BIOLOGY REESE LIBRARY

R
6

UNIVERSITY- OF CALIFORNIA.

APR 24 1893

189 .

j cces

No.*-*'

EXPERIMENTAL EVOLUTION

RICHARD CLAY AND SONS, LIMITED,
LONDON AND BUNGAY

PREFACE

THE following pages contain a record of lectures which
I delivered in August, 1891, in Edinburgh, before the
very cultivated and attentive audiences afforded by the
Summer School of Art and Science which Professor
Patrick Geddes is evolving with great expense of
energy and devotion to science, aided by some
personal friends whose interest he has well awakened
in the organisation and diffusion of knowledge. I
wish to be reckoned among these ; and I took part
with much pleasure in the proceedings, while on
a visit to Edinburgh, Oxford, Cambridge, and
London, where the French Government had com-
missioned me to investigate the University Extension
Movement.

These lectures do not cover the whole ground

o

of the subject : I have purposely given most
attention to documents and facts of French origin,
as they are certainly less familiar to an English
audience, although the similar facts and documents
of English origin are, if anything, more familiar

vi PREFACE

to myself, and also much more extensive in some
lines. My desire has been more specially to show what
should be done, in future, on behalf of the Evolution
Theory, so that I may be excused if I have not gone
entirely through the facts of the past ; and as I consider
that experiment is now the only method of secur-
ing any further advance in solving the problems of
organic evolution, I have wished to state the matter
clearly, and to give some circulation to the statement
in the country where this line of study has most
followers.

And now I should ask of my readers to excuse such
literary or grammatical defects as they may meet with
in this volume. A foreigner can scarcely be expected
to master all the niceties of the English language.
However, my friends Prof. Patrick Geddes and J. A.
Thomson having been kind enough to look over the
proofs — and this I most sincerely thank them for —
I feel the most important inelegancies or errors have
been excluded, although English readers must doubt-
less perceive that the author is not writing in his
native language.

H. DE V.

MONTMORENCY (SEINE ET OISE), FRANCE,
October io//z, 1891.

CONTENTS

LECTURE I

The problem of the Living World — The three Hypotheses
concerning it — General Statement of the Evolution-
hypothesis — Gradual Growth of this Hypothesis, considered
especially in French Literature : Claude Duret (1605) ;
de Maillet (1749); Robinet (1766); Buffon (1761-6);
Lamarck (1809) ; Geoffrey St. Hilaire, etc. — Naudin (Rev^^e
Horticole, 1852) anticipates the Natural Selection Theory —
General Proofs of Evolution : Palaeontological, Embryo-
logical, Morphological — These Proofs not absolutely conclu-
sive— Direct Proof is wanted, and wanting — Nothing will
suffice but the Transformation of one Species into another :
Experimental Evolution necessary

LECTURE II

^^v

Experimental Evolution based on Three- Groups of Facts — First
Group : the Facts of Natural or Spontaneous Variation :
Organisms are not rigid structures, but exhibit much plasticity.
— Facts of Variation in Colour, correlated sometimes, and

viii CONTENTS

PAGE

perhaps always, with variation of chemical composition
(Armand Gautier's investigations) ; Variation in Dimensions
and Experiments on the real cause of this Variation, Semper
and the Author ; Variation in Integuments, Form, Shape of
Fruits and Leaves, Flowers — Penzig's Pflanzen- Teratologie —
Skeleton, Muscles, Internal Organs and Viscera ; Sexuality —
Neotenia 46

LECTURE III

The Facts of Natural or Spontaneous Variation (concluded) — Phy-
siological or Chemical Variation — Often exists where un-
suspected— May be noticed in all parts of the Body, even
between very closely-related Forms — Exists not only between
different Species, but between Varieties of same Species,
Individuals of same Variety, and even different ages of same
Individual — Chemical Variation explains Racial Immunity to
peculiar Diseases — This Chemical or Physiological Variation
in some cases of much higher import than any Morphological
Variation — Chauveau's Experiments on Bacilhis anthracis —
Physiological Differences between Brown and Green Frog
towards Poisons and Heat — Tarchanoff's Experiments —
Variation generally exists at all Ages, in all Groups of
Beings, at all Geological Epochs — Sudden Variation ... 114

LECTURE IV

Second Group of Facts supporting Experimental Evolution ; Facts
of Domestication of Animals ; their Departure from the
original Wild Type as seen in the cases where the latter still
exists ; Much more might be done in this way, and many

CONTENTS

PAGE

new Resources discovered ; Domestication has caused Animals
to vary in all parts of their Organism, from Weight of Brain
to Length of Digestive Tract. Third Group of Facts:
Cultivation of Plants ; its Influence ; the Departure from
the original Wild Type ; Variation in all parts of the Plants
from Roots to Flowers ; Numerous Varieties of the commonly-
cultivated Vegetables. Fourth Group of Facts : Influence of
Environment on Structure ; Closeness of Agreement between
Environment and Organism ; Beudant and Raulin's Experi-
ments ; the Author's Experiments ; Dareste and Teratogeny ;
Pouchet, Yung ; Facts and Experiments ; Pierre Lesage ;
Schmankevitsch ; Weismann's Criticisms 156

LECTURE V

Experimental Evolution based on the four preceding Groups of
Facts. These Facts illustrate at the same time its Methods,
which are : Change of Environment ; Use and Disuse ;
Natural Selection ; Sexual Selection ; and Physiological
Selection. These Factors of Evolution must all be subjected
to Experimental Test in order to show what they can Effect.
What is wanted : A Direct Proof, which all may Perceive and
Touch, of one Species (or Form) giving Birth to another
more or less Different, and Permanent. Numerous Accessory
Problems to be Investigated at the same time. Scientific
and Practical Import of this line of Investigation. Require-
ments : Farm and Laboratory ; Animals and Plants ; Time ;
Experiments must be able to last 20, 50, 100 Years or more.
This Experimental Investigation must and shall be performed.
But who is to begin ? . » 226

€

INDEX 261

EXPERIMENTAL EVOLUTION

EXPERIMENTAL EVOLUTION

LECTURE I

Summary — The Problem of the Living World — The three Hypotheses
concerning it — General Statement of the Evolution-hypothesis —
Gradual Growth of this Hypothesis, considered especially in French
Literature: Claude Duret (1605); de Maillet (1749); Robinet
(1766); Buffon (1761-6); Lamarck (1800); Geoffroy St. Hilaire,
etc. — Naudin (Revue Horticole, 1852) anticipates the Natural
Selection Theory — General Proofs of Evolution : Palaeontological,
Embryological, Morphological — These Proofs not absolutely con-
clusive— Direct Proof is wanted, and wanting — Nothing will suffice
but the Transformation of one Species into another : Experimental
Evolution necessary.

DURING countless ages, of which centuries are mere
moments, and whose number and length we can yet
by no known method pretend to appreciate, our
planet — an atom amidst an infinite world of similar
bodies — has been teeming with life. Innumerable
millions of plants and animals have lived and died,
on the earth, in the waters, in the air ; and if we can

B

EXPERIMENTAL EVOLUTION T/F.CT.

hardly estimate the number of the forms of life, it is
impossible to obtain any idea of the enormous —
although finite — number of the individuals. How
many plants were required to form a square foot
of coal ; and of how many Protozoa and sponges
is a cubic inch of chalk the only vestige ? Who
could dare to form an estimate of the number
of organisms which have disappeared and died with-
out leaving a single vestige, whose bodies, through
the slowly disintegrating processes of decomposition,
aerial or submarine, have abandoned their elements
to the atmosphere, the water, and the soil, — the
materials of life whence they have unceasingly re-
turned to new organisms in the course of that circulus
which, like life itself, knows neither rest nor immo-
bility ? The very elements which at the present
moment are parts of ourselves, of our bones, of our
flesh, of our blood, brain, or nerve, were part, not
very long ago, of our ancestors — further back still,
of prehistoric man ; and in a remote past, of that
inconceivable number of organisms of part of which
the sedimentary strata are the enormous burial-ground.
And when we come to consider that the circulation
of matter is unceasing and continuous between the
earth, the air, and the water on the one hand, and
all living organisms, animals, or plants, on the
other, we cannot help coming to the conclusion that

I THE PROBLEM OF THE LIVING WORLD 3

all present life is made up from the elements of
past life — that we are verily the flesh and blood of
the dead, recent or remote, and that the air we in-
hale, the water we drink, the food we eat, are for
the greater part made with elements derived from
these dead.

This notion is a very simple one, and certainly
familiar to all. And yet, its origin is not very
remote. Not to speak of our ugly brute of an
ancestor, that prehistoric man, who struggled hard
for dear life — and this we must thank him for — under
hard times and against many foes, without tools
without weapons, " sans everything " in fact, and who,
we may imagine, had but little spare time left for
philosophical meditations after he had provided the
food necessary to his companion and progeny, and
settled his little accounts with troublesome neigh-
bours, bipedal or quadrupedal, did this notion ever
cross the brain of the Gauls, Celts, or Britons of old ?
Did it even suggest itself to that old father of science,
to Aristotle, or to his commentators of mediaeval
times ? -Surely not, and in fact, no exact idea of
the circulation of matter could be obtained even a
century ago, when chemistry was yet only entering
upon life, and acquiring the dignity of a science.

The same is true of the greater part of our
modern ideas and science.

B 2

4 EXPERIMENTAL EVOLUTION LECT.

The philosopher of Geneva has said 1 that " the
condition of him who reflects is an anti-natural
condition, and that the man given to meditation
is a depraved animal." Some doubts may be
entertained concerning the second term of this
sentence, although the unhealthiness of meditation
is often obvitfus ; but it is certainly true that under
natural conditions, very little time is available for
meditative purposes. Even in our so-called civilized
life, how very small is the number of those who
do often really think and ponder on topics which
are neither food, nor dress, nor money. Most men
live, in fact, without troubling themselves with any
of the really great questions which force themselves
on the attention of the few who think, and they
leave those vexed questions of force, matter, move-
ment, space, life, consciousness, death, will, memory,
morality, right and wrong, to the physicist, bio-
logist, and moralist, with some disdain, pitying
them most thoroughly for devoting their time, life,
and energy to problems which apparently do not
admit of being solved.

The thinkers are however not of the same mind as
the multitude ; they entertain the opinion — absurd
in the eyes of many — that human science has yet a

1 J. J. Rousseau, Discours sur V Origin e et les Fondements de
rin'egalite parmi les Homines, 1754.

THE PROBLEM OF THE LIVING WORLD

long road to travel, that unexplored fields are yet
innumerable, and that no problem can be considered
insoluble so long as it has not been subjected to a
thorough investigation by means of all available
methods. If we consider that the number of these
methods increases each day, if we remember that
discoveries which seem quite insignificant are often
pregnant with the most important deductions — from
Galvani to the telegraph and the telephone one
small century only has elapsed — we may fairly con-
clude that a problem which hardly admits to-day of
any investigation may suddenly be solved to-morrow.
I may be allowed to quote an instance among many.
Some forty years ago a young man spent a long time
in the seemingly very speculative and idle study of
dissymmetry and symmetry in various crystals. The
practical value of such investigation seemed to be
nought, and at all events it had no interest save for
the elucidation of some points in crystallography.
But this investigation led logically to a study of
fermentation, and the final outcome of Pasteur's
earliest work has been — leaving out the step-
ping stones — the discovery of the real cause of
a large number of diseases, the cure of one of
them, and the expectation, based on facts, that
all of these diseases can be defeated by appropriate
methods. Little causes have great effects, and no

EXPERIMENTAL EVOLUTION LECT.

ascertained fact is useless ; this must be kept in
mind.

To return to our question, we may conclude that
no problem is out of man's reach : there is none he
may not grapple with, more or less successfully.

But this notion, also, is a very modern one, and
while the many at present certainly disagree with it,
we do not require to go centuries back to find the
thinkers themselves of a different opinion on the
matter, and sharing the creed of the mass.

This explains how it is that man has so long
delayed to investigate the problem of the present
day, which is the problem of the world. He con-
sidered the problem as admitting of no possible
investigation, and accepting the Scriptures as a
scientific text-book as well as a book • of morals, he
even perceived no problem at all, and lived in quiet-
ness and repose. But some were at work, observ-
ing, comparing, and noting facts. Their names are
familiar to all, and the outcome of their diverse work
and tendencies broke upon the world in 1859. For
Darwin, while seemingly inquiring only about the
origin of cats and dogs, and pigeons, and their pro-
bable relationship with antecedent similar animals,
had opened new prospects. This was immediately
understood ; and behind the cats, clogs, pigeons,
swine, and cattle, all beheld a new system of the

THREE HYPOTHESES

world, quite different from that of the currently
accepted creed.

The general system we shall leave out in the course
of these lectures ; that which concerns us here is
its application to the organic kingdom.

How did animals and plants come to life, and how
are we to explain the present state of nature ?

As Professor Huxley clearly states in his American
Addresses, there are only three hypotheses concerning
this matter.

The one is that the present state of things has
always existed, -and, I presume, never began. This
is one of the propositions which Herbert Spencer
terms unthinkable. There must have been a begin-
ning, because we know there is an end of all things ;
but in fact, it would be perfectly Quixotic to argue
against this windmill, as no one works it. I am not
aware that any scientists maintain this position.

The second hypothesis is that the present world
of animals and plants began suddenly in some past
epoch, in the course of the days or periods of crea-
tion : this is the theory of the book of Genesis,
of Milton's Paradise Lost, the orthodox theory of
the greater part ©f the civilized millions.

This hypothesis is a more rational one, and no
objection could be raised against it, in my opinion, if
the facts we are acquainted with were not in direct

8 EXPERIMENTAL EVOLUTION LECT.

contradiction with it. As to the feasibility of a
creation after this mode, we can entertain no doubt.
Miraculous and incomprehensible is this theory : but
all theories which pretend to explain the beginnings
are so ; they cannot avoid recurring to the hypothesis,
either of the spontaneous generation of matter, energy,
and life — of the whole intricate and complex system
of things, or of the creation of all this by some
mighty being, the watchmaker of Paley's well-known
argument. But who made the watchmaker ? it
is naturally asked. To the last question neither you
nor I are prepared to answer, and as none can answer
it, many come to the conclusion that the question is
absurd and must be dismissed as untenable. We
must confess that this question is above our reason.
But what of the first alternative ? Can any one of us
show matter, life, or energy spontaneously generated
out of nothing ? No ! and all the progress of physics
and chemistry goes to show how numerous are the
transformations of energy and matter, and to confirm
steadily the axiom ex niJiilo nihil. If we are asked
to believe in spontaneous creation of life, matter, or
energy, we merely answer that this belief goes against
our reason, because we are asked to believe in things
which are contrary to all our experience.1 And

1 This does not prevent Basile Conta, in his interesting Origine dcs
Espcccs (Paris, Alcan, 1888), from supposing that spontaneous genera-

SPECIAL CREATION THEORY

between two creeds, the one above, the other against
our reason, we prefer the first, willingly admitting that
our present intelligence is not able to understand most
of the phenomena we are acquainted with — though we
sincerely expect it to become so in the course of
ages — and that any adequate idea of the origin of
the world is a thing much above the grasping powers
of our intellect. Suppose some savages discovering one
morning on a sea-beach a watch stranded from some
shipwreck. No doubt, they all will come and cluster
eagerly around it, and if the unfortunate machine be
water-proof, they will listen to the ticking with great
wonder, and will furthermore believe that this watch is
some new and curious sort of animal which takes
more pleasure in ticking than in anything else. If
those savages are not mere brutes I presume some old
wise man will express his astonishment, and im-
mediately advise his slaves and followers to go and
give fruit and hogs to the priests, because this is an
extraordinary event which has some extraordinary
origin. And if you were to tell him that this watch had
been made by the rushing together of fragments of
stone and sand, he would not believe it. At least, I

tion has taken place, and is even taking place daily. He supposes that
the inferior organisms are of very recent, contemporary origin, while
the superior are derived from similar inferior organisms which have
sprung into life in periods which are remote in proportion to the
degree of perfection reached by the higher species.

io EXPERIMENTAL EVOLUTION LECT.

hope not. We are such savages. The more we study
nature in its broadest sense, the more its wheels seem
intricate, and its movements complex. Of course we
do not understand how it was made so, we do not
understand the watchmaker, nor even his design and
purpose in making the watch, but we perceive the
watch, we understand part of its movements, and so
are compelled to believe in the existence of the'
watchmaker, although we can form no definite idea
concerning him.

But the fact of believing in the watchmaker's exist-
ence, which is forced upon us by the fact that we
never have seen a single watch ; come spontaneously
into existence, and that our experience shows that no
single element — wheel, axis, or spring — has ever spon-
taneously appeared, does not necessarily compel us
to accept the second, above-named, of the three
hypotheses which Prof. Huxley recognizes. We
may very well accept the watchmaker's existence
without being obliged to believe that he made the
watch in the particular method described in the
Scriptures, and assumed by the adherents of the
Special Creation Theory. And we cannot — so long
as neither energy nor matter can be shown to arise
spontaneously out of nothingness — we cannot, upon
any theory, dispense writh the existence of a Creator.

The third hypothesis is the hypothesis of Evolution.

i EVOLUTION THEORY u

I cannot do better than quote Prof. Huxley's own
words. It "supposes that at any comparatively late
period of past time, our imaginary spectator [supposed
to be a witness of the history of the earth] would
meet with a state of things very similar to that which
now obtains, but that the likeness of the past to the
present would gradually become less and less, in pro-
portion to the remoteness of his period of observation
from the present day ; that the existing distribution
of mountains and plains, of rivers and seas, would
show itself to be the product of a slow process of
natural change operating upon more and more widely
different antecedent conditions of the mineral frame-
work of the earth ; until at length, in place of that
framework he would behold only a vast nebulous
mass, representing the constituents of the sun and of
the planetary bodies. Preceding the forms of life
which now exist, our observer would see animals and
plants, not identical with them, but like them ; in-
creasing their difference with their antiquity, and at
the same time, becoming simpler and simpler, until
finally the world of life would present nothing but
that undifferentiated protoplasmic matter which, so
far as our present knowledge goes, is the common
foundation of all vital activity." l

To put it briefly : the evolutionary hypothesis sup-

1 American Addresses. Three Lectures on Evolution, p. 10.

12 EXPERIMENTAL EVOLUTION LECT.

poses that from matter and force, the entire world and
the life it contains — their past, present, and future —
have been, are, and will be evolved by a natural
process, without any special interference of the
Creator, whose existence seems to me necessarily
assumed.

To quote again Professor Huxley : l " The hypo-
thesis of evolution supposes that in all this vast
progression there would be no breach of continuity-
no point at which we could say, 'This is a natural
process/ and ' This is not a natural process,' but that
the whole might be compared to that wonderful
process of development which may be seen going on
every day under our eyes, in virtue of which there
arises, out of the semi-fluid, comparatively homo-
geneous substance which we call an egg, the com-
plicated organization of one of the higher animals."

Excluding the first hypothesis, which explains
nothing, and merely ignores the problem to be
solved, the whole discussion is between the second
and third. And we cannot wonder at the rivalry
displayed on both sides — we cannot wonder at the
passionate fighting which has been carried on at
each discussion of the matter, when we consider that
in fact the question is not merely zoological, but
metaphysical and speculative, and that the real

1 American Addresses. Three Lectures on Evolution, pp. 10, n.

EVOLUTION THEORY 13

matter under discussion is not the origin of species,
but the origin of the world and of all it contains, man
himself included.

It would require much time to convey a correct
idea of the gradual evolution of the Evolution theory
itself. It did not spring out of the brain of one man,
fully equipped and ready, as Minerva is said to have
come to life. On the contrary, it developed slowly,
cautiously, very timidly, we may say. And this for
good reasons, prominent among which was the un-
animous assault its defenders had to receive each time
they tried to say a word in its favour. No doubt these
fights and defeats were unpleasant, but they turned
to the advantage of the vanquished, and each defeat
became a tonic to him, by which his forces were
invigorated and freshened. The idea of evolution,
and more specially of organic evolution, is, however,
of recent origin. At first it was a very vague and
unscientific notion. Although I have no intention of
giving an historical account of the evolution of the
Evolution theory, I may be allowed to give some
instances, to show some stepping-stones. Similar
instances are certainly to be found in English
and German literature, but I shall be content with
quoting here some facts belonging to French litera-
ture, as they may be less familiar to most English
readers.

14 EXPERIMENTAL EVOLUTION LECT.

In 1609 Mons. Claude Duret, President of the
Bench in the town of Moulins, in central France,
published a quaint book with still quainter illus-
trations. This Histoire admirable des Plantes . . -1
contains evolutionary notions of a very queer sort.
He fully believes that many aquatic birds, as well as
many sorts of insects, are generated from the rotten
wood of trees. In Scotland it seems — perhaps some
of you have heard of the fact and are ready to vouch
for it — in Scotland there is one sort of tree more
peculiar than others ; the leaves which fall on the
ground yield birds, while those which fall into water
are soon changed into fishes. There is no doubting
the fact, as the scene is very distinctly depicted
in an old wood-engraving. A photograph, how-
ever, would be more convincing, but then Daguerre
and Niepce had not made their appearance at that
time.

It may be remarked that some seventy years later
Father Kircher, in his Mundus Subterraneus? still
believed in many strange notions of the same sort, and
depicted the genesis of birds, apes, and men by means
of the transformation of some orchids. He had been

1 The full title is : Histoire admirable des Piantcs et Herbes esmer-
veillables et miractileuscs en Nature, mesmes d'aticunes qui s.ont vrays
Zoophytes on Plantes Animalcs .... avec I cur Portraits att natwel.
1 8°. Paris, Nicolas Brion, 1609.

2 Amsterdam, 2. vols. in folio, 1678.

DE MA1LLET 15

struck with the resemblance of these strange flowers
to many animals, and therefore concluded that the
latter were derived from the former.

In the meantime De Maillet, French consul in
Leghorn and in Egypt during a number of years,
wrote, at the end of his life, a strange book called
Telliamed^ (his own name reversed). The greater
part of it has little to do with the matter under dis-
cussion, but in the last ninety pages, after having
considered the real nature of fossils — a question at
that time much discussed, and concerning which the
truth became established only after numerous diffi-
culties— De Maillet concerns himself with the origin
of man and animals. His main idea is that all
terrestrial and aerial animals have their origin in some
corresponding marine form. For instance, birds are
derived from flying fishes, lions from sea-lions, &c.,
and man from the " homme marin" the husband of the
mermaid. The reason he gives for these derivations
is curious enough. Considering the many islands —
there were more of them in his time than at the
present day — which, although uninhabited by man,
contain animals and plants, he argues that if these
animals and plants are not derived from marin

1 Telliamed ; ou, Entretiens (fun Philosophe Indien avec un Missio-
naire Francais, etc. , mis en ordre sur les Mtmoires de fen M. de Maillet.
Basle, 1749.

16 EXPERIMENTAL EVOLUTION LECT.

forms, "we must assume a new creation, which is
absurd" (p. 313).

Some years after De Maillet, another French writer
gave utterance to more valuable notions concerning
evolution. This author was J. B. Robinet. There is but
little to interest us in his book, De la Nature, published
in 1 766 (four Svo volumes, Amsterdam,) but his Vues
philosophiques de la gradation naturelle des Formes de
FEtre, ou les Essais de la Nature qui apprend a faire
r Homme (1768, Amsterdam,) contain curious passages.
For instance, he clearly recognized the fact that all
animals are in many points similar, and that if the
similarity between any two animals at the opposed
ends of the organic scale is difficult to perceive when
they aie considered apart from the others, numerous
transitional forms occur, and are real connecting links
when the whole scale is taken into consideration.

Robinet supposes that Nature has an aim, a con-
stant tendency towards perfection, and towards perfec-
tion of a given type. Since the beginning the aim of
Nature has been to prepare man, and the proofs
thereof are not wanting, according to Robinet. These
proofs are the numerous stones or fossils which bear a
more or less vague resemblance to the organs and
various parts of man, monstrous turnips and extra-
ordinary cabbages, in the form of a hand, a nose, or
an ear, or other parts of the body, whether internal or

I ROBINET AND BUFFON 17

external. Robinet is not very clear about the method
which Nature followed in order to attain her object,
but the last part of his story is quite fluent, and the
ape appears as the last effort of Nature before she
succeeded in making man.

This is very crude and elementary evolutionism, to
be sure, and the names of Robinet, De Maillet, and
Duret l have but slight historical interest, but it must
be remembered that between Robinet and Darwin not
a century elapsed, and there lies the reason for which
I have wished to recall briefly the quaint notions of
these transformists of the past A word, however,
may be said in their defence ; we must remember
that at the time they wrote, little was known concern-
ing species, and no idea could be obtained concerning
their origin and derivation, so long as their nature was
ignored.

Evolutionism, scientific and really deserving this
name, appeared only a few years after the publication
of Robinet's ungainly views, and here the French
scientists took a prominent part.

Buffon comes first. Much has been said and
written concerning the orthodoxy of the great natural-
ist, and contradictory statements have been made, so

1 For details concerning their theories cf. Henry de Varigny : La
Philosophic Biologique aux xvii1' el xmiie Siccles, l\.evt(e Scientijiyuc,
August 29th, 1889. Also De Quatrefages, Charles Darwin et ses Pre-
curseurs francaiS) 1870, of which anew edition is in the press (1892).

C

J8 EXPERIMENTAL EVOLUTION LECT.

that many know not whether he is to be accounted
as a friend or as a foe. The truth is that Buffon's
views on the unity of species lacked unity themselves.
From 1753 to 1756, it is quite clear, as Geoffroy Saint
Hilaire has shown, that he believed in their immut-
ability. "Species in animals," he says, "are all
separated from each other by an interval which Nature
cannot cross." Later on, his writings show a different
turn of mind, and from 1761 to 1766, more particularly
give evidence thereof. " One is surprised at the prompt-
ness with which the species vary, and at the ease with
which they become altered and assume new forms."

This theory of the mutability of species he con-
sidered, some years later, to be rather exaggerated,
and he returned to more moderate views, though not
abandoning the theory of variability and mutability,
which, in his opinion, are due to the direct influence
of environment.

After Buffon comes Lamarck, a friend and pupil of
the former. Lamarck was the first to state distinctly,
in any developed form, the theory of the variability
and transmutation of species, which many had before
him briefly proposed or supposed, and he tried to dis-
cover the cause of this variability.1 The facts of varia-

1 See his Philosophic ZoologicjJie, 1809 ; Introduction a FHistoire
naturelle des Animaux sans Verlebres, 1815 ; and Systeme de Con-
naissances positives ', 1820.

I LAMARCKIAN THEORY 19

bility were supplied to him by all sorts of animals, and
in part by the domesticated forms, and among these
the pigeon and fowl, of which, later, Darwin made
great use. Lamarck believed in spontaneous genera-
tion— under laws given by a Creator — of elemen-
tary organisms which became gradually perfected and
transformed into higher beings, under other laws which
Lamarck recognized and stated. Among these laws is
that of the hereditary transmission of acquired char-
acters, which is at present so much discussed, after
Weismann's opposition. As to the cause of variability,
it is to be found, says Lamarck, in " new needs of the
organism," so that the influence of environment plays
but an accessory part. Whatever opinions may be
entertained as to the views of this naturalist concern-
ing the causes and methods of variation, it must be
conceded that he was the first clearly to perceive and
state the problem of the origin of species.

Geoffrey Saint Hilaire (Etienne) was rather a
disciple of BufFon than of Lamarck. He believed
much in the influence of environment1 and fought
hard against Cuvier and his views, while Bory de
Saint Vincent upheld the views of Lamarck. Of
Geoffroy Saint Hilaire we shall have to speak again
further on. We do not pretend to give here any com-

1 See his Sttr le Degre if Influence du Monde ambiant po^lr modifier
es Formes animates.

C 2

EXPERIMENTAL EVOLUTION LECT.

plete account of the progress of the Evolution theory-
more especially after having announced our desire to
restrict ourselves chiefly to French naturalists — and
shall dwell no longer on this point of history. It
must be recalled, however, that Linnaeus, in 1762
(Amcenitates] had expressed the idea that all species
of the same genus ab initio unam constituerunt speciem,
without saying, however, how the differentiation of
he primitive one species into many had taken place.
Moreover many writers whose names are given by
Darwin in his Origin of Species, anticipated him more
or less, not in his explanation of the quomodo of trans-
mutation, but in the statement of the fact, or theory.

There is, however, one name to which attention
must be called ; it is that of Naudin, the veteran French
botanist, who, in 1852, published a very interesting
paper in the Revue Horticole (1852, p. 102). As he
recently wrote to me x this paper was published
by the editors of the Revue with much diffidence ;
they cared little about theoretical discussions, and the
hypothesis of transmutation was " nowhere " in their
opinion. Some passages are of much interest, and
may be quoted here.

1 " The editors of the Revue Horticole did not feel inclined to
allow such heretical notions to be expounded in it ; they accepted the
paper, however, throwing the whole responsibility upon myself, and
fearing to injure their orthodoxy through an irhpure alloy." — (Letter,
dated March 6th, 1891.)

I NAUDIN (1852) 21

" We do not think that Nature has made her species
in a different fashion from that in which we proceed
ourselves in order to make our variations. To say the
truth, we have practised her very method. When we
wish, out of some zoological or botanical species, to
obtain a variety which answers to such or such of our
needs, we select (choisissons) out of the large number of
the individuals of this species, so as to make them the
starting point of a new stirp, those which seem already
to depart from the specific type in the direction which
suits us, and, by a rational and continuous sorting of
the descendants, after an undetermined number of
generations we create types or artificial species, which
correspond more or less with the ideal type we had
imagined, and which transmit the acquired characters
to their descendants in proportion to the number of
generations upon which our efforts have been bearing.
Such is, in our opinion, the method followed by Nature;
as well as by ourselves ; she has wished to create races
conformable to her needs, and, with a comparatively
small number of primitive types, she has successively,
and at different periods, given birth to all the animal
and vegetable species which people the earth." . . .

This says nothing of the reason for which Nature
follows such a method, but the method is exactly that
which we know under the name of natural selection and
artificial selection. It seems fair to say that Naudin's

22 EXPERIMENTAL EVOLUTION LECT.

name deserves a high place in the history of the rise
and progress of evolutionary thought, and the paper to
which I allude is not generally well known, even to
writers familiar with the subject of evolution. Of
Darwin's work I shall say nothing : all are familiar
with the principles which lie at the root of his theory ;
but it would be unfair not to put Herbert Spencer's
name on the list, close to his.

And now we may briefly recapitulate the theories
which have been proposed on both sides to explain
the present condition of the organic world.

On the special creation side we meet with four
distinct views :

(1) Our planet, long uninhabited, has become
peopled with the types and forms it now contains, from
another planet in which these existed, and which has
fallen on ours.

This hypothesis might be discussed by savages
or by lunatics ; to me it seems useless to show
its failure, of which the least is that it merely
puts off the problem without any attempt towards
solving it.

(2) All species have been specially created from
the beginning of the world — a very elastic term, to be
sure — and have lived in part, or in whole, until the
present day, without any alteration.

This hypothesis is untrue, as it is known that most

I SPECIAL CREATION THEORIES 23

living species occur only very seldom in strata of some
antiquity, and that the present fauna, for instance, is
quite different from the various faunas which lived in
the different geological epochs.

(3) A large number of living beings specially
created at the beginning, having been killed by various
cataclysms, they have been created anew after
the catastrophes which, in Cuvier's opinion, are the
necessary concomitants of every geological epoch.
This is Cuvier's hypothesis of the " revolutions of
the earth." It may seem somewhat puerile to sup-
pose that the Creator has seen His own doing turn
against Him, and oblige Him to begin His work
anew, on repeated occasions.

(4) All species have been specially created from
the beginning, but while some die out gradually, other
new ones put in a sudden appearance, for reasons
hitherto unexplained.

This is only a part of an hypothesis, as it does not
explain why or how new species appear, which is
exactly the problem to be solved.

On the adverse, non-special creation side, we have
only one hypothesis, the evolutionary one, which sup-
poses all living species to have been evolved from
antecedent and different organisms — all organisms
having perhaps been evolved out of a single ele-
mentary one, born we know not how, but certainly

24 EXPERIMENTAL EVOLUTION LECT.

created, unless we can believe that matter, energy,
and life can originate spontaneously.

Between the Special Creation and the Evolution
theory the contest has been a fierce one, for reasons
already given ; but it may be said that at the present
moment the last-named has gathered around it the
greater army.

But it must be confessed, at the same time, that
no positive and direct proof of the truth of the evo-
lutionary theory has yet been given. It is true none
can be given either of the opposite theory. In the
very year, 1852, in which Naudin gave utterance
to his theory of the origin of species by means of
selection, Herbert Spencer published a short essay
on the Development Hypothesis, which has been re-
publishccl in his recent edition of Essays, as the first
of the whole series. In this essay he speaks of the
anti-evolutionists, who argue that " as in • all our
experience we know no such phenomenon as trans-
mutation of species, it is unphilosophical to assume
that transmutation of species ever takes place," and
forget that " as in all our experience we have never
known a species created, it is unphilosophical to
assume that any species, has ever been created."
We cannot exactly adhere to this reasoning. If
species have been created, they may have been so
before man could see them, while if species are

I ARGUMENTS FOR EVOLUTION 25

derived from each other by evolution, there is no
reason why the process should not be at all times
going on, and why man should not witness it. So,
on that point, creationists are entitled to ask of evo-
lutionists demonstrations which, conversely, the latter
cannot require from the former.

Without proceeding to discuss more amply the
matter so very well discussed by Herbert Spencer
in this essay, I wish to recall briefly to your memory
the general proofs of organic evolution as they are
known at present.

One of these proofs, or arguments, is that which
results from palaeontological studies. Broadly speak-
ing, an evolution in the animal and vegetable king-
doms is indicated by the fact that the older strata
of the earth contain organisms which are simpler than
those which are contained in the newer, or are living
at present. For instance, no Vertebrates are known
in the Silurian strata save some lowly-organized
fishes, and it is only in later deposits that the other
groups put in an appearance. Of course, much may
be said, even now, concerning the provisional con-
dition of our palaeontological knowledge. We know
but little of the contents of the geological strata, and
of the greater part of the globe we are totally igno-
rant. Future investigations and discoveries may con-
siderably alter the present situation ; and, on the

26 EXPERIMENTAL EVOLUTION LECT.

other hand, our geological notions may require im-
portant alterations as concerns synchronism and
heterochronism of the strata and of their contents.
It may happen that vestiges of animals which we
consider as very recent may be found in much older
strata ; it may also happen that some types have
been evolved in very limited portions of the globe
at different times and with different characters. It
may be granted that our geological conceptions re-
quire to be revised, and in many cases altered. But
however fragmentary and imperfect our present know-
ledge may be, it nevertheless yields important con-
clusions. Through palaeontology we perceive in some
cases the passage from one group of animals to
another, and while theory shows that birds are
probably in close relationship with reptiles, the
Jurassic strata yield ArcJiceopteryx lithographic^
which partakes of the character of both groups, and
in the more recent Tertiary deposits we meet with
many forms which have now disappeared, but are in
intimate connection with the existing species of many
orders, and seem positively to be the ancestors from
which the latter have been evolved with slight modifi-
cations. It is enough to recall the important investi-
gations of Gaudry, Leidy, Falconer, Cope, Marsh,
Boyd-Dawkins, and Lartet, who have traced, with the
utmost probability, the exact line of descent from

PALAEONTOLOGICAL ARGUMENTS 27

those fossil forms of older strata to those which live
at the present time.

Palaeontology shows in some cases the process of
evolution in much detail. I may refer to the researches
of Hilgendorf and Hyatt, at Steinheim in Wiirtem-
bcrg. They show that while the different species of
Planorbis, when considered in the most recent of
these strata, are very dissimilar, if the series is studied
from the lower to the upper ones, it is easily seen
that out of four initial forms, not very different from
each other, slightly different forms have in the course
of time originated, becoming, as we consider more
recent strata, always more diversified, always more
different from their ancestors, and from one another.
While the origin is the same, the results are quite
dissimilar, and if the older strata were wanting,
no possible link could be found between the very
dissimilar forms which co-exist in the more recent
deposits, no line of descent or of relationship could
be established. Investigations of less recent elate than
those of Hyatt have afforded identical results. In
his important work on the Foraminifera,1 Terquem has
shown the forms which are intermediate between types
which at first glance seem very dissimilar ; and Rupert
Jones more recently, in his " Remarks on the Fora-

1 Recherches sur les Foraminifcrcs du Lias du Dtpartement de la
Moselle. 1858-1866,

28 EXPERIMENTAL EVOLUTION LECT.

minifera, with especial reference to their Variability
of Form, illustrated by the Cristellarians " {Monthly
Microscopical Journal, 1 876), has worked out the same
matter, with the same general result.

Palaeontology, upon the whole, although yet very
fragmentary and incomplete, testifies to the truth of
evolution, showing an unmistakable line of descent
from ancient types of life to more recent types, and
from these more recent types to those which live now.
I do not mean to say that in the case of every animal
we are enabled to trace its ancestry with exactness
to the most remote times, but in many cases this
ancestry admits of being very satisfactorily traced,
and, with the future progress of geology and palae-
ontology, many gaps will be filled up, and many
connecting links discovered.

Among recent books — French books — well illus-
trating the preceding statements, I would recommend
those which M. Gaudry, professor of palaeontology in
the French Natural History Museum, and one of the
leading evolutionists in France, has published, under
the significant title of Les Enchainements du Monde
Animal dans les Temps Geologiques. These three
volumes are entirely devoted to the question of palae-
ontological descent, and are most ably written and
reasoned.

Another argument for evolution is derived from

I EMBRYOLOGICAL ARGUMENTS 29

the facts of embryology. Embryology is merely an
evolution, and to study the development of any given
organism is to study its evolution from a single ele-
mentary cell — the egg-cell — to the stage when this
has become capable of leading an independent or
semi-independent life, and has acquired a form and
complexity of structure which are truly marvellous.
In many cases this evolution lasts some weeks, some
months at the longest, and the organism thus evolved
merely needs to acquire larger dimensions by growth ;
but in many cases also there are breaks in the evo-
lution process, and when one point is attained the
process stops for some time, and is resumed later on.
Such is the case in most butterflies where the evolution
or development takes place in two or three periods,
the adult period being singularly short, and some-
times hardly exceeding a few hours, during which
reproduction is the only function accomplished, and,
in fact, the butterfly stage of life has no other object
than reproduction.

This process of evolution is a most marvellous one.
While the brain — the minute speck of brain— of an
ant may well cause the naturalist and thinker to
wonder, by reason of the varied and complex acts it
originates, the mere cell out of which a most complex
organism with innumerable functions develops in the
course of a few years, yielding a brain such as that

30 EXPERIMENTAL EVOLUTION LECT.

of a Pascal, a Lavoisier, a Newton, a Goethe, a Shake-
speare, a Pasteur, or a Darwin, becomes to the natur-
alist a subject of meditation still more extraordinary
and astounding. This form of evolution is to be seen
in all organisms, save in the simpler ones where no
process of reproduction is present except mere division,
and where the organism consists of mere cells — one or
more — without any specialized organs and functions.
There is a striking sameness in the development
of animals of the same group, however much they
may differ from each other when they attain the
adult form. Such is the case, for instance, with many
parasitic crustaceans. While the adult Sacculina, for
example, is a mere mass of suctorial appendages
converging towards an alimentary canal, and presents
not a single one of the external characters of any
adult crustacean, development shows the character-
istic form of the crustacean larva, and no doubt can be
felt as to the real nature, affinities, and systematic
position of the degenerate adult, however unlike the
general crustacean type it may be.

This individual evolution is named ontogeny, as all
know, and evolutionary naturalists consider it as repeat-
ing, under a condensed and abridged form, the evolution
of the species, or group, that is to say the pJiylogeny
or palaeontological evolution. And while the study of
the transitional phases in individual evolution shows

I EMBRYOLOGICAL ARGUMENTS 31

the real relation between forms sometimes very dis-
similar in adult age, it shows also the probable origin
of the group or species under consideration. Why
should a tadpole begin as a fish — having' gills and
the circulatory system belonging to fishes — although
destined to become something very different from a fish,
if there is not some intimate relationship between am-
phibians and fishes, if amphibians have not their origin
in fishes, if amphibians are not transformed fishes ?

And, if we turn towards man, who, according to the
evolutionary hypothesis, is no more than the last result
of the evolution of higher vertebrates, we meet with
facts identical in nature, but more surprising still.
Mammals must be considered as having been evolved
out of lower vertebrates, exactly as amphibians must
have been evolved out of fishes, and as all vertebrates
must, in different lines, have been evolved from fishes,
man's development or embryology should retain some
trace of this long and varied ancestry. And it does
retain such traces ; this is a very plain and precise fact.
Haeckel, in his History of Natural Creation, and in
his AntJiropogenie, has well summarized the facts bear-
ing on this question, and it is useless to go over the
details which are familiar to all. In the course of
the few months during which the primitive egg-cell be-
comes evolved into a new-born child, the human organ-
ism offers unmistakable evidence of its animal ancestry

32 EXPERIMENTAL EVOLUTION LECT..

down to the fishes themselves, as, for instance, in its
temporary branchial slits and arches, in the primitive
circulatory apparatus of the earlier stages of develop-
ment, in the various forms which the central nervous
system presents at various periods. The evolution of
the circulatory apparatus is wonderful. At the begin-
ning, during the first hour of evolution, the heart is a
mere tube or bulb, exactly similar to the heart of the
ascidians. Through some modifications, it then pre-
sents the typical aspect of the heart of mud fishes
or Dipnoi'. Later on, we meet with the condition
persistent in adult amphibians ; then follows a stage
which corresponds to that of reptiles, and finally
the heart corresponds to that of birds and mammals.
The same process is to be seen in the evolution of
the principal blood-vessels which are attached to the
central organ of circulation, and the same stages are
successively gone through. Classical as these facts
may be, they may be briefly recalled, as their
signification is of great weight. All fishes, it
is well known, have a number of gill-arches on
each side. In the amphioxus or lancelet, the
lowest of known fish-like forms, there are very
numerous slits, doubtfully homologous with those
of true fishes, which have seven, five, four, or three.
Their use is quite clear : the blood flows through the
arches and the fringes they support, and thus be-

I EMBRYOLOGICAL ARGUMENT 33

comes aerated. If we consider amphibians, we
notice that the gill-arches and corresponding blood-
vessels are retained in the tadpole, and do not wonder
at it, since the tadpole, during its early life, is a gill-
breather. But when we consider reptiles — a lizard
for instance — we meet with the same vessels. Why ?
No reptile, at any time of its life, is a gill-breather, and
the use of these vessels is not easy to understand. It
cannot be said that they are useful to circulation,
since the circulatory function is much more effective
in birds or mammals, where these vessels are pro-
foundly modified. And no explanation can be given
except that reptiles are derived from amphibians and
fishes, and have retained a large part of the anatomy
of their ancestors. A closer study of the amphibians
shows that this explanation is acceptable. When the
gills shrivel and disappear, while lung respiration be-
comes established, the vessels do not entirely dis-
appear : they remain and persist exactly as before :
the gill-arches minus gills are known as aortic arches.
The need of these aortic arches is gone ; a much better
circulation might be provided otherwise, but this would
require a miracle, and as none occurs, we readily under-
stand how it is that these arches persist ; they have
been useful and necessary, and their presence explains
itself. So, then, if these aortic arches are present in the
reptiles, we must interpret them as we have interpreted

D

34 EXPERIMENTAL EVOLUTION LECT.

those of the frog, as having been useful at some time,
when they were rendered efficient by the presence of
gill-arches and gills, the only difference being in this
last case, that they have been useful not some days or
weeks or months ago, not in the same individual at an
earlier stage of life, but in remote ancestors, and the
remote ancestors are the amphibians, and, further still,
the fishes. If any other intelligible explanation can
be given of the presence of these aortic arches in
reptiles, which never, at any stage of life, are gill-
breathers, we certainly shall listen to it with great at-
tention. But the argument does not stop here, and
things may be pushed further still. Useless as cir-
culatory organs, and useless as respiratory organs,
these aortic arches are not limited to adult amphibians
and reptiles ; we meet them in birds, in mammals, and
even in man himself. At an early stage of their de-
velopment the latter all have on the side of the neck
several gill-slits and aortic arches. Will some creationist
explain why these arches, most of which are destined to
disappear, put in this temporary appearance ? Evolu-
tionists explain it as we have briefly pointed out :
but creationists must explain in some way or other
the temporary presence of these arches of which the
larger part rapidly disappears, while the remainder goes
to build the principal blood-vessels which originate in
the heart.

I EMBRYOLOGICAL ARGUMENT 35

The development of the central nervous system
furnishes us with another important argument out of
many in favour of evolution. The brain of man, dur-
ing the development of the embryo, passes through a
series of stages of increasing complexity, and a careful
study shows that these stages, which are temporary in
the embryo, are permanent in the principal groups of
animals. One may easily detect in the evolution of
the human brain a stage corresponding to that of the
brain of fishes ; but while the fishes permanently re-
tain this brain-structure, an advance occurs in man,
and the brain acquires the characters of the reptilian
encephalon ; later on it progresses again, and acquires
bird characters, then mammalian characters, and
finally it acquires those characters which are peculiar
to mankind. Here again, ontogeny demonstrates phy-
logeny, and phylogeny, that is, derivation from the
lower vertebrate forms, must be admitted to be true,
unless some better explanation can be proposed.

Many other embryological facts do not admit of
any explanation, if the hypothesis of derivation and
descent is not admitted. For instance, on the special
creation theory, why have baleen whales been provided
with a full set of teeth' which remain rudimentary, and
soon disappear in the course of development, and
which are never used nor even could be useful ? Again,
why are there pelvic bones in the whale, and even

D 2

36 EXPERIMENTAL EVOLUTION LECT.

rudiments of the hind-limbs, when both are totally
useless ? Innumerable questions of the same sort
might be and have been asked ; but no satisfactory
answer has yet been given by any creationist.

We may consider as belonging remotely to embry-
ology, some pathological proofs of evolution of which
a passing word may be said. I refer to those many
cases, well known to the pathologist, of tumours, of
fistulae, and of various malformations in many parts
of the body, which are congenital, and are seen in the
child from the moment of his birth, and cannot be
ascribed to any disease or accident. Some of these
cases are most curious and interesting to the evolu-
tionist. A great number of them have been recently
collected in an important work published by Professor
Lannelongue and V. Menard, under the title of
Affections Congenitalesl In the first volume of this
work — the only one yet published — the authors deal
with the congenital malformations of the head and
neck, and, to those who are not familiar with the evolu-
tionary theory, it may seem astounding that such or
such malformation of the neck or ears is due to the
persistence of the fish or amphibian stage of develop-
ment of these parts. Such is the case, however, and

1 Affections Congenitales, vol. i. Tctc ct Con, Maladies des Bour-
geons de FEmbryon, des Arcs brancliiaux et de leurs Fentes, Paris :
Asselin et Houzeau. 1891.

I PATHOLOGICAL ARGUMENT 37

there is no going against the facts of pathology which
come to furnish an unexpected support to the theory
of evolution. Other pathological, or, at least, abnor-
mal, facts point in the same direction. Some years
ago Dr. L. Testut, of Bordeaux, wrote l a large work
on muscular anomalies in man. It is well known
that there are frequent variations in the muscular
system, muscles being sometimes differently attached,
sometimes absent, while in many cases unusual
muscles appear in the human organism. Have the
persons who offer these abnormal conditions been
specially created with these peculiarities ? There is
no reason for supposing that they originated by a
different method from that with which we are all
acquainted, and then what can the creationists say to
explain these facts ? The evolutionist appeals to
descent, and does not much wonder at the occasional
presence, in man, of muscles which exist permanently
and constantly in other mammals. As Dr. Testut
says, " When we consider the facts separately [the
facts of muscular variation], we find, in short, that
nearly all the muscular anomalies of man are normal
dispositions in organisms which are inferior to him in
the zoological scale." This means that no condition

1 Les Anomalies wuscntaires c/icz F Homme expliquecs par T Anatomic
comparte, by L. Testut, Professor in the Medical School of Bordeaux.
8vo, 850 pages, 1884. Paris : G. Masson.

3cS EXPERIMENTAL EVOLUTION LECT.

is exceptionally met with in man, which does not
represent the normal condition in apes or in other
animals, and this is a fact of great importance to the
evolutionist. But it sorely tries the feelings of the
creationist, who cannot explain the case, who cannot
give any satisfactory reason for the presence, in that
specially created creature, man, of muscles which
typically belong to some other mammal, ape, bear, or
hog, also specially created.

A third argument for evolution is offered by the
facts of morphology. Morphology shows the unity
of plan of quite different organs, as for instance, the
arm of man, the fore-paw of the lion, the wing of the
bat, the fin of the whale, and the wing of the bird ;
it shows that they arc all made up of the same ele-
ments which are more or less modified in each case
according to what is required from them. The same
may be said of the numerous homologous organs in
any large group : as for instance the mouth-parts of
insects, which, although very different in their anatomy
and also in their function, when considered in the dif-
ferent orders of insects, are easily seen to be identical
fundamentally, whether the mouth is used for biting,
for sucking, or for other purposes. Other organs in
the same group, and sometimes in very large sub-
divisions of the animal kingdom, admit of being
morphologically compared, and in many cases we

MORPHOLOGICAL ARGUMENT 39

find that organs which often subserve very different
functions have a common origin, and are identical in
despite of the modifications through which they have
been adapted to their peculiar uses.

Such are, briefly stated, the general proofs of
evolution, or at least the principal among them ; I
must be content with this short statement.

Are these proofs satisfactory, are they convincing,
and what do they demonstrate ?

To an impartial mind, they prove one thing to
begin with, and it is that if we accept the creation
theory, we must believe that creation has been going
on through the whole series of past ages, and that
every type of life has been specially created at some
time or other, being in most, if not all cases, very
similar to types which have lived before, and must
also have been specially created. We must believe
that the Creator while obeying a general tendency to
progress, has first created some types of life which He,
soon after, has diversified in various directions ; and
that some of these types were doubtless of inferior
order, since they have died out, while the types of new
creation, the new species or varieties, have taken their
place. But then, these new species also have proved
inferior, and again new types have been created, or,
again, without proving inferior, they have soon had new
companions more perfect. Upon the whole, innumer-

40 EXPERIMENTAL EVOLUTION LECT.

able creations must have taken place, from the Cam-
brian to the Quaternary period, during millions of
years, and it would seem as if the Creator has been
trying to evolve out of each given type the greatest
number of forms without altering the fundamental
structure of the type Also it would seem as if the
Creator evolved the higher types very slowly and
gradually, through small modifications in various parts,
by a sort of patching, an ever-mending and rearrang-
ing process, just as a man generally proceeds. Things
stand, therefore, exactly as they should stand if the
Creator had been unable to create immediately the
desired form or types ; if He had begun by inferior
forms which required much alteration to attain the
desired degree of efficiency. This inability to attain,
from the first, the desired result, is very striking ;
palaeontology amply illustrates it, and embryology
also ; and to many it may seem surprising, while
evolutionists, and believers in natural selection, do not
wonder at it.

Palaeontology and embryology therefore, while not
disproving the creation theory, render it rather un-
intelligible to our reason, while they display facts
which seem very intelligible upon evolutionary views.
But can palaeontology and embryology, and all the
other facts appealed to by evolutionists, disprove
special creation, and establish the evolution theory

I VALUE OF THESE ARGUMENTS 41

on a firm basis ? Can we consider the doctrine of
the transmutation of species as firmly established, as
demonstrated by fact in an unmistakable manner ?
Certainly not. Evolutionists are convinced of the
truth of their doctrine, they can point to a number of
facts which fit with it, but they cannot give the re-
quired demonstration. The situation of the creation-
ists is different. If they accept the view — and they
must do so — that every species and variety has been
specially created, they may say that things stand as
they ought to, if special creation has existed ; and as
none of them claim that special creation is going on
now we cannot ask of them to show us a creation of that
sort. On the other hand, evolutionists cannot claim
that evolution is a process of the past. They believe
in its present existence, not only in organic structure,
but in mental organization, and also in the inorganic
world, and they point to the facts of psychology,
zoology, and astronomy, as illustrating the pro-
cess of evolution. And creationists may rightly
demand of them to show precise and unmistakable
instances of transmutation.

Are evolutionists prepared to meet this difficulty,
this requirement ? They may answer that the astron-
omical facts are not under their control, and that an
enormous amount of time is required to yield a single
instance of evolution, so that all they can do is to

42 EXPERIMENTAL EVOLUTION LECT.

note the present condition of things, and let our de-
scendants do the same and draw their conclusions.
So far as psychology is concerned, they may answer
that proofs of individual evolution are to be seen every
day, and that mental evolution is a positive fact in
every individual man, and in the animal kingdom as
a whole. And as concerns zoology, they may reply
that innumerable facts point to descent and evolution.
But the creationists may object to this argument,
and say ; if species are really evolved from each
other — and the case of species is only a very small
point in the question — you must show us species aris-
ing, by evolution, from former species. In many
palaeontological cases we do not find the connecting
links of which you assume the existence — in fact, it
may be said with truth that their existence is not
always* required — and, especially, we have not yet
seen a new species originate from a preceding one.
Show us this, show us a positive case of transmuta-
tion through natural means, such as may and do
operate under natural conditions, show us a species
becoming a new one, hitherto unknown? and we
will believe in evolution. Such is the answer of
creationists.

It might be discussed whether this argument is not

1 This requirement is necessary to preclude all objection which might
be raised— with reason— from the possibility of normal dimorphism.

I A POSITIVE PROOF WANTED. 43

of the most: dangerous sort, more especially for
creationists, whether there are not serious inconveni-
ences in refusing1 to believe in that which cannot be

o

demonstrated by actual, precise, visible and tangible
fact. But this point had better be left out, and we
will accept the reply of the creationists as it stands.

They ask for a proof of transmutation : we must
secure that proof and meet their demand. How so ?
Through direct experiment, through experimental
transformism. The notion is not exactly a recent
one, but in the present debate it represents the only
line along which we may expect to discover the
positive facts which are necessary. As Buffon has
said, " Man will never be conscious enough of nature's
power, nor of his power on nature." And this state-
ment I believe to be positively true. The only thing
to be clone, at all events, is to subject the notion to
the only possible test of which it admits, and to begin
experiments.

I have just said that the notion is not of recent
origin. The fact is that we find it clearly expressed
in the Nova Atlantis, where Bacon advises experi-
mental investigations for the purpose of discover-
ing how the environment reacts on living organ-
isms and forms species. But the most authorized
defender of experimental transformism has surely
been Isidore Geoffroy Saint Hilaire, and many

44 EXPERIMENTAL EVOLUTION LECT.

passages concerning this matter might be quoted from
his Histoire naturelle generate des Regnes orga-
niques, and his Influence du Monde ambiant, etc. One
will be enough, " Since Nature," he says," left to
herself never allows us to witness considerable modifi-
cations in the conditions of life, it is clear that only
one way is open to us if we wish to perceive such
modifications and to examine their effects on the
organism ; we must oblige Nature to perform that
which she would not spontaneously accomplish."
(Hist. Nat. Gen. iii. p. 389.)

This is exactly what we require. While facts of
observation are sufficiently numerous to give us a fair
idea of the amount of natural variability and variation
—although much may yet be done to give an adequate
notion of the amount of this variability — we require
to extend our knowledge concerning the causes of vari-
ability (the natural causes, of course), and to discover
in what manner, and to what extent they do operate.
We are already acquainted with some of these causes,
and we know that by selection, crossings, modified en-
vironment, much has been done. But still more can be
done, and in experimental transformism lies the only
test which we can apply to the evolutionary theory. We
must use all the methods we are acquainted with, and
also those, yet unknown, which cannot fail to disclose
themselves when we begin a thorough investigation

I EXPERIMENTAL TEST NECESSARY 45

of the matter, and do our utmost to bring about the
transmutation of any species. We do not specially
desire to transform any one species into another
known at present ; we wish to transform it into a new
species. And this is necessary, if we do not wish to
remain open to an objection suggested by the facts of
dimorphism. Many species occur in two or more forms,
sometimes very different, and if we were merely to
transmute one species into another, it might be said
that we had mistaken the two forms of a dimorphic
species for two different species, and then our attempt
would be useless to a large extent.

Experimental transformism is what we need now,
and therein lies the only method we can use.

But it must be demonstrated that this test is avail-
able, and it remains to show what are the facts which
lie at its basis, and what are the methods to be used.

LECTURE II

Summary — Experimental Evolution based on Three Groups of Facts —
First Group : the Facts of Natural or Spontaneous Variation :
Organisms are not rigid structures, but exhibit much plasticity.
— Facts of Variation in Colour, correlated sometimes, and
perhaps always, with variation of chemical composition
(Armand Gautier's investigations) ; Variation in Dimensions and
Experiments on the real cause of this Variation, .Semper and the
Author ; Variation in Integuments, Form, Shape of Fruits and
Leaves, Flowers — Penzig's Pflanzcn-Ter dialogic — Skeleton,
Muscles, Internal Organs and Viscera ; Sexuality — Camerano's
Neotenia.

TJIUI.I groups of facts lie at the basis of experi-
mental transformism and display at the same time
its conditions and its methods. The first, and most
important, comprises the facts which illustrate varia-
bility in the state of nature, natural or spontaneous
variability. Spontaneous, we call it, but in fact we use
the word only because we are ignorant of the real and
positive causes of this variability. The second group
includes the facts of variation under domestication
and culture ; the third, the facts illustrating the direct
influence of environment as a factor of modification and
transformation. These three groups of facts require

LECT. ii BASIS OF EXPERIMENTAL EVOLUTION 47

to be briefly stated in order to show how experimental
transformism must be carried out. Of course it is of
much importance to prove that living organisms
display a marked tendency to vary, under natural con-
ditions, in most of their parts, in a more or less marked
degree. For this natural variability l is that which

1 Cornevin (Traitc de Zootechnie generate, 1891, p. 226) establishes
the following list of the modes of variation among domestic animals :

I. Morphological variations.

Variations through disappearance. Absence of horns, ears,

hair, pigment, etc.
Total. Dwarfing, discolour-
ation.

arrested ' Partial. Niatism, partial

development, j discolouration, reduction
in the number of limbs,
etc.

juxtaposition. Is seen in some hybrids
when the characters of
both progenitors coexist
side by side.

— fusion. Diminished number of

ribs, teeth, digits, verte-
brae, etc.

— transformation. Wool replaced -by hair;

scales replaced by fea-
thers, etc.

j Total. Giants, melanism,
; extreme hairiness.

- hypertrophy. Partial Drooping ears ;
very long horns, hairs
or feathers of unusual
length.

( Supplementary vertebrae
division or ribs, teeth, horns, digits,

repetition. /

48 EXPERIMENTAL EVOLUTION LECT.

has allowed natural selection to operate, and allows
us to expect to push things further in the way of
direct experiment.

I do not intend to recall here all the facts which
have been quoted by a large number of naturalists, up
to the present day. I shall merely call attention to
the most important of them, using again preferably,
as they may be less familiar to my hearers, those
which I have been able to collect from French
sources.

One of the variable characters in most living beings
is colour, — in most, not in all, for there is among the
human races a strong tendency to the preservation of
the race-colour, while among animals, and especially
plants, colour varies a great deal. And this is the
reason why Linnaeus wrote his ever-quoted nimium

II. Physiological variations.

Variations through diminished activity. Lateness of develop-
ment ; enfeeble -
ment of sexual ten-
dencies ; sluggish-
ness.

— earlier Precocity.

— exaggerated Increase in fertility,

etc.

— stronger Vigour ; immunity

from diseases, etc.

To this list, as I shall show later on, we must make an important
addition in Group II., and add what I propose to call physiological or
chemical variation, although it differs entirely from the sort of variation
included by Cornevin under the same name

COLOUR- VARIATION 49

ne crede color i. It may be noticed here that persons who
want their supposed good sayings to travel far and
long, should always say them in Latin ; if Linnaeus
had written the four words above in good sensible
English, or in clear French, his saying, which seems
to be a sort of divinely inspired axiom for many,
would never have met with the success it has obtained,
and it would have been better. Perhaps the fact that
these words are a quotation from Virgil (Eclogues, ii.
17) has something to do with the matter. Accepting
this dictum, many have considered colour as of no im-
portance in the organism, whereas in many cases it is
demonstrably of high import.1 And, as we shall see
further on, variations in colour cannot be considered
as mere freaks of nature, however abundant they may
be, for where colour varies, there is also a more or
less pronounced variation in other characters, and
more especially in some interior and less easily
appreciated characters of chemical nature. And no
one can dispute the import of chemical characters,
when one knows the influence of chemical media on
most organisms. So, while recognizing with Linnaeus
that colour is certainly in many cases a very variable
character, I would refrain from repeating after so many
others nimium ne crede colori. For colour is a specific

1 Concerning the uses of colour see especially A. R. Wallace's
Danvinism, which contains an excellent account of the matter.

E

So EXPERIMENTAL EVOLUTION LECT.

character, or at least it -must be one to most of the
present systematic naturalists (though I doubt if this
state of things is eternal), and as evolutionists, we
cannot allow this character to be lightly disposed of,
when it is precisely one of the most variable in some
cases.1 In some cases, I repeat, not in all. For
while some instances of colour variation may be
observed in the state of nature among animals or
plants, while some special variations are more especially
met with, such as albinism and melanochroism, it must
be noted that colour variations are especially frequent
among cultivated plants and domestic animals, and are
thus due to the results of changing environment. We
do not always perceive how far there may be a change
in environment, but colour variations show that it
exists in many cases where we do not readily detect it.
Among animals in their natural condition, colour
variations are of no very rare occurrence. It is known
that the common fox in the same country offers
marked variations in colour, which are illustrated by
the different names which have been conferred upon
the principal forms ; Vulpes alopex, melanogaster, and
crucigera. The beaver also offers important colour

1 Of course facts concerning colour variation are to be found in a
large amount of works. But I would recommend, concerning colour
variation in insects, two recent works. The one is Mr. S. H. Scudder's
magnificent work on the Butterflies of New England ; the other is the
Entomologist' s Record and Journal of Variation.

COLOUR-VARIATION

variations, and its fur is in some cases of much lighter
colour, in others, of deeper. Colour variations are of
no scarce occurrence among insects and fishes, and in
a recent number of the Entomologists Record and
Journal of Variation -1 an interesting coloured plate
may be seen, illustrating more vividly than whole
volumes of description, the colour variations which
Mr. J. A. Clark has met with among the British
species of SmerintJius.

Lacordaire records similar facts concerning the
Sphinx elpenor, Audouin has some concerning Pyralis
vitis, and Duges concerning Phasma. Among insects,
again, Hulst has noticed a large amount of variation.
From one and the same Arctia excelsa he has obtained
a number of eggs and larvae which have yielded adult
butterflies belonging to eight or nine different varieties
— or, to speak correctly, possessing eight or nine
different specific names (Arctia phalerata, pallida,
phyllina, flammea, decorata, nais, etc.). Of course this
merely shows that the makers of these species were
wrong in establishing species where mere varieties
exist — if even varieties may be spoken of in this case —
but does this not show also that variation may be
very important ? 2 The common cray-fish is a well-

1 Edited by J. W. Tutt, London. March i6th, 1891.

2 Cf. Hulst: Variation in the Arctias. American Naturalist, 1884,
P- J93-

E

52 EXPERIMENTAL EVOLUTION LECT.

known instance of colour variation, being generally
brown, but sometimes blue, and even red in its
living state. Leeches offer a large amount of colour-
variation ; most Helices do the same, and in fact, it
may be said that in all groups of animals varia-
tions are met with in the colour of their garment.
I refer here merely to occasional variations, for it is
well known that a large number of mammals, birds,
and other animals offer periodical or seasonal colour
variations, especially in northern climates, being
brown or grey during the summer, and becoming
white during the winter. Such seasonal variations
Wallace, in his recent and excellent book on
Darwinism, ascribes to natural selection and to pro-
tective necessities. Very numerous instances thereof
might be adduced ; and Godron in his DcFRspeceet des
Races dans les Rtres organises (1859, two volumes), gives
a list — which might be extended of course — of the
mammals and birds and other animals which show
this seasonal variation, and also a list of animals which
offer instances of albinism, melanism, and crythrism.
But I maybe allowed to refer to Wallace's Darwinism
for all seasonal colour variations, and for the investi-
gation of the use and origin of colour generally.
As the last named cases of colour variation, such as
albinism and melanism, cannot be interpreted in a
quite satisfactory manner, we had better leave them

COLOUR-VARIATION 53

out. That which most interests us, so far as colour
variation is concerned, is the evidence showing
that a change of environment causes a change in
coloration. Some instances may be adduced : for
instance, Gerard states in the Dictionnaire dHistoire
naturelle of D'Orbigny1 that when the small brown
honey bees from High Burgundy are transported into
Bresse — although not very distant — they soon become
larger and assume a yellow colour ; this happens
even in the second generation. The same author
gives some instances from the vegetable kingdom.
As he rightly remarks, the roots of beet, carrot,
radish, and other plants, are colourless in the wild
and natural state, and as soon as they are subjected to
the process of culture they become red, or yellow, etc.
and Vilmorin in his Notice sur V Amelioration de la
Carotte sauvage, originally published in the Transac-
tions of the Horticultural Society (1840), has noted the
same fact, the red and yellow colours, as well as a
peculiar violet hue which has not been permanent,
appearing only in cultivated carrots after some time
their appearance being at first irregular and transitory.
Moquin Tandon 2 records some instances of change
in colour which are due to the influence of environ-
mental change. For instance, he has seen gentians
which are blue in valleys become white in the

1 Article Espcce. 2 Elements de Ttmtologie vcgetale.

54 EXPERIMENTAL EVOLUTION LECT.

mountains. Similarly Oxytropis montana and Trifo-
lium pratense are white in the Alps and Pyrenees, and
Geranium batrachoides, which is commonly bluish,
becomes variegated, and turns generally white when
it grows in unpropitious soil. There are white
varieties of many plants, such as Latnium purpureum
and Erica vulgaris, while Verbascum lycJinis, and
Campanula Trachelium bear flowers which are blue,
violet, or white, according to circumstances.

Such instances might be given by hundreds, as is
well known. In some cases it would seem that the in-
fluence of environment is very plain, although difficult
to explain, for there are places where some natural
colours of plants or animals disappear soon, and are
replaced by lighter tints, or in many cases by white.
M. d'Apchier de Pruns records the fact as having been
noticed by himself on his own land, and it seems that
at Brassac les Mines, in central France, while oxen
become of lighter hue, and pheasants, pigeons, ducks,
&c., have more or less white feathers, plants with
variegated leaves soon become uniformly green.1 And
some horticulturists and amateurs have complained,
similarly, of their garden or grounds, saying that they
find it impossible to keep variegated plants — for
all return to the ordinary type. The causes of these
facts are difficult to ascertain, as the circumstances
1 Revue Horticole^ 1883, p. 316.

II COLOUR-VARIATION 55

which determine variegations are themselves not
known ; but the facts are numerous, well authenti-
cated, and must be taken into account. Climate
certainly has some influence on the colour of flowers,
and although we do not exactly know yet what we
mean when we speak of differences of climate, as
Naudin aptly remarks, and though climate includes a
large number of very different factors which are
combined in different proportions according to
localities, there are influences which may be ascribed
to it, /;/ toto. G. Bonnier and C. Flahault have per-
formed interesting experiments on this point. G.
Bonnier1 has compared flowers of the same species
and age, from different altitudes, in the Austrian Alps
and Carpathians, and the result has been that while
some plants, such as Rosa alpina and Erigeron alpinus,
have the same colour at different heights, others are
slightly different : such is the case with TJiymus
serpyllum and Geranium sylvaticum ; others are very
different, such as Myosotis sylvatica, Campanula ro-
tundifolia, Ranunculus sylvaticus, Galium cruciatum.
Of course the colour is not radically changed
a pink flower does not become yellow, but it
grows deeper and richer in plants of higher altitude.
Microscopical investigation shows that the pigment

1 De la Variation avec F Altitude des Matieres colorees dcs Fleurs chez
line menu Espcce vegelale. Bull Soc. Botanique, 1880, . 103.

56 EXPERIMENTAL EVOLUTION LECT.

granules are more numerous in the flowers from high
altitudes. C. Flahault's 1 experiments are more con-
clusive, and the conditions under which they have
been performed are more satisfactory. His experi-
ments have been made on plants grown in Upsala
and in Paris from seeds of same origin. One half of
the Parisian seed has been sown in Paris, and the
other in Upsala ; one half of .the Upsala seed has
been sown in Paris, and the other in Upsala. With
the two experiments the result has been the same, the
flowers have always been more vividly coloured in
Upsala than in Paris, and the same holds good when
flowers of plants spontaneously growing around Paris
and around Upsala are compared. In some cases,
however, there is but a very slight difference. M.
Flahault has had the exact colours represented in his
paper, and the comparison of the Upsala and Paris
flowers is thus shown to the reader as if he had the
flowers themselves.

Concerning colour variation in animals, I must be
content with calling attention to some principal facts.
One is, that while animals in their natural wild
state offer but very slight colour variations in the same
region, these variations become very numerous under

1 Nonvelles Observations sur les Modifications des Vegetanx suivant
les Conditions physiques du Milieii. Annales des Sci. Nat. (Bot.) t. ix.
1880, p. 159.

COLOUR- VARIATION 57

domestication. Of this, horses, oxen, cats, rabbits,
guinea-pigs, &c., are instances. And this may be
explained by natural selection, at least if colour
is always of positive use in some way or other to
animals, in escaping dangers which are of daily
occurrence in the wild state of life, but which dis-
appear under domestication. Under domestication
colour variations, to which a more or less marked
tendency may always exist, are of no inconvenience,
unless positively repelled by artificial selection, and
thus such variations are often present. On this point
I may refer to the works of Darwin and Wallace.

Another fact to be taken into account is that of
the influence of food on colour. Many bird-fanciers
think that by appropriate colour-feeding, as they call
it, they can help the production or intensification of
colours. For instance, they believe that canary birds
can be made to become of a bright yellow when fed
with egg, mustard seed, curcuma powder, saffron
water, and alcohol, in definite proportions ; they even
consider it useful to put yellow flowers around the
bird's cage. But exact experiments, scientifically
conducted, are yet wanting on this subject, as I
have but second-hand and rather untrustworthy in-
formation concerning the investigations conducted by
Dr. Sauermann, which are alluded to in the previous
sentence.

58 EXPERIMENTAL EVOLUTION LECT.

A third fact, which must be noticed here, is the posi-
tive influence of the colour of environment on that of
animals. Mr. E. B. Poulton has recently studied this
matter, showing, in his important memoir published
in 1887, that many lepidopterous larvae are strongly
affected by the surrounding colour. The plates
which accompany his memoir illustrate the fact
very precisely.

If we consider those freaks of colour which are
familiar to horticulturists under the name of variega-
tions, some interesting facts may be noticed. It has
been often questioned whether variegations are not
pathological symptoms, and whether variegated plants
are not more or less diseased. M. E. A. Carriere * has
carefully considered the matter, and his considerable
horticultural experience does not make him feel in-
clined to consider variegated plants as being diseased
at all. It even seems that in many cases, variegated
forms are healthier and stronger than the non-
variegated : for instance, the variegated Euouymus of
the Duke of Anjou variety. There is however one
fact which has been noticed concerning variegations —
it is the impossibility of maintaining such plants with
their variegation in some localities. Many horticul-
turists have recorded the fact ; and while some com-

1 Lcs Panachures sont dies des Maladies? Revue Horticole, 1884,
p. 198.

ii COLOUR-VARIATION 59

plain that all variegated plants, when grown on their
grounds, soon revert to the ordinary type, even when
they belong to the most stable varieties, others notice
that their garden seems very propitious to the produc-
tion of variegations. There is some unknown influence
at work in these cases, and experiments might show
what it is.

But it certainly seems that variegated plants cannot
be considered as diseased, and M. Lebas x says posi-
tively that Euonymus sulfurea, Euonyinus radicans
variegata, and Thujopsis dolabrata variegata are cer-
tainly stronger and hardier than the common non-
variegated varieties; and, on the other hand, MM.
Carriere and Andre2 notice that while Aspidistra
clatior variegata has a strong tendency, in most
places, to revert to the non-variegated type, there
are places where it remains quite constant, and where
even non-variegated forms become spontaneously
variegated. In some cases variegation comes on
slowly, and Vilmorin3 has studied the process with
care, but in others it comes on all of a sudden.
Carriere 4 has noticed a case of this sort in a garden
where thousands of celery plants were growing, and

1 De qtielqttes Fusains du Japan a Feuilles panachees. Rev.
Horticole, 1872, p. 139.

-' Revue Horticole, 1888, p. 124.

;i Stir les Panachures des Fleiirs. Ibid. 1852, p. 128.

4 Panachurc dn Ccleri. Rev. Horticole, 1882, p. 541.

60 EXPERIMENTAL EVOLUTION LECT.

where all, in a more or less marked degree, at the
same time became variegated. This fact, with others
which might be quoted, goes to show that variegations
depend on some environmental influence.

Colour variations may, however, be noticed in cases
where no environmental influence can, as yet, be
traced. Every one has seen cases where the same
rose-bush yields flowers of dissimilar colours. Carriere
and Andre,1 to take an instance among many, have
noticed a rose of the Mabel Morison variety carrying-
white flowers and one single pink one. The branch
bearing the pink flower has been grafted on another
bush, and it has maintained its special character,
yielding always pink roses. Such cases are not of
rare occurrence. But how can we understand the
cause of this variation ? Environmental influence
seems out of the question, and we are at a loss to
account for this important variation.

Similar colour variations are often noticed in fruits,
and have often been recorded in connection with
grapes. Carriere has quoted a case of this sort, and
given a good coloured plate showing well how things
stand. In the same bunch of grapes some are black
or red, some colourless, and many variegated in
different manners. It may seem that these cases are

3 C<zs dc Dichroisme dans la Floraison tfun Rosier. Rev. Horticole,
1888, p. 74.

II COLOUR-VARIATION 61

of slight importance, and that I am losing much time
in bringing them before you. Truly, if we were to
view the things in the light of Linnaeus — nimiinn
ne crede colori — such would be the case ; but recent
facts have gone to show that colour variation is not
merely what it seems to be, a variation in pigment
deposits ; there are more important variations which
underlie or accompany it, and these are of much
interest in showing that colour variation is of greater
import than might be thought at first glance. These
variations are of chemical order, and, so far as I know,
little has yet been done to investigate this delicate
matter beyond a short but excellent paper by Pro-
fessor Armand Gautier.1 The author begins by re-
calling some instances which have a remote relation
to this matter, and some of which are familiar to all.
It is known, for instance, that when a mare has once
given birth to a mule, it may happen that in after years
her foals, produced after the usual impregnation from
a stallion, present peculiarities which belong to asses.
It seems that the single fecundation by the ass has in
some manner impregnated the whole maternal organ-
ism upon which it has stamped itself. Similar cases
are to be observed in the human race as well as
among horses or dogs, and these show that a foreign

1 Du Mecanisinede la Variation des Etresvivants, dr-'<:., \\\Hommage
a Monsieur Chevreul a V Occasion de son Centenaire. F. A lean. 1886.

62 EXPERIMENTAL EVOLUTION LECT.

influence, which determines no variation at all in the
maternal organism, has, however, effected a deep
change on the germ-cells, and has operated on an
important part of the organism. Instances of the
same sort may be met with among plants. It
happens, for instance, that after a branch of a varie-
gated variety has been grafted on a non-variegated
plant, some variegated branches sprout from the
latter. And this shows, as M. Armand Gautier con-
tends, and as all naturalists must admit, that race-
variation, or, generally speaking, variation of any
sort, or of any importance, is not a mere external
fact — a mere external modification — but that the
modification makes itself felt in the utmost depths
and intimacy of the cells. Otherwise stated, there
is not only a mere difference of form ; underlying
the formal or external difference, there are modifi-
cations of much greater importance in the chemistry
or physiology of the cell-plasma. These differ-
ences may be localized instead of being general.
For instance, the same orange-tree may bear oranges
and lemons, if some flowers have been impreg-
nated with pollen from lemon-trees ; and it may
happen even that the variation is more localized
still when one half of the fruit is orange and the
other lemon — when, as Naudin has seen, one half is
Datura stramonium, the other D. lacvis. Of course,

CHEMICAL VARIATION 63

by reasoning we also come to the conclusion that
there must be physiological or chemical differences
accompanying the anatomical or morphological varia-
tions. ^ But Prof. Gautier has tried to appreciate
these differences, and to measure them in some
way. Notwithstanding the Linnaean axiom con-
cerning colour, and the fact that many consider
colour variation as of very little import because it is
so frequent, Gautier has studied with great care the
intimate changes which accompany colour variation.
The common grape has been selected by him as
his subject, all varieties of grape being varieties
of one common stock, however different they may be
in many respects ; and after a careful investigation of
the colouring matters, he has come to the conclusion
that, although they all belong to the same type, and
have all been considered as one and the same, they
offer important differences. For instance, while some
of the pigments are soluble in water, others are not ;
while some yield green precipitate with lead salts,
others yield a blue one ; while some contain nitrogen,
others do not. For instance, again, grapes of the
Carignan variety contain a colouring matter of the
type C21H20O10, and another which contains C22H24O10.
The Grenache variety contains a different matter,
C,3H22O10 ; Aramon contains C23H18O10 ; Teinturier
answers to C22H20O10, Petit-Bonschet to C^H^O^,

64 EXPERIMENTAL EVOLUTION LECT.

and Camay to C20H20O10. This shows that the slight
external differences which are peculiar to each sort or
variety, derived from the common stock by selection
and culture, arc accompanied by important chemical
variations. The above-mentioned differences illus-
trate the fact. It must be added, also, that other
differences are to be met with — differences in the
amount and nature of sugar, tannin, &c.

These results determined Prof. Gautier to investi-
s gate an important matter which is closely related
to the foregoing topics, and he has examined the
colouring-matter of hybrid forms. For instance,
Petit-BouscJiet is the result of the impregnation of
Teinturier by Aramon pollen ; and the question to be
solved is the following : Is Petit- Bouscket colouring-
matter identical with that of one of its parents, or
intermediate between both, or is it entirely different ?
Direct analysis shows that the second supposition
is true. Petit-Bonschet colouring-matter is nearly
exactly intermediate between those of its parents,
and its composition is the arithmetical mean between
those of the two stocks from which it is derived.
Another important fact which has been pointed out
by Gautier is that all colouring-matter which may
be found in grapes, when subjected to the influence
of potash, splits into two sorts of chemical com-
pounds ; two of them are constant, and invariably

CHEMICAL VARIABILITY 65

met with — phloroglucin and protocatechuic acid ; the
other is variable, and consists of potash united to
some fatty acid, so that while in all cases phloro-
glucin and protocatechuic acid are present, the third
element varies, and these variations are the cause
of the peculiarities which characterize each grape
colouring-matter ; or at least, if they are not the
cause, they are concomitant phenomena. Similar
facts have been ascertained by Prof. Gautier con-
cerning a chemical substance which is very abundant
in nature, and which would seem to be constant and
invariable. Chlorophyll, according to his investiga-
tions, is not identical among Acotyledons, Monoco-
tyledons, and Dicotyledons ; there are marked chemical
differences, marked variations in chemical constitu-
tion, and even between two species of two families
(Spinach and Mallow) there is a difference. Of
course these variations are not very intense, and the
different sorts of chlorophyll are always homologous,
but they are not identical. Similar instances are to
be met with among animals. While we commonly
speak of albumen, ossein, syntonin, and other com-
pounds of animal tissues, as being constant and
identical, direct analysis and investigation show that
all these substances, when considered among different
animals, do present common characters, which are
permanent and ubiquitous ; all possess also special

F

66 EXPERIMENTAL EVOLUTION LECT.

features which distinguish them from the similar
compounds. Albumen is not the same in all eggs,
for instance, in those of the hen, turkey, and duck ;
and the flesh of fishes is different from that of
mammals or birds. It even follows from Prof.
Gautier's experiments that there are differences in the
same animal at different times of life, and differences
according to the mode of life and nutrition. For
instance, if the meat of oxen, fed in the ordinary
manner upon hay and grass in the pasture, is com-
pared with that of oxen which have been fed and
rapidly fattened with the refuse of beet-sugar fac-
tories, as is often done in France and Germany, there
is not only a difference in the taste and flavour of the
steaks or roasts, there is also a chemical difference
which is easily detected. While the flesh of the
pasture-oxen rapidly dissolves in water and hydro-
chloric acid, that of the oxen fed on beet-refuse
dissolves very slowly and incompletely ; the greater
part does not become transformed into syntonin, and
in this respect it resembles the flesh of calves, veal
being very refractory to the action of dilute hydro-
chloric acid.

I may have been dwelling rather a long time on
M. Gautier's experiments, but they seem to me very
interesting and suggestive. Of course we do not yet
know anything about the cause of variation, but it is a

II CAUSES OF COLOUR-VARIATION 67

great deal to have some information concerning the
phenomena which accompany it, and especially the
chemical and biological phenomena, and it is import-
ant also to be able to detect such phenomena even in
cases where no external or morphological differences
are obvious. Later on, I shall have to revert to these
matters, and for the present it is sufficient to show
that even in cases where the external variations seem
so weak as to be generally considered of no real
account by naturalists, very marked chemical varia-
tions underlie the slight morphological differences.

Upon the whole, then, if a steady and careful
investigation were made of the chemical differences
which accompany colour variation, doubtless we should
see that the latter is of great importance.

Concerning the causes of colour variation very
little is known. Mr. A. R. Wallace has given a
detailed discussion of the matter in his recent book on
Darwinism, and emphasizes the protective value of
colours and their consequent relation to natural
selection. This factor has doubtless been of much
importance, but on the other hand, as Wallace indeed
admits, colour variations have much to do also with
the general constitution, and some relationship between
vigour, or weakness, and colour is commonly recog-
nized. In 1823, Heusinger already contended that the
quantity of colour in animals is subject to two laws :

F 2

68 EXPERIMENTAL EVOLUTION LECT.

the first of which is that colour is more abundant
when the genital functions are most active ; and the
second, that colour is also in relation with the fatty
layer underlying the skin, being less abundant when
this layer is thicker, and vice versa. Recent observa-
tions, and the general experience of breeders, go to
show that there is much truth in this view, as the
breeders have remarked that the best breeds for flesh
and fat — the Southdown for instance — have less colour
than the other breeds of the same origin ; and the same
obtains among cattle, and among domestic birds,
where the white, or faintly coloured individuals are
known to be less vigorous than the others. It is also
commonly observed that the cause which induces
albinism generally affects reproductive functions in a
marked manner, and that partial or total sterility is
induced : in fact one may say that the absence of
•pigment and the sterility are correlated expressions
of the same constitutional change. Such is the case,
for instance, with the Fredericksberg breed of horses.
These horses are very peculiar in their colour, which is
pure white, although they are not albinos. They are
sterile inter se, and in order to preserve the breed,
which is used by the royal family of Denmark, they
are mated with grey or black mares, and among the
progeny pure white horses are obtained. The sterility
between like and like is not complete, as in some cases

ii VIGOUR AND COLOUR 69

a progeny is obtained, but the latter is deficient and
lacks vitality.1 As a last proof of the relation between
vigour and colour, we may notice the fact that accord-
ing to many authors, among them Settegast, Heusinger,
and Wyman, animals deeply coloured, animals of
black coats for instance, are well able to withstand
the influence of poisonous plants, which kill others
less coloured. There thus seems to exist a positive
relationship between vigour and colour, and this
cannot be wondered at, since colour is the result of
chemical processes which are carried on in the organ-
ism, and since this metabolism certainly varies in in-
tensity and rapidity in different individuals. Other
agencies, which may operate on vigour, exert an
influence on colour ; light is such an agency, but facts
seem somewhat contradictory, and we cannot wonder
at this when we consider that while light varies, other
influences, such as heat, may not vary, or may vary
in a different direction. The climate is also operative
— although we can certainly not give a precise defini-
tion of this term — and an interesting case is that of a
herd of Dishleys living in the vicinity of the sea, in
France. These Dishleys were always spotted on the
face and ears, and had large black spots which rather
discouraged buyers. The owner said these spots were

1 Tissernnd : fitudes economiqiies sur le D<nte'>wfc, le Hohtein, ft It

Slesivig.

70 EXPERIMENTAL EVOLUTION LECT.

the result of the climate of the sea-shore, and in fact,
, the descendants of these spotted animals bred inland,
at Lyons for instance, were always pure white.1

So much, then, for colour variation. But animals
and plants vary in many other respects, and one of
the most familiar examples is that of dimensional
differences.

I am not aware that any naturalist has said —
-unless in current English or French, happily not
in a Latin aphorism — that dimensional differences
are of small importance ; but I presume many
think so. Variations of this sort are very frequent,
and although it is possible, by selection of extreme
variations, to create varieties of giant or of dwarfed
plants for instance, as any horticulturist may testify,
one might rightly consider this sort of variation as
more secondary than most others, if it could not be
shown that, while dimensions vary, other variations are
present at the same time, which may very well be of
high importance. These dimensional variations arc
in a large measure correlated with external influences.
Darwin has shown how, among horses, the dimensions
decrease in northern latitudes, in islands, and on moun-
tains. Man also is smaller in extreme northern climates,
and all the organisms of extreme northern parts
tend to be small. It may be, as Alcide d'Orbigny

1 Fact quoted by Cornevin : Traitt de Zootechnie, p. 278,

DIMENSIONAL VARIATIONS 71

believes ( Voyage dans ? Amerique meridionale, t. iv.),
that cold on one hand, and decrease of pressure on the
other, exert an unfavourable influence on growth.
But certainly food has a great deal to do with dimen-
sional variations. When food is abundant, and easy
to get, animals and man are prosperous and attain
large dimensions, while when it is scarce they remain
smaller. Japanese horticulturists rely in part on this
influence of the scarcity of food in their process for the
dwarfing of plants. Most persons have seen — or at
least heard of — these diminutive plants of theirs,
mostly conifers, such as Thuja > Juniperus, etc., which,
while aged 40, 60, 80, 100, or 150 years, are often
much less than a yard high, although their relative
proportions are well preserved, so that when you look
at them it is exactly as if you were looking at a normal
large tree through the wrong end of a glass. These
dwarfs are the result, in part, of mechanical processes
which prevent the spreading of branches, and in part,
of a starving process which consists in cutting most
roots, and in keeping the plant in poor soil.
Many of these Japanese dwarfs may be seen in
Europe, and they well illustrate the influence of
external conditions on growth and dimensions. Num-
erous instances show that plants or animals transferred
from unfavourable to favourable conditions, or vice
versa, acquire larger dimensions, or, on the contrary

72 EXPERIMENTAL EVOLUTION LECT.

become smaller. Such 'differences may be noticed
among all sorts of animals, from the highest to the
lowest. Gerard has noticed that bees transferred from
Burgundy to Bresse become larger in a generation ; A.
H. Curtiss has seen, in some places near the Potomac,
Bidens cernua acquire a height which is six times
the common average height of this plant, and he has
seen the same in Oxalis stricta ; C. Lemaire states in
D'Orbigny's Dictionary that, while cultivated hemp
grows no higher than a metre and a half in France, in
Piedmont it attains three and four metres ; and if
Italian stock is planted in France it rapidly reverts to
the small variety, in the course of two or three
years. Speaking of horses and of their dimensional
differences according to climate and environment, De
Quatrefages expresses himself as follows : " These
contrasts may be interpreted as due to the influence
which must be exerted on the first-named [Corsican
and Pyrenean stocks] by the stimulating and dry air
of the mountains, the frugal food with which they
must often be content, and, doubtless also, the hard
exercise which is rendered necessary by the roughness
of the soil. The others, on the contrary, [he refers to
the large heavy horses of the Bresse province,] always
immersed in a moist and heavy atmosphere, over-fed
with watery plants, and having none but easy work to
perform, must surely feel the effects of an environment

ii DIMENSIONAL VARIATIONS 73

whose influence exerts itself even on plants." That
such is the case, and that the influence of environ-
ment on dimensions is a very direct one, is amply
shown by the results of a change. Horses and oxen
become larger when transferred from Brittany to
Normandy, while the reverse happens in the reverse
case, for when some oxen were sent from Poitou to
Brittany, at the third generation the first named race
had acquired all the characters of the Breton stock.

Generally speaking, insular animals are smaller f
than their continental congeners. In the Canary
Islands the oxen of one of the smallest islands are
much smaller than those of the others, although all
belong to the same breed, and the horses are also
smaller, and the indigenous inhabitants are in the
same case, although, belonging to a tall race. It
would seem that in Malta elephants were very small
— fossil elephants of course — and that during the
Roman period the island was noted for a dwarf breed
of dogs, which was named after their birthplace, ac-
cording to Strabo. In Corsica also horses and oxen
are very small, and Cervus corsicanus> the indigenous
deer, is quite reduced in dimensions, although, accord-
ing to Polybius, this species was imported from
Europe 2,000 years ago, which makes it a descendant
of our Cervus elaphus ; and lastly the small dimensions
of the Falkland horses — imported from Spain in 1764

74 EXPERIMENTAL EVOLUTION LECT.

— are familiar to all. The dwarf rabbits of Porto
Santo described by Darwin may also be cited as a
case in point Dimensional variations in wild animals
are very numerous, and Locard (Etudes sur les Varia-
tions malacologiques a" apres la Faime vivante et fossile
de la partie centrale du Bassin du Rhone) notes among
a large number of similar cases, the fact that many
molluscs — land or water — common to France and
Algeria, are much larger in Africa, where their dimen-
sions are double those of their European con-
geners.1 Isidore Geoffrey Saint Hilaire says that
Lymncea stagnalis is* much larger in ponds than
in rivers. Moquin-Tandon notes that in the same'
country the same species of molluscs exhibits im-
portant dimensional variations, and he has seen
Bulimus decollatns nineteen times larger in Africa
than in Europe.

Through careful selection these dimensional varia-
tions may become permanent, especially if no change

1 Such is the case particularly with Helix aspersa, vermiciilata,
lactea, melanostoma, Leticochroa candidissima, Fhysa contorta, and
many others. And when Leucochroa, for instance, is transferred from
Algeria to France it does not acquire a length of more than one centi-
metre, while in its African home it is two or three centimetres long.
Cf. Locard : L 'Influence des Milieux sur le Developpement des Mol-
lusques. Societe d 'Agriculture ', Histoire Naturelle, et Arts Utiles de
Lyon, 1891. It has also been issued in pamphlet form by J. B.
Bailliere, Paris, 1892. A large amount of facts of French origin are
quoted in this valuable contribution to the subject, and the author is
one of the leading malacologists.

II DWARFING AND STERILITY 75

occurs in the environment/ M. A. Roujon, of
Clermont-Ferrand,1 by selecting the central, smaller
seeds of dwarfed plants of Helianthus annuus, Calen-
dula arvensis, and Zea rnais^ has been able to obtain
very small individuals of these three species. But the
most important fact, among those he has observed,
is that while the dimensions of the plants decrease,
their fertility is much impaired : the number of seeds
which are produced becomes smaller, and dwindles
down to 4, 3, 2, i, only, and finally no more seeds are-'
produced : a condition of absolute sterility is induced.
This concomitant sexual variation is of great import-
ance, of course, in showing that when dimensions vary
they are not alone variable ; there are other variations
which accompany the differences of dimensions.

One fact must be noticed concerning the point
which is now under consideration. It is the fact that
while we can easily, through a number of methods,!
induce unfavourable conditions, it is much more
difficult to induce favourable circumstances which,
lead to a better development. The advance of know-
ledge, however, may be expected to yield results
which shall prove more satisfactory, but we perceive
the difficulty of progress through the difficulty we
experience when we wish to maintain any natural or

1 De quelques Variations considerables observees chez les Vegetattx.
Journ, d'Ifist, Nattirelle de Bordeaux, t, iii., 1884, p. 156.

76 EXPERIMENTAL EVOLUTION LECT.

artificial race at its highest standard, and we all know
how readily degeneracy interferes with and ruins the
work of man or nature.

Dimensional variations, although very considerable,
cannot be regarded as unlimited. We cannot expect
to make any species of plant or animal become much
larger or much smaller than it is. Of course there are
natural or artificial conditions Under which all species
acquire a better development, and many facts display
this. But we cannot expect to be able to increase
the dimensions of any species beyond a certain point.
Such an increase would require numerous variations in
all the systems of the organism, stronger bones for
instance, a stronger heart, and so on.1 And then, on
another side, giant forms would require so much food
that their number could never become very large, and
in fact, much goes to prove that such forms would
have much trouble to compete with others, while the
smaller forms could more easily live and maintain
themselves. So there certainly exists a limit to the
increase of dimensions — a physiological limit which
cannot be passed without danger to the organism.
Conversely, there is also a limit to the decrease of
dimensions. Too small animals or plants are too

1 Paul Bert (Sur le Maximum de Tailk que puissent atteindre les
Animaux Vertebres : Soc. de Biologic, 1878) considers the maximal
dimensions of vertebrate animals as dependent upon the strength of the
cardiac muscle.

n EXPERIMENTS ON STARVING 77

weak to thrive unless considerable variations also occur
in their mode of life ; or their fertility may be very
much impaired, and thus the species is liable to go to
ruin. Thus it seems that, as things are, the condition
of every species — including under this word condition
the state of all parts of the organism — is exactly what
it should be to meet the present external circum-
stances, and departures from this condition are possible
only when necessary to the species itself, through a
change in circumstances. Concerning decrease in
dimensions, we may note that while a continuous
decrease must surely end in death, there are cases
where a large loss may be sustained without bringing
about this result. I made some experiments on this
point, a few years ago, and obtained the following
results. Wishing to ascertain the loss of weight
which animals are able to sustain without losing their
life, I weighed a number of Invertebrates, crabs and
medusae among others, and kept them in pure sea-
water without any chance to get anything to eat,
although I have reason to suspect some more enter-
prising individuals did eat some of their brethren.
But many mishaps befell this experiment, in one way
or another — the course of true experiment seldom runs
smooth — and at the end of a fortnight most of my
animals were gone, so that, in order to prevent a
complete disaster, I preferred stopping the process and

78 EXPERIMENTAL EVOLUTION LECT.

taking note of the results. Of all my animals only
two were left : two Aurelia aurita, a species of medusa
common on the Mediterranean coast. I had originally
put three in the aquarium, but one had died. The three
I had begun with weighed 98, 82, and 57 grammes at
first. At the end of the fortnight the two remaining
famished creatures weighed but 25 and 13 grammes.
Assuming for accuracy's sake, and in order to prevent
an over-estimation of the result, that these two were
those which weighed originally 82 and 57 grammes,
we see that the loss has been at least two-thirds in
one case, and three-quarters in the other.1 This loss is
very considerable, for, as Chossat has shown in his
investigations on the effects of inanition, mammals die
before they have lost half of their original weight.
When the experiment was interrupted, my Aurelia
were in good condition, and seemed quite inclined to
live longer : in fact they did live. This experiment
should be repeated with Beroe ovata, or some other
species of this genus, for I have noticed that these
animals rapidly lose in dimensions when in captivity

1 Henry de Varigny, Bemerkung iiber den Gewichtsverlusl durch
Nahrungsmangel bei Aurelia aurita. Centralblatt fiir Physiologic,
12 November, 1887. Of course it must be said that in this case the
greater proportion of the loss of weight is due to loss of water, since
water is in such animals even more abundant than in higher terrestrial
organisms. But it must be noticed that even if the loss of weight is
especially due to loss of water, the latter is due to the loss of organic
tissues or substances with Which the water Was combined.

SEMPER'S EXPERIMENTS 79

with little to eat. Of course it is quite natural that
organisms which do not eat become smaller, and if
under-fed as a rule they must doubtless remain of
inferior dimensions. But there are cases where, not-
withstanding abundant food, animals are unable
to grow to their accustomed dimensions. Herbert
Spencer says that it is well known by all anglers that
trout and other fishes are small in small streams, and
large in larger rivers, and many naturalists are of the
same opinion. Is it that these animals remain small
because they get less to eat ? or is there some other
reason ?

I have also made some investigations on this
subject during the past two or three years, and may
be allowed to recall them. The starting-point of
these investigations was the fact announced by Karl
Semper some twenty years ago, in a special paper
on the matter, which he has since abstracted in his
Animal Life, that if the common pond snail is kept
in small volumes of water, of less than five or six
litres, the animal does not attain its regular develop-
ment, and remains more or less dwarfed. For instance,
if three young pond-snails (Lymncea stagnalis, or
L. auricular -ia), of the same brood and age, are
put respectively into aquaria containing 500, 1,000,
and 3,000 cubic centimetres of water, a difference
in their dimensions may be detected even after a

UNJVEESIIl

8o EXPERIMENTAL EVOLUTION LECT.

few days, and if the experiment is allowed to last
some months, we finally see that the inhabitant of the
largest volume of water is the largest in all ways,
that of the smallest being smallest, and that of the
intermediate aquarium being between the two as
concerns dimensions. Such is the general fact. But
many points are to be considered when we try to
explain it. The first explanation which suggests
itself is that in the larger space there is more to eat,
and that the pond-snails in small aquaria remain
small because they cannot secure food enough. This
objection and explanation are amply met by the fact
that in all my experiments care was taken to provide
superabundance of food in the form of aquatic plants,
and that the animals, whether in small or large
aquaria, had always at their disposal, a much larger
quantity of food than they could possibly eat, or than
they really did consume. So this explanation cannot
stand. Prof. Semper has thought of a curious
interpretation. He supposes that there exists in
common water some matter which, while not possessed
of nutritive properties, is conducive to growth and
development, and is a sort of incentive to both. If
the animal lives in a small body of water it has but
a small quantity of this matter at its disposal, and
does not grow as much as an animal in a larger
quantity of water. This interpretation is contradicted

ii SEMPER'S EXPERIMENTS 81

by a very simple experiment. Take two equal
volumes of water, 1,000 cubic centimetres for instance,
and put one of them into a broad and shallow basin,
so that it extends over a large surface, while the other
is poured into a spherical glass vessel, so that the
horizontal surface is very small. The two volumes
are equal, but their form is quite different. Into each
vessel, with an abundance of aquatic plants — Myrio-
phyllum and Elodea especially : always submerged
sorts, so that they are not in need of a large surface,
and cannot interfere with it — put one pond-snail
of the same brood, or cluster of eggs, recently
hatched. The difference after a few days is sur-
prising, and in the course of time it is seen that
the pond-snail of the large-surface vessel is much
larger than the other one. As the volume of water is
the same in both cases, we must conclude that in itself
the volume is not that which determines the variations
of growth, and also that Semper's interpretation
cannot be accepted, for, whether spherical or wide-
mouthed, the same quantity of the same water should
contain the same amount of Semper's hypothetical
matter.

If, then, we cannot admit Semper's explanation,
what is the cause of the observed facts ? This
question may be answered by new experiments, in
which various conditions may be made to vary at

G

82 EXPERIMENTAL EVOLUTION LECT.

will and in different known degrees. In my first
series of experiments I used equal volumes of water,
but with different surfaces. One of the volumes, for
instance, was poured into a large-surfaced vase of
fifteen inches diameter, while the other was poured
into a vase of only four or six inches diameter. In
such cases I always found that the animals living in
the large-surfaced vase became much larger than the
others. Why so ? Is it that the water has better
aeration in the large-surfaced vase ? But this is of
no account at all. In the first place I would call
attention to the fact which I have repeatedly ob-
served since I began this series of experiments,
(and of which I am at present a daily witness),
that the aquatic plants which I used in my experiments
(Myriophyllum and Elodea canadense] do positively
thrive and grow much better in narrow-surfaced
vases than in large-surfaced vessels, in spherical
glass balloons with a long neck, in which the water has
but a very meagre surface contact with the atmosphere
(two centimetres diameter for instance), than in twenty
centimetres diameter vessels. This shows certainly
that in spherical vessels, with small surface, aeration
must be very good. On the other hand there is no
reason to think that aeration is better in one case
than in the other, as the water contains a large
amount of plants which ensure good aeration and

II THE AUTHOR'S EXPERIMENTS 83

(in the last instance) the pond-snails care nothing
whatever about the aeration of water, since they
are not gill-bearers but pulmonated ; they breathe at
the surface, and do not breathe the air contained in
the water. So aeration has nothing to do with the
matter. It has so little to do that I have, in some
experiments purposely devised, been able to see that
pond-snails live exactly as well in two identical
vessels (identical in shape, surface, volume of water
and amount of aquatic plants) one of which remains
open, in contact with the atmosphere, while the other
is stopped by a paraffined cork, the amount of air
imprisoned between the cork and surface of the
water hardly amounting to 50 cubic centimetres.
Even if it is argued that some air may pass in and
out, through the cork, the quantity is very small, and
we may consider the renewal of the air as very incon-
siderable so far as penetration from the atmosphere is
concerned. Of course the air does and must remain
quite suitable for the animals, since they thrive, and
the plants are the agents of this continued purifi-
cation. If the animals can and do live under such
conditions, and even live as well as they do when
the communication with the atmosphere is not inter-
rupted, does this not show that aeration must be
considered as quite sufficient even when the surface
is small ?

G 2

84 EXPERIMENTAL EVOLUTION LECT.

In a second series of experiments I varied the
volume of the water, but allowed the surface to
remain the same. For instance, into two vases of iden-
tical form and diameter I poured unequal volumes
of water. The surface was the same, but the volumes
were very different. In such cases, while the animals
were certainly larger in the larger volume, the differ-
ence was not considerable. The influence of volume-
variations is thus seen to be much less important than
that of surface-variations.

These experiments seem to me to call for the
following interpretation. The volume of water is in
itself of comparatively small importance, especially
for some species of pond-snails, and the real influence
is exerted by surface. And surface operates in this
manner only : the larger it is, the more exercise the
animals are able to take. The L. auricularia, to which
the above-mentioned experiments refer more especially,
seems to dislike deep vessels, and moves usually
in the horizontal plane near the surface. If the
surface is small it moves but little, while if it is
large the animal moves a great deal. On the other
hand L. stagnalis seems generally to care less about
surface or depth, and to prefer living in the deep
parts of the vessels where it is always moving about. I
have seen it in one case live almost all the time in the
deepest part of its prison (a glass balloon with a long

SEMPER'S EXPERIMENTS 85

narrow neck), and it acquired dimensions certainly
equal to those of another one living in a large-
surfaced vessel. There is some difference certainly
between L. stagnalis and auricularia in this respect,
and I call attention to this point.

I have tested Semper's interpretation in another
manner. I have caused pond-snails of the same age and
brood to live in unequal volumes of the same water in
the following manner. In some eases I have used
one, or two, or more glass tubes, of same length and
diameter exactly (two pieces of the same tube),
which were closed at one end with some muslin
stretched over the aperture, and made fast by means
of a string or thread wound around the tube. The
tubes were suspended in a large vessel containing
three or four litres, by means of a string, in such a
manner as to allow the other end to rise, say two
centimetres, above the surface (to prevent the animals
from getting out of the tube and going into the
vessel). In each tube I put one pond-snail, with a
sufficient quantity of aquatic plants (submerged al-
ways), and one in the vessel, outside of the tubes.
Every day, and many times a day, the tubes were
lifted so as to empty them of water, and immediately
replunged, so as to ensure the mixture of the water
inside them with the water outside; moreover the
water in the tubes was in constant communication

86 EXPERIMENTAL EVOLUTION LECT.

with the water around them, through the muslin, whose
only function was to prevent the animals from
escaping from the tubes into the vessel, or vice versa.
In all such experiments, the water being the same in
both tubes and vessel, food being superabundant,
temperature identical, and surface and volume only
being different, I have seen the pond-snails in the
tubes remain much smaller than those in the vessel. I
may even add that in some cases I have had one tube
as above described, and another stopped at the lower
end with a good cork and wax around it, so that the
water in the tube never got mixed with that of the
vessel, and have hardly if at all noticed any difference
in the dimensions of the animals of both tubes.

This experiment may be performed in another
manner by fixing up a sort of cage (with muslin and
glass rods), which affords more space than the tubes,
and more surface and volume ; the communication
between the water inside and the water outside is
still better, since it is effected through all the available
sides of the cubic cage ; the results are the same,
and the animal inside the cage remains much smaller
than the one outside it. This series of experiments
answers the objections which might be raised on the
ground that in the smaller volume of water the
proportion of waste products might be larger, and
exert a noxious influence. But these waste products

II SEMPER'S EXPERIMENTS 87

do not require to be taken into account in such cases.
I have also seen that unless a given volume of water
has been inhabited for a long time or by a large
number, it exerts no bad influence on the growth of
other pond-snails. For instance, take two identical
vessels, and use, in one, one litre of pure fresh water,
in the other the same quantity of water in which a
pond-snail has been living two or three months ; in
each put one young Lymncza, of same age and brood ;
kill both after the same time (three or four months) ;
there is no observable difference. Of course, if the stale
water has been much inhabited by pond-snails, the
growth of the fresh ones is impaired. But such
impairment does not occur in my experiments, and I
do not well see how waste products could accumulate
more in a narrow-surfaced vessel where aeration is
very good, as the plants show, than in a large- surfaced
vessel, where it must be also good, the quantity of
water being equal in both, or even, as is the case in
many of my experiments, superior in the former.1

So it seems that Semper' s interpretation has to be
dismissed as unnecessary, and that a simpler expla-
nation is furnished by the results of my experiments —
an explanation which depends upon known principles

1 All these experiments shall be related in greater detail in a forth-
coming memoir, as soon as I have completed the experiments
which are yet being continued (March, 1892).

88 EXPERIMENTAL EVOLUTION LECT.

of known influence. It is quite natural that exercise
should have an influence upon growth and development,
and that in cases where there are physiological or
mechanical impedimenta to movement, dwarfing should
be the result. I think that this is the explanation
which must be accepted ; and if animals living in
confined spaces remain small, this is due to the fact
that they cannot move enough. At all events Prof.
Semper's interpretation seems to me not acceptable.
Further experiments will yield new facts, and time
will tell whether this explanation is sufficient

In this connection I may call attention to the cir-
cumstance that an observer who has given some study
to dwarfing in Lymncea has pointed out a singular
fact connected with this process, but one which
requires to be confirmed by new investigations.

It is the fact that dwarfed forms are generally
exclusively female, and that their liver offers a con-
siderable amount of degeneration.

So much for dimensional variation.

If we now pass on to consider the integument, we
perceive that in this part, and in its appendages,
variations are numerous and also important. Many
animals, when transferred to warm climates, lose
their wool, or their hairy covering is much reduced.
In some parts of the warmer region of our earth
sheep have no wool, but merely hairs like those of

II INTEGUMENTARY VARIATIONS 89

dogs. Similarly, as Roulin notices, poultry have, in
Colombia, lost their feathers, and while the young are
at first covered with a black and delicate down, they
lose it as they grow in great part, and the adult fowls
nearly realize Plato's realistic description of man —
a biped without feathers. Conversely, many animals,
when transferred from warm to cold climates, acquire
a thicker covering, dogs and horses, for instance, be-
coming covered with wool, &c. Such cases are easily
observed in Europe when animals from the warm
regions are sent to our zoological gardens. In
Paris, for instance, we have seen sheep from Senegal
acquire, in the course of two years, a long and grizzled
cover of hair, while at first they had but a short one.
Similar modifications have been observed in a large
number of animals, and more precise data could have
been obtained if more attention had been paid to the
subject. As M. Faivre rightly remarks in his La
Variabilite des Especes et ses Limites (1868), while
" no truth is better established in natural history
than the influence of climate on the superficial cha-
racter of animal species, on the dimensions, colour,
form, nature of integuments and hairs, none has been
less investigated and discussed by the naturalists
whose business is to distinguish — one might even
say, to multiply — species."

Variability and variation of such superficial cha-

90 EXPERIMENTAL EVOLUTION LECT.

racters sometimes go to such an extent that animals
of the same species have been at times considered as
belonging to different species, and even to different
genera. Such has been the case, for instance, with
two fishes — Abramis versicolor and Stilbe americana —
which C. C. Abbott recognizes as one and the same
species which has a great tendency to variation,
not only as concerns colour, but in respect of fins and
scales, according to its environment.1 This is doubt-
less an extreme case, but its interest is considerable,
in that it exemplifies, on the one hand, the importance
of variation, while, on the other, it shows once more
how very artificial and unsound our specific and even
generic distinctions in some cases are. While we
ascribe most of the superficial, or integumentary,
variations to that general and complex factor which
we call change of climate — although we cannot in all
cases tell which particular factor of the complex
operates — there are cases where we can trace the
variation to one determined cause. Such is the case
with the variation in length of wool. There is a direct
relation between the abundance of food and the length
of the wool of sheep, for instance. Krocker,2 in
Proskau, has shown that the amount of wool yielded

1 C. C. Abbott : Notes on the Cyprinoias of Central New Jersey.
American Nattiralist, vol. viii. p. 326.

- His paper has been published in the Annalen der Landwirthschaft
in den Koeniglich Preussischen Staaten for 1869.

n INTEGUMENTARY VARIATIONS 91

daily per 1,000 kilograms of sheep varies in the
following proportions according to the food : —

Kg.

o'69i of wool : scanty winter food.
0*870 ,, plenty of hay.

0*958 ,, good pasture.

ro8o — 1*240 ,, fattening process.

If we now turn to plants, we perceive the same
variability in the superficial integumentary organs.
I merely recall here — because I shall have to refer to
it at greater length later on — the considerable differ-
ences which many observers have recently noticed in
the anatomy and characters of the same parts which
successively lead aquatic and aerial lives. In these
cases the influence of environment is easily to be
traced and appreciated. It is also well known that
where mountain-plants are transferred to the valleys
and plains they lose the hairy covering which they
generally possess, while valley-plants transferred to
the mountains acquire this same covering. Linnaeus
noticed that Persicaria is devoid of this sort of down
when living in humid places, while it becomes very
villous in dry stations. The same is noticed of
Thymus serpyllum. Many plants, in short, exhibit
two varieties which are readily distinguishable — the
glabrous and the villous ; such are Prismatocarpus
speculum, Isatis tinctoria, Jasione montana, Onopordon
acanthium.

92 EXPERIMENTAL EVOLUTION LECT.

Similar cases are met with among spiny plants.
While some plants, which possess no spines, become
markedly spiny when they grow in some localities,
others, which are spiny, lose their appendages. Such
is the case with Capparis spinosa for instance, of which
Turrel l has described a variety without spines in the
Balearic Islands. In all other respects this variety
exactly resembles the common form. Whether a
lusus naturae or not, this peculiar character is heredi-
tary, as the seeds of this form always yield non-spiny
plants, in France as well as at Mahon. Another case
is that of Ulex europaeus, of which there exists a non-
spiny form, as Trochu has shown.2 This form is
seldom met with, as it has less chances of success in
the struggle for life, for while oxen, rabbits, hares,
and other animals are respectful and deferential
towards the common spiny form, they have a great
liking for the other one, and eat all they can of it. It
must be added also that the last-named bears but
few seeds, and thus cannot become very abundant.
De Jussieu considers this Ulex nanus as a variety of
Ulex europaeus, and Vilmorin has made some in-
vestigations concerning this form,3 which may become

1 L, Turrel : Sur le Caprier sans Epines. Bull. Soc. Zool. Acclima-
tation, vol. viii. p. 448.

2 L. Vilmorin : De PAjonc sans Epines. Revue Horticole, vol. xii.
p. 151.

3 Note sur un projet d? Experience ayant pour but de creer line Variete

li FORM-VARIATIONS 93

very useful, as it can be given as food to animals
which will not eat the common spiny form. His first
experiments have not proved satisfactory, for the seeds
of Ulex nanus have always yielded plants of Ulex
europaeus. But since the tendency to vary is strong
enough in Ulex europaeus to afford some plants vary-
ing in the direction of non-spinosity, we may hope
that by means of careful selection Ulex nanus may
become an abundant and permanent form.

So much for integumentary variations. While con-
sidering variability of external and superficial charac-
ters, we may now say a word of form-variations.
These are very frequent among many groups of
animals, and particularly among molluscs. Locard,
in his interesting and valuable Variations malacolo-
giques (vol. ii.), has collected many instances of form-
variations noticed by himself and by others. In
his opinion, Lymnaa frigida and thermalis are mere
varieties of L. peregra, while Ancylus rupicola and
thermalis are varieties of A. simplex, the only differ-
ence being a matter of mere form. Brot has noticed
that in the cool mountain waters, Lymncea auricularia
has only four whorls to its shell instead of five, and
the Marquis de Folin observes that the pond-snails of

iCAjonc sans epines, se reproduisant de graines. Bulletin de la
Socitte Industrielle d' 'Angers, 1851. Also in Notices sur I' Amelioration
des Plantespar le Semis, 1 886.

94 EXPERIMENTAL EVOLUTION LECT.

the Lake of Constance are less regular in form, more
abrupt, he thinks on account of the movements of the
water of the Lake.

Baudin also considers Pisidium pulchellum and
cinereum as two forms of the same species, and
Locard himself has discovered through experiments
that L. turgida and elophila are mere varieties — due
to environment — of the common Lymncea stagnalis.
He says : " These are not new species, but merely
different aspects of a common type, which is capable
of modification and of adaptation according to the
nature of the media in which it has to live." Bateson
has recently observed similar facts concerning Cardium
edule ; Locard shows how extensively any one species
— Unio rhomboideus for instance — varies in forma
and in colore according to its habitat, lake, river, or
torrent, and an indefinite number of such instances
might be quoted here. The same may be said con-
cerning plants. All know that in different stations the
same species exhibits considerable differences in form,
in the comparative height of the stems, in the number,
length, distance of the branches, and so on, and ex-
perienced practical botanists easily recognize through
these differences the origin of an individual plant,
detecting whether it has grown in a valley or on the
Alps, in dry or in moist soil, in an exposed or in a
protected station, As the well-known fungologist,

ii FORM-VARIATIONS 95

M. Boudier, of Montmorency, says, in valuable notes
which he has kindly written down for me in answer
to many queries, " plants growing in dry, unprotected
soil are small and dwarfed, while the same species
living in moist soil are more vigorous, more developed,
and especially much taller. A common species,
Serratula tinctoria, grows indiscriminately in dry and
in moist soil ; in dry and unprotected stations it seldom
is over ten or twenty centimetres' in height, while
in moist soil it easily attains one metre (100 centi-
metres). The common dandelion '(Taraxacum dens
leonis] has in dry soil leaves which are much more
irregular and incised, while they are hardly dentate
in marshy stations, when it is called Taraxacum
palustre" Individuals of the same species grow-
ing near the sea-shore differ markedly from those
growing far inland. Similarly species, such as some
Ramuiculus^ which can live under water as well as in
the air, exhibit marked differences when considered in
their different stations, as is well known to all.
These differences may be important enough to induce
botanists to believe in the existence of two different
species when there is only one. A century and
a half ago, G. Bauhin and Tournefort described two
different species of Coriander. But Fabrejou, a
botanist of that time, who has written a large treatise
on systematic botany, under the title, Description des

96 EXPERIMENTAL EVOLUTION LECT.

Plantes qui naissent ou se renouvellent aux environs de
Paris} was able to show that the two so-called species
are one and the same. " Here is the proof," he says :
" When the same seed, sown in fertile and infertile soil,
yields the two so-called species, one must conclude
that there is but one single species, and that that which
seems to establish a difference between the two so-
called species, can only come from the climate and
culture. It is certain, as I have often witnessed the fact,
that the same seed, sown in fertile and infertile
soils, produces the two alleged species." And Prof.
Bonnier, recently, in his Etudes sur la Vegetation de la
Valle'e de Chamounix et de la Chaine du Mont-Blanc
(1889), says, corroborating others, that "in high alti-
tudes the appearance of the same species is dissimilar :
the stems straggle on the ground, leaves are narrower
and thicker, flowers are comparatively large and of
higher colour, and most of the plants even lose many
morphological characters which they possess in the
plains. . . . The characters of plants of high altitudes
are even different enough to have induced many
writers to describe these alpine forms as particular
species." Prof. Bonnier's statements are of especial
value from the fact that they are based on facts derived
from experiments made in stations situated at different
altitudes ; they are not facts of mere observation.

1 1740, 6 vol. in 1 8, vol, iii. p. 244.

LEAF-VARIATION 97

I have alluded to the considerable morphological
variations which are observed in Ranunculus aquatilis,
Godron, who, in 1839, published an important mono-
graph/ of the Ranunculus group, has studied these
variations with great detail. When the plant develops
wholly under the surface of water, all its leaves are
delicately laciniated. If the plant is able to send
some of its leaves to the surface, they float and assume
a very different form, being kidneyvshaped and lobed.
The same plant when growing entirely out of water
presents a very different appearance : the stem is
short, much divided into branches, which bear a large
number of small leaves, cylindrical, much divided,
and somewhat thick. If it were not for the floral
organs, one would certainly believe in two or three
species. There is but one, however, which varies
greatly according to external circumstances, and this
is shown by the fact that the same individual plant
under different circumstances presents the different
appearances which have been mentioned. Lamarck
believed that Ranunculus aquatilis might be trans-
formed into R. hederaceus through changes in the
environment, but Godron denies the fact. Rubus
fruticosus seems also to vary considerably. Sagittaria
sagittcefolia, when growing in deep water has also
ribbon-shaped leaves, while in shallow water it has
also arrow-shaped leaves, which rise vertically instead

H

98 EXPERIMENTAL EVOLUTION LECT.

of floating horizontally. Similar variations in form
are to be observed in Myriophyllum verticillatum and
Juncus supinus, and many other plants. Polygonum
amphibiiun also exhibits important morphological
variations. When growing out of water it has lanceo-
lated, downy leaves, with short stalks, and covered
with stomata on both faces, while the same leaves, if
the plant is growing under water, are deprived of hair,
have a long stalk, a,nd are obtuse, without stomata on
the lower side. These two forms of leaves are often
met with on the same plant, where it has been,
through accidental circumstances, growing for some
time under water and for some time out of water.
Ch. Martins 1 notices similar facts concerning Jussicea
grandiflora, where the variations are even more im-
portant. Every one may notice in our common ivy
considerable variations in the form of leaves, and these
variations are also to be seen in other plants, in fact
they are more or less present in most plants, and
careful investigation will disclose their number and
importance.2 These variations, which seem to be of
no account as far as the general life of the plant is
concerned, may however be accompanied by important

1 Observations sur la Jussicea grandiflora, in Bull. Soc. Botanique
de France, vol. xiii. p. 176.

2 G. Fournier : Recherches Anatomiques et Taxonomiques stir la
Famille des Crucijeres, 1868, and also Faivre : La Variabilite des
Especes et ses Li mites, 1868.

FRUIT- VARIATION 99

differences in the physiology of the plant. For in-
stance, Carriere,1 after having noticed the formal
variations of the leaves of the ivy according to its
mode of life (climbing, or entirely independent and
tree-like), adds the significant fact that the leaves of
the climbing plant when inserted in the soil readily
start an independent life, and emit roots very soon,
while those of the independent form do so only with
great difficulty. Here is certainly an inportant
physiological difference ; not perhaps in itself, but as
indicating differences in the structure and life of the
whole plant.

Fruits vary as well as leaves ; the same branch of a
peach-tree, for instance, bears peaches and nectarines ;
the same branch of an orange-tree bears oranges and
lemons ; the same branch of an apple-tree bears quite
different varieties of apples. Prof. Decaisne, who was
an authority in the matter of fruit trees, especially
apple and pear, observed2 considerable variations
among the descendants of seeds of the same sort ; in the
course of a few years, from the same seeds, he obtained
six different forms of pear-tree, in which the fruits
were unlike, while differences also existed in the
general morphology of the plant.

1 Polymorphisme des Vegetaux. Revue Horticole, 1886, p. 209.

2 De la Variabilite de F Espece dans le Poirier. C. R. Acad. des
Sciences, 1863.

ioo EXPERIMENTAL EVOLUTION LECT.

Among flowers the same variability obtains. Colour
may be different, but there are also important varia-
tions of a morphological order, and many botanists
have pointed out the more interesting cases in all
parts of the world. Maxwell Masters has collected
a number of them in his Teratology, and Udo
Dammer has added many in the German edition
of this work; more recently, Dr. O. Penzig, of
Genoa, has collected all known cases anew, in his
important Pflanzen-Teratologie (1890). In this book,
of which only the first half has yet been pub-
lished, we find a very complete list of teratological
cases, of cases of variation in all parts of the plants,
and of every sort, so that I may refer to this book
once for all, as concerns all plant variation. Some
idea of its value may be gathered from the fact that
1 66 large octavo pages are filled up with the mere
titles of papers referring to variation, and that the
whole work is devoted strictly to facts, so that it may
really be considered as a list — as complete as possible
— of all departures from the normal types. Of course
variations of floral structures are numerous, and cases
abound in this work, but I prefer referring, as an
instance, to a case which is not noted by Dr. Penzig,
and which is of great interest, as it concerns import-
ant variations observed in the floral structures of one
and the same individual plant, a Tradescantia virgi-

FLOWER- VARIATION 101

nica.1 "This plant," says Mr. G. A. Brennan, "presents,
as the result of thirteen years' cultivation, the curious
aspect of a monocotyledonous plant bearing in
bloom at the same time flowers of dimerous, trimerous,
tetramerous, pentamerous, hexamerous, and hepta-
merous types respectively, each flower bearing twice as
many stamens as sepals, petals, or carpels of the ovary.
The plant was set out in 1872, and received very rich
treatment, so that it gave forth blossoms measuring
two inches in diameter. In 1874 it began to depart
from the original trimerous type and to assume the tetra-
merous one, by developing another petal, and instead
of doing this at the expense of the pistil or stamens, it
added another sepal, another carpel with style, and two
stamens, thus making a typical tetramerous flower.
The plant has since then continued to differentiate in
a greater degree each succeeding year." In 1876 it
became pentamerous, in 1879 hexamerous, in 1882
dimerous, in 1886 heptamerous ; thus you perceive that
there has been no regular order in the course of
differentiation. At present, while the pentamerous
type is dominant in this plant, dimerous and hepta-
merous flowers are scarce. It seems that further
variation is forthcoming, for an octamerous ovary has
been detected in one flower. This fact is certainly

1 G. A. Brennan : Variations of Tradescantia virginica. American
Naturalist, vol. xx. 1886, p. 55.

102 EXPERIMENTAL EVOLUTION LECT.

one of the most striking which can be quoted in
respect of floral morphological variation. Such varia-
tion is always present among different varieties of the
same species. For instance, C. E. Bessey l has investi-
gated the floral structures of different varieties of
apples, and while it is generally thought that no
difference obtains, he has detected considerable
differences in the form of the stigmas and styles, and
found that the pistil varies much in length, breadth,
hairiness, &c. And the proof thereof is seen in the
engravings which accompany his paper, and refer to
five well-known varieties of apples — red Canada,
Talman Sweet, Rambo, Wagner, &c.

The very smell of flowers is also subject to variation,
as Dalibard 2 showed by direct experiment nearly a
century and a half ago. He planted mignonette in
different soils, using seeds from the same mignonette
plant, possessing its well-known fragrancy. While
the seeds sown in rich garden soil became vigorous,
and were well perfumed, the seeds sown in sandy soil
produced plants which remained weak and small, and
had no perfume. It even seems that the latter
did not acquire any odour when transferred to rich

1 Can Varieties of Apples be distinguished by their Flowers ?
American Nattwalist, vol. xx. 1886, p. 162.

2 Observations stir le Reseda a few odorante, in Me moires de
Mathematiqucs et de Physique de V Academic des Sciences, 1750,
P- 95-

OSTEOLOGICAL VARIATIONS 103

garden soil. Similar facts have since been repeatedly
observed and noticed.

In the more internal functions and organs of animals
— and of plants as well — the same variability shows
itself. In man himself, as Mantegazza has shown, teeth
vary considerably, and a careful study of the third
molar tooth has shown that there is a strong tendency
towards the disappearance of this part, and while among
inferior races all that concerns it is normal in 50 to 54
per cent., abnormality becomes considerable among
superior races, where the normal state is only met in
37*09 per cent., leaving 62'9i abnormal in one way or
other. No doubt, we could find numerous cases of
variation in the dentition of mammals, although
the number and form of teeth is considered as a
specific character. But teeth may be considered as
external organs in some sense, just as fur or feathers ;
and it is even more interesting to see that more
internal parts vary perhaps as much, if not more.
Such is the case with the bones which go to make
the skeleton of mammals and other animals. Some
instances are referred to by Darwin, and by Wallace
in his recent and valuable Darwinism ; St. George
Mivart has shown that the number of ribs varies among
the apes ; in man himself the number varies from
twelve to thirteen ; and concerning whales, Georges

io| EXPERIMENTAL EVOLUTION LECT.

Pouchet l says : " Balaenidae certainly are among
those higher vertebrates whose skeleton exhibits
least fixity ; this is a peculiarity which cannot be
denied." The same writer also says that in many
species which live in limited regions the same skeletal
variability exists in a marked degree, and although
the individuals are absolutely similar so far as exterior
characters are considered, they may display a varia-
bility which may be said to be unlimited, in the
number and relations of the bones. And Pouchet and
Beauregard 2 say also that it would prove difficult
to meet with two skeletons of the Anteater which
were exactly similar as concerns the number of the
ribs or vertebrae, or the connections of the ilium or
ischium with the vertebral column.

As to differences in weight and length of the skeleton
in different individuals of the same species, Darwin
and Wallace have also collected numerous data of
which all are cognizant. The soft parts of the body
display the same tendency. All have heard of John
Hunter's experiments on the sea-gull (Lams tridacty-
lus}. He fed it during a year on grain, with the result
of hardening to a large extent the inner coat of the

1 A propos de deux Photographies de Baleine Franc he. Compt. Rend,
Soc. Biologie, 1890, p. 705.

- Traite d? Osteologie Comfaree, 1889, p. xii.

II VISCERAL VARIATION 105

stomach of this animal, which, being a flesh-eater, does
not require to have the hard and horny coating of the
gizzard of the pigeon or fowl. This experiment is
repeated each year in nature, and without man's
operation, by another gull (Larus argentatus}, of the
Shetland Islands, which, according to Dr. Edmonstone,
changes the structure of its stomach twice every
year, according to its food, which consists of grain
during part of the year, and of fish during the other
months. So the stomach may vary considerably in
its use and functions, and Holmgren's experiments
show that the gizzard of a grain-eater, such as the
pigeon, may be converted into a carnivorous stomach,
such as that of one of the birds of prey.

I have already said that there is great variability in
the muscular system. Some anatomists have made
a special study of this variability : Wenzel Griiber
in Germany, Testut in France, Cunningham of
Dublin, and many others. Not only are there
variations in the mode of attachment and course of
every muscle of the human body — which has been
more especially studied in this connection — but super-
numerary muscles are often found which are all exactly
similar to muscles which normally exist in lower
animals, but do not as a rule exist in man. Testut
has dwelt upon this fact, which is of great significance
in the evolution theory, and a very large number of

io6 EXPERIMENTAL EVOLUTION LECT.

instances might be given of man having muscles which
are considered as peculiar to the ape, horse, dog,
bear, &c. 1

Variations also occur frequently in the anatomy of
many internal organs. Wallace refers to the
variability in the length of the digestive system in
the giraffe and other animals, and in the nature and
position of the gall-bladder, which in the same species
is sometimes present, either single or double, some-
times absent. These variations are not confined
to higher animals. Claus observes that ^Equorea
forskalea, a Ccelenterate, varies much in the number
of the radiating canals2 ; and many botanists have
noticed the important structural variations which
obtain in plants. E. Mer has carried his investigations
into great detail in regard to Isoetes laciistris, and
other plants.3 It results from these investigations
that the internal anatomy of plants may vary
considerably. This variability displays itself also in
regard to sex ; for it has been shown that external
influences play a large part in the determination

1 Cf. R. Wiedersheim, Der Bail des Menschen ah Zeugniss seiner
Vergangcnheit (Freiburg i. B., 1880).

2 American Naturalist, vol. xvi., 1882, p. 147.

3 De F Influence exercee parle Milieu stir la Forme, la Structure, et le
Mode de Reproduction de F Isoetes lacustris. Ccmptes Rendus 1881, p.
94 (Jan.-July). See also Des Causes qui modifcnt la Strttcture de
ccrfaines Plantcs aquatiques vegetant dan F Eau. Bull. Soc. Botanique^
1880, p. 194.

SEXUAL VARIATION 107

thereof. Whilst among tadpoles left to themselves,
the females are in a slight majority, the proportion
increases from 54 to 78 per cent, when the
tadpoles are fed with beef, to 8 1 per cent, when fed
with fish, and, when fed with frog-flesh, to 92 per cent.1
Thus food, and the nature of food, has much to do in
the determination of sex. The same is the case with
bees, where the production of queens, workers, and
drones is in great part a matter of nutrition. A
worker-larva may be reared into a queen, if royal food
is provided. Other facts show similarly that external
influence must be at work to operate in the deter-
mination of sex. Fisch has noted the sex of 66,327
plants of hemp, and he finds there are 154 female
against 100 male plants. Among other plants, such
as Spinacia oleracea and Ruinex acetosella, the
proportions vary much, as in some cases the one sex,
in others the other, is predominant. In the human
species males are constantly in slight excess over
females — 105 against 100. The same condition
obtains among oxen, sheep, hogs, and domestic
birds. But in the case of the latter, the constancy
is less, and during some particular years there is
a very large number of individuals of one sex
against a small number of the other. There

1 See Yung, Propos Scientijiques, 1890, Reinwald, Paris, quoted in
Evolution of Sex, P. Geddes and J. A. Thomson, Lond. , 1889.

io8 EXPERIMENTAL EVOLUTION LECT.

are some external causes in operation which are
not yet detected. M. C. Cornevin thus summarizes
the proportion of males to 100 females in the
following species : —

Horses 101 males against 100 females.

Oxen 104-6 „ „ „ „

Sheep 115-4 „ „ „ „

Hogs 104-9 „ „ . „ „

Turkeys 120 „ „ „ „

Guinea-fowl 102 „ „ „ „

Common fowl 101 „ „ ,, „

Duck 115 „ „ „ „

That external influences do play an important part
in the determination of sex is shown by numerous
facts. Spallanzani, Bernardi, and Autenrieth have
shown that female plants of hemp when mutilated
bear male flowers, and M tiller has in some cases seen
male plants bear female flowers. M tiller has also ob-
served female plants of Zea Mays bearing male flowers
when nutrition was deficient. Hoffmann has noticed
that in Lychnis, Spinacia, and Rumex the proportion of
sexes varies according to the greater or less interval
between each individual plant ; and Cornu, Giard, and
Magnin have shown that in Lychnis vespertinci, under
the influence of parasitic " rust " ( Ustilago antherarum\
female flowers bear stamens. Prantl has seen similar
facts among Cryptogams. While the (seeds/ of ferns

SEXUAL VARIATION 109

develop into male plants when the soil is poor in
nitrogen, or when the seeds are very near each other,
they yield female plants when nitrogen is abundant,
and the seeds somewhat distant.

Yung's experiments on tadpoles had already been
performed by Born with similar results, and it seems
that in the human species, a change of climate is
often conducive to a larger production of females.
In Java, for instance, European or white children are
born in the proportion of five females against two ,'
males ; in Yucatan, in the proportion of eight /
females against two males.

All these facts go to show that sexuality is in
great part determined by external factors, whatever
these may be, and that much variability is here
present. This variability may be readily seen in the
same species, under different conditions, and even
in the same individual. For instance, Carriere has
pointed out that variability is common in Ailanthus
glandulosa,%. well-known plant in which the distribution
of sexes is very inconstant. While some individuals
bear a large number of female flowers, many bear but
few, and it is a curious fact that they are all to be
found on the same branch, instead of being on different
branches, interspersed with male flowers. There
seems to be some special condition in one or more
branches which determines the production of female

i io EXPERIMENTAL EVOLUTION LECT.

flowers.1 This condition may vary from one year to
another, in the course of the lifetime of the plant. It
even seems that in normally male plants, this condition
may put in an appearance. Ch. Martins 2 observed at
Moritpellier a male Chamcerops humilis which yielded
only male flowers from 1851 to 1861 ; in 1861 this
plant produced some female flowers, quite normal,
since the seed from these flowers yielded vigorous
young plants; and in 1862 a large proportion of
female flowers were to be seen. This last fact is of
real importance, as showing that sexual variability
may exist to a high degree.

Another very interesting form of variability is that
which may be observed in individual evolution or
development. Although there are numerous cases of
this sort, and although a large number of instances
might be quoted where the individual evolution is
readily arrested or modified through different circum-
stances, none seem more carefully ascertained than
those which Camerano has published. This writer has
investigated what Kollmann has called Neotenia in
Amphibians. Neotenia is the lengthening (for an
indefinite time) of the period during which Amphibians
are gill-breathers. Every one knows that, at first,

1 Carriere, Sur FAilanthus glandulosa a propos des Sexes. Rev.
Horticole. 1872, p. 234.

Ch. Martins, Transformation d?un Chamcerops humilis male en
polygame. Rev. Horticole, 1862, p. 353.

ii NEOTENIA in

frogs, toads, &c., breathe as tadpoles, by means of
gills, and that after a few weeks the lungs develop
and the gills disappear, while the animal becomes an
adult, and acquires new characters and organs. But as
every one can ascertain, this gill-breathing period may
be considerably lengthened under natural or artificial
and experimental circumstances. I have myself kept
toads in the tadpole state for over two years, merely
by feeding them very scantily. They were born in
the spring of 1889, and remained all the time in an
aquarium in the laboratory, having water enough at
their disposal, being always sufficiently provided with
aquatic plants, and enjoying heat enough : it cart by
no means be said that their evolution was arrested by
the cold of winter, as often happens in mountain ponds,
when the cold of autumn sets in before the tadpoles
have achieved their development, so that they become
frogs or toads only in the course of the following
year. In the case of my tadpoles, it seemed that the
completion of development was due to my imprudent-
ly feeding them in the spring of 1891 on the very sub-
stantial flesh of their congeners ; and in the course
of some three weeks at most, the limbs were evolved,
the long tail disappeared gradually, the very colour
and appearance of the skin underwent considerable
changes, and my superannuated tadpoles became
toads at last. This Neotenia has been observed by

112 EXPERIMENTAL EVOLUTION LECT.

many physiologists in different Amphibians. Mile, de
Chauvin has reared larvae which were the progeny of
Amblystoma, and while some of them became
, Amblystoma, others remained Axolotls in con-
sequence of being kept in very well aerated water,
where the gills had no tendency to atrophy or retro-
gression. Similar experiments have been performed
by a large number of naturalists on different species
of Triton, Salamandra, Pelobates, Alytes, Hyla, Rana,
and Rnfo ; and the result is that while there arc
Amphibians, such as Salamandra atra, in which the
length of the branchial or gill-bearing period is very
short, and others, such asfroteus anguineus, and some
Tritons and Axolotls, where gills exist normally in
adult and even in aged individuals, there exist
also a number of Amphibians among which the
gill-bearing period, normally short, may be much
lengthened. But in Urodela (newts and sala-
manders) this lengthening1 may and does occur
without seriously modifying the evolution of the
remainder of the body ; and the result is that these
tadpoles are sexually mature, while among Anura
(frogs and toads) this lengthening interferes with the
general development, and sexual maturity does not
seem to occur among the tadpoles. New investigations

are required to ascertain how far this sexual immaturity

>**

exists, and to what extent it may be retarded by the

II NEOTENIA 113

lengthening of the gill-breathing period.1 If it could
be shown that sexual maturity may occur although the
tadpole state is lengthened, and that sexual reproduc-
tion may take place, although this is on obvious a
priori grounds very improbable, we might perhaps try
to obtain a new species which would exhibit very
marked physiological features.

1 Camerano, Stir le Developfenient dcs Amphibiens, et sur ce que ton
a nomme chez eiix la Neotenie. Arch. c'ltaliennes de Biologic, vol. v.,
1884, p. 27. Recherches sur la Prolongation de la Periode branchial e
des Amphibiem. Ibid., p. 29. Recherches sur le Developpement et les
Causes du Polymorphisme des Tetards des Amphibiens anoiires. Ibid.,
xv. 1891, p. 165.

LECTURE III

Summary : The Facts of Natural or Spontaneous Variation (concluded) —
Physiological or Chemical Variation — Not always easily detected.
— May be noticed in all parts of the Body, even between very
closely related Forms — Exists not only between different Species,
but between Varieties of the same Species, Individuals of the same
' Variety, and even different ages of the same Individual — Chemical
Variation explains Racial Immunity to peculiar Diseases — This
Chemical or Physiological Variation in some cases of much higher
import than any Morphological Variation — Chauveau's Experi-
ments on Bacillus ant hr ads — Physiological Differences between
Brown and Green Frog towards Poisons and Heat — Tarchanoff's
Experiments — Variation generally exists at all Ages, in all Groups
of Beings, at all Geological Epochs— Sudden Variation.

THERE is a last form of variability to which I wish to
call attention, and which has not been enough taken
notice of up to the present time. I refer to what I have
mentioned under the name of chemical or physiological
variability. Under this name I include all facts which
indicate a difference in chemical or physiological con-
stitution, expressed through differences in the reaction
of the organisms towards definite and common external
influences. Such chemical variation must certainly
exist at the basis of all specific or even racial characters,

LECT. in VARIATION IN PHYSIOLOGY 115

and if I dwell somewhat upon the topic, it is owing to
the fact that this sort of difference has not been as much
investigated as it ought to have been. Between two
species, however closely allied, between two varieties or
races of the same species, there are not only those slight
external differences upon which so much stress is laid
by morphologists ; there are internal, chemical and
physiological differences which are most likely of
greater importance. For instance, Naudin cultivates in
his gardens at Collioure, in the south of France, a
number of plants of a species of Echium ; part are
indigenous, part come from the Canary Islands ; they
all exactly resemble each other, no external difference
is perceptible ; they differ in origin only. During the
night, the frost comes ; all the Canary plants die,
while the plants of France resist. There is some
difference in their constitution or physiology, some
difference due to habit, to adaptation, however it
may be called, and the result is that life may continue
under circumstances which cause it to cease when this
difference does not exist. This is one fact among
a thousand, and horticulturists and breeders could
provide many similar examples. It shows that,
even in cases where no external differences are
perceptible, variations do exist in given circum-
stances which may be of the highest importance, and
decide life or death. Though they are not always of

I 2

ii6 EXPERIMENTAL EVOLUTION LECT.

equal magnitude, they admit of being detected
with real accuracy by appropriate methods. While
calling this variation physiological, I understand it
to be, in fact, chemical ; the difference is in chemical
constitution — most probably — but it displays itself
mostly in physiological differences. I have collected
some cases of this variability, endeavouring specially
to obtain widely different instances, in order to show
the extent to which this kind of variation occurs.

Of positive chemical variability among animals, I
meet with a good instance provided by two well-
known savants — Ch. Robin, the histologist, and
Sainte-Claire Deville, the chemist — who, at Sanson's
request, examined comparatively the structure and
composition of the bony structures of the common
breed, and of a perfected breed, of sheep. While the
microscope detected no difference at all between the
two breeds, chemical analysis showed considerable
variations in the respective percentages of organic
and inorganic matters, as follows : —

Organic Substances. Inorganic Substances.

Perfected breed 32*3 per cent. 677 per cent.

Common breed 38*6 „ 61*4 „

Similarly, considerable variations obtain in the
chemical constitution of the integumentary append-
ages of different varieties of animals. Here follows,

in CHEMICAL VARIATION 117

for instance, the percentage of the principal com-
ponents of the wool of some breeds of sheep
(after Miintz and Girard) :—

Dfchley. Merino, Solognot.

Water .................. 15 10 14 15-5 16

Nitrogenous matters 63 48 53 64 53

Fatty substances ... 8 30 19 6 10

Ash ..................... ii 10-5 15 13 18

Potash .................. 6 4-5 7 6-5 4-5

While some components vary but slightly, such as
water and potash, others, such as fatty substances,
are found in very different proportions ; the difference
being from six to thirty, or from one to five.

Similar variations are to be observed in the mus-
cular or fleshy parts. Sir R. Christison made
chemical analyses of salmon in good health and con-
dition, and of salmon after spawning. The results
are as follows : — 1

Healthy Salmon. Salmon out of Season.
Oil ............ 18*53 per cent. 1*25 per cent.

Nitrogen ... 1970 „ 17-07 ,

Salts ......... 0-88 „ 0-88 „

Water ...... 60-89 „ 8o'8o „

It is not necessary to have studied physiology very
deeply to understand that such differences in the flesh
or skeleton, as are shown above, may be of great im-

1 From a paper read in the Royal Society, quoted in the American
Naturalist, vol. vii., p. 372.

i IS EXPERIMENTAL EVOLUTION LECT.

portance under definite conditions, and may deter-
mine life or death in some circumstances, while at all
events they must, in every-day life, put the animals
which exhibit them in very different positions as
regards the struggle for life and success in it.

Such differences are common in the chemical consti-
tution of the different species of the same genus, and
the following analysis by Forchammer well illustrates
this :—

Fitcu
Potash

s digit alus.
20-66
7-65
6-86
10-98
2-36

0-57
1-44
26-18

F. vesiculosns.
13-01

9'54
6-12
836
1-16
24*06
0-28
1-15
21-45

F. serrati

18-67
10-29

14-41

18-59
0*30
0-38
16-56

Soda

Magnesia

Lime

Phosphoric acid ...
Sulphuric acid
Ferric oxide

Silica

Sodium chloride ...

And again, among different individuals of the same
species considerable differences may obtain according
to the mode of life, and particularly, as Hermbstaedt
has seen, according to food. This fact is well dis-
played by the results of Hermbstaedt's experiments
on the influence of different manures on the propor-
tion of gluten and starch in wheat. Wheat from
common soil, neither rich nor poor, has 9-20 per cent,
of gluten to 66-69 °f starch ; manuring with human
urine yields gluten 39- 10 and starch 39*30, and each

in PHYSIOLOGICAL VARIATION 119

different manure more or less alters, between these
two extreme data, the proportions of these two im-
portant elements of the plant.

The foregoing instances afford an example of posi-
tive measurable variation in chemical constitution ;
and if we were better acquainted with the details
of the life-history of any species, we should readily
perceive the corresponding effects from the physio-
logical side : we should see, for instance, how such and
such chemical variation, which we can measure and
weigh, is of real advantage to those which possess it ;
while those without it suffer definite and generally
disadvantageous consequences.

In other cases we perceive the physiological effects,
while we are not yet acquainted with the degree or
even the nature of the variability. We all know that
different animals of the same or of different groups
react quite differently under similar unfavourable
circumstances. We know, for instance, that it takes a
much longer time to drown a frog than a reptile or a
bird, and we understand why ; we know also why a
duck or penguin can withstand submersion a longer
time than a hen or a quail. There are physiological
reasons for these facts, and we are familiar with them.
But in other cases such reasons must also exist,
although we cannot tell what they may be. For
instance, if different insects are subjected to the

120 EXPERIMENTAL EVOLUTION LECT.

same process which is injurious to life, as in Gratacap's
experiments,1 considerable differences are easily
perceived, though not explained. While the common
fly withstands living in pure oxygen less than thirty
hours, Doryphora decemlmeata survives easily for
three whole days, and Colias phyllodoce cannot stand it
more than twelve hours. While the same DorypJiora
can live twenty-four or even forty-eight hours in pure
hydrogen, a species of Noctua cannot live more than
twenty minutes, nor Poinpilns unifasciatus more than
ten minutes. Why, we cannot tell, but there cer-
tainly is some physiological and chemical reason
accounting for the fact.

Every physiologist knows well that the same poison
exerts very different influences on different organisms.
For instance, while brucine acts on dog or frog in the
same manner as strychnine (although stronger doses
are required than of the latter) it acts very differently
on the common crab (Carcinus maenas}, which exhibits
no convulsions but only a peculiar movement of the
external mouth-parts. Picrotoxin, similarly, acts on
dog and frog like strychnine ; on the crab it induces
a powerful contraction which is most characteristic.2

1 Gratacap, Vitality of Insects in Gases* American Naturalist, vol.
xvi., 1882, p. 1019.

2 Cf. Henry de Varigny, De t Action de la Strychnine, de la Brucine
et de la Picrotoxine sur le Carcinus maenas. Journal de V Anatomic et
de la Physiologic, 1889, Paris. Also : H. de Varigny and Paul Langlois,

in CHEMICAL VARIATION

It may be argued that such instances are not very
convincing : they concern very different species and
genera ; how can it be proved that such important
variations occur within the same species, for there is
the point ? To this the answer is easy to give, and
if we turn to any given species, we cannot fail to
notice important differences. Take the human species,
for instance, and consider the differences between man
and woman, then those between the races of man,
and finally between the different men of the same
race.

As an instance of chemical difference between man
and woman, here are the percentages of the principal
components of bony structures in man and woman of
the same age, after Milne-Edwards : —

Woman. Man.

Phosphate of Lime 62*15 5&'3~

Carbonate „ -. 4-52 9-98

Organic Substances 33'33 3170

Inorganic „ 66*67 68*30

And it must be noticed that the differences vary
according to the age of the patients, and even to the
side of the body. While in the young the proportion of
inorganic substances is smaller than in the adult, the
bones of the right side of the body contain more

Sur r Action de quelques Poisons de la Serie cinchonique sur le Cardnus
maenas (ibid. 1891), where similar facts are recorded.

EXPERIMENTAL EVOLUTION LECT.

than those of the left side, as H. Milne-Edwards
clearly recognized in his investigation on animals, and
such differences certainly obtain in man, as direct
experiments have shown. And such differences are
to be met not only between man and woman, between
one side and another, but also between one part and
another, lime-salts being more abundant in the thigh-
bone than in the arm, &c.

If we turn to the chemistry of the blood, the same
facts appear. Quetelet has analyzed the salts which are
contained in this fluid, and has seen that the differ-
ences arc as follows : —

Man. Woman

At one year 14/2 13-3

At ten years 37-1 34-4

At thirty years 98*9 78-4

There is more iron in male than in female blood
(Boussingault) ; there arc also more salts in male than
in female, more in the right thigh of the duck than in
the left one ; there are more red blood-corpuscles in
man than in woman (142 against 127, after Becquerel
and Rodier, or 4*5 against 3*5, after Malassez), and
so on ; and all these minute or important differences
in anatomical or chemical structure are accompanied by
more or less important variations in physiology. Of
these differences I shall give only one instance : it
is admitted in forensic medicine that when man and

in ARGUMENTS FROM PATHOLOGY 123

wife are drowned together, the wife is considered as
having died the last, because it is known that woman
faints sooner, and has therefore more chances to survive
than man, as experience has shown.

So much then for variability between the different
sexes of the same species. If we now compare two races
of the same species — mankind again — similar differ-
ences come in.1

While man and woman are respectively more liable
to certain diseases, each race seems to offer different
predispositions to the principal diseases flesh is heir
to. Pathologists are well acquainted with this fact,
and numerous instances of it are known. The following
figures show the death-rate from marsh fever among
Europeans (Englishmen) compared with negroes, in
different countries : — 2

Death-rate per 1,000
Englishmen Negroes.

Jamaica 101-9 8-3

Guiana 59'2 8'5

Trinidad 6r6 3'2

Sierra Leone 410^0 24

It has been sometimes said that negroes are entirely
refractory to malarial fever : the fact is not accurate,
but the figures show, at least, that the black race has,

1 Cf. G. Delaunay's interesting Etudes de Biologic Comparce basees sur
V Evolution et la Nutrition. 1878-9. A. Delahaye, Paris.
- After Borclier, Geographic Medicate. Paris, 1884, p. 475.

124 EXPERIMENTAL EVOLUTION LECT.

for some reason or other, much less to fear from malaria
than the " white devils." The same difference is found
concerning tuberculosis : while it is more dangerous
for Polynesians and negroes than for whites, it is more
deadly for the whites than for the Mongolians, among
whom it has been said that Thibetans quite escape
the disease. The statement may have been exagge-
rated : at all events, it shows that the yellow race enjoys
comparative immunity from tuberculosis. Similar
instances are frequent among animals : not only do we
meet with instances of diseases which are peculiar to
some species only,1 but within the same species some
breeds enjoy immunity while others do not. For in-
stance, Prof. Chauveau has shown that the sheep 01
Algeria enjoy a much greater immunity in respect to
anthrax than those of France, and the same differ-
ence obtains among asses. This is a racial character,
for foreign breeds living in Algeria do not acquire it ;
but the Algerian breeds transferred into Europe seem

1 For instance, anthrax affects sheep especially, while it is scarcer
among oxen, hogs, and horses, and is never met with among birds. To
glanders the pigeon seems to be the only bird at all susceptible.
Syphilis is peculiar to man, though it possibly may be seen in apes
and hogs. Rats and mice enjoy an almost perfect immunity from
diphtheria, and any number of similar cases may be found in any text-
book on Bacteriology. Perfect immunity is rather doubtful, but it is
quite certain that many virulent diseases, due to microbes, exist spon-
taneously only in a limited number of species, but may be conferred
experimentally upon some or many others under experimental condi-
tions.

in IDIOSYNCRASY 125

to lose it gradually, so that the influence of environ-
ment appears to have something to do with it.

And now, if we consider men of the same race —
and the same facts would appear if we were to con-
sider individuals of any species of animals or plants
— are we not all acquainted with facts of very notable
variability ? The same external influence acts quite
differently upon them, and of four men standing in a
draught, for instance, one will have pneumonia, the
other rheumatism, number three a bad cold, and
number four nothing at all but a temporary relief
from the heat of the day.

The very same morbid influence — typhoid fever as an
instance — acts differently, producing in the one patient
gastric symptoms, while cerebral trouble is predomi-
nant in another. Every physician can furnish any
number of similar instances, and can also show that
while in every epidemic of every disease there are
different forms of the same disease which are doubt-
less in correspondence with different personal variabi-
lities or idiosyncrasies, these idiosyncrasies vary from
one time to another, so that in one epidemic one form
predominates, while in another some different form
is most frequent. It thus seems that personal varia-
tion varies according to seasons and periods under
unknown influences. Or else, if no variation is
assumed to exist in the patients, there then exists

EXPERIMENTAL EVOLUTION LECT.

some variation in the pathogenetic organism. For
the present purpose this comes to exactly the same
thing, our only point being to show that variability
does exist in a marked manner.

Later on I shall have something to say concerning
the degree of variability among pathogenetic organ-
isms under different modes of culture or treatment ; it
is enough here to allude to the general fact of the
attenuation of many sorts of virus which has led to
the humane although as yet unexplained l practice of
vaccination ; but something must now be said concern-
ing the external manifestation of this variability.
Many bacteriologists have thought at times that it
might be possible to transmute one micro-organism
into another under definite circumstances, and we have
all heard of Biichner's or other experiments concerning
the relationship between the common hay bacillus and
the typhoid fever bacillus, as well as of similar in-
vestigations. But investigators seem to think much
too highly of mere morphological transmutations, and
to have too much disregard for other transmutations
which are in fact of much greater importance. They
seem to be running after shadows while substantial
reality lies disregarded at their very feet. Let us take

1 " Unexplained " refers of course to the process by which a bacillus
or bacterium, although in appearance unchanged, becomes incapacitated
for the production of disease of a virulent type.

in CHAUVEAU'S EXPERIMENTS 127

an instance. Here is that much investigated anthrax
bacillus. Many bacteriologists have tried to determine
morphological variations of the species through various
experimental methods, hoping to see it assume quite
different characters : but they have utterly failed.
Professor Chauveau studying the same general topic
of variability, has investigated it not on the morpho-
logical side, but on the physiological one. And he
asks very appropriately whether a bacillus which has
entirely lost its virulence, while retaining its morpho-
logical appearance — which is always very simple —
has not varied more than a bacillus in which form
might have varied while the pathogenetic properties
had remained unaltered ? The answer seems to me
manifest, that variability of virulence is of greater
importance than that of form and external appear-
ance, especially in the case of such very simple and
undifferentiated organisms, since this testifies to
deep modifications in the chemistry and vital pror
perties of the organism. How much more would
this be evident if the new characters acquired by
the organism were to remain unaltered from one
generation to another, without it being necessary
to provide permanently the special conditions or
the peculiar environment which initiated the produc-
tion of new characters ? And this case is not of
hypothetical nature ; it really exists, and I have been

128 EXPERIMENTAL EVOLUTION LECT.

a daily witness to it. Professor Chauveau, from long,
and, as usual very careful experiments on Bacillus
anthracis, has been able to show that while no known
method can as yet, entirely destroy the pathogenetic
influence of this micro-organism, nor confer upon it
new and different properties, the pathogenetic influence
may be destroyed to the extent that it can no longer
harm the animals in which it makes itself the most
easily felt. Such virus may be inoculated into guinea-
pigs and mice without doing the slightest harm. But
it has not entirely lost its properties, since it retains
its vaccinal influence : while apparently no longer
noxious to animals, while producing no disease nor
pathological symptoms, it acts like a vaccine lymph,
and confers immunity against the inoculation of viru-
lent bacillus, as experiment shows. Again, these devi-
talised or altered bacilli, which only retain a vaccinal
influence, may be made to acquire virulence of the
highest type through very simple experimental pro-
cesses. Lastly, these attenuated bacilli retain their
new characters (of non-virulence and of mere vaccinal
aptitude) as long as is required, without it being
necessary to use particular methods of any sort, and,
as M. Chauveau remarks, if one were to consider
these bacilli in themselves, apart from their origin,
and without knowing what they may be made to
become under appropriate experiments, they might

in CHAUVEAU'S EXPERIMENTS 129

certainly be looked upon as a distinct species. Between
this ultra-attenuated and the highly virulent breed
many intermediate types exist, but they have less
fixity, and their nature — as measured through their
pathological effects — is less constant. At all events
Professor Chauveau has succeeded in obtaining three
types of Bacillus anthracis :

Firstly, the ultra-attenuated type, which has lost all
pathological properties, and produces no disease even
in the most delicate and appropriate animals (mouse,
guinea-pig), but retains vaccinal influence, and can be
used for vaccination of the same animals against the
disease ;

Secondly, the semi-attenuated type,1 which kills
some species of animals (rabbit and guinea-pig), but
acts only as a vaccine in other larger animals ;

Thirdly, the less attenuated type, which kills the
rabbit, guinea-pig, and sheep, and plays the part of a
vaccine only with the horse or oxen.

These different types may exist in Nature, and some
facts go to show that some of them probably do
exist.

The foregoing facts are of undeniable importance
in regard to the question of physiological variability,

1 This type may be obtained either by attenuation of the highly
virulent type, or by partial revivification of the attenuated bacilli. The
latter method is certainly preferable.

130 EXPERIMENTAL EVOLUTION LECT.

as they clearly show that while no difference at all
can be discovered in the external appearance of the
different types, considerable variation is present when
physiological properties are taken notice of.

I have quoted this case at some length, because it is
one of the most satisfactory yet obtained ; but similar
instances are very numerous in bacteriology, where we
perceive that very considerable differences of a phy-
siological nature may exist although not perceptible
from the morphological standpoint.1

Zoology also provides us with other facts which are
of great interest. I refer to those which concern the
considerable physiological difference which obtains
between two closely related species, the brown and
the green frog (Rana esculenta and temporarid), when
subjected to identical experiment.

In 1 88 1 Monnier2 noticed that brucin and its
different compounds act differently on these two
species. In R. esculenta this alkaloid determines a
paralysis of the motor nerves, and at the same time
an increase in the excitability of the spinal cord. Of

1 Cf. A. Chauveau : Sur les Proprietes vaccinates de Microbes ci-devant
fiathogenes transformes en Microbes d'apparence saprogene. Archives de
Medecine Exptrimentale, March, 1889, p. 161. Also, by the same
author : Recherches sur le Transformisme en Microbiologie pathogene.
Des Limites, des Conditions ct des Consequences de la Variabilitc du
Bacillus Anthracis. Ibid. November, 1889, p. 757.

2 Archives des Sciences Physiques et Naturelles, Geneva, 1881.

in GREEN AND BROWN FROG 131

course, the influence on motor nerves prevents the
spinal influence from being detected, unless the experi-
ment is performed in a particular manner. In jR.
temporaries the symptoms are quite different ; tetanic
convulsions appear, and if the dose is considerable,
motor paralysis ensues later. The case is the same
with the common toad.

Similar facts had been witnessed years before by
many physiologists. As early as 1864 my much re-
gretted master Vulpian : found that the same poisons
operate differently on the circulatory system of the
two species. Two years afterwards J. L. Prevost 2 wit-
nessed facts confirmatory of the preceding, concerning
the same animals when subjected to the influence of
veratrin ; the heart being arrested in one case, while
it is merely slackened in the other. Then Schmie-
deberg, in i8/4,3 took up the question, studying the
influence of caffein, and saw that in R. temporaria
caffein operates in determining a local action which
gradually spreads a sort of muscular rigor, accom-
panied by a decrease in excitability ; in R. esculenta

1 Sur les Differences entre les Grenouilles rousses et les Grenouilles
vertes sous le Rapport des Effets produits par les Substances Toxiques et
sptcialement par les Poisons du cceur. Bull. Soc. Philomatique, 1864,
p. 94.

2 J. L. Prevost, Recherches Experimentales relatives a F Action de
la Veratrine. Thesis, Paris, 1886.

3 Ueber die Verschiedenheit der Caffeinwirkung an Rana temporaria
und R. esculenta. Arch. f. Exp. Path, und Pharm. 1874.

K 2

132 EXPERIMENTAL EVOLUTION LECT.

there appear, on the contrary, an increase in excita-
bility and tetanic convulsions. But after two or three
days the symptoms become similar in both species.

Pilocarpin, also, acts differently on the two above-
mentioned species, as Harnack and Meyer have
shown.1 In Rana temporaries, pilocarpin induces
paralysis ; in R. esculenta, tetanus. Nicotin induces
convulsions, followed by paralysis, in esculenta,
while- paralysis is the immediate result in temporaria.
Similarly, pyridin induces tetanus in esculenta,
and in temporaria the symptoms resemble those of
picrotoxin poisoning. L. Wintzenried has con-
firmed Monnier's results on the different influences
of brucin,2 and Vulpian,3 in a later paper,, investi-
gated the accuracy of the statements of both to his
complete satisfaction. Lastly I may be allowed to
quote a few lines from a paper by Messrs. Lauder
Brunton and Cash,4 which bears very exactly on the
topic : " Johannsen [who was working under Schmie-
deberg's direction] observed in the frogs with which he

1 Harnack and Meyer, Untersuchungen it. d. Wirkungen des fabor-
andialkaloide, nebst Bemerkungen u. d. Gruppe des Nicotins. Arch. /.
Exp. Path, und Pharm.

2 Recherches Experimentales relatives a V Action Physiologiqite de la
Rrucine. Thesis, Geneva, 1882.

3 Lemons sur V Action Physiologique des Substances Toxiques et Medica-
menteuses. 1882.

4 Lauder Brunton and J. Th. Cash, On the Circumstances which
modify the Action of Caffeine and Theine upon Voluntary Muscle.
Journal of Physiology, vol. ix. p. 112, 1888

in GREEN AND BROWN FROG 133

experimented that the muscles became rigid at the
place where caffein was injected, and this rigidity
gradually extended to the rest of the body, but he
failed to observe any tetanus. About three years
afterwards, Aubert arrived at results entirely opposed
to those of Johannsen, rinding that caffein in the
frogs with which he experimented produced marked
tetanus, but very slight rigor. These contradictory
results induced Schmiedeberg again to take up the
subject, and he found that the discrepancy be-
tween the statements of Johannsen and Aubert was,
to a great extent, due to the kind of frog employed
by each observer in his experiments, the former having
used specimens of R. temporaria, and Aubert of
R. esculenta. According to Schmiedeberg, in R. tern-
poraria caffein produces muscular rigor, without
tetanus, the rigor beginning at the place where the
poison is applied, and extending over the body so
gradually that the muscles first attacked may be
completely contracted and rigid, while others may be
still slightly irritable. On the other hand, in R.
esculenta, caffein frequently produces a violent and
continuous reflex tetanus, without any rigidity of
muscle other than that dependent on the tetanic con-
traction. It is only at a late stage of the poisoning,
two or three days after the caffein has been given, that
these differences between these two kinds of frogs

134 EXPERIMENTAL EVOLUTION LECT.

become equalised, increased reflex action and even
tetanic convulsions occurring in R. temporaria, and
distinct stiffness of the muscles becoming observable
in R. esculenta, although this stiffness never becomes
so great as in R. temporaria"

The foregoing differences in the nervous system of
these two very closely related species are again exem-
plified in other experiments, for Lautenbach1 has shown
that while the nerves of Rana temporaria are never
excited by heat lower than 49° centigrade, those of
R. esculenta are excited as soon as the temperature
attains or exceeds 20° centigrade ; and, on the other
hand, a friend of mine, M. C. Contejean, a dis-
tinguished young physiologist, informs me that,
according to his own experiments, considerable dif-
ferences are noticeable in individuals of the same
species which differ in colour. While frogs whose
skin contains numerous pigment granules withstand
for some time the effects of having part of their blood
replaced by salt solution, frogs whose skin is sparsely
coloured resist during a much shorter period. Again,
the same physiologist informs me that while Rana
esculenta and temporaria possess digestive glands in
the lining of their cesophagus, the toad has none.
Also, while the green and brown frog are provided

1 The Physiological Action of Heat. Journal of Physiology, vol. ii.

in GREEN AND BROWN FROG 135

with gastric glands which are exactly similar, the
brown certainly produces a much larger amount of
pepsin. These are differences which may be of great
importance in the life of the animals — or may go
with others yet unknown to make considerable differ-
ences— yet nothing in the external character of the
animals would lead us to suppose that they were
present.

Among the facts which illustrate this physiological
variability I shall quote a few more. We all are
acquainted with the fact that while many varieties of
grape-vine are killed by some fungus or insect — Phyl-
loxera, for instance — others do not suffer at all, or
at least, as a rule, withstand the unfavourable effects.
We know also that while the venom of a snake is
deadly for most other snakes, it is not so for the same
species, as Surgeon Waddell x has recently shown with
great care ; we have all heard of cases when the same
plant is toxic for some animals and is not so for
others. Willoughby in his Ornithologia 2 says that the
common quail eats hellebore and water-dropwort
(Cicuta] without danger ; Daniel Duncan 3 says the
same of the same animal ; water-dropwort is not
dangerous for goats, nor tobacco-leaves for oxen,

1 Are Venomous Snakes Autotoxic ? Calcutta, I

2 Francisci Willughbeii Ornithologia, Libri Hi. 1676.

3 La Chymie Naturelle^ on I Explication Chymique et Mechaniqtu de

la Nonrritnre de I Animal,

UNIVEBSITI

136 EXPERIMENTAL EVOLUTION LECT.

according to Cornevin ; common valerian, when
growing in marshes, is half or three-quarters less
toxic than when it grows in dry soil, according to
Pierlot ; 1 and Coffcea arabica is killed by insect
parasites (Cemiostoma caffeohnn] which do not attack
C. liberica?1 Physiological variability is displayed
every day among the individuals of the same pro-
geny or of the same brood. Human twins are often
very dissimilar in regard to physical and mental
abilities. Among animals, the same cluster of eggs
gives birth to tadpoles which differ considerably as to
the epoch at which the tail is cast off and the limbs
put in their appearance, although all external con-
ditions of temperature, food, etc., are exactly identical.
Among hogs, the last born of the brood is generally
much weaker than the others ; of the four or five dogs
which are generated by the same parents, no two are
alike in regard to the acuteness of the smell, swiftness,
etc. Young turkeys of the same brood differ much,
while there is but little difference between young ducks
or geese. In my experiments on Lymnaea stagnates
I have often noticed very marked differences in the
length and weight of animals from the same cluster of
eggs, although they lived together, under exactly
identical conditions, in the same aquarium. For in-

1 Note sur la Valerians. Bull. Soc. Bot. France, vol. ix. p. 189.

2 Nature, vol. xxiii. 1881, p. 541.

in PHYSIOLOGICAL VARIATION IN SEEDS 137

stance, in one case I have had animals of four or five
millimetres in length only, while some of their brethren
were over ten millimetres long, at the same age. In
another case the difference between lengths was from
three to ten, and in width from two to six. More
detailed facts concerning this point I intend to publish
shortly in a special paper, and I shall try to establish
a comparison especially between the different indi-
viduals of the same brood parthenogenetically pro-
duced, or at least produced without previous fecunda-
tion by a different animal of the same species, for it is
a positive fact that Lymncea stagnalis and auricularia
can yield fertile eggs without fertilisation by another
individual having taken place. Similar facts are to
be noticed among plants, as every one knows. Cornevin
has provided a new demonstration of the fact by sub-
jecting seeds of the same plant to the same conditions.
He took thirty seeds from the same pea-plant, and
steeped them some thirty hours in a solution of
colchicin, and then planted them. Out of the thirty,
twenty-five were entirely killed, and out of the five
which survived, only three were able to develop a
normal plant. Some years ago I had noticed similar
facts, in a different manner. Four species of seeds
were subjected to the influence of heat in the following
manner : In one series the temperature was 80° Cent.,
and the seeds remained two minutes in the heated

138 EXPERIMENTAL EVOLUTION LECT.

water ; in the second, it was 90° Cent., and the time
for heating was ten minutes ; in the third, the seeds
remained two minutes only in the water at 90° Cent.
The final result was that in the first series only one
sort of seed was able to withstand the effects of the
heat : two out of ten seeds germinated. In the
second series one seed only germinated (Lepidium
sativum}, and in the third series two species ger-
minated (cress and radish).

The same result was obtained when I planted seeds of
different sorts whichhad been subjected to the influence
of a solution of sulphate of copper in water, during a
period varying from one to sixteen days. Some species
were very sensitive, and did not germinate at all. Such
was the case with radish and mustard seed. Others
were less sensitive, and Lepidium sativum germinated
even after ten days' immersion, but then only some of
the seeds were able to germinate, and the proportion of
those that were killed increased when the duration of
the submersion was greater. Lastly, flax seed withstood
sixteen days' contact with the copper solution, but the
number of germinations was larger among the seeds
which had been immersed four or eight days only, than
among those which had remained the whole period.
More recent experiments of the same sort with
copper and strychnine have yielded the same results,
and show that : istly, great differences occur in the

in PHYSIOLOGICAL VARIATION IN SEEDS 139

sensitiveness of different species in regard to the same
reagent ; 2ndly, marked differences occur also in
regard to the sensitiveness of different individuals oi
the same species in regard to the same reagent.

I am at present engaged in repeating and develop-
ing this series of experiments, as they help to illus-
trate physiological variability, and can be used also for
investigations in selection. Of course, in many cases
the result may be interpreted as due to variation in
the thickness of the seed-envelopes, or in the bulk
of the seed itself; but whatever the cause of the
differences in resistance may be, the main point is
to demonstrate palpable variations, that is, a firm
basis for the operation of selection ; and, on the other
hand, the differences in thickness of the seed-en-
velopes is not a mere anatomical fact, it is also a
physiological character of the plant.

Observation has, however, already provided very
interesting facts bearing upon this question of physio-
logical variability in regard to the influence of poison.
We know that this influence varies according to many
conditions, among which are the following : —

First, the mode of introduction, — Many poisons are
devoid of danger when introduced through the ali-
mentary tract, while they are very dangerous when
introduced into the blood or under the skin, because
in the first case they are slowly absorbed or are

HO EXPERIMENTAL EVOLUTION LECT.

destroyed by their passage through the liver for
instance.

Secondly, the age of tJie animal under experiment. —
This is easily ascertained, and the fact is recognised
in medical practice, where the dose of the same drug
varies from one-sixteenth to one, according as it is
given to a young child or to an adult.

Thirdly, sex. — Females are more sensitive than
males, and accordingly are unable to withstand doses
of drugs or poisons which males resist.

Fourthly, species. — Belladonna is very active on
man, cat, dog, and birds ; less so on horses and hogs ;
nearly without effect upon sheep and goats, and
especially on rabbits. Within the same class the
same differences obtain ; the rat is, generally
speaking, more sensitive than the guinea-pig,
and the rabbit is less so than the latter ; and the
ass is more sensitive than the mule and the horse.
Hemlock (Conium macnlatuni} is not injurious for the
lark and quail ; although they may eat so much of it
that their flesh may be poisonous for Carnivora, they
themselves sustain no injury. The red corn poppy is
not injurious for rabbits, and it is said that Euphorbia
may be eaten without inconvenience by goats, although
it confers toxic properties on their milk. Laburnum
is not toxic for goats, rabbits, and hares. Within the
same species, marked differences obtain between

in FOOD AND POISON 141

varieties. The Pyrenean sheep feed without injurious
effects on the leaves of Quercus tosa, while imported
Southdovvns are killed by this plant. Lychnis Githago
is very unequally toxic for different species ; calves
require 2 g. 50 centigr. per kilogram of weight of
flour, while the hog requires only one gramme, and
the dog ninety centigrammes, to be killed. Similarly,
while the horse is killed by two kilograms of fresh
hemlock, the ox requires at least double this amount.
Cyclamen europceum is very dangerous for man, and
hardly at all for hogs ; it kills fishes and some other
aquatic animals, while many Crustacea and different
insect larvae do not suffer at all.

Of course, there are many reasons for these dif-
ferences in the influence of poisons, and in some cases
we perceive them easily. But in others there is some
intimate unknown reason which would require investi-
gation, such as the case of the Pyrenean and South-
down sheep. Even if there is merely here a case of
habitual adaptation — a mere verbal explanation —
such as is very often met with in experiments on the
influence of toxic media on animals or plants, or on
the influence of pathogenetic organisms on higher
beings, there must be some difference between the
organisms which perfected methods will be able to
detect. There may be here some acquired character,
some peculiar variation which has become inherited.

142 EXPERIMENTAL EVOLUTION LECT.

On the other hand, turning to plants, similar facts
of physiological or chemical variation are noticeable.
The same plant is more or less toxic, according to its
age or period of life, and to the various parts con-
sidered. While some plants are toxic in all their
parts, such as meadow saffron (Colchiciim autummale)
hellebore, squill (Scilla maritime), Pride of India {Melia
azcdaracli], others are dangerous only in their roots,
such as Atractylis gemmifera, or in their roots and
stem, such as the common dog violet ; or in their
aerial parts only, such as many Solanaceae ; or in
their bark and leaves only, as is the case with the
yew ; or in their flowers, as buckwheat (Polygonum
fagopyrum) ; or in their fruits only, as, for instance,
in the castor oil plant ; or even in one part only of
their fruits. Other plants are dangerous in all their
parts save one, the fruit for instance in sumach (R/ius
coriaria).

Young leaves of the yew are much less toxic than
aged ones, which is the reverse of the case generally
observed. Clematis vitalba displays the same fact.
Ranunculus ficaria, while at first feebly toxic (through
its leaves), becomes afterwards more so, but after
flowering it loses much of its poisonousness, and the
same is the case with Caltha palustris. Aconitum
napellus is very toxic in warm climates, while in
the northern or cold regions it is harmless ; culti-

in TWO CLASSES OF SPECIFIC CHARACTERS 143

vation also diminishes its injurious properties in a
marked manner. Of course, these differences in the
physiological influence of the same plant can only be
ascribed to variations in the protoplasmic or physio-
logical processes of the plant, so that they afford
very good instances of physiological variation. These
are a few instances among many ; but they are enough.
We may then draw the inference that between
different species there are not only external dif-
ferences which may seem more or less unimportant
— although we must believe them to have some use-
fulness— there are also other differences of a physio-
logical nature. As yet we are acquainted with but
a few of them, the matter having been but very
slightly investigated, but we may rest assured that
in fact they are numerous, and often very consider-
able. While they may seem, and perhaps are, in
many circumstances of small importance, they may,
in others, become of the highest interest, and de-
termine life or death. This is the main fact I wish
to illustrate, and I entertain no doubt whatever
concerning the novel, and certainly startling, character
of the results, which will be put forward when some
competent physiologist and chemist shall have devoted
some time to the comparative investigation of two
species, or better of two varieties of the same species,
from this point of view.

144 EXPERIMENTAL EVOLUTION LECT.

With chemical investigation such as Armand
Gautier's, and physiological experiments such as
those which Vulpian originated, a great deal must
certainly be discovered, and herein lies a new way
to the investigation of the much debated question
of variability. Even if it does not lead us any
further, this line of study must bring us to this
much needed requisite : an answer to the oft-
repeated question, What is a species ? Species,
we are always answered, are endowed with such
and such characters, and when we come to look
at matters, we find out that two forms — say of
Crustaceans or Rotifers — are considered as speci-
fically distinct because the one has a few hairs
more than the other on this or that appendage,
or because the form of such or such part is more
elongated in one group and rather square in the
other. This answer is doubtless very satisfactory,
since so many are amply satisfied — or seem to be
so — with it ; but in future we shall certainly come
to define species not only by means of their external
anatomical characters, but also in terms of a large
number of physiological and chemical differences
which have hitherto been entirely disregarded, which
are but slightly apparent, and can be made quite
clear only by means of careful and methodical in-
vestigation with appropriate methods : to the mor-

in TARCHANOFF'S EXPERIMENTS 145

phological diagnosis, a chemico-physiological diag-
nosis shall be added, whose importance shall often, if
not always, be much greater than that of the former.

As I have dwelt at some length on the topic, I
might be expected now to dismiss it, after having
shown that variation is to be found in every part of the
organism, even in its deepest and most secluded nooks ;
but there arc still some important matters to be dis-
cussed. Concerning physiological variability, many
experiments might be suggested, and some have
been made which show that physiological variations
may be experimentally induced. Professor Jean de
Tarchanoff,1 investigating the physiological condition
of the brain of new-born animals, has shown that this
part of the nervous system does not at birth answer
with the normal activity to external stimulations.
While Fritsch and Hitzig, afterwards followed by
Ferrier and a number of physiologists, established the
fact that stimulation of certain parts of the mid-brain
is followed by motor reactions in various parts of the
body, Tarchanoff has shown that during the first days
of life, and especially among the animals which enter
upon life with closed eyelids, no motor reaction at all
is produced. This is an important feature from the

1 Sur les Centres Psycho-moteurs des Animaux notiveau-nes et leur
Develop f>euient dans differentes Conditions. Rev. Mensuelle de Mede-
cine et de Chirurgie, 1878.

L

I46 EXPERIMENTAL EVOLUTION LECT.

stand-point of physiological variability ; but there is
something more that Professor de Tarchanoff has seen
and proved. The brain of the new-born guinea-pig,
for instance, does not answer to electrical stimulation
during the first days doubtless because it is not yet
developed enough. If it could be artificially developed
or retarded in its growth and progress, it is likely that
the moment at which electrical excitability exists
could be hastened or retarded, and that, similarly, the
moment at which the eyes open could be at will
hastened or retarded. Methods are not wanting to
allow the performance of the experiment, and
Professor de Tarchanoff has artificially hastened the
development by means of some phosphorus mixed
with the food, and by means of cerebral hyperaemia in-
duced by occasionally hanging the animals head down-
wards, while the reverse position and a slight degree
of alcoholism have been enough to render cerebral
development much slower. The result was exactly
what might have been expected ; when the develop-
ment is retarded, excitability and sight are retarded,
and another fact is noticeable : locomotion is also more
difficult and is attained later, because the causes which
retard the cerebral development inhibit more or less
all functions which are dependent upon the brain.
Professor de Tarchanoff thinks that it might be
possible, by repeating the same experiments on the

in VARIATION UNIVERSAL 147

successive generations, to hasten or to retard in a
marked manner the nervous development. This may
be : at all events the facts are interesting, and show
that methods may be devised through which an in-
fluence may be exerted on constitutional peculiarities.
Such facts give us hopes of seeing where the cause of
physiological variability may be sought.

To all that has been said concerning variability,
morphological and physiological, we must add that
this variability is not limited to any group of plants or
animals, to any time of life, nor to any geological epoch.
From the very beginning of life variation is apparent.
Take a number of eggs of the same frog, in conditions
apparently identical : some are early and some late in
developing into tadpoles. Tadpoles acquire their
limbs and lose their tail at very different intervals,
although all live in the same aquarium, are born from
the same parents, and enjoy the same food ; and if you
put some of them into the same toxic solution, some
are certain to die much earlier than the others, and if
the time during which they remain in the dangerous
medium is not too long, some certainly will recover,
while the others die. Of the whole progeny of the same
parents, whether two or two hundred young are pro-
duced at one time, no two are exactly alike : noticeable
differences exist, if not in the external, certainly at

L 2

148 EXPERIMENTAL EVOLUTION LECT.

least in the physiological characters. Of the same
brood of pigs the last born is generally weaker ; of
twin lambs one is always heavier, etc. And if any two
animals of the same brood are selected and observed
in after-life in order to estimate the differences
between them in physiological respects, although
they live under exactly similar conditions, consider-
able differences appear in their weight, height, etc.
It is enough to note these facts, without dwelling any
longer on the topic. But while variability exists
everywhere, in every species, in every individual, it
must be also admitted that its sum total is very
variable. Some species are much more liable to
variation than others, as all horticulturists can testify.
But, in fact, truth seems to require another statement.
All species are probably equally variable, but all are
not at the same time in conditions which are equally
suitable for the production of variation. Take the
case of any imported species of plants which is
cultivated in our European gardens. At first no
variability is apparent, and many horticulturists give
up the hope of improving or of modifying it in any
way. But those who have more experience go on
with their plant, knowing very well that while at
first no marked variability appears, very important
variations may suddenly appear at a later stage, after
cultivation has been continued for some time. Such

in VARIATION UNIVERSAL 149

has been the case with the common pansy, as Weis-
mann has noticed, and it often happens that the
foreign species, after keeping very constant for some
years, begins all of a sudden to vary considerably and
in many directions, thus giving birth to an unexpected
number of varieties. These facts must be kept in mind,
and they go to show that one must not be hasty in
deciding whether any species is or is not liable to vary
more or less than another : variability is doubtless
itself variable, according to influences of which we are
more or less ignorant. Palaeontological facts are
known which are of value in that they show that
variability has existed in the past as well as in present
times, and that it has been more apparent in some
species or genera than in others. Mr. Hyatt provides
a good instance of such facts, in his paper on the
Steinheim fauna,1 where a large number of fossil
varieties of Planorbis are met, all of which most
probably descend from four principal varieties of one
single species, P. laevis, unless we prefer to believe that
every single one of these principal or secondary
varieties has been called into existence by an equal
number of special creations. H. Filhol has also given
valuable facts bearing on this matter, in his investiga-

1 See The Genesis of the Tertiary Species of Planorbis at Steinheim
(Bost. Soc. Nat. Hist. 1880), and Transformations of Planorbis at
Steinheim (Am. Naturalist, 1882, p. 441.) Cf. also Stearns, Proc.
Acad. Nat. Sc., Philadelphia, 1881.

150 EXPERIMENTAL EVOLUTION LECT.

tions concerning the fauna of the Quercy phosphorites.
For instance, he shows that at St. Gerand le Puy,
Amphicyon, that presumed ancestor of our dog, has
a great tendency to vary in height, strength, form of
the head, and in the teeth, while a number of other
genera exhibit the same tendency in all the parts of
the body : such are Palaeot her turn y EurytJiermm,
Acerotheriuni) Palaeocliaerus, Cynodictis, Hyaenodon,
Cynohyaenodon, Achirogalus, Necrolemur, Adapts,
Psendelurus, etc. ; and so far as dimensions are con-
cerned adult fossil remains are often met which
indicate that the differences were often from one to
two. Nor can all these differences be explained as
of mere age or sex.

As I have already noticed, we know nothing of the
causes of variability. We can measure and appreciate
it to some extent, but we do not know how it is
determined in most cases, save in those where it is
consequent upon some modification in external
environment, and to these we shall have to revert
further on. Must we believe in some innate " tendency
towards variation " ? Buffon thought that every species
tends towards degeneracy, while Lucas believed in
some innate tendency towards the production of new
forms, which is, of course, in constant warfare with
conservative heredity. Naudin and Naegeli similarly
believe in internal forces, and Delbceuf, the eminent

in SUDDEN VARIATION 151

Belgian thinker, clearly expresses himself in favour of
the belief in a " tendency to betterment," some per-
manent cause with an unlimited aim, which will
operate as long as our planet lasts, and as long as
something may be imagined which is more perfect
than that which exists. Clearly such a tendency is
undemonstrable. For even if things could be seen
to progress as they ought if this tendency exists, this
is no proof of the existence of the tendency.

On the other hand, many naturalists appeal to
external influences in order to explain variation, and
they certainly can point to many facts which are of
weight, as we shall show further on. Conditions
which seem, at first sight, to have no importance,
often exert considerable influence on individuals or
groups of individuals. But a discussion of this matter
would require more time than can be afforded here,
and I must dismiss the subject after having briefly
stated the state of opinion concerning the cause of
variation. I only wish to add that while, in the earlier
period of Darwinism, much stress was laid on the
slowness with which variation appears and operates,
there is at present a tendency to a change of opinion.
This change has been well expressed in a recent paper
by W. H. Dall, On a Provisional Hypothesis of Saltatory
Evolution! The writer bases his argument on the oft-

1 In this connection Mivart's Genesis of Species may also be cited.

152 EXPERIMENTAL EVOLUTION LECT.

repeated fact that in many cases while two forms of
life, fossil and extant for instance, seem to be directly
or genetically related to each other, some link seems
to be missing through which the transition from the
one to the other could be effected. In Mr. Ball's
opinion no links are really missing in such cases,
because none have existed ; the much asked for
transitional forms have never lived. He supposes
that sudden and considerable variation may take
place under the cumulative influence of a number of
small causes which remain a long time inoperative,
but become efficient when at last one more slight in-
fluence is added, which acts like the straw that breaks
the camel's back. A good deal may be said in favour
of this view, and many facts from zoology and
palaeontology go to support it, and it may be that
there is more truth in this manner of explaining
some facts than in the former opinion. At all
events abrupt or sudden variation is not an un-
known fact. Some years ago, in France, a variety
which stands between Begonia Schmidtii and B.
semperflorens made its appearance quite suddenly in
different points at the same time ; at Paris, at
Poitiers, at Lyons, at Marseilles, etc. At Lyons the
fact was very striking, as 500 specimens of the plant
suddenly exhibited the new characters, and these
characters were found in a plant which had been a

ITI SUDDEN VARIATION 153

year previously isolated in order to prevent hybridisa-
tion.1 A year later, a similar fact was observed by
another horticulturist when all of a sudden a large
number of plants of Narcissus} which had met with
adverse circumstances and had required some quan-
tity of chemical manure, began to bear double
flowers.

Among animals, sudden variation is not uncommon,
mainly through the disappearance of some external
characters. In Paraguay, during the last century
(1770), a bull was born without horns, although his
ancestry was well provided with these appendages,
and his progeny was also hornless although at first
he was mated with horned cows. If the horned and
the hornless forms were met in fossil state, we would
certainly wonder at not finding specimens provided
with semi-degenerated horns, and representing the
link between both, and if we were told that the horn-
less variety may have arisen suddenly we should not
believe it, and we should be wrong. In South America
also, between the sixteenth and eighteenth centuries,
the Niata 3 breed of oxen sprang into life, and this

1 Cf. A. Carriere, Spontaneite simultanee. Rev. Horticole, 1882,

P- 534-

2 M. Poulin, Particular ites Vegetahs. Ibid. 1883, p. 342.

3 Niatas are occasionally met with in Europe, and many are living at
present. They are descendants of common cattle and sheep, and no
particular reason for their peculiarity is offered. This sort of variation
thus seems to be common.

154 EXPERIMENTAL EVOLUTION LECT.

breed of bull-dog oxen has thriven and become a new
race. So in the San Paulo province of Brazil a new
breed of oxen suddenly appeared which is provided
with truly enormous horns, the breed of Franqueiros,
as they are called. The Mauchamp breed of sheep
owes its origin to a single lamb which was born in
1828 from merino parents, but whose wool, instead of
being curly like that of its parents, remained quite
smooth. This sudden variation is often met with,
and in France has been noticed in different herds.

Other cases of the same sort might be quoted,
showing that, as some naturalists feel inclined to
believe, sudden variation is much less uncommon
than has been generally supposed.

Having dealt at some length with the facts con-
cerning variability, we may briefly sum them up in
the statement that a certain degree of variability is
met with in every species, fossil or existing, animal or
vegetable, and that this variability is not found merely
in external characters, and does not affect only the
colour, dimensions, or integumentary appendages, but
that it extends also to the most deeply seated parts
such as the viscera and bones of animals, and reaches
even further, since physiological variability is merely
the external expression of physical and chemical
variations in the most intricate recesses of the various
parts which make up the organism.

in SUDDEN VARIATION 155

Here ends the first group of facts which lie at the
basis of experimental transformism, the facts of varia-
bility in the state of nature. We may now proceed to
examine the second group, that of the facts of
variability under domestication and culture.

LECTURE IV

Summary. — Second Group of Facts supporting Experimental Evolution ;
Fadts of Domestication of Animals ; their Departure from the
original Wild Type as seen in the cases where the latter still exists ;
Much more might be done in this way, and many new
Resources discovered ; Domestication has caused Animals to vary
in all parts of their Organism, from Weight of Brain to Length of
Digestive Tract. Third Group of Facts : Cultivation of Plants ;
its Influence ; the Departure from the original Wild Type ; Varia-
tion in all parts of the Plants from Roots to Flowers ; Numerous
Varieties of the commonly-cultivated Vegetables. Fourth Group
of Facts : Influence of Environment on Structure ; Closeness of
Agreement between Environment and Organism ; Beudant and
Raulin's Experiments ; the Author's Experiments ; Dareste and
Teratogeny ; Pouchet, Yung ; Facts and Experiments ; Pierre
Lesage ; Schmankevitsch ; Weismann's Criticisms.

WE positively know that some of our domestic
animals and cultivated plants were companions of
prehistoric man. It even seems that among the
older nations, now dead and gone, some animals
were subjected to domestication which have since
been totally abandoned and allowed to run wild. The
beech-marten and other Mustelidae were in part
domesticated by the ancient Greeks in order to

LECT. iv NUMBER OF DOMESTIC ANIMALS 157

destroy rats, and in ancient Egypt Lycaon pictus, a
wolf, was tamed, and during a long period made use
of as a dog. Similarly the jackal and lion were
tamed and used for hunting purposes, and many
species of antelopes were domesticated, being shut
up at night in stables, while during the day shepherds
led them about like ours with cows or sheep. But
the domestication of these various species was soon
abandoned, for while we notice these pictures in
many sepulchral monuments of the earlier periods,
they are no more to be seen in those of the more
recent epochs, these animals having doubtless been
superseded by others more useful and more easily
tamed.

If we call domestic those animals which remain
voluntarily in man's dependence, while being of special
use to him, we perceive that their number is very
small. Excluding, of course, animals such as oysters,
clams, bees, silkworms, trout, salmon, and the fishes
which are the object of the pisciculturist's attention,
domestic animals are wholly comprised in two classes
those of mammals and birds. Among the birds we
have the ostrich, swan, goose, duck, turkey, pheas-
ant, peacock, guinea-fowl, common fowl, and pigeon.
Among mammals : guinea-pig, rabbit, cat, dog, hog,
horse, llama, camel, reindeer, sheep, buffalo, and ox,
and partly also the elephant. If to these twenty-three

158 EXPERIMENTAL EVOLUTION LECT.

species we add some fifteen or eighteen species which
are more or less domesticated by the inhabitants of
other parts of the world, we obtain a sum total of
some forty, let us say fifty species.

The wild forms of these domestic species are
nearly all known and living. The two genera of
ostriches, found in Africa and America, are among the
most recently domesticated forms, and in fact have
been domesticated only to a slight extent. Wild
swans are yet found in Sweden and Norway ; geese
are met in Asia and Europe ; ducks are found in the
greater part of Europe ; the turkey is an inhabitant
of the New World, whence it was imported but a few
centuries ago ; pheasants — but yet partly domesticated
— live wild in Central Asia ; the guinea-fowl has been
found wild in Africa by De Brazza ; the peacock
inhabits India, Java, and Sumatra ; the common fowl
is the descendant of the Indian Callus Bankiva ; the
rock-pigeon is the ancestor of all our varieties of
domestic pigeon.

However, wild guinea-pigs are no longer found in
South America, where they existed some centuries
ago ; and of our hog only doubtful ancestors exist in
Asia and the Sunda Islands (Sus vittatus and papu-
ensis). Wild horses most probably still exist. Pliny,
Varro, Strabo mention them, and Erasmus Stella
and Rosslin speak of wild horses in 1518 and

iv WILD AND DOMESTIC FORMS 159

1593 'm Prussia and Alsace, while Gaspard de
Saunier mentions their existence in 1711 in the
forests between Dusseldorf and Wosel, where he
had hunted this animal. And a few years ago the
celebrated Russian explorer, Prjevalsky, discovered
in Dzungaria a wild species, which has been named
Equus Prjevalskii, and which seems to occupy a
place between the horse and the ass. Wild asses
have been seen by Prjevalsky in Kokonor, and by
others in Africa, near Obock. In Egypt Marco
Polo and Pallas found the wild camel, which, nearer
us, Prjevalsky discovered near Lake Lob-nor. The
wild form of the llama seems to be the guanaco ;
the American caribou seems to be the wild form of
the reindeer, and the Asiatic moufflon (Ovibos musi-
mon) is considered as the wild form of our sheep,
while wild goats are found in the Himalaya, buffaloes
in Asia and Africa, and the yak in Asia, and oxen
in Africa only, as they have now disappeared in the
wild state from Europe and Asia, where they for-
merly existed. Some points are, however, doubtful.
Concerning the sheep, we cannot exactly tell whether
our domestic form is derived from any one of the
present wild forms or from the crossing of two or
more, or from an extinct species ; and as to horses,
while they were very abundant in the wild state
during the neolithic period, when they were used as

160 EXPERIMENTAL EVOLUTION LECT.

food by prehistoric man, yet we cannot tell exactly
whether our horses are derived from these wild
ancestors, nor whether the descendants of the neo-
lithic horse really persisted till some two or three
centuries ago.

Of our present domestic animals, most have been
domesticated for a very long time, and while we feel
assured that domestication is merely a matter of time
and patience, we wonder at the fact that civilised man
has been content to accept the legacy of his savage
ancestors, and has done so little to increase it. At
the present time man, in the civilised state, does not
possess more than some twenty species of birds and
some twenty of mammals in the domesticated state.
It is true these species meet most of his requirements ;
but who would venture to say that there is not much
profit in store for him if he were to increase the number
of his domestic friends ? While man in all parts of the
earth is — or ought to be — eager to discover new vege-
tables, or at least new fruits, and to cultivate and export
them, how is it that our animal resources remain so very
few in number ? I do not explain the fact, but merely
call attention to it, and many, I hope, will concur
with me, and think that much might be done in the
way of acclimatising useful animals — useful as meat
or milk-givers or wool-producers — of domesticating
them, and of discovering new resources from which

iv DOMESTICATION MUST ADVANCE 161

mankind may derive many benefits. Our acclimatisa-
tion societies do not yet understand the real aim they
ought to pursue, and they are much more occupied
with the pursuit of new or rare animals, which are
seldom of any use, than in that of the useful species
which certainly exist. We cannot believe that our
present domestic animals are the only ones which can
be of use to us ; there are many others which may
be profitable, but instead of trying to domesticate
these, we often wantonly destroy them. Such is the
case at present with the American bison, which com-
petent writers state to be an excellent flesh-producer.
While it roamed in millions some years ago, not
300 could be found to-day on the whole surface of
the earth. I do not wish to open here a chapter
recording the foolish and cruel dealings of so-called
civilised man — the real civilised man occurs in infi-
nitesimal proportion among the featherless bipeds —
with animals, for a whole book would not suffice, but
whoever is acquainted with the facts cannot help
regretting this stupid and sinful waste.1

Revenons a nos moutons. Domesticated animals are
few in number. There are good reasons, however, apart
from that which has been already given, for this fact.

1 For interesting details as to domestication of animals in India, see
J. Lockwood Kiplings's recent volume, Man and Beast in India.
Lond. 1891.

M

162 EXPERIMENTAL EVOLUTION LECT-

As Cornevin l remarks, some essential conditions must
be fulfilled before any species can be domesticated.
The principal requirements are the following :—

First, Sociability. — All domestic animals, as observa-
tion at once shows, live in societies, in herds — all, save
one, the cat ; the much-abused cat, the much-praised
cat, the most independent and self-centred of our
domestic friends. This gregariousness of all our do-
mestic mammals and birds, pigeon or fowl, hog or
ox, shows that if we are to attempt new domestica-
tions we must direct our attention towards gregarious
animals.

Secondly, Tameness. — Only docile animals can be
domesticated, and all animals cannot be tamed with
the same facility. Some retain a very considerable
element of savageness, whatever care may be taken
to tame them. Tameness is the result of kind treat-
ment, and of the habit of being constantly with man,
and while some species seem untamable, the greater
proportion may be more or less tamed.

Thirdly, Preservation of Fertility. — Many animals,
even in their own country, become sterile under
domestication or captivity ; they have no progeny,
or but a very small one. It also often happens
that the transfer to a new country induces temporary
decrease of fertility. The common fowl when intro-

1 Traite de Zoolechnie generate, 1891.

iv CONDITIONS OF DOMESTICATION 163

duced into Colombia was at first nearly sterile ; but
this condition does not last in most cases. It is
useless to try to domesticate animals which do not
multiply under domestication or captivity ; for even if
acquired characters are in general not inherited, it
is certainly true that the progeny of a wild species
is much more difficult to tame and domesticate
than that of the same species in the domestic state.
And if this hereditary transmission of the acquired
character of tameness did not exist, domestication
would prove impossible. In fact, domestication may
be more or less complete ; while some animals can
hardly revert to the wild condition, in many others
domestication has not existed long enough to dispel
all natural tendencies towards wild life. Such is the
case with the llama, the reindeer, the rabbit, goose,
duck, and some others, and many instances might be
given. Cornevin, for instance, has seen a flock of
geese, which for over thirty years had lived in the
same yard, arise in the air on seeing a flock of wild
geese overhead, join them, and fly away for ever.

The foregoing conditions must be fulfilled when the
domestication of any species is contemplated, and we
know enough of many animals to be assured that the
number of our domesticated species might be easily
increased if we only took some care.

As I have already said, the domestication of animals

M 2

1 64 EXPERIMENTAL EVOLUTION LECT.

has been the work of man. The study of the pre-
historic vestiges of our ancestors shows that domestica-
tion began at different times in different localities.
Up to the palaeolithic epoch, man possessed no
domestic animals. He hunted and killed the reindeer,
aurochs, and horse, but ate them instead of domes-
ticating them. In the Solutre encampment vestiges
have been found of over 40,000 horses ; but all the
bones are broken and shattered, the animals have been
killed by the hunters and immediately eaten, and the
flint arrow-heads have been found embedded in the
bones, showing beyond doubt what use was made of
the horse by palaeolithic man. It is only during the
neolithic period that domestication began. The dog
was one of the animals first domesticated, and he was
already in use during the Kitchenmidden period.
The domestication of other animals followed at very
irregular intervals and in very different countries, and
it is nearly impossible as yet to ascertain exactly at
what period or epoch our domesticated animals
entered upon their present condition. In fact it
matters little, the principal point of interest for us
being that the domestication of animals has been the
work of man. This is sufficiently proved by all ascer-
tained facts.

The next and most important point is that domes-
tication has been a means of transmutation. The

IV ALTERATIONS THROUGH DOMESTICATION 165

species which have been domesticated have gra-
dually departed from the feral ancestral type, and
among the domestic descendants man has, by his
industry and through the use of methods which he
has discovered, established different types. It matters
little from our point of view whether the ancestral form
of our horse was one or many, for if many, they at all
events had doubtless one common ancestral form, and
we may consider all our present types and varieties of
any one species as having, in each case, one single an-
cestral form from which, as we see, they have con-
siderably and in manifold ways departed. Compare,
for instance, the Shetland pony, the racehorse, and
the heavy clrayhorsc of the north of France ; compare
the numerous and very different breeds of sheep, of
oxen, of hogs, of dogs, so useful in different ways. In
some cases the wild form has disappeared, and in
those where it yet exists we perceive to what extent
domestication has modified and transformed the de-
scendants of the original stock. Whatever may have
been the ancestor of our dogs, the differences the exist-
ing breeds exhibit are marked enough to illustrate our
thesis.

The modifying influence of domestication makes
itself felt in all parts of the organism, even in its depths
and in its less external characters. For instance, if
we measure the skull-capacity of wild and domestic

1 66 EXPERIMENTAL EVOLUTION LECT.

forms, we find, as Cornevin has well shown, a marked
difference in favour of the former.

Animals. Skull-capacity. Difference in favour

of Wild Form.

Wild Ass of Persia 521 )

Domestic „ 45O j cubic centimetres 71

Abyssinian Ox 479 \

Domestic African Ox ... 432) " " 47

Moufflon 240 }

Sheep 122 j>

Boar (Europe) 190 )

Hog 177 f "

Cochin China Boar 162^

Stis mttatus 181 > „ „

Domestic Chinese Pig ... i5oJ

Wolf 142!

Dog ii6/ "

Jackal 82 "I

Italian Greyhound 76) "

Wild Rabbit 9-4^

Tame Rabbit 7-5]" "

At the same time wild animals have heavier brains
than the domestic forms. Domestic animals are also
heavier and more fleshy, and the tendency towards
flesh-production increases with domestication. At
the present day our oxen are three times heavier than
the same animals, at the same age, four or five centu-
ries ago. In France, since the beginning of the
century, oxen have more than doubled their weight ;
in 1808 the average was 300 kilograms, now it is 700.
Domestication also reacts on the length of gestation,

iv ALTERATIONS THROUGH DOMESTICATION 167

and even among domesticated animals, compared with
one another, there are marked differences.

Cornevin shows that this period in the cow varies
in length from 288 to 277 days, a difference of eleven
days. The following table gives details : —

Cows. Length of Gestation, in days.

Schwytz 28875

Freiburg 287*50

Auvergne 286

Tarentese 282

Flemish 280

Durham 280

Valais 279-65

Jersey 279-40

Ayr 279

Dutch 279

Breton 277

The same is observed among sheep, according to
Nathusius and others.

Merino 150*3

Southdown 144*2

Southdown Merino 146*3

| Southdown I45'5

£ Southdown 144*2

It seems useless to do more than point to the
modifying influence of domestication. While we must
assume that domestic animals were not specially
created for man, and that, as palaeontology, zoology,
and anthropology show, they have been evolved by

i68 EXPERIMENTAL EVOLUTION LECT.

man himself out of wild existing species which in
some cases are yet living in the feral state, the mere
comparison between the different types which have
been evolved out of the original stock, at different
times — not always very remote — is enough to show
the influence of domestication. I may add that the
divergence might have been even more marked.
For we must remember that man has always had in
view his own profit, excluding all other considerations ;
the selection which he has consciously or uncon-
sciously performed has always been directed along
the same lines ; and all variations which were of no
direct and positive use to him have been swamped.
This is well displayed by the cases in which man has
been less subservient to utility ; in pigeons, for in-
stance, where the production of new types or varieties
has been the business of amateurs and dilettanti who
pursued no particular useful object, but merely wished
to obtain the greatest number of variations, there arc
more different types than among other species of
which only a small number of useful characters —
useful to man, not to the animal itself — arc required,
all other characters being considered useless and un-
interesting, and therefore neglected, the result being
that the variations are swamped by intercrossing.
As Geoffroy Saint Hilaire1 observed, there is a
1 Histoire Natnrelle generate des Regnes Organiques,\o\. iii., p. 133

iv DOMESTICATION AND CIVILIZATION 169

definite relation between the degree of civilisation in
man and the condition of his domestic animals.
Many savages at the present time are yet devoid of
domestic animals, although they possess hunting and
fishing implements, and have even some cultivated
plants. " Where man is much civilised, domestic
animals are varied, either as species or as races of the
same species ; and among races many exist which
differ greatly from one another and depart greatly
from the original type. On the contrary where man
is himself not far removed from the wild condition,
his animals are also very near to the feral state ; his
woolless sheep is nearly a moufflon, his hog resembles
a boar, his dog itself is no more than a tame jackal,
and so on with the others if he possesses any more."

I think none will dispute the accuracy of this state-
ment.

Some animals have, from the Cambrian to the Qua-
ternary epoch, varied but in a very slight degree, such
as Nautilus, and some fossil forms which lived in
cretaceous times, are yet living in the depths of the
present seas. Generally speaking, according to Gaudry
and Lyell, the group of molluscs is less variable than
that of mammals, and among molluscs Gasteropods
vary more than Lamellibranchs, and among Gastero-
pods, Siphonostomata have varied more than Holo-
stomata. Among mammals, Artiodactyls and Perisso-

170 EXPERIMENTAL EVOLUTION LECT.

dactyls afford good illustrations of the variability of
the group, and the number of fossil forms discovered
in the Tertiary strata is very considerable. Among
domestic animals there are very different degrees of
variability ; Cornevin gives the following list of
domestic birds and mammals, where the animals are
arranged according to the order of decreasing varia-
bility :— •

Pigeon. Hogs.

Fowl. Dogs.

Duck. Oxen.

Pheasant. Sheep.

Goose. Rabbits.

Guinea-fowl. Hares.

Peacock. Donkeys.

Swan. Camels.

Turkey. Goats.

Barbary Ducks. Guinea-pigs.

Of these species, three which vary but very slightly
(turkey, Barbary ducks, and guinea-pigs) are recent
importations and will perhaps vary more in later
periods. At all events guinea-pigs have already
sufficiently varied to have become infertile with their
original stock.

The modifying influence of domestication on ani-
mals has a parallel in the influence of cultivation on
plants, and to these we must now turn, to call atten-
tion to the important transformations which wild

iv CULTIVATION 171

plants have undergone under cultivation at the hands
of mankind.

Man seems to have cultivated plants before he
domesticated animals, in some cases at least. In the
lake-dwellings of Lagozza, in Italy, belonging to the
neolithic epoch, while flints, terra-cotta ware, and even
crude linen are found, no bones are seen at all ; it
would seem that the inhabitants were strict vegetarians^
and wheat, acorns, nuts, apples, and other vegetable
products have been discovered, carefully stored away.
The people who lived there, ages ago, were already
well advanced — comparatively speaking — in agricul-
ture, before they began domesticating, or perhaps
even eating animals. But in other cases man seems
to have begun with animal domestication before he
cultivated plants. He began with the cultivation
of the species which were abundant in his familiar
haunts, and were of considerable use to him in one
way or another, especially as food for himself or for his
animals. Has he paid more attention to vegetable
food, or is some other reason to be called for ? At all
events, the number of plants which are cultivated in
the different parts of the earth is much larger than
that of domesticated animals. Truly, cultivation is
an easier process than domestication, and while the
latter is always attended with many difficulties, the
former requires less care. In all parts of the world

172 EXPERIMENTAL EVOLUTION LECT.

some vegetable species are predominantly cultivated :
in India rice, in Europe wheat, in Oceania the taro-
plant, and so on. And while little more than nothing is
done at the present time to increase our animal re-
sources, much is being done every day to cultivate
new plants, for food, pleasure, or drugs. But more
remains also to be performed, and I doubt whether
the hundred or more species which Sir Joseph Hooker
pointed out in his Flora Tasmania as being suitable
for cultivation, have all been added to those which have
been known to mankind since the long-past ages when
agriculture began to be evolved. Four centuries have
now elapsed since the American continents were dis-
covered : how many species have been added to those
which were already under cultivation ? Some forty
species, among which, it is true, we must include the
potato, arrow-root, cinchona, tobacco, tomato, pine-
apple, indian-corn ; but are there not many more
which it would prove beneficial to cultivate ? But
this is the business of the future, and ours is with the
past.1 Many of our cultivated plants differ but

1 While thus advocating the necessity of turning to a better account
the numerous plants which exist and may be, by cultivation, made very
profitable to man in one way or another, I perceive that Prof. G. L.
Goodale was addressing the American Association for the Advancement
of Science on the same topic at the same time. I will merely refer
the reader to his very interesting paper published in the American
Journal of Science, under the heading : Useful Plants of the Future.
Some of the Possibilities of Economic Botany (pp. 271-303), where

iv WILD AND CULTIVATED TYPES 173

slightly from their wild congeners, especially when
we consider plants which have been cultivated only
within recent times. De Candolle 1 shows that out of
247 cultivated species, 169 have enough resemblance
to some wild species to allow us to trace with exact-
ness their origin in the latter. In five cases there is
room for doubt ; in four, the cultivated species although
unlike the wild one is not different enough to
prevent us from tracing its origin ; in fifteen the
differences are greater, and the question remains open
whether there are here distinct species or mere
varieties ; in twenty-four cases wild forms are met
which may be cultivated plants which have been dis-
persed and have become naturalised ; in three cases
the wild and cultivated forms differ to the extent of
being considered as distinct species ; in three cases
the species are distinct ; in twenty-four the wild form
is unknown, but some may yet be recognised after
more careful investigation. Upon the whole, then,
out of 247 cultivated species of plants 113 exist in the
wild as well as in the cultivated state, identical or more
or less modified ; twenty-seven are doubtful ; and
twenty-seven have not been found growing wild. Such
is the result obtained by De Candolle in his valuable

a large amount of useful information and valuable suggestions are
embodied (April, 1892).

1 Origine dcs Plant es Cultivces, 1883.

174 EXPERIMENTAL EVOLUTION LECT.

investigations. Among these 247 species there are
seven which are rapidly becoming extinct.1 We thus see

1 The following is De Candolle's list : —

I. Species spontaneously growing in the wild state, with all
the appearance of indigenous species, and identical with

the cultivated species 1 69

Of these 169 species 31 are of very remote origin ; 56
have been cultivated for more than 2000 years ; the others
are of unknown date.

II. Species of the same category as I., but which have been
found in a wild condition in one locality only, and only by

one observer 3

Cucurbita maxima. Faba vulgaris. Nicotiana tabacum.^

III. Species seen and noticed, but not gathered, by non-
botanical observers who may have been mistaken (old
authors) 2

Carthamus tinctorius, Triticum milgare,

IV. Species found in a wild state, by botanists, under forms
which differ slightly from those which are cultivated, but
not enough to prevent most botanists from recognising
that both are of the same species 4

Olea europea, Oryza saliva, Solanum tuberosum, Vitis vinifera.
V. Species found in a wild state, but considered by some
authors of different species, by others, of different variety,

when compared to the cultivated forms... 15

Allium ampeloprasum porrum, Cichorium endivia
var.*, Crocus sativus var., Cucumis melo*, Cucurbita
pepo, Helianthus tuberosus, Lactuca scariola sativa,
Linuni usitatissimum anmuim, Lycopersicum esculen-
tum, Papaver somniferum, Pyrus nivalis var., Ribes
Grossularia*, Solanum melongena, Spinacia oleracea var. *,
Triticum monococcum.

1 Italicised names are those of species which have been cultivated for
a very long time ; names with an * are those of plants cultivated
for less than 2000 years.

iv WILD AND CULTIVATED TYPES 175

that the greater number of cultivated plants are known
also in their wild condition. This result may seem
surprising and we may wonder at it. As De Candolle

VI. Species found in a sub-spontaneous condition, similar to
any one of the cultivated forms, but which are perhaps

cultivated species having run wild 24

Agave americana, Amarantus gangeticus, Amygdahis
persica, Areca catechu, Avena orientalis*, Avena sativa,
Cajanus indicus*, Cicer arietinum, Citrus decumana,
Cucurbita moschata, Dioscorea japonica, Ervum ervilia,
Ervuni lens, Fagopyrum emarginatum, Gossypium bar-
badense, Holcus saccharatus, Holcus sorghum, Indigofera
tinctoria, Lepidium sativum, Maranta arundinacea, Nico-
tiana rustica, Panicum miliaceum, Raphanus sativus,
Spergula arvensis.

VII. Species found in a sub-spontaneous condition, but different
enough from the cultivated varieties to allow most botanists

to consider them as distinct species 3

Allium ascalonicum* (form of A. cepal), Allium scoro-
doprasum* (form of A. sativum ?), Secale cereale (form of
some other Secale ?).

VIII. Species not found in a wild condition, nor in a sub-
spontaneous state, having perhaps originated in cultivated
forms, but too widely different not to be commonly called

species 3

Hordeum hexastichum (derived from H. distichum?},
Hordeum vulgare (derived from H. distichon ?), Triticum
spelta (derived from T. vulgare ?).

IX. Species not found in a wild or sub-spontaneous condition,
having originated in countries whose indigenous flora is
not yet sufficiently known, but where wild species exist

which are perhaps the same 6

Arachis hypogaea, Caryophyllus aromaticus, Convol-
vulus batatus, Dolichos lablab*, Manihot utilissima, Pha-
seolus vulgaris.

176 EXPERIMENTAL EVOLUTION LECT.

says, "we should have believed a priori &&&. a much
larger number of species which have been cultivated for
more than 4,000 years, would have departed from the
original type to such a degree that the latter could not
be recognised. It appears, on the contrary, that the
wild forms have generally persisted." And he goes
on to explain this fact in two ways. First of all, the
period of 4,000 years is comparatively short, when we
consider the duration of most phanerogamous species ;
and on the other hand, intercrossing between the
wild and the cultivated forms may have prevented
the production of considerable differences between
them in all cases where the wild form persisted. This
last view is very important and goes far to explain
why the cases where the wild progenitor is not re-
cognisable are not more frequent ; and if it is correct,
we should find the largest departure from the original

X. Species not found in a wild or sub-spcitaneous condition,
having originated in countries whose indigenous flora is
yet incompletely known, but more different from the wild

species of these countries than in the preceding case 18

Amorphophallus konjak, Aracacha esculenta, Brassica
chinensis, Capsicum annuum, Chenopodium quinoa, Citrus
nobilis, Cucurbita ficifolia, Dioscorea alata, Dioscorea
batatas, Dioscorea sativa, Eleusine coracana, Lucuma
mammosa, Nephelium Litchi, Pisum sativum*, Saccharum
orncinarum, Sechium edule, Trichosanthes anguina*, Zea

Total 247

iv VARIETIES DUE TO CULTIVATION 177

type in species cultivated in countries where the wild
form does not exist.

The foregoing facts show that some modification is
due to cultivation, in cultivated plants, since some
species exist which are not recognised in the wild
state, such as indian-corn, sugar-cane, wheat, etc. But
numerous modifications are met with, when we con-
sider our cultivated species themselves, and investigate
the orgin of the varieties they exhibit. Here, culti-
vation shows itself as having played an important
part. Let us consider, for instance, the cabbage,
Brassica oleracea, which is most probably a European
species. While Theophrastus recognised three varie-
ties, Pliny was acquainted with six, Tournefort with
twenty, and De Candolle enumerates more than thirty.
These varieties are probably all due to cultivation, and
in some cases the differences between them are very
considerable, and the differences between the varieties
and the parent form, which still exists in France and
England, are greater still. Almost every part has
varied in this species, from the root to the tip of the
leaves and the peduncles of the flowers. Compare
Brussels sprouts and Hungarian turnips, cauliflowers
and common cabbage, for instance, or let us turn
to the common kidney bean (Phaseolus vulgaris) ;
here also varieties are numerous. The potato has
also a large number of varieties although its cultiva-

N

i;8 EXPERIMENTAL EVOLUTION LECT.

tion is of recent origin ; among the radishes consider-
able differences obtain, whatever their original form
may have been ; and the same is true of carrots, lettuce,
strawberries, peaches, pears, apples, oranges — in fact,
of every cultivated species we are acquainted with.
In all these species, and also in all plants which are
cultivated for the sake of their flowers, or because
they provide drugs which are of use to man, in all
vegetable species, in short, which mankind cultivates
for some reason or other, numerous varieties exist,
and in many cases we meet with twenty, thirty, or
forty varieties, if not even more, in the same species.
These varieties man is responsible for : he has made
them, he has evolved them out of the species, and
some are of very recent origin, such as the Brussels
sprouts, for instance — some were made yesterday, and
others will appear to-morrow. The process may be
indefinitely varied, and so long as man cultivates
plants he has the right to expect to create new
varieties. The method used in such creations is no-
wise mysterious, and all breeders, horticulturists, and
gardeners are acquainted with its application.

The mere enumeration of our garden vegetables,
fruit trees, commercial and industrial plants, garden
trees and flowers, and even their names show that
variability exists amongst cultivated plants as well
as among the wild species, and in plants generally

iv INFLUENCE OF ENVIRONMENT 179

as well as in animals. It is because plants and
animals vary naturally or spontaneously — here spon-
taneously merely means from unknown causes — that
man has been able to select among the variations
and to make them become permanent. And when
we see how very different are the lines along which
the same species has varied — take the cabbage, for
instance, or the dog — we are warranted in drawing the
conclusion that variability is very considerable among
cultivated or domesticated organisms.1

We must now consider the last of the three groups
of facts which lie at the basis of experimental trans-
formism. We have considered variability in the state
of nature, and shown that it is to be met with in all
parts of the organism ; we have also shown that the
same variability obtains among cultivated plants and
domestic animals whose numerous varieties are the
result of man's selection. We must now refer to the
facts which show how natural variability may be
determined or facilitated. These facts may be
arranged under the general heading of the influence
of environment in the production of variations.2 Their

1 See De Candolle's Origine des Plantes Cultivees, and Sturtevant's
important series of articles on Originof Cultivated Plants, in American
Naturalist y 1887-89.

- Besides Samper's well-known Animal Life (published in the Inter-
national Science Series], the reader will find a large body of subsequent
literature condensed in J. Arthur Thomson's Synthetic Summary of the

N 2

i8o EXPERIMENTAL EVOLUTION LECT.

interest lies in the fact that they can help to show us
how — and how far — we can produce variation instead
of having to wait for its spontaneous appearance. It
must be said that up to the present date but little has
been done in this line. Such investigations are only
of speculative interest — at least they seem so to most
people — and they require much time and patience as
well as favourable conditions which are seldom
offered by our city laboratories. On the other hand,
we are allowed to use many facts of observation in
this demonstration of the influence of environment
upon parts or the whole of living organisms : they are
of as much value as direct experiments when we can
really ascertain what are the influences which have been
in action. Between observation and experimentation
there is not as much difference as is commonly said, and
when the conditions under which any phenomenon is
observed can be exactly recognised, the result of the
observation has all the value of that of an experiment.1
The investigation of the direct influence of environ-

Influence of the Environment upon the Organism. Proc. Roy. Phys.
Soc. Edin. 1887.

1 An observation made under circumstances which allow all the
elements which co-operate to be well ascertained has as much worth as
an experiment ; the only difference being that in the latter case the
experimenter's will has determined the conditions while in the former he
has had no control upon them. But if he is exactly acquainted with
these, the result is quite as valuable, and the difference lies only in the
mental process which precedes the recording of the result.

iv ENVIRONMENT AND LIFE 181

ment illustrates from the very first a fact which is
more or less familiar to all, the fact that living organisms
can withstand, generally speaking, but a small amount
of environmental modification. They are in so many
ways, and by so many parts, dependent upon the ex-
ternal medium, their adaptation to it is so very close,
and the slightest change in environment is apt to react
on such a large proportion of the vital functions, that
we cannot wonder at the enormous influence which
external modifications can exert on life. Suppose
for instance the very small percentage 0,030-0,034% of
carbonic acid which always exists in our atmosphere,
were to disappear, life would soon be extinct on the
whole earth, because plants cannot do without it, nor
animals without plants. Thus a very small change,
which would be perceived only through the use of precise
methods and instruments, and could not be detected by
our unaided senses, would suffice to ruin all life. This
instance shows how very close is the adaptation
between organisms and their environment, and
teaches the need of care in all our experiments on
the action of the latter on the former. A great
number of instances are known which show the
considerable influence of minute external variations,
but none, I think, is more cogent than that which I
gather from the excellent Etudes chimiques sur la
Vegetation of Jules Raulin (Paris, 1870). This writer,

182 EXPERIMENTAL EVOLUTION LECT.

while investigating the influence of the different
elements which go to make up that complex whole
which we call environment, has studied the influence
of many chemical substances upon the growth of
Aspergillus niger. After having ascertained the
exact nature and proportions of the chemical sub-
stances which are required to provide for the plant
the best suitable medium, he has investigated the
influence of some chemicals which do not contribute
to the making of that medium. Some of them exert
a most unfavourable influence ; thus bichloride of
platinum for instance prevents all vital manifestations
of Aspergillus ; even when added in the very minute
dose of y~oVo-, **• kills the plant. With bichloride of
mercury these results are still more striking, as the
dose of -5ToVcro is enough to kill Aspergillus ; and
with nitrate of silver the results are still more
surprising : add only i^nhnnr and death ensues.

It even happens that when Aspergillus is made to
grow in a silver cup, the plant soon dies, because
some of the silver dissolves in the liquid medium, and
although there is not enough of the metal in the
liquid to allow its detection through chemical
analysis, the plant detects it immediately, and shows
that it feels the influence of the poison. Similar
facts are very abundant now, since bacteriology has
sprung into existence, and we all know of the con-

iv ENVIRONMENT AND LIFE 183

siderable influence exerted on micro-organisms by
very dilute reagents. Very minute doses may kill,
in more or less time, most bacteria, and this pro-
vides a basis for the prevention and treatment of
many diseases due to pathogenetic organisms, and
for the disinfection of places where pathogenetic
organisms are supposed to exist. It is needless
here to quote instances. But this investigation has
led to some interesting results, in showing also that
different organisms require different quantities or
proportions of the same substance to cause death, and
that even the same organisms, under different forms,
require different proportions. Here again, in these
very minute and elementary organisms, we find
physiological variability or variation in play ; here
again, in these minute cells, where function would
at first glance appear very elementary, great differences
exist in reaction towards external agents, and hence
in intimate physiology. We know, for instance, that
while bacteria are killed, in one species, at 80° or 90°
centigrade, the spores of the same species require 100°
or 120°; that one species is killed at 40° or 50°,
another at 70°, 80°, or 100° ; that the one thrives well
in such and such a culture, while the other requires
very different media. Here also, once more, physio-
logical variability is in action ; the bacillus of tuber-
culosis, for instance, thrives in bouillon of herring with

1 84 EXPERIMENTAL EVOLUTION LECT.

glycerine, or of clams, or of monkey, hen, or goose,
while in rat broth it becomes very feeble. Each
micro-organism has its very marked preferences as
regards temperature and chemical conditions, and the
susceptibility to variation in these conditions is so very
marked, that while the fowl is too warm-blooded to
allow anthrax to develop, it is enough to cool the
animal artificially to render it inoculable.

These facts show that the correspondence between
the environment and the organism is very close, and that
very slight alterations are enough to cause death, and
the result is that in the experimental investigation of
the influence of environment upon variability, we
must be careful to handle our methods with great
prudence.

But, on the other hand, while in all cases very
slight modifications in environment are apt to
destroy life — especially as concerns chemical environ-
ment— we often justly wonder at the extent of the
modifications which may be introduced into the latter
without impairing the vital functions. Micro-organ-
isms afford numerous instances of this fact, but I
prefer giving some examples from the higher organ-
isms. It is a familiar fact that while most aquatic
animals or plants die very quickly when transferred
from sea to fresh water or from fresh to sea water,
a number of them withstand the change perfectly

iv BEUDANT'S EXPERIMENTS 185

well, and many fishes are known to spend part of
their life in each of these media. Direct experi-
ments on this matter were made in the beginning of
the century by Beudant ; and the results were fully
recorded by him in a paper read to the Academy of
Sciences.1 While sudden passage from one medium
to another was in most cases conducive to death, he
has shown that a gradual passage may be attended
with success. A number of Lymnaea, Planorbis,
Physa, Ancylus, Paludina^ etc. were divided into two
sets ; the one lived in fresh water, the other were put
into fresh water to which, every day, a small quantity of
salt was added. After a few months, when in the
latter case the saltness was 4 °/0 the number of the
foregoing individuals which were yet living in the
salted water was nearly exactly the same as that of
the individuals yet alive in the fresh-water aquarium :
in both aquaria the same number of animals had been
originally introduced, and out of 400 there remained
170 in salt water, 184 in fresh water.

Other species suffered more ; while only 40 °/0
Paludina died in fresh water, 71*54 % died m salt
water, and while Unto and Anodonta all throve well
in fresh water, they all died in salt. It is an

1 F. S. Beudant, Memoir c sur la Possibilite de fairs vivre des Mol-
lusques fluviatihs dans les Eaux salees, et des Mottusques marins dans
les Eaux douces, consideree sous le rapport de la Geologic. Paris, 1816,
Journal de Physique, vol. Ixxxiii. p. 268.

1 86 EXPERIMENTAL EVOLUTION LECT.

interesting fact that some of the animals accustomed
to salt water did very well when suddenly transferred
into fresh water, and also when, a month later, they
were again suddenly replaced in the salt solution,
although, in the latter case, animals of the same
species die immediately when they are placed in salt
water without having been gradually accustomed to it
by small doses of salt.

In another series of experiments Beudant tried to
accustom marine animals to fresh water. These
animals, of the genera Haliotis, Cerithium, Buccinum,
Tellina, Verms, Ostrea, Pecten, Mytilus, when suddenly
immersed in fresh water soon died, although some of
the littoral species certainly seemed to resist longer.
After this experiment Beudant tried to accustom the
same species gradually. He had thirty-eight species
at his disposal, in great numbers, and performed the
experiment as in the converse case, adding fresh water
every day, so that after five months the animals were
living in pure fresh water. Out of thirty-eight species,
twenty withstood the change perfectly well ; 370 out of
610 being alive in fresh water, while in salt water
there were 401 ; while the eighteen others were unable
to exist.

Lastly, in a third series of investigations, Beudant
established the fact that marine molluscs are able to
live in sea water containing 30 °/0 of common salt, a

iv AUTHOR'S EXPERIMENTS 187

much larger proportion than that which is commonly
found in the sea.

These experiments show that animals may be
accustomed to live in media which are very different
from those which they normally inhabit, provided the
change is a gradual one. I performed similar investi-
gations some years ago with different animals,1 with
the view of ascertaining whether it may not be gene-
rally said that the animals which live close to the sea
shore where the fresh water of river and rain must
certainly somewhat sweeten the sea water, are more
liable than others, inhabiting the sea at greater
distances from the coast, to get accustomed to life in
fresh water. I first compared the resistance to fresh
water of three species of Actinozoa, which were A ctinia
mesembryanthemum, Anthea Cereus, and Sagartia
parasitica, putting them at first into an aquarium
containing six litres of salt water and one and a half
of fresh water. All went well. After a few days I
increased the proportion of fresh water, and no change
was apparent, so that on the seventh day I mixed four
and a half litres of sea water with three of fresh water.
On the ninth day death came, carrying off one Sagar-
tia. A second died on the eleventh day, and on the
thirteenth and fifteenth days the two last of this species

1 Henry de Varigny, Beitrag zum Studium des Einjlusses siissen
Wasscrs auf die Seethiere. Centralblait f. Physiologic, 21 January, 1888.

1 88 EXPERIMENTAL EVOLUTION LECT.

died. The other species were doing quite well ; both
are shore-inhabiting animals, while Sagartia lives
at some depth in the sea.

In another experiment, I used animals of very dif-
ferent groups — Carcinus maenas, Pagurus Prideauxii,
Dromia vulgaris, Anthea Cereus, Sagartia para-
sitica, Portunus puber, Doris tuberculata^ Venus (sp. ?),
Actinia mesembryanthemum, Holothuria cucumaria,
Grapsus (sp. ?) — beginning with fresh water 20, and
sea water 70.

I gradually altered the proportions, so that on the
thirty-fifth day I had 80 fresh water and 10 salt
water. I cannot go into details of this experiment,
or record the obituary of the different animals as
they one by one died, dreaming doubtless of shores
where experimenting bipeds are not admitted ; but
the final result was, that on the thirty-eighth
day I had nine animals living, of which eight
were Actinia mesembryantJiemum, and one Carcinus
maenas. While all my Anthea died, as also my
Sagartia (the latter opening the march), I did not
lose one single Actinia mesembryantkenmm. As all
are aware, this species, as well as the Carcinus
maenas^ lives as close as possible to the shore and
to the surface, so that, in fact, both must certainly
in their normal habitat have become accustomed to
a decrease in the saltness of the water. I have wit-

iv AUTHOR'S EXPERIMENTS 189

nessed facts which are exactly parallel l while compar-
ing the influence of increased temperature on Crustace-
ans of different species, some dwellers on the shore,
and others at some distance ; the former withstand tem-
peratures which the latter are unable to resist, and
the reason may be found in the fact that the shore-
inhabiting animals are liable (my experiments were
made in Banyuls on the Mediterranean coast) to be
much warmed in the pools or even in the surface water,
by the heat of the sun.

In the case of heat, as well as that of salt, there seems
to exist a marked adaptation of the organisms, and
this adaptation I have also investigated in regard
quite different animals and conditions.2 For instance
while tadpoles soon die when introduced into water
containing some amount of common salt, it is easy to
enable them to survive by using at first very dilute
solutions to which a small quantity of salt is added
every day or every second day. But even when the pro-

1 Henry de Varigny, Ueber die Wirkung der Temperaturerhohungen
auf einige Crustaceen. Centralblatt f. Physiologic, 1887.

2 Cf. Henry de Varigny : Influence exercee par les Principes contenus
dans FEau de Mer sur le Developpement d? Animaux d'Eau douce.
Comptes Rendus, 1883, vol. xcvii. p. 94.. But many of the results here
recorded have been obtained at a later date, and the paper in which they
have been embodied, read before the meeting of the French Association
for the Advancement of Science, at the meeting held in Rouen, 1883,
under the title : Sur V Action des Variations de Milieu sur les Animaux
d'Eau douce, has remained unpublished.

UNIVERSITY

EXPERIMENTAL EVOLUTION LECT.

cess is carefully and slowly accomplished, the age of
the tadpoles experimented upon must be taken into
consideration, for tadpoles of three weeks' age with-
stand conditions which younger larvae cannot resist.
For instance, young tadpoles, aged two or three days
at the beginning of the experiment, all died when the
water contained eleven grammes of salt per litre,
while those which were three weeks old died only when
the percentage was fifteen grammes per litre. Rather
strangely, tadpoles of four or five weeks which had
been accustomed to live in water containing fourteen
grammes of salt per litre, died rapidly when I trans-
ferred them to their normal element, fresh water : they
had become so well adapted to the new environment
that their normal medium had become deadly for them.
Young eels may also be accustomed to live in salt
water, although they are very sensitive to the influence
of salt, even if there is less than two grammes of salt
per litre of water : at the beginning they feel the
change, and during some ten or twelve hours remain
sluggish, seemingly half paralysed ; but they become
quite well after twelve or fifteen hours, and recover
their usual activity, and may be by gradual addi-
tions of salt accustomed to live in water containing at
least five grammes of salt per litre. P. Bert, Plateau,
Hugo Eisig, and many others have performed similar
experiments with similar results. They all show that

REGNARD'S EXPERIMENTS 191

even inconsiderable differences in the environment,
when sudden, are accompanied with great danger to
the life of animals, while slow change may do no
harm at all ; it even happens that the adaptation of
the animal to the new environment becomes so close
that sudden transfer to the formerly normal one is
dangerous and even deadly. Instances of sudden
changes of any sort where the result is death are to be
met with in nature ; so that in all experiments bear-
ing on the influence of environment upon organisms,
care must be taken to alter it very gradually. Of course
there are great differences in this influence of environ-
ment on life ; any amount of carbonate or of sulphate
of lime, for instance may be added to water in which
tadpoles are living, without any injury ; other reagents
are not equally dangerous, for a number of reasons
which it is needless to enumerate here.

Generally speaking, then, care must be taken to
alter environment slowly, if we wish to appreciate its
influence on organic forms and life. In some cases it
happens that, while not totally impairing life, a change
of environment is conducive to considerable change in
the vital functions. Such 1 Regnard has seen to be the
case in the animals subjected to pressures much
greater than that under which they commonly live.

1 Cf. P. Regnard, Recherches experimentales sur les Conditions
Physiqtusde la Vie sous les Eaux . Paris, 1891.

192 EXPERIMENTAL EVOLUTION LECT.

By means of instruments which he devised, he has
been able to compel animals to live under enormous
pressures, 500, 600, 800, and even 1000 atmospheres,
which corresponds to a depth of over 30,000 feet in
t?he sea, and he has seen that most animals, although
they withstand 200 or 300 atmospheres without
giving any signs of alteration in their vital functions,
pass into a state of latent life when the pressure
becomes higher. For instance, Vorticellae, under a
pressure of 600 atmospheres, become motionless ; the
cilia stop entirely, and the animal does not move at
all : the same phenomenon is observed even at lower
pressures (300), while other animals require higher
ones. The same phenomenon appears with different
species at different pressures. While some are killed
if they remain some time in this condition, others
revive when the pressure is diminished and becomes
normal ; they revive in more or less time. Actinia
plumosa may live a whole hour under 1000
atmospheres pressure : the animal seems to be dead,
and when taken out of the apparatus strikes the
spectator as being larger than before ; when weighed
it is seen to be twice as heavy as before the experi-
ment, water having doubtless been forced into its
tissues. But after some hours the animal is itself
again, has regained its normal weight and dimensions,
and is quite well. The same obtains with star-fishes,

iv EXPERIMENTAL TERATOGENY 193

ascidians, molluscs, worms, crustaceans, some aquatic
insects, while frogs and fishes die when subjected to
high pressures which the former easily withstand.
I cannot enter here upon the details of the experi-
ments or their results, nor upon the reason of these
differences between different species, but the fact of
latent life must be recorded. In experiments on the
influence of environment such circumstances contrary
to the continuation of life must be avoided ; they
may be induced by other factors, such as change of
chemical medium, for instance (in the case of micro-
organisms), and it suffices to notice the fact.

In some cases external influences may make them-
selves felt by creating animals or plants which are
abnormal and monstrous. Although in most cases
life is impossible, through the importance of the
disorders thus introduced, these facts are interesting,
as they go to show that very slight influences may
make themselves felt in a marked manner, when they
are allowed to operate at certain periods of life,
especially during that of early development, which is
the only period during which real monsters may be
produced.

Among the physiologists who have investigated
the question of experimental teratogeny, of the
artificial production of monsters, none deserve
mention more than Camille Dareste, the author of

O

194 EXPERIMENTAL EVOLUTION LECT.

that celebrated work Recherches sur la Production
A rtificielle des Monstruosites ; ou, Essais de Ttratogtnie
Exptrimentale?- While Swammerdam 2 seems to have
been the first to try to produce monstrosities in
animals through experimental means, M. C. Dareste
has been the first to investigate the subject in a
precise manner, and he may indeed be called the
founder of experimental teratogeny. All his
methods, which are of a very simple sort, are
described in his work ; they all have reference, as well
as most of his investigations, to experiments on the
eggs of birds, and they consist : (a) in placing the
eggs in a vertical instead of a horizontal position ; (b) in
covering part of the shell with some substance which
resists the penetration of air ; (c) in keeping the eggs
at temperatures which are slightly below or above
that of normal incubation ; (d) in heating at different
temperatures any two parts of the same egg. These
methods have enabled M. Dareste to produce a large
number of teratological specimens, many varieties of
which were previously unknown, and the results
obtained are very important in the discussion of many
of the higher problems of natural science. But much
remains to be done on the lines of investigation thus
opened, and the main problem to be solved is that of

1 Paris, 1877 > 2nd edition in 1891. Reinwald.

8 Unfortunately, no record has been found of his experiments.

iv EXPERIMENTAL TERATOGENY 195

producing monstrosities which are not of such a sort
as to prevent the continuation of life after the end of
the developmental period. We may expect that
many methods will be discovered through which the
embryo of most groups of animals and plants can
be modified in some degree, without impairing
vital functions, and this discovery will certainly prove
most beneficial to experimental transformism. Other
investigators have, in most parts of the scientific
world, followed M. C. Dareste's experiments, and the
results are valuable. For instance, M. J. Fallou l has
shown that when cocoons of Attacus Pernyi are hung
vertically, the butterflies are normal, while if resting
horizontally the same cocoons yield abnormal butter-
flies. He adds that a very slight disturbance in the
internal conditions of the mode of suspension is enough
to induce important variations. This point should
be investigated anew. Again, G. Pouchet and Chabry
have recently investigated the influence of some che-
mical conditions on the development of young sea-
urchins, by depriving the water in which the eggs are
hatched of one of its normal components, carbonate of
lime,2 and they have seen that under such conditions

1 Etude sur la Prod^lction Artificielle des Lepidopftres anormaux.
B^lll. Soc. Acclimatation, 1887, p. 499.

2 Sur le Developpement des Larves d* Our sin dans FEau de mer
privee de Chaux. Comptes Rendusdela Societe de Biologic, 1889, p. 17.

O 2,

196 EXPERIMENTAL EVOLUTION LECT.

considerable differences are noticeable in the evolution
of individuals. The less carbonate there remains,
the slower is the development ; and in no case does
the larva go any further than the Pluteus stage. But
the most interesting fact is that these embryos do not
acquire the spicules which are so characteristic of
their structure. The problem now consists in
obtaining such abnormal embryos with sufficient
vitality to keep alive, for the Pluteus obtained by
Pouchet and Chabry have always proved unable to
outlive the stage known by the same name. Recently
also M. Marcacci has shown that when eggs — of the
common fowl — are subjected to motion during^ the
period of incubation, abnormal chicks are obtained
and this is a new method of producing monsters.

The foregoing general facts are enough to entitle us
to draw the conclusion that environmental changes,
while in many cases liable to cause rapid death, or
considerable disturbance of vital functions, may in
others, and especially when care is taken not to
produce too important modifications, result in
organisms which diverge widely from the common
form. As yet, however, the divergences have been
too great, involving changes which make life impos-
sible. But new investigations may show that this
influence of environment can be reduced in degree,
so that the organisms thus modified may be able

iv ENVIRONMENT AND DEVELOPMENT 197

to live to the adult condition. At all events, it is
certainly more interesting for us to see that slight
external causes may determine considerable effects
than it would be to meet with sheer impossibility of
any action or influence. The facts that we are now
acquainted with go to show that the influence of
environment upon the development of the egg is
considerable — from the very first stages of the
building of the embryo, from the segmentation process
itself. This has been ascertained by H. W. Conn in
reference to the eggs of Thalassema mellita, where
segmentation is regular or irregular according to the
mode of life — free or protected ; by Pfliiger, in
reference to amphibian eggs, by O. and R. Hertwig,
and by Marcacci ; while Tichomiroff has witnessed
parthenogenesis artificially induced in insects by
chemical stimuli.

Many facts also go to prove that external influences
are very efficient in accelerating or retarding
the developmental processes, as every naturalist has
certainly noticed when comparing the development of
eggs from the same Lymnaea or Planorbis for
instance, under different conditions of heat or light ;
and other facts show that environment also exerts a
marked influence on the general metabolism of the
body.

This influence is illustrated by experiments on the

198 EXPERIMENTAL EVOLUTION LECT.

growth of animals or plants, and it may be well to
dwell upon this. As a general fact, growth and
dimensions are correlated with the quantity and
quality of food. All breeders know what is the most
suitable food for their animals, according to the result
they wish to obtain ; all agriculturists know exactly
what are the manures they must use, according to
the soil on which they grow their plants, and the
species, the varieties even, that they put under culti-
vation. These facts have been put beyond doubt by
the numerous experiments which have been performed
in the English, French, and German agricultural
stations, and all have seen illustrations showing the
influence of the principal manures, if not the plants
themselves. Although these sorts of experiments
originated over a century ago — although Tillet began
in 1770 to perform investigations with artificial soils
made with different proportions of natural earth, with
the view of ascertaining the influence of the com-
ponents on the crop obtained, the study of manures,
conducted in a scientific manner, has been only during
the present century made to yield the precise and
valuable results we are all acquainted with.1 But

1 Tillet 's experiments were published under the following title : —
Experiences et Observations sur la Wgttation du Bit dans chacune des
Matieres simples dont les terres labourables sont ordinairement composes,
et dans different* melanges de ces matib-es, par lesquels on s'est rap-
procht de ceux qui constituent ces mtmes terres a labour. Histoire et

iv ENVIRONMENT AND GROWTH 199

many other external conditions exert a considerable
influence on growth and weight, such as light, heat
etc. In 1709 De Vallemont 1 noticed — others may
have done the same before him — that in trees the
wood is thicker on the southern than on the northern
aspect, and he ascribed this fact to the greater heat
received by the southern side of plants ; and Kraus
has shown that fruits grow much more during the
night than during daytime, the difference being be-
tween eighty or ninety and twenty or ten per cent. ;
eighty per cent, of the growth of an apple, for instance,
occurring at night-time, while twenty per cent,
occurs during the day.2 On these points further
information is to be found in any text-book of
plant physiology, such as those of Sachs or of
Vines.

Concerning animal growth and its dependence upon
external conditions, Yung,3 of Geneva, has performed
many useful experiments, showing how considerable
variations are induced in the length and dimensions
of tadpoles through the use of different foods, animal
foods, such as egg and flesh especially, being much

Memoires de f Academic Royale des Sciences, 1772, p. 99 of Part I. of
the Memoires.

1 Curiosites de la Nature et de FArt, 1709, p. 57.

2 Cf. Naudin, Rythme de la Croissance. Revue Horticole, 1872,
p. 408.

3 Cf. his recent Propos Scientifiques^ in which are abstracted most of
his investigations.

200 EXPERIMENTAL EVOLUTION LECT.

more suitable than vegetable food. He has shown
also that growth is certainly correlated with other
influences, since, even when food is superabundant,
tadpoles become sooner transformed into the adult
form when they are few than when they are numerous
in the same space. This had already been noticed by
Semper in his experiments on Lymnaea stagnates* to
which reference has already been made, and I have
also spoken of my own experiments on the same
subject.2 To these facts I shall merely add the
general fact, recorded by Herbert Spencer, that trout
and other fishes living in small streams are generally
small ; that pond-snails grow larger in ponds than in
rivers, and that under natural conditions, as Balas-
chewa has noticed, the smaller the mass of water in
which molluscs live, the smaller they remain. And
R. P. Whitfield,3 who has performed experiments
similar to those of Semper, has obtained the same
results, with this additional interesting circumstance,
that when the dwarfing process is made to operate

1 C. Semper, Ueber die Wachsthums-Bedingungen der Lymnaeus
stagnalis. Arbeit en aus dem Zool. Zoot. Institut zu Wiirzburg, vol. i.,
1874.

2 H. de Varigny, Contribution Experimental a f Etude de la Crois-
sance. Comptes Rendus, June 15, 1891.

3 Description of the Animal of Lymnaea megasoma (Say), with
some Account oj the Changes produced by Confinement in Aquaria
and under Unnattiral Conditions. Am. Naturalist, 1880, p. 51
(abstract).

iv ENVIRONMENT AND PHYSIOLOGY 201

on successive generations, important sexual changes
occur which are correlated with the changes in growth
and size ; instead of being as usual hermaphrodite
the individuals (of Lymnaea megasoma] become uni-
sexual and are exclusively female. At the same time
also the hepatic gland undergoes a process of partial
atrophy. These influences of external agents on in-
ternal viscera, such as the sexual glands and liver,
whether directly or indirectly exerted, are very inter-
esting, and more cases of a similar nature may be
discovered if more attention is paid to the process. It
is merely a matter of historical interest to recall that
the father of natural science, Aristotle, many centuries
ago noticed the variations in growth and dimensions
while comparing animals of the same species in Egypt
and in Greece.

The preceding facts show that external influences
may react on the general growth of organisms, and
perhaps on their internal constitution.

In some cases, however, where variation in environ-
ment might be expected on a priori grounds to inter-
fere greatly with internal constitution, we perceive no
such interference, and we are compelled to draw the
conclusion that the organism admits of a greater
amount of physiological elasticity than we expected.
I find a good instance of such elasticity in the result
of recent experiments which have been conducted by

202 EXPERIMENTAL EVOLUTION LECT.

Messrs. Irvine and Woodhead.1 These experiments
show that when laying hens are deprived of carbonate
of lime by being shut into a room lined throughout
with wood, without sand or soil, they are yet able to
lay normal eggs, provided with the usual shell, if sul-
phate of lime is given to them in their food. It follows
that when the hen's organism does not receive carbon-
ate of lime as is usually the case, it is able to trans-
form sulphate into carbonate. We do not know
exactly how things go on in this case, nor even in the
normal case.2 Are carbonate and sulphate of lime trans-
formed into phosphate for instance, which is carried
under this form to all parts of the organism, and is in
the oviduct transformed by nascent carbonic acid — the
result of the respiration of tissues — into carbonate of
lime ? In such case the thing would be less surprising
than in any other hypothesis ; at all events, whatever
the case may be, we have here a very precise* instance
of external variation being met by the organism,
whether its physiology varies or not. But other
animals offer the reverse instance, as Irvine and

1 R. Irvine and G. Sims Woodhead : On the Secretion of Lime by
Animals ) Proc. Roy. Soc. Edin. May 7, 1889, and Secretion of Carbonate
of Lime by Animals (Part II.), ibid.

2 I would refer the reader, for a recent investigation of this matter, to
Moynier de Villepoise : Note sur le Mode de Production des Formations
calcaires dti Teste des Molhisques. Comptes Rendus Societe de Biologic,
1892

iv IRVINE AND WOODHEAD'S EXPERIMENTS 203

Woodhead have shown. They have seen that crabs
living in sea-water from which chloride of calcium is
excluded, cannot, after shedding their exoskeleton,
form a new one even when sulphate of lime and chloride
of sodium are present in the water : chloride of calcium
is quite necessary for the formation of the crab shell.
Considering now external form, we see that it may
be influenced by external influences, as well as internal
constitution or physiology. Here are some instances
out of many. M. Languet de Sivry, some fifty years
ago,1 noticed that seeds of short-rooted carrot, when
sown in a particular soil, in the alluvial deposits
formed by a small river in France, yielded imme-
diately, during the first generation, a number of long-
rooted plants, either white or yellow, whose roots
were very much larger than those in the parent plants.
The seeds of the best, or less deformed plants, were
selected, and sown in the same soil. The result was
that in the second generation hardly any roots were
found of the short type, and most were exactly similar
to the common wild form. Again, Petermann (Con-
tribution a la Chimie eta la Physiologie de la Better ave
a sucre, Brussels, 1889) notices the fact, familiar to all
horticulturists, that when a plant — beet for instance —
is grown in poor soil, its root becomes much longer

1 Cf. Societe Roy ale et Centrale d' Agriculture, 2nd series, vol. ii.,
1846-7, p. 539.

204 EXPERIMENTAL EVOLUTION LECT.

than is usually the case because it lengthens in pur-
suit of richer soil ; and when thick-rooted plants, such
as beet, are experimented upon, a very striking differ-
ence is produced in the length and also the thickness
of the root by the chemical constitution of the soil
the plants inhabit.

Many facts of this sort might be quoted. Con-
cerning animals, we may note that Bourguignat thinks
left-handed shells of molluscs are due to some electrical
influences in operation during the period when the
embryo is rotating in the egg (experiment might
settle this) ; and Brot 1 has noticed a fact which,
although very singular, can be merely mentioned
here. One year he remarked a small pond near Geneva
which contained many pond-snails, and found that
nine-tenths of them were in various respects abnormal.
Next year he visited the place again, but found only
normal forms. The fact remains unexplained — but
not unparalleled, as other observers have met with
similar instances — as our writer only notices that in
the first visit he found a large amount of common
Hydra, while none at all were to be found at the
second. It would seem rather audacious to ascribe
the deformations of the molluscs to the presence of
Hydra, even in large quantities ; but, on the other

1 Cf. Locard, Variations Malacologiques, vol. ii., where these facts
are noted.

iv TEMPERATURE AND LIFE 205

hand, I think no naturalist, knowing anything about
the mutual interaction of living organisms, would
dismiss the case entirely, and say that any influence
of the one on the other is impossible and incredible.

Alterations in the forms of animals, especially
molluscs, are very frequent, and in some cases a sug-
gestion as to the causes may be gained, when the
deformed animals live under circumstances where a
departure from the normal conditions is obvious. It
is well known that many warm springs contain a large
number of living plants and animals. Physa acuta, for
instance, has been found in waters at 30° Cent (Fischer),
and even at 33° and 35° Cent, (at Dax, according to
Dubalen, in Soc. Linneenne de Bordeaux, vol. xxix.
p. 4), while Turbo thermalis lives at 50° Cent, at
Albano,1 and Neritina thermophila between 50° and
60° Cent, in New Brittany Island, according to Studer,
etc. But it would seem that when individuals which
have not been gradually accustomed to such con-
ditions, through their ancestors, live for the first time
in such unnatural media, many deformations are apt
to appear. M. G. Regelsperger 2 has observed the
following case. The waters of an artesian well, sunk

1 De Blainville's article Mollusques, in the Dictionnaire des Sciences
Naturelles, 1816-30.

2 Deformations remarquables de Physa acuta observees a Rochefort
surMer. Actes de la Societe Linneenne de Bordeattx, vol. xxxix. (vol. ix.
of 4th series), 1885, p. 117.

206 EXPERIMENTAL EVOLUTION LECT.

many years before, were made to run into a garden.
The water was ferruginous, and its temperature was
32° or 33° Cent, in 1881, when the writer first began
to notice the facts. At that time individuals of
Physa acuta were seen in the water, and it was re-
marked that they were generally small, and in many
cases much deformed, as one may perceive by a
glance at the illustrations which accompany M.
Regelsperger's paper. In 1882 the temperature of the
water had fallen off considerably ; instead of being at
32° or 33° it had decreased to 26°*5. M. Regelsperger
again examined the animals, and saw that deformed
individuals were very scarce. Since then the flow of the
water has entirely ceased, the pipes having become im-
permeable, and the part where the animals are seen re-
ceives simply rain-water. Now the animals seem larger
than they were when they lived in warm water, and
none are deformed. In this case it seems quite certain
that the deformations were the result of the heated
water the animals lived in/ and experiments can easily
be made to prove the fact, or to disprove it, as the case
may be. Ritzema Bos l has observed other deforma-
tions, or form-alterations, in very different animals
and circumstances. Tylenchi (Tylenchus devastatrix),
which have been accustomed for some generations to

1 Untersuchungen ilber Tylenchus devastatrix. Biol. Centralblatt,
vii., 1887, pp. 232-243.

iv ENVIRONMENT AND DEFORMATION 207

feed on one single sort of plant, acquire form and size
which differ from those of the same species fed on
other plants, and it even seems that here physiological
variation also comes into play, since prolonged life
on one plant makes them less dangerous for other
sorts of plants.

Deformations may be determined by other natural
causes. M. Pire 1 has seen Planorbis complanatus much
deformed in Belgium through the influence of a thick
layer of aquatic plants on the surface of the pond,
preventing easy access to the air, and S. Clessin 2 ex-
plains the numerous deformations of the Lymnaea
tumida in the Bodensee and Starnbergsee as due to
the constant motion of the surface of these two lakes.

Form may vary in plants also, according to motion
for instance, many plants being much smaller and
much deformed in windy localities. Behrens has
noticed the influence of currents on the forms of
aquatic plants, which E. Mer and others have also
done ; and this leads us to consider the variations in
internal structure, and in functions which are cor-
related with those modifications of external characters.
E. Mer is among those who have investigated the
matter in the most precise manner, and the results

1 Annales Soc. Malacologiqne dc Belgiqtie, vol. vi., 1871, and xiv.,
1879.
a Deutsche- Excursions Molhisken Fauna, Nuremberg, 1876, p. 368.

2o8 EXPERIMENTAL EVOLUTION LECT.

obtained are interesting. His investigations were
made upon amphibious plants.1 In Ranunculus
aquatilis the external differences are well known
between the plants which grow in water, and those
which live on land, in the length and thickness of the
stem, the length of internodes, etc., and if direct ex-
periment and observation had not shown that the
two forms belong to the same species, they would
certainly be considered as different. Important
structural differences are also present. If we consider
the leaves only, we see that in the aquatic leaf the
dichotomies are from eight to ten in number ; the
cells are cylindrical with two or three hairs ; the
epidermic cells are regularly shaped and contain
chlorophyll, and bear but few stomata ; while in the
air-inhabiting leaf, dichotomies are from two to six
in number ; cells are flattened, without hairs ; epidermic
cells are irregular and contain no chlorophyll, while
they bear a large number of stomata. The same
differences obtain in the leaves of Carex ampullacea
as shown here :

Submerged leaves. Leaves not submerged.

Epidermic cells long, wide, Very thick cuticle. Nu-

without stomata. merous stomata.

2-3 rows of cells with 4-5 rows of cells with abun-

chlorophyll. dant chlorophyll.

1 E. Mer, Des Modifications de Forme et de Structure que subissent les
Plantes suivant qu'elks vegttent a F Air ou sous V Eau. Bull. Soc.
Botanique, 1880, p. 50.

iv ENVIRONMENT AND LEAF-FORMS 209

In a more recent paper Costantin has investigated
the same subject, and given special attention to the
influence of environment on the production of
stomata.1 In Hippuris vulgaris the leaves which live
in water are long, thin, and sinuous, while in the air
they are short and thick ; in the water the epidermis
consists of short regular cells, bearing a number of
stomata, while in the water the cells are long, thin,
narrow, and bear no stomata. The writer has from
the same rhizome of Polygonum amphibium grown
two plants, one in water, the other in air, and while
the latter was provided with numerous stomata, the
former had none at all. This illustrates well the in-
fluence of environment on the production of stomata,
and in Stratiotes aloides stomata are seen to appear
on the leaves as they gradually emerge above the
surface of the water. But the most minute and
valuable investigations in reference to this matter
have been conducted by M. Pierre Lesage, and were
described last year 2 in his inaugural thesis. His re-
searches bear upon the question of the influence of

1 Costantin, Influence du Milieu Aquatique sur les Stomatcs. Bull.
Soc. Botanique, 1885, p. 259.

2 Pierre Lesage, Influence du Bord de la Mer sur la Structure dcs
Feuilles. Rennes, Oberthur, 1890. See also his Contributions a la
Biologic des Plantes du Littoral et des Halophytes ; Influence de laSalure
sur f Anatomie des Vegetaux, ibid. 1891, which contains an abstract of
many experiments performed after the publication of this thesis.

210 EXPERIMENTAL EVOLUTION LECT.

shore and inland life on different individuals of the
same species, the number of species investigated
being eighty-five. The results have been that in
fifty-four species leaves are thicker in the vicinity
of the sea than in inland individuals ; in twenty-seven
species no difference is apparent ; and in four, leaves
are thicker inland than near the sea. If we consider
that of the fifty-four species above mentioned, seven-
teen are shore-inhabiting plants, while thirty-seven
live preferably inland, it is obvious that, generally
speaking, inland plants acquire thicker leaves when
living in the vicinity of salt water. So much for the
external characters. Now if we consider internal
characters, many differences are detected which ex-
plain the presence of the external differences, and
these differences are observable in all parts of the
leaves. Epidermic cells are larger in twenty-three
shore plants, but in thirty-one there is no differ-
ence, while in four the difference turns to the advan-
tage of inland plants. Here, then, the influence
makes itself but little felt. The case is quite altered
when the mesophyll is considered, for while in eleven
species there is no difference, in all others the palisade
cells are either more numerous or attain greater
thickness, or exhibit both characters at once, and
at the same time the interspaces which underlie
the stratum of palisade-cells are much reduced. The

iv LESAGE'S EXPERIMENTS 211

principal cause of dimensional differences is then to
be found here. And lastly chlorophyll is less abun-
dant in shore-inhabiting individuals. These facts of
observation have been confirmed by experimental
facts. M. Lesage has cultivated plants of the same
species under precisely similar conditions save one,
and has found that the results concur with his obser-
vations. The one condition which differs between the
two sets of cultivations is the presence or absence of
common salt in the water used for watering the plants.
Of two individuals of the same species the one which
has grown in soil watered with salted water has thicker
leaves, and in these leaves the palisade cells are seen
to be larger and more numerous. The experiments
show that the influence exerted by sea-shore life
on plants is principally due to the salt which is always
contained in lesser or greater quantities in the soil,
and is brought there by the winds carrying small
drops of sea-water from the crests of the waves ; they
show at the same time that external variations are
accompanied by important structural differences.

Sea-shore life or the presence of some common salt
in the soil where plants grow exerts even more im-
portant variations ; variations not in morphology
and anatomical features, but in the physiological
processes. In experiments concerning radishes M.
P. Lesage has seen that while in radishes watered

P 2

212 EXPERIMENTAL EVOLUTION LECT.

with common pure water starch is never or but rarely
present in the root at the period when it is generally
eaten, plants of the same age watered with solutions
of common salt (from I to 20 per thousand) do con-
tain a great deal of starch under certain conditions.
For instance, if the water contains 20 per mille of
salt, or i or 2 per mille, there is no starch ; at 3 or
5 °/oo tnere is little of it ; at 10 %0 a little more, but at
4 °/oo there is a large amount of starch. Thus, the
presence of common salt, in definite proportions, exerts
a considerable influence on the chemical structure and
physiology of the plant.1 With Lepidium sativum
things are somewhat different : while the plant con-
tains normally a large amount of starch, watering
with a solution containing 10 °/00 or more of common
salt causes the starch to diminish in a large measure
and even to disappear totally, while weak solutions
do not interfere with the proportions of this sub-
stance.2

1 Cf. Lesage : Sur la Quantite d'Amidon contenue dans les Tuber-
cules du Radis. Comptes Rendus, September 7, 1891.

2 Cf. Influence de la Salure surla quantite de f Amidon contenue dans
les Organcs vegetatifs du Lepidium sativum (Comptes Rendus, April 20,
1891), and two other notes in the Comptes Rendus, January 18, 1892,
and March 31, 1891. I would also refer the reader, on this general
subject i of 'the influence of salt on structure and physiology, to A.
Batalin : Wirkung des Chlornatriums auf die Entwickelung von
Salicornia herbacea (International Meeting of Botanists and Horti-
culturists in St. Petersburg, 1884) ; and to C. Brick : Beitrage zur
Biologic tind vergleichende Anatomie der baltischen Strandpflanztn

iv SCHMANKKWITSCH'S EXPERIMENTS 213

But external differences seem in some cases to have
much greater moment than has hitherto been re-
cognised, and in this respect no facts are of higher
interest than those which were some years ago made
known by the investigations of a Russian naturalist,
M. Schmankewitsch,1 to whose work I must call
attention, although most have certainly heard more
or less about it. Daphnia (or Moina) rectirostris is a
small Crustacean which lives indifferently in fresh
water, in brine ditches, and in salt lakes when the con-
centration varies from five to eight degrees of Baume's
areometer. But this difference in life-conditions is
.accompanied by noticeable variations in the physiology
and structure of the animal. The mean temperature of
the salt lake being lower than that of the fresh waters,
Daphnia while being a summer form in the latter
becomes an autumn form in the former, and thus
has acquired the custom of living and even multiply-
ing in salt water at temperatures at which the fresh-
water form cannot live. So much for the physiological
variation. M. Schmankewitsch goes on to say, as

(Schriften der Naturforschenden Gesellschaft zu Dantzig, 1888). Both
authors obtain results which are entirely confirmed by M. Lesage's
investigations.

1 Cf. Zeitschrijt f. Wiss. Zoologie, 1877, vol. xxix., p. 429, and also
the Transactions of the Neo- Russian Society of Naturalists for 1875.
The original papers have been abstracted in Packard's Monograph of
North American Phyllopod Crustacea, 1883, Washington (Geological
Survey).

214 EXPERIMENTAL EVOLUTION LECT.

concerns anatomical characters : "In the females of
the Chadschibai Lake the penicilli or fascicles of knob-
bed setae (Tast-Borsteri) are but little developed, being
nearly fifty times shorter than the antennae themselves,
while in the females of fresh water the same sensitive
penicilli are moderately long and only six times
shorter than the entire antennae. In the males the
sensitive rods are also shorter than in those males
inhabiting fresh water. The small hooks situated
near the sensitive rods on the tips of the male
antennae of fresh-water forms are strongly curved
with pointed tips, while in the males of Chadschibai
Lake those hooks are shorter, less curved, and with
blunt tips. Of the two pointed pale sensory threads
situated on geniculated protuberances of the first
posterior third section of the male antennae, the
posterior one is a little shorter than the anterior
thread, the latter coming out a little more in front.
These threads are, in the males of Dqphnia rectirostris
of the Chadschibai Lake, not in a straight but in a
screw-like line. The distance between the threads is
considerable, which character in the fresh-water males
is much less prominent." I should scarcely have
ventured to quote the foregoing lines, and to enter into
such very minute details, if it was not a fact familiar
to all that many zoologists are to be found in all
countries who spend their life in establishing new

iv SCHMANKEWITSCH'S EXPERIMENTS 215

species which are often based on characters such as
those which Schmankewitsch refers to. These are
specific characters, or at least we are told so every
day by any number of systematic zoologists, and they
are supposed to know " all about species," so we may
go on with the quotation. " Besides the differences
observed in the antennae of the salt-water generations
of Moina rectirostris, our attention is called to the
number of slender finely-toothed spines which occur
on the lateral surface of the post-abdomen of Daphnia
rectirostris, running in lateral series and nearly parallel
with the direction of the rectum. Leydig called them
finely-feathered spines, which I would have called
triangular laterally dentate plates. However this
may be, we observe in our fresh-water forms of
D. rectirostris on each side from eleven to thirteen of
these spines or plates, and only from seven to nine
in the salt-lake form, meaning here, as a matter of
course, mature individuals only. In younger specimens
there are fewer spines than in the adults of the same
surroundings, and therefore the young fresh-water
forms have the same number of spines at a certain
age as the adult forms of the salt lake, which demon-
strates the retarded development of the latter." And
further on : " We now find, in comparing the fresh-
water generations with the salt-water generations of
Daphnia rectirostris, that the latter generations are

216 EXPERIMENTAL EVOLUTION LECT.

not only changed in consequence of the immediate
effect of the surrounding elements, but also in con-
sequence of retarded development under their influ-
ence ; and, furthermore, that sexual maturity shows
itself in the salt-water generations earlier than the
complete typical development of the body-parts.
The termination of the sensory antennae, the colour
of the body, the lesser pinnulation of the bristles in
the salt-water generations are principally dependent
upon the immediate effect of the surrounding elements.
The smaller number of the above-mentioned spines
on the post-abdomen principally depends upon the
retarded development under the influence of changed
surroundings."

We thus see that the change of environment makes
itself felt in various changes in the anatomy and
physiology of the species investigated. The same
conclusion holds good in the case of Branchipus
ferox, another Crustacean which inhabits both salt
and fresh waters. The differences relate to the
length which the egg-sac attains, the segments
of the animal, its shape, the length of the furcal
lobes, and the bristles of the latter. " The most
important difference," says Schmankewitsch, " con-
sists in that while in Branchipus ferox of our salt
ditches the furcal lobes have both edges bristled, in
the fresh-water form only the inner edges of the lobes

iv SCHMANKEWITSCH'S EXPERIMENTS 217

are bristled, etc." And he again says, " Had I not
found all possible transitory forms between salt-ditch
and fresh-water specimens, had I not convinced my-
self of the variability by domestication of this form, I
should have regarded the salt-lake specimen as a new
form."

Other investigations have shown M. Schmankewitsch
that Daphnia degenerata is merely a changed and
degraded variety of D. magna, while the latter is an
intermediate form between the typical D. magna and
D. pulex. But among Phyllopods no species seem more
sensitive to the influence of the surrounding element
than the genera Artemia and Branchipus. Changes
in environment are apt to produce such variations in
the same generation that two closely allied forms
hardly admit of distinction. For instance, Artemia
salina, which lives in water whose concentration varies
from 5° to 12° of saltness, exhibits at high con-
centrations (12° or 15°) strong tendencies towards the
form of Artemia milhausenii, which is a form able to
live in water at 24° or 25°, in water where the
self-deposition of salt is imminent, and between both
forms all transitional types are found, which show that
both are really of the same species, since A. milhau-
senii may be obtained from A. salina through the
increase of the proportion of salt in the water. And we
cannot escape the conclusion that either our species

218 EXPERIMENTAL EVOLUTION LECT.

may be transformed into each other, or that the
characters upon which they are based are worthless
and require a severe revision.

To end with external characters, I shall merely
remind you of the facts which illustrate the influence
of environment on integuments ; merino sheep lose
their wool in warm climates and recover it under cold
skies ; Iceland cattle have short and small horns which
develop well under mild temperature ; the silky cover-
ing of the common hen, in Guinea, becomes trans-
formed in Europe into the feathers we are accustomed
to see on our domestic fowl, etc. Such instances are
very numerous, and since the anatomical change
follows immediately upon the change of conditions,
we are at liberty to ascribe the former to the latter.

But we must now turn to more important changes
in internal structure or functions, which may be
experimentally produced at will through environ-
mental changes.

Schiibeler has shown that seeds may, through a
change in climate and environment, be made to
become larger than usual, and also to exhibit
greater rapidity in the germinating process. At the
same time the plants grown from the seeds are
more coloured than in their accustomed climate. This
fact may be ascribed to the influence of the greater
light in northern regions, and light, it is known, is apt

iv ENVIRONMENT AND PLANT LIFE 219

to make up for temperature, within some limits, in
plant growth, as De Candolle and others have shown.
At all events the fact that climate or environment
reacts on the germinative faculty is a positive one.

It is well known that the same animals or plants,
in different climates or conditions, exhibit marked
differences in their physiology and intimate functions.
Grape-vines transferred from the Rhine valley to
Madeira require but a few years to yield Madeira
wine, very different from the Rhine wines. It seems,
from the experience of vine-growers, that the taste of
the grapes and wine depends largely upon the chemical
composition of the soil, some soils being very un-
favourable and always yielding wine or grapes of
inferior taste. Of course, differences in taste are due
to variations in the chemistry and physiological pro-
cesses of the plant and fruit. The same fact may
be observed with most vegetables ; all possess a
pleasanter flavour when grown in one sort of soil
than in another. In some cases these internal dif-
ferences are accompanied by external differences,
and M. Saint Lager has thus been led to consider
Ulex major, Trifolium Molineri, Cirsium anglicum,
and Rhododendron ferrugineum as forms of U. parvi-
floruS) T. incarnatum, C. bulbosum, and Rh. hirsutum,
due to the influence of soil containing much silicon,
while the latter inhabit soils containing much lime.

220 EXPERIMENTAL EVOLUTION LECT.

Some mutilations react on the process of fructifica-
tion, if it be true that by cutting through the medulla of
a grape-vine stem, grapes are obtained which contain
no seeds. The fact has been often spoken of for
at least 1,900 years, as ancient Romans practised it,
according to trustworthy witnesses, such as Columella,
Camulogen, and Pliny.1 At all events the experiment
is worth trying, and some interesting facts might be
derived from it.

Colour variations may be experimentally deter-
mined through changes in environment. Moleschott
has observed that in pure oxygen no black pigment is
generated in the skin of frogs, and the coloration of
birds' eggs sometimes varies with the amount of light
to which they are exposed. These facts are enough
to point the way to many interesting experiments.

We can also produce changes in sexuality, since we
know that the want of suitable depositing ground for
trout, is, according to Barfurth, followed by degenera-
tion and permanent sterility, or at least by the
production of weak forms. In many cases also, defi-
cient nutrition of parents determines predominant
maleness in the progeny, and Giard has shown that
castration parasitaire, as he calls it, that is the presence

1 Cf. Revue Horticole, 1884, pp. 6 and 219; Couverchel, Trait* des
Fruits, 1839 ; Columella, De Arboribus, and also Olivier de Serres,
who knew of the process, but denied its efficacy.

TV WEISMANN'S CRITICISMS 221

of parasites, affects in a marked degree some sexual
characters, males being made thus to resemble more
or less females in external secondary character?, while
complete sterility may be induced through action on
the essential sexual parts.

Fertility may thus be affected in many manners, by
want of space (Semper), by nutrition (Maupas), etc.,
and many facts also go to show that external influ-
ences have a good deal to do with the nature of
segmentation and even with the occurrence of par-
thenogenesis.

As concerns physiological characters, we are also
able to induce much modification, by changes in
pressure for instance, or by altered food, etc. Through
gradual increase of heat we may, as Dallinger has done,
accustom certain Monads to live at temperatures which
are deadly to them in other circumstances ; Chauveau
has shown us how we can profoundly alter the physio-
logical characters of micro-organisms, etc.

At least it seems to us that this conclusion fairly
follows from the foregoing facts. But we cannot
proceed without saying a word of Weismann's posi-
tion in regard to these facts. In one of his essays,
On the Supposed Botanical Proofs of the Transmis-
sion of Acquired Characters, written a few years ago,
Weismann has discussed some cases which are similar
to some of those I have related. One of these cases,

222 EXPERIMENTAL EVOLUTION LECT.

brought forward by Detmer, is that of the shoots of
Thiija occidentalis. These shoots contain in their
upper side green palisade cells, while the under sides
possess green spheroidal cells. And when the branches
are turned upside down, and are fixed in this position,
the anatomical structure of the shoots which put in
their appearance later is reversed ; the side which was
destined to become the upper side, and which a change
in the branch's position has made the lower side,
assumes the structure of the lower side, and vice versa.
A similar case occurs with the climbing shoots of the
ivy, and in Tropaeolum leaves important structural
changes have been noticed by Detmer in response to
differences in external influences, or change of envi-
ronment. Now Weismann says, " Such differences [in
structure] do not by any means afford proof of the
direct production of structural changes by means of
external influences. How would such an explanation
be consistent with the fact that the leaves are, in all
these cases, changed in a highly purposeful manner ?
Or is it assumed that these organs were so constituted
from the beginning that they are compelled to respond
to external conditions by the production of useful
changes ? Any one who made such an assertion now-
adays, or who even thought of such a thing as a
possibility, would prove that he is entirely ignorant of
the facts of organic nature, and that he has no claim

iv WEISMANN'S CRITICISMS 223

to be heard upon the question of the transformation
of species." These are rather big words, and Professor
Weismann has perhaps written somewhat hastily. It
may be answered that all evolutionists, and more
especially " Natural Selectionists," to whom Professor
Weismann belongs, assume the production of " useful
changes " with or without change of external condi-
tions, since those only survive in the struggle for life
who offer beneficial modifications or adaptations.
And of course the production of such " useful
changes " is of much higher importance when the en-
vironment changes than when it remains unmodified.
Professor Weismann denies the importance and trans-
missibility of variations due to external modifica-
tions. But then how does he explain the fact — now
repeatedly ascertained in all bacteriological labora-
tories— that all micro-organisms, bacilli, bacteria, etc.,
undergo under cultivation in different external condi-
tions—whether of light, heat, or food, it matters little
— such important modifications that they may be made
to lose their essential characters, and that these charac-
ters are lost as long as the external modification per-
sists ? Take Bacillus anthracis, for instance. Com-
pared with many other bacilli, it differs very slightly
in external characters ; the principal and all-important
difference is that it determines in many animals a
disease of a very precise character which can be mis-

224 EXPERIMENTAL EVOLUTION LECT.

taken for no other. But this bacillus, if you alter even
very slightly some of the external conditions it lives
in, gradually loses its most important character ; it is
deeply modified for the time being — that is for the
time you compel it to live under particular conditions,
and perhaps even for some time the normal conditions
are restored. The usefulness or unusefulness of the
modification are not in the slightest degree apparent,
and to evolutionists it matters little, since modifications
may be useful, useless, or indifferent, or even injurious,
and natural selection destroys all that is not useful, or
at least indifferent ; but the main fact is that here is an
important modification which puts in its appearance
when some external conditions are changed, and dis-
appears when the normal condition reappears. Is envi-
ronment operative here, or must we assume that when
Bacillus anthracis is cultivated in some particular
manner, it loses its most important character without
any reference to the change of environment ? I dare
say no bacteriologist or physiologist could be met who
would venture to assert that the change of character
is not in direct relation with the change of external
conditions, whether the former is beneficial or not.

It seems, then, that Prof. Weismann goes certainly
too far when he asserts that we have no proof of
the direct production of transmissible changes by
means of external influences. It may be said that he

iv WEISMANN'S CRITICISMS 225

restricts his denial to the Metazoa ; but this is
assuming a physiological contrast to the unicellular
forms of life which it will not be easy to justify. On
the other hand, we possess, in the facts of domestica-
tion and cultivation, a large number of cases of
variation — which occurs in every part — due to environ-
ment, and transmitted by inheritance in various
degrees. Psychology affords similar instances : a
kitten which has never seen a dog is afraid from the
first moment it perceives one ; young birds of many
species instinctively fear the hawk and other birds of
prey, while remaining unaffected by the presence of
other birds. Are these not psychological " attitudes "
due to environment (acting on the mens of ancestors)
which have been transmitted by inheritance ; are
these not acquired characters / I would recommend,
in regard to this discussion, two recent papers : Mr.
J. A. Thomson's History and Theory of Heredity
(Proc. Roy. Soc. Edin., 1889), where the writer gives
his reasons for not accepting Weismann's extreme
views, and E. B. Poulton's Theories of Pleredity (Mid-
land Union of Natural History Societies, 1889). The
latter seems more favourably disposed to Weismann's
theory, which he has greatly contributed to spread
in England through his excellent translation of the
Essays on Heredity.

LECTURE V

Summary :— Experimental Evolution based on the four preceding
Groups of Facts. These Facts illustrate at the same time its
Methods, which are : Change of Environment ; Use and Disuse ;
Natural Selection ; Sexual Selection ; and Physiological Selection.
These Factors of Evolution must all be subjected to Ex-
perimental Test in order to show what they can Effect. What is
wanted : A Direct Proof, which all may Perceive and Touch, of
one Species (or Form) giving Birth to another more or less
Different, and Permanent. Numerous Accessory Problems to be
Investigated at the same time. Scientific and Practical Import of
this Line of Investigation. Requirements : Farm and Laboratory ;
Animals and Plants ; Time ; Experiments must be able to last
20, 50, IOD Years or more. This Experimental Investigation
must and shall be performed. But who is to begin ?

WE have thus shown that a high degree of varia-
bility exists among animals and plants in the natural
state as well as under domestication, and that through
the modification of environment, in part or in whole,
we are able to determine some changes in organisms.
This variability is met with in all parts of the body,
even in those which seem to be the most permanent.

What does this demonstrate ? it may be asked.
And the objection arises : What does it matter that

LECT. v USE OF FOREGOING FACTS 227

variability occurs in all animals and plants, even to
a large extent ? Of course, if all parts of any animal
or plant were to vary to the extent which has been
shown, variability might explain the production of
new species ; but do they really vary to this extent
in any one individual or group of individuals ?
Certainly not, and we must admit that variability is
limited, and that it is not, so far as we know, sufficient
to create new species. The differences are not
numerous enough.

What, then, is the use of the series of facts which
have been examined, and what do they show ?

They provide a basis for the study of variation,
specific or otherwise, in showing that no species are so
very permanent in their structure or functions that no
departure from their type is possible. They form the
solid ground on which evolutionists stand, and
if this ground were missing the evolution hypo-
thesis would have no support at all, and would be
nothing more than an aerial and unfounded structure.
In the second place, they provide the basis and suggest
the methods for experimental transform ism.

Believing as we do that transmutation or evolution
must have taken place under the action of natural
causes and influences, we consider that these causes
have been natural selection and environment, in pro-
portions which we cannot determine. But these causes

Q 2

EXPERIMENTAL EVOLUTION LECT.

cannot have had any influence if the species do not
admit of some variability ; and this very variability
itself we consider as being in some degree the measure
of their operativeness and influence.

We are thus impelled to conclude that transformism
admits of experimental investigation, and this is the
main point we wish to establish. If the present species
have really originated from the more or less closely
allied species which have lived in the past, if the
present has really been evolved out of the past through
natural agencies, without any special intervention
of any force, we do not see why there might not be in
the future forms evolved out of the present, and why
we could not evolve them ourselves, in part, and help
towards their production, through the use of the
methods which we believe to have been used by Nature
herself. If we do not succeed, we are either mistaken
in our general idea, or mistaken in regard to the
methods through which evolution is supposed to have
taken place ; but we can really draw no conclusion at
all as concerns these methods, as long as we have not
subjected them to experimental test.

I do not propose to show all that can be done in
this line ; the matter would require more time than I
can devote to it, and on the other hand I am firmly
convinced that much is to be done of which we have
at present no idea at all. As Dareste rightly says :

FACTORS OF EVOLUTION 229

" We may rest assured that the execution of experi-
ments will cause a great number of questions to arise,
of which we can at present have no idea. This is one
of the great advantages of experiment. If we do not
always find what we are seeking after, while starting
from hypotheses which the facts do not support, we
often find what we were not looking for, and light is
thus cast on regions which till then seemed buried in
complete darkness."

This I consider as exactly true, and many unexpect-
ed questions will certainly turn up of which we have
no idea, while answers to others may also be found.
But, if it is impossible to state exactly what will be
done, we may at least gather some idea of the principal
methods and hints of experimental transformism.

The methods first.

What can the methods of experimental trans-
formism be ? The only answer to this question is
based on the consideration of what the Factors of
Evolution are or are supposed to be. At the present
moment five are usually recognised.1 I quote from
Le Contc's able paper of recent date :

" First. Presence of a changing environment affect-
ing functions, and functions affecting structure, and the
changed structure and function inherited and integ-
rated through successive generations indefinitely.

1 Cf. Herbert Spencer's Factors of Organic Evolution, and Le Conte's
The Factors of Evolution in The Monist, April, 1891.

230 EXPERIMENTAL EVOLUTION LECT.

" Secondly. Use and disuse of organs reacting on
growth-force, and producing change in form, structure,
and relative size of parts, and such change inherited
and integrated through successive generations.

" Thirdly. Natural selection among individuals of
a varying progeny, of those most in accord with an
ever-changing environment, or, as it has been other-
wise called, survival of -the fittest in each successive
generation.

" Fourthly. Sexual selection. The selection of females
among varying male individuals, all competing for the
possession of the strongest or the most attractive.
Among mammals the selection is mainly of the
strongest as decided by battle ; among birds, of the
most attractive, as determined by splendour of colour
or beauty of song.

" Fifthly. Physiological selection, or selection of those
varieties, the individuals of which are fertile among
themselves, but sterile or less fertile with other varieties
and with the parent stock. This has also been called
segregate fecundity by Gulick, and homogamy by
Romanes."

These five factors are not all recognised by the same
group of evolutionists. The two first factors are
Lamarckian ; the third and fourth are Darwinian ; the
two first are supposed to operate during individual
life ; the third and fourth operate on the offspring,

v FACTORS OF EVOLUTION 231

which has more or less departed from the parental
type. For some time an important discussion has
been carried on, especially in England, Germany, and
the United States, concerning these factors between
Lamarckians and Darwinians, as to their efficiency
and frequence.

I cannot enter upon the discussion, which would
require much time, and in fact it might seem rather
early yet to discuss the quoinodo of a fact whose exist-
ence is not proved to the satisfaction of all whose
opinion is of any weight. Lamarckian views arc held
especially by American and some French evolutionists,
while in England and in Germany strict Darwinian
theory prevails. It must be said, however, as concerns
the Lamarckian theory, that, as Lc Conte has well
remarked, the Lamarckian factors of environment and
use and disuse, arc the most fundamental in importance,
and first in order of appearance. Selective factors are
conditioned by reproduction, and on sexual reproduc-
tion particularly in which the characters of two diverse
individuals are blended in different proportions in the
individuals of the same progeny; sexual generation
thus provides material for selection to operate upon.
But where no sexual generation occurs — and this is the
case with the lower forms of life which were first evol-
ved, and out of which the higher forms are supposed
to have developed — Weismann urges that selection is

232 EXPERIMENTAL EVOLUTION LECT.

impossible, since the progeny is nothing more than a
part of the parent form, an outgrowth thereof, the two
being so very similar that in most cases none can tell
which is the parent, and which the progeny. It then
results — if really no selection can occur when sexual
reproduction is wanting, and this is a matter which is
not settled by Weismann's very sweeping assertion,
with which I cannot concur, as there is no reason
why some degree of variability should not exist in
unicellular organisms as well as among multicel-
lular plants or animals — that Lamarckian factors
must have operated, and must operate even now, if
evolution has existed from the beginning, and has
been carried on through natural agencies. Weismann
strongly argues that at present, at all events, or as
concerns higher animals, the Lamarckian factors are
possessed of no influence, and his essays on heredity
are all against the heredity of acquired characters.

Such is the present state of the question. I have
no intention to discuss the matter, as I have already
said ; but I think it may be in the future discussed in
a much more profitable manner than has been done till
now. And this may be effected through experimental
transformism. If we are to subject the evolution
theory to the test of experiment, we can only do so by
the investigation of the efficiency of the factors of
evolution, and we must subject them to the said test.

v PROPOSED EXPERIMENTAL INVESTIGATION 233

This method cannot fail to be highly profitable to the
discussion ; I do not think of any other that, at present,
can settle the matter ; and if we are to know some-
thing some day about the general fact of evolution,
and the methods through which it has been going on,
and may in future go on, it is through experiment
that our knowledge will be acquired.

Whatever our opinions may be as to the real value
of the factors of evolution which have been suggested
on different sides, all must be subjected to the same
test, that of experiment : the results will allow us to
decide upon the theory itself, and upon the details of
the process.

Such is the general view. As to details, now, I
must confess that we are rather in the dark as yet. At
first we shall have to grope about somewhat, search-
ing for the ways in which the experiments may be
performed, and for suitable organisms upon which we
may experiment. Every one of the recognised factors
must be investigated.

Concerning environment, we may operate on many
sorts of animals and plants. A first and simple
method will consist in transferring animals and plants
from one country to another, or from mountains to
plains, or vice-versa, from dry to moist soil, from cold
to warm, from calcareous to siliceous soil, from one
pond in one sort of soil to another pond in another

234 EXPERIMENTAL EVOLUTION LECT.

soil, from light to semi-darkness, from land to water,
&c. The experiment may be performed in a thousand
ways, and all external differences, all changes in
environment which seem to operate on organisms
may be successively tested. Care must be taken,
however, to watch the experiment without interfering,
and the animal or plant must be left wild, without
domestication or cultivation, so that they are exactly
in the condition of a species transferred from one set
of conditions to another without being particularly
helped to support the change. Other experiments
may be performed in a different manner. Instead of
altering slightly all conditions of environment as in
the preceding case, we may alter only one : for
instance, while keeping the animal or plant in its
native climate, alter the proportion of chemical com-
ponents of the soil, alter the nature of food, add some
new compound to the one or the other, increase or
decrease motion around it, &c. All the facts men-
tioned as illustrating the influence of environment
show how numerous and varied are the experiments
which may be performed, and it is needless therefore
to repeat what has already been said on the matter.
If the variations of environment have really effected
the result noticed, such result must be again obtained
by direct experiments.

The fact is however, that in such experiments, the.

v PROPOSED EXPERIMENTAL INVESTIGATION 235

difficulty lies not in the experiment itself, but in
appreciating the results. Such results are not always
external and obvious ; many are internal and require
chemical and microscopical investigation in minute
details, and such differences in chemical constitu-
tion or in structure may have a great influence in the
struggle for life and operation of natural selection.

In reference to use and disuse, experiments may be
made to diminish or suppress the activity and use of
some organ, by keeping plants or animals in such con-
ditions as to render some character useless. For
instance, one might try to obtain unscented or plain
flowers through artificial fecundation of all the flowers
of the same plant which require insect-intervention,
as it is supposed to have developed scent or colour in
view of attracting insects. Or again, place any animal
in such conditions as to render any one function use-
less ; or also, such as to render the development of
some organ or function of great use and necessity.
Experiments on the inheritance of mutilations may
be repeated at the same time : those which have been
already performed have not been successful nor
sufficient, although a priori it seems most likely that
the result will be exactly what it has been. For
such and other experiments bearing on the question,
intending experimenters may be referred to the essays
of Weismann, and W. P. Ball's Effects of Use and

236 EXPERIMENTAL EVOLUTION LECT.

Disuse, where they will see what has been done and
what may be attempted. Care should be taken to
operate preferably on useless characters. But are
there any useless characters ?

It is a rather curious fact that while the operation of
selection is recognised by most evolutionists, even if
holding Lamarckian versus Darwinian views, but few
experiments, as such, have been yet performed,
although observations are plentiful. Among the best
which have yet been made, I must refer to those
of Vilmorin,1 performed many years ago, and
published for the first time in the Transactions oj
the Horticultural Society in 1840 (2nd Series, vol. ii.,
p. 348). M. de Vilmorin, considering that most of
our food-vegetables are derived from species which
have been altered by man, and that the most interest-
ing point to investigate is the methods through which
the alteration has been obtained, notices the fact
familiar to all, that while species which have been
a long time under cultivation vary easily and in many
directions, those which have been less cultivated, or
have not been cultivated at all hardly exhibit an)'
variation. Such has been the case with this writer
in his experiments on Lactuca perennis, on Tetragonia,
on Solanum stoloniferum, on Brassica orientalis. But

1 See his Notice sur f Amelioration de la Carolte Salvage in Notices
sur t Amelioration des Plant es par la Cuttitre, Paris, 1886.

EXPERIMENTS ON SELECTION 237

in the case of the wild carrot circumstances have been
quite different, and through selection, artificial of
course, he has obtained very precise and interesting
results which it may be useful to quote here.

In 1832, M. de Vilmorin, wishing to obtain from the
wild carrot plants with thick and edible roots, planted
some seeds of the wild plant. All the plants thus
obtained grew quickly and yielded seed, while no
root was any better than that of the common wild
carrot. He began again in 1833, and among the seeds
planted, many were late in germinating and no seed
was produced, while some roots were somewhat larger
and thicker than usual. These roots he selected and
put apart so as to plant them in the following spring,
and they yielded seeds in 1834. The seeds were
again planted in 1835. Many gave plants with the
ordinary wild carrot root, but a rather large proportion
(-J-th) yielded plants with thicker roots. The seed of
these plants was selected, and planted in 1836. Selec-
tion again was performed, so that in 1837 many good
roots were obtained. In 1838 and 1839 the process
was continued, with the result of yielding a large pro-
portion of satisfactory carrots (T%ths). While acquiring
different dimensions, the roots acquired also unusual
colour : yellow, lilac, and even red.

Here we have a good instance of the selective
process and of its influence and operation. Another

238 EXPERIMENTAL EVOLUTION LECT.

is yielded by experiments on the beetroot, performed
some years later by the same writer, with the view of
obtaining a variety of this plant containing more
sugar than is commonly the case.1 It is worth
recording, as it shows that through selection it is
possible to influence physiological variability, and the
result has been to increase the proportion of sugar
from 10 on an average to 12, 14 and even 16 per cent.
M. de Vilmorin notices a fact which it is well to state
here, when he says that it is better to select seeds from
plants belonging to a group with high average than
from plants yielding high maxima but also low
minima.

A large number of facts from observation confirm
these results of experiment. Our domesticated
animals, our cultivated plants have been made to yield
so many varieties simply through selection. While
cultivation or domestication increases the tendency
towards variation as we all know, selection of
variations has led us to produce quite a number of
varieties of which we make use in very different
manners, because different variations have in turn
been selected according to the particular wish of
the selectors, or to the peculiarly interesting nature

1 Note sur un Projet if Experience ayant pour but tfaugmenter la
Richesse saccharine de la Betterave. Loc. cit. (1890), and Note sur la
Creation June nouvelle Race de Betterave a Sucre. Loc. cit. and Comptes
Rendus, Nov. 1856.

EXPERIMENTS ON SELECTION 239

of the variation. On this point I shall merely refer
those who desire more information to Darwin's book
on variation : instances are there most numerous and
convincing, as concerns animals and plants, and are
enough to show the power of selection. I may also
refer to some recently-noticed cases. One con-
cerns the production of a new variety of hornless
oxen. In 1874 a Sicilian farmer noticed among his
herd a young bull which had no horns at all. This
young bull was allowed to mate, and the result has
been the production of other hornless animals, so that,
by selecting at each generation the progenitors of the
following this farmer has obtained a hornless variety.
A similar fact occurred in 1 86 1 in a village of the
Mouse department. A cow gave birth to twins, male
and female, deprived of horns : they were mated
together, and thus, by constant selection of hornless
animals as progenitors, a hornless variety has been
also created. The breed of Mauchamp sheep has
similarly been evolved out of a ram which was born in
1828, in the Mauchamp farm, with the peculiarity of
bearing an even wool, instead of having it frizzled,
merino-like. And M. Cornevin, from whose work I
abstract these facts remarks that any day any
breeder in the south of France can, if he chooses, pro-
duce by simple selection a variety of sheep with four
udders, for these animals often bear four of these

240 EXPERIMENTAL EVOLUTION LECT.

organs. From what we have seen, and that which
has been done, purposely or unconsciously by man,
we may infer that every possible variation may be
permanently consolidated as a normal and fixed
character, through selection, through the choice of
progenitors based on the similarity of the character
which it is required to render permanent.

Some points concerning selection require a passing
notice.

In the first place, scientific investigation being the
only aim, the only point in view, it seems advisable to
undertake the study of the influence of selection — be
it on animal or on plant — without any particular fore-
thought at all. I mean by this that such investi-
gations should be begun without any view of obtain-
ing a variation and variety in any particular direction.
For instance suppose Lysimachia nummularia —
I quote the first name which occurs to my memory,
without the slightest choice among those which
come with it — is made the subject of an investigation
in selection. Well, it would not do to decide before-
hand to seek for a new variety having such or such a
peculiarity in the roots, or stems, or leaves : one
should merely cultivate the plants, and if among them
some offered any interesting or curious variation in
any part whatever, one ought to begin the process
of selection, and try to consolidate in the progeny

V EXPERIMENTS ON SELECTION 241

this particular variation. This method offers the
advantage of opening a wider field to investigation,
and on the other hand, animals or plants which,
through culture have been brought to vary in any
direction, are more apt to vary in the one particular
direction which may be desired. Even in cases where
one particular variation is desired in order to create
a special variety, de Vilmorin rightly advises as
follows : — " In order to obtain from a yet unmodified
plant, varieties of a determined character, I would
strive at first to make it vary in any manner, and
would choose, as progenitors, not the accidental
variation which would most nearly approach that I
am seeking for, but merely the one which offers the
largest departure from the type. In the second
generation, I would again select as progenitors the
plants which are most different from the normal type,
and, at the same time, from the progenitors selected
in the previous generation."1 In fact, as Vilmorin
says, we must try to craze the plant, to make it vary
as much as possible, in all possible directions ; and it
is only when this result has been obtained that it
becomes advisable to select the variations in the
desired direction.

We should always remember that plants and

1 Note snr itn Projet d^ Experience ayant pour but de creer ntie
Variete d* Ajonc sans Epines. Loc. cit. p. 35.

242 EXPERIMENTAL EVOLUTION LECT.

animals may vary in a large number of directions, that
variability increases with variation, and that any
desired variation is more apt to occur among plants
whose tendency to variability generally has been
considerably increased through the process which has
been mentioned. And then also, it is well to
remember that while proceeding in this manner,
though we may not meet what we desire, we may
meet with very unexpected variations which may
prove of even greater interest than that which we are
seeking.

In the second place one must not forget that in
experiments of this kind, especially with wild or
uncultivated plants, a long time is sometimes required
before any important variations occur ; the species
seems for a long period to resist all inducements to
variation, and then, all of a sudden, it begins to vary
considerably and in many different directions.

So much for experiments on selection. While
speaking of selection, a word may also be said of the
method which is in some sense exactly the reverse of
selection ; I refer to crossing. While in the course of
selection progenitors are chosen among the animals
which are the most similar to each other, in that of cross-
ing, on the contrary, the progenitors are of different
type, and crossing is performed in order to obtain
animals or plants — which combine the character of

v EXPERIMENTS ON CROSSING 243

both parental forms. In natural conditions, crossing
occurs both among animals and plants, although,
generally speaking, among animals at least, there is
a marked tendency against the mating of unlike, and
towards that of similar animals. It has even been
noticed that in the same town — I have heard of the
fact in Florence — the pigeons congregate in flocks
according to their colour, and keep together, and mate
together, while they seldom do either with the pigeons
of a different flock. In many cases, crossing gives
origin to hybrids which are unable to reproduce their
own form, so that the process is not of much use if
new varieties are required. In other cases, however,
the varieties produced by crossing are fertile inter se,
and it must be noticed, that when crossing does not
seriously impair or totally destroy fertility, it increases
it in a marked manner. It is on account of this
increase of fertility that crossing is often resorted to by
breeders or agriculturists, and this increase has been
demonstrated by Darwin for plants, and observed
by many persons in animals. Cornevin quotes an
instance when a flock of sheep yielding 6°/0 twin
births had its percentage increased to 1 3 through the
introduction of a ram of different breed. The same
is true of hogs, of pigeons, and other animals.

If crossing is to be used in experiments on Evolu-
tion some points must be particularly attended to,

R 2

244 EXPERIMENTAL EVOLUTION LECT.

Observation has shown that crossing is beneficial in
some cases only, and many persons have spoken
unfavourably of it. This is doubtless due to the fact
that we are yet ignorant of some conditions which are
of high importance in the matter, and it would seem
that facts of apparently little significance have a great
deal to do with the ultimate result. Fertility and
sterility may be induced by very feeble external
agencies, and at the beginning results may be obtained
in crossing, which are quite unfavourable, and quite
unlike those which are obtained later on. On the other
hand some conformity must exist between the plants
or animals between whom the crossing occurs. When
it does exist — and, in fact we hardly know when and
where it does or does not — the results may be un-
favourable in that the characters of the parents, though
apparent in the progeny, are not blended together, as
was expected ; they are separate, and may be seen side
by side instead of being combined. Such is the case,
for instance, when white-seeded peas are crossed with
green-seeded varieties ; in the progeny green peas arc
met amidst white seeds, some seeds are green striped
with white ; none are between green and white.
Similar instances are met with among animals when
among the progeny of the same parents, some exhibit
the character of the one, and others those of the other
parent. Another point which requires consideration

v EXPERIMENTS ON CROSSING 245

is the fact that of the two progenitors in an intended
crossing the one is generally — as a variety — possessed
with stronger hereditary tendencies than the other,
and the result is that the progeny takes more after
one of the parents than after the other. For instance,
in the crossing of the Angus bull with the Dutch cow,
the progeny has more characters of the former than of
the latter, and among plants, according to Cornevin,
Vitis rupestris is said to transmit its characters very
markedly when crossed with other varieties.

Such varieties or individuals display what may be
called predominant heredity ; by this is meant that in
crossing the hereditary tendencies of one parent lord
it over those of their mate. This is true of females
as well as of males ; it does not seem to belong to
the one sex more than to the other, and among horses
and oxen Eclipse and Duchess have been renowned
for the predominance of their own qualities over that,
of their mates. Among plants, instances also occur,
and are well known, although in many cases horticul-
turists vainly strive to find individuals thus endowed.
Many have sought to discover Ulex europaeus devoid
of spines, able to transmit this peculiarity to their
progeny — this would be a very valuable conquest, as
Ulex europaeus is good fodder but requires to be
crushed so that the cattle do not injure themselves —
but none have obtained it yet. And this is but one

246 EXPERIMENTAL EVOLUTION LECT.

instance among a thousand. Why, and how it is that
some individuals are thus endowed, we know not. It
must be noticed that the pre-eminence of one of the
progenitors, as a race or variety is not constant ; while
variety a for instance, possesses stronger hereditary
tendencies when crossed with b and r, its tendencies
are overpowered by those of d in a crossing with this
variety ; and in order to ascertain exactly or more
accurately the relative energy of these tendencies, many
systematic crossings would have to be made. This
pre-eminence of one of the progenitors over the other,
in regard to the character of the progeny may in some
cases be so considerable that no difference is apparent ;
it would seem that no crossing has been made and
that both progenitors belong to the same variety.1
As M. C. Dareste 2 rightly observes, " in the present

1 It may happen, however, that the difference, as concerns external
characters, is well marked, but then one marked physiological feature
may be transmitted from one of the progenitors to the hybrid ; for
instance, M. Millardet, in his Essai sur F Hybridation de la Vigne
(Paris, Masson, 1891), shows that in some hybrids between two varieties
oi grape-vine, the marked immunity of one of the progenitors — the
male especially— towards phylloxera, is transferred to the progeny,
notwithstanding the reverse tendency in the other progenitor. The
same writer notices that when the American variety is used as male,
immunity towards phylloxera is considerable, while the amount of
fruit produced is smaller ; the reverse obtains when the American
variety is used as female. Similar facts have been observed by Th.
Niebnei, Die Rose, Berlin, 1880.

2 Noiivdle Exposition d'un Plan d' Experiences sur la Variabilite
des Aniiiiaux, p. 16 (Bull. Soc. Zool. Acclimatation, 1888).

v FORMS OF HEREDITY 247

condition of science it is nearly impossible to foresee

what will be the results of a crossing But we

may assert that this method will yield very interesting
results, and all the more so that the crossed varieties
will be more dissimilar."

This is quite true, and we cannot wonder at it when
we consider how many different forms heredity is
able to assume. Accepting Cornevin's recent classi-
fication, we recognise the following modes :

1. Predominant or Unilateral Heredity ', where the
hereditary tendencies of one of the two mates appear
predominantly or exclusively in the progeny.

2. Bilateral Heredity. Here the progeny has
characters of both progenitors ; and it seldom, if ever,
happens that the progeny has both sorts of characters
to the same degree, or in the same proportion ; one of
the progenitors has more influence than the other.
Both sorts of characters may fuse and combine
together; white and black begetting gray for instance ;
or may coexist, remaining separate, the progeny
having some traits of the father, and others of the
mother. In this sort of heredity four cases are possible :
Heredity is Direct or Crossed, Equal or Unequal.
These terms require no explanation.

3. Atavistic Heredity, or Retrogression, which may
also be direct, crossed, or collateral. In this case the
predominant characters in the progeny are charac-

248 EXPERIMENTAL EVOLUTION LECT.

ters belonging, not to the progenitors but to their
ancestry, near or remote. Many anomalies in organ-
isation are but reversions to former ancestral types ;
and reversions exist to a less degree in the many
cases when a child, for instance, resembles his
grandfather or great-grandmother by some marked
peculiarity instead of possessing the traits of one of
his direct progenitors.

4. Indirect atavistic Heredity ', or Heredity tliroiigJi
Influence. An instance will explain this form. Lord
Morton caused a mare to be mated with a quagga ; she
gave birth to a striped hybrid. Mated the following
year with a thoroughbred, her progeny was again
striped, although not hybrid ; and this occurred three
following years, although she was but once mated with
the Quagga. The influence of the latter — and we do
not know what we exactly mean by influence in this
case — had incorporated itself as it were, in the mare's
organism so deeply as to make itself felt even three
years after. Such cases are met in human marriage.
They are, as yet, unexplained, but they are occasion-
ally met with, and positively ascertained.

5. Homochronoiis Heredity. This term applies to
cases where psychical or physical peculiarities put in
their appearance among the progeny, at the age when
they appeared among the progenitors. Many patho-
logical tendencies are transmitted after this mode, in

v FORMS OF HEREDITY 249

man as well as in animals, and this form of heredity
may be direct as well as crossed.

6. Re inverted Heredity. The progeny may, at first,
and during some time, closely resemble one of the
progenitors, and later on, resemble 'the other.

7. Homotopic Heredity. In this case, a given
peculiarity of one of the progenitors is met with in
the progeny exactly in the same part of the body as
in the former ; for instance, a differently coloured
lock of hair, or a naevus maternus similarly placed in
progenitors and progeny. This form may be also
direct or crossed.

8. Heterotopic, or Homo/list Heredity. Peculiarities
in one part of a progenitor may be transmitted to
other parts (made of similar tissue) in the progeny ;
the same disease, for instance, may assume one form
in progenitors, and another in the descendants.

The natural sequel to experiments in- crossing will
be experiments in hybridisation, that is, crossing
between distinct species. New hybrids must be
obtained, and the number of those which are fertile
inter se must be largely increased. And then, will the
latter hybrids form permanent varieties or species ?
Experiment only can decide. And while experiment
and artificial impregnation may go a long way in
creating entirely new and unexpected forms of life,
which may be of great interest, particular attention

250 EXPERIMENTAL EVOLUTION LECT.

must be paid to the production of hybrids under natural
conditions. This study of hybridisation, scientifically
conducted, will certainly yield very useful results in
being conducive to experiments concerning that very
marked variability in the reproductive function which
in so many cases determines sterility where fertility
might have been expected, while fertility occurs where
sterility would have seemed natural. It seems that
the process of impregnation is of the most delicate
sort, and very slight circumstances — slight they seem
at least — determine its success or failure. Investi-
gation of these circumstances cannot but prove
profitable.

Many experiments may also be performed in regard
to sexual and physiological selection, which are con-
nected with those on crossing and hybridisation, and
Mr. Romanes has already suggested some.

Such are, briefly stated, the methods of experimental
transformism. I sincerely hope and expect that some
years hence, perhaps when all of us shall have become
things of the past, the lecturer who shall have
assumed the pleasant task which I here fulfil, will
have much more to say on this topic, and especially
will be able to say : " this and that have been done,"
instead of the " this should be done " which is the
somewhat monotonous conclusion of each of these
lectures.

v AIMS OF EXPERIMENTAL EVOLUTION 251

And now, what are the aims of experimental
transformism ?

As stated, from the beginning, we wish to test the
theory of evolution, as applied to living beings. This
is the main object : but I wish to call your attention
also to the practical and utilitarian results which may
be expected and attained. As you all know, most, if
not all, of our garden vegetables and plants are the
result of man's industry, and in the cases where the
original wild form still exists, we can well measure the
distance between Nature's product and the perfected
form shaped by man, and best adapted to his needs.
And if man had not undertaken the task of bettering —
bettering meaning here simply adapting more ade-
quately to his needs — Nature's work, many of our im-
portant foods would not have existed.1 The same is
true of animals. Compared with our domestic animals
the wild forms sink in insignificancy as concerns useful-
ness, and here again man has been a most potent
factor in creating out of the raw material those useful

1 Cf. Asa Gray : Were the Fruits made for Man or did Man make the
Fniits? (American Natural, vol. viii., p. 116.) The veteran botanist
here showed that while some fruits and vegetables have hardly departed
from their original wild type (huckleberries, cranberries, persimmons,
etc. ), others have been bettered and rendered more useful by cultivation
(currants, gooseberries, raspberries, blackberries, chestnuts, straw-
berries), while others have been so much perfected as to represent new
fruits (apple, pear, peach, etc.). He adds a list of fruits which man
should endeavour to render more perfect for his own needs.

252 EXPERIMENTAL EVOLUTION LECT.

allies which provide him with meat, milk, wool, or
energy. But, since man has been able to do what he
has done, while devoid of knowledge and unconscious
of methods, what may he not expect to perform now,
with larger means, more varied resources, many
centuries of accumulated science, and the certainty of
success if he is persevering enough ? The past is a
promise for the future, and the results already obtained
well show what we may attain to ; the whole thing
rests in our hands. Are we to believe that among
the unnumbered species of animals and plants which
are yet living in the wild state, none remain which may
be cultivated or domesticated ? Has all been done that
was possible ? No naturalist would venture to answer
yes, and to say that man has reached his Pillars of
Hercules. We are then entitled to expect many
useful discoveries if we only set to work, and the field
which lies open to us is infinite. Both organic king-
doms may be made to yield any number of new forms
whose use we cannot even foresee, so short-sighted
are we ; and even if we were only to increase the
number of the useful animals or plants, without varying
the use to which either may be put, a great deal would
doubtless have been done for the benefit of mankind.

But this cannot happen if we do not purposely set
to work. In former times, when man lived in small
or large tribes, widely separated, without easy means

v AIMS OF EXPERIMENTAL EVOLUTION 253

of intercourse, it was necessary for him to attend at
all costs to his cultures and herds ; it was a matter of
life or death. Now, our most civilised nations are
unable to produce all they need ; some work in one
line, some in others, and by cooperation and exchange
every one is provided with the things he needs, and
none feels the necessity of creating new resources.
But civilised man must be made to understand that he
can considerably increase the latter if he chooses. Such
is the practical interest of experimental transformism,
and it can in no possible manner interfere with its
scientific aim ; both are bound together.

As to the latter purpose, I must be content with a
few words on the principal lines of investigation. Our
main aim must be the study of evolution, that is of
the derivation of living forms from each other, and
the study of natural influences on the process of this
derivation. If the evolution hypothesis is true, we
must find that new forms of life may be evolved out of
pre-existing forms, by means of influences actually
operative in Nature, without man's or any other agent's
interference. Of course, in experiments on evolution,
man must interfere, but he does so only in order to
test the real efficiency of what he considers to be the
factors of evolution.

This general line of investigation is not a simple one ;
a large number of questions are intimately connected

254 EXPERIMENTAL EVOLUTION LECT.

with it, and cannot be separated, concerning which
information will be most valuable, from the practical
as well as from the scientific point of view. Some of
these questions may be briefly indicated.

First the question of variability in species, or other
groups, and how they are established. External and
internal or physiological variability must both be in-
vestigated anew, with the most delicate tests and
methods, and particular attention must be directed to
their causes. Of course, this study implicates that of
species. What is a species ; what are specific charac-
ters ? If we consider many of the recognised species,
we see that these characters are often of the most
insignificant sort, and that many of the so-called
specific characters are even of less value than those
which are used to distinguish varieties. It may be
predicted that terrific discussions will arise concerning
this vexatam questionem, which seems to become more
intricate every day, and that much sorrow will befall
that numerous and well-disposed class of systematists,
whose self-assumed task in life seems to be to in-
crease the list of specific forms. Perhaps we shall
thus understand what really makes a species ; for
while we talk much about them, we really do not
understand what they are, and no thorough definition
has yet been given.

The problem of heredity will also be investigated,

v AIMS OF EXPERIMENTAL EVOLUTION 255

What is heredity ? how does it operate ? what is
transmitted ? We hardly know anything on the
matter ; we all have read a number of anecdotes of
more or less unscientific character, and remain in the
dark. Weismann's solid and heavy essays are cer-
tainly valuable, but facts must be added to reasonings,
and the facts we need are mainly experimental. The
whole problem requires a thorough investigation, al-
though many facts are already ascertained, a great
deal remains to be done to explain heredity, and
to ascertain its limits and power. One important
question is that of the heredity of Abnormalities and
Mutilations. Many abnormalities, when not opposed
to the continuation of life, are hereditary.1 A good
instance is provided in the case of the cats, mentioned
by E. B. Poulton (^^^,1883-6), and in the case of the
Fodli tribe, in Arabia, where all the individuals, since
very ancient times, have been born with twenty-four
digits instead of twenty, and where they all marry
within the tribe.2 Many diseases are hereditary, under

1 Paul Bert must be included among those who have somewhat
investigated the subject, after Philipeaux, Bronn, and many others.
He observed that if the eyes of young, newly-born rats are re-
moved, death always ensues when the experiment attains the fourth
generation, doubtless, says he, through some impairment of the optic
lobes. Cf. his Essais cf Experience sur la Transmission hereditaire de
certaines Lesions chirurgicales ; Relations trophiqnes entre les Yetix tt
les Lobes optiques. Comptes Rendus Soc. de Biologic, 1870.

2 Aira, Bull. Soc. Anthropelogie, 1886,

>56 EXPERIMENTAL EVOLUTION LECT.

the same or a different form. And finally comes that
much-discussed question of the heredity of muti-
lations, negatively settled by Weismann, but which
certainly requires much new investigation. On
hybridism, sexuality, and many other points, useful
facts will be discovered ; in fact, as has been said,
we cannot exactly foresee the subjects which will
naturally offer themselves to our investigation.

But there is enough to be done, even if experiment
were to suggest nothing new, and the field which is
opened to experiment, in the lines briefly indicated
above, in the line of the investigation of organic
evolution in its general sense, and in its details, is
simply unlimited.

All these experiments can be made on any animals
and plants, and in any country. What is required
for their execution is an institution of some sort
specially devoted to this line of investigation. It
appears to me that this institution should comprise
the following essential elements : rather extensive
grounds, a farm with men experienced in breeding,
agriculture, and horticulture, some greenhouses, and
a laboratory with the common appliances of che-
mistry, physiology, and histology. Of course this
must be located in the country. It is very important
to have experienced farm-hands, and a good chemist
and histologist are necessary in the staff of the insti-

v A LONG TIME REQUIRED. 257

tution. As to the general management, it seems
advisable to have a director with a board of com-
petent men, whose function would be to decide, after
careful investigation and exchange of views, what are
the fundamental experiments to be performed. These
experiments, when once decided upon, should be pur-
sued during a long period of years, and nothing
should be altered in their execution, unless con-
sidered advisable by the board, or unless the
experiment should be found useless or devoid of
chances of success. The main thing should be to
provide for the duration of this experiment, whether
the originators were living or dead, and to follow it
out for a long time. Time is an indispensable ele-
ment in such investigations, and experiments of this
sort will surely exceed the normal duration of human
lifetime. But, as old Pierre Belon writes in his
Remontrances sur le Defaut de Labour et Culture des
Plantes, 1558 : " II ne se fault pas excuser sur la lon-
gueur du temps pourentreprendrechoses seantesau bien
public." Into the details of the work of the chemists,
histologists, or physiologists, it is useless to enter ; the
mere enumeration of the varied facts which have been
quoted shows that their services are of the utmost
usefulness, and are quite necessary for the investiga-
tion of the results. Any number of experiments of
minor importance may be carried

• UNIVERSITY

VV OF J

258 EXPERIMENTAL EVOLUTION LECT.

time, and surely the fact that they will be performed
under good conditions, in a laboratory specially pre-
pared for such investigations, will contribute greatly
to the final success. The co-operation of many out-
siders might be of great use. Young men might
spend some time — some three, four, or five years, or
more — in attending specially to some of the experi-
ments in course of execution, in the investigation of
some special points. Many friends of science could
also do good work and help greatly by agreeing, for
instance, to cultivate in various localities the same
species of plant, or to co-operate in breeding special
varieties of animals and reporting the results. In
fact, all natural history societies, all laboratories, and
all individuals could undertake a share of work,
and among the individuals, naturalists, horticulturists,
breeders, and pisciculturists would occupy a pro-
minent part. The institution for the experimental
investigation of evolution would thus be the head-
quarters for all that concerns evolution, and its in-
fluence would make itself felt in all departments of
natural history, and thus create a strong current in
the line which, sooner or later, must be opened.

I do not entertain the slightest doubt as to the fact
that it will be opened. The thing must be done. It
is a matter of money — as usual. But in civilized
countries individuals or corporations are occasionally

v EXPERIMENTAL STUDY INDISPENSABLE 259

met who understand that mankind's glory lies not
entirely in the invention of instruments of war and
death, and that there are aims in life higher than mere
money-making or enjoyment. There are two main
aims in life — the benefiting of mankind, which may
be performed in a thousand manners, and the pursuit
of truth. Much money has already been given to-
wards the accomplishment of these two purposes, and
this allows me to hope that some charitable and en-
lightened persons may be found who will be able and
willing to help towards the experimental study of
evolution.

The matter is of sufficient importance when we
consider that, in fact, nothing less is proposed than
an application of experiment to the solution of one
of the highest problems of science, and the one in
which thinking mankind is most interested.

POSTSCRIPT. — Since the above lectures were de-
livered, and even in type, I have had the pleasure
of learning that Dr. Romanes has circulated an
appeal for an experimental institute essentially on
the lines above suggested, which he wishes to see
established in connection with the University of
Oxford. There is also a prospect that the Granton
Marine Station at Edinburgh may be more fully
adapted to some department of this line of research.

S 2

INDEX

A.

Abratnisversicolor, see Stilbe

Aconituat napellits, 142

Acquired characters, 163 ; Weismann
on, 221 seg., 225

Actinia- mescinbryantheiiinui, trans-
ferred to fresh water 187, 188

Actinia plumosa under high pressures,
192

sEqttorea Forskalii, 106

Ailanthiis glandulosa, variation in
sexuality, 109

AIRA, on six-digited tribe of Arabia,
255

Albumen, not identical in all eggs, 66

Alytes, 112

Amblystoma, 112

Amphibians, neotenia among, 110-112 ;
evolution of circulatory apparatus,

Amphicyon, very variable, 150
Amphioxns, gill-slits, 32
Ancylns^ rupicola and thennalis,
varieties of A. simplex ', 93; living
in salt water, 185

Animals, domestication of, 156 ; depar-
ture from wild type, 159 ; brain of
wild and domestic, 166 ; marine
animals in fresh water, 186
Anodonta, living in salt water, 185
Anomalies, muscular, 37; and heredity,

255

Anteater, osteological variability, 104
Antelopes, domesticated, 157
Anthea ccmis, transferred to fresh

water, 187, 188
Anthrax, 124
Aortic arches, 33
APCHIER UE PRUNS, on the influence

of environment on colour, 54
Apples, varieties of, 102
A rchtzopteryx lithographica, 26
Arctia, colour-variation in genus, 51
ARISTOTLE, on differences in animals
from Egypt and Greece, 201

Artemia, salina and milhattsenii,

relationship, 217
Artificial soils, 198
Aspergillnsniger, killed by r^J^th

of nitrate of silver, 182
Aspidistra elatior variegata, 59
Atmospheric pressure, 192
Atractylis genimifera.) 142
A ttacus Pernyi, 195
AUBERT, on caffein, 133
AUDOUIN, on colour-variation, 51
Aurelia aurita, loss of weight through

inanition, 78

AUTENRIETH, on sexuality, 108
Axolotls, 112

B.

Bacillus anthracis, physiological

variability, 127, 223
BACON, on experimental evolution, 43
Balcenidte, 104

BALASCHEWA, on growth, 200
BARFURTH, on sterility, 220
BATALIN (A.), on the influence of com-
mon salt on Salicornta, 212
BATESON, on variation in Cardhim

ednle, 94
BAUDIN, onPisidiujtipnlchelluin and

cinerennt, 94
BAUHIN (G.)i 95
BEAUREGARD, see POUCHET
Beech-marten, formerly domesticated,

156
Bees, changes in colour under change

of environments, 53 ; sex, 107
Begonia Schmidtii, sudden variation,

I52
BEHRENS, on the influence of currents

on aquatic plants, 207
BELON (PIERRE), on time required for

experiments in cultivation and

domestication, 257
BERNARDI, on sexuality, 108
Beroe ovata, loss of weight during

inanition, 78

262

INDEX

BERT (P.)i 9n the physiological limit
to dimensional variations, 76 ; on
adaptation to salinity, 190 ; on
heredity of mutilations, 255

BESSEY (C. A.), on differences of the
flower in different varieties of apples,
102

BEUDANT (F. S.), on transferring
marine forms to fresh water, and
fresh-water forms to sea water, 185

Bidens cernua, variation, 72

Blood, chemical differences according
to sexes, 122

Bones, chemical differences between
man and woman, 121

BONNIER (G.) and FLAHAULT, on the
influence of altitudes on colour, 55;
on the influence of altitudes on form,
96

BOKY DE SAINT VINCENT, 19

BOUDIER, on relation between form and
environment, 95

BOUKGUIGNAT, on possible connection
between electrical phenomena and
left-handed shells, 204

Brain, physiological conditions may be
artificially hastened or retarded, 146

Branchipiis ferox, variations accord-
ing to the mode of life, 216

Brassica olcracea, varieties derived
from it, 177 ; B. orientalis, experi-
ments on selection, 236

BKENNAN (G. A.), on variation in an
individual plant of Tradescantia
I'irginica, 101

BRICK (C.)> on physiology of sea-shore
plants, 212

BRONN, on heredity of mutilations, 255

BROT, on abnormal Lymncea in ponds
containing many Hydras, 204

Brucine, influence on common crab,
120

Buccinnm transferred to fresh water,
1 86

BUFFON, evolutionary and anti-evolu-
tionary views, 17, 18 ; on man's power
over nature, 43 ; tendency towards
degeneracy, 150

Btijo, 112

Brilitmis decollatiis, 74

C.

Calendula arvensis, 75
Caltha palustris, 142
CAMERANO, on neotenia, no
Campanula trachelium, 54 ; C.

rotnndifolia, 55
CAMULOGEN, 220

CANDOLLE (DE), on the origin of culti-
vated plants, 173 ; on the varieties of
Brassica oleracea, 177 ; on light and
temperature, 219

Capparis spinosa devoid of spines, 92

Carbonic acid, its disappearance would
destroy all life, 181

Cardium edule, 94

Carcinus mcenas, 120 ; transferred to
fresh water, 188

Carex ampullacea, difference in aerial
and aquatic leaves, 208

CARRIERS (E. A.), on variegation, 58 ;
on .sudden variegation, 59 ; on dis-
similarly coloured grapes in the
same bunch, 60 ; on variation in the
leaves of the ivy, 98 ; on variation
of sexuality in Ailanthus, 109 ; on
sudden variation, 153

CARRiEREand ANDRE, on variegation,
59 ; on dissimilarly coloured flowers
on the same plant, 60

Carrot, experiments in selection on, 237

Cattle, different flavour and chemical
characters of flesh according to
mode of feeding, 66 ; insular smaller
than continental, 73 ; sudden appear-
ance of hornless, 153 ; Niata breeds,
153 ; Franqueiros breed, 154 ; weight
increased by domestication, 166 ",
length of gestation varies according
to breeds, 167 ; hornless, 239

Cemiostoma caffeoium, 136

Cerithiuin transferred to fresh water,
1 86

Cerviis corsicanus a descendant of C.
elaphus, 73

CHABRY, see POUCHET

Chamcerops hnmilis no

CHAUVEAU (A.), on the greater im-
munity of Algerian sheep towards
anthrax, 124 ; on physiological
transmutation 127, 221

CHAUVIN (MARIE DE), on neotenia, 112

Chemical differences between the bony
structures of different breeds of
sheep, 116; in the percentage of
principal components of the wool of
various breeds of sheep, 117 ; in the
flesh of salmon in normal condition
and after spawning, 117 ; between
different species of the same genus,
118 ; between plants of same species
poorly or richly fed, 118 ; between
bones of man and woman, 114,
121 ; between their blood, 122

Chlorophyll, not identical in all plants,
65

CHOSSAT, on inanition, 78

CHRISTISON (SiR ROB.), on chemical
analyses of salmon betore and afte
spawning, 117

Cicuta. 135

Circulation of matter, 2

Circulatory system, arguments for
evolution, 32

Cirs27i)n anglicwn, form of C. Itilbo-
$11111) 219

INDEX

263

Civilization and domestication, 169
CLARK (J. A.), on colour-variation in

Smerinthus, 51
CLAUS, on variation in ^Eqnorea

,

forskalea, 106
lematis vitalba, 142

CLESSIN (S.)> on the influence of the
movement of water on the form of
molluscs, 207

Climate, influence on colour, 69 ; on
sexuality, 109

Coffea arabica killed by a species of
insects which does not attack C-
liberica, 136

Colchicin, influence of germinating
seeds, 137

Colchiciiin aiitnmnale, 142

Colzas phyllodoce, vitality, 120

Colour, variability, 48 ; in animals,
50 ; food and, 57 ', colour of envi-
ronments, its influence, 58 ; and
hybridation, 64 ; and vigour, 68, 69 ;
and climate, 69

Colour-variation, Linnaeus on, 48 ;
accompanied by other sorts of varia-
tion, 49 ; in fox, 50 ; butterflies, 50 ;
in insects generally, 51 ; cray-fish, 52 ;
worms, 52 ; seasonal, 52 ; chemical
variation underlying colour-varia-
tion, 61 ; influence of light and
oxygen, 220 ; and fecundity, 68

COLUMELLA, 22O

Conium macnlatnm, 140

CONTA (BASILE), on origin of present
forms of life, 9

CONTEJEAN (CM.), on physiological
differences between differently
coloured frogs, 134 ; on differences
in the digestive tract between frog
and toad, 134, 135

Copper (sulphate of), influence on
germination, 137

Coriander, species, 95

CORNEVIN, on modes of variation in
domestic animals, 47 ; on proportion
of sexes in different species of
animals, 108 ; on toxic foods, 135,
136 ; on conditions of domestication,
162 ; on differences in skull-capacity
between wild and domestic forms,
166 ; on differences in length of
gestation according to breeds of
cattle, 167; on differences of
variability among domestic animals,
170 ; on a variety of sheep with
four udders, 239 ; on crossing and
fertility, 243 ; on predominant
heredity, 245 ; forms of heredity, 247

CORNU, on parasitism and sexuality,
108

COSTANTIN, on the influence of aerial
and aquatic life on stomata and
leaves, 209

Cray-fish, colour-variation, 51

Creation Theory, 7
four views, 22
what it implies, 39

Crossing between orange and lemon,
62 ; proposed method of experiments,
242 seq., 249

Cultivation of plants, its modifying
influence, 171 ; should be extended
to new forms, 172 ; origin of culti-
vated plants, 173

CUNNINGHAM, on muscular variability,
105

CuRTiss(A. H.), on dimensional varia-
tions, 72

CUVIER, 19 ; revolutions of the earth, 23

Cyclamen europce-itm, 141

D.

DALIBARD, on variations in the scent
of flowers, 102

DALL (W. H.), on sudden variation,
*5i

DALLINGER, on adaptation, 221

DAMMER (UDO), on teratology, 100

Daphnia degenerata, magna, and
pulex, relationship, 217

Daphnia rectirostris, variations ac-
cording to mode of life, 213

DARESTE(C.)I on experimental terato-
geny, 193^^.. 228, 220 ; on crossing,
246

DARWIN (C.), Origin of Species, 6

Datura stramonhim crossed with D.
Icevis, 62

DECAISNE, on variability in fruit trees,
99

DELAUNAY (G.), on comparative
biology, 123

DELBCEUF, " tendency to better-
ment," 151

DETMER, on the shoots of Thuja
occidentalis, 222

Digestive system, variation, 106 ;
physiological differences between
frog and toad, 134, 135

Dimensional variation, 70 ; in man
and animals, 70 ; in plants, 72 ; in
insular animals and plants, 73 ;
physiological limit, 76

Diphtheria, 124

Disease, racial immunity from 123

Domestic animals, number very small,
157 ; wild forms of, 158, 159 ; varia-
bility is variable, 170

Domestication, 156 ; ought to be ex-
tended to new forms, 160 ; conditions
of, 162 ; as a means of transmuta-
tion, 164 ; and civilization, 169

Doris tiibercnlata transferred to fresh
water, 188

Doryphora decemlineata, 120

Down of plants more abundant in dry
stations, 91

264

INDEX

Dromia -vnlgaris transferred to fresh
water, 188

DUBALEN, on molluscs living in warm
waters, 205

DUGES, on colour-variation, 51

DUNCAN (D.), on toxic foods, 135

DURET (CLAUDE), quaint evolutionary
notions, 14

Dwarf plants, 71 ; elephants, 73 ; dogs,
73 ; rabbits, 74

Dwarfing of Japanese plants, 71 ; and
sterility, 75 ; of Lymntea, and in-
fluence on sexuality, 200

Echium, physiological differences ac-
cording to climate, 115
EDMONSTONE (DR.), on differences in
the structure of the stomach of
Larus according to food, 105
Eels, experiments en the influence of

salt, 190

Elephants, small in Malta, 73
Elodea, 81, 82

Embryology : arguments for evolution,
29 ; ontogeny and phylogeny, 30 ;
arguments from the circulatory
apparatus, 32 ; from the nervous
system, 35 ; from teratology and mal-
formations, 36

Environment, its modifying influence
on organisms, 179 ; a very slight
change may be fatal, 181 ; and de-
velopment, 197 ; and physiology,
201 ; and deformation, 207 ; and
leaf forms, 209; and plant life, 219;
factor in evolution, 229 ; proposed
experiments, 233
Eqnns Prjevalskii, 159
Erica vulgaris, 54
Eiigeron alpinns, 55
Eiionymiis, variegated, 58 ; E. siil-
furea, 59 ; E. ra.dica.ns variegata,
59

Euphorbia, 140
Evolution theory stated, n, 12
historical sketch, 13
proofs : palseontological, 29
embryological, 29
pathological, 36 ; morphological,

38

mental, 41 ; proof wanted, 42
and experiment (Bacon on), 43
factors of, 229

first, change of environment, 233
second, use and disuse, 235
third, selection, 236
Evolution, experimental, aims of, 251
need of, 45

based on three groups of fucts, 46
first, variations in structure, 47
second, variations in colour, 48

third, variations in dimensions, 70
first group of facts supporting it,

46
second group of facts supporting

it, 156
third group of facts supporting it,

170
fourth group of facts supporting

it, 179

Experiment and observation, 180
Experiments proposed on environment,

233 A j-
on use and disuse, 235

on selection, 236
on crossing, 243
physiological, 250

FABREJOU, on the influence of environ-
ment on plants, 96

FAIVRK, on variability, 98

FALLOU (J ), on experimental produc-
tion of abnormalities among butter-
flies, 195

Fertility influenced by external condi-
tions, 221

FILHOL (H.), on variability in palaxm-
tological faunas, 150

FISCH, on proportion of both sexes in
plants, 107

FISCHER, on molluscs living in warm
waters, 205

FLAHAL'LT, See BONNIER ', On the

colour of plants grown from the same
set of seeds under different condi-
tions, 56

Flesh, chemical variations according
to condition of the animal, 117

Flesh, differences in taste and chemis-
try according to the food of the
animal, 66

Flower, variability, 100

FOLIN (MARQUIS DE), on the irregu-
larity of some pond snails, 93

Food and colour, 57 ; and length of
wool, 90 ; and structure of the
stomach, 105 ; and sexuality, 107,
109 ; and chemical composition, 118

Foraminifera, 27

FORCHAMMER, on chemical differences
between different species of the same
genus, 118

Form-variation, 93 ; among molluscs,
93

FOURNIER (G.), on variation among
Cruciferae, 98

Fox, colour- variation. 53

Fresh water, generally but not always
fatal to marine animals, 185

Fruit, variations, 99

Fiicns, chemical differences between
different species, 118

INDEX

265

G.

Galium cruciatum, 55

Callus bankiva, 158

GAUDKY(A.), on palarontological argu-
ments for evolution, 28 ; on varia-
bility among molluscs, 169

GAUTIER (ARMAND), on chemical
variation accompanying colour-
variation in grapes, 61

Gentians, colour-variation, 54

GEOFFROY SAINT HILAIRE, on en-
vironment, 19; on experimental
transformism, 43, 44 ', on dimensional
variation, 74 ; on civilization and
domestication, 169

Geological record, imperfection, 25

Geranium batrachioides, 54 ; G. sylva-
ticum, 55

GERARD, on colour-variation in bees,
53 ; on colour-variation in plants, 53

GIARD (A.), on parasitism and sexu-
ality, 108 ; on parasitary castration,
220

Gill-arches, 32

Glanders, 124

GODRON, on seasonal colour-variation,
52 ; on variation in the form of
Ranunculus leaves, according to
environment, 97 ; on Ranunculus,
97

GOODALE (G. L.), on plants suitable
for cultivation, 172

Grape-vines from the Rhine valley
yield Madeira wine in Madeira, 219

Grapes, differently coloured in the
same bunch, 60', colour-variation
and chemical variation, 63

Grapsus transferred to fresh water, 188

GRATACAP, on differences of resistance
of different insects to various in-
jurious processes, 120

GRAY (AsA), on cultivation and its
results, 251

GRUBER (W.), on muscular variability,
105

H.

HAECKEL (E.), on evolution, 31

Haliotis transferred to fresh water,
186

HARNACK and MEYER, on the in-
fluence of pilocarpin on green and
brown frog, 132

Heat, influence on germinating seeds,
137 ; on different bacteria, 183 :
molluscs living in warm water, 205,
206

Helianthus annuus, dwarfed, 75

Helicidce, dimensional variations, 74

Hellebore, 135

Hemp, proportion of sexes, 107 ; muti-
lated, 108

Heredity, 225 ; predominant, 245, 247;
bilateral, 247 ; direct and crossed,
eq^lal and unequal, 247 ; atavistic,
247 ; through influence, 248 ; homo-
chronous, 248 ; rein-verted, 249 ;
homotopic, 249 ; heterotopic, 249 ;
in general, 255 ; of mutilations, or
abnormalities, 255

HERMBSTAEDT, on the influence of
food on chemical composition of
plants, 118

HKRTWIG (R. and O.), on segmenta-
tion, 197

HEUSINGER, on colour- variation, 67-69

HILGENDORF and HYATT, on the
Planorbis of Steinheim, 27

Hippuris -vulgaris, differences in
aquatic and aerial leaves, 209

HOFMANN, on sexuality, 108

HOLMGREN, on structure of the
stomach and its variations accord-
ing to food, 105

Holothuria cucumaria transferred to
fresh water, 188

HOOKER (SiR JOSEPH), on Tasmanian
species suitable for cultivation, 172

Horse, colour and fecundity, 68 ; do-
mestic forms, 165

HULST, on colour-variation among
Arctias, 51

HUNTER (JOHN), on visceral varia-
bility in sea-gulls, 104

HUXLEY (Tn. H.), three hypotheses
concerning the present world, 7 ; on
evolution, n

HYATT, see HILGENDORF ; on varia-
bility of Planorbis, 149

Hybrids, colour in, 64 ; between grape-
vines, 246 ; new experiments must
be performed, 249

Hydra, possible influence on Lym-
na?a, 204

Hyla, 112

Idiosyncrasy, 125

Immunity, comparative, to different
diseases among different species, 124

Inanition, loss of weight in inverte-
brates, 77

Insular animals smaller than conti-
nental, 73

Integumentary variation, 89 ; in poul-
try, 89 ; in sheep, 89 ; in the length of
the wool, 89 ; in the amount of hairy
covering among plants, 91 ; in the
spines of plants, 92

IRVINE and WOODHEAD, on the pro-
duction of lime by animals, 202

1 'satis tinctoria, 91

Isoetes lacustris, variability, 10

266

INDEX

J-

Jackal, formerly tamed, 157

Jasione montana, 91

JOHANNSEN, on caffein, 133

JONES (RUPKRT), on Foraminifera, 28

Juncussupinus, variation, 98

Juniperus, dwarfed, 71

Jussicea grandijlora, leaf-variatio n,

98
JUSSIEU (DE), on Ulexnanus

KIPLING (LOCKWOOD), on domestic
animals in India, 161

KIKCHEK, on genesis of animal forms,
I4

KRAUS, on growth of fruits during day-
time and night, 199

KROCKER, on the amount of wool
yielded according to the food of
sheep, 91

L.

Laburnum, 140

LACORDAIRE, on colour variation, 51

Lactuca perennis, 236

Lamarckism and Darwinism, 230, 231

LAMARCK'S theory of transmutation,
19 ; on Kamtnculns hederacens
and aquatilis, 97

Lamiumpurpureum, 54

LANGUET DE SIVRY, on environment
.and artificial selection, 203

Larus argentatus, variation, 105

Lams tridactylus, variation, 104

Latent life, 193

LAUDER BRUNTON and CASH, on the
action of theine and caffeine, 132

LAUTENBACH, on the physiological
action of heat on Rana temporaria
and esculenta, 134

Leaves, variation, 97 ; toxicity, 142 ;
variability according to mode of life,
208, 209-212

LEBAS, on the comparison of varie-
gated and non-variegated plants, 59

LE CONTE, factors of evolution, 229

Leeches, colour-variation, 52

LEMAIRE (C.)j on dimensional varia-
tions of hemp, 72

Lepidiiim sativum, 138 ; influence of
fresh and sea water on starch-pro-
duction, 212

LESAGE (P.), on the influence of sea-
shore life on plants, 209 ; influence
of salt water on thickness of leaves,
influence of salt water on starch pro-
duction, 212

Leucochroa candidissima, 74

Lime salts produced by animals, 202

Links, missing, not always required
nor really missing, 152

LINNAEUS, on evolution, 20; on the
influence of environment on the
hairy covering of plants, 91

Lion, formerly tamed, 157

Living world, problem of, three
hypotheses concerning, i

LOCARD(A.), on dimensional variation
among molluscs, &c., 74; on form-
variation among molluscs, 93 ;
L. turgida and elophila as 'varieties
of L. stagnates, 94 ; on variations of
Unto in form and colour, 94

LUCAS, tendency towards production
of new forms, 150

Lycaonpictus domesticated in ancient
Egypt, 157

Lychnis githago unequally toxic for
different species of animals, 141

Lychnis, sexuality, 108

LYKLL (C.), on variability among
molluscs, 169

Lyuintea stagnalis larger in ponds
than in rivers, 74 ; stagnalis and
auricularia artificially dwarfed, 79
seq. \frigida and the) malts varieties
of L. peregra, 93 ; auricularia hav-
ing only four whorls in mountain
waters, 93 ; turgida and elophila
varieties ^stagnalis^i, ; differences
between individuals of the same
brood, 136 ', living in salt water, 185 ;
external influences, 197 ; growth,
200; dwarfing produces unisexuality,
201 ; abnormal in ponds containing
many Hydras, 204 ; deformation by
motion of water, 207

MAGNIN, on parasitism and sexuality,

108
MAILLET (DE), on the origin of man

and animals, 15
Malformations, congenital, their value,

36

MANTEGAZZA, on variation in teeth, 10
MARCACCI, on experimental terato-

geny, 196, 197
Marsh-fever, comparative death-rate

of Europeans and Negroes, 123
MARTINS (Cn.), on variation in

Jnssi&a, 98 ; on sex-variability in

Chamcerops, no
MASTERS (MAXWELL), on teratology,

100
Mauchamp breed of sheep, origin, 154,

239

MAUPAS, on nutrition and fertility, 221
Melia azedarach, 142
MER (E.), on variation in Isoetes

INDEX

267

lacustris, ic6 ; on the influence of
currents on aquatic plants, 207

MII.LAKDET, on hybrids between
grape-vines, 246

MILNE-EDWARDS, on chemical differ-
ences between the bones of man and
woman, 121

MILTON, special creation theory ex-
pounded in Paradise Lost, 7

MIVART, SAINT GEORGE, 103

Moina, see Daphnia

MOLESCHOTT, on the influence of
oxygen on pigments, 220

MONNIER, on the influence of brucin
on green and brown frog, 130

MOQUIN TANDON, on changes in the
colour of plants due to environment,
53 ; on dimensional variations, 74

Morphological argument for evolution,
38

MORTON (LORD), on mating a mare
with a quagga, 248

MOYNIER DE VILLEPOISE, on the pro-
duction of lime by marine organisms,
202

MCLLER, on sexuality, 108

Muscular system, variability, 105

Mutilations and sexuality, 220 ; here-
dity of, 255

MUNTZ and GIRARD, on chemical
differences of the wool of different
breeds of sheep, 117

Myosotis sylvatica, 55

Myriophyllnm, variation, 98

My til us transferred to fresh water, 186

NAEGELI, internal forces tending to
develop new forms, 150

Narcissus, sudden variation, 153

NATHUSIUS, on length of gestation in
different breeeds of sheep, 167

Natural selection (anticipated by
Naudin), 20

NAUDIN, his paper on selection (1852),
20, 21 ; on climate, 55 ; on varia-
tion in fruits, 62 ; on physiological
differences between Echhun of differ-
ent climate, 115 ; internal forces tend-
ing to develop new forms, 150

Nautilus has hardly varied since very
remote epochs, 169

Neotenia in Amphibians, no

Neritina thermophila, 205

Nervous system, argument for evolu-
tion, 35

Niata breed of cattle, 153

Nicotin, influence on green and brown
frog, 132

NIEBNER (TH.), on hybrids between
roses, 246

Noctna, 120

O.

Onopordon acanthiuin, 91
Ontogeny, 30, 35

ORBIGNY (D'), on dimensional varia-
tion, 70, 71

Osteology, variations in, 103
Ostrea transferred to fresh water, 186
Ovibos moschatus, 159
Oxalis strzcta, variations, 72
Oxytropis man tana, 54

P.

Pagiirus Prideauxii transferred to
fresh water, 188

Palajontological argument for evolu-
tion, 25

PALLAS, 159

Paludina living in salt water, 185

Pansy has varied slowly, 149

PASTEUR, 5

Pecten transferred to fresh water, 186

P debates, 112

PENZIG (O ), on teratology, 100

Persicaria, 91

PETERMANN, on the influence of soil
on roots, 203

PFLUGER, on segmentation, 197

Phaseolus vnlgaris, varieties, 177

Phasnta, colour-variation, 51

Phylogeny, 30, 35

Physa contorta, 74 ; acuta, 205

Physiological differences between
plants of same species, but different
climate, 115 ; between different spe-
cies, 119 ; between different species
of insects towards the same external
conditions, 120; between man and
woman, 122 ; between different hu-
man races, 123 ; between European
and Algerian sheep, 124; between
normal and attenuated Bacillus an-
thracis, 127 ; between Rana escu-
lenta and temporaria, 130 seq. ; be-
tween the different individuals of the
same brood, 136 ; between seeds,
137 ; may be experimentally in-
duced, 145 ; between bacteria thriv-
ing only in different media, 183 ',
between plants watered with fresh
and sea water, 211

Physiological transmutation, 127

Physiological variation. 114

Picrotoxine, influence on common crab,
1 20

PIERLOT, on variation of toxicity of
valerian, 136

Pigeons in Florence congregating in
flocks according to their colour, and
breeding together, 243

Pilocarpin, influence on green and
brown frog, 132

268

INDEX

PIKE, on deformation of Planorbis
by life in a pond containing a super-
abundance of plants, 207

Pisidium pulchellum and cinerenm
varieties of same species, 94

Planorbis of Steinheim, 27, 149 ;
living in sea-water, 185 ; deformed
by superabundance of plants, 207

Plants, wild and cultivated, types of,
173 ; De Candolle's investigations
on, 173 ; list of cultivated species of,

174

PLATEAU, on adaptation to salinity,
190

PLINY, 158 ; on varieties of Brassica
oleracea,) 177 ; on mutilation of
grape-vine, 220

Poisons, physiological variability as
concerns their effects, 139

POLO (MARCO), 159

POLYBIUS, 73

Polygonum amphibium, morphologi-
cal variations, 98, 209

Polygonum fagopyrum, 142

Pompiliis UHifasciatus, 120

Portunns puber transferred to fresh
water, 188

POUCHET (G.), on osteological varia-
bility, 104

POUCHET and BEAUREGARD, on osteo-
logical variability, 104

POUCHET and CHABRY, on the influ-
ence of decalcification of sea-water
on the development of larvae of sea-
urchins, 195

POULIN (M.), on sudden variation,
i53

POULTON (E B ), on the influence of
the colour of environment, 58 ; on
heredity, 225 ; on heredity of ab-
normalities, 255

PRANTL, on food and sexuality, 108

Pressure, its influence on life, 191

PREVOST (J. L.), on the influence of
veratrin on green and brown frog,
131

Prismatocarpus speculum, 91

PRJEVALSKY, 159

Proteus anguineus, neotenia, 112

Py ralis zntis, colour-variation, 51

Pyridin, influence on green and brown

frog, 132

Q.

Quagga, mated with a mare, 248
QUATREFAGES (DE), on dimensional

variations, 72
Quercus tosa toxic for Southdowns, not

injurious for Pyrenean sheep, 141
Quercy phosphorites, fauna of, 150
QUETELET, on thechemical differences

of the blood of man and woman, 122

K

Rabbits, dwarfed, 74

Rana esculenta, and tcmporaria,

principal physiological differences,

130
Ranunculus, different forms according

to environment, 95 ; forms of leaves,

97 ; R aquatilisa.n& hederaceus, 97 ;

differences according to aerial and

aquatic mode of life, 208 ; R. sylva-

ticus, 55 ; R.Jicarla, 142
RAULIN ( JULES), on the influence of

very slight chemical changes on the

life of Aspergillus niger, 182
REGELSPERGER (G.), on deformation

in molluscs by living in warm waters,

205
RFGNARD (P.), on the influence of

pressure on life, 191
Reptiles, evolution of circulatory appa-

ratus, 33
Rhododendron ferriigineum, form of

R. hirsutuin, 219
Rhns corlaria, 142
Ribs, variation of number, 103
RITZEMA Bos, on peculiar characters

of Tylenchi having fed only on one

species of plants, 206
ROBINET(B. J.), on evolution, 16
ROMANES (G. J.)>

ments, 250, 259

on propose exper-

,
d e

Roots, influence of the soil on their

growth, 204
Rosa alpina, 55
Rose carrying white and pink flowers,

60

ROSSLIN, 158

ROUJON (A.), on dwarfed plants, 75
ROUSSEAU (J. J.), on meditation, 4
Rubus, variation, 97
Rumex, sexuality, 108

S.

Saccnlina, development shows its real

systematic position, 30
Sagartia parasitica transferred to

fresh water, 187
Sagittaria, leaf- variation, 97
SAINT GEORGE MIVART, on variability

in the number of ribs, 103
SAINT HILAIRE, GEOFFROY, 19, 43
SAINT HILAIRE, ISIDORE GEOFFROY,

SAINT LAGER, on special forms of some
plants due to the chemical nature of
the soil, 219

SAINTE CLAIRE DEVILLE, on chemical
variability, 116

Salainandra atra, neotenia, 112

Salinity, adaptation to, 189

Salmon, chemical analyses of, 117

INDEX

269

SAUERMANN, on food in its relations to
colour, 57

SAUNTER (GASPARD DE), 159

Scent of flowers, variation, 102

SCHMANKEWITSCH, on differences in-
duced in Daphnia rectirostris by
mode of life, 213 ; on Branchipus
ferox, 216 ; on Artei/tia and Bran-
chipus, 217

SCHMIEDEBERG, . on the action of
caffein on green and brown frog,
JSi-iSS

SCHUBELER, on seeds of same species
obtained under different climates,
218

Scilla maritiina, 142

Sea-shore, influence on plants, 211

Sea-urchins, development of their
larvae in decalcified sea-water, 195

Sea-water fatal to most but not all
fresh-water organisms, 186 ; influence
on plants, 211

Seeds, physiological variability, 137-
139 ; influenced by environment, 218

Selection, natural, a factor in evolu-
tion, 230 ; sexual, 230 ; physio-
logical, 230; Weismann on, 231;
experiments on, 236 ; proposed ex-
periments, 240

Selection, Naudin on, 21 ; produces
most new forms when not subservient
to man's utilitarian demands, 168 ;
of carrots, 203 ; proposed experi-
ments, 241

SEMPER (K.), on dimensional varia-
tions, 79, 200; on environment, 179,

221

Serratula tinctoria, 95

Sexuality, variation, 107 ; influence of
food, 107 ; variation in plants, 107 ;
variation in human species and ani-
mals, 107 ; proportion of males to
females among domestic animals,
108 ; and parasitism, 108 ; and muti-
lations, 108 ; and food, 109 ; and
climate, 109 ; and external factors,
109, no ; sexes, proportion of males
and females in different animals,
108 ; and dwarfing, 200

Sheep, Mauchamp breed, 239 ; colour
and flesh, 68 ; colour and climate,
69 ; from Senegal acquiring wool
under northern climates, 89 ; chemi-
cal differences in skeleton of differ-
ent breeds, 116; Mauchamp breed
suddenly produced, 154; variability
in length of gestation of different
breeds, 167

Shell, left-handed, due to electrical in-
fluences, 204

Skull-capacity of wild and domestic
forms, 165

Stnerinthus, colour-variation, 51

Soil, influence on taste of wine, 219

Solanum stoloniferum, 236

SPALLANZANI on sexuality, 108

Special creation theory, 7, 22

Species, different, react differently to-
wards same poisons, 141 ; what are,
144, 254 ; all variable, 148 ; selec-
tion, 203

Specific characters not merely external
and morphological, but chemical and
physiological, 143

SPENCER (HERBERT), on evolutionists'
and anti-evolutionists' demands, 24 ;
on dimensional variations, 79, 200

Sphinx elpenor, colour- variation, 51

Spinacia oleracea, proportions of
sexes, 107 ; sexuality, 108

Starving, experiments on, 77

STELLA (ERASMUS), 158

Sterility of dwarfecl plants, 75

Stilbe americana and A bramis versi-
color identical, 90

Stomach, variability, 105

Stomata in aquatic and aerial indi-
viduals of same species, 208, 209

STRABO, 73, 158

Stratiotes aloides, influence of mode
of life on leaves, 209

Strychnine, influence on common crab,
120

STUDER, on molluscs living in warm
water, 205

STURTEVANT, on the origin of culti-
vated plants, 179

Sus vittatus, 158

SWAMMERDAM, on experimental tera-
togeny, 194

Syphilis, 124

T.

Tadpoles, influence of food on sexua-
lity, 107 ; experiments on the influ-
ence of salt, 189 ; influence of food,
199 ; embryology, 33

Taraxacum dens-leonis and palustre,
95

TARCHANOFF (JEAN DE), on the brain
of young animals, 145

Teeth of whales, 35 ; variation in num-
ber, 103

Tellina transferred to fresh water,
1 86

Temperature and life, 205

"Tendency to betterment," Delbceuf's,

i52

Teratogeny, experimental, 193
TERQUEM, on Foraminifera, 27
TESTUT, on muscular anomalies in

man and their interpretation, 37 105
Tetragonia, 236
Thalassema mellita, 197
THEOPHRASTUS, on varieties of Bras-

sica oleracea, 177

270

INDEX

THOMSON (J. A.), on the influence of
environment, 179 ; on heredity, 225

Thuja occidentalis^ influence of ex-
ternal conditions, 222 ; dwarfed, 71

Thnjopsis dolabrata variegata, 59

Thytnus serpyllum, 55, 91

TICHOMIROFF, on artificially induced
parthenogenesis, 197

TILLET, on investigations with artifi-
cial soils, 198

TOURNEFORT, 95 ; on varieties of
Brassica oleracea, 177

Toxicity of plants varies according to
their different parts, 142

Tradescantia virginica, variation of
an individual plant in respect of
flower-ir.orphology, 101

Transmutation of one micro-organism
into another, 126

Trifoliuin molineri, form of T. incar-
natum, 219

Triton, 112

TROCHU, on the non-spiny form of
Ulex europceus, 92

Tropceolum , influence of external con-
ditions, 222

Tuberculosis, comparative immunity
of Mongolians, 124

Turbo thermalis, 205

TURREL, on the non-spiny form of
Capparis spinosa, 92

Tylenchus devastatrix acquiring pecu-
liar characters from living on one
species of plant only, 206

U.

Ulex europceus devoid of spines,
92 ; Ulex nanus, 92 ; U. major,
form of U. paiviflorus, 219 ; U.
europceus, 245

Unio's variations in form and colour,
94 ; living in sea-water, 185

Urodela, 112

Use and disuse, a factor in evolution,
230 ; proposed experiments, 239

Ustilago antherarum, influence on
sexuality, 108

dimensions, 70 ; integuments, 89 ;
form, 93 ; leaf, 97 ; fruit, 99 ; flower,
101 ; personal, 125 ; universal, 147 ;
sudden, 152

Variations, osteological, 103 ; visceral,
105 ; sexual, 107

Variegation and environment, 54 ;
Carriere on, 58 ; some localities un-
favourable to variegation, 58, 59 ; are
variegated plants weaker than
others, 59 ; sudden variegation, 59

VARIGNY (DE), on history of evolution-
ary notions, 17 ; on the loss of
weight in Coelenterates during
inanition, 77 ; on dimensional varia-
tions (experiments on Lymncea), 79 ;
on abnormal prolongation of tadpole
condition, in ; influence of brucin,
strychnine, and picrotoxine on com-
mon crab, 120 ; observations on
normal variation among individuals
of the same brood of Lymncea, 137 ;
on the influence of heat on seeds,
137 ; on the influence of sulphate
of copper and of strychnine on
seeds, 138 ; experiments on accus-
toming marine animals to live in
fresh water, 187 ; experiments on the
adaptation of fresh-water forms to
life in saline media, 189

VARRO, 158

Venus, transferred to fresh water, 186

Veratrin, influence on green and brown
frogs, 131

Verbascum lychnis, 54

Vigour and colour, 69

VILMORIN (L. DE), on changes of colour
due to culture, 53 ; on variegation,
59 ; on Ulex nanus and europceus,
93; experiments in selection, 236, 237 ;
experiments on beet-root, 238 ; on
selection generally, 241

Visceral variations, 105

Vitis rupestris, predominant heredity,
245.

Vorticellce subjected to high pres-
sures, 192

Vulpes alopex, 50

VULPIAN, on the influence of poisons
on green and brown frogs, 131 ; on
the influence of brucine, 132

Valerian, less toxic when grown on dry
soil, 136

VALLEMONT (DE), on growth in thick-
ness partly determined by external
influences, 199

Variability present at all epochs, in all
organisms, 147 ; is itself variable,
149 ; causes unknown, 150

Variation among pathogenetic organ-
isms under different modes of culture,
126 ; in structure, 47 ; colour, 48 ;

WALLACE (A. R.), on seasonal colour-
variation, 52 ; on colour-variation,
67 ; on variability of the length of
the digestive system, 106

WEISMANN (A.), on variability in com-
mon pansy, 149 ; on acquired
characters, 221 ;on selection, 231

Whales, rudimentary teeth, 39 ; osteo-
logical variability, 103

INDEX

271

Wheat, chemical differences according

to soil, 118

WHITFIELD (R. P.)> on dwarfing in-
ducing unisexuality in Lynin&a,

200
WILLOUGHBY (F.), on hellebore and

water-dropwort not being toxic for

the common quail, 139
WINTZENRIED (L.), on the action of

brucin, 132

WOODHEAD, see IRVINE
Wool of sheep, relation to food, 90 ;

chemical differences according to

breeds, 117

Y.

YuNG(E.), on the influence of the
nature of food on the development
of tadpoles, 199

Zea Mays, sexuality and nutrition,
108 ; dwarfed, 75

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Cantab., and MATILDA BERNARD. Parti. 8vo, 17^. net.

" In compiling the book / have endeavoured to do full justice to the numerous
important results of the research of the last decade. / have been less anxious to
supply a complete and detailed compendium of comparative anatomy than to
bring to notice what is most important, and to bestow on it special attention.
The present work in many respects exceeds the limits till now usually assigned to
text-books of comparative anatomy. It contains, separated as far as possible
from the portion devoted to comparative anatomy, the elements of comparative
embryology, which will perhaps not be unwelcome to many students. Following
Oscar Schmidt's example, / have prefaced the comparative anatomy of the
different animal races by short systematic reviews, which may be of use to the
student of systematic zoology. The book had also to contain ivkat was necessary
for the zoological education of the medical student." — Extract from PROF.
LANJ'S Preface.

GLASGOW HERALD:— "One of the most satisfactory works it has been our
lot to notice."

SCOTSMAN:—" Will be gratefully welcomed by a host of students. . . . It is
the best general account of the science of comparative anatomy as developed on the
new lines laid down in the great biological works of Darwin and Wallace. It comes
out with the highest possible recommendation— a testimonial from Prof. Haeckel.
The translation . . . . is so well done as to be a model for others to follow ....
The illustrations are numerous and valuable. The version will at once take ics place
in the front rank among scientific text-books."

WORKS BY ALFRED RUSSEL WALLACE, LL.D.

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