing of this kind has ever been observed in any other part of
plants.

When I touch the extended branches of the sensitive plant {Mimosa
pudica), instead of a contraction I observe in the joints of the disturbed
branches and petioles a relaxation, which permits these branches and
petioles of the leaves to droop, and causes the leaflets themselves to
sink down upon one another. When once that sinking has been
produced it is useless to touch again the branches and leaves of this
plant ; no effect follows. A longish time is required, unless it is
very hot, for the distension of the joints of the small branches and
leaves of the sensitive plant ; when all these parts will again be raised
and spread out, ready to fall together once more upon a contact or
slight shaking.

I cannot see in this phenomenon any relation to the irritability
of animals. I reflected however that during growth, especially
when it is hot, there are produced in plants many elastic fluids,
part of which are incessantly being exhaled. Hence I conceived
that in leguminous plants these elastic fluids might accumulate,
especially in the joints of the leaves, before being dispelled, and that
they might then distend these joints and keep the leaves or leaflets
spread out.

In this case, the slow dissipation of the elastic fluids in question set
up in leguminous plants by the approach of night ; or the sudden
dissipation of the same fluid set up in Mimosa pudica by a slight shaking,
will give rise for leguminous plants in general to the phenomenon
known under the name of sleep, and for the sensitive plant to that
wrongly attributed to irritability.^

It follows from the observations which I shall set forth below, and
from the inferences which I have drawn from them, that in general

^ I have developed in another work (Hist. Nat. des végétaux, edition Détervillc,
vol. i. p. 202) other analogous phenomena ob.servcd in plants such as Hedysarum
girans, Dionaea muscipula, the stamens of the flowers of Berberis, etc. ; and 1 have
shown that the curious movements observed in the parts of certain plants chiefly
in hot weather are never the result of a real irritability essential to any of their fibres ;
but that they are sometimes hygrométrie or pyrometric effects, sometimes the results
of elastic relaxations which take place under certain circumstances, and sometimes
of a swelling and drooping of parts by the local accumulations and more or less rapid
dissipations of elastic and invisible fluids which are being exhaled.

GENERAL PRINCIPLES 53

it is not true that animals are sensitive creatures endowed without
exception with the power of producing acts of will, and consequently
with the faculty of voluntary locomotion. Hence the definition
of animals hitherto given to distinguish them from plants is altogether
unsuitable ; in consequence, I have already proposed to substitute
the following as more in harmony with the facts, and more suitable
to characterise the beings which compose the two kingdoms of living
bodies.

Definition of Animals.

Animals are organised living bodies, which have irritable parts
at all times of their lives ; which nearly all digest the food on which
they live ; and which move, some by acts of will, either free or
dependent, and others by stimulated irritability.

Definition of Plants.

Plants are organised living bodies whose parts are never irrit-
able, which do not digest or move either by will or true irritability.

We see from these definitions, which are much sounder and more
accurate than those hitherto received, that animals are primarily
distinguished from plants by the irritability which all or some of
their parts possess, and by the movements that they can produce
in these parts, or which are set up by external causes as a sequence
of their irritability.

It would doubtless be wrong to agree to these new ideas merely
on authority ; but I think that every unprejudiced reader who takes
into consideration the facts and observations which I shall set forth
in the course of the present work will be unable to deny them pre-
ference over the ancient ones for which I am substituting them ;
since the latter are obviously contrary to all observation.

We shall terminate this general outlook upon animals by two some-
what curious considerations : one concerning the extreme multiphcity
of animals on the surface of the earth and in the waters, the other
concerning the means adopted by nature to ensure that their number
shall never become injurious to the preservation of her productions
and of the general order which should exist.

Of the two kingdoms of living bodies that comprising the animals
appears much richer and more varied than the other : at the same
time it exhibits more wonderful phenomena in its organisation.

The surface of the earth, the waters, and to some extent even the air
are populated by an infinite multitude of diverse animals, the races
of which are so varied and numerous that a large proportion of them

54 ZOOLOGICAL PHILOSOPHY

will probably always evade our researches. This is rendered the more
likely since the enormous extent of water, its depth in many places,
and the prodigious fertihty of nature in the smallest species will doubt-
less be for all time an almost insuperable obstacle to the progress
of knowledge.

A single class of the invertebrate animals, such as insects for instance,
equals the entire vegetable kingdom in the number and diversity of
its contained objects. The class of polyps is apparently much more
numerous still, but we shall never be able to flatter ourselves that
we know all the animals which make it up.

As a result of the rapid multipUcation of the small species, and
particularly of the more imperfect animals, the multipUcity of in-
dividuals might have injurious effects upon the preservation of races,
upon the progress made in perfection of organisation, in short, upon
the general order, if nature had not taken precautions to restrain that
multipUcation within limits that can never be exceeded.

Animals eat each other, except those which live only on plants ;
but these are liable to be devoured by carnivorous animals.

We know that it is the stronger and the better equipped that eat
the weaker, and that the larger species devour the smaller. Neverthe-
less, individuals rarely eat others of the same race as themselves ;
they make war on different races.

The multipUcation of the small species of animals is so great, and
the succession of generations is so rapid, that these small species would
render the globe uninhabitable to any others, if nature had not set
a Umit to their prodigious multiphcation. But since they serve
as prey to a multitude of other animals, and since the duration of
their hfe is very short and they are killed by any fall of temperature,
their numbers are always maintained in the proper proportions for
the preservation of their own and other races.

As to the larger and stronger animals, they might well become
dominant and have bad effects upon the preservation of many other
races if they could multiply in too large proportions ; but their races
devour one another, and they only multiply slowly and few at a time ;
and this maintains in their case also the kind of equilibrium that
should exist.

Lastly, man alone, considered apart from all that is special to him,
seems to be able to multiply indefinitely, for his intelligence and powers
protect him from any hmit of multiplication due to the voracity of
any animal. He exercises a supremacy over them, so that instead of
having to fear the larger and stronger races of animals, he is capable
rather of extinguishing them, and he is continually keeping down
their numbers.

GENERAL PRINCIPLES 55

But nature has given him numerous passions which unfortunately
develop with his inteUigence, and thus set up a great obstacle to the
extreme multiphcation of individuals of his species.

It seems, in fact, that man is himself responsible for continually
keeping down the numbers of his kind ; for I have no hesitation in
saying that the earth will never be covered by the population that
it might support ; several of its habitable regions will always be
sparsely populated in turns, although the period of these fluctuations
are, so far as we are concerned, immeasurable.

By these wise precautions, everything is thus preserved in the
estabhshed order ; the continual changes and renewals which are
observed in that order are kept within limits that they cannot pass ;
all the races of living bodies continue to exist in spite of their variations ;
none of the progress made towards perfection of organisation is lost ;
what appears to be disorder, confusion, anomaly, incessantly passes
again into the general order, and even contributes to it ; everywhere
and always the will of the Subhme Author of nature and of everything
that exists is invariably carried out.

Before devoting ourselves to showing the degradation and simphfica-
tion existing in the organisation of animals, when we proceed according
to custom from the most complex to the simplest, let us examine
their true arrangement and classification, as well as the principles
employed for this purpose. It will then be easier for us to recognise
the proofs of the degradation in question.

CHAPTER V.

ON THE TRUE ARRANGEMENT AND CLASSIFICATION OF ANIMALS.

For the progress of zoological philosophy and the object that we have
in view, it is necessary to enquire into the true arrangement and
classification of animals ; to consider how such an arrangement
came about ; to ascertain what principles should be observed in set-
ting up that general arrangement ; and, finally, to investigate what
remains to be done in order to bring that arrangement into the closest
harmony with the actual order of nature.

But in order that our studies may be profitable, we must first deter-
mine the essential aims of an arrangement and of a classification of
animals ; for these two aims are very different in nature.

The aim of a general arrangement of animals is not only to possess
a convenient list for consulting, but it is more particularly to have an
order in that Ust which represents as nearly as possible the actual
order followed by nature in the production of animals ; an order con-
spicuously indicated by the afl&nities which she has set between them.

The aim of a classification of animals, on the other hand, is to furnish
points of rest for our imagination, by means of lines of demarcation
drawn at intervals in the general series ; so that we may be able
more easily to identify each race already discovered, to grasp its
affinities with other known animals, and to place newly discovered
species in their proper position. This device makes up for our own
shortcomings, facilitates our studies and our knowledge, and is
absolutely necessary for us ; but I have already shown that it is a
produce of artifice, and that despite appearances it corresponds to
nothing real in nature.

An accurate determination of afiinities between objects will always
begin by fixing in our general arrangements the place of the large
groups or primary divisions ; then that of the lesser groups, and lastly
that of the species or special races that have been observed. Now
here is the inestimable advantage accruing to science from a know-

ARRANGEMENT AND CLASSIFICATION 57

ledge of affinities. Since these affinities are the actual work of nature,
no naturaHst will ever be able or indeed desire to alter the consequences
of a recognised affinity. The general arrangement will thus become
ever more perfect and less arbitrary, according as our knowledge
of affinities becomes greater.

The case is different with classifications : that is to say, with the
various lines of demarcation that we have to draw at intervals in the
general list both of animals and plants. In truth, so long as there are
gaps remaining to be filled in our hst owing to many animals and plants
not having yet been observed, we shall always find these lines of
demarcation, which appear to be drawn by nature herself; but this
illusion will vanish as our observations accumulate. Have we not
already witnessed the effacement of a great number, at least in the
smaller divisions, by reason of the numerous discoveries of naturalists
during the last half century ? Except for the Unes of demarcation
resulting from gaps to be filled, those which we shall always have to
draw will be arbitrary and therefore changeable, so long as naturalists
do not adopt some conventional principle for their guidance.

In the animal kingdom such a principle is that every class should
comprise animals distinguished by a special system of organisation.
The strict execution of this principle is quite easy, and attended only
with minor inconveniences.

In short, although nature does not pass abruptly from one system
of organisation to another, it is possible to draw boundaries between
each system, in such a way that there is only a small number of animals
near those boundaries and admitting of doubt as to their true class.

The other lines of demarcation which sub-divide classes are usually
more difficult to establish, since they depend on less important
characters ; and for this reason are more arbitrary.

Before examining the true classification of animals, let me endeavour
to show that the list of living bodies should form a series, at least as
regards the main groups ; and not a branching net-work.

Classes should form a Series in the Arrangement
OF Animals.

Man is condemned to exhaust all possible errors when he examines
any set of facts before he recognises the truth. Thus it has been denied
that the productions of nature in each kingdom of hving bodies can
really be arranged in a true series according to their affinities ; and
that there exists any scale in the general arrangement either of animals
or plants.

Naturalists, for instance, have noticed that many species, certain
genera and even some families appear to a certain extent isolated

58 ZOOLOGICAL PHILOSOPHY

in their characters ; and several have imagined that the affinities
among living beings may be represented something after the manner
of the different points of a compass. They regard the small well-
marked series, called natural families, as being arranged in the form
of a reticulation. This idea, which some modern writers think sub-
lime, is clearly a mistake, and is certain to be dispelled when we have
a deeper and wider knowledge of organisation ; and especially when
the distinction is recognised between what is due to the influence
of environment and habits and what is due to the greater or less
progress in the complexity or perfection of organisation.

Meanwhile I shall show that nature, by giving existence in the course
of long periods of time to all the animals and plants, has really formed
a true scale in each of these kingdoms as regards the increasing com-
plexity of organisation ; but that the gradations in this scale, which
we are bound to recognise when we deal with objects according to
their natural affinities, are only perceptible in the main groups of the
general series, and not in the species or even in the genera. This
fact arises from the extreme diversity of conditions in which the various
races of animals and plants exist ; for these conditions have no relation
to the increasing complexity of organisation, as I shall show ; but they
produce anomalies or deviations in the external shape and characters
which could not have been brought about solely by the growing com-
plexity of organisation.

We have then only to prove that the series constituting the animal
scale resides essentially in the arrangement of the main gi'oups com-
posing it, and not in that of species, nor always even of genera.

The series to which I have alluded can then only be made out among
the larger groups ; since each of these groups, constituting the classes
and bigger famiUes, comprises beings whose organisation is dependent
on some special system of essential organs.

Thus each distinct group has its special system of essential organs ;
and it is these special systems which undergo a degradation as we pass
from the most complex to the simplest. But each organ taken by
itself does not proceed so regularly in its degradations : and less so
in proportion to its lesser importance and greater susceptibility to
modification by environment.

In fact, the organs that have httle importance or are not essential
to life are not always at the same stage of perfection or degradation ;
so that if we follow all the species of a class we shall see that some
one organ of any species reaches its highest degree of perfection,
while some other organ, which in that same species is quite un-
developed or imperfect, reaches in some other species a high state
of perfection.

ARRANGEMENT AND CLASSIFICATION 59

These irregularities in the perfection and degradation of inessential
organs are found in those organs which are the most exposed to the
influence of the environment ; this influence involves similar irregu-
larities in the shape and condition of the external parts, and gives
rise to so great and singular a diversity of species that, instead of being
arranged like the main groups in a single linear series as a regularly
graduated scale, these species often constitute lateral ramifications
around the groups to which they belong, and their extremities are
in reaUty isolated points.

A much more powerful and lasting set of conditions is necessary to
modify any internal system of organisation than to alter the external
organs.

I observe, however, that in cases of necessity nature passes from one
system to another without a break, if they are closely alhed ; it is
indeed by this faculty that she succeeded in fashioning them all in
turn, passing from the simplest to the most complex.

So true is it that she has this faculty, that she even passes from one
system to another not merely in two different alhed famiUes but in
one individual.

Those systems of organisation in which respiration is carried on by
true lungs are nearer to the systems requiring gills than to those requir-
ing tracheae ; thus, nature not only passes from gills to lungs in alUed
classes and famihes, as is seen among fishes and reptiles, but she does
so even during the existence of one individual : which possesses in
turn first one and then the other system. It is known that the frog,
in its imperfect condition of tadpole, breathes by gills ; while in its
more perfect condition of frog it breathes by lungs. But nowhere
does nature pass from the system of tracheae to the pulmonary
system.

It may then be truly said that in each kingdom of living bodies the
groups are arranged in a single graduated series, in conformity with the
increasing complexity of organisation and the affinities of the object.
This series in the animal and vegetable kingdoms should contain the
simplest and least organised of hving bodies at its anterior extremity,
and ends with those whose organisation and faculties are most perfect.

Such appears to be the true order of nature, and such indeed is
the order clearly disclosed to us by the most careful observation and
an extended study of all her modes of procedure.

We have seen the necessity of paying attention to the question of
affinities, in drawing up our arrangements of the productions of nature ;
hence we are no longer able to arrange the general series in any way
we hke. Our knowledge of nature's methods continues to increase
in proportion to our studies of the affinities between objects or various

60 ZOOLOGICAL PHILOSOPHY

groups of objects ; and this knowledge compels us to conform to her
order.

The first result obtained from the use of affinities in placing the group»
in a general scheme is that the two extremities of the order must be
occupied by the most dissimilar beings, since they are the most distant
from one another from the point of view of affinities, and consequently
of organisation. Hence it follows that if one of the extremities of
the order is occupied by the most perfect of living bodies, having the
most complex organisation, the other extremity of the order must
necessarily be occupied by the most imperfect of living bodies, namely,
those whose organisation is the simplest.

In the general arrangement of known plants according to the natural
methods, that is according to affinities, only one extremity is thoroughly
known ; and that is occupied by the cryptogams. If the other ex-
tremity is not determined with equal certainty, it is due to the fact
that our knowledge of plant organisation is much less advanced than
our knowledge of the organisation of a great number of known
animals. Hence it follows that in the case of plants we have as yet
no certain guide to the affinities between the large groups, as we have
to those among genera and famiUes.

The same difficulty does not exist in the case of animals, and both
extremities of their general series are thus definitely fixed ; for as long
as importance is attached to the natural method, and hence to
affinities, the mammals will of necessity occupy one extremity of
the order, while the infusorians will be placed at the other.

For animals then, as well as for plants, there exists in nature an
order arising, Hke the objects which it calls into existence, from powers
conferred by the Supreme Author of all things. Nature is herself
only the general and immutable order created everywhere by this
Sublime Author ; she is the sum total of the general and special laws
to which that order is subject. By these powers, which she continues
unchangeably to make use of, she has given and still continues to give
existence to her productions ; she is incessantly varying and renewing
them, and thus maintains everywhere the entire order which results.

We were obUged to recognise this order of nature in each kingdom
of living bodies ; and we are already in possession of various parts
of it, in our better constituted famiUes and genera. We shall now
see that in the animal kingdom it is established in its outUnes in a
way that leaves no scope for arbitrary opinion.

But the great number of divers animals that we have come to know,
and the brilUant light shed by comparative anatomy on their organisa-
tion, now place it in our power definitely to draw up the general Ust
of all known animals, and to assign definitely the rank of the main

ARRANGEMENT AND CLASSIFICATION 61

•divisions that may be established in the series which they constitute.
This it behoves us to recognise ; it would indeed be difficult to dispute.
Let us now pass to the actual arrangement and classification of
animals.

The Tkue Aerangement and Classification of Animals.

Since the purpose and principles both of a general arrangement
and of a classification of living animals were not at first perceived
when these subjects were studied, the works of naturalists long suffered
from this imperfection of our ideas. The same thing happened in
the science of natural history as has happened in all others to which
much attention was given, before any principles had been thought out
to constitute a basis and to guide their labours.

Instead of subjecting the classification which had to be made in
€ach kingdom of living bodies to an arrangement which should be quite
unfettered, attention was entirely devoted to disposing objects in
convenient classes, so that their arrangement" was thus abandoned
to arbitrary opinion.

The affinities among the larger groups in the vegetable kingdom,
for example, were very difficult to grasp ; and artificial systems were
long made use of in botany. They faciUtated the making of convenient
classifications based upon arbitrary principles, so that every author drew
up a new one according to his fancy. Thus the proper arrangement of
plants according to the natural method was then always sacrificed. It
is only since we have recognised the importance of the parts concerned
with fruiting, and the greater importance of some than others that the
general arrangement of plants began to make progress towards perfection.

As the case of animals is different, the general affinities which
characterise the main groups are much easier to perceive : so that
several of these groups were identified at the very beginning of the
study of natural history.

Aristotle indeed divided animals primarily into two main divisions
or, as he called it, two classes, viz. :

1. Animals that have blood :

Viviparous quadrupeds.
Oviparous quadrupeds.
Fishes.
Birds.

2. Animals that have no blood :

Molluscs.
Crustaceans.
Testaceans.
Insects.

62 ZOOLOGICAL PHILOSOPHY

This primary division of animals into two main groups was fairly
good, but the character taken by Aristotle for discrimination was
bad. That philosopher gave the name of blood to the chief fluid in
animals which has a red colour. He imagined that all animals which
he placed in his second class only possessed white or whitish fluids ;
and he thereupon regarded them as having no blood.

Such apparently was the first outUne of a classification of animals ;
it is at any rate the oldest of which we have any knowledge. But
this classification also furnishes the earUest example of an arrange-
ment, though in the opposite direction from the order of nature ; since
we may notice in it a progression, though a very imperfect one, from
the most complex to the simplest.

That erroneous direction has been generally followed ever since
in the arrangement of animals ; and this has clearly retarded our
knowledge of nature's procedure.

Modern naturahsts have endeavoured to improve upon Aristotle's
division by giving to the animals in the first class the name of red-
blooded animals, and to those in his second class that of white-blooded
animals. It is now well known how defective is this character ; since
there are some invertebrate animals (many annelids) which have
red blood.

In my opinion the essential fluids of animals do not deserve the name
of blood, except when they circulate in arteries and veins ; for the
other fluids are so degraded, and the combination of their principles
so imperfect, that it would be wrong to assimilate them to fluids which
have a true circulation. One might as well attribute blood to a plant
as to a radiarian or polyp.

In order to avoid ambiguity and hypothesis, I divided the entire
known animal world in my first course of lectures at the Museum
in the spring of 1794 (the year II. of the repubUc) into two perfectly
distinct groups, viz. :

Animals that have vertebrae.
Animals without vertebrae.

I called the attention of my pupils to the fact that the vertebral
column, among animals provided with it, indicates the possession
of a more or less perfect skeleton and of a plan of organisation on the
same plane ; whereas its absence among other animals not only
distinguishes them sharply from the first, but shows that their whole
plan of organisation is very diff'erent from those of vertebrate animals.

From Aristotle to Linnseus nothing of note appeared with regard
to the general arrangement of animals ; but in the course of last
century naturalists of the highest distinction made a large number
of special observations on animals, and especially on many inverte-

ARRANGEMENT AND CLASSIFICATION 63

brate animals. Some recorded their anatomy with greater or less
fulness, while others gave an accurate and detailed history of the
metamorphoses and habits of a great number of these animals ; as a
result of their valuable observations, we have become acquainted
with many facts of the greatest importance.

At length Linnaeus, a man of high genius and one of the greatest
of naturalists, after having marshalled the facts and taught us the
necessity for great accuracy in the determination of all kinds of
characters, gave us the following classification for animals.

He divided known animals into six classes, based upon three stages
or characters of organisation.

Classification of Animals, established by Linnaeus.
Classes. \ First Stage.

I. Mammals. J- Heart with two ventricles : blood red and

II. Birds. j warm.

III. Amphibians (Reptiles). ) Second Stage.

IV. Fishes, / Heart with one ventricle : blood red and cold.
V. Insects. ) Third Stage.

VI. Worms. j A cold serum (in place of blood).

Except for the inversion displayed by this arrangement as by all
others the four first divisions proposed are now definitely established,
and will henceforth always obtain the assent of zoologists as to their
position in the general series. For this we are primarily indebted to
the illustrious Swedish naturalist.

The case is different with regard to the two final divisions of the
arrangement in question ; they are wrong and very badly disposed.
Since they comprise the greater number of known animals of the
most varied characters, they should be more numerous. Hence it
has been necessary to re-constitute them and substitute others.

We have seen that Linnaeus, and the naturahsts who succeeded him,
gave very little attention to the necessity for increasing the number
of divisions among animals which have a cold serum in place of blood
(invertebrate animals), and whose characters and organisation are so
greatly varied. Hence they have divided these numerous animals
into two classes only, viz. insects and worms ; so that everything
which was not regarded as an insect, that is to say all invertebrate
animals that have not jointed legs, were referred without exception
to the class of worms. They placed the class of insects after the fishes,
and the worms after the insects. According to this arrangement of
Linnams, the worms constituted the final class of the animal kingdom.

These two classes are still maintained in the same order in all the
editions of the Sy sterna Naturae published subsequently to Linnaeus.
The essential vice of this arrangement, as regards the natural order of

64 ZOOLOGICAL PHILOSOPHY

animals, is obvious ; it cannot be denied that Linnaeus's class of worms
is a sort of chaos in which the most disparate objects are included.
Yet the authority of that savant carried so much weight among
naturahsts, that no one dared to change this monstrous class of worms.
With a view to bringing about some useful reform in this respect,
I suggested in my first course the following arrangement for inverte-
brate animals, which I divided not into two classes, but into five in
the following order.

Aerangement of Invertebrate Animals set forth
IN MY First Course.

L Molluscs ;

2. Insects ;

3. Worms ;

4. Echinoderms ;

5. Polyps.

These classes were then identical with some of the orders which
Bruguière had suggested in his arrangement of worms (which I did not
adopt), and with the class of insects as defined by Linnaeus.

The arrival of M. Cuvier in Paris however, towards the middle of
the year III. (1795), drew the attention of zoologists to the organisa-
tion of animals. I then saw with much satisfaction the conclusive
evidence which he produced in favour of the priority of rank accorded
to molluscs over insects in the general series. This I had already
impressed in my lessons ; but it had not been favourably received by
the naturalists of this capital.

The change which I had thus instituted, from a consciousness of the
inadequacy of the prevaihng arrangement of Linnaeus, was thoroughly
consolidated by M. Cuvier by the most definite facts, several of which, it
is true, were already known but had not attracted ourattention in Paris.

I took advantage of the light shed since his arrival by this savant
over every section of zoology, and particularly over invertebrate
animals which he called white-blooded animals. I then added in
turn new classes to my arrangement ; I was the first to establish
them ; but, as we shall see, such of those classes as were adopted were
only adopted reluctantly.

The personal interests of authors are doubtless a matter of complete
indifference to science, and also apparently to those who study it.
Nevertheless, a knowledge of the history of the changes imdergone
during the last fifteen years by the classification of animals is not
without its uses : the following are those which I have instituted.

First, I changed the name of my class of echinoderms to radiarians,
in order to unite with them the jelly-fishes and neighbouring genera.

ARRANGEMENT AND CLASSIFICATION 66

This class, notwithstanding its utility and inevitableness, has not yet
been adopted by naturalists.

In my course in the year VII. (1799) I established the class of
crustaceans. At that time M. Cuvier, in his Tableau des animaux,
p. 451, still included crustaceans with insects ; and although this
class is essentially distinct, yet it was not till six or seven years later
that a few naturalists consented to adopt it.

The following year, that is to say, in my course of the year VIII.
{1800)1 suggested the arachnids as a class by itself, easy and necessary to
distinguish. From that time its characters have constituted a sure indi-
cation of an organisation pecuhar to these animals ; for it is impossible
to beheve that they arose from an organisation exactly similar to the
insects. Insects undergo metamorphosis, propagate only once in the
course of their life, and have only two antennae, two eyes with facets and
six jointed legs; while the arachnids never undergo metamorphosis, and
exhibit various characters besides which differentiate them from insects.
This fact has since been partly confirmed by observation. Yet this class
of arachnids is still not admitted into any other work than my own.

M. Cuvier had discovered the existence of arterial and venous vessels
in various animals, which used to be confused under the name of
worms with other animals of very different organisation. I immediately
took this new fact into consideration for the improvement of my
classification ; and in my course in the year X. (1802) I established
the class of annelids, placing them after the molluscs and before the
crustaceans, as required by their organisation.

By giving a special name to this new class I was able to keep the
old name of worms for the animals which have always borne it, and
whose organisation was remote from the annelids. So I continued
to place the worms after the insects, and to distinguish them from the
radiarians and polyps with which they can never again be united.

My class of annelids, published in my lectures and in my Recherches
sur les corps vivants (p. 24), was several years before being admitted
by naturalists. For the last two years however this class has begun
to gain recognition ; but since it is held desirable to change the name of
it and to call it by the name of worms, they do not know what to do
with the worms properly so-called which have no nerves or circula-
tory system. In this difficulty they combine them with the class of
polyps, although their organisation is very different.

These instances of perfection at first attained in a classification,
then destroyed and subsequently re-established by the necessity of
things, are not rare in natural science.

Linnaeus in fact united several genera of plants which Tournefort
had formerly distinguished as in the case of Polygonum, Mimosa,

66 ZOOLOGICAL PHILOSOPHY

Justicia, Convallaria, and many others ; and now botanists are re-
establishing the genera which Linnaeus had destroyed.

Finally last year (in my course of 1807) I established among in-
vertebrate animals a new class — the tenth — that of infusorians ; because
after a careful examination of the characters of these imperfect animals,,
I was convinced that I had been wrong to place them with the polyps.

Thus, by continuing to collect facts from observation and from the
rapid progress of comparative anatomy, I instituted successively
the various classes which now compose my arrangement of inverte-
brate animals. These classes, to the number of ten, are arranged
in order from the most complex to the simplest as usual, viz. :

Classes of Invertebrate Animals.

Molluscs. Insects.

Cirrhipedes. Worms.

Annelids. Radiarians.

Crustaceans. Polyps.

Arachnids. Infusorians.

I shall show, when I come to deal with each of these classes, that
they constitute necessary groups, since they are based upon a study
of organisation ; and that although races may, nay must, exist near
the boundaries, half way between two classes, yet these groups are the
best attainable by artifice. They will therefore have to be recognised,
so long as the interest of science is our chief concern.

By adding to these ten classes into which the invertebrates are
divided, the four classes of vertebrate animals identified and deter-
mined by Linnaeus, we shall have a classification of all known animals
into the following fourteen classes, set out once more in the opposite
order to that of nature.

1. Mammals.

2. Birds.

3. Reptiles.

4. Fishes.

5. Molluscs.

6. Cirrhipedes.

7. Annelids.

8. Crustaceans.

9. Arachnids.

10. Insects.

11. Worms.

12. Radiarians.

13. Polyps.

14. Infusorians,

Vertebrate animals.

• Invertebrate animals.

ARRANGEMENT AND CLASSIFICATION 67

The above represents the true arrangement of animals, and also
the classes established among them.

We now have to examine a very important problem, which appears
never to have been fathomed nor discussed ; but the solution of which
is necessary ; it is this :

All the classes, into which the animal kingdom is divided, necessarily
form a series of groups arranged according to the increasing or decreas-
ing complexity of their organisation. In drawing up this series, ought
we to proceed from the most complex to the simplest, or from the
simplest to the most complex ?

We shall endeavour to give the solution of this problem in Chap.
VIII. which concludes this part ; but we must first examine a very
remarkable fact, most worthy of our attention, which may lead us
to a perception of nature's procedure, when bringing her diverse
productions into existence. I refer to that remarkable degradation of
organisation which is found on traversing the natural series of animals,
starting from the most perfect or the most complex towards the simplest
and most imperfect.

Although this degradation neither is nor can be finely graduated as
I shall show, it so obviously and universally exists in the main groups,
including even the variations, that it doubtless depends on some
general law which it behoves us to discover and consequently to
search for.

CHAPTER VI.

DEGRADATION AND SIMPLIFICATION OF ORGANISATION FROM
ONE EXTREMITY TO THE OTHER OF THE ANIMAL CHAIN,
PROCEEDING FROM THE MOST COMPLEX TO THE SIMPLEST.

Among the problems of interest for zoological philosophy, one of the
most important is that which concerns the degradation and simpli-
fication observed in animal organisation on passing from one extreme
to the other of the animal chain, from the most perfect animals to
those whose organisations are the simplest.

Now the question arises whether this is a fact that can be established ;
for, if so, it will greatly enUghten us as to nature's plan and will set
us on the way to discover some of her most important laws.

I here propose to prove that the fact in question is true, and that
it is the result of a constant law of nature which always acts with
uniformity ; but that a certain special and easily recognised cause
produces variations now and again in the results which that law
achieves throughout the animal chain.

We must first recognise that the general series of animals arranged
according to their natural affinities is a series of special groups which
result from the different systems of organisation employed by nature ;
and that these groups are themselves arranged according to the de-
creasing complexity of organisation, so as to form a real chain.

We notice then that except for the anomalies, of which we shall
ascertain the cause, there exists frpm one end to the other of this chain
a striking degradation in the organisation of the animals composing it,
and a proportionate diminution in the numbers of these animals'
facidties. Thus if the most perfect animals are at one extremity
of 41le chain, the opposite extremity will necessarily be occupied by
the simplest and most imperfect animals found in nature.

This examination at length convinces us that all the special organs
are progressively simplified from class to class, that they become
altered, reduced and attenuated httle by little, that they lose their

DEGRADATION OF ORGANISATION 69

local concentration if they are of the first importance, and that finally
they are completely and definitely extinguished before the opposite
end of the chain is reached.

As a matter of fact, the degradation of which I speak is not always
gradual and regular in its progress, for often some organ disappears
or changes abruptly, and these changes sometimes involve it in peculiar
shapes not related with any other by recognisable steps.

Often again some organ disappears and re-appears several times
before it is definitely extinguished. But we shall see that this could
not have been otherwise ; for the factor which brings about the pro-
gressive complexity of organisation must have had varied effects,
owing to its liabiUty to modification by a certain other factor acting
with great power. We shall however see that the degradation in
question is none the less real and progressive, wherever its effects
can be seen.

If the factor which is incessantly working towards compUcating
organisation were the only one which had any influence on the shape
and organs of animals, the growing complexity of organisation would
everywhere be very regular. But it is not ; nature is forced to submit
her works to the influence of their environment, and this environment
everywhere produces variations in them. This is the special factor
which occasionally produces in the course of the degradation that we
are about to exemphfy, the often curious deviations that may be
observed in the progression.

We shall attempt to set forth in full both the progressive degra-
dation of animal organisation and the cause of the anomalies in the
progress of that degradation, in the course of the animal series.

It is obvious that, if nature had given existence to none but aquatic
animals and if all these animals had always lived in the same cUmate,
the same kind of water, the same depth, etc., etc., we should then
no doubt have found a regular and even continuous gradation in the
organisation of these animals.

But the power of nature is not confined within such limits.
It first has to be observed that even in the waters she has estabUshed
considerable diversity of conditions : fresh-water, sea water, still or
stagnant water, running water, the water of hot cUmates, of cold
cUmates, and lastly shallow water and very deep water ; these provide
as many special conditions which each act differently on the animals
Uving in them. Now the races of animals exposed to any of these
conditions have undergone special influences from them and have
been varied by them all the while that their complexity of organisation
has been advancing.

After having produced aquatic animals of all ranks and having

70 ZOOLOGICAL PHILOSOPHY

caused extensive variations in them by the different environments
provided by the waters, nature led them httle by little to the habit
of living in the air, first by the water's edge and afterwards on all
the dry parts of the globe. These animals have in course of time
been profoundly altered by such novel conditions ; which so greatly
influenced their habits and organs that the regular gradation which
they should have exhibited in complexity of organisation is often
scarcely recognisable.

These results which I have long studied, and shall definitely prove,
lead me to state the following zoological principle, the truth of which
appears to me beyond question.

Progress in complexity of organisation exhibits anomalies here and
there in the general series of animals, due to the influence of environment
and of acquired habits.

An examination of these anomahes has led some to reject the obvious
progress in complexity of animal organisation and to refuse to recognise
the procedure of nature in the production of Uving bodies.

Nevertheless, in spite of the apparent digressions that I have just
mentioned, the general plan of nature and the uniformity of her pro-
cedure, however much she varies her methods, are still quite easily
distinguished. We have only to examine the general series of known
animals and to consider it first in its totality and then in its larger
groups ; the most unequivocal proofs will then be perceived of the
gradation which she has followed in complexity of organisation ; a
gradation which should never be lost sight of by reason of the afore-
mentioned anomalies. Finally, it will be noticed that whenever there
have been no extreme changes of conditions, that gradation is found to
be perfectly regular in various portions of the general series to which
we have given the name of families. This truth becomes still more
striking in the study of species ; for the more we observe, the more
difficult, complicated and minute become our specific distinctions.

The gradation in complexity of animal organisation can no longer
be called in doubt, when once we have given positive and detailed
proof of what we have just stated. Now since we are taking the
general series of animals in the opposite direction from nature's actual
order when she brought them successively into existence, this grada-
tion becomes for us a remarkable degradation which prevails from
one end to the other of the animal chain, except for the gaps arising
from objects which are not yet discovered and those which arise
from anomahes caused by extreme environmental conditions.

Let us now cast an eye over the complexity and totality of the animal
series, in order to estabUsh positively the degradation of organisation
from one extremity to the other ; let us consider the facts presented

DEGRADATION OF ORGANISATION 71

and let us then pass rapidly in review the fourteen classes of which
it is primarily composed.

The general arrangement of animals set forth above is unanimously
accepted as a whole by zoologists : who dispute only as to the boundaries
of certain classes. In examining it I notice a very obvious fact which
would in itself be decisive for my purpose ; it is as follows :

At one extremity of the series (that namely which we are accustomed
to consider as the anterior) we find the animals that are most perfect
from all points of view, and have the most complex organisation ;
while at the opposite extremity of the same series we find the most
imperfect that exist in nature — those with the simplest organisation
and to all appearances hardly endowed with animality.

This accepted fact, which indeed cannot be questioned, becomes
the first proof of the degradation which I propose to establish ; for
it is a necessary condition of it.

Another fact brought forward by an examination of the general
series of animals and furnishing a second proof of the degradation
prevailing in their organisation from one extremity to the other of
their chain, is the following :

The first four classes of the animal kingdom contain animals that
are in general provided with a vertebral column, while the animals of
all the other classes are absolutely destitute of it.

It is known that the vertebral column is the essential basis of the
skeleton, which cannot exist without it ; and that wherever there is a
vertebral column there is a more or less complete and perfect
skeleton.

It is also known that perfection of faculties is a proof of perfection
of the organs on which they rest.

Now although man may be above his rank on account of the extreme
superiority of his intelhgence as compared with his organisation,
he assuredly presents the type of the highest perfection that nature
could attain to : hence the more an animal organisation approaches
his, the more perfect it is.

Admitting this, I observe that the human body not only possesses
a jointed skeleton but one that is above all others the most complete
and perfect in all its parts. This skeleton stiffens his body, provides
numerous points of attachment for his muscles and allows him an
almost endless variation of movement.

Since the skeleton is a main feature in the plan of organisation of
the human body, it is obvious that every animal possessed of a skeleton
has a more perfect organisation than those without it.

Hence the invertebrate animals are more imperfect than the ver-
tebrate animals ; hence, too, if we place the most perfect animals

72 ZOOLOGICAL PHILOSOPHY

at the head of the animal kingdom, the general series exhibits a real
degradation in organisation ; since after the first four classes all
the animals of the following classes are without a skeleton and con-
sequently have a less perfect organisation.

But this is not all : Degradation may be observed even among
the vertebrates themselves ; and we shall see finally that it is found
also among the invertebrates. Hence this degradation follows from
the fixed plan of nature, and is at the same time a result of our follow-
ing her order in the inverse direction ; for if we followed her actual
order, if, that is to say, we passed along the general series of animals
from the most imperfect to the most perfect, instead of a degradation
in organisation we should find a grow^ng complexity and we should
see animal faculties successively increasing in number and perfection.
In order to prove the universal existence of the alleged degradation, let
us now rapidly run through the various classes of the animal kingdom»

MAMMALS.

Animals with mammae, four jointed limbs, and all the organs essential
to the most perfect animals. Hair on certain parts of the body.

Mammals {Mammalia, Lin.) should obviously be at one extremity
of the animal chain, viz. that which contains the most perfect animals
and the richest in organisation and faculties ; for among them alone
are found those with the most developed intelligence.

If perfection of faculties is a proof of that of the organs they are
based upon as I said above, all mammals (and they alone are truly
viviparous) must have the most perfect organisation, since it is agreed
that these animals have more intelligence, more faculties and a more
perfect set of senses than any others ; moreover their organisation
approaches most nearly to that of man.

Their organisation exhibits a body whose parts are stiffened by a
jointed skeleton, which is generally more complete in these animals
than in the three other classes of vertebrates. Most of them have four
articulated limbs appended to the skeleton ; and all have a dia-
phragm between the chest and abdomen ; a heart with two ventricles
and two auricles ; red warm blood ; free lungs, enclosed within the
chest, through which the blood passes before being driven to the other
parts of the body ; lastly, they are the only viviparous animals, for
they are the only animals in which the foetus although enclosed within
its membranes is always in communication with its mother and develops
at the expense of her substance, and in which the young feed for some
time after their birth on the milk of her mammae.

DEGRADATION OF ORGANISATION 73

It is then the mammals that must occupy the first rank in the animal
kingdom by virtue of their perfection of or<:;anisation and greatest
number of faculties [Recherches sur les corps vivants, p. 15). After
the mammals we no longer find a definitely viviparous reproduction,
nor lungs limited by a diaphragm to the chest and receiving all the
blood which has to be driven to the rest of the body, etc., etc.

Among the mammals themselves it is in truth not easy to distinguish
what is really due to degradation from what is the effect of environ-
ment, manner of life and long-established habits.

Nevertheless, traces of the general degradation of organisation
may be found even among them ; for those whose limbs are
adapted for grasping objects have a higher perfection than those whose
Umbs are adapted only for walking. It is among the former that
man is placed in respect of his organisation. Now it is clear that since
the organisation of man is the most perfect, it should be regarded
as the standard for judging of the perfection or degradation of the
other animal organisations.

Thus the three divisions, into which the class of mammals is unequally
broken up, exhibit among themselves, as we shall see, a conspicuous
degradation in the organisation of the animals they contain.

First division : nnguiculate mammals ; they have four limbs, flat
or pointed claws at the end of their digits but not investing them.
These limbs are in general adapted for grasping objects or at least
for hooking on to them. It is among these that the animals with
the most perfect organisation are found.

Second division : ungulate mammals ; they have four limbs and
the extremity of their digits is completely invested by a rounded
horn called a hoof. Their feet serve no other purpose than that of
walking or running on the ground, and cannot be employed either
for cUmbing trees, or for grasping any object or prey, or for attack-
ing and rending other animals. They feed exclusively on vegetable
substances.

Third division : exungulafe mammals ; they have only two limbs
and these limbs are very short, flat and shaped like fins. Their digits
are invested by skin and have no claws or horn. Their organisation
is the least perfect of all mammals. They have no pelvis, nor hind
feet ; they swallow without previous mastication ; finally they
habitually live in the water ; but they come to the surface to breathe
air. They have received the name of cetaceans.

Although the amphibians also live in the water, coming out of it
occasionally to crawl upon the shore, they really belong to the first
division in the natural order, and not to that which comprises the
cetaceans.

74 ZOOLOGICAL PHILOSOPHY

Henceforth we have to distinguish the degradation of organisation
which arises from the influence of environment and acquired habits,
from that which results from the smaller progress in the perfection or
complexity of organisation. We must be careful therefore about going
into too much detail in this respect ; because as I shall show the environ-
ment in which animals habitually live, their special habitats, the habits
which circumstances have forced upon them, their manner of life, etc.,
have a great power to modify organs ; so that the shapes of parts
might be attributed to degradation when they are really due to other
causes.

It is obvious for example that the amphibians and cetaceans must
have greatly shortened limbs, since they live habitually in a dense
medium where well-developed limbs would only impede their move-
ments. It is obvious that the influence of the water alone must
have made them such as they are, by interfering with the movements
of very long limbs with solid internal parts ; and that consequently
these animals owe their general shape to the influence of the medium
they inhabit. But with regard to that degradation which we are
seeking among the mammals themselves, the amphibians must
be far removed from the cetaceans because their organisation is much
less degraded in its essential parts. Amphibians then have to be joined
to the unguiculate mammals, while the cetaceans should form the last
order of the class, as being the most imperfect mammals.

We now pass to the birds ; but I must first note that there is no
gradation between mammals and birds. There exists a gap to be filled,
and no doubt nature has produced animals which practically fill this
gap, and which must form a special class if they cannot be comprised
either among the mammals or among the birds.

This fact has just been realised, by the recent discovery in Australia
of two genera of animals, viz. :

Tj, 1 . n !■ Monotremes (Geoff.).

These animals are quadrupeds with no mammae, with no teeth
inserted and no hps ; and they have only one orifice for the genital
organs, the excrements and the urine (a cloaca). Their body is covered
with hair or bristles.

They are not mammals, for they have no mammae and are most
likely oviparous.

They are not birds ; for their lungs are not pierced through and
they have no limbs shaped as wings.

Finally, they are not reptiles ; for their heart with only two ven-
tricles removes them from that category.

They belong then to a special class.

DEGRADATION OF ORGANISATION 75

BIRDS.

Animals without mammae, with two feet and two arms shaped as wings ;
the body covered with feathers.

The second rank clearly belongs to the birds ; for while we do not
find among these animals so many faculties or so much intelhgence
as among the animals of the first rank, they are the only ones except
the monotremes which have like mammals a heart with two ventricles
and two auricles, warm blood, the cavity of the cranium completely
filled by the brain, and the trunk always enclosed by ribs. They have,
then, qualities common to mammals, but not found elsewhere ; and
consequently affinities with them that are not to be found in any
animals of the posterior classes.

But the birds when compared with the mammals display an obvious
degradation of organisation which has nothing to do with the influ-
ence of the environment. They are for instance naturally devoid of
mammae, organs with which only animals of the highest rank are
provided and which belong to a system of reproduction that is no
longer found in the birds nor in any of the animals of subsequent
ranks. In short they are essentially oviparous ; for the system
of truly viviparous animals, which is adapted to animals of the first
rank, is not found in the second nor does it again re-appear. Their
foetus is enclosed in an inorganic envelope (the egg-shell) and soon
ceases commimication with the mother and can develop without
feeding on her substance.

The diaphragm, which among mammals completely separates some-
what obhquely the chest from the abdomen, here ceases to exist, or
becomes very incomplete.

The vertebrae of the neck and tail are the only mobile parts in the
vertebral column of birds. Since movements of the other vertebrae
of that column are not necessary to the animal, they are not performed
and they thus place no obstacle to the large development of the
sternum which now makes such movement almost impossible.

The sternum of birds indeed gives attachment to the pectoral
muscles, which have become very thick and strong by reason of their
energetic and almost continuous movements. The sternum has thus
become extremely large and carinate in the middle. This, however,
is due to the habits of these animals and not to the general degra-
dation that we are investigating. The truth of this is exemphfied by
the fact that the mammal called a bat has also a carinate sternum.
AU the blood of birds passes through their lungs before reaching
the other parts of the body. Thus they breathe exclusively by lungs

76 ZOOLOGICAL PHILOSOPHY

like the animals of the first rank ; and this is not the case with any
known animal after them.

We now come to a very strange peculiarity which is connected
with the environment of these animals. They live more than other
vertebrates in the air, and are almost continually rising into it and pass-
ing through it in every direction. They have adopted a habit of swelling
their lungs with air in order to increase their volume and make them-
selves lighter ; and this habit has caused the organ to adhere to the
sides of the chest so that the air within, being rarefied by the heat
of the place, has had to pierce through the lung with its investing
membranes and to penetrate every part of the body even to the inside
of the great bones which are hollow, and to the quills of the large
feathers.^ It is, however, only in the lungs that the blood of birds
undergoes the necessary influence of the air ; for the air which
penetrates to the other parts of the body has another use than that
of respiration.

Thus the birds, which have been rightly placed after the mammals,
exhibit an obvious degradation in their general organisation : not
because their lung has a peculiarity not found among the former,
for this is due like their feathers only to their acquired habit of launch-
ing themselves into the air ; but because they no longer have the
system of reproduction proper to the most perfect animals, but only
that which characterises most of the animals of the posterior classes.

It is very difficult to ascertain among the birds themselves the
degradation of organisation which we are now studying ; our know-
ledge of their organisation is still too vague. Hence it has hitherto
been a matter of convention which order should be placed at the head
of this class and which at the end.

We may reflect however that aquatic birds (like the palmipeds),
as also the waders and gallinaceans, have this advantage over all
other birds that their young on coming out of the egg can walk and
feed. We may pay special attention to the fact that among the pal-
mipeds, the penguins and king-penguins, whose almost featherless
wings are merely oars for swimming and of no use for flight,

^ If it is true tliat in the case of birds the hings are pierced througli and the hair
changed into feathers as a result of their habit of rising into the air, 1 may be asked
why bats have not also feathers and pierced lungs. I re])ly that it seems to me pro-
bable that bats, which have a more perfect organisation than birds, and hence a
complete diajihragin to impede the swelling of tlicir lungs, have not been able to
pierce them through nor to swell themselves out with air sufficiently for that tluid
even by an effort to reach the skin and so to give to the horny matter of the hair
the faculty of branching out into featiiers. Among birds, in fact, air is introduced
as far as the hair l)ull)s ; changing their bases into quills and compelling this same
hair to break up into feathc^rs ; an event which -cannot occur in the bat, where tht*
air does not penetrate beyond the lung.

DEGRADATION OF ORGANISATION 77

thus approximate in some ways to the monotremes and cetaceans.
We shall then recognise that the palmipeds, waders, and galUnaceans
should constitute the first three orders of birds, and that the doves,
passerines, birds of prey and chmbers should form the last four orders
of the class. Now, from what we know of the habits of the birds
of these last four orders, we find that their young on coming out of
the egg can neither walk nor feed by themselves.

On this principle the climbers are the last order of birds ; more-
over, they are the only ones which have two posterior digits and two
anterior. This character, which they possess in common with the
chameleon, appears to justify us in placing them near the reptiles.

REPTILES.

Animals with only one ventricle in the heart and still possessing a pul-
monary respiration though incomplete. Their skin is smooth or
provided with scales.

In the third rank are naturally and necessarily placed the reptiles ;
and they will furnish us with new and stronger proofs of the degrada-
tion of organisation from one extremity of the animal chain to the
other, starting from the most perfect animals. In fact, their heart,
which has only one ventricle, no longer displays that conformation
which belongs essentially to animals of the first and second ranks,
and their blood is cold, almost like that of the animals of the posterior
ranks.

We find another proof of the degradation of the organisation of reptiles
in their respiration. In the first place they are the last animals to
breathe by true lungs ; for after them we find no respiratory organ
of this nature in any of the succeeding classes, as I shall endeavour
to show when speaking of molluscs. Next, the lung has in their case
usually very large chambers, proportionally less numerous, and is
already much simplified. In many species this organ is absent in
youth and is then replaced by gills, a respiratory organ which is never
found in animals of the anterior ranks. Sometimes the two kinds
of respiratory organs are present together in the same individual.

But the strongest proof of degradation in the respiration of reptiles
is that only part of their blood passes through the lungs, while the rest
reaches the parts of the body without having undergone the influence
of respiration.

Finally, among reptiles the four limbs essential to the most perfect
animals begin to be lost, and indeed many of them (nearly all the
snakes) lack them altogether.

78 ZOOLOGICAL PHILOSOPHY

Independently of the degradation of organisation indicated by the
shape of the heart, by the temperature of the blood which scarcely
arises above the level of the environment, by the incomplete respira-
tion and by the almost regular simpUfication of the lung, it is found
that reptiles differ considerably among themselves ; so that there are
greater differences of organisation and external shape among the
animals of the various orders of this class than among those of the
two preceding classes. Some habitually live in the air, and of these,
such as have no legs can only crawl ; others live in the water or on
its banks, sometimes withdrawing into the water and sometimes
going into open places. There are some that are clothed in scales
and others that have a naked skin. Lastly, although they all have a
heart with one ventricle, in some there are two auricles, while in
others there is only one. All these differences are due to environment,
manner of life, etc. ; conditions which doubtless act more strongly
upon an organisation that is still remote from the goal to which nature
is tending, than they could do on one more advanced towards per-
fection.

Reptiles are oviparous animals (including even those in which
the eggs are hatched in the body of the mother) ; their skeleton is
modified and usually very degraded ; their respiration and circulation
are less perfect than those of mammals and birds ; and they all
have a small brain which does not fill the cavity of the cranium.
Hence they are less perfect than the animals of the two preceding
classes, and in their turn confirm the fact that the degradation
of organisation increases, according as we approach the most
imperfect animals.

Within this class of animals themselves, independently of the modi-
fications in their parts due to environment, we find in addition traces
of the general degradation of organisation ; for in the last of their
orders (the batrachians) the individuals, when they are first born,
breathe by gills.

If the absence of legs observed among snakes were regarded as a
result of degradation, the ophidians ought to be the last order of
reptiles ; but it would be a mistake to suppose this. The fact is that
snakes are animals which for purposes of concealment have adopted
the habit of crawUng directly on the ground, and their body has thus
acquired a considerable length, out of proportion to its size. Now
elongated legs would have impeded their efforts in crawhng and
concealing themselves ; while very short legs, of which there could
only be four since these animals are vertebrates, would have been
incapable of moving their body. Thus the habits of these animals
have caused the disappearance of their legs ; although the batrachians.

DEGRADATION OF ORGANISATION 79

which have legs, are more degraded in organisation and nearer to the
fishes.

The proofs of the important principle which I am stating will be
based upon positive facts ; they will consequently always hold good
in contact with the arguments that are brought against them.

FISHES.

Animals breathing by gills, with a smooth or scaly skin ; the body
^provided with fins.

On following the course of that degradation undergone by organisa-
tion as a whole and of the diminution in the number of animal faculties,
we see that the fishes must of necessity be placed in the fourth rank,
that is, after the reptiles. Their organisation in fact is even less
advanced towards perfection than is that of reptiles, and is conse-
quently more remote from that of the most perfect animals.

It is true no doubt that their general shape, the absence of a con-
striction between the head and body to form a neck, and the various
fins which for them take the place of limbs, are results of the influence
of the dense medium they inhabit, and not of the degradation of
organisation. But that degradation is none the less real and very
great, as we may convince ourselves by an examination of their
internal organs ; so that we are forced to assign to fishes a lower
rank than to reptiles.

We no longer find in them the respiratory organ of the most perfect
animals ; for they have no true lung, and in its place have only gills
or vascular pectinate folds arranged on both sides of the neck or head,
four altogether on each side. The water which these animals breathe
goes in by the mouth, passes between the folds of the gills, and bathes
the numerous vessels which run there. Now since the water is mixed
with air or contains it in solution, that air although small in quantity
acts upon the blood of the gills and there achieves the function of
respiration. The water then issues through open holes on either
side of the neck.

Note that this is the last time that the respired fluid enters by the
animal's mouth in order to reach the organ of respiration.

These animals, like those of the posterior ranks, have no trachea
or larynx or true voice (including even those called grondeurs ^)
or eyehds, etc. These organs and faculties are here lost and are not
again found throughout the animal kingdom.

Yet the fishes are still part of the division of vertebrate animals ;
1 [The Grey Gurnard. H.E.]

80 ZOOLOGICAL PHILOSOPHY

but they are the last of them and they terminate the fifth stage of
organisation, being in common with reptiles the only animals which have:

A vertebral column ;

Nerves, terminating in a brain, which does not fill the cranium ;

A heart with one ventricle ;

Warm blood ;

Lastly, a completely internal ear.
Fishes thus display an oviparous reproduction ; a body without
mammae, of a shape adapted for swimming ; fins which are not
all invariably analogous with the four limbs of the most perfect
animals ; a very incomplete skeleton curiously modified and rudi-
mentary in the last animals of this class ; only one ventricle in the heart
and cold blood ; gills instead of lungs ; a very small brain ; the sense
of touch incapable of giving knowledge of the shapes of bodies ; and
apparently without any sense of smell, for odours are only conveyed
by air. It is clear that these animals strongly confirm in their turn
also the degradation of organisation that we have undertaken to
follow throughout the animal kingdom.

We shall now see that fishes are primarily divided into what are
called bony fishes, which are the most perfect of them, and cartilaginous
fishes, which are the least perfect. These two facts confirm the de-
gradation of organisation within the class itself; for among the
cartilaginous fishes the softness and cartilaginous condition of the
parts intended to stiffen their bodies and aid their movements
indicate that it is among them that the skeleton ends or rather that
nature has sketched its first rudiments.

By continually following the order of nature in the inverse direction,
the eight last genera of this class should include the fishes whose
branchial apertures have no operculum or membrane and are nothing
but holes at the sides or under the throat ; finally the lampreys and
hag-fishes should terminate the class, for these fishes differ greatly
from all others by the imperfection of their skeleton and in having a
naked slimy body without lateral fins, etc.

Observations on the Vertebrates.

The vertebrate animals, although differing greatly from one another
as regards their organs, appear to be all formed on a common plan
of organisation. On passing from the fishes to the mammals, we find
that this plan becomes more perfect from class to class and that it
only reaches completion in the most perfect mammals ; but we may
also notice that this plan while approaching perfection has undergone
numerous modifications, some of them very large, through the influence
of the environment of the animals and of the habits which each

DEGRADATION OF ORGANISATION 81

race has been forced to contract by the conditions in which it is
placed.

Hence we see, on the one hand, that if vertebrates differ markedly
from one another in their organisation, it is because nature only started
to carry out her plan in their respect with the fishes ; that she made
further advances with the reptiles ; that she carried it still nearer
perfection with the birds, and that finally she only attained the end
with the most perfect mammals.

On the other hand, we cannot fail to recognise that if the perfection
of the plan of organisation of the vertebrates does not everywhere
show a regular and even gradation from the most imperfect fishes
to the most perfect mammals, the reason is that nature's work has
often been modified, thwarted and even reversed by the influence
exercised by very different and indeed conflicting conditions of hfe
upon animals exposed to them throughout a long succession of
generations.

Annihilation of the Vertebral Column.

On reaching this point in the animal scale the vertebral column
becomes entirely annihilated. Since this column is the basis of
every true skeleton, and since this bony framework is an important
part of the organisation of the most perfect animals, it follows that all
the invertebrate animals, which we are about to investigate in turn,
must have an organisation still more degraded than that of the four
classes that we have just passed in review. Henceforth, therefore,
the supports for muscular activity will no longer reside in any internal
parts.

Moreover, none of the invertebrate animals breathes by cellular
lungs ; none of them has any voice nor consequently any organ
for this faculty ; finally they mostly appear devoid of true blood,
that is to say, of that fluid which in the vertebrate is essentially red,
but which only owes its colour to the intensity of their animalisation,
and proves especially a real circulation. How grave an abuse of words
it would be to give the name of blood to the thin and colourless fluid
which moves slowly through the cellular substance of the polyps !
We might as well apply the name to the sap of plants.

Besides the vertebral column, we also lose here the iris which is
characteristic of the eyes of the most perfect animals ; for such of the
invertebrates as have eyes have no distinct irises.

Kidneys in the same way are only found among the vertebrates,
and fishes are the last animals where this organ is met with. Hence-
forward there is no more spinal cord, no more great sympathetic
nerve.

82 ZOOLOGICAL PHILOSOPHY

A final very important observation is that among vertebrates, and
especially in the neighbourhood of that extremity of the animal scale
where the most perfect animals are found, all the essential organs
are isolated or have each an isolated seat in as many special places.
We shall soon see that the complete contrary holds good according
as we approach the other extremity of the scale.

It is then obvious that all the invertebrate animals have a less
perfect organisation than any of those which possess a vertebral
column ; while the organisation of mammals is that which from all
aspects includes the most perfect animals and is beyond question
the true type of the highest perfection.

Let us now enquire whether the classes and large families into
which the long series of invertebrate animals is divided also exhibit,
when we compare them together, an increasing degradation in the
complexity and perfection of their organisation.

INVERTEBRATE ANIMALS.

On reaching invertebrate animals we enter upon an immense series
of diverse creatures, the most numerous of any existing in nature,
the most curious and interesting with regard to the variations observed
in their organisation and faculties.

On observing their condition, we are convinced that in bringing
them successively into existence, nature has proceeded gradually
from the simplest to the most complex. Now since the purpose
in view has been to attain a plan of organisation which should admit
of the highest perfection (that of the vertebrates) — a plan very
different from those which nature had hitherto used to reach this point
— we may be sure that among these numerous animals we shall not
meet with a single system of organisation progressively perfected,
but with various quite distinct systems, each one taking its start
at the point where each organ of highest importance began to exist.

For instance, when nature attained to the creation of a special organ
for digestion (as in the polyps) she then gave for the first time a special
constant shape to the animals provided with it ; seeing that the in-
fusorians with which she began everything could not possess either
the faculty endowed by this organ, or the kind of shape and organisa-
tion favourable to its functions.

She subsequently established a special organ for respiration, and
in proportion as she varied this organ in order to perfect it and to
accommodate it to the animal's environment, she diversified their
organisation, in so far as the existence and development of the other
special organs rendered it necessary.

DEGRADATION OF ORGANISATION 83

When afterwards she succeeded in producing the nervous system,
it then immediately became possible to create the muscular system.
Thereupon, fixed points for the attachments of the muscles became
necessary, and also paired parts so as to constitute a symmetrical
shape. Hence have resulted various schemes of organisation due to
the environment and to the parts acquired, which could not previously
have come about.

When finally she secured sufficient movement in the contained
fluids of the animal to permit a circulation to be organised, there
again resulted important peculiarities of organisation which dis-
tinguished it from the organic systems in which there is no
circulation.

In order to perceive the truth of what I have stated and to furnish
evidence of the degradation and simplification of organisation (since
we are following the order of nature in the inverse direction) let us
rapidly run through the various classes of invertebrate animals.

MOLLUSCS.

Soft unjointed animals which breathe by gills and have a mantle. No
ganglionic longitudinal cord ; no spinal cord.

The fifth rank, as we descend the graduated scale of the animal
series, necessarily belongs to the molluscs ; for they have to be placed
a stage lower than the fishes since they have no vertebral column,
but they are yet the most highly organised of invertebrate animals.
They breathe by gills, which vary greatly not only in their shape and
size, but in their position within or without the animal according
to the genera, and the habits of the races comprised in these genera.
They all have a brain ; nerves without nodes, that is to say, without
a row of ganglia stretching down a longitudinal cord. They have
arteries and veins and one or several single-chambered hearts. They
are the only known animals which, although possessing a nervous
system, have neither a spinal cord, nor a gangUonic longitudinal
cord.

Gills, which are essentially intended by nature to carry out re-
spiration during immersion in the water, have been subjected to modi-
fication both in function and shape in those aquatic animals which
have been constantly exposed for generations to contact with the air,
and even in some cases have stayed in it altogether.

The respiratory organ of these animals has imperceptibly become
accustomed to the air ; and this is no mere supposition : for it is known
that all the crustaceans have gills and yet there are crabs {Cancer

84 ZOOLOGICAL PHILOSOPHY

ruricola) which habitually live on land and breathe air quite naturally
with their gills. Eventually this habit of breathing air with gills
became a necessity to many molluscs which acquired it : it even
modified the organ in such a way that the gills of these animals,
having no further need for so many points of contact with the respired
fluid, became adherent to the walls of the cavity which contains
them.

As a result we may distinguish among molluscs two kinds of
gills.

The first kind consist of networks of vessels running through the
skin of an internal cavity which is not protruded and can only breathe
air : these may be called aerial gills.

The second kind are organs nearly always protruded either within
or without the animal and forming fringes or pectinate lamellae or
edgings, etc. : these can only achieve respiration by means of the
contact of fluid water, and may be called aquatic gills.

If the differences in the habits of animals produce differences in their
organs, it will be useful in describing the special characters of certain
orders of molluscs to distinguish those which have aerial gills from
those whose gills can only breathe water ; but in any case they are
always gills and it appears to us quite improper to say that the molluscs
which breathe air possess a lung. How often the abuse of words
and wrong applications of names have served to distort objects and
lead us into error !

After all, is the difi'erence so great between the respiratory organ
of Pneumoderma, which consists in a vascular network running over
an external skin, and the vascular network of snails, which runs over
an internal skin ? Yet Pneumoderma appears to breathe nothing but
water.

Let us further enquire for a moment if there are any affinities between
the respiratory organ of air-breathing molluscs and the lung of verte-
brates.

A lung is essentially a peculiar spongy mass composed of more
or less numerous cells into which air is always entering in nature.
The entrance is effected through the animal's mouth and thence by a
more or less cartilaginous canal called the trachea, which usually
sub-divides into branches known as bronchi, culminating in the cells.
The cells and bronchi are alternately filled and emptied of air by
successive swellings and shrinkings of the cavity of the body contain-
ing the mass ; so that distinct alternate inspirations and expirations
are characteristic of a lung. This organ can only tolerate the contact
of air and is highly irritated by water or any other material. It is
therefore different in character from the branchial cavity of certain

DEGRADATION OF ORGANISATION 85

molluscs, which is quite peculiar, exhibits no alternate swelling and
shrinking, never has a trachea or bronchi and in which the respired
fluid never enters by the animal's mouth.

A respiratory cavity which has neither trachea nor bronchi nor
alternate swelhng and shrinking, and in which the respired fluid
does not enter by the mouth, and which is adapted either for air or
water, cannot be a lung. To confuse such different things by the
same name is not to advance science but to retard it.

The lung is the only respiratory organ that can give the animal
the faculty of having a voice. After the reptiles no animal has a
lung ; nor therefore a voice.

I conclude that it is not true that there are molluscs which breathe
by lungs. If some in nature breathe air, so also do certain crustaceans
and all insects ; but none of these animals has true lungs, unless the
same name is to be given to very different objects.

The molluscs also furnish proof of the progressive degradation that
we are investigating in the animal chain ; for theirgeneral organisation
is less perfect than that of fishes. But it is not so easy to recognise
the same degradation among the molluscs themselves ; for it is difficult
to distinguish in so numerous and varied a class what is due to the
degradation in question, from what is caused by the environment
and habits of these animals.

The only two orders into which the large class of molluscs is
divided, are strongly contrasted by the importance of their dis-
tinctive characters. The animals of the first of these orders (cephalic
molluscs) have a very distinct head, eyes, jaws or a proboscis and
reproduce by copulation.

All the molluscs of the second order (acephalic molluscs) on the con-
trary are destitute of a head, eyes, jaws, proboscis ; and they never
copulate for the purpose of reproduction.

Now it can hardly be denied that the second order of molluscs
is inferior to the first as regards perfection of organisation.

It is important, however, to remember that the absence of head,
eyes, etc., in the acephalic molluscs is not wholly due to the general
degradation of organisation, since we find again at lower stages of
the animal chain, animals which have a head, eyes, etc. We have here
again apparently one of those deviations in the progress of perfection
of organisation that are produced by environment, and consequently
by causes foreign to those which make for a gradual increase of com-
plexity in animal organisation.

When we come to consider the influence of the use of organs and of
an absolute and permanent disuse, we shall see that a head, eyes,
etc. , would in fact have been of very little use to molluscs of the second

86 ZOOLOGICAL PHILOSOPHY

order, because the large development of their mantle would have
prevented the functioning of these organs.

In conformity with that law of nature which requires that every
organ permanently disused should imperceptibly deteriorate, become
reduced and finally disappear, the head, eyes, jaws, etc., have in fact
become extinct in the acephalic molluscs : we shall see elsewhere
many other examples of the same thing.

In the invertebrates nature no longer finds in the internal parts
any support for muscular movement ; she has therefore supphed
the molluscs with a mantle for that purpose. Now the strength and
compactness of this mantle of the molluscs is proportional to the
necessity entailed by their locomotion and means of support.

Thus in the cephalic molluscs, where there is more locomotion
than in those which have no head, the mantle is closer, thicker and
stronger ; and among the cephalic molluscs, those which are naked
(without shells) have in addition a cuirass in their mantle which is
stronger than the mantle itself and greatly facilitates the locomotion
and contraction of the animal (slugs).

But if, instead of following the animal chain in the opposite direc-
tion from the actual order of nature, we followed it from the most
imperfect animals to the most perfect, we should then easily per-
ceive that nature when she was about to start the plan of organisation
of the vertebrates, was forced in the molluscs to abandon the use of a
crustaceous or horny skin as a support for muscular action, and to
prepare to transfer these fulcra into the interior of the animal. In
this way the molluscs are to some extent in the midst of this change
of system of organisation ; they have in consequence only feeble
powers of locomotive movements and they all carry out such move-
ments with remarkable slowness.

CIRRHIPEDES.

Animals without eyes which breathe by gills and have a mantle and jointed
arms with a horny skin.

The cirrhipedes, of which only four genera ^ are yet known, should
be considered as a special class, since these animals cannot belong to
any other class of invertebrate animals.

They approach the molluscs by their mantle and should be placed
immediately after the acephalic molluscs, since like them they have
neither head nor eyes.

Yet the cirrhipedes cannot be a part of the class of molluscs ; for
^ A natif a, Balanus, Coronula, and Tubicinflla

DEGRADATION OF ORGANISATION 87

their nervous system is characterised like the animals of the three
following classes by a ganglionic longitudinal cord. They have more-
over jointed arms with a horny skin and several pairs of transverse
jaws. They are therefore of lower rank than molluscs. Their fluids
move by a true circulation with arteries and veins.

These animals are fixed on marine bodies and in consequence carry
out no locomotion ; their principal movements are those of their arms.
Now although they have a mantle like the molluscs, nature could not
obtain from it any assistance for the movements of their arms, and
was forced to create in the skin of those arms fulcra for their muscles.
Hence the skin is coriaceous and almost horny like that of crustaceans
and insects.

ANNELIDS.

Animals ivith elongated annulated bodies ivithout jointed legs, breathing
by gills and having a. circulatory system and a ganglionic longi-
tudinal cord.

The class of annelids necessarily comes after that of cirrhipedes,
because no annelid has a mantle. We are moreover compelled to place
them before the crustaceans, because they have no jointed legs and it
would not do to interpose them in the series of those which have ; nor
does their organisation permit us to place them lower than the insects.

Although these animals in general are still very Uttle known, the
rank to which their organisation entitles them proves that in their case
again the degradation of organisation is continued ; for from this
aspect they are inferior to the molluscs in that they have a gangUonic
longitudinal cord ; they are inferior also to the cirrhipedes, which
have a mantle Uke molluscs ; and the fact that they have not jointed
legs prevents us from interposing them in the series of those which
are so organised.

Annehds owe their elongated form to their habits of life, for they
either live buried in damp earth or in mud or actually in the water,
mostly in tubes of various materials which they enter and leave at
will. Thus they are so like worms that all naturaUsts hitherto have
confused the two.

Their internal organisation shows a very small brain, a ganghonic
longitudinal cord, arteries and veins in which circulates blood that is
usually coloured red ; they breathe by gills, sometimes external and
protruding, and sometimes internal and hidden or invisible.

88 ZOOLOGICAL PHILOSOPHY

CRUSTACEANS.

Animals with a jointed body and limbs, crustaceous shin, a circulatory
system, and breathing by gills.

We now enter upon the long series of animals, whose body and
limbs are jointed, and whose integuments are hard, crustaceous,
horny or coriaceous.

The solid or hard parts of these animals are all on the exterior.
Since nature created the muscular system very httle in advance
of the earlier animals of this series, and since she had need of solid
support to endow it with energy, she was obhged to establish the
method of articulation in order to secure the possibihty of movement.

All the animals that exhibit this method of articulation were held
by Linnaeus and subsequently as forming only a single class, to which
was given the name of insects ; but it was at length recognised that
this large series of animals has several important divisions which
must be distinguished.

The class of crustaceans, which had thus been confused with that
of insects, although all the ancient naturahsts had always kept it
apart, is a division indicated by nature and must be maintained.
It should follow immediately upon the annelids and occupy the
eighth rank in the general series of animals ; this is required by their
organisation and is not a matter of arbitrary opinion.

The crustaceans indeed have a heart, arteries and veins ; a trans-
parent and almost colourless circulating fluid, and they all breathe
by true gills. This is unquestionable and will always constitute a
difficulty in the way of those who persist in placing them among the
insects on account of their having jointed legs.

If the crustaceans are completely distinguished from the arachnids
and insects by their circulation and respiratory organ, and if their
rank is therefore obviously superior, they yet share one trait of
inferiority of organisation with the arachnids and insects as compared
with the annelids ; that, namely, of being a part of the series of animals
with jointed limbs : a series in the course of which the circulatory
system and consequently the heart, arteries and veins are seen to
diminish and disappear, and in which again the branchial system
of respiration is likewise lost. The crustaceans therefore again confirm
the continuous degradation of organisation in the direction in which
we are following the animal scale. The transparency and extreme
thinness of the fluid which circulates in their vessels, hke that of
insects, is a further proof of their degradation.

As to their nervous system, it consists of a very small brain and a

DEGRADATION OF ORGANISATION 89

ganglionic longitudinal cord. This is a sign of poverty of that system
observed among the animals of the two preceding and the two following
classes ; for the animals of these classes are the last in which a nervous
system is still to be seen.

It is in the crustaceans that the last traces of an organ of hearing have
been identified ; after them it is no more found in any animal.

Observations.

Here ends the existence of a true circulatory system, that is to say,
of a system of arteries and veins, which is part of the organisation of the
most perfect animals and with which those of all the preceding classes
are provided. The organisation of the animals of which we shall now
speak is still more imperfect than that of the crustaceans, which are
the last in which a circulation is actually to be found. The degradation
of organisation is thus clearly in progress ; since according as we
advance along the series of animals, all features .of resemblance are
successively lost between the organisation of those we come to and
that of the most perfect animals.

Whatever may be the nature of the movement of the fluids in
the animals of the classes that we are about to traverse, that move
ment is secured by less active methods, and consta!itly tends to
become slower.

ARACHNIDS.

Animals breathing by limited tracheae, undergoing no metamorphosis,
and having throughout their lives jointed legs and eyes in their
head.

On continuing the order that we have hitherto followed, the ninth
rank in the animal kingdom necessarily belongs to the arachnids ;
they have so much affinity with the crustaceans that we shall always
have to bring them together, immediately following one another.
They are however entirely distinct ; for the arachnids furnish us
with the first example of a respiratory organ lower than gills, — one
never met with in animals which have a heart, arteries and veins.

Arachnids in fact breathe only by stigmata and air-carrying tracheae,
which are respiratory organs analogous to those of insects. But
these tracheae, instead of extending throughout the body as in the
insects, are limited to a small number of sacs : this shows that nature
is bringing to an end in the arachnids the method of respiration
which she had to employ before the establishment of gills, just as she
brought to an end in the fishes or later reptiles that which she had to
make use of, before she could form a true lung.

so ZOOLOGICAL PHILOSOPHY

If the arachnids are quite distinct from the crustaceans, through
not breathing by gills but by very limited air-carrying tracheae,
they are also to be distinguished from the insects. It would be quite
as improper to combine them with the insects of which they lack
the classic character and from which they differ even in internal
organisation, as it would be to confuse the crustaceans with the insects.

The arachnids, indeed, although having strong affinities with the
insects are essentally distinct from them :

1. In that they never undergo metamorphosis, that they have at
birth the shape and all the parts of an adult and that, consequently,
they have eyes in their head and jointed legs throughout their lives.
This is an order of things that follows from the nature of their internal
organisation and therein differs greatly from that of insects ;

2. In that in the arachnids of the first order (pedipalp-arachnids)
we begin to see the outlines of a circulatory system ; ^

3. In that their respiratory system, although of the same order
a.s that of insects, is nevertheless very different ; since their tracheae
are limited to a small number of sacs, and do not constitute the very
numerous air-canals extending throughout the animal's body that are
witnessed in the tracheae of insects ;

4. Lastly, in that the arachnids procreate several times in the course
of their life ; a faculty which the insects do not possess.

These considerations suffice to show how faulty are those arrange-
ments in which the arachnids and insects are combined into one class,
through paying exclusive regard to the joints in these animals' legs,
and the more or less crustaceous skin which covers them. It is almost
as if we were to consider only the more or less scaly integuments of
reptiles and fishes, and thus to combine them into one class.

The general degradation of organisation that we are seeking through-
out the entire animal scale is extremely obvious in the arachnids : these
animals indeed breathe by an organ inferior in organic perfection
to lungs and even to gills, and have only the rudiments of a circulation
apparently not yet finished off. They thus confirm in their turn the
continuous degradation in question.

This degradation may even be observed in the series of species
belonging to that class ; for the arachnids with antennae, making up
the second order, are sharply distinguished from the others, are very
inferior to them in progress of organisation, and come close to the
insects ; they differ from the latter however in undergoing no meta-

' "It is especially in the spiders that this heart may be easily observed : it may
be seen beating through the skin of the abdomen in species that are not hairy. On
removing this skin, a hollow oblong organ is seen, pointed at the two ends, with the
anterior end directed towards the thorax and from the sides of which there issue
visibly two or three pairs of vessels " (Cuvier, Anatom. conip. vol. iv. p. 419).

DEGRADATION OF ORGANISATION 91

morphosis ; and as they never launch themselves into the air, it is
very probable that their tracheae do not generally extend through-
out all parts of their bodies.

INSECTS.

Animals which undergo metamorphoses, and have in the perfecf state
two eyes and two antennae in their head, six jointed legs and wo
tracheae which extend throughout their body.

As we continue to follow the inverse order from that of nature,
the insects necessarily succeed the arachnids. They constitute that
immense series of imperfect animals which have no arteries or veins ;
which breathe by air-carrying tracheae not limited to special parts ;
lastly, which are born in a state less perfect than that in which they
reproduce ; and which consequently undergo metamorphoses.

In their perfect state all insects without exception have six jointed
legs, two antennae and two eyes in their head, and most of them
also have wings.

The insects necessarily occupy the tenth rank of the animal kingdom
in the order that we are following ; for they are inferior to the arachnids
in perfection of organisation since they are not born like these latter in
their perfect state, and they only procreate once in the course of their
hfe. It is particularly in the insects that we begin to observe that the
organs essential to maintenance of life are almost equally distributed,
and in most cases situated throughout their bodies instead of being
isolated in special places, as is the case in the most perfect animals.
The exceptions to this rule gradually disappear, so that it becomes
ever more striking in the lower classes of animals.

Nowhere hitherto has the general degradation of organisation
been more manifest than in the insects, whose organisation is less
perfect than that of the animals of any of the preceding classes.
This degradation comes out even within the various orders into which
insects are naturally divided ; for those of the three first orders
(Coleoptera, Orthoptera, Neuroptera) have mandibles and maxillae
in their mouths ; those of the fourth order (Hymenoptera) begin to
possess a sort of proboscis ; finally, those of the four last orders (Lepi-
doptera, Hemiptera, Diptera and Aptera) have really nothing more
than a proboscis. Now paired maxillae are nowhere found again
in the animal kingdom, after the insects of the three first orders.
With regard to wings, the insects of the six first orders have four,
all of which or only two serve for flight. Those of the seventh and
eighth have only two wings or else they are quite aborted. The

92 ZOOLOGICAL PHILOSOPHY

larvae of the insects of the two last orders have no legs and are like
worms.

It appears that the insects are the last animals which have a quite
distinct sexual reproduction and are probably oviparous.

Lastly, we shall see that insects are rendered highly remarkable
by what is called their skill ; but this alleged skill is far from being
the product of any thought or any combination of ideas on their
part.

Observation.

Just as among the vertebrates the fishes display in their general
conformation and anomalies of organisation the product of the action
of their environment ; so the insects among the invertebrates exhibit,
in their shape, organisation and metamorphoses, the obvious effects
of the action of the air in which they live ; for most of them launch
themselves into it and habitually maintain themselves there like
birds.

If the insects had had lungs, if they had been able to swell them-
selves out with air, and if the air which penetrates into every part
of their body could have there become rarefied like that which is intro-
duced into the body of birds, their hair would no doubt have changed
into feathers.

Lastly, if among invertebrate animals we are surprised to find so
few affinities between the insects which undergo remarkable meta-
morphoses and other classes of invertebrates, let us remember that
these are the only invertebrate animals which launch themselves into
the air and there execute movements of progression ; we shall then
no longer be surprised that such pecuUar conditions and habits must
have produced peculiar results.

The insects are allied only to the arachnids by their affinities, and in
fact these two are in general the only invertebrate animals that live in
the air ; but no arachnid has the faculty of flight ; none therefore
undergoes metamorphosis ; and when I come to treat of the influence
of habits, I shall show that these animals, being accustomed to remain
on the surface of the earth and to hve in retreats, must have lost a
part of the faculties of insects- and acquired characters which con-
spicuously distinguish the two groups.

Extinction of Several Organs essential to the
Most Perfect Animals.

After the insects it appears that there is a rather large gap in the
series remaining to be filled by animals not yet observed ; for in this
part of the series several organs essential to the most perfect animals

DEGRADATION OF ORGANISATION 93

suddenly drop out and are really annihilated, since they are not found
again in the classes which remain to be considered.

Disappearance of the Nervous System.

Here for instance the nervous system (the nerves and their centre
of communication) completely disappears, and is no more found in
any of the animals of the succeeding classes.

In the most perfect animals, this system consists of a brain which
appears to serve for carrying out acts of intelligence. At its base is
the nucleus of sensations from which issue nerves and also a dorsal
spinal cord which sends out other nerves to various parts.

Among the vertebrates the brain becomes regularly reduced, and
as its volume diminishes the spinal cord becomes larger and seems to
take its place.

Among the molluscs which constitute the first class of the inver-
tebrates the brain still exists, but there is no spinal cord nor a gan-
glionic longitudinal cord, and as ganglia are rare the nerves do not
appear to have nodes.

Lastly, in the five following classes the nervous system is approach-
ing its end and is reduced to the very small rudiments of a brain and
to a longitudinal cord from which issue nerves. Thereafter there is
no longer a separate nucleus for sensations, but a multitude of small
nuclei scattered throughout the length of the animal's body.

Hence among insects, the important system of feeUng comes to an
end ; a system which at a certain stage of development gives birth
to ideas and which in its highest perfection can produce all the acts
of intelligence ; which, lastly, is the source whence muscular action
derives its power and without which sexual reproduction apparently
could not exist.

The centre of communication of the nervous system is situated
in the brain or at its base or in a ganglionic longitudinal cord. There
is still a longitudinal cord when there is no longer any obvious brain ;
but when there is neither a brain nor a longitudinal cord, the nervous
system ceases to exist.

Disappearance of the Sexual Organs.

Here again all traces of sexual reproduction disappear ; indeed
among the animals about to be cited it is no longer possible to recognise
organs for true impregnation. We shall, however, still find among
the animals of the two following classes kinds of ovaries, abounding
in oviform corpuscles that are alleged to be eggs ; but I look upon
these supposed eggs which can develop without previous fertiUsation

94 ZOOLOGICAL PHILOSOPHY

as buds or internal gemmules ; they establish a connection between
internal gemmiparous reproduction and sexual oviparous reproduction.

The strength of habit is so great that man always perseveres in the
same view of things, even when it is contrary to the evidence.

Thus botanists, accustomed to observing the sexual organs of a
great number of plants, affirm that all without exception have such
organs. Consequently several botanists have made every conceivable
effort to discover stamens and pistils in cryptogamic or agamic plants ;
and they have preferred to attribute arbitrarily and without proof
these functions to parts of whose use they are ignorant, rather than
admit that nature may attain the same end by different means.

It was believed that every reproductive body is a seed or egg, that is
to say, a body which must undergo the influence of sexual fertilisa-
tion in order to be reproductive. This is what caused Linnaeus to
say : Omne vivutn ex ovo. But we now know well plants and animals
which reproduce entirely by means of bodies that are neither seeds
nor eggs, and which consequently do not require sexual fertilisation.
These bodies are therefore differently fashioned and develop in another
manner.

The following is the principle to be observed in judging of the method
of reproduction in any hving body.

Any reproductive corpuscle which without having any investment
to break through lengthens, grows and becomes a plant or animal
similar to that from which it sprang, is not a seed nor an egg ; it
undergoes no germination and does not hatch after beginning to
grow, and its formation requires no sexual fertilisation : thus it does
not contain an embryo in an investment which has to be broken
through, as does the seed or egg.

Now, if you follow attentively the development of the reproductive
corpuscles of algae, fungi, etc., you will see that the result of the lengthen-
ing and growth of these corpuscles is to take imperceptibly the shape
of the plant from which they spring ; that they do not break through
any investment as does the embryo in the seed or egg.

Similarly, if you follow the gemma or bud of a polyp Uke a hydra,
you will be convinced that this reproductive body does nothing but
lengthen out and grow ; that it breaks through no investment ; in short,
that it does not hatch hke a chicken or silkworm coming out of its egg.

It is then clear that all reproduction of individuals does not come
about by means of sexual fertilisation ; and that when sexual fertilisa-
tion does not occur there is not really a true sexual organ. Now as no
organ for fertilisation is to be distinguished in the four classes follow-
ing the insects it appears that this is the point in the animal chain
at which sexual reproduction ceases to exist.

DEGRADATION OF ORGANISATION 95

Disappearance of the Organ of Sight.

Here again the organ of sight, so useful to the most perfect animals,
is entirely extinguished. This organ began to be deficient in some
of the molluscs and cirrhipedes and in most of the annelids, and is
only found afterwards in the crustaceans, arachnids and insects in a
very imperfect state and of little or no use ; after the insects it does
not re-appear in any animal.

Here again, finally, the head altogether ceases to exist, — an essential
part of the body of the most perfect animals and the seat of the brain
and nearly all the senses ; for the swelling at the anterior extremity
of the body of some worms like Taenia is caused by the arrangement
of their suckers and is not the seat of a brain nor of any organ of
hearing, sight, etc., since there are no such organs in the animals of
the neighbouring classes. Hence this swelling cannot be considered
as a true head.

We see that at this part of the animal scale the degradation of
organisation becomes extremely rapid, and strongly foreshadows the
greatest simplification of animal organisation.

WORMS.

Animals with soft elongated bodies, without head, eyes or jointed legs,
and no longitudinal cord or circulatory system.

We now come to worms, which have no vessels for circulation ; in-
cluding those known under the name of intestinal worms, and some
others not intestinal whose organisation is quite as imperfect. They
are animals with soft more or less elongated bodies, which undergo no
metamorphosis and are all destitute of a head, eyes and jointed legs.

The worms should be placed immediately after the insects and before
the radiarians, and occupy the eleventh rank in the animal kingdom.
It is among them that we note the origin of the tendency of nature
to establish the system of articulations, a system that she subsequently
carried to completion in the insects, arachnids and crustaceans. But
the organisation of the worms is less perfect than that of the insects,
since they have no longitudinal cord, head, eyes or true legs, so that we
are forced to place them after the insects ; lastly, the new kind of shape,
which nature initiates in them on passing from a radiating arrange-
ment of the parts to the system of articulations, shows that the worms
should be placed even before the radiarians. After the insects, more-
over, the plan followed by nature in the animals of preceding classes
is lost sight of, viz. that general shape of the animal which consists

96 ZOOLOGICAL PHILOSOPHY

of a bilateral symmetry of the parts, so that each part is opposite to
another exactly like it.

In the worms we no longer find this bilateral symmetry, nor do
we yet witness the radiating arrangement of the organs both internal
and external which characterises the radiarians.

After I established the annelids, some naturalists called them by
the name of worms ; and as they did not then know what to do with
the animals now under discussion, they united them with the polyps.
I leave the reader to imagine what may be the aflBnities and classic
characters that justify the union in one class of Taenia or Ascaris with
a hydra or any other polyp.

Several worms still appear to breathe hke insects by tracheae of
which the external openings are kinds of stigmata ; but there is reason
to believe that these limited or imperfect tracheae are water-carrying
and not air-carrying like those of insects ; because these animals
never live in the open air, but are continuously in the water or bathed
by fluids which contain water.

As no organ for fertilisation is distinguished in them, I suppose
that sexual reproduction does not occur in these animals. It may be
however that, just as there exists a primitive circulation in arachnids
so there may exist a sexual reproduction in the worms, as is suggested
by the various shapes of the tail of Strongylus ; but observation has
not yet fully established such reproduction in these animals.

Objects which are found in some of them and supposed to be ovaries
(as in Taenia) appear to be merely clusters of reproductive corpuscles
which do not require fertilisation. These oviform corpuscles are
internal, like those of sea-urchins, and not external like those of
Coryne, etc. Polyps exhibit similar differences in the situation of their
gemmules ; it is therefore probable that the worms are internally
gemmiparous.

Animals like the worms, which have no head, eyes, legs or perhaps
sexual reproduction, provide further evidence in their turn of the con-
tinuous degradation of organisation that we are seeking throughout
the animal scale.

RADIARIANS.

Animals with regenerating bodies, destitute of a head, eyes or jointed
legs ; with the mouth on the inferior surface and a radiating arrange-
ment of the parts both internal and external.

In the usual order the radiarians occupy the twelfth rank in the
lengthy series of known animals, and constitute one of the three last
classes of invertebrates.

DEGRADATION OF ORGANISATION «7

When we reach this class we find animals with a general shape
and arrangement of the parts and organs, both internal and external,
that nature has not employed in any of the animals of the anterior
classes.

The radiarians indeed conspicuously exhibit in their internal and
external parts that radiating arrangement around a centre or axis,
which constitutes a special shape not hitherto used by nature. Its
rudiments are found in the polyps, which accordingly come next.

Nevertheless, the radiarians form a stage in the animal scale quite
distinct from the polyps ; so that we can no more confuse radiarians
with polyps than we can class crustaceans with insects or reptiles
with fishes. Among the radiarians indeed, not only do we find again
organs apparently intended for respiriation (tubes or kinds of water-
bearing tracheae), but we discover in addition special organs for
reproduction, such as kinds of ovaries of various shapes to which
there is nothing analogous in the polyps. Moreover, the intestinal
canal of the radiarians is not generally a cul-de-sac with a single
opening as in all the polyps ; their mouth is always on the inferior
surface and displays a special arrangement which is quite different
from that commonly found in polyps.

Although the radiarians are very remarkable animals, and as yet
little known, what we do know of their organisation plainly points to
the rank which I am assigning to them. Like the worms, radiarians
have no head, eyes, jointed legs, circulatory system or perhaps nerves.
Yet the radiarians necessarily come next to the worms, for the latter
have nothing in the arrangement of their internal organs that suggests
a radiating shape, and it is among them that the system of articulations
begins.

If the radiarians are destitute of nerves, they cannot have the faculty
of feeling, but are simply irritable ; this fact seems to be confirmed
by observations made on living star-fishes, whose arms have been cut
off without their showing any sign of pain.

In many radiarians fibres may still be distinguished ; but can we
call these fibres muscles ? Not unless we are justified in saying
that a muscle can function without nerves. Do not plants show us
that cellular tissue may be reduced to fibres ? Yet we cannot possibly
regard these fibres as muscular. In my opinion it does not follow
that because a living being has distinguishable fibres, it must therefore
have muscles ; I hold that where there are no nerves, there is no
muscular system. There is reason to believe that in animals without
nerves the fibres which are still to be found possess the faculty by mere
irritability of producing movements which replace those of the muscles,
although less energetically.

98 ZOOLOGICAL PHILOSOPHY

Not only does it appear that the muscular system has ceased to
exist in the radiarians, but also there seems to be no sexual repro-
duction. There is indeed nothing to show or even to suggest that the
little oviform bodies, the clusters of which are called ovaries in these
animals, undergo any fertilisation or are true eggs : this is rendered
still less probable by the fact that they are found in all individuals
alike. Hence I regard these little oviform bodies as already perfected
internal gemmules, and the clusters of them in special places as nature's
preliminary step towards sexual reproduction.

The radiarians in their turn contribute to prove the general degrada-
tion of animal organisation ; for on reaching this class of animals
we find a shape and a new arrangement of the parts and organs that
are far removed from the animals of the preceding classes. Furtlier-
more they appear to be destitute of feeling, muscular movement and
sexual reproduction ; among them the intestinal canal no longer has
two exits, the clusters of oviform corpuscles disappear, and the body
becomes completely gelatinous.

Observation.

It appears that in very imperfect animals such as the polyps and
radiarians, the centre of movement of the fluids does not exist except
in the alimentary canal ; it is here that it is first established, and it is
through this canal that the subtle surrounding fluids enter, mainly
for the purpose of stimulating the movement of the fluids which belong
to these animals themselves. What would plant life be without
external stimuli ? What indeed would be the life of the most imperfect
animals without this factor, that is, without the caloric and electricity
of the environment ?

The radiating form has no doubt been acquired as a consequence
of this method, which nature employs feebly at first in the polyps
and afterwards with greater vigour in the radiarians ; for the subtle
surrounding fluids which enter the alimentary canal are expansive
and must by incessant repulsion from the centre towards every point
of the circumference give rise to this radiating arrangement of the
parts.

This is the reason why in the radiarians the intestinal canal, although
still very imperfect, since it has usually only one opening, is none the
less provided with numerous radiating vasculiform and often branched
appendages.

This again is no doubt the reason why in the soft radiarians, such as
jelly-fishes, etc., we may observe a continual isochronous movement,
a movement which very probably results from the alternative move-
ments of the masses of subtle fluids, which penetrate into the interior

DEGRADATION OF ORGANISATION 99

of these animals and escape again, after having spread throughout
all their parts.

Let it not be said that the isochronous movements of the soft radi-
arians are signs of respiration ; for nature does not exhibit in any
animal after the vertebrates those alternate and measured movements
of inspiration and expiration ; whatever the respiration of radiarians
may be, it is extremely slow and involves no appreciable movement.

POLYPS.

Animals with sub-gelatinous and regenerating bodies, with no special
organ but an alimentary canal with only one opening. Terminal
mouth supplied with radiating tentacles or a ciliated and rotatory
organ.

With the polyps we reach the penultimate stage of the animal scale,
that is to say, the last but one of the classes which have to be established
among animals.

Here the imperfection and simplicity of organisation are very
striking, so that the animals of this group have scarcely any faculties
left, and their animal nature has long been doubted.

They are gemmiparous animals with homogeneous bodies, usually
gelatinous, and with very regenerative parts, not displaying the
radiating shape (for it is only here that nature began it) except in
radiating tentacles around their mouth, and having no special organ
but an intestinal canal, which has only one opening and is therefore
incomplete.

The polyps may be described as much more imperfect animals
than any of those which make up the preceding classes, for they have
no brain, longitudinal cord, nerves, special respiratory organs, vessels
for the circulation of fluids nor ovary for reproduction. The substance
oF their body is to a great extent homogeneous and composed of
a gelatinous and irritable cellular tissue in which fluids move slowly.
Lastly, their viscera are entirely reduced to an imperfect alimentary
canal, rarely folded on itself or provided with appendages, and usually
resembling a mere elongated sac, always with a single opening which
serves at once for mouth and anus.

There can be no justification for the statement that, although
we find in these animals no nervous system, respiratory organ
or muscle, etc., yet these organs still exist infinitely reduced and
distributed or dissolved throughout the general substance of the
body, and equally divided up in every molecule instead of being
collected in special places ; consequently that every point in their

100 ZOOLOGICAL PHILOSOPHY

body can experience every kind of sensation, muscular movement,
will, ideas and thought ; this would be an altogether gratuitous,
baseless and improbable supposition. On such a supposition a hydra
must have in every part of its body all the organs of the most perfect
animals, and hence every point in the body of this polyp must see,
hear, distinguish odours, tastes, etc. ; and also must have ideas,
form judgments, think and, in short, reason ; each molecule of the body
of a hydra or any other polyp would in itself be a perfect animal ; and
the whole hydra would be a more perfect animal even than man.
since each of its molecules would be equivalent, as regards the com-
pletion of organisation and faculties, to an entire individual of the
human species.

There is no reason why such an argument should not be extended to
the Monas — the most imperfect of known animals — and even to plants
themselves, which also possess life. We should then attribute to each
molecule of a plant all the aforementioned faculties, though restricted
within limits set by the nature of the living body of which it is part.

Assuredly it is not to this that the study of nature leads us. This
study teaches us, on the contrary, that wherever an organ ceases to
exist, the function depending on it ceases likewise. Any animal which
has no eyes or whose eyes have been destroyed cannot see ; and
although in the last analysis the various senses derive their origin
from touch, of which they are only special modifications, yet no animal
which is without nerves, the special organ of feeling, could experience
any kind of sensation ; for it has not the intimate feeling of its existence,
it has not the central nucleus to which sensation has to be conveyed,
and consequently it could not feel.

Thus the sense of touch, which is the basis of the other senses and is
spread throughout every part of the bodies of animals which have
nerves, no longer exists in those which, like the polyps, have no nerves.
Among the latter, the parts are nothing more than merely irritable ;
they are so in a very high degree, but they are devoid of feeling and
hence of every kind of sensation. In order that a sensation may
arise, an organ is first necessary to receive it (nerves) ; and then some
central nucleus must exist (a brain or ganglionic longitudinal cord)
to which this sensation may be conveyed.

A sensation is always the sequel of an impression received and
immediately conveyed to an internal nucleus, where the sensation
is formed. Interrupt the communication between the organ which
receives the impression and the nucleus where the sensation is formed,
and all feeling will immediately cease. This principle can never be
disputed.

No polyp can really be oviparous ; for it has no special organ for

DEGRADATION OF ORGANISATION 101

reproduction. Now in order to produce true eggs, it is necessary not
only that the animal should have an ovary, but in addition that it or
some other individual of its species should have a special organ for
fertilisation, and it cannot be shown that the polyps have such organs ;
in place of them we are well aware of the buds which some of them
produce for purposes of multiplication ; and on paying them a little
attention we note that these buds are themselves nothing more than
somewhat isolated portions of the animal's body, — portions less
simple than those employed by nature for the multipUcation of the
animalcules which compose the last class of the animal kingdom.

Polyps, being highly irritable, only move by external stimuli foreign
to themselves. All their movements are necessary results of impressions
received, and are in general carried out without any act of will ; they
are thus without any possibility of choice, since they cannot have
any will.

They invariably and inevitably move towards the light, just like
the branches and leaves or flowers of plants, although in their case the
movement is slower. No polyp pursues its prey, nor seeks for it with
its tentacles ; but when some foreign body touches these same ten-
tacles, they hold it and carry it to the mouth, and the polyp swallows
it without making any distinction as to its suitabihty or the reverse.
It digests and feeds on the body if it is capable of being digested,
but rejects it entirely if it remains some time untouched in the
alimentary canal ; finally, it brings up such of the débris as can be no
more broken up ; but in all this, there is the same necessity in the
action and never any possibility of choice to vary it.

The distinction of the polyps from the radiarians is very wide and
glaring ; nowhere in the interior of the polyps is the radiating arrange-
ment to be found : their tentacles alone have this arrangement, thus
resembling the arms of the cephalapod molluscs, with which however
they certainly cannot be confused. Moreover the polyps have a
superior terminal mouth, while the mouth of the radiarians is other-
wise situated.

It is altogether improper to give the polyps the name of zoophytes,
which means animal-plants ; because they are entirely and completely
animals. They have faculties absent in plants, that, for instance, of
true irritablity and generally of digestion ; and, lastly, their nature
has nothing essentially in common with that of a plant.

The only affinities existing between polyps and plants are : (1) A
similar simplification of organisation ; (2) the faculty possessed by
many polyps of adhering to one another with a common conmunica-
tion by their aUmentary canal, and of forming compound animals ;
(3) the external shape of the groups formed by these combined polyps,

102 ZOOLOGICAL PHILOSOPHY

a shape which has long caused these groups to be taken for true plants,
since they are often branched almost in the same way.

Whether polyps have one or several mouths, there is always an
aUmentary canal to which they lead and consequently an organ for
digestion, of which all plants are destitute.

If the degradation of organisation that we have observed in all classes
starting from the mammals is anywhere obvious, it is assuredly among
the polyps, whose organisation is reduced to an extreme simphfication.

INFUSORIANS.

Infinitely small animals with gelatinous, transparent, homogeneous
and very contractile bodies ; with no distinct special organ internally,
but often oviform gemmules ; and having externally no radiating
tentacles nor rotatory organs.

At length we reach the last class of the animal kingdom, comprising
the most imperfect animals from all points of view ; that is, those
which have the simplest organisation, possess the fewest faculties and
seem all to be mere rudiments of animal nature.

Hitherto I have placed these small animals in the class of polyps,
of which they constituted the last order under the name of amorphous
polyps, since they have no constant shape pecuhar to them all ;
but I have recognised the necessity of separating them to form a class
apart, though this in no wise changes the rank that I had assigned
to them. The only result of this change is to establish a Une of demarca-
tion which appears to be called for, on account of the greater sim-
plicity of their organisation and their lack of radiating tentacles and
rotatory organs.

Since the organisation of the infusorians becomes ever more simple
as we pass down their genera, the last of these genera shows us in some
degree the limit of animahty, the hmit at all events of what we can
reach. It is especially in the animals of the second order of this class
that we can verify the entire disappearance of any trace of an intestinal
canal and mouth ; so that they have no special organ whatever nor
any digestion.

They are only very tiny gelatinous, transparent, contractile and
homogeneous bodies, consisting of cellular tissue, with very shght
cohesion and yet irritable throughout. These tiny bodies, which look
like animated or moving points, feed by absorption and continual
imbibition ; and they are doubtless animated by the influence of the
subtle surrounding fluids, such as caloric and electricity, which stimu-
late in them the movements constituting life.

DEGRADATION OF ORGANISATION 103

If we were to imagine that such animals possess all the organs
known in other animals, but that these organs are dissolved throughout
their bodies, how absurd such a supposition would be !

The extremely slight cohesion between the parts of these tiny
gelatinous bodies is an indication that such organs cannot exist, since
they could not possibly carry on their functions. It is clear that in
order that any organs may have the power of reacting on fluids and
of carrying on their appropriate functions, their parts must have
enough cohesion and firmness to give them strength ; now this is not
to be imagined in the case of these fragile animalcules. It is exclu-
sively among the animals of this class that nature appears to carry
out direct or spontaneous generations, which are incessantly renewed
whenever conditions are favourable ; and we shall endeavour to
show that it is through this means that she acquired the power after
an enormous lapse of time to produce indirectly all the other races of
animals that we know.

Justification for the belief that the infusorians or most of them owe
their existence exclusively to spontaneous generation is found in the
fact that all these fragile animals perish during the reduction of tem-
perature in bad seasons ; and it surely will not be suggested that such
delicate bodies could leave any bud sufficiently hardy to be preserved
and to reproduce them in warm weather.

Infusorians are found in stagnant waters and infusions of plant
or animal substances, and even in the seminal fluid of the most perfect
animals. They are found just the same in all parts of the world, but
only in conditions suitable for their existence.

Thus on examining in turn the various systems of organisation of
animals from the most complex to the simplest, we have seen the
degradation of animal organisation beginning even in the class that
comprises the most perfect animals and thence advancing progressively
from class to class, although with anomalies due to environment,
and finally ending with the infusorians. These last are the most
imperfect animals and the simplest in organisation, — the animals
in which the degradation that we have traced reaches its limit.
Animal organisation is then reduced to a simple homogeneous gela-
tinous body with very slight cohesion, destitute of special organs, and
entirely formed of a very delicate and primitive cellular tissue, which
appears to be vivified by subtle surrounding fluids incessantly penetrat-
ing it and exhahng from it.

We have seen each special organ in turn, including even the most
essential, become slowly degraded till it is less special, less isolated,
and finally completely lost and gone, long before reaching the other
extremity of the order we are tracing ; and we have noticed that it is

104 ZOOLOGICAL PHILOSOPHY

chdefly among the invertebrate animals that the extinction of special
organs occurs.

It is true that even before leaving the division of vertebrates, we
already witness great changes in the perfection of organs ; while some
even disappear altogether, such as the urinary bladder, the diaphragm,
the organ of voice, the ey ;lids, etc. The lung, for instance, which is
the most perfect respiratory organ, begins its degradation in the reptiles
and ceases to exist in the fishes, not to reappear again in any inver-
tebrate animal. Finally, the skeleton, the appendages of which
constitute the basis of the four extremities or limbs possessed by most
vertebrates, begins its deterioration mainly in the reptiles and comes
entirely to an end with the fishes.

But it is in the division of invertebrates that the extinction takes
place of the heart, brain, gills, conglomerate glands, vessels for circula-
tion, the organs of hearing and sight, that of sexual reproduction
and even that of feeling, as also of movement.

As I have already said, we should vainly seek in a polyp, such as the
hydra or most animals of that class, the slightest vestiges either of nerves
(organs of feeling) or of muscles (organs of movement) ! Irritability,
with which every polyp is highly endowed, alone replaces the faculty of
feehng which no polyp possesses, since it has not the essential organ for it.

It also replaces the faculty of voluntary movement, since all will
is an act of the organ of intelligence, and this animal is absolutely
destitute of any such organ. All its movements are necessary results
of the impressions on its irritable parts of external stimuli ; and they
are carried out without any scope for choice.

Put a hydra in a glass of water, and set this glass in a room where
daylight only enters by one window and therefore only from one side.
When this hydra has fixed on some point of the sides of the glass,
turn the glass so that the light strikes it on the opposite side to that
where the animal is. You will then always see the hydra go with
a slow movement and place itself where the light strikes, and stay there
so long as you do not change this point. This is the same in those parts
of plants which, without any act of will, lean towards the side from
which the light comes.

Doubtless wherever a special organ no longer exists, the function
which it supports also ceases to exist ; and we may furthermore
clearly observe that according as an organ is degraded and reduced,
the function resulting from it becomes proportionally more vague
and imperfect. Thus, we find that on descending from the most
complex towards the simplest, the insects are the last animals which
have eyes ; but there is sound reason for the belief that they see very
dimly and make little use of them.

DEGRADATION OF ORGANISATION 105

Thus on traversing the chain of animals from the most perfect to
the most imperfect, and on examining in turn the various systems
of organisation distinguished in the course of this chain, the degrada-
tion of organisation and of each organ up to their complete disappear-
ance is seen to be a positive fact which we have now verified.

This degradation comes out even in the nature and consistency of
the essential fluids and flesh of animals. For the flesh and blood of
mammals and birds are the most complex and animalised materials
that can be obtained from the soft parts of animals. Hence after
the fishes these materials are progressively degraded until in the soft
radiarians, the polyps and the infusorians, the essential fluid has only
the consistency and colour of water and the flesh is nothing more than
a gelatinous scarcely animalised material. The bouillon made from
such flesh would scarcely be found very nourishing or strengthening
by any one who tried to Hve upon it.

Whether or no we recognise these interesting truths, they will never-
theless always be forced upon the attention of those who closely
observe facts, and who, overcoming prevailing prejudices, consult the
phenomena of nature and study her laws and regular procedure.

We shall now pass to the examination of another kind of subject,
and shall endeavour to prove that the environment exercises a great
influence over the activities of animals, and that as a result of this
influence the increased and sustained use or disuse of any organ are
causes of modification of the organisation and shape of animals and
give rise to the anomalies observed in the progress of the complexity
of animal organisation.

CHAPTER VIL

OF THE INFLUENCE OF THE ENVIRONMENT ON THE ACTIVITIES
AND HABITS OF ANIMALS, AND THE INFLUENCE OF THE
ACTIVITIES AND HABITS OF THESE LIVING BODIES IN MODI-
FYING THEIR ORGANISATION AND STRUCTURE.

We are not here concerned with an argument, but with the examina-
tion of a positive fact — a fact which is of more general application than
is supposed, and which has not received the attention that it deserves,
no doubt because it is usually very difficult to recognise. This fact
consists in the influence that is exerted by the environment on the
various living bodies exposed to it.

It is indeed long since the influence of the various states of our
organisation on our character, inclinations, activities and even ideas
has been recognised ; but I do not think that anyone has yet drawn
attention to the influence of our activities and habits even on our
organisation. Now since these activities and habits depend entirely
on the environment in which we are habitually placed, I shall endeavour
to show how great is the influence exerted by that environment on the
general shape, state of the parts and even organisation of living bodies.
It is, then, with this very positive fact that we have to do in the
present chapter.

If we had not had many opportunities of clearly recognising the
result of this influence on certain living bodies that we have trans-
ported into an environment altogether new and very different from
that in which they were previously placed, and if we had not seen
the resulting effects and alterations take place almost under our very
eyes, the important fact in question would have remained for ever
unknown to us.

The influence of the environment as a matter of fact is in all
times and places operative on living bodies ; but what makes this
influence difficult to perceive is that its effects only become percep-
tible or recognisable (especially in animals) after a long period of time.

INFLUENCE OF ENVIRONMENT 107

Before setting forth to examine the proofs of this fact, which deserves
our attention and is so important for zoological philosophy, let us
sum up the thread of the discussions that we have already begun.

In the preceding chapter we saw that it is now an unquestionable
fact that on passing along the animal scale in the opposite direction
from that of nature, we discover the existence, in the groups composing
this scale, of a continuous but irregular degradation in the organisa-
tion of animals, an increasing simplification in their organisation,
and, lastly, a corresponding diminution in the number of their
faculties.

This well-ascertained fact may throw the strongest light over the
actual order followed by nature in the production of all the animals
that she has brought into existence, but it does not show us why the
increasing complexity of the organisation of animals from the most
imperfect to the most perfect exhibits only an irregular gradation, in
the course of which there occur numerous anomalies or deviations
with a variety in which no order is apparent.

Now on seeking the reason of this strange irregularity in the increas-
ing complexity of animal organisation, if we consider the influence
that is exerted by the infinitely varied environments of all parts of the
world on the general shape, structure and even organisation of these
animals, all will then be clearly explained.

It will in fact become clear that the state in which we find any animal,
is, on the one hand, the result of the increasing complexity of organisa-
tion tending to form a regular gradation ; and, on the other hand,
of the influence of a multitude of very various conditions ever tending
to destroy the regularity in the gradation of the increasing complexity
of organisation.

I must now explain what I mean by this statement : the environment
affects the shape and organisation of animals, that is to say that when the
environment becomes very different, it produces in course of time
corresponding modifications in the shape and organisation of animals.

It is true if this statement were to be taken literally, I should be
convicted of an error ; for, whatever the environment may do, it
does not work any direct modification whatever in the shape and
organisation of animals.

But great alterations in the environment of animals lead to great
alterations in their needs, and these alterations in their needs neces-
sarily lead to others in their activities. Now if the new needs become
permanent, the animals then adopt new habits which last as long
as the needs that evoked them. This is easy to demonstrate, and
indeed requires no amphfication.

It is then obvious that a great and permanent alteration in the

108 ZOOLOGICAL PHILOSOPHY

environment of any race of animals induces new habits in these
animals.

Now, if a new environment, which has become permanent for some
race of animals, induces new habits in these animals, that is to say,
leads them to new activities which become habitual, the result will
be the use of some one part in preference to some other part, and in
some cases the total disuse of some part no longer necessary.

Nothing of all this can be considered as hypothesis or private opinion ;
on the contrary, they are truths which, in order to be made clear, only
require attention and the observation of facts.

We shall shortly see by the citation of known facts in evidence,
in the first place, that new needs which estabUsh a necessity for some
part really bring about the existence of that part, as a result of efforts ;
and that subsequently its continued use gradually strengthens,
develops and finally greatly enlarges it ; in the second place, we shall
see that in some cases, when the new environment and the new needs
have altogether destroyed the utility of some part, the total disuse
of that part has resulted in its gradually ceasing to share in the
development of the other parts of the animal ; it shrinks and wastes
little by httle, and ultimately, when there has been total disuse for
a long period, the part in question ends by disappearing. All this is
positive ; I propose to furnish the most convincing proofs of it.

In plants, where there are no activities and consequently no habits,
properly so-called, great changes of environment none the less lead to
great differences in the development of their parts ; so that these
differences cause the origin and development of some, and the shrinkage
and disappearance of others. But all this is here brought about by
the changes sustained in the nutrition of the plant, in its absorption
and transpiration, in the quantity of caloric, light, air and moisture
that it habitually receives ; lastly, in the dominance that some of the
various vital movements acquire over others.

Among individuals of the same species, some of which are continually
well fed and in an environment favourable to their development,
while others are in an opposite environment, there arises a difference
in the state of the individuals which gradually becomes very remark-
able. How many examples I might cite both in animals and plants
which bear out the truth of this principle ! Now if the environment
remains constant, so that the condition of the ill-fed, suffering or
sickly individuals becomes permanent, their internal organisation is
ultimately modified, and these acquired modifications are preserved
by reproduction among the individuals in question, and finally give
rise to a race quite distinct from that in which the individuals have been
continuously in an environment favourable to their development.

INFLUENCE OF ENVIRONMENT 109

A very dry spring causes the grasses of a meadow to grow very
little, and remain lean and puny ; so that they flower and fruit after
accomplishing very little growth.

A spring intermingled with warm and rainy days causes a strong
growth in this same grass, and the crop is then excellent.

But if anything causes a continuance of the unfavourable environ-
ment, a corresponding variation takes place in the plants : first in
their general appearance and condition, and then in some of their
special characters.

Suppose, for instance, that a seed of one of the meadow grasses in
question is transported to an elevated place on a dry, barren and stony
plot much exposed to the winds, and is there left to germinate ; if
the plant can live in such a place, it will always be badly nourished,
and if the individuals reproduced from it continue to exist in this
bad environment, there will result a race fundamentally different from
that which lives in the meadows and from which it originated. The
individuals of this new race will have small and meagre parts ; some
of their organs will have developed more than others, and will then be
of unusual proportions.

Those who have observed much and studied large collections, have
acquired the conviction that according as changes occur in environ-
ment, situation, climate, food, habits of life, etc. , corresponding changes
in the animals likewise occur in size, shape, proportions of the parts,
colour, consistency, swiftness and skill.

What nature does in the course of long periods we do every day
when we suddenly change the environment in which some species of
living plant is situated.

Every botanist knows that plants which are transported from their
native places to gardens for purposes of cultivation, gradually undergo
■changes which ultimately make them unrecognisable. Many plants,
by nature hairy, become glabrous or nearly so ; a number of those
which used to lie and creep on the ground, become erect ; others
lose their thorns or excrescences ; others again whose stem was
perennial and woody in their native hot chmates, become herbaceous
in our own climates and some of them become annuals ; lastly, the
size of their parts itself undergoes very considerable changes. These
effects of alterations of environment are so widely recognised, that
botanists do not like to describe garden plants unless they have been
recently brought into cultivation.

Is it not the case that cultivated wheat (Triticum sativum) is a plant
which man has brought to the state in which we now see it ? I should
like to know in what country such a plant lives in nature, otherwise
than as the result of cultivation.

110 ZOOLOGICAL PHILOSOPHY

Where in nature do we find our cabbages, lettuces, etc., in the same
state as in our kitchen gardens ? and is not the case the same with
regard to many animals which have been altered or greatly modified
by domestication ?

How many different races of our domestic fowls and pigeons have
we obtained by rearing them in various environments and different
countries ; birds which we should now vainly seek in nature ?

Those which have changed the least, doubtless because their
domestication is of shorter standing and because they do not live in a
foreign climate, none the less display great differences in some of their
parts, as a result of the habits which we have made them contract.
Thus our domestic ducks and geese are of the same type as wild
ducks and geese ; but ours have lost the power of rising into high
regions of the air and flying across large tracts of country ; more-
over, a real change has come about in the state of their parts, as com-
pared with those of the animals of the race from which they come.

Who does not know that if we rear some bird of our own climate
in a cage and it lives there for five or six years, and if we then return
it to nature by setting it at liberty, it is no longer able to fly hke its
fellows, which have always been free ? The slight change of environ-
ment for this individual has indeed only diminished its power of flight,
and doubtless has worked no change in its structure ; but if a long
succession of generations of individuals of the same race had been
kept in captivity for a considerable period, there is no doubt that even
the structure of these individuals would gradually have undergone
notable changes. Still more, if instead of a mere continuous captivity,
this environmental factor had been further accompanied by a change
to a very different climate ; and if these individuals had by degrees
been habituated to other kinds of food and other activities for seizing
it, these factors when combined together and become permanent
would have unquestionably given rise imperceptibly to a new race
with quite special characters.

Where in natural conditions do we find that multitude of races of
dogs which now actually exist, owing to the domestication to which
we have reduced them ? Where do we find those bull-dogs, grey-
hounds, water-spaniels, spaniels, lap-dogs, etc., etc. ; races which
show wider differences than those which we call specific when they
occur among animals of one genus living in natural freedom ?

No doubt a single, original race, closely resembUng the wolf, if
indeed it was not actually the wolf, was at some period reduced by
man to domestication. That race, of which all the individuals were
then ahke, was gradually scattered with man into different countries
and climates ; and after they had been subjected for some time to

INFLUENCE OF ENVIRONMENT 111

the influences of their environment and of the various habits which
had been forced upon them in each country, they underwent remark-
able alterations and formed various special races. Now man travels
about to very great distances, either for trade or any other purpose ;
and thus brings into thickly populated places, such as a great capital,
various races of dogs formed in very distant countries. The crossing
of these races by reproduction then gave rise in turn to all those that
we now know.

The following fact proves in the case of plants how the change of
some important factor leads to alteration in the parts of these living
bodies.

So long as Ranunculus aquatilis is submerged in the water, all its
leaves are finely divided into minute segments ; but when the stem
of this plant reaches the surface of the water, the leaves which develop
in the air are large, round and simply lobed. If several feet of the same
plant succeed in growing in a soil that is merely damp without any
immersion, their stems are then short, and none of their leaves are
broken up into minute divisions, so that we get Ranunculus hederaceus,
which botanists regard as a separate species.

There is no doubt that in the case of animals, extensive alterations
in their customary environment produce corresponding alterations
in their parts ; but here the transformations take place much more
slowly than in the case of plants ; and for us therefore they are less
perceptible and their cause less readily identified.

As to the conditions which have so much power in modifying the
organs of living bodies, the most potent doubtless consist in the
diversity of the places where they live, but there are many others
as well which exercise considerable influence in producing the effects
in question.

It is known that localities differ as to their character and quality,
by reason of their position, construction and chmate : as is readily
perceived on passing through various localities distinguished by
special qualities ; this is one cause of variation for animals and plants
living in these various places. But what is not known so well and
indeed what is not generally beheved, is that every locality itself
changes in time as to exposure, cHmate, character and quahty, although
with such extreme slowness, according to our notions, that we ascribe
to it complete stability.

Now in both cases these altered locahties involve a corresponding
alteration in the environment of the living bodies that dwell there,
and this again brings a new influence to bear on these same bodies.

Hence it follows that if there are extremes in these alterations,
there are also finer differences : that is to say, intermediate stages

112 ZOOLOGICAL PHILOSOPHY

which fill up the interval. Consequently there are also fine distinctions
between what we call species.

It is obvious then that as regards the character and situation of the
substances which occupy the various parts of the earth's surface,
there exists a variety of environmental factors which induces a
corresponding variety in the shapes and structure of animals, inde-
pendent of that special variety which necessarily results from the
progress of the complexity of organisation in each animal.

In every locality where animals can live, the conditions constituting
any one order of things remain the same for long periods : indeed they
alter so slowly that man cannot directly observe it. It is only by an
inspection of ancient monuments that he becomes convinced that in
each of these localities the order of things w^hich he now finds has
not always been existent ; he may thence infer that it will go on
changing.

Races of animals living in any of these localities must then retain
their habits equally long : hence the apparent constancy of the races
that we call species, — a constancy which has raised in us the belief
that these races are as old as nature.

But in the various habitable parts of the earth's surface, the character
and situation of places and climates constitute both for animals and
plants environmental influences of extreme variability. The animals
living in these various localities must therefore differ among themselves,
not only by reason of the state of complexity of organisation attained
in each race, but also by reason of the habits which each race is forced
to acquire ; thus when the observing naturalist travels over large
portions of the earth's surface and sees conspicuous changes occurring
in the environment, he invariably finds that the characters of species
undergo a corresponding change.

Now the true principle to be noted in all this is as follows :

1 . Every fairly considerable and permanent alteration in the environ-
ment of any race of animals works a real alteration in the needs of that
race.

2. Every change in the needs of animals necessitates new activities
on their part for the satisfaction of those needs, and hence new habits.

3. Every new need, necessitating new activities for its satisfaction,
requires the animal, either to make more frequent use of some of its
parts which it previously used less, and thus greatly to develop and
enlarge them ; or else to make use of entirely new parts, to which
the needs have imperceptibly given birth by efforts of its inner feeling ;
this I shall shortly prove by means of known facts.

Thus to obtain a knowledge of the true causes of that great diversity
of shapes and habits found in the various known animals, we must

INFLUENCE OF ENVIRONMENT 113

reflect that the infinitely diversified but slowly changing environment
in which the animals of each race have successively been placed,
has involved each of them in new needs and corresponding alterations
in their habits. This is a truth which, once recognised, cannot be
disputed. Now we shall easily discern how the new needs may have
been satisfied, and the new habits acquired, if we pay attention to the
two following laws of nature, which are always verified by observation.

First Law.

In every animal which has not passed the limit of its develo'pment,
a more frequent and continuous use of any organ gradually strengthens,
develops and enlarges that organ, and gives it a power proportional to
the length of time it has been so used ; while the permanent disuse of
any organ imperceptibly iveakens and deteriorates it, and progressively
diminishes its functional capacity, until it finally disappears.

Second Law.

All the acquisitions or losses wrought by nature on individuals, through
the influence of the environment in which their race has long been placed,
and hence through the influence of the predominant u^e or permanent
disuse of any organ ; all these are preserved by reproduction to the new
individuals which arise, provided that the acquired modifications are
common to both sexes, or at least to the individuals which produce the
young.

Here we have two permanent truths, which can only be doubted
by those who have never observed or followed the operations of nature,
or by those who have allowed themselves to be drawn into the error
which I shall now proceed to combat.

Naturalists have remarked that the structure of animals is always
in perfect adaptation to their functions, and have inferred that the
shape and condition of their parts have determined the use of them.
Now this is a mistake : for it may be easily proved by observation
that it is on the contrary the needs and uses of the parts which have
caused the development of these same parts, which have even given
birth to them when they did not exist, and which consequently have
given rise to the condition that we find in each animal.

If this were not so, nature would have had to create as many different
kinds of structure in animals, as there are different kinds of environ-
ment in which they have to live ; and neither structure nor environ-
ment would ever have varied.

This is indeed far from the true order of things. If things were
really so, we should not have race-horses shaped hke those in England ;

114 ZOOLOGICAL PHILOSOPHY

we should not have big draught- horses so heavy and so different from
the former, for none such are produced in nature ; in the same way
we should not have basset-hounds with crooked legs, nor grey-hounds
so fleet of foot, nor water-spaniels, etc. ; we should not have fowls with-
out tails, fantail pigeons, etc. ; finally, we should be able to cultivate
wild plants as long as we liked in the rich and fertile soil of our gardens,
without the fear of seeing them change under long cultivation.

A feeling of the truth in this respect has long existed ; since the
following maxim has passed into a proverb and is known by all.
Habits form a second nature.

Assuredly if the habits and nature of each animal could never vary,
the proverb would have been false and would not have come into
existence, nor been preserved in the event of any one suggesting it.

If we seriously reflect upon all that I have just set forth, it will be
seen that I was entirely justified when in my work entitled Recherches
sur les corps vivants (p. 50), I estabhshed the following proposition :

"It is not the organs, that is to say, the nature and shape of the
parts of an animal's body, that have given rise to its special habits
and faculties ; but it is, on the contrary, its habits, mode of life and
environment that have in course of time controlled the shape of its body,
the number and state of its organs and, lastly, the faculties which it
possesses."

If this proposition is carefully weighed and compared with all the
observations that nature and circumstances are incessantly throwing
in our way, we shall see that its importance and accuracy are sub-
stantiated in the highest degree.

Time and a favourable environment are as I have already said
nature's two chief methods of bringing all her productions into exist-
ence : for her, time has no limits and can be drawn upon to any
extent.

As to the various factors which she has required and still constantly
uses for introducing variations in everything that she produces, they
may be described as practically inexhaustible.

The principal factors consist in the influence of cUmate, of the vary-
ing temperatures of the atmosphere and the whole environment,
of the variety of localities and their situation, of habits, the com-
monest movements, the most frequent activities, and, lastly, of the
means of self-preservation, the mode of life and the methods of
defence and multiplication.

Now as a result of these various influences, the faculties become
extended and strengthened by use, and diversified by new habits
that are long kept up. The conformation, consistency and, in short,
the character and state of the parts, as well as of the organs, are

INFLUENCE OF ENVIRONMENT 115

imperceptibly affected by these influences and are preserved and
propagated by reproduction.

These truths, which are merely effects of the two natural laws
stated above, receive in every instance striking confirmation from
facts ; for the facts afford a clear indication of nature's procedure in
the diversity of her productions.

But instead of being contented with generalities which might be
considered hypothetical, let us investigate the facts directly, and
consider the effects in animals of the use or disuse of their organs
on these same organs, in accordance with the habits that each race
has been forced to contract.

Now I am going to prove that the permanent disuse of any organ
first decreases its functional capacity, and then gradually reduces
the organ and causes it to disappear or even become extinct, if this
disuse lasts for a very long period throughout successive generations
of animals of the same race.

I shall then show that the habit of using any organ, on the con-
trary, in any animal which has not reached the limit of the decHne
of its functions, not only perfects and increases the functions of that
organ, but causes it in addition to take on a size and development
which imperceptibly alter it ; so that in course of time it becomes
very different from the same organ in some other animal which uses
it far less.

The 'permanent disuse of an organ, arising from a change of habits,
causes a gradual shrinkage and ultimately the disappearance and even
extinction of that organ.

Since such a proposition could only be accepted on proof, and not
on mere authority, let us endeavour to make it clear by citing the chief
known facts which substantiate it.

The vertebrates, whose plan of organisation is almost the same
throughout, though with much variety in their parts, have their jaws
armed with teeth ; some of them, however, whose environment has
induced the habit of swallowing the objects they feed on without any
preliminary mastication, are so affected that their teeth do not develop.
The teeth then remain hidden in the bony framework of the jaws,
without being able to appear outside ; or indeed they actually become
extinct down to their last rudiments.

In the right-whale, which was supposed to be completely destitute
of teeth, M. Geoffroy has nevertheless discovered teeth concealed
in the jaws of the foetus of this animal. The professor has moreover
discovered in birds the groove in which the teeth should be placed,
though they are no longer to be found there.

116 ZOOLOGICAL PHILOSOPHY

Even in the class of mammals, comprising the most perfect animals,
where the vertebrate plan of organisation is carried to its highest
completion, not only is the right-whale devoid of teeth, but the
ant-eater (Myrmecophaga) is also found to be in the same condition,
since it has acquired a habit of carrying out no mastication, and has
long preserved this habit in its race.

Eyes in the head are characteristic of a great number of different
animals, and essentially constitute a part of the plan of organisation
of the vertebrates.

Yet the mole, whose habits require a very small use of sight, has
only minute and hardly visible eyes, because it uses that organ so
little.

Olivier's Spalax (Voyage en Egypte et en Perse), which lives under-
ground like the mole, and is apparently exposed to dayhght even less
than the mole, has altogether lost the use of sight : so that it shows
nothing more than vestiges of this organ. Even these vestiges are
entirely hidden under the skin and other parts, which cover them up
and do not leave the shghtest access to light.

The Proteus, an aquatic reptile alhed to the salamanders, and living
in deep dark caves under the water, has, like the Spalax, only vestiges
of the organ of sight, vestiges which are covered up and hidden in the
same way.

The following consideration is decisive on the question which I
am now discussing.

Light does not penetrate everywhere ; consequently animals which
habitually live in places where it does not penetrate, have no oppor-
tunity of exercising their organ of sight, if nature has endowed
them with one. Now animals belonging to a plan of organisation of
which eyes were a necessary part, must have originally had them.
Since, however, there are found among them some which have lost
the use of this organ and which show nothing more than hidden and
covered up vestiges of them, it becomes clear that the shrinkage and
even disappearance of the organ in question are the results of a per-
manent disuse of that organ.

This is proved by the fact that the organ of hearing is never in this
condition, but is always found in animals whose organisation is of the
kind that includes it : and for the following reason.

The substance of sound, ^ that namely which, when set in motion by
the shock or the vibration of bodies, transmits to the organ of hearing

^ Physicists believe and even afiSrm that the atmospheric air is the actual sub-
stance of sound, that is to say, that it is the substance which, when set in motion
by the shocks or vibrations of bodies, transmits to the organ of hearing the impression
of the concussions received.

That this is an error is attested by many known facts, showing that it is impossible

INFLUENCE OF ENVIRONMENT li7

the impression received, penetrates everywhere and passes through
any medium, including even the densest bodies : it follows that every
animal, belonging to a plan of organisation of which hearing is an
essential part, always has some opportunity for the exercise of this
organ wherever it may live. Hence among the vertebrates we do not
find any that are destitute of the organ of hearing ; and after them,
when this same organ has come to an end, it does not subsequently
recur in any animal of the posterior classes.

It is not so with the organ of sight ; for this organ is found to
disappear, re-appear and disappear again according to the use that
the animal makes of it.

In the acephalic molluscs, the great development of the mantle
would make their eyes and even their head altogether useless. The
permanent disuse of these organs has thus brought about their dis-
appearance and extinction, although molluscs belong to a plan of
organisation which should comprise them.

Lastly, it was part of the plan of organisation of the reptiles, as of
other vertebrates, to have four legs in dependence on their skeleton.
Snakes ought consequently to have four legs, especially since they are
bv no means the last order of the reptiles and are farther from the
fishes than are the batrachians (frogs, salamanders, etc.).

Snakes, however, have adopted the habit of crawling on the ground
and hiding in the grass ; so that their body, as a result of continually
repeated efforts at elongation for the purpose of passing through
narrow spaces, has acquired a considerable length, quite out of pro-
portion to its size. Now, legs would have been quite useless to these
animals and consequently unused. Long legs would have interfered

that the air should penetrate to all places to which the substance producing aound
actually does penetrate.

See my memoir On the Substance of Sound, printed at the end of my Hydrogéologie,
p. 225, in which I furnished the proofs of this mistake.

Since the pubUcation of my memoir, which by the way is seldom cited, great efforts
have been made to make the known velocity of the propagation of sound in air tally
with the elasticity of the air, which would cause the propagation of its oscillations
to be too slow for the theory. Now, since the air during oscillation necessarily under-
goes alternate compressions and dilatations in its parts, recourse has been had to
the effects of the caloric squeezed out during the sudden compressions of the air and
of the caloric absorbed during the rarefactions of that fluid. By means of these
effects, quantitatively determined by convenient hypotheses, geometricians now account
for the velocity with which sound is propagated through air. But this is no answer
to the fact that sound is also propagated through bodies which air can neither traverse
nor set in motion.

These physicists assume forsooth a vibration in the smallest particles of solid
bodies ; a vibration of very dubious existence, since it can only be propagated through
homogeneous bodies of equal density, and cannot spread from a dense body to a
rarefied one or vice versa. Such a hypothesis offers no explanation of the well-known
fact that sound is propagated through heterogeneous bodies of very different densities
and kinds.

118 ZOOLOGICAL PHILOSOPHY

with their need of crawUng, and very short legs would have been
incapable of moving their body, since they could only have had four.
The disuse of these parts thus became permanent in the various races
of these animals, and resulted in the complete disappearance of these
same parts, although legs really belong to the plan of organisation of
the animals of this class.

Many insects, which should have wings according to the natural
characteristics of their order and even of their genus, are more or less
completely devoid of them through disuse. Instances are furnished
by many Coleoptera, Orthoptera, Hymenoptera and Hemiptera, etc.,
where the habits of these animals never involve them in the necessity
of using their wings.

But it is not enough to give an explanation of the cause which has
brought about the present condition of the organs of the various
animals,— a condition that is always found to be the same in animals
of the same species ; we have in addition to cite instances of changes
wrought in the organs of a single individual during its life, as the
exclusive result of a great mutation in the habits of the individuals
of its species. The following very remarkable fact will complete the
proof of the influence of habits on the condition of the organs, and of
the way in which permanent changes in the habits of an individual
lead to others in the condition of the organs, which come into action
during the exercise of these habits.

M. Tenon, a member of the Institute, has notified to the class of
sciences, that he had examined the intestinal canal of several men who
had been great drinkers for a large part of their lives, and in every
case he had found it shortened to an extraordinary degree, as compared
with the same organ in all those who had not adopted the like
habit.

It is known that great drinkers, or those who are addicted to drunken-
ness, take very little sohd food, and eat hardly anything ; since the
drink which they consume so copiously and frequently is sufiicient
to feed them.

Now since fluid foods, especially spirits, do not long remain either
in the stomach or intestine, the stomach and the rest of the intestinal
canal lose among drinkers the habit of being distended, just as among
sedentary persons, who are continually engaged on mental work and
are accustomed to take very little food ; for in their case also the
stomach slowly shrinks and the intestine shortens.

This has nothing to do with any shrinkage or shortening due to a
binding of the parts which would permit of the ordinary extension,
if instead of remaining empty these viscera were again filled ; we
have to do with a real shrinkage and shortening of considerable extent,

INFLUENCE OF ENVIRONMENT 119

and such that these organs would burst rather than yield at once to
any demand for the ordinary extension.

Compare two men of equal ages, one of whom has contracted the
habit of eating very little, since his habitual studies and mental work
have made digestion difficult, while the other habitually takes much
exercise, is often out-of-doors, and eats well ; the stomach of the first
will have very little capacity left and will be filled up by a very small
quantity of food, while that of the second will have preserved and
even increased its capacity.

Here then is an organ which undergoes profound modification in
size and capacity, purely on account of a change of habits during the
life of the individual.

The frequent use of any organ, when confirmed by habit, increases the
functions of that organ, leads to its development and endows it with a
size and power that it does not possess in animals which exercise it less.

We have seen that the disuse of any organ modifies, reduces and
finally extinguishes it. I shall now prove that the constant use of
any organ, accompanied by efforts to get the most out of it, strengthens
and enlarges that organ, or creates new ones to carry on functions
that have become necessary.

The bird which is drawn to the water by its need of finding there
the prey on which it lives, separates the digits of its feet in trying to
strike the water and move about on the surface. The skin which unites
these digits at their base acquires the habit of being stretched by these
continually repeated separations of the digits ; thus in course of time
there are formed large webs which unite the digits of ducks, geese,
etc., as we actually find them. In the same way efforts to swim,
that is to push against the water so as to move about in it, have
stretched the membranes between the digits of frogs, sea-tortoises,
the otter, beaver, etc.

On the other hand, a bird which is accustomed to perch on trees
and which springs from individuals all of whom had acquired this habit,
necessarily has longer digits on its feet and differently shaped from those
of the aquatic animals that I have just named. Its claws in time be-
come lengthened, sharpened and curved into hooks, to clasp the
branches on which the animal so often rests.

We find in the same way that the bird of the water-side which does
not like swimming and yet is in need of going to the water's edge
to secure its prey, is continually liable to sink in the mud. Now this
bird tries to act in such a way that its body should not be immersed
in the liquid, and hence makes its best efforts to stretch and lengthen
its legs. The long-established habit acquired by this bird and all

120 ZOOLOGICAL PHILOSOPHY

its race of continually stretching and lengthening its legs, results in
the individuals of this race becoming raised as though on stilts, and
gradually obtaining long, bare legs, denuded of feathers up to the
thighs and often higher still. {Système des Animaux sans vertèbres, p. 14. )

We note again that this same bird wants to fish without wetting
its body, and is thus obhged to make continual efforts to lengthen
its neck. Now these habitual efforts in this individual and its race
must have resulted in course of time in a remarkable lengthening,
as indeed we actually find in the long necks of all water-side birds.

If some swimming birds like the swan and goose have short legs
and yet a very long neck, the reason is that these birds while moving
about on the water acquire the habit of plunging their head as deeply
as they can into it in order to get the aquatic larvae and various
animals on which they feed ; whereas they make no effort to lengthen
their legs.

If an animal, for the satisfaction of its needs, makes repeated efforts
to lengthen its tongue, it will acquire a considerable length (ant-eater,
green-woodpecker) ; if it requires to seize anything with this same
organ, its tongue will then divide and become forked. Proofs of my
statement are found in the humming-birds which use their tongues
for grasping things, and in lizards and snakes which use theirs to
palpate and identify objects in front of them.

Needs which are always brought about by the environment, and the
subsequent continued efforts to satisfy them, are not hmited in their
results to a mere modification, that is to say, an increase or decrease
of the size and capacity of organs ; but they may even go so far as
to extinguish organs, when any of these needs make such a course
necessary.

Fishes, which habitually swim in large masses of water, have need of
lateral vision ; and, as a matter of fact, their eyes are placed on the
sides of their head. Their body, which is more or less flattened
according to the species, has its edges perpendicular to the plane
of the water ; and their eyes are placed so that there is one on each
flattened side. But such fishes as are forced by their habits to be
constantly approaching the shore, and especially sUghtlv inclined or
gently sloping beaches, have been compelled to swim on their flattened
surfaces in order to make a close approach to the water's edge. In
this position, they receive more light from above than below and stand
in special need of paying constant attention to what is passing above
them ; this requirement has forced one of their eyes to undergo a
sort of displacement, and to assume the very remarkable position
found in the soles, turbots, dabs, etc. {Pleuronectes and Achirus). The
position of these eyes is not symmetrical, because it results from an

INFLUENCE OF ENVIRONMENT 121

incomplete mutation. Now this mutation is entirely completed in
the skates, in which the transverse flattening of the body is altogether
horizontal, like the head. Accordingly the eyes of skates are both
situated on the upper surface and have become symmetrical.

Snakes, which crawl on the surface of the earth, chiefly need to see
objects that are raised or above them. This need must have had its
effect on the position of the organ of sight in these animals, and accord-
ingly their eyes are situated in the lateral and upper parts of their
head, so as easily to perceive what is above them or at their sides ; but
they scarcely see at all at a very short distance in front of them. They
are, however, compelled to make good the deficiency of sight as regards
objects in front of them which might injure them as they move forward.
For this purpose they can only use their tongue, which they are
obliged to thrust out with all their might. This habit has not only
contributed to making their tongue slender and very long and con-
tractile, but it has even forced it to undergo division in the greater
number of species, so as to feel several objects at the same time ;
it has even permitted of the formation of an aperture at the extremity
of their snout, to allow the tongue to pass without having to separate
the jaws.

Nothing is more remarkable than the effects of habit in herbivorous
mammals.

A quadruped, whose environment and consequent needs have for
long past inculcated the habit of browsing on grass, does nothing but
walk about on the ground ; and for the greater part of its life is
obliged to stand on its four feet, generally making only few or moderate
movements. The large portion of each day that this kind of animal
has to pass in filling itself with the only kind of food that it cares for,
has the result that it moves but little and only uses its feet for support
in walking or running on the ground, and never for holding on, or
chmbing trees.

From this habit of continually consuming large quantities of food-
material, which distend the organs receiving it, and from the habit
of making only moderate movements, it has come about that the body
of these animals has greatly thickened, become heavy and massive
and acquired a very great size : as is seen in elephants, rhinoceroses,
oxen, buffaloes, horses, etc.

The habit of standing on their four feet during the greater part of
the day, for the purpose of browsing, has brought into existence a
thick horn which invests the extremity of their digits ; and since
these digits have no exercise and are never moved and serve no other
purpose than that of support like the rest of the foot, most of them
have become shortened, dwindled and, finally, even disappeared.

122 ZOOLOGICAL PHILOSOPHY

Thus in the pachyderms, some have five digits on their feet invested
in horn, and their hoof is consequently divided into five parts ; others
have only four, and others again not more than three ; but in the
ruminants, which are apparently the oldest of the mammals that are
permanently confined to the ground, there are not more than two
digits on the feet and indeed, in the solipeds, there is only one (horse,
donkey).

Nevertheless some of these herbivorous animals, especially the
ruminants, are incessantly exposed to the attacks of carnivorous
animals in the desert countries that they inhabit, and they can only
find safety in headlong flight. Necessity has in these cases forced
them to exert themselves in swift running, and from this habit their
body has become more slender and their legs much finer ; instances
are furnished by the antelopes, gazelles, etc.

In our own climates, there are other dangers, such as those con-
stituted by man, with his continual pursuit of red deer, roe deer and
fallow deer ; this has reduced them to the same necessity, has impelled
them into similar habits, and had corresponding effects.

Since ruminants can only use their feet for support, and have little
strength in their jaws, which only obtain exercise by cutting and
browsing on the grass, they can only fight by blows with their heads,
attacking one another with their crowns.

In the frequent fits of anger to which the males especially are subject,
the efforts of their inner feeling cause the fluids to flow more strongly
towards that part of their head ; in some there is hence deposited
a secretion of horny matter, and in others of bony matter mixed with
horny matter, which gives rise to solid protuberances : thus we have
the origin of horns and antlers, with which the head of most of these
animals is armed.

It is interesting to observe the result of habit in the peculiar shape
and size of the giraffe (Camelo-pardalis) : this animal, the largest of
the mammals, is known to live in the interior of Africa in places where
the soil is nearly always arid and barren, so that it is obliged to browse
on the leaves of trees and to make constant efforts to reach them.
From this habit long maintained in all its race, it has resulted that
the animal's fore-legs have become longer than its hind legs, and that
its neck is lengthened to such a degree that the giraffe, without standing
up on its hind legs, attains a height of six metres (nearly 20 feet).

Among birds, ostriches, which have no power of flight and are raised
on very long legs, probably owe their singular shape to analogous
circumstances.

The effect of habit is quite as remarkable in the carnivorous mammals
as in the herbivores ; but it exhibits results of a different kind.

INFLUENCE OF ENVIRONMENT 123

Those carnivores, for instance, which have become accustomed to
climbing, or to scratching the ground for digging holes, or to tearing
their prey, have been under the necessity of using the digits of their
feet : now this habit has promoted the separation of their digits, and
given rise to the formation of the claws with which they are armed.

But some of the carnivores are obliged to have recourse to pursuit
in order to catch their prey : now some of these animals were compelled
by their needs to contract the habit of tearing with their claws, which
they are constantly burying deep in the body of another animal in
order to lay hold of it, and then make efforts to tear out the part seized.
These repeated efforts must have resulted in its claws reaching a size
and curvature which would have greatly impeded them in walking or
running on stony ground : in such cases the animal has been compelled
to make further efforts to draw back its claws, which are so pro-
jecting and hooked as to get in its way. From this there has gradually
resulted the formation of those pecuhar sheaths, into which cats,
tigers, lions, etc. withdraw their claws when they are not using them.

Hence we see that efforts in a given direction, when they are long
sustained or habitually made by certain parts of a living body, for
the satisfaction of needs established by nature or environment, cause
an enlargement of these parts and the acquisition of a size and shape
that they would never have obtained, if these efforts had not become
the normal activities of the animals exerting them. Instances are
everywhere furnished by observations on all known animals.

Can there be any more striking instance than that which we find
in the kangaroo ? This animal, which carries its young in a pouch
under the abdomen, has acquired the habit of standing upright, so
as to rest only on its hind legs and tail ; and of moving only by means
of a succession of leaps, during which it maintains its erect attitude
in order not to disturb its young. And the following is the result :

1. Its fore legs, which it uses very little and on which it only supports
itself for a moment on abandoning its erect attitude, have never
acquired a development proportional to that of the other parts, and
have remained meagre, very short and with very little strength.

2. The hind legs, on the contrary, which are almost continually
in action either for supporting the whole body or for making leaps,
have acquired a great development and become very large and strong.

3. Lastly, the tail, which is in this case much used for supporting
the animal and carrying out its chief movements, has acquired an
extremely remarkable thickness and strength at its base.

These well-known facts are surely quite sufficient to establish the
results of habitual use on an organ or any other part of animals. If
on observing in an animal any organ particularly well-developed.

124 ZOOLOGICAL PHILOSOPHY

strong, and powerful, it is alleged that its habitual use has nothing to
do with it, that its continued disuse involves it in no loss, and finally,
that this organ has always been the same since the creation of the species
to which the animal belongs, then I ask. Why can our domestic ducks
no longer fly like wild ducks ? I can, in short, cite a multitude of in-
stances among ourselves, which bear witness to the differences that
accrue to us from the use or disuse of any of our organs, although these
differences are not preserved in the new individuals which arise by
reproduction : for if they were their effects would be far greater.

I shall show in Part II., that when the will guides an animal to any
action, the organs which have to carry out that action are immediately
stimulated to it by the influx of subtle fluids (the nervous fluid),
which become the determining factor of the movements required.
This fact is verified by many observations, and cannot now be called
in question.

Hence it follows that numerous repetitions of these organised
activities strengthen, stretch, develop and even create the organs
necessary to them. We have only to watch attentively what is
happening all around us, to be convinced that this is the true cause
of organic development and changes.

Now every change that is wrought in an organ through a habit
of frequently using it, is subsequently preserved by reproduction,
if it is common to the individuals who unite together in fertilisation
for the propagation of their species. Such a change is thus handed
on to all succeeding individuals in the same environment, without
their having to acquire it in the same way that it was actually created.

Furthermore, in reproductive imions, the crossing of individuals
who have different quaUties or structures is necessarily opposed to
the permanent propagation of these quahties and structures. Hence
it is that in man, who is exposed to so great a diversity of environment,
the accidental quaUties or defects which he acquires are not preserved
and propagated by reproduction. If, when certain peculiarities
of shape or certain defects have been acquired, two individuals who
are both affected were always to unite together, they would hand on
the same peculiarities ; and if successive generations were limited
to such unions, a special and distinct race would then be formed. But
perpetual crossings between individuals, who have not the same
peculiarities of shape, cause the disappearance of all pecuUarities
acquired by special action of the environment. Hence, we may be sure
that if men were not kept apart by the distances of their habitations,
the crossing in reproduction would soon bring about the disappear-
ance of the general characteristics distinguishing different nations.

If I intended here to pass in review all the classes, orders, genera

INFLUENCE OF ENVIRONMENT 126

and species of existing animals, I should be able to show that the
conformation and structure of individuals, their organs, faculties,
etc., etc., are everywhere a pure result of the environment to which
each species is exposed by its nature, and by the habits that the
individuals composing it have been compelled to acquire ; I should
be able to show that they are not the result of a shape which existed
from the beginning, and has driven animals into the habits they are
known to possess.

It is known that the animal called the at or sloth (Bradypustridactylus)
is permanently in a state of such extreme weakness that it only executes
very slow and limited movements, and walks on the ground with
difficulty. So slow are its movements that it is alleged that it can only
take fifty steps in a day. It is known, moreover, that the organisation
of this animal is entirely in harmony with its state of feebleness and
incapacity for walking ; and that if it wished to make other movements
than those which it actually does make it could not do so.

Hence on the supposition that this animal had received its organisa-
tion from nature, it has been asserted that this organisation forced
it into the habits and miserable state in which it exists.

This is very far from being my opinion ; for I am convinced that
the habits which the ai was originally forced to contract must
necessarily have brought its organisation to its present condition.

If continual dangers in former times have led the individuals of
this species to take refuge in trees, to live there habitually and feed
on their leaves, it is clear that they must have given up a great number
of movements which animals living on the ground are in a position
to perform. All the needs of the ai will then be reduced to clinging
to branches and crawling and dragging themselves among them,
in order to reach the leaves, and then to remaining on the tree in a
state of inactivity in order to avoid falling off. This kind of inactivity,
moreover, must have been continually induced by the heat of the
climate ; for among warm-blooded animals, heat is more conducive
to rest than to movement.

Now the individuals of the race of the ai have long maintained this
habit of remaining in the trees, and of performing only those slow
and Uttle varied movements which suffice for their needs. Hence
their organisation will gradually have come into accordance with
their new habits ; and from this it must follow :

1. That the arms of these animals, which are making continual
efforts to clasp the branches of trees, will be lengthened ;

2. That the claws of their digits will have acquired a great length
and a hooked shape, through the continued efforts of the animal to
hold on ;

126 ZOOLOGICAL PHILOSOPHY

3. That their digits, which are never used in making independent
movements, will have entirely lost their mobility, become united
and have preserved only the faculty of flexion or extension all
together ;

4. That their thighs, which are continually clasping either the trunk
or large branches of trees, will have contracted a habit of always being
separated, so as to lead to an enlargement of the pelvis and a back-
ward direction of the cotyloid cavities ;

5. Lastly, that a great many of their bones will be welded together,
and that parts of their skeleton will consequently have assumed an
arrangement and form adapted to the habits of these animals, and
different from those which they would require for other habits.

This is a fact that can never be disputed ; since nature shows
us in innumerable other instances the power of environment over
habit and that of habit over the shape, arrangement and proportion»
of the parts of animals.

Since there is no necessity to cite any further examples, we may
now turn to the main point elaborated in this discussion.

It is a fact that all animals have special habits corresponding to-
their genus and species, and always possess an organisation that is
completely in harmony with those habits.

It seems from the study of this fact that we may adopt one or other
of the two following conclusions, and that neither of them can be
verified.

Conclusion adopted hitherto : Nature (or her Author) in creating
animals, foresaw all the possible kinds of environment in which they
would have to live, and endowed each species with a fixed organisa-
tion and with a definite and invariable shape, which compel each
species to live in the places and climates where we actually find them,
and there to maintain the habits which we know in them.

My individual conclusion : Nature has produced all the species
of animals in succession, beginning with the most imperfect or simplest,
and ending her work with the most perfect, so as to create a gradually
increasing complexity in their organisation ; these animals have
spread at large throughout all the habitable regions of the globe,
and every species has derived frorh its environment the habits that
we find in it and the structural modifications which observation
shows us.

The former of these two conclusions is that which has been drawn
hitherto, at least by nearly everyone : it attributes to every animal
a fixed organisation and structure which never have varied and never
do vary ; it assumes, moreover, that none of the localities inhabited
by animals ever vary ; for if they were to vary, the same animals

INFLUENCE OF ENVIRONMENT 127

could no longer survive, and the possibility of finding other localities
and transporting themselves thither would not be open to them.

The second conclusion is my own : it assumes that by the influence
of environment on habit, and thereafter by that of habit on the state of
the parts and even on organisation, the structure and organisation
of any animal may undergo modifications, possibly very great, and
capable of accounting for the actual condition in which all animals
are found.

In order to show that this second conclusion is baseless, it must
first be proved that no point on the surface of the earth ever under-
goes variation as to its nature, exposure, high or low situation, climate,
etc., etc. ; it must then be proved that no part of animals undergoes
even after long periods of time any modification due to a change of
environment or to the necessity which forces them into a different
kind of life and activity from what has been customary to them.

Now if a single case is sufficient to prove that an animal which has
long been in domestication differs from the wild species whence it
sprang, and if in any such domesticated species, great differences
of conformation are found between the individuals exposed to such a
habit and those which are forced into different habits, it will then be
certain that the first conclusion is not consistent with the laws of
nature, while the second, on the contrary, is entirely in accordance
with them.

Everything then combines to prove my statement, namely : that
it is not the shape either of the body or its parts which gives rise to
the habits of animals and their mode of life ; but that it is, on the con-
trary, the habits, mode of life and all the other influences of the environ-
ment which have in course of time built up the shape of the body and
of the parts of animals. With new shapes, new faculties have been
acquired, and little by Httle nature has succeeded in fashioning animals
such as we actually see them.

Can there be any more important conclusion in the range of natural
history, or any to which more attention should be paid than that
which I have just set forth ?

Let us conclude this Part I. with the principles and exposition of
the natural order of animals.

CHAPTER VIII.

or THE NATURAL ORDER OF ANIMALS, AND THE WAY IN WHICH
THEIR CLASSIFICATION SHOULD BE DRAWN UP SO AS TO BE
IN CONFORMITY WITH THE ACTUAL ORDER OF NATURE.

I HAVE already observed that the true aim of a classification of animals
should not be merely the possession of a list of classes, genera and species,
but also the provision of the greatest facilities for the study of nature
and for obtaining a knowledge of her procedure, methods and laws.

I do not hesitate to say, however, that our general classifications of
animals up to the present have been in the inverse order from that
followed by nature when bringing her Uving productions successively
into existence ; thus, when we proceed from the most complex to the
simplest in the usual way, we increase the difficulty of acquiring a
knowledge of the progress in complexity of organisation ; and we
also find it less easy to grasp both the causes of that progress and of
the interruptions in it.

When once we have recognised that a thing is useful and indeed
indispensable for the end in view and that it is free from drawbacks,
we should hasten to carry it into execution although it is contrary
to custom.

This is the case with regard to the way in which a general classi-
fication of animals should be drawn up.

We shall see that it is not a matter of indifference from which end
we begin this general classificatiori of animals, and that the beginning
of the order is not a mere matter of choice.

The existing custom of placing at the head of the animal kingdom
the most perfect animals, and of terminating this kingdom with the
most imperfect and simplest in organisation, is due, on the one hand,
to that natural prejudice towards giving the preference to the objects
which strike us most or in which we are most pleased or interested ;
and, on the other hand, to the preference for passing from the better
known to what is less known.

NATURAL ORDER OF ANIMALS 129

When the study of natural history began to occupy attention,
these reasons were no doubt very plausible ; but they must now
yield to the needs of science and especially to those of facilitating
the progress of natural knowledge.

With regard to the numerous and varied animals which nature
has produced, if we cannot flatter ourselves that we possess an exact
knowledge of the real order which she followed in bringing them
successively into existence, it is nevertheless true that the order
which I am about to set forth is probably very near it : reason and
all our acquired knowledge testify in favour of this probability.

If indeed it is true that all living bodies are productions of nature,
we are driven to the belief that she can only have produced them
one after another and not all in à moment. Now if she shaped
them one after another, there are grounds for thinking that she
began exclusively with the simplest, and only produced at the very
end the most complex organisations both of the animal and vegetable
kingdoms.

The botanists were the first to set an example to the zoologists as
to the proper way of drawing up a general classification in order to
represent the actual order of nature ; for it is with the Acotyledons
or agamous plants that they constitute the first class among plants,
that is to say, with the simplest in organisation and the most imperfect
under every aspect, plants in short which have no cotyledons, no
recognisable sex, no vessels in their tissue, and which in fact are com-
posed of nothing but cellular tissue more or less modified according
to their various expansions.

What botanists have done in the case of plants, we should now do
with regard to the animal kingdom ; and we should do it, not only
because nature herself indicates it and reason demands it, but also
because the natural order of classes in accordance with their growing
complexity of organisation is much easier to determine among animals
than it is in the case of plants.

While this order represents most closely the order of nature, it also
makes the study of objects much easier, advances our knowledge of
the organisation of animals with its increasing complexity from class
to class, and exhibits still more clearly the affinities existing among the
various stages of complexity of animal organisation, and the external
diiferences that we commonly utilise for the characterisation of classes,
orders, famihes, genera and species.

To these two principles, whose validity can scarcely be questioned,
I add another, viz. : that if nature, who has not succeeded in endowing
organised bodies with eternal existence, had not had the power of
giving these bodies the faculty of reproducing others hke themselves

130 ZOOLOGICAL PHILOSOPHY

to carry on and perpetuate the race in the same way, she would have
been forced to create directly all races, or rather she would only have
been able to create a single race in each organic kingdom, viz. the
simplest and most imperfect animals and plants.

Moreover, if nature had not been able to endow the organising activity
with the faculty of gradually increasing the complexity of organisation
by accelerating the energy of the movement of the fluids and hence
that of organic movement, and if she had not preserved by repro-
duction all the progress made in complexity of organisation and
all acquired improvements, she would assuredly never have produced
that infinitely varied multitude of animals and plants which differ
so greatly from one another both in their organisation and in their
faculties.

Finally, she could not create at once the highest faculties of animals,
for they are only found in conjunction with highly complex systems
of organs : and she had to prepare slowly the methods by which such
systems might be brought into existence.

Thus, in order to estabhsh the state of affairs that we now see in
hving bodies, the only direct production that is required from nature,
that is to say, the only production that occurs without the co-operation
of any organic activity, is in the case of the simplest organised bodies,
both of animals and plants ; these she continues to produce every
day in the same way at favourable times and places. Now she endows
these bodies, which she has herself created, with the faculties of feeding,
growing, multiplying, and always preserving the progress made in
organisation. She transmits these same faculties to all individuals
organically reproduced throughout time and the immense variety of
ever-changing conditions. By these means living bodies of all classes
and orders have been successively produced.

In the study of the natural order of animals, the very definite grada-
tion existing in the growing complexity of their organisation and in the
number and perfection of their faculties is very far from being a new
truth for it was known even to the Greeks ; ^ but they could not set
forth its underlying principles and proofs, because they lacked the
necessary knowledge.

Now, in order to facilitate an acquaintance with the principles
which have guided me in the exposition that I am about to give,
and in order to bring home more closely the gradation observed in
the complexity of organisation from the most imperfect animals at
the head of the series to the most perfect at the end of it, I have
divided into six distinct stages the various modes of organisation
recognised throughout the animal scale.

^ See the Voyage du jeune Anacharsis, by J. Barthélémy, vol. v. pp. 353, 354,

NATURAL ORDER OF ANIMALS

131

Of these six stages of organisation, the first four comprise the in-
vertebrate animals, and consequently the first ten classes of the animal
kingdom according to the new order that we are going to follow ; the
two last stages comprises all the vertebrate animals and consequently
the four (or five) last classes of animals.

By this method it will be easier to study and follow the procedure
of nature in the production of the animals that she has brought into
existence ; to recognise throughout the animal scale the progress
made in complexity of organisation and everywhere to verify both
the accuracy of the classification and the propriety of the rank
assigned by examining such characters and facts of organisation as
are known.

In lecturing on invertebrates at the Museum, I have for some years
past followed this plan of always proceeding from the simplest to
the most complex.

In order to bring out more clearly the arrangement and totahty
of the general series of animals, I shall first present a table of the
fourteen classes into which the animal kingdom is divided, confining
myself to a very brief account of their characters and of the stages
of organisation which they include.

TABLE

OF THE ARRANGEMENT AND CLASSIFICATION OF ANIMALS
ACCORDING TO THE ORDER MOST IN CONFORMITY WITH
THE ORDER OF NATURE,

INVERTEBRATE ANIMALS.

I. Infusorians. "^

Amorphous animals, reproducing by fission or
budding ; with bodies gelatinous, transparent,
homogeneous, contractile and microscopic ; no
radiating tentacles, or rotatory appendage ; no
special organ, even for digestion.

II. Polyps.

Reproducing by budding ; bodies gelatinous
and regenerating, but with no other internal
organ than an aUmentary canal with a single
aperture.

Terminal mouth, surrounded by radiating
tentacles or furnished with ciliated or rotatory
organs.

They mostly form compoimd animals.

Ist Stage.

No nerves ; no
vessels ; uo special-
ised internal organ
except for digestion.

132

ZOOLOGICAL PHILOSOPHY

III. Radiarians.

Suboviparous animals, free, with regenerating
bodies, destitute of head, eyes, or jointed legs ;
parts arranged radially. Mouth on inferior
surface.

IV. Worms.

Suboviparous animals, with soft regenerating
bodies ; undergoing no metamorphosis, and
never having eyes, jointed legs, nor a radial
arrangement of the internal parts.

2nd Stage.

No ganglionic
longitudinal cord ;
. no vessels for cir-
culation ; a few in-
ternal organs in addi-
tion to those of
digestion.

V. Insects.

Oviparous animals, which undergo meta-
morphosis, and have, in the perfect state, eyes
in their heads, six jointed legs, and tracheae
which spread everywhere ; a single fertilisation
in the course of their life.

VI. Arachnids.

Oviparous, having always jointed legs, and
eyes in their heads, and undergoing no meta-
morphosis. Limited trachae for respiration ; a
primitive circulation ; several fertilisations in
the course of their life.

Srd Stage.

Nerves terminat-
ing in a ganglionic
longitudinal cord ;
respiration by air-
carrying tracheae ;
circulation absent or
imperfect.

VII. Crustaceans.

Oviparous, with jointed body and Umbs,
crustaceous skin, eyes in their head, and usually
four antennae ; respiration by gills ; a ganglionic
longitudinal cord.

VIII. Annelids.

Oviparous, with elongated and ringed bodies ;
no jointed legs, rarely any eyes ; respiration by
gills ; a ganglionic longitudinal cord.

IX. CiRRHIPEDES.

Oviparous, with a mantle and jointed arms,
the skin of which is homy ; no eyes ; respira-
tion by gills ; ganglionic longitudinal cord.

X. Molluscs.

Oviparous, with soft moist bodies, unjointed,
and with a variable mantle ; respiration by
gills of various shapes and situations ; no spinal
cord, nor ganghonic longitudinal cord, but nerves
terminating in a brain.

4th Stage.

Nerves terminat-
ing in a brain or a
)> ganglionic longitud-
inal cord ; respira-
tion by gills ; arteries
and veins for circu-
lation.

NATURAL ORDER OF ANIMALS

133

VERTEBRATE ANIMALS.

CLASSES

XI. Fishes.

Oviparous, and without mammae ; respiration
complete and always by gills ; two or four
primitive limbs ; fins for locomotion ; no hair
or feathers on the skin.

XII. Reptiles.

Oviparous, and without mammae ; respiration
incomplete, usually by lungs which exist either
throughout life or during the latter part of it ;
four limbs, or two, or none ; no hair or feathers
on the skin.

5th Stage.

Nerves terminat-
ing in a brain which
is far from filling the
cranial cavity; heart
with one ventricle,
and the blood cold.

6th Stage.

Nerves terminat-
ing in a brain which
fills the cranial
cavity ; heart with
two ventricles, and
the blood warm.

XIII. Birds.

Oviparous, and without mammae ; four jointed
limbs, two of which are shaped as wings ; respira-
tion complete, by adherent lungs, which are
pierced through ; feathers on the skin.

XIV. Mammals.

Viviparous, and possessing mammae ; four
jointed limbs, or two only ; respiration com-
plete, by lungs not pierced through ; hair on
some part of the body.

The above is a table of the fourteen classes of known animals arranged
in the order most in conformity with that of nature. The arrangement
of these classes is such that we shall always be obliged to adhere to it
even though we may refuse to adopt the lines of demarcation between
them ; because this arrangement is based on a study of the organisa-
tion of the living bodies concerned, and because this highly important
study reveals affinities among the objects comprised in each division,
and determines the rank of each division throughout the series.

For these reasons no solid grounds can ever be found for changing
the general features of this classification, though changes may be
made as to detail, particularly in the divisions that are subordinate
to the classes ; because the affinities between the objects compr'sed
in the sub-divisions are more difficult to determine and leave more to
arbitrary opinion.

Now in order to bring home more closely the conformity of this
arrangement of animals with the actual order of nature, I shall set
forth the general series of known animals divided into its main groups,
proceeding from the simplest to the most complex according to the
principles indicated above.

134 ZOOLOGICAL PHILOSOPHY

My object in the exposition is to enable the reader to recognise the
rank in the general series that is occupied by the animals which I have
often had occasion to cite in the course of the present work, and to
save him the trouble of having recourse to other works on zoology
for this purpose.

I shall, however, here give merely a list of genera and of the main
groups ; but this hst will suffice to show the extent of the general
series, the arrangement of it that is most in conformity with nature,
and the places necessarily occupied by classes and orders as well perhaps
as by families and genera. We must of course refer to the good works
on zoology that we possess for a study of the details of all the animals
named in this list, for that does not come within the scope of the
present work.

GENERAL CLASSIFICATION OF ANIMALS.
Forming a series in conformity with the actual order of nature.

INVERTEBRATE ANIMALS.

They have no vertebral column and consequently no skeleton ; those
which have fulcra for the movement of their parts have them under
the integument. They lack a spinal cord and exhibit great variety
in the complexity of their organisation.

FIRST STAGE OF ORGANISATION.

No nerves or gangUonic longitudinal cord ; no vessels for circulation ;
no organs of respiration ; no specialised internal organ but that for
digestion,

{Infusorians and Polyps.)

INFUSORIANS.

(Class I. of the Animal Kingdom.)

Amorphous animals, reproducing by fission ; with bodies gelatinous,
transparent, homogeneous, contractile, and microscopic ; no radiating
tentacles, or rotatory appendage ; internally no special organ, even for
digestion.

Observations.

Of all known animals the infusorians are the most imperfect, the
most simply organised and possessed of the fewest faculties ; they
certainly have not the faculty of feeling.

GENERAL CLASSIFICATION 135

Infinitely minute, gelatinous