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HOME UNIVERSITY LIBRARY
OF MODERN KNOWLEDGE

EVOLUTION

By PATRICK GEDDES
AND

J. ARTHUR THOMSON

LONDON
WILLIAMS & NORGATE

HENRY HOLT & Co., NEw Yore
Canapa: WM. BRIGGS, Toronto
Inpia : R. & T. WasHsourne, LTp.

et

Da Ft Sees
we

wh i HOME =
UNIVERSITY
LIBRARY : &

OF

MODERN KNOWLEDGE
Editors:

HERBERT FISHER, M.A., F.B.A.

PRroF. GILBERT MURRAY, D.LitTT.,
LL.D., F.B.A.

ProF. J. ARTHUR THOMSON, M.A.

i Ww r

NEW YORK
HENRY HOLT AND COMPANY

lle

EVOLUTION

BY

PATRICK GEDDES

PROFESSOR OF BOTANY, ST, ANDREWS
UNIVERSITY

AND

J. ARTHUR THOMSON

REGIUS PROFESSOR OF NATURAL HISTORY,
ABERDEEN UNIVERSITY

Joint Authors of *‘ The Evolution
Of Sex,” ete.

| LONDON -
WILLIAMS AND NORGATE

Printed by
MORRISON & GiBB LIMITED
Edinburgh

THE INSTITUTE OF REDIAEVAL STUDIES

ID &. ReSLeYyY reas

TORONTO 6, CANADA,

JUN 3 1958

II

III

VIIl

CONTENTS

INTRODUCTION. . 6 , : :

EVIDENCES OF EVOLUTION FROM EXPLORER
AND PALZONTOLOGIST . : : :

EVIDENCES OF EVOLUTION FROM ANATOMIST,
EMBRYOLOGIST AND PHYSIOLOGIST. :

GREAT STEPS IN EVOLUTION e e °
VARIATION AND HEREDITY e : :
SELECTION o . e e . bs

ORGANISM, FUNCTION AND ENVIRONMENT

EVOLUTION THEORIES IN THEIR SOCIAL
ORIGINS AND INTER-ACTIONS. : :

THE ‘EVOLUTION PROCESS ONCE MORE RE-
INTERPRETED . : ‘ ; ;

BIBLIOGRAPHY . . 9 * e :

Digitized by the Internet Archive
in 2007 with funding from
Microsoft Corporation

http://www.archive.org/details/evolutionO0gedduoft

INTRODUCTION

Despite the many and wide differences so
obvious in every community—of age and sex,
of regional origins and historic groupings, of
occupations and interests, of experience and
intelligence, efficiency and originality, of edu-
cation, manners and morals, of wealth and
rank, and so on—each generation has more in
common than its individuals may realize.
Layman and cleric, pressman and prime
minister, message-boy and millionaire respond
not merely to their respective call-bells, nor
in common to the peal of general rejoicing, to
the tolling of sorrow; but through their minds
there vibrates also a certain unison, a response,
though it may be more or less unconscious, to
the key-notes of their age. How this unison
underlies the apparent differences is easily
seen on differing intellectual levels. The boy
in the train buys Tit-Bits, but the man in
the villa takes in the new Britannica ;

the specialist concentrates upon the “ Pro-
vii

viii INTRODUCTION

ceedings *’ of his learned society, while the
university principal reviews his “‘ Calendar ”
of all the studies: so far they seem widely
apart. But, after all, their differences are
only of degree and not of kind; all four are
children of the recent and passing phase of
knowledge, characterized by the encyclopedia
—whether in “articles” or in “ papers,”
in lecture-courses or in snippets from them—
all is but a question of magnitude, a matter
of detail. All four readers alike are inter-
ested in knowledge of one sort. or another;
but these are seen mainly as knowledges, and
as advancing analyses, rather than as a grow-
ing synthesis. So though they all read very
different newspapers, these newspapers are
yet much the same, all vividly retrospective
of yesterday, and keenly criticizing such and
such of its doings, but as yet with little sight
of how the day’s items are resultants of far
distant yesterdays, sowings for far distant
morrows. Yet ideas of unity amid diversity,
of order amid change, have also long been
growing, even finding expression, and this
not merely, as sporadically in all ages, in im-
pressions and speculations on decline or on
better things; but in clearer and more com-
prehensive surveys of the processes of change,
even inquiries into its method. These, in

INTRODUCTION ix

fact, have gone towards making up that
general idea we now more or less share, of the
universe as not only orderly, but in process
of change. Changing order, orderly change,
and this everywhere—in nature inorganic and
organic, in individual and in social life—for
this vast conception, now everywhere dif-
fusing, often expressed, rarely as yet applied,
we need some general term—and this is
Evolution.

Now, if this be gaining ground as a con-
ception of the world-process, it is time to be
inquiring farther into it: how is this to be
done? On one hand historically, thus quickly
appropriating the best thought as yet reached
by others; on the other hand directly, at first
hand and for oneself, in our own environment
of life and work and contact with nature. In
the former way we shall save time, and in the
latter gain definiteness; hence impartially
deciding on both, we may most speedily turn
for our outlines to our encyclopedia, say
Chambers’ articles “‘ Evolution ” and “ Dar-
winian Theory” ; and for direct experience
take a holiday in the woods or by the shore.
At first the general ideas of our reading, the
details of our field-observing, may seem to
have little in common, like the old philosopher
and the boy collector among our acquaint-

x INTRODUCTION

ances: but gradually they come together:
orderly change in general, changing order amid
particulars, are more and more seen to be at
one: thus we become evolutionists. We hear
of boy collectors becoming old philosophers,
yet remaining boy collectors still: Darwin
above all. Among his foremost fellows,
Wallace, Haeckel, Hooker are still with
us; and later ones in increasing number.
Observing and thinking, thinking and observ-
ing; outdoor and indoor, and outdoor again;
that is a game at which we all can play;
with education and evolution alike mingled
in its process and in its winning.

Evolution in astronomy, from Kant to
Lockyer; evolution in chemistry and physics,
from Lucretius to the alchemists, and thence
to Ramsay and his fellow-alchemists of to-
day; evolution in geology, from Leonerdo and
Palissy to Lyell and Darwin and onwards—
all these large retrospects of the history of
science are needed for a grasp of cosmic
evolution. Their impetus, their methods too,
have once and again impelled the student of
' organic nature towards evolutionary inter-
pretations, and still do so; while the thought
of the physicist and of the naturalist are in-
creasingly of interest and suggestion towards
the distinctively human and social studies.

INTRODUCTION xi

Yet it was essentially in the very opposite
way that modern evolution doctrines really
originated; as a social theory, that of progress :
and this generally diffused spirit of the later
eighteenth century, and the earlier nineteenth,
has both consciously and unconsciously stimu-
lated naturalist and physicist towards their
evolutionary inquiries and doctrines. Of this
social ferment of evolutionary thought there
have been as yet two main phases; and first
the French eighteenth century “ Progress of
Humanity,” that characteristic doctrine of
the Encyclopedists and Physiocrats, of Rous-
seau, and of the Revolution at its best, and
this expressed for history by Condorcet, for
living nature by Lamarck. The second phase
is that of the Industrial Revolution in Britain,
from Waitt and Arkwright to Stephenson and
Wheatstone; and thence to a nineteenth-
century manufacturing and commercial world-
predominance, proportionately culminating
from 1851 to 1860 or thereby; with its char-
acteristic “* self-made men,” its colonial expan-
sion and growing empire.

It was the former period, with its theories
of society and of morals, which gave birth to
the “ Doctrine of Evolution”; while the
latter period, with its competitive industry,
its resultant “‘ population question,” etc., has

xii INTRODUCTION

found its expression in the “ Doctrine of
Natural Selection.” Each of these two great
advances of thought is thus the philosophic
epic of a great nation at its epoch; and
Lamarck and Darwin are their representative
prophets respectively.

In the generation after Darwin research
was necessarily actively specialized in biology;
and the social perspective, with its conscious
application to evolutionary research, has been
little employed by naturalists since Darwin
and Wallace, despite its extraordinary fruit-
fulness in their hands. Now, however, it
begins to return, witness the Eugenie move-
ment: and in these pages we shall not hesitate
to avail ourselves of it.

We may even utilize it for teaching pur-
poses, beginning with the doctrine of natural
selection. As Paley’s famous ‘“‘ watch argu-
ment” appeared at the outset of the
mechanical age, so again at its culmination
we may avail ourselves of the conspicuous
progress of invention to explain and illustrate
Darwin’s great doctrine. In fact, we may
socratically elicit it from the freshman who
supposes himself quite unacquainted with
biology or its theories. For he knows the
points of a bicycle, and something of the
story of its development from his father’s

INTRODUCTION xiii

‘“* bone-shaker,”’ at one time by the introduc-
tion of ball-bearings, at another by the inven-
tion of pneumatic tyres, each new make,
thanks to this or that better “‘ adaptation,”
being eminently successful in surviving against
its kindred but less developed competitors
in the struggle for existence. From bicycle,
or similarly motor or aeroplane, we pass
readily enough to bicyclist, to racehorse and
bird: and we see how we may explain the
evolution of their swiftness in like manner.
The man in the street is thus a Darwinian
without knowing it, and the world-success
of Darwin’s theory is thus more readily
understood; the age had found its man, the
hour its voice.

But what of outdoor nature? ‘The field in
summer, the study in winter ” is a good rule,
yet not a sufficient one; the evolutionist’s
studies should as far as possible include both
elements of observation and interpretation
day by day. Hence Darwin’s is perhaps the
most exemplary of scientific lives, incessantly
rising from sight to insight, yet this as con-
stantly freshening sight anew. From boyish
truancies, through youthful travels and matur-
ing researches his observations and his specu-
lations went on enriching one another; and
thus their interpretation and theory have been

xiv INTRODUCTION

an “‘ open sesame ”’ to new fields, new volumes
of personal discovery, new impulses to fresh
workers. Naturalist and thinker, teacher
and pupil, will thus long be inspired by the
example of Darwin as rambler, traveller
and observer, yet also as dreamer and inter-
preter. The study of biology is thus by no
means merely abstract, nor mainly in the
library; it ever arises from and returns to
living nature, and goes on throughout that
annual season-drama of which we are but the
awakening spectators.

So psychology has its concrete nature-
observation in child study, in animal be-
haviour; and just as ethics has its side of
everyday life, so sociology its current events.
Nature studies and social studies must again
be generalized, and this not only separ-
ately but in unison. How so? By and
from Regional Survey. Relief and climate,
geological and botanical surveys, anthropo-
logical, archzological and historic surveys
all underlie our social studies. Our concrete
science thus generalizes into a comprehensive
regional survey, natural and social, rural and
urban; as our abstract sciences advance and
unite into a philosophy of evolution. In
measure as our abstract interpretations and
our concrete surveys come together and unify;

INTRODUCTION xV

our geography becomes geogeny, that is, it
develops from mere empirical world-descrip-
tion into a rational vision of world-develop-
ment. And correspondingly, the abstract of
this, which is our evolution doctrine, becomes
applicable in education and in social life.

Enough, then, of introductory outline; in
the following chapters we endeavour to eluci-
date some of these large propositions more
clearly.

CHAPTER I

EVIDENCES OF EVOLUTION FROM EXPLORER
AND PALZONTOLOGIST

The Voyage of the ‘‘ Beagle” —The Galapagos Islands—
Other Geographical Evidence—Resemblances of Present
Forms and Past Ones—The Ancestry of the Horse—
Connecting Links— Other Paleontological Evidences.

THE VOYAGE OF THE “‘BEAGLE.”—We think
of the voyage of the “Challenger “as a Colum-
bus-voyage_in. the historyof Biology, for it
revealed a new world—the strange, silent, cold,
dark, plantless world of the abyssal sea. But
a far greater Columbus-voyage was that of the
** Beagle ” (1831-6), which led Darwin, as the
supreme field-naturalist, at once widest and
intensest, to make the whole world new. For
it was during this voyage that the evolutionist
view of Nature was vitally borne in 6n Dar-
win’s mind. He tells us so himself : “ On my
return home in the autumn of 18386 I immedi-
ately began to prepare my journal for publi-
cation, and then saw how many facts indicated

the common descent of species. ... In July
16

a

EVIDENCES OF EVOLUTION 17

(1837) I opened my first notebook for facts in
relation to the Origin of Species, about which
I had long reflected, and never ceased working
for the next twenty years. ... Had been
greatly struck from about the month of pre-
vious March on character of South American
fossils, and species on Galapagos Archipelago.
These facts (especially latter) origin of all my
views.”

This interesting biographic fact, that what
Darwin saw on the Galapagos Islands and
elsewhere on his journeyings was (or at least
seemed to him) the origin of all his views,
justifies us in giving precedence to the “ evi-
dences”’ of evolution that have come from
his and other explorations.

THE GALAPAGOS IsLANDS.—Let us take the
case of these islands (some six hundred miles
west of the coast of South America), which
impressed Darwin so much when he visited
them in 1835. What exactly was it that im-
pressed him? He found that each island

had its own_distinctive animal population,

especially of reptiles and birds. And yet the
species in one island were the counterparts of ©

those in another, and almost all had their
counterparts in the adjoining parts of the

continent. What a riddle indeed—unless it
meant that the corresponding species on the

i8 EVOLUTION

different islands and on the continent were
blood-relations ¥ with a common descent ?

Thus it was that in the Galapagos Archipelago
Darwin felt_ himself “ brought-near.to the very

_act of creation.” —

** My attention,” Darwin writes, ‘ was first
thoroughly aroused by comparing together the
numerous specimens, shot by myself and
several other parties on board, of mocking
thrushes, when, to my astonishment, I dis-
covered that all those from Charles Island
belonged to one species (Mimus trifasciatus);
all from Albemarle Island to M. parvulus;
and all from James and Chatham Islands
(between which two other islands are situ-
ated as connecting links) belonged to M.
melanotis.”

All subsequent investigations have con-
firmed Darwin’s observations, both in their
general result and in details. Thus it has since
been shown by Ridgway that the thrushes
from James and Chatham Islands of the same
group are also of distinct species. And of one
hundred and twenty-eight specimens of a
lizard called Tropidurus collected by the
** Albatross” from eight of the islands, Dr.
Baur writes just as Darwin did: “I was not
a little astonished to find that nearly every

island contained a peculiar race or species.ot.

EVIDENCES OF EVOLUTION 19

this liz j j on-
tained more than one race or specie;-"’ —The..

suggested except t that which Darwin gave—of
. divergent. evolution froma common ‘stock. .
~~ We cannot here enter into a discussion of
the geological history of the Galapagos Islands,
in regard to which there is some difference of
opinion; it must suffice to state one of the
theories—that advanced by Baur in the Woods
Holl Biological Lectures for 1804. At~a~

former period these islands were connected

with each other, forming a single large island,
which itself at a still earlier time was united

with the continent, probably with Central

America and the West Indies. When this

large e “island was not yet broken up into a
‘series ‘of smaller islands, the number of species —
must have been very much smaller; probably ;
there ¥ was only one species of Nesomimus, of
-Certhidia, “of” Tropidurus, of the’ “Land for=~
-toise, and so on. Thr hrough i isolation into igi”
islends the "peculiar differentiation of the.
ecies began; an originally single species was
amany different forms; every, ~
or-nearly every, island developed its peculiar _

_races. e still see to-day that islands whi
_are close togé ated by deep

20 EVOLUTION

water show the same species, like James and

ervis or Hoo ~—~The faunas of
the larger central islands are again more closely
related to each other than are the faunas of
the more isolated islands, like Tower, Bindloe,
Abingdon, Hood and Charles. The tortoise
of Duncan is closest to the tortoise from Abing-
don; at the same time the Tropidurus of
Duncan comes nearest to that of Abingdon.
The prevention of intercrossing after the
separation of the islands, the time of separa-
tion, and the difference in the conditions on
the different islands, are the factors which
produced the different races.”

We may also refer the student to Wallace’s
fascinating “‘ Island Life”’ for further illus-
trations of the evolutionary suggestiveness of
the exploration of islands.

OTHER GEOGRAPHICAL EvIDENCES.—As in
other parts of this little book we have dwelt
on one interesting illustration of a large
subject, we cannot do more than refer briefly
to some of the other geographical evidences.

With the help of the paleontologist it is
sometimes possible to come to a conclusion as
to the original headquarters of a particular
race of plants or animals, and then it is found
that the present-day distribution of the
members of the race is readily intelligible on

EVIDENCES OF EVOLUTION 21

the evolutionary assumption of diffusion from
the original centre, and of transformation into
new species in relation to the new conditions
encountered. Some of the particular cases leap
to the eye, but they are unmeaning conun-
drums without the evolutionist clue. Darwin
has, in fact, brought us more nearly back to
the Noah’s ark of our childhood than we
commonly realize; for do not all these
stories of thrushes, lizards and what not
quaintly recall the origin of human races from
the dispersion of Shem, Ham and Japheth ?

In Mesozoic times, when there were no
Mammals higher than Marsupials, Australia
was separated off from the Asiatic continent.
Therefore it is that there are no higher
Mammals in Australia, except the somewhat
mysterious dingo, the bats, which find the sea
no barrier, and the rabbits, for which man
is responsible.

A final argument is furnished by the con-
trast in the fauna and flora of oceanic and of
continental islands. The former, being usually
of volcanic origin, have always a very dis-
tinctive fauna and flora, which Wallace has
explained as being due to the fortuitous con-
tributions borne from diverse quarters by
currents, winds and birds. Other islands,
which are isolated pieces of continents, have

22 EVOLUTION

a fauna and flora like that of the nearest part
of the mainland.

RESEMBLANCES OF PRESENT FoRMS AND
Past Ones.—Another seed-impression that
was borne in on Darwin’s mind during his
journeyings was the striking resemblance
between the living and the extinct forms in
the same area. On his travels into the interior
of South America he made large collections,
both of living animals and of fossils dug from
the red mud of the Pampas, and what im-
pressed him most was that the extinct bore a
notable correspondence to the extant. No
living creatures are more characteristic of the
South American fauna than the sloths and
ant-eaters; no fossils are more characteristic
than the gigantic Megatheriums and Glypto-
donts; and the important fact is the structural
resemblance between these creatures of the
past and those of the present—a structural
resemblance which suggested to Darwin that
the explanation might be, indeed must be,
one of blood-relationship. ‘“ This wonderful
relationship,” he wrote, ‘‘ in the same conti-
nent between the dead and the living will, I
do not doubt, hereafter throw more light on
the appearance of organic beings on our earth,
and their disappearance from it, than any
ether class of facts.”? This is, to be sure, a

EVIDENCES OF EVOLUTION) 28

cautious statement; but it seems not unlikely
that it was while thus digging his fossils on
the Pampas that Darwin lai
the principle long nascent in geology, a
especially-impresséd vu upon him by Lye
the present~is"the child of the past—an a
which he spent-so-muchof “his life in” sub-
stantiating. Let us considér~somé™ other
illustrations of the paleontological evidence.
Fossiz Horses.—Huxley made a strong
statement in 1855 as to the futility of seeking
in the study of fossils for confirmation of the
doctrine of evolution, but after a quarter of a
century of investigation he was as strongly of
the opposite opinion, declaring that “ if zoolo-
gists and embryologists had not put forward
the theory, it would have been necessary for
paleontologists to invent it.” One of the
many reasons which led him to a warm appre-
ciation of “* the paleontological evidence,” was
a visit to America, where he saw the famous
series of fossil horses which Marsh had un-
earthed from American Tertiary beds—one of
the most impressive of pedigrees that has yet
been disclosed. For although we are not even
now able to state the lineage of the modern
horse, the chief steps in the evolutionary
process stand out with clearness, and he must
be dull indeed who can see the admirably

24 EVOLUTION

arranged and convincing series in the museums
at Yale and New York without a thrill of
admiration at the wonderful reconstruction of
the ancient history of the noblest race of ani-
mals, and that most widely identified with man.
Since Huxley’s day the fossil horse has been
‘the cheval de bataille of the evolutionist.”

In spite of many puzzles, the pedigree is one
of the completest and most striking instances
of a well-preserved genealogical series. It
illustrates evolution, as it were, in process, for
the gradations are very gradual; and natural
selection also, for the advances in the adapta-
tion of the limbs to swifter locomotion, of the
neck to reach the low grass, of the teeth for
more effective chewing, and so on, are all such
as may be reasonably interpreted in terms of
the selection of relatively better-fitted varia-
tions. Let us, since the case is a classic one,
attempt an outline of the geological history
of the horse family, following the careful
work of the successors of Marsh and Cope,
notably of Lull and Matthew.

The horse-like animals probably sprang
from an extinct stock known as the Condy]l-
arthra, which was first represented in Europe
and Asia, and afterwards in North America.
The Condylarthra had five toes on each foot
and a large part of the sole was on the ground.

EVIDENCES OF EVOLUTION 25

One of them, Phenacodus, was called by its
discoverer, Professor E. D. Cope, a“ five-toed
horse,” but this is not to be taken too literally.
“The first undoubted horse-like animal
appearing in the rocks of North America is a
little creature not more than eleven inches
high, known to science as Eohippus. This
interesting animal had already made a long
stride in the direction of the modern horse, as
the number of toes is now reduced to four in
front and three behind, and the bones of the
wrist and ankle have shifted so as to interlock,
which greatly strengthens the foot.” It seems
that Eohippus was also represented in Britain,
and it is possible that migrants by way of Asia
and what is now the Behring Strait started
the American stock. Apparently more primi-
tive than Eohippus is the “ coney-like crea-
ture’’ Hyracotherium, but only the skull is
known. “‘Commencing with the Hyraco-
therium,”’ Dr. Matthew writes, “‘ twelve stages
have been recognized from as many successive
formations, showing the gradual evolution of
the race into its modern form; and each stage
is characteristic of its particular geological
horizon. Besides the main line of descent
which led into the modern horses and zebras,
there were several collateral branches which
have left no descendants.”

26 EVOLUTION

Also in the Eocene there was Protorohippus,
with four toes in front and three behind, the
side ones behind touching the ground. It
seems to have been about fourteen inches
high, and the evolution of speed had begun.
During the Eocene times North America was
in great part forest-clad, but “the moist
climate gave rise to many streams and lakes,
along the shores of which grew sedgy meadows
that in turn gave rise to grassy plains. These
were the conditions under which the horses
made their first appearance, and the increasing
development of grass lands gave the initial
trend to their evolution.”

Somewhat later, in the Oligocene, Meso-
hippus makes its appearance, the hind-foot
with three toes as before, but the fore-foot
with the little toe reduced to a splint, so that
only three remain, the side ones just touching
the ground. The middle or third toe is now
much larger than the side toes, which no
longer bear much of the weight of the animal,
save on marshy ground. The grinding teeth
have become more complex. One of the
species of Mesohippus was about the size of
a sheep, and one of the treasures in the Yale
Museum that brings the past very vividly back
to us is the nearly perfect skull of its new-born
foal. Of the physical conditions of the Oli-

EVIDENCES OF EVOLUTION 27

gocene, Dr. Lull writes: “‘ The drying up of
streams and lakes, due to the increasing aridity
of climate, gave great impetus to the develop-
ment of broad meadow lands, and to the true
prairie as well. Thus there were three con-
ditions—woodland, meadows and dry prairie,
which seem to have given rise to several
parallel lines of evolution, some of which
terminated, being overcome in the struggle
for existence, while others flourished and gave
rise to the horses of the Miocene.”

Of the Miocene types we may select Proto-
hippus, with three toes on each foot, but
only one touching the ground. The short-
crowned teeth without cement are now
replaced by long-crowned cement-covered
teeth like those of the modern horse. Proto-
hippus was about thirty-six inches high at
the shoulder, and had a wide distribution from
Texas to Montana and Oregon. In a closely
related genus, Merychippus, we find the first
instance of the completion of a bridge of bone
at the hinder border of the orbit, one of the
characteristic differences between the skull of
a horse and that of a carnivore, for instance.
Merychippus is of particular interest, because
it is almost certainly in the direct line of
ancestry to all subsequent Equide. The
forest-horse, Hypohippus, with spreading

28 EVOLUTION

three-toed feet, suited, like the reindeer’s,
for soft ground, is a good example of those
horses that became extinct during the Miocene,
leaving no descendants, and Anchitherium,
found both in Europe and in America, was
probably also on a side branch. Of the
Miocene period, Dr. Lull says: “ This was
a time of continental elevation and great
expansion of our western prairies and a con-
sequent diminution of the forest-clad areas.”
Many forms very perfectly adapted to soft
herbage became extinct, “but the great
majority were more plastic and in consequence
underwent a remarkable development, during
this period reaching the culmination in
numbers and kinds.”

In the Pliocene there was a wide repre-
sentation of the Old World genus Hipparion,
most of the species still three-toed. It was
probably derived from the American Neo-
hipparion, a swift, deer-like animal, about
forty inches in height at the shoulder. “In
the Siwalik beds of India is found a one-toed
Hipparion, and it has been suggested that
the modern zebras may be the living descend-
ants of this genus. It is certainly not in the
line to the common horse, Equus caballus,
which makes its appearance, however, in the
Upper Pliocene beds both of Eurasia and

EVIDENCES OF EVOLUTION 29

North America—the climax of a long evo-
lutionary progression.”

We have dwelt on the case of the horse’s
pedigree—at once longer and stranger than
any fairy ride—because it is one of the best
instances of its kind, and from one such we
may learn all. But we have only given the
bare outlines of a remarkable story, well
worth reading in detail. In the enthusiasm
of early discoveries the matter seemed simpler
than it really is, and the mistake was made
of hurriedly constructing a linear series which
showed, for instance, the gradual reduction
of toes from five to one, and supposing that
this was a genuine pedigree. More detailed
and critical inquiry has shown, however, that
there were several collateral series, and it is
not quite justifiable to fill up gaps along one
line by links which belong to other lines of
descént. One critic points out that Equus
actually appears in the rock record before
some of its alleged ancestors, and Depéret
writes in his interesting “ Transformations
of the Animal World”: “ The supposed
pedigree of the Equidz is a deceitful delusion,
which simply gives us the general process by
which the tridactyl hoof of an Ungulate can
transform itself, in various groups, into a
monodactyl hoof, in view of an adapta-

30 EVOLUTION

tion for speed.” It is interesting to notice,
however, that among competent critics
of too hastily constructed pedigrees even
the severest do not in the least impugn the
doctrine of evolution.

What seems clear is this, that in early
Eocene times there lived small five-toed
hoofed quadrupeds of generalized type, that
the descendants of these were gradually
specialized throughout long ages along similar,
but by and by divergent lines, that they lost
toe after toe till only the third remained,
that they became taller and swifter, that they
gained longer necks, more complex teeth and
larger brains. So from the short-legged splay-
footed plodders of the Eocene marshes there
were evolved light-footed horses running on
tiptoe on the dry plains.

We can only refer to the importance for an
evolutionist outlook of thus trying to correlate
the changes in the animal with the changes
in the external conditions. The evolution of
the horse is wrapped up with the evolution
of the plains, and of their grasses also, for
these made their first appearance in Tertiary
times. The early ancestors probably lived in
the warm luxuriant forests, but as colder,
drier climate set in, and the forests shrank,
the progressive “ hippoids ” took more and

EVIDENCES OF EVOLUTION 381

more to the open. Even in regard to the
teeth we can understand that the change
from the short-crowned to the long-crowned
type enabled the animals, as Dr. Matthew
notices, “‘ to subsist on the hard, comparatively
innutritious grasses of the dry plains, which
require much more thorough mastication
before they can be of any use as food than do
the softer green foods of the swamps and
forests.”

We must not leave this question of the
horse’s evolution without calling attention to
a fact of great interest, that in the individual
development there is a series of changes which
to some extent correspond with the historical
steps represented by forms like Eohippus,
Mesohippus, Protohippus, Merychippus, and so
on. Professor Cossar Ewart has shown, for
instance, that the small nodule at the end of the
splint bone is separate in the embryo, and is
the representative of one or more of the joints
of the second or the fourth digit which, apart
from this, would seem to have entirely passed
away. It is well known that in a monstrosity
of our familiar one-toed horse the splint bone
on each side of the main cannon-bone is en-
larged, and bears a complete digit, so that a
three-toed horse, such as the one Julius Cesar
rode, occasionally still walks upon the earth.

~

32 EVOLUTION

Such cases of symmetrical three-toed develop-
ment may be fairly interpreted as reversions
to the ancestral type, and are to be distin-
guished from unsymmetrical extra toes, which
are mere duplications without ancestral in-
terest, and comparable to the occasional
occurrence of a sixth finger in man.

In his very interesting study of “‘ Wild Traits
in Tame Animals ”’ (1897) Dr. Louis Robinson
refers to survivals of behaviour which date
from the old wild life in the open plains. It
was imperative long ago that the young foals
should run with their mothers, and to this
day they do not gorge themselves with milk
as calves do. When alarmed, horses hold
their heads high, as when wild upon the
plains; they bite very closely when grazing;
in both respects they differ markedly from
cattle. ‘“‘Shying” is a relic of the instinct
of swerving suddenly from a suspicious rust-
ling and the like which used to mean the
presence of a lurking foe. Such survivals
are interesting and strike our fancy; but the
past lives in the present even more clearly
in regard to structure than in regard to habit,
and by the “‘ button ” at the lower end of the
splint bones the modern horse is indubitably
linked back to its polydactyl ancestors.

ConnecTinec Linxs.—There is no more

EVIDENCES OF EVOLUTION 33

complete or striking contrast of aspect and
habitat, habit and temperament in the animal
kingdom than that between the average bird
and the average reptile; and yet every zoolo-
gist is sure that birds sprang from some
ancient reptilian or saurian stock. He has
not ceased to wonder how this transition
can have come about; “ how the slow, cold-
blooded, scaly beast ever became transformed
into the quick, hot-blooded, feathered bird,
the joy of creation”’; but he does not doubt
that the transition was effected. He is still
unwilling to make any positive statement
in regard to the precise pedigree of birds, and
yet he is confident that they sprang from a
reptilian stock. What are the reasons for
this confidence ?

They are threefold :—({1) There are, in spite
of appearances, numerous structural resem-
blances between birds and reptiles, from the
scales on the feet to the composition and the
articulation of the lower jaw; (2) there are
deep similarities in development, for the
embryo bird and the embryo reptile travel at
first along parallel paths, and only gradually
part company; and (8) there are extinct
types which to some extent bridge the con-
spicuous gap. A word, then, in regard to these

connecting links.
B

34 EVOLUTION

One of the most treasured fossils in the
world—of which the British Museum and the
Berlin Museum have each one of the two
known specimens—is the oldest known bird,
Archeopteryx. These priceless skeletons were
found well preserved in the lithographic stone
of Bavaria, and the grain of the stone—
a hardened mud—is so fine that the impres-
sions of the feathers are well seen, and most
of the bones are clear. Archzopteryx was a
creature about the size of a crow, probably
arboreal, and beyond all doubt a bird—the
earliest bird we know of. But what gives it
a peculiar interest is that while it is not far
from a typical bird in its skull, its merry-
thought, and its legs, it is in some other
respects markedly reptile-like. It has, for
instance, teeth in both jaws, a long tail like
a lizard’s, and a strange wing, well-developed
yet unfinished, with its three digits ending in
unmistakable claws.

Now Archeopteryx was very far from being
a beginner on the bird line of evolution; its
wings and its legs prove that. It is also
possible that it was an offshoot from the
direct line, and thus not ancestral to any
bird now living. Still, we cannot but regard
it as “‘a connecting link” in the sense that
it shows in its structure a combination of

EVIDENCES OF EVOLUTION’ 385

reptilian and avian characters, the latter, of
course, fully predominating.

Fossit SERIES.—One of the finest examples
of a well-preserved series of kindred forms
is afforded by an extinct freshwater snail,
Paludina neumayri, which is very abundant
in some Tertiary deposits in Slavonia. The
oldest form has a more or less smooth shell,
the youngest has a conspicuously ridged shell,
and there are fifteen gradations between the
two. Before the complete series was known
it was usual to distinguish half a dozen or
more species; but with the beautifully gradu-
ated, really continuous series before us, we
feel—fossils as they are—that we see a species
varying before our eyes. If conditions had”
arisen that assured survival and success only
to the markedly ridged forms, the inter-
mediate gradations would soon have fallen
into the minority and disappeared as living
creatures from the scene, and a ridged species,
apparently discontinuous, would have been
established.

Similarly in the neighbourhood of Stein-
heim in Wirtemberg, in calcareous deposits
that mark the floor of an old Tertiary
lake, there are enormous quantities of a
small snail, Planorbis multiformis, which has

been carefully studied by Hyatt and others.
B2

36 EVOLUTION

And again, since the whole history has been
unearthed, we see evolution before our eyes.
The particularly interesting feature is that
there are four or so primitive forms which
are very like one another, and that each of
these is the starting-point of a series the
termini of which are very different. The
contrast between the beginning and the end
of a series, e.g. between a high spiral and a
flat spiral, is often so striking that no one
would hesitate in calling them distinct species.
Yet they are connected by a long series of
fine gradations.

Some are surprised that such series are not
commoner if Evolution has been the mode of
the becoming of things; but they have not
adequately understood how great are the odds
against the preservation of such records.
Only hard parts make good fossils; only cer-
tain kinds of deposits make suitable tombs;
many rocks have been unmade and re-made
several times;—these and many other facts
enable us to understand “the imperfection
of the geological record.”” As Darwin said,
we must look at the geological record “as a
history of the world imperfectly kept, and
written in a changing dialect; of this history
we possess the last volume alone, relating
only to two or three countries. Of this

EVIDENCES OF EVOLUTION 37

volume, only here and there a short chapter
has been preserved; and of each page, only
here and there a few lines.” And again he
said: “‘ We shall perhaps best perceive the
improbability of our being enabled to connect
species by numerous fine intermediate fossil
links, by asking ourselves whether, for in-
stance, geologists at some future period will
be able to prove that our different breeds of
cattle, sheep, horses and dogs are descended
from a single stock or from several aboriginal
stocks. ... This could be effected by the
future geologist only by his discovering in
a fossil state numerous intermediate grada-
tions; and such success is improbable in the
highest degree.”

OTHER PALZONTOLOGICAL EvIDENCES.—
There is a sublime suggestiveness in the broad
fact that in successive periods of the earth’s
history higher and higher animals appear.
Fishes make their appearance in the Silurian,
Amphibians in the Carboniferous, Reptiles
in the Permian, and Birds in the Jurassic.
The record as regards plants is perhaps more
striking in some of its details than in its broad
outlines (see Dr. Scott’s volume in this series
on “The Evolution of Plants”), but every
one will allow that there were Cryptogams
before there were Phanerogams, and Cycads

8§ EVOLUTION

and Conifers before there were any ordinary
Flowering Plants.

There are other sets of suggestive facts to
which reference might be made if space per-
mitted : there is the absence of sudden breaks
or cataclysms; there is gradual waxing and
waning of races; there is the remarkable
phenomenon of what may be called the
adolescence and senescence of genera, if not
even species; there is the occurrence of old-
fashioned generalized types which link to-
gether a number of now divergent stocks; but
perhaps we have said enough to show that
the facts brought to light by the explorations
of paleontologists are suggestive of the
evolutionist interpretation, and there is no
other reading of the rock-record that does
not leave the facts enigmatical. In emphasiz-
ing the importance of this line of argument,
Huxley said: “ The primary and direct evi-
dence in favour of Evolution can be furnished
only by paleontology. The geological record,
so soon as it approaches completeness, must,
when properly questioned, yield either an
affirmative or a negative answer: if Evolution
has taken place there will its mark be left;
if it has not taken place there will lie its
refutation.” But it is more consistent with
the science of to-day to put the case more

EVIDENCES OF EVOLUTION 389

confidently, and we -would quote the opinion
of a living paleontologist of high achieve-
ment, Professor W. B. Scott of Princeton:
“The geological record is not so hopelessly
incomplete as Darwin believed it to be. Since
‘The Origin of Species’ was written our
knowledge of that record has been enormously
extended, and we now possess, no complete
volumes, it is true, but some remarkably full
and illuminating chapters. The main signifi-
cance of the whole lies in the fact that, just
in proportion to the completeness of the record
is the unequivocal character of its testimony to
ihe truth of the evolutionary theory.”

The wealth and interest of the palsonto-
logical record is, in fact, only nowadays coming
to be fully appreciated by the palzontologists
themselves. From collectors and specialists
they are becoming not only museum-makers,
but so far also artists, not only arranging their
specimens in clear evolutionary series, like
the horses at Yale or the elephants’ teeth at
South Kensington, or setting up their skeletons
in living attitudes, like the marvellous group
of Iguanodons which are the glory of the
Brussels Museum, but becoming also sculptors,
and modelling their ancient monsters as they
must actually have lived. Nearly a couple
of generations ago this was tried, as notably

40 EVOLUTION

for the Ichthyosaurs and Plesiosaurs (Liassic
fish-dragons and swan-dragons) at the Crystal
Palace, where to this day there are some
weird survivals, but with inaccuracies which
were only too severely criticized. Now, how-
ever, the magnificent Central Natural History
Museum of New York has not a few examples
of this new branch of the animal sculptor’s
art, which hardly yield in vividness and
convincingness to the life-like triumphs of
the best of museum taxidermists. Yet even
these are but a beginning; as the evolutionary
mode of presentment increasingly dominates
our collections, as already in the “ Phyletic
Museum ”’ which has been so appropriately
established as the Haeckel memorial at Jena,
or in the central hall of the Natural History
Museum in London, our galleries will in-
creasingly develop their panoramic renewal!
of the forms of life throughout their evolution,
and will thus express the record of the
paleontologist as a wonderland for the child—
whose continual interest in strange beasts, a
delight thrilled with terror, is perhaps itself
a survival and a recapitulation of the past
mental experience of our race.

CHAPTER II

EVIDENCES OF EVOLUTION FROM ANATOMIST,
EMBRYOLOGIST AND PHYSIOLOGIST

Three Foundations of the Doctrine of Descent—Homo-
logies—New Organs from Old—Classification—Vestigial
Structures— The Recapitulation Doctrine. Experi-
mental Evolution—Direct Evidence of Blood-relation-
ship—Man as Transformist.

THREE FOUNDATIONS OF THE DOCTRINE OF
DesceNnt.—The general theory of organic
evolution—for so long conveniently called the
** doctrine of descent ”—has a tripod basis.

(a) It rests, as we have seen, on definitely
* historical"? evidence—on what can be
actually proved in regard to ancestry. Thus
recent discoveries have made the lineage of
the elephant convincingly clear, equalling, if
not surpassing in evidential value that of the
horse itself.

(b) It rests also upon anatomical evidence,
on the disclosure of structural resemblances,
often beneath a mask of functional differences,
which are in many cases so intimate, so
thoroughgoing, so detailed, that it is impossible
to doubt that they spell affiliation.

(c) It rests thirdly upon embryological

evidence, for the individual development
41

42 EVOLUTION

seems almost to go out of its way to reveal the
evolution of the race. The familiar develop-
ment of frog-spawn into tadpoles and froglings
is in some respects almost startling in its
recapitulation of the evolution of the
Amphibian race from fish ancestors—an evo-
lution vouched for by the data of paleontology
and comparative anatomy.

Following the historical order, we pass from
the distributional evidences of evolution—
whether horizontal and geographical, or
vertical and paleontographical—to the ana-
tomical data. These are of three kinds, at
least: (1) there is the recognition of homo-
logies, 7.e. of deeply-rooted structural and
developmental similarities; (2) there are the
facts of classification, that species fades into
species, that genus is linked to genus, that
tentative genealogical trees are possible; and
(83) there is the occurrence of vestigial struc-
tures, of which there is no feasible interpreta-
tion except in terms of past history.

Homo.tocres.—When two or more struc-
tures, organs or speci ialized zed_parts, in one. and

et SR

show a deep resemblance i in. their architecture.
‘and _ also in their manner of development, _
they are said to be homologous. _ When they
resemble one another in having a similar use,

EVIDENCES OF EVOLUTION 48

in discharging the same function, they are
said to be analogous. This distinction of the
two kinds of likeness, which are confused in
popular thought and language, is of far-reach-
ing importance. The discipline of compara-
tive anatomy, largely by help of the Platonic
idea of the “archetype”—the essential or
ideal form of each group or species—had made
the idea of homology clear before it reached
its evolutionist interpretation ; and research
increasingly showed that if classification is
to be a grouping together of forms that are
deeply alike, it must rest on a recognition
ef homologies, and that a grouping according
to analogical resemblances is bound to be
fallacious.

Aristotle (384-322 B.c.) recognized real
kinship when he ranked whales with mammals,
not with fishes; and bats with mammals, not
with birds. And from that early date till
now the successful classifiers of animals or
of plants have been those who saw clearly
through all deceptive suggestions of functional
resemblance (analogy), and got down to the
sure foundation of structural and develop-
mental resemblance (homology).

To make the distinction between homologies
of essential form and mere analogies of use
more concrete, let us recall the three instances

44 | EVOLUTION

of Owen, to whom it owes its classic state-
ment :—
(1) The wing of a bird and the arm of a

mat; they are both fore-limbs, with funda-

meaty the. the same structure as regards bones—
and muscles, nerves and blood-vessels; they

aré homolo ogous, but not analogous.

“(2) The wing o _of a bird and thé-wing o! of a
butterfly;they.are_both.organs.of true_flight,-
but they have no structural or developmental
resemblance ; they are analogous, but not
homologous. ~

(8) The wing of a bird and the wing of
abat; they are both fore-limbs of similar
structure and development; they are both

_.organs-of_true_fiight_; they are at_once homo-_
_logous and analogous...

Now, the evolutionary suggestiveness of
homologies is indisputable. If we take, for
instance, a series of fore-limbs among back-
boned animals—the arm of a frog, the paddle
of a turtle, the wing of a bird, the fore-leg of
a horse, the flipper of a whale, the wing of a
bat, and the arm of man—we find detailed
homology not only as regards the bones, but
as regards muscles, nerves, and blood-vessels.
Throughout there is close similarity in the
fundamental material and in the mode of
origin, but the final results how different!

EVIDENCES OF EVOLUTION 45

There is moulding and shaping and twisting
of the same old materials, and—it is Nature’s
conjuring—there is something new every
time. But the facts being so, it is very
difficult to suggest any interpretation except
one—that the resemblance is due to blood-
relationship. As Darwin said: “ How inex-
plicable is the similar pattern of the hand of
a man, the foot of a dog, the wing of a bat,
the flipper of a seal, on the doctrine of in-
dependent acts of creation! How simply ex-
plained on the principle of the natural selection
of successive slight variations in the diverging
descendants from a single progenitor! ”

New OrGans From O1tp.—Another set of
suggestive facts is found in what the compara-
tive anatomists have shown in regard to many
of the structural novelties which appear at
point after point in the animal series, that
they are old organs in a new guise. The
poison gland of a snake is usually a specializa-
tion of the parotid salivary gland; the milk-
glands of ordinary mammals are specializa-
tions of the sebaceous glands of the skin, while
those of the egg-laying duckmole and spiny
ant-eater are nearer the sweat-gland type;
the chain of three minute bones in the mam-
malian ear, conveying vibrations from the
drum to the inner ear, is in a sense quite new,

46 EVOLUTION

and yet its links were forged long before there
were any mammals; similarly, the Eustachian
tube which runs past the ear to the back of
the mouth in amphibians, reptiles, birds and
mammals corresponds to the first gill-cleft
or spiracle of a shark. Begging the question,
we may state it as one of the laws of evolution
‘that markedly new structures have often
arisen from the transformation of old struc-
tures of quite different function.
CLASSIFICATION.—Some reckon that there
are over a million different species of living
creatures, and, in any case, there are many
myriads. Now these species are, in many
cases, linked together by varieties which make
strict severance difficult. They are like con-
stellations, well-defined at first glance, which
on closer inspection are seen to be connected
by outlying members with adjacent constella-
tions. Moreover, they can be rationally
arranged in genera, orders, families and
classes; yet between these there appear not a
few remarkable connecting links; there is
structural progress from the unicellular organ-
isms upwards along various lines of organiza-
tion; and it is possible to make a provisional
genealogical tree which is becoming less and
less shadowy every year, though the mutual
relations of the larger branches are still very

EVIDENCES OF EVOLUTION 47

obscure. A practical study of the species of
plants and animals, and of the way one
category of classification includes those be-
neath it—classes, orders; orders, families;
families, genera; genera, species; species,
varieties; and varieties, individuals—gives us
*“an impression of affiliation’? which we do
not get from a classification of rocks or other
inanimate objects. It is impossible not to
feel in biological classification the suggestion
of pedigrees and heraldry.

VEsTic1aL StrucTuRES.—Both in plants
and animals it is common to find minute and
more or less useless representatives of organs
which are well developed and functional in
related forms. Itis impossible for us nowadays
to keep from calling these structures vestigial
(a better term than rudimentary, which should
be kept for what is incipient), and from regard-
ing them as the tell-tale evidences of remote
ancestry. Darwin compared them to the
unsounded letters in many words, such as the
““o” in leopard, the “ b” in doubt, the “ g”
in reign, which are quite functionless, but tell
us something about the history of these words.
Every one is familiar with the numerous
functionless flaps and buttons in clothing
which once had a meaning they have now
lost. Similar “ vestigial structures ”’ or “ sur-

48 EVOLUTION

vivals ” persist in the recesses of all manner
of venerable institutions.

From this point of view our own body is a
veritable museum of relics. But these are
not all equally venerable. In the first place,
there are antique structures which are present
only in the embryo, not normally coming to
anything in the adult, as is the case with all
the visceral clefts (or gill-clefts) except the
first, which survives as the Eustachian tube.
In the second place, there are old-fashioned
structures which persist in adult life, but in
much disguised form. Thus the gill-arches,
whose primary significance (in the lower Verte-
brates) was to support gills, persist in our body,
almost unrecognizably transformed, in the
skeletal support of the tongue and in the
framework of the larynx. In the third
place, there are vestigial structures in a
stricter sense, because far more recent—
dwindling residues persistent in adult life,
but either functionless or relatively unim-
portant, such as the minute “ third eyelid ”
which lies in the median angle of our eye, or
the muscles of the ear, which in occasional
individuals are strong enough to move the
trumpet, or the vermiform appendix on the
large intestine. This last anachronism seems
not merely to have outlived its usefulness; it

EVIDENCES OF EVOLUTION 49

often costs a man his life. It is “‘ like an idle
person in a community,” peculiarly liable to
go wrong and give rise to serious mischief. —
Indeed, this is true of not a few other vestigial
organs.

There is no lack of eloquent examples from
the animal kingdom. The baleen whale has
no functional teeth, and yet it has the usual
two sets—which never cut the gum. Whales
have no visible hind-legs, yet many show
vestiges, with bones, cartilages, and even
unmoving muscles, which are buried deep
below the surface and absolutely useless.
Most snakes are absolutely limbless, but in
the boa constrictor and some of its relatives
there are quite distinct hind-legs, though
these are so diminutive as to require looking
for, even on a big specimen.

THe REcAPITULATION DocTRINE.—The
greatest of embryologists, von Baer (1792-
1876), was not an evolutionist, for reasons
which his dates in part explain; yet he was
one of the first to make clear what has always
been eloquently suggestive of evolution—
the remarkable resemblance between the
embryos of different types of the same great
group. Thus, if we take the higher Verte-
brates, viz. reptiles, birds and mammals,
there is an undeniable resemblance between

50 EVOLUTION

their embryonic stages. They seem, as it
were, to travel for a considerable distance
along the same road, or along closely parallel
roads, before they diverge, each on its own
path of development.

It is only in a very general way that we can
accept the late Professor Milnes Marshall’s
epigram, that the individual climbs up its
own genealogical tree; yet there is no doubt
that the development of the individual is in
some measure interpretable as a condensed
recapitulation of the presumed racial evolu-
tion. There is no doubt that in many cases
the developing embryo pursues a strangely
circuitous path instead of progressing straight
towards its goal, and the only light that we
can throw on many instances of this circuitous-
ness—when it is not adaptive to the peculiar
conditions of development—is the light from
the past. The living hand of the past is upon
the embryo, constraining it to follow the old
route of its race, and often reasserting its
power in trivial details, even when a consider-
able short-cut has been made.

Thus in the development of every reptile,
bird and mammal there are residues of gill-
clefts, sometimes imperfectly opening, which
have no respiratory significance whatsoever,
which can hardly be said to be of any use at

EVIDENCES OF EVOLUTION 51

all, except that the first one becomes the
Eustachian tube connecting the ear with the
back of the mouth. There is no known inter-
pretation of these except as recapitulations of
the respiratory apparatus of remote aquatic
ancestors.

Every one is familiar with the bony flat-
fishes, such as plaice, flounder and sole, which
have an asymmetrical body fiattened from
side to side. They rest and swim on their
right or left side, which is unpigmented, and
both eyes are on the upturned pigmented side.
Now these markedly asymmetrical fishes begin
their life with perfect symmetry just like other
fishes. ‘They retain this for some considerable
time and live near the surface. At a certain
stage a very remarkable lop-sidedness of
growth and alteration of equilibrium sets in;
they begin to sink towards the bottom, the
eye on the down-turned side travels round,
or even in part through, the margin of the
head; in short, a metamorphosis occurs.
Different naturalists may read different mean-
ings into the word “ recapitulate,” but in some
sense it is surely true that these flat fishes
recapitulate in their early development the
form of symmetrical ancestors.

We have already referred to the case of the
baleen whale, which has two sets of teeth in

52 EVOLUTION

embryonic life. They never cut the gum,
they are absorbed at a very early stage, they
are not of the slightest use. It appears to us
that in the inheritance of the baleen whale
there must be definite “ representative par-
ticles” corresponding to the typical mam-
malian dentition, that they are still strong
enough to insist on some expression in
development, and that so far as teeth are
concerned the whalebone whale is, therefore,
recapitulating, obviously in much condensed
form, an ancestral condition.

A fish has a two-chambered heart, with an
auricle that receives impure blood from the
body and a ventricle that drives it to the gills.
In amphibians the auricle is divided length-
wise by a partition, so that the heart becomes
three-chambered. In reptiles the ventricle
is partially divided by a similar partition, and
this becomes complete in the case of the
crocodile. In birds and mammals the heart
of the adult is four-chambered, with two
auricles and two ventricles. But when we
inquire into the development of the heart
of the bird or of the mammal, we find a series
of stages which are in a general way parallel
to the historical evolution of the heart as we
see it registered in the successive grades—fish,
amphibian and reptile. The same impression

EVIDENCES OF EVOLUTION 58

is to be gained from a study of the develop-
ment of the brain, the skull, the kidneys, and
other organs. It seems to us impossible to
deny that there is in the stages of organo-
genesis (the development of organs) some sort
of repetition of the stages in the evolution of
organs. The embryo of a higher Vertebrate
has still in some measure to recapitulate the
steps taken by the developing embryo of a
lower Vertebrate; and though we may say
that this is an architectural necessity, that
the end could be reached in no other way, the
facts seem to press us to go further and say
that something in the inheritance, which is
due to literal blood-relationship, compels the
repetition.

Professor T. H. Morgan states the case as
follows :—‘“* The most fundamental difference
between the view of von Baer and modern
views is due to our acceptation of the theory
of evolution, which seems to make it possible
to get a deeper insight into the meaning of
the repetition, that carries us far ahead of
von Baer’s position. For with the acceptance
of this doctrine we have an interpretation of
how it is possible for the embryonic stages of
most members of a group to have the same
form, although they are not identical. There
has been a continuous, although divergent,

54 EVOLUTION

stream of living material, carrying along with
it the substance out of which the similar
embryonic forms are made. As the stream of
embryonic material divided into different
paths it has also changed many of the details,
sometimes even all; but, nevertheless, it has
often retained the same general method of
development that is associated with its par-
ticular composition. We find the likeness,
in the sense of similarity of plan, accounted
for by the inheritance of the same sort of
substance; the differences in the develop-
ment must be accounted for in some other
way.”

In thinking of the repetition or recapitula-
tion there are two distinct ideas to be kept
in mind. On the one hand, each stage in
embryonic development is, as Professor His
put it long ago, “‘ the physiological conse-
quence of the preceding stage and the neces-
sary condition for the following.” “If the
embryo is to reach the complicated end-forms,
it must pass, step by step, through the simpler
ones.”” On the other hand, the inheritance
of a living creature is, in some manner that
we cannot image, a condensation of ancestral
initiatives which are materially represented
in the living substance and compel the
developing embryo to re-tread, to some extent

EVIDENCES OF EVOLUTION 55

at least, the path taken by the embryos of
its ancestors.

Let us take the particular case of the
notochord, a supporting axial rod, present for
some time at least in all Vertebrate embryos,
and always arising in the came way as a fold
along the dorsal median line of the embryonic
gut. In a few old-fashioned types, such as
lancelet and lamprey, there is no backbone,
but the notochord persists throughout life.
From fishes upwards it is gradually replaced
in development by the backbone. The noto-
chord does not become the backbone, but is
replaced by it. The two are quite different
embryologically, the notochord arising from
the inner germinal layer or endoderm, the
backbone arising, like the rest of the internal
skeleton, from the middle germinal layer or
mesoderm. In point of fact, the backbone
develops from a mesodermic sheath around the
notochord, a permanent structure around a
temporary structure, as a tail tower might
be built around an internal scaffolding of wood.
Now, what is the relation between the more
primitive axis or notochord and its more
effective substitute the backbone, seeing that
the former does not become the latter? In
his interesting theory of “‘ the substitution of
organs,” Kleinenberg suggested that the noto-

56 EVOLUTION

chord supplies the stimulus, the necessary
developmental condition, for the formation
of the backbone when suitable materials are
forthcoming. Of course we require to know
more precisely how the old-fashioned structure
prepares the way for and stimulates the
growth of its future substitute, but the general
idea of one organ leading on to another is
suggestive. It is consistent with our general
conception of development—that each stage
supplies the necessary condition for the next;
it helps us to understand more clearly how
new structures, too incipient to be functional,
and old structures, too transitory to be of
direct use, may persist; in short, it makes the
process both of development and of evolution
more intelligible. But to the idea of the
architectural utility of the notochord as a
piece of scaffolding, we must add, unless the
recapitulation is simply metaphorical, the idea
that the notochord is laid down to-day in the
development of a higher Vertebrate because of
a continuity of germinal material since the
days of the ancestral forms which had no
backbone at all.

It must be admitted that the recapitulation
doctrine has been often stated in somewhat
crude and exaggerated form, so that many
saving-clauses are necessary. The human

EVIDENCES OF EVOLUTION 57

embryo is never like a little fish or a little
reptile; the resemblance is between embryonic
stages. The recapitulation is general, not
exact; there is often abbreviation and a
masking of the old by the new. On the one
hand, old-fashioned features may drop out,
having no significance either in embryonic,
larval or adult life; on the other hand, many
new features have been added on as adapta-
tions to novel conditions. The recapitulation
is seen more in the stages in the development
of organs than in the development of the
organism as a whole, and the reason for this is
obviously to be found in the individuality
or specificity of every creature. Increased
precision of embryological work discloses
individual characteristics even in early stages
of development; indeed, a skilled embryolo-
gist (exaggerating a little in his turn) has said
that even a blind man could distinguish
embryos of the duck from those of the fowl as
early as the second or third day of incubation.
The developing frog is in many ways like a
developing fish, for instance, as regards its
heart and circulation, but it is none the less,
from almost the very outset, an amphibian
and nothing else.

It must also be frankly stated that we are
apt to get into a vicious circle in arguing about

58 EVOLUTION

recapitulation. We infer the pedigree from
the development, and then say that the
development recapitulates the pedigree. But
this is not quite so bad as it seems, since no
racial history or phylogeny is worth consider-
ing for a moment that does not show the
anatomical affiliation of actual forms, whether
living or fossil, and embryological investiga-
tion cannot do more than suggest clues.
Again, we consider the eircuitousness of the
frog’s life-history and find in it an evidence
of the reality of recapitulation. We say that
in the development of many of its organs the
frog repeats steps which were taken by the fish
stock from which the race of Amphibians
sprang. We then use this as one of “ the
evidences of evolution’’—which we have
already assumed. But the fallacy here is
simply that we cannot directly demonstrate
the truth of the doctrine of descent; we can
only bring forward facts which suggest it,
and which it serves to interpret.

When all is said, then, there remains good
reason for keeping firm hold of this idea,
which was first cleazly stated in its full
evolutionary importance by Haeckel, first in
his notable “‘ Generelle Morphologie,” and
later in his more popular treatises. This he
termed the “fundamental biogenetic law ”

EVIDENCES OF EVOLUTION 59

that “‘ Ontogeny, or the development of the
individual, is a shortened recapitulation of
phylogeny, or the evolution of the race.”

Even apart from recapitulation, we must
admit the suggestive general fact that the
developing organism passes through a series
of stages, which often differ from one another
in the same sort of way as related species
differ from one another.

EXPERIMENTAL Evo.ution.—In his “* Nova
Atlantis,” that far-sighted Utopia of science
which has already been so largely realized,
Bacon suggested that experiments should
be set agoing in order to discover how far
surroundings can affect and transform living
creatures; and many naturalists have dreamed
of and pleaded for such an Institute of Experi-
mental Evolution. One such has lately been
founded in the United States, the precursor, it
is to be hoped, of many in Europe. “ Since
Nature,” said Isidore Geoffroy Saint-Hilaire,
‘* left to herself never allows us to witness modi-
fications of much magnitude 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.”
Good expositions of the results of various sets

60 EVOLUTION

of experiments will be found in H. De
Varigny’s “‘ Experimental Evolution ” (1892),
and more recently in T. H. Morgan’s “ Experi-
mental Zoology ’’ (1907); and we cannot here
do more than give a few typical illustrations.

In a few cases it has been found possible
to induce experimentally what may be called
an adaptive response. ‘Thus Professor Poul-
ton’s beautiful experiments on the pupz of
certain butterflies show that the colour of
the chrysalid is affected by the colour of the
surroundings, which operates in some mys-
terious way through the skin. When the
pupation occurs on a light background the
chrysalids are lighter; when on a dark back-
ground the chrysalids are darker. This is
undoubtedly an advantageous response, for it
has been proved experimentally that in natural
conditions survival depends in great part on
the inconspicuousness of the pupz in the
place where they are fastened.

In connection with experimentally induced
adaptive responses Professor T. H. Morgan
makes an important note: “ It is remarkable
how rare are adaptive structural responses,
when we recall the fact that adaptation of
the organism to its surroundings is one of its
most characteristic properties. The poverty
of adaptive structural response does not

EVIDENCES OF EVOLUTION 61

encourage one to look to external agents as
having brought about directly the structural
adaptation of organisms to external conditions,
even if it could be shown that such influences
are inherited.”

Many naturalists have experimented with
the pups of butterflies and moths, subjecting
them, for instance, to unusual conditions of
temperature, and many very interesting re-
sults have been reached. In cases where there
are distinct summer and winter adult forms,
the pupa which should give rise to the former
may be made to give rise to the latter, or the
pupa may be affected by cold or by heat so
that what emerges resembles not the local
form of the species, but a northern or southern
variety. Perhaps the most important general
result from our present point of view is that
“the differences effected by changes in the
environment have been shown in some cases
to resemble the kind of differences that
separate species from each other.” This is
suggestive and important, though it does not
by any means prove that species have arisen
in this way.

Mr. J. T. Cunningham put very young
flounders in an aquarium lighted from below,
and observed that as they underwent their
peculiar metamorphosis the pigment first

62 EVOLUTION

disappeared as usual from the down-turned
side, and then (in 11 cases out of 18) re-
_appeared under the unusual stimulus of light
from below. This shows that the normal
absence of pigment on the down-turned side
of a flat-fish is due to the absence of the light-
stimulus in each individual case.

Some .forty years ago Schmankewitsch
made a study of a natural experiment that
occurred in a salt lagoon which was divided
by a dam into an upper and a lower part, the
latter the salter of the two. In a spring flood
in 1871 the waters of the upper part swept
over the dam and reduced the salinity in
the lower part. Thereafter great numbers of
a tiny brine-shrimp, Artemia salina, were
observed in the lower part, having been
presumably washed in. After a time the dam
was repaired, the water gradually regained
its great salinity, and the brine-shrimps in
the course of their rapid generations lost the
well-developed caudal fins characteristic of
Artemia salina and became like another
form without caudal fins, Artemia mil-
hausenii. Passing from observation to experi-
ment, Schmankewitsch found that gradual
concentration of the water led to the replace-
ment of typical forms of Artemia salina by
forms like Artemia milhausenii, and he also

EVIDENCES OF EVOLUTION 68

showed that if the forms without caudal fins
were kept in brine which was gradually
diluted, a pair of conical prominences, each
with a bristle, appeared after some weeks at
the end of the tail. Schmankewitsch did not
regard the change he observed as a trans-
formation of one species into another, and it
seems fairly clear that there is no species
Artemia milhausenii. What he did show was
that alterations in the salinity of the water are,
in the course of generations, followed by slight
changes in the form of the tail. Bateson
and others have shown that there is great
variability in the character of the tail and
bristles of Artemia salina, and that the tailless
form is connected by intermediate stages
with the fully tailed typical form. A careful
discussion of this frequently misstated case
will be found in Bateson’s “ Materials for
the Study of Variation ” (1894).

Direct EvmEeNcE oF Bioop RE.LaTion-
sHip.—Various workers—Friedenthal, Uhlen-
huth and Nuttall—have brought forward
experimental evidence of blood-relationship,
and this in the most complete and literal sense.
Friedenthal points out that when the blood
of a horse is transfused into an ass, that of a
hare into a rabbit, or that of an orang into a
gibbon, or that of man into a chimpanzee,

64 EVOLUTION

there is a harmonious mingling of the two.
But when human blood is transfused into eel,
pigeon, horse, dog, cat, lemur or “non-
anthropoid’”” ape, there is no harmonious
mingling. The human blood serum behaves
in a hostile way to the other blood, causing
great disturbance, marked, for instance, by
the destruction of the red blood corpuscles.
The difference in the two sets of cases is
that in the first the organisms are closely
related, in the second they are not.

Another form of the same kind of experi-
ment is given by Uhlenhuth and Nuttall.
The blood-serum of a rabbit which has had
human blood injected into it forms a precipi-
tate with human blood. It forms almost as
marked a precipitate when it is added to the
blood of an anthropoid ape. As Schwalbe
sums up in the recent Darwin centenary
volume: “‘ The reaction to the blood of the
lower Eastern monkeys is weaker, that to the
Western monkeys weaker still; indeed, in
this last case there is only a slight clouding
after a considerable time and no actual
precipitate. The blood of the Lemuridex
(Nuttall) gives no reaction or an extremely
weak one, that of the other mammals none
whatever. We have in this not only a proof
of the literal blood-relationship between man

EVIDENCES OF EVOLUTION 65

and apes, but the degree of relationship with
the different main groups of apes can be
determined beyond possibility of mistake.”
MAN As TRANSFORMIST.—It is time, how-
ever, to pass from the laboratory to the breed-
ing-pen and experimental plot, to recall the
very striking transformations that man, by
selective breeding, has effected in his domesti-
cated animals and cultivated plants. Darwin
pointed to what has taken place in the case
of sheep and cattle, cabbages and apples, and
a score of other cases, and pressed home the
question: If Man has been instrumental in fix- _
ing all these varieties in a short time, what may
hot Nature have effected in a very long time? __
There are over two hundred very well-
marked breeds of domestic pigeons, and there
are at least ten that would be ranked as
distinct genera if they occurred wild; yet
there is very strong evidence that all are
scions of the blue rock-dove, Columba livia.
In the same way there is very strong evidence
that all the breeds of poultry—Hamburghs
and Dorkings, Bantams and Silk-fowl, and all
the rest of them, are descended from the
jungle-fowl, Gallus bankiva, still found wild
in some parts of India and the Malay Islands.
Since the canary was introduced into Europe

about the middle of the sixteenth century,
c

66 EVOLUTION

over a dozen very distinctive races have been
established ; and of course varieties for “‘ the
fancy ”’ without end.

It is a remarkable fact that, in spite of the
accuracy, assiduity and collecting acquisitive-
ness which characterize botanical systematists,
we know very little that is quite certain about
the pedigrees of cultivated plants. As De
Vries says: “ The origin and history of the
greater part of our garden flowers, fruits and
vegetables are obscure; we see them as they
are, and do not know whence they came. The
original habitat for a whole genus or for a
species at large may be known, but questions
as to the origin of the single forms of which it
is built up ordinarily remain unanswered.”

But in spite of obscurities as to origin, the
evolution of cultivated plants is still going
on before our eyes. Whether we visit the
nearest country flower-show, or admire from
enchanting distance Mr. Burbank’s latest
creations—the “ primus berry,” the “ phe-
nomenal berry,” the “ Bartlett plum,” the
spineless cactus, and the rest, or see the
Mendelian experimenters positively manipu-
lating the inheritances of our cereals, we
cannot doubt that we are in the presence of
evolution in actual process.

It is necessary, however, to point out that

EVIDENCES OF EVOLUTION 67

the results of Mendelian experiments have
somewhat modified our view of what man is
able to achieve in the way of establishing new
breeds. In many cases it seems as if he were
only assisting in the “unpacking” of the
extremely complex inheritance of the wild
type. It may seem that new peculiarities
are emerging, but in many cases what is being
effected is a process of analysis and of selection.
There seems to be no doubt, for instance, that
the colour-varieties of domestic rabbit are
but analyzed in varying measure and mixture
from that beautiful synthesis of hues which we
see in the wild rabbit. As similar analytical
varieties probably occur in Nature, the facts
of domestication may retain their position
among the “ evidences of evolution,” though
our interpretation of many of them is being
altered by the Mendelians.
In this case, and throughout all consideration |
of evidences” Te must I be remembered that
the evolution idea cannot be logically demon-
strated. It is not a simple mduction’ from
particulars, thoroughly a8 particulars
it, It isa way of looking at the becoming™
of things; and it is the only scientific modal
interpretation that has been suggested. It
is a formula that fits the facts, and all the —
facts it fits ate its “evidences.”
C2

68 EVOLUTION

CHAPTER III

GREAT STEPS IN EVOLUTION

Evolution a great Succession of Achievements—The Begin-
nings — Protoplasm and Organisms — Characteristic
Features of Living Creatures—Origins among the
phe reer Se Serie ga pare eee
TTS Orig 0 Son The Beginaiage of Beins—The

innings of Behaviour—Progress along many Lines—
The Ascent of Vertebrates—The Ascent of Man—Evolu-
tion as Retrogressive—Deterioration and Parasitism.

EVOLUTION A GREAT SUCCESSION OF

ACHIEVEMENTS.—It is impossible to appre-

ciate our own human position aright unless

we see it in the light of history. We must
think of the distant stone ages—when man
made weapons of chipped flints and then of
polished stone; of the prehistoric metal
ages that followed—-when man made weapons
and utensils of copper, of bronze, and then
of iron; and of the gradual growth of
civilization along many lines. We are so
familiar with the result that we are apt not
to think enough of the long succession of
achievements—each a great event in human
history. It is one of the uses of a museum,
provided it be on evolutionary lines, like the

Pitt Rivers Museum at Oxford, to give us

detailed pictures of the state of things in age

after age. We must have a series of human

GREAT STEPS IN EVOLUTION 69

skulls, a series of weapons—a series of every-
thing that has evolved.

Similarly, Go one can adequately appre-
ciate a fully-formed creature, whether an
oak tree or the bird on its branches, a frog
or an eel, a butterfly or a starfish, who does
not know the stages of its individual develop-
ment, from the apparent simplicity of the
fertilized egg-cell onwards. Looking down
from the summit of a pass which it has taken
us all day to reach, we see the village in
the valley from which we started at day-
break, and it seems like a great stone’s-throw
off. The dips and ascents, turns and twists,
of our path are all lost to sight; only those
who have walked over it know what the
climb has really been. So it is with a retro-
spect on evolution) | |

It is an easy thing for us to say that the
world of life we see around us to-day has
evolved ; with equal ease our grandparents
said that it had been created. But it is
incumbent on the able-minded to give to this
doctrine of descent a solid body of fact, so
that they may realize something of the
grandeur and, let us add, of the difficulty of
the proposition. In other volumes of this
series the student will be helped to fill in
some of the details of the evolution chart,

70 EVOLUTION

thus Dr. Scott deals with the pedigree of
Plants, Professor Gamble with Animal Life,
Dr. Keith and Mr. Marett between them
with man; what we propose in this chapter.
is to indicate in a general way a few of the
great steps in Organic Evolution.

THE Brecinnincs.—Until the earth cooled
and consolidated it was quite unfit to be a
home of life. It follows that at some un-
certain, but inconceivably distant date, living
creatures appeared on the scene. The ques-
tion is: What was the manner of their be-
coming upon the previously tenantless earth ?
Our answer must be that we do not know.
But to obviate worse answers we may submit
two or three suggestions.

It may be that germs of life came to our
earth embosomed in meteorites. This was
the suggestion of Richter, Helmholtz and
Lord Kelvin. But it is difficult to conceive
of anything like the protoplasm we know
surviving transport in a meteorite.

Some authorities who have found satisfac-
tion in the meteorite-vehicle theory have also
suggested that life isas old as matter. It must
be noted, however, that the life we know is
always associated with highly complex sub-
stances known as proteids, which are more like
termini than beginnings in material evolution.

GREAT STEPS IN EVOLUTION 71

It may be that what we call “living”
evolved in Nature’s laboratory from what
we call “ not-living,” for though prolonged
experiments have led biologists to adhere
dogmatically to the dictum ‘‘omne vivum e
vivo,” this is not inconsistent with supposing
that spontaneous generation occurred in
favourable conditions very longago. Verworn
has elaborated a suggestion due to the great
physiologist Pfliiger (1875), that the cyanogen
radical (CN) may have been the starting-
point of the proteid molecule which is the
essential part of the physical basis of life.
As cyanogen and its compounds arise in
an incandescent heat when the necessary
nitrogenous compounds are present, they may
have been formed while the earth was still
aglow; with their property of ready decom-
position they were forced into correlation
with various other compounds likewise due
to the great heat; when water was precipi-
tated upon the earth these compounds entered
into chemical relations with the water and
its dissolved salts and gases, and thus origin-
ated extremely labile, very simple, undiffer-
entiated living substance, which perhaps fed,
as Sir Ray Lankester has suggested, upon
** antecedent steps in its own evolution.”

It must be note awever, (1) that although

72 EVOLUTION

the synthetic chemist can now manufacture
artificially such natural organic products as
urea, alcohol, grape sugar, indigo, oxalic acid,
tartaric acid, salicylic acid and caffeine, he
has _not yet come near the artificial syn-
thesis of proteids; (2) that we are at a loss
to suggest what, in Nature’s as yet very
hypothetical laboratory of chemical synthesis,
could take the place of the directive chemist;
and (8) that there is a great gap between
making organic matter and making an
organism.

It is plain, therefore, that the doctrine of
the origin of the living from the not-living
cannot be held at present with a clear or
easy mind, yet we must admit that as an
hypothesis it is in harmony with the general
trend of evolutionary theory. If facts
accumulate which make the hypothesis a
tenable interpretation, it will not in any way
affect the dignity and value of living creatures,
nor of our own life. If the dust of the earth
did naturally give rise to living creatures, if
they are in a real sense born of her and
the sunshine, then the whole world becomes
more continuous and vital, and all the in-
organic groaning and travailing becomes
more intelligible.

PROTOPLASM AND ORGANISMS.—If we whip

GREAT STEPS IN EVOLUTION 7

up in a tumbler some white of egg, some
yolk of egg, some casein from milk, and so
on, we have got a mixture of proteids, one
excellent to feed protoplasm with, but we
have not got protoplasm itself. Our tumbler-
mixture is only a fortuitous concourse of
proteids; whereas protoplasm is an integrate
of proteids, perhaps with fats and amyloids as
well—a fortunate combination of molecules in
instable, even mobile, yet enduring equilibrium.

It is probable that the potency of living
matter is in part an expression of the com-
plex inter-relations of the diverse proteids
and other substances of which it is com-
posed. No single substance may mean very
much, but in combination they are irresistible.
Indeed we may compare protoplasm to a
successful firm which owes its success to an
unusually fortunate combination of partners
—of inventive, organizing, administrating,
pushing, competitive and other geniuses !

But there is something more. The firm
works as a unity, and this is its essential
secret. It is unified from within, whether
by a common purpose, or by the predominant
will of its leading partners, or by something
of both. And the organism has likewise its
secret, its internal unity, which we are still
far from understanding.

74 EVOLUTION

CHARACTERISTIC FEATURES OF LIVING
CREATURES.—The chemists tell us that the
physical basis of life always includes proteids
and similar highly complex substances, and
that the process of living involves an intricate
series of combustions and fermentations and
reconstructions, many of which can be
imitated outside the body altogether and
expressed in chemical formule. On the other
hand we cannot give a chemical description
of any complete vital function, or of any
activity of the living creature as a whole—
and unless, as the Germans say, we throw
away the baby with the bath, we cannot
ignore the most salient fact, that all the
manifold chemical processes are correlated
and controlled in a unified behaviour, in a
purposive agency. Even the amceba is no
fool.

The physicists tell us that the living creature
resembles some wonderful kind of engine; it
is a material system adapted to transform
matter and energy; and it illustrates in its
living a number of well-known physical pheno-
mena, of surface-tension, of diffusion, of
. elasticity, of hydrostatics, of thermodynamics,
of electricity, and so on. At the same time
it has to be admitted that not even the
simplest vital activity, such as the passage

GREAT STEPS IN EVOLUTION 7%

of digested food from the alimentary canal
into the blood-vessels, can be completely
described in terms of physical formule. The
fact is that when we add up the components
revealed by chemical and physical analysis,
they do not amount to the whole resultant
which we see in a vital action, even of a
simple sort.

It is indeed profitable to compare a living
creature to a machine, and a fertile method
of discovery to press this comparison to its
hardest. Yet the living organism differs
from any machine in its greater efficiency;
and especially in this, that the transfer of
energy into it is attended with effects con-
ducive to further transfer and retardative
of dissipation. Again in this, that it is a
self-stoking, self-repairing, self-preservative,
self-adjusting, self-increasing, self-reproducing
engine! And this also must be remembered
in comparing a living creature and a machine,
that the latter is no ordinary sample of the
inorganic world. It is an elaborated tool,
an extended hand, and has inside of it a
human thought. It is because of these
qualities that highly complex machines come
to be so like organisms. But no machine
profits by experience, nor trades with time
as organisms do. Therefore it is that the

76 EVOLUTION

formule that serve to describe the activity
of a machine will not suffice for living creatures
which demand an historical explanation,
When we leave the chemical and physical
standpoint, and look at the living creature as
biologists, we recognize four chief character-
istics—growth, cyclical development, effective
response, and unified behaviour. The living
ereature grows after a fashion all its own,
not as a rolling snowball, by mere accretion,
but by a unifying incorporation; not even as
a crystal grows, at the expense of dissolved
material chemically the same as itself, but at
the expense of material different from itself.
Again, it has a cyclical development, from
egg-cell to seedling, from seedling to bean-
stalk; from egg-cell to tadpole, from tadpole
to frog; it shows an orderly, correlated, regu-
lated succession of events, which leads from
apparent simplicity to obvious complexity;
but, as Huxley puts it, “no sooner has the
edifice, reared with such exact elaboration,
attained completeness, than it begins to
crumble.”” Inanimate objects have a certain
power of response to external stimuli, as a
piece of potassium shows when thrown on
a basin of water, but the responses of.a living
creature in normal surroundings are effective,
self-preservative, usually making for better-

GREAT STEPS IN EVOLUTION 77

ment. Lastly, the living creature has a
persistent unified behaviour, a power of
profiting by experience, a creative capacity
as a genuine agent. .
ORIGINS AMONG THE Protozoa.—It is well
over two centuries since the Dutch microscop-
ist, Leeuwenhoek, exhibited to the Royal
Society of London some of those unicellular
animals or animalcules which we now call
Protozoa—the Fellows present signing an
affidavit that they had really seen the minute
creatures. This was the beginning of a study
which has been extraordinarily fertile in itself
and in its bearing on other lines of research.
As has become so emphatic recently, the study
is one of enormous practical importance to
man, since some of the most terrible diseases,
such as malaria and sleeping sickness, are
due to Protozoa, but the study is also of
fundamental theoretical importance. For the
Protozoa give us, so to speak, a natural
analysis of the elements which compose the
higher animals; the phases of their life-cycles
are sometimes echoed in the cellular variations
of man himself; a few of them seem to linger
in a state of relative simplicity, approximat-
ing to that which must have characterized
the true Protozoa, or first animals; they are,
as it were, permanent germ-cells which never

78 EVOLUTION

get beyond the ovum and sperm stage; and
they show us the beginnings of division of
labour and its structural aspect which we call
differentiation, the beginnings of sex and of
reproduction, the beginnings of a body and
of death. ‘“* Protozoology,” as it is quaintly
called nowadays, is a fascinating study in
origins.

THe Prorists.—It is useful to retain
Haeckel’s term “ Protists ’” for those simplest
of all living creatures, which lie at the base of
the V-shaped tree of life, showing no definite
bias towards distinctively plant or distinct-
ively animal characteristics. How far re-
moved even these simplest of the simple may
be from the first living creatures we do not
know, but they have remained, as it were,
in chronic indecision, neither clearly plants nor
animals. In studying them we are brought
face to face with one of the great steps in
evolution, and one of the earliest—a dicho-
tomy, like many other great steps—the
parting of the ways between plants and
animals,

PLANTS AND ANIMALS.—We have all grown
up with our minds coloured by the childish
game of “ Animal, Vegetable or Mineral ? ”
and in too many schools they still teach that
there are three kingdoms of Nature. But

GREAT STEPS IN EVOLUTION 79

this is a surviving error of the alchemists,
continued by the early encyclopedists of
nature, but broken down by Linnzeus, who
clearly discerned that there are only two:
the living and the non-living, the truly organ-
ized and the merely aggregated. Hence in
his immortal ‘ System of Nature” he unites
Animalia and Vegetabilia as Organisata, and
separates Mineralia as Conserta. True, he
falls somewhat from this again, witness his
famous, but very fallacious, aphorism—
“Minerals grow; Plants grow and _ live;
Animals grow, live and feel”’; yet the great
distinction of life is not lost sight of.

Since Claude Bernard, more than a genera-
tion ago, wrote his famous book, ‘* Phéno-
ménes de la vie communs aux animaux et
aux végétaux,” it has been recognized that
the beech-tree feeds and grows, digests and
breathes, as really as does the squirrel on its
branches; that in regard to none of the main
functions (except excretion, which plants have
little of) is there any essential difference; and
that plants, though for the most part, as
it were, asleep, give many striking illustra-
tions of their power of movement and their
irritability.

We must remember also that plants and
animals are alike in fundamental architecture,

80 EVOLUTION

being built up of cells and various modifica-
tions of cells. And there is a third deep
resemblance, that when we trace a_beech-
tree or a squirrel back to its individual begin-
ning we find a fertilized egg-cell, which
divides and re-divides, the body of the plant
or animal being built up by continued division,
arrangement and differentiation of cells.
But important as these resemblances between
plants and animals are, the divergence is very
profound and expresses one of the great
cleavages in evolution.

It came about through the invention of
chlorophyll by some Protists—a chemical
and physiological achievement of the highest
magnitude, which made the life of plants
possible, and, through them, that of animals
and man. In the complex “‘photo-synthesis”
' by which plants build up complex carbon-
compounds from the raw materials of water,
air and earth, chlorophyll plays an indispens-
able part. The still widely prevalent ignorance
of this fundamental process of the living
world is perhaps the greatest example of the
slowness with which the discoveries of science
become generally recognized.

Most plants derive the carbon they require
from the carbon dioxide of the air, while
only a few (green) animals have this power;

GREAT STEPS IN EVOLUTION 81

all the others depend for their carbon supplies
on the sugar, starch, fat, etc., already made
by other animals or by plants. As regards
nitrogen, most plants take this from nitrates
and the like, absorbed along with water by
the roots; whereas animals obtain their
nitrogenous supplies from the complex pro-
teids formed within other organisms. Most
plants, therefore, feed at a lower chemical
level than do animals, and it is characteristic
of them that, in the reduction of carbon
dioxide and in the manufacture of starch
and proteids, the kinetic energy of sunlight is
transformed by the living matter into the
potential chemical energy of complex food-
stuffs. Animals, on the other hand, get their
food ready-made; they take the pounds
which plants have, as it were, accumulated
in pence, and they spend them. For it is
characteristic of animals that they explosively
convert the potential chemical energy of food-
stuffs into the kinetic energy of locomotion
and other activities. In short, the great dis-
tinction—an average one at best—is that
most animals are more active than most plants.

Changing the point of view a little, we may
notice that, because of their mode of nutrition,
typical animals are bound to be active and
locomotor either in whole or in part. Similarly

}

|

82 EVOLUTION

we may say that the plant-cell, by shutting
itself up in a wall of cellulose, instead of
fully oxidizing this substance, and perhaps
also by less efficient elimination of nitro-
genous waste, doomed itself to fixity and to
sleep. Yet something of the animal impulse
of the ancestral Protists lingers in the plant,
and something of the vegetative tendency of
the ancestral Protist lingers in the animal.
We have dwelt for a little on this elementary
question of the distinctions between plants
and animals, because it is the fundamental
illustration of a bifurcation that has recurred
many times in the evolution of living creatures.
Living implies two great processes—of re-
pairing and wasting, of building up and
breaking down, of construction and dis-
ruption—more technically, of anabolism and
katabolism. Given a typical plant and
animal of equal weight, both living normally,
we might safely say that the animal lives
much more nearly up to its income than the
plant does. If we express the vital ratio of

anabolism to katabolism as 2 for the plant

and - for the animal, we may safely say

that 2 is always much greater than ~. In

GREAT STEPS IN EVOLUTION 88

the plant the numerator is always large in pro-
portion to the denominator. In the animal
there is a relative preponderance of kata-
bolic processes. Thus at point after point in
the history of organisms the evolving Proteus
has had to face the alternatives of two
possible regimes precisely corresponding to
the alternatives between Plant and Animal
in the earliest days.

THe Cetu-CycLte.—When we take a survey
of a representative set of unicellular organisms
—amecebe, foraminifers, sun-animalcules, in-
fusorians, gregarines, and simple alge and
fungi as well, we reach, almost by inspection,
a rough and ready tripartite classification
into very active and very passive forms, with
amceboid forms midway. At one extreme
are the highly active infusorians, such as the
widely diffused free-living slipper-animalcules,
or the widely diffused parasitic trypanosomes
(one of which causes sleeping-sickness); at the
opposite extreme are quiescent forms, in which
the life seems to sleep; between the two
the amceboid forms have evolved along a
via media—a compromise between extreme
activity and extreme passivity.

If we go deeper than mere inspection and
study the life-history of the very simplest
forms, such as some of the primitive Proteo-

84 EVOLUTION

myxa and Myxomycetes, we get a new light
on our classification. For in these life-
histories we find, for instance, that amceboid
forms become encysted, that the encysted stage
gives rise to active flagellate spores, and that
these sink down again into amcebe. The
three chapters in the life-history of the
simplest forms are, as it were, prophecies of
each of the three groups—Infusorians, Rhizo-
pods, and Gregarines. In other words, the most
primitive organisms pass through a cycle of
three phases, one of which is accented by each |
of the three main groups of Protozoa. And
while each main group is characterized by one
dominant phase of cell-life—flagellate, amce-
boid or encysted—there are often transient
hints of other phases. An infusorian may
have its encysted chapter, a gregarine its
amoeboid stage, and a rhizopod may begin as
a mobile flagellate spore; for each group,
- while accenting one phase of the cycle, retains
reminiscences of the others.

The conviction that the triple division really
means much, grows stronger when we pass
from the unicellulars to the cells that compose
the higher animals. For they, too, may be
rationally classified along the three great lines.
There are active ciliated or flagellate cells in
most animal types—the flagellate cells of

GREAT STEPS IN EVOLUTION 85

sponges, the “‘ flame-cells ”’ of the lower worms,
the ciliated epithelium lining our air-passages,
being three familiar illustrations. The white
blood corpuscles are obviously comparable to
amcebe. Passive encysted cells are illus-
trated in some forms of connective, skeletal
and fatty tissue. Thus the physiological
classification of the Protozoa is verified in the
histology of the higher animals, and is further
corroborated in the study of their diseases.
In a certain kind of “sore throat” the
ciliated cells of the windpipe sink into an
amoeboid phase, echoing a normal change in
the life-history of the simplest Protists. The
young ovum is often amceboid, the mature
ovum is encysted; the typical spermatozoon
is flagellate, but there are some exceptional
amceboid forms. Finally, the same cell-
cycle is not only recognizable in the repro-
duction of the lower plants, but is plain in the
higher cryptogam, and vestigial in the flower.
And the deep significance and historical
importance of the lines of differentiation indi-
cated by the cell-cycle become more evident
still when we recognize that the three phases
correspond to the three possibilities of rela-
tively preponderant anabolism, relatively
predominant katabolism, and a compromise
between these two.

86 EVOLUTION

THE BEGINNING oF A Bopy.—The simplest
organisms are single cells physiologically com-
plete in themselves; they leave off where
higher creatures begin, that is to say, in a
unicellular state; they do not form “ bodies.”
Here we have perhaps the greatest gap and
the greatest step in organic nature, that
between single-celled and many-celled organ-
isms. It is very interesting to inquire into
the beginning of a “ body.” What are the
possibilities ?

We know of some simple units that have a
habit of coalescing into composite masses, of
others in which the nucleus divides over and
over again within the cell so that multi-
nucleate organisms are formed, and of others
again that break their definition, and do their
best to get beyond the unicellular state, by
forming loose colonies. It was probably in
the third of these ways that body-making
began. Certain simple organisms, unable
fully to complete that division into two or
more separate units which normally occurs
at the limit of growth, bridged what Agassiz
called ‘“‘the greatest gulf in organic nature.”
It was perhaps through some weakness that
the daughter-units, formed by division of
the mother-cell, remained associated, instead
of drifting apart in individual completeness.

GREAT STEPS IN EVOLUTION 87

But out of this weakness—if weakness—
strength arose, the strength of animals
with a body.

BEGINNING OF DeEatH.—In a. startling
phrase—the immortality of the Protozoa—
Weismann called attention to the fact that
unicellular organisms are not subject to
natural death in the same degree as higher
animals are. They may be killed, of course,
in many ways, but they do not normally die.
Even against microbic infection many of them
seem proof; they digest the virulent intruders,
as do the phagocytes which form our body-
guard. But the point is, that in natural
conditions, where inter-crossing, for instance,
is readily feasible, they appear to be exempt
from that natural death which in the higher
organisms is due to the slow mounting-up of
physiological arrears.

How is it that these simple pioneer organ-
isms are exempt from the penalty all other
flesh is heir to? The answer is twofold. On
the one hand, being relatively very simple,
in a strict sense without a “ body ”—they are
able to sustain with persistent success the
vital equation between waste and repair. On
the other hand, their common mode of repro-
duction, by dividing into two or more units,
is inexpensive and not attended with any loss

88 EVOLUTION

of life. For although the individual A dis-
appears in giving rise to B and C, its daughter-
cells, we can hardly speak of death when there
is nothing left to bury. On the one hand, we
reach the idea that death was the price paid
for a body; on the other hand, we see that in
the simplest forms of life immortality has not
even yet been pawned for love.

Tse Onicin or Sex.—In many of the uni-
cellular organisms there is a kind of sexual
reproduction, in the sense that two cells fuse
to become one, just as ovum and spermatozoon
do in higher creatures. In many cases, more-
over, the two cells which fuse are dimorphie,
as is well illustrated in the bell-animalcule,
Vorticella, where a small, active, free-swim-
ming (we may say, male) cell unites with a
fixed individual of full size, which may be
called female. This is one line of approach
to the origin of sex, and it may be noted that
the male and female cells illustrate the anti-
thesis we have already discussed between
relatively more anabolic and relatively more
katabolic types.

The next stage in the problem is to account
forthe familiar fact that in almost all organisms
with bodies there are special reproductive
cells, or germ-cells—ova and spermatozoa—
quite distinct from the ordinary body-cells.

GREAT STEPS IN EVOLUTION 89

This is an economical improvement on the
method of starting a new life by a sexual over-
growth or by the liberation of buds. More-
over, the peculiarity of true germ-cells is that
they do not share in building up the “ body,”
and that they retain an organization contin-
uous in quality with the original germ-cell
from which the parent arose. They are thus
not very liable to be tainted by the mishaps
which may befall the “‘ body ” which bears
them. And again, in the life-history of the
germ-cells, and in the mingling of two of them
of different experiences in fertilization, there
is apparently opportunity for new organic
permutations and combinations—variations
in short. Perhaps there is some subtler
advantage still in the process which ensures
that each new life usually begins in a unifica-
tion of two inheritances.

The third aspect of the problem is that
most multicellular organisms are males or
females. The former liberate male elements,
which are usually actively motile; the latter
form, and usually liberate, more passive egg-
cells or ova. In the lower reaches of the
animal kingdom there is seldom much differ-
ence between males and females; indeed, it is
often impossible to distinguish the two sexes
without a microscopic examination of the

90 EVOLUTION

reproductive organs. It is obviously at this
level, and not with the highly specialized sex
dimorphism of peacock and peahen, ruff and
reeve, lion and lioness, man and woman, that
the problem should be first studied.

The problem is partly solved by considering
the simplest expressions of the sex-difference,
as we see it, for instance, in Volvox, an inter-
esting colonial Infusorian, which well illustrates
a body in the making. It is a beautiful rolling
ball of ciliated cells, and these component
units are connected by protoplasmic bridges.
From the ball of cells reproductive units are
sometimes set adrift, which divide to form
other colonies without more ado. But in
other conditions, when nutrition is checked, a
less direct mood of reproduction occurs. Some
of the cells in the ball become large, well-fed
elements—the ova; others, less anabolic, fade
from green to yellow, divide and re-divide into
many minute units—the spermatozoa. The
large cells of one colony are fertilized by
the small cells from another. Here we see
the formation of dimorphic reproductive cells
in different parts of the same organism. But
we may also find Volvox balls in which only
ova are produced, and others in which only
sperms are produced. ‘The former seem to be
more vegetative and nutritive than the latter;

GREAT STEPS IN EVOLUTION 91

we call them female and male organisms
respectively; we are at the foundation of
the differences between the two sexes.

Again we would state our thesis that all
through the animal series, from active Infu-
sorians and passive Gregarines, to feverish
Birds and sluggish Reptiles, we read alterna-
tives or antitheses between activity and pas-
sivity, between liberal expenditure of energy
and a more conservative habit of storing.
This primarily depends on the ratio between
disruptive (katabolic) processes and con-
structive (anabolic) processes, and we regard
the sexes as expressions of the same contrast
within a given species. And donot kindred yet
contrasted forms, like goat and sheep, wasp
and bee, butterfly and moth, seem, as it were,
but the extreme expression of the same indi-
vidual and sex contrasts carried farther, upon
the plane of species, of genus, of order, or of
class?

According to this view the deep constitu-
tional difference between the male and the
female organism, which makes of the one a
sperm-producer and of the other an egg-pro-
ducer, is due to an initial difference in the
balance of chemical changes. The female
seems to be relatively the more construc-
tive, whence her greater capacity for organic

92 EVOLUTION

sacrifices in maternity; the male relatively
the more disruptive, whence his usually more
vivid life, his explosive energies in action.
In short, the sexes express a fundamental
difference in the rhythm of metabolism.

This initial difference not only leads to the
primary functional distinction between male
and female, but it also determines, either
from the start, or after maleness and female-
ness have been partly established, what par-
ticular expression will be given to a whole
series of secondary characters,—both struc-
tural and functional—whether a masculine
or a feminine expression.

THE BrGINNINGS OF Brains.—In most
sponges and ccelenterates (such as jelly-fish,
sea-anemones and coral polyps) the body
has radial symmetry. That is to say, it is
the same all round, it has no right nor left, it
can be cut into symmetrical halves along
many different vertical planes. This kind of
symmetry is well suited for sedentary life,
like that of sea-anemones, which wait for
food to come within the scope of their sting-
ing and grasping tentacles; or for an easy-
going life, like that of jelly-fishes, which live
in the very uniform environment of the open
sea where all directions mean very much the
same.

GREAT STEPS IN EVOLUTION 98

For conditions of more active and strenuous
life, however, where it is important to chase
the food, to flee from enemies, to pursue mates,
and so on, radial symmetry is unsuitable, and
it is replaced by bilateral symmetry. This ac-
quisition of head end and tail end, of right side
and left side, was doubtless of enormous im-
portance, both in itself and in its consequences,
which include our knowing our right hand
from our left.

It is likely that certain “ worms ”’ were the
first animals definitely to abandon the more
primitive radial symmetry, to begin moving
with one part of the body always in front, to
acquire head and sides. And if one end of
the body constantly experienced the first
impressions of external objects, it seems
reasonable to suppose that sensitive and nerv-
ous cells would be most developed in that
much-stimulated, and otherwise over-educated,
head region. But a brain always arises from
the sinking in of ectodermic cells from the
surface of the embryo, and its beginning in
the cerebral ganglion of the simplest “‘ worms ”
is thus in part explained. It is difficult to
over-estimate the importance of the establish-
ment of an anterior brain—a chief motor and
sensory and co-ordinating nerve-centre—and
the consequent evolution of a head.

94 EVOLUTION

THE BEGINNINGS OF BEHAvIOUR.—Jen-
nings has shown that some unicellular animals
“behave ” in a very definite way. They are
not mere automata which rush about as long
as their spring keeps unrolling, and they are
more than the mere slaves of stimulus. Ther
are some, it is true, which seem to have only

one kind of reaction to every kind of stimulus,
only one answer to every question, but ‘there —
are others whose behaviour is at a higher
level, illustrating what may be called “thé
method of trial and error.” “They try” one
kind of reaction after another, until, in some
cases, they give the effective response.

But while we cannot doubt that the be-
ginnings of behaviour are to be found in the
Protozoa, new possibilities must have opened
up whenever head-brains were established.
For this centralizing of the nervous system
must have meant a new integration, a more
unified control, of the whole organism.

We cannot attempt to summarize the
discernible steps in the evolution of behaviour,
but we wish to press home the fact that what
we are so familiar with to-day is the long
result of time. We see behaviour rising, along
one line, to its wonderful instinctive expres-
sions. We see it rising (whether further or
along another line is still under discussion)

GREAT STEPS IN EVOLUTION 95

into intelligent expression where there is
perceptual inference. Finally, in man, with
his conceptual inferences, intelligent behaviour
becomes rational conduct.

PRoGRESS ALONG MANY Lines.—In his
interesting “ Evolution of Plants,” Dr. Scott
refers to the important fact that at a time so
remote as the Devonian period, when there
were no backboned animals higher than fishes,
a very high level of organization had been
reached by the plants. There were in those
days ferns and horsetails, club-mosses and
Pteridosperms, and many other plants of
high degree; what has happened since has
been specialization rather than great advance.
It is true that the fern-like Pteridosperms gave
rise to the world-wide Mesozoic Cycadophytes,
and, in still later times, to the true Flowering
Plants, but there was no great new organic
invention like that of the seed, for which the
flower is but the protean birth-robe. Since
that, progress has been in the intensive
colonization of the earth and in detailed
adaptations, vegetative and floral, manifold
and exquisite.

In thinking of this, we must remember, in
the first place, that while the Devonian period
is inconceivably remote, there was an equally
inconceivable stretch of ages before it, during

96 EVOLUTION

which there must have been many a great
step among plants as well as among animals.
In the second place, the fact that plants
have made no such very great advance since
the Devonian period, whereas animals have
risen by stride after stride to higher and
higher levels of organization, is congruent
with the deep contrast between plants and
animals to which we have already referred.
It is not merely that plants in their struc-
tural relations remain about the level of
Ceelentera among animals; it is that they
are on an entirely different line of evolution.
Plants and animals are incommensurable and
antithetic.

If we take a series of sedentary animals,
such as zoophytes or alcyonarian corals, we
find, as in plants, a wealth of variety within
narrow range, an exhausting of the possi-
bilities of ramification and colony-making, a
great development of hard supporting parts,
and many nice adjustments to slight environ-
mental peculiarities. They and the plants
have a similar kind of beauty—expressing the
dream-smiles of their’ sleep-like life.

How different this is from what we see
among the free-living animals—which made
one important step after another. Keeping
to backboneless animals for the moment, let

GREAT STEPS IN EVOLUTION 97

us notice some of the great acquisitions—
bilateral symmetry, a head-brain, specialized
sense-organs, a body-cavity, a segmented
body, muscular feet, a renewable external
armour, muscular jointed appendages, and so
on. Or let us think of particular cases such
as the extraordinary development of the re-
spiratory system in insects, where ramifying
tubes carry air to every nook and cranny of
the body, so that the blood can hardly ever
become impure, and a climax of vital activity
is attained. The story of the evolution of
Invertebrates is a succession of great achieve-
ments. Among Vertebrates they were even
greater.

THE ASCENT OF VERTEBRATES.—It is a
profitable exercise to draw a long ascending
slope, with perpendiculars dropped from
various points to the base line, registering the
evolutionary ascent of Vertebrate animals.
What are the impressive facts? (1) Life has
been creeping or pressing upwards for many
millions of years. (2) Great specializations
occur at every level, but there is also beyond
doubt a progressive differentiation and in-
tegration. (3) This is particularly true of
the nervous system, and is of course a con-
dition and expression of the gradual increase -

of intelligent behaviour. Life becomes richer
D

98 EVOLUTION

and freer. (4) Increased individuation makes
reproductive economy possible. Parental care
increases, and the number of offspring de-
creases. There is an emergence of the finer
feelings, and fondness is sublimed in love.
(5) There has been an interesting peopling
of the earth, an establishment of faunas
distinctive of the shore, the open sea, the
deep sea, the fresh waters, and the air.
Amphibians mark the important transition
from water to dry land ; the ancient Ptero-
dactyls mark the mastery of the air in which
Birds and Bats are now most at home. But
hardly less impressive is the possessing of
every nook and corner. Many a species has
only a niche, but itis its own. (6) Following
from the masterful, detailed colonization of
the heavens and the earth and the waters
under the earth, there is the wealth of con-
summate adaptation—of a creature to its
surroundings, to its food, to its habits; of the
unborn young to the mother and of the
mother to the unborn young; of the sexes to
one another; and of the internal architecture
of the body, whether in the fit adjustment of
the proportions of parts, or in the minute
structure of a bone. Every creature is a
bundle of adaptations. Indeed, as Weis-
mann says of the whale, “ When we take

GREAT STEPS IN EVOLUTION 99

away the adaptations, what have we
left ? ”

It is instructive to look into the matter in
detail, and to notice, for instance, what types
made particular acquisitions. Hag fishes and
lampreys (Cyclostomes) were the first animals
with skulls; fishes were first with jaws; amphi-
bians gained fingers and toes, true lungs, a
voice, and a mobile tongue; reptiles first show
the important antenatal robes (or foetal mem-
branes) called the amnion and the allantois,
and the crocodile was the first creature with
a four-chambered heart; birds and mammals
are the only warm-blooded animals, and they
show a great heightening of brain-develop-
ment; in all mammals except a few primitive
forms there is an extremely important and
usually prolonged intimate connection be-
tween the mother and the unborn young.

Tue Ascent oF Man.—As this final achieve-
ment of Vertebrate evolution will be discussed
by Dr. Arthur Keith in a special volume of
this Library, we need not do more than refer
to a few points of general evolutionary
interest.

The real distinctiveness of man from his _

nearest allies depends on his power of building

up general ideas and of controlling his conduct

in relation to ideals. He has many structural

DZ pear TT

100 EVOLUTION

peculiarities, it is true, but the differentiating
qualities are in language, thought and con-
duct, and in the finer brain associated with
these. |

The “ Descent of Man” is the expansion
of a chapter in the “ Origin of Species.’? In
other words, the evidences of man’s origin
from an ancestral type common to him and
to the higher apes, are the same as those used
to substantiate the general doctrine of descent.
As Owen allowed long ago, there is an “ all-
pervading similitude of structure” between
man and the anthropoid apes; the bodily life
is closely similar; the human body is a rich
collection of vestigial structures; some of the
fossil remains are nearer the anthropoid type;
man’s individual development is in some ways
like a recapitulation of his presumed ancestral
history.

There is a fine ring in the closing words of
“The Descent of Man ”’ :—

‘“*We must, however, acknowledge, as it
seems to me, that man, with all his noble
qualities, with sympathy which feels for the
most debased, with benevolence which extends
not only to other men, but to the humblest
living creature, with his God-like intellect
which has penetrated into the movements
and constitution of the solar system—with all

GREAT STEPS IN EVOLUTION 101

these exalted powers—man still bears in his
bodily frame the indelible stamp of his lowly
ori “4 33

Man’s antiquity is to be measured not in
centuries but in millennia. It is perhaps
150,000 years since he used stone weapons in
Europe against mammoth and rhinoceros,
hyena and lion, and these weapons were not
the work of novices. No fossil remains of
man have been found except in Post-Tertiary
(Diluvial) deposits, but there are several
reasons for believing that his origin was very
much earlier. Thus, for instance, it is cer-
tain that he did not arise from any of the
known anthropoid apes (gorilla, chimpanzee,
orang and gibbon), but from a stock common
to them and to him; therefore it is likely that
the human stock had diverged before the
time when the anthropoid apes are known
to have been established as a distinct family,
namely, in the Miocene.

It is possible that man arose as a mutation,
as an anthropoid genius in short, but the
factors that led to his emergence are all
unknown. We must remember, however,
that the stock of Primates to which he is
zoologically affiliated is marked by great in-
telligence, and that we find illustrated amongst
them some very significant habits—of walking

102 EVOLUTION

half erect, of using sticks and stones, of
building shelters, of living in families, of co-
operating in bands, and of talking a good deal.
The anthropoid apes are not social, but many
monkeys are, and there can be little doubt
that man was from the first . distinctively
social. ‘‘ Man did not make society; society
made man.”

The uncertainties as to man’s pedigree
and antiquity are still great, and it is unde-
niably difficult to discover the factors in
his emergence and ascent. Therefore, while
holding firmly to the general conclusion to
which the facts all point, we do well to treat
the problem with all reverence, especially
when we reflect on the greatness of the result
of this last great step in organic evolution.
For “‘ What a piece of work isa man! How
noble in reason! how infinite in faculty, in
form and moving how express and admirable !
in action how like an angel! in BPEL
how like a god!”

A chapter can merely hint at the great
steps in evolution, and we must leave the
reader to develop the subject. For this is
certain that we cannot appreciate the fact
of evolution, or form a sound judgment in
regard to its factors, unless we think of the
age-long process in some detail and recognize

GREAT STEPS IN EVOLUTION 1038

at once the grandeur and the difficulty of
each of its greater uplifts.

EVOLUTION AS RETROGRESSIVE: DETERI-
ORATION AND Parasitism.—Of “ Degenera-
tion: a chapter in Darwinism,” Sir Ray
Lankester many years ago wrote a whole
volume, compact yet readable: still, even
to-day, the old optimism of political progress
too largely colours the public mind; 50,
despite knowledge and care, all save the most
pessimistic of us tend sometimes to speak,
and it may be even write, as if evolution
necessarily implied progress, and as if the
surviving fittest were also the best, in its
ordinary sense, of better than mere good.
Hence the need of frankly facing some of
those ugly chapters of natural history which
follow the decline of so many forms of life,
even high and beautiful ones, into degenera-
tions well-nigh incredible, into parasitisms
even loathsome. For one thing, even the
most thoroughgoing creationist and Paleyan
of old must have had some qualms in ascribing
the intricacies of parasitism to special creation,
or its pains and enfeeblement, so varied and
so widespread among all the higher animals,
to beneficent design; thus the evolutionary
parasitologist has had it practically all his
own way, yet has also cured us, with his

104 EVOLUTION

gruesome lists of pestiferous creatures and
lurking dangers, of that dream of this as the
best of all possible worlds to which a too
facile evolutionism has been wont to incline.
Species of all manner of groups, he shows
us, may fall into parasitism, the simplest
bacteria and lower fungi, the more active and
long supposed innocent Protozoa above all—
so that for a generation past the vast field
of pathology has seemed well-nigh divided
between bacteriologist and _ parasitologist
proper. It is among the Vertebrates, which
only fall into parasitism in the rarest cases,
that infestation is most frequent. Fishes
may even swarm externally with trematodes
and parasitic crustaceans, internally with
eysts and intestinal worms without number.
A vivid impression of the prevalence of
parasitism is afforded by the capture, not
infrequent at a channel zoological station or
by fisher folk anywhere, of the huge and
majestic sunfish, Orthagoriscus mola; and by
picking off with forceps into museum bottles
his crowds of uninvited passengers—the tuft
of barnacles upon his back, the biting isopods
like enormous fleas upon his skin, the trema-
todes sucking like leeches upon his eyes; and
within to find not only his alimentary canal
crammed with worms more than with food,

GREAT STEPS IN EVOLUTION 105

and his liver changed from its natural brown
almost into the likeness of a tangle of white
worsted, of which each thread is a tape-
worm. Neither frog nor lizard, serpent nor
bird, escapes; indeed birds are peculiar suf-
ferers, witness the too common “ gapes”’ of
poultry, a choking of the windpipe by thread-
worms, and the numerous parasitic worms
which Mr. Shipley’s labours have discovered
in the well-nigh sacred grouse. Of ticks the
shepherd is only beginning to know the full
dangers, as of fleas man himself. Apart
from bacterial and protozoan pests, as yet
beyond counting, man is debited by the
parasitologist with at least sixty species; some
reckon twice as many. The amazingly varied
methods of Nature for the diffusion of para-
sites are among the very strangest disen-
tanglements of the web of life, but into the
stories of these adventures in search of mis-
chief we cannot enter here: enough if we
note the stupendous rate of multiplication
by which the many chances against finding
the proper host are constantly met; thus
the common tape-worm of man has been
calculated to produce eighty-five million ova
during its two years’ existence.

It is an interesting inquiry whether the
large numbers of so-called species of thread-

106 EVOLUTION

worms, tapeworms and other parasites, are
not, in many cases at least, mere modification
forms, whose diagnostic characters are directly
induced by the peculiarities of their respective
hosts. The question is, of course, one for the
experimental observer.

Again, even parasitism must not be viewed
too pessimistically. It is, after all, not the
interest of the parasite to kill its host, or even
to deteriorate its life too seriously; moreover
the host becomes more or less adapted to its
wonted guests, and probably correspondingly
immune to the irritant poisons which many
parasites have been shown to excrete. The
rapid disaster which parasites so often bring
about seems rather when introduced into
some new and unaccustomed host; as probably
in the case of sleeping sickness.

Again, parasitism may pass on one side
towards more and more complete mutual
adaptation, witness the symbiosis of alga
and animal in certain sea-anemones, or
the admirable permanence of that co-opera-
tion of short-lived alga and transient mould
which enables the resultant lichen sometimes
to outlive the very tree which bears it. Galls,
again, afford many instances of a parasitism
which is reaching equilibration.

Thus in many ways we must not consider

GREAT STEPS IN EVOLUTION 107

parasites as simply aberrant, nor their peculi-
arities as unique. ‘These become intelligible
products of evolution when we realize them
as perhaps the extreme cases of the deter-
mination of organism by environment. From
the analysis of this relation, especially in
these extreme cases of parasite and host, the
theory of evolution might almost have been
predicted, since, if the details of environment
and of organism be, as here, obviously and
precisely adapted one to the other, change
in the former must either be followed by the
extinction of the latter, or by its modification
in the requisite details. To understand the
modus operandi of this, Weismann invokes
the needful germinal variation of the germ-
cells, and Dohrn his “ principle of functional
change”—his reminder that every living tissue,
however specialized, retains traces of all the
functions of protoplasm, and that there-
fore any one of these may be indefinitely
increased by favourable conditions, and the
specialized function similarly reduced to a
trace. Our notion of specialization becomes
thus associated with a corresponding possi-
bility of simplification, and our idea of
progress thus becomes complemented and
checked by the possibility of degeneration, and
this from any stage of the ascent of life. The

108 EVOLUTION

first of these views is the neo-Darwinian; while —
the second savours of neo-Lamarckianism;
but here, happily, is a case in which the recent
admirable eirenicon of Lloyd Morgan, Osborn
and Baldwin (discussed in Chapter V1) may
be conveniently applied. According to this,
the modifications of the individual in response
to environment, to use and disuse, in them-
selves non-heritable though they may be, may
yet serve as the nurse and shield and selective
vantage-ground for germ-variations in the
same direction. With this two-fold process
at work, in germs and in developing adults,
the frequent development of parasitic shoots
upon the tree of life becomes a less perplexing
marvel.

Another interest of this subject is the way
in which it invites that comparison of the
natural and the social world which has always
been so fascinating, and, as we maintain
from opening to close of this volume, also so
fruitful. The naturalist and physician almost
forget that the word parasite was originally
a social epithet; but the many critics of human
society are using the comparison more and
more frequently, of course often in mere vague
abuse, but sometimes keenly also. Notable
in this connection is the collaboration of
Professor Massart, a biologist of Brussels, with

GREAT STEPS IN EVOLUTION 109

M. Emile Vandervelde, now widely known
beyond the Belgian parliament as one of the
foremost of the popular tribunes of Europe;
and their “* Parasitism, Organic and Social ”
(1895) will still be found suggestive to
naturalist and sociologist alike.

Without entering upon matters so contro-
versial as a volume so named inevitably raises,
we may profitably note the fresh light which
the study of parasitism throws upon that till
lately accepted and still mainly predominant
body of economical and social thought, that
of the modern industrial age—its political
economy for the group, its teaching and ideal
of success for the individual. For thus instead
of calling this one or that of our more success-
ful fellows by the ugly name of parasite, we
may more safely begin by recognizing this
very tendency in ourselves. For who does
not at times look forward to a more peaceful,
@ more prosperous and assured period, in
which, storms and trials over, we are to settle
down, snug, cosy and warm, there to eat of the
fat, and drink of the sweet, and to enjoy what
may remain to us of life? And what parent
but wishes for his child a safer, easier, richer
life than his own? Little wonder, then, that
the political economist, who has for the most
part but massed popular opinion into his

110 EVOLUTION

pretentious but inchoate would-be science, has
treated this scheme of life as the natural one,
and confirmed his public more and more into
it as the practical one as well. For your
would-be practical man, slave to that wildest,
strangest, most impossible of all theories—
the theory that there are no theories—ever
falls victim to the surface plausibility of the
crudest theory going.

Whereas the student who has seen crusta-
cean larve in all the activity of their youth,
bright-eyed, free-swimming, and thereafter
settling down into barnacles upon the rock,
or, seeking food and safety at the expense
of their larger and stronger active kindred,
settling further down into mere blood-bags,
mere egg-bags, “sams eyes, sans ears, sans
everything,” has before him a nature-symbol,
one worth thinking about, and that carefully,
even furiously also. For here it turns out
that the teaching of the economists who have
identified comfort with progress have been
so far right in unifying them, no doubt; only
they have been forgetting that such progress
tends to be bought too dearly. Their gospel
of “‘ getting on”’ is not necessarily getting on;
and hence their much preached and yet more
prayed for “success in life”’ so often turns
out the very reverse of success in living.

GREAT STEPS IN EVOLUTION 111

Contrariwise, our bio-sociology tends to
justify the so-called “‘unpractical.” It is
essentially the free-living and self-supporting
creatures that really get on, that evolve in the
best sense. So the idealist adventurer, who
loves to meet the “ bright eyes of danger,”
who goes out to seek love and face death, has
true success in life, brief though it be; and this
not merely from the “romantic” point of
view the philistines fancy confined to novels,
but from that rising standpoint of evolutionist
realism of which morals in one age, religion
in another, and now art in our own, have each
been the presage. Thus in facing the ugliest
facts of lowest life we see them give way to
the noblest hopes of our own evolution. In
education, then, let us not fear to apply this
escape from economics of the baser sort, that
science falseliest so called; and thus have done
with the current obsessions of the money-
world, of most ease with least labour, of
getting something for nothing; perhaps above
all, of that seeking after the assured life of
petty, sedentary functionarism, which is be-
coming a main curse of civilization—we now
see why.

Out in the fields, on hill, at sea, facing the
buffetings of wind and wave, working with
‘our fellows, and there content neither with

112 EVOLUTION

strength nor skill alone, but seeking exercise
for both, here is the best life of evolving man-
hood: as of old, so for ever, let townlings dream
as they may. And how to combine this
fundamental vividness of rustic life with the
subtler, yet it may be even more strenuous
life of productive urban culture, is, perhaps,
the main problem before the evolutionist. In
modern everyday phrase this task is, in fact,
already opening before us; already we are
seeking to advance rural development here
and town-planning there; we have next to
co-ordinate both into regional renewal. Given
this incipient view and policy of human life,
as consciously evolutionary, in exchange for
the passing one—of successful life as sessile,
unconsciously degenerative, and as far as
possible, parasitic—the field of effort opens.
Hygiene, engineering and irrigation, agricul-
ture and forestry, and all such strenuous
careers are already opening perspectives lately
undreamed by youth, struggles for existence
nobler and more sustainedly strenuous than
those of war. Practically, the control of the
ice-lands and of the tropics, the amendment
of nature—and above all, speculatively, the
distinction between ascending and deteriora-
tive progress—thus alike become more clear.

i

VARIATION AND HEREDITY 118

CHAPTER IV

VARIATION AND HEREDITY: THE SPRINGS
AND CHANNELS OF EVOLUTION

What Organic Evolution Implies—Heredity and Variation
—Why Like Tends to Beget Like—Organic Changes
Analyzed—Darwin’s Position in regard to Variations
—Modern Study of Variations—The Mutation Theory
—Mendelism—Causes of Variation.

Wuat Orcanic EvotutTion Imp.ies. — Or-

ganic evolution is racial change along a de-

finite line. It is for the variety or species,
breed or race, what embryonic development
is for the individual—a mode of becoming.

Its continuity is sustained by a succession of

generations, whereas in development the con-

tinuity is obviously one of personal identity.

Evolution implies three things: (a) raw

materials in the form of variations, or organic

changes of some sort; (b) an arrangement for
securing the hereditary entail of some of these;
and (c) a directive mechanism for securing
consistency and effectiveness of racial change.

The importance of (c) will vary with what

is provided by (a) and with the degree of

persistence allowed by (0d).

HEREDITY AND VARIATION. — Heredity is
the genetic relation between successive genera-
tions, and an inheritance includes all that an

114 EVOLUTION

organism is, or has, to start with, in virtue of
its hereditary relation. We cannot compare
organic inheritance to a patrimony; for the
organism and its inheritance are, to begin
with, one and the same. Nor do we any
longer think of heredity as a power or a prin-
ciple, as a fate or a force; we study it as a
genetic relation, which is sustained by a visible
material basis, namely the germ-cells; as a
relation of resemblances and differences which
can be measured and weighed, or in some way
computed.

The hereditary relation is suchthat like tends
to beget like, while at the same time oppor-
tunity is afforded for the individual new
departures which we call variations. Both
the tendency to persist and the tendency to
diverge are included in the hereditary relation,
so that it is confusing to make an absolute
antithesis between heredity and variation.
Heredity, seen in its fullest sense, is the larger
concept, and includes both inertia and diver-
gence, both continuance and change. What-
ever be the terms used, there are two comple-
mental facts: that like tends to beget like,
yet that every new creature has in some way
an individuality of its own.

Way Lixe Tenps to Brecet Lixe.—The
fundamental hereditary relation is such that

VARIATION AND HEREDITY 115

like tends to beget like, and the reason for this
is found in the fact of germinal continuity.
As long ago as 1875, Galton pointed out that
there is a sense in which the child is as old as
the parent; for when the parent’s body is
developing from the fertilized ovum, a residue
of unaltered germinal material is kept apart
to form the reproductive cells, one of which
may become the starting-point of a child.
This idea has been independently expressed
and more fully developed by Weismann, who
states it thus: “In development a part of
the germ-plasm [#.e. the essential germinal
material] contained in the parent egg-cell is
not used up in the construction of the body
of the offspring, but is reserved unchanged
for the formation of the germ-cells of the
following generation.”” In many cases the
future reproductive cells are visibly set apart
at a very early stage before the division of
labour in body-making has more than begun;
in other cases where the future reproductive
celis are not visible till much later, we argue
by analogy that they are reproductive cells
because they have not shared in body-making,
but have kept intact the protoplasmic equip-
ment—the full inheritance—of the original
fertilized ovum. Thus the parent is rather
the trustee of the germ-plasm than the pro-

116 EVOLUTION

ducer of the child. In a new sense the child
is “‘ a chip of the old block.” The clarifying
and corroboration of this doctrine of germinal
continuity has been one of the most important
steps of post-Darwinian biology. It enables
us to understand why like tends to beget like;
and it also suggests, what is hardly less impor-
tant, that the new departures or variations,
which we have spoken of as individual, are
really expressions of the changeful vitality of
the undying germ-plasm. As Bergson puts it:
** Life is like a current passing from germ to
germ through the medium of a devcloped
organism. ... The essential thing is the
continuous progress indefinitely pursued,
an invisible progress, on which each visible
organism rides during the short interval of
time given it to live.”

OrGANIC CHANGES ANALYZED.—Great pro-
gress has been made in recent years in studying
the individual peculiarities of plants and
animals, in registering their amount and their
frequency. The collection and analysis of
these ‘“‘ biometric” data is of fundamental
importance, for the Darwinian method of
interpretation is like that of Lyell, throwing
the light of the present on the darkness of the
past; and it is only when we know securely
what changes are going on now that we can

VARIATION AND HEREDITY 117

legitimately argue back to what may have
occurred in remote antiquity. |

Facts bearing upon variations have been
gathered so industriously of late that assimila-
tion has hardly kept pace with accumulation;
and one evidence of this is to be found in the
confusing ambiguity of the terms used by
various biologists. The term “ variation ” is
used in reference to at least three readily
distinguishable kinds of organic change, and
the term mutation is also used in three senses.
The terminology will require to be standard-
ized by some International Congress of
Biologists; but pending this, let us do what
we can in trying to get the ideas clear.

When we compare a number of members of
the same species—men, ruffs, garter-snakes,
sticklebacks, snails, brambles, buttercups,
pansies, and so on—we find that they differ
from one another. These differences can be
measured and registered under the title
** observed differences,’’ which commits us to
no theory whatever.

But these “ observed differences ” require
further analysis before a statement of them
can be very useful. Indeed a statement of
them without analysis is very apt to lead to
biological fallacy. Many of the differences
may be wrapped up with sex, and these can

118 EVOLUTION

be readily sifted out from the slumped total.
Others may be wrapped up with age, and these
can also be analyzed out. Others are due
to something unusual in the “nurture” in
the wide sense; that is, they are the direct
results of peculiarities in surrounding influ-
ences and of peculiarities of habit. Such
changes in the bodies of plants and animals
are extrinsic, not intrinsic, in origin; they are
acquired, not inborn. They are technically
called “ acquired characters,’”’ or much more
clearly “‘ modifications.” They may be de-
fined as structural changes in a part of the
body, directly induced by peculiarities of use
or disuse, or by some change in surroundings
and nurture generally, which transcend the
limit of organic elasticity and thus persist
after the inducing conditions have ceased to
operate. No convincing evidence of their
transmission has as yet been forthcoming.
Now the point is that when we subtract
from the total of observed differences all that
can be regarded as individual modifications,
we have a very interesting remainder, which
we thus define off as inborn or germinal
variations. They are intrinsic, not extrinsic;
inborn, not made. We cannot causally relate
them in a direct way to peculiarities in habits
or surroundings; they are often distinct at

VARIATION AND HEREDITY 119

birth or even hinted at before birth; they are
rarely alike even among forms whose con-
ditions of life are uniform. They are in many
cases, if not always, transmissible. They form
the raw material of evolution.

Darwin’s PosiTIon IN REGARD TO VARIA-
TIONS. — Darwin recognized two kinds of
hereditary variations, in addition to those
extrinsic changes which we now call modifica-
tions. In the first place he recognized large
“single variations ” or “‘ sports,’” which occur
rarely and result in conspicuous divergences
from the type of the species. In the second
place he recognized slight “ individual varia-
tions,” which are practically ubiquitous,
distinguishing child from parent, brother from
brother, cousin from cousin. Both of these
kinds of variations were called “ indefinite ”
and ‘* spontaneous,” to distinguish them from
what he somewhat unfortunately called
*“* definite variations ’’—the direct result of
environmental and functional peculiarities.
These correspond to what we now call modi-
fications, and it must be noted that Darwin
believed in their occasional transmissibility.

Leaving aside the question of the possible
racial importance of modifications, it is of
interest to notice Darwin’s view of the
relative importance of “single variations ”

120 EVOLUTION

and “individual variations.” The former
correspond in a general way to what we
now call “ discontinuous variations,”’ ‘** muta-
tions,” “ saltatory variations ’’; the latter to
“continuous variations’ or “ fluctuations.”
Darwin was much interested in the former
class, “‘ sports ’’ as he sometimes called them;
but—true to the influence of Lyell—he came
deliberately to the conclusion that the minute
ubiquitous fluctuations were by far the more
important. The criticism of Fleeming Jenkin,
Professor of Engineering in Edinburgh, that
single large peculiarities would be likely to
be swamped by inter-crossing, had so much
weight with Darwin that he ceased to attach
importance to the larger divergences, and
found his raw material in the smaller fluctua-
tions. ‘“‘ The more I work,” he said, ‘‘ the more
I feel convinced it is by the accumulation of
such extremely slight variations that new
species arise.” We shall return to this
question, but we may note in passing (1) that
there is no reason to believe that “ single
variations ”’ necessarily occur singly, the fact
being that numerous sports in the same
direction sometimes occur simultaneously;
(2) that some of the discontinuous variations
that have been studied have proved themselves
to have remarkable staying power in inherit-

VARIATION AND HEREDITY 121

ance, being anything but liable to swamping;
and (3) that we have not, even to this day,
sufficient knowledge of what Darwin never
seems to have doubted, namely the degree of
heritability of the minute fluctuations. It
was probably a false step on Darwin’s part
when he turned so fully away from discon-
tinuous variations.

MopERN StupDy oF VARIATIONS.—One of
the great steps of progress in evolution lore
since Darwin’s day has been what we see, for
instance, in Dr. J. A. Allen’s pioneer measure-
ments of American birds (1871), in Bateson’s
** Materials for the Study of Variation ” (1894),
and in the pages of the journal called “ Biome-
trika ’—the recording and registration of the
variations that do actually occur in nature.
A few results may be noted.

It has been clearly shown that Darwin did
not in the least exaggerate the available
supply of raw material. “Even Darwin
himself,’ as Wallace says, “did not realize
how much and how universally wild species
vary.” It has been proved that great varia-
tion is as frequent in wild as in domesticated
animals. The fountain of change is even more
copious than was dreamed of.

Another important fact has come out clearly,
especially from the pioneering work of Galton,

122 EVOLUTION

that there is often a proportion between
the frequency of a particular variation and
the amount of its deviation from the mean
of the character in question. Let us take
Wallace’s illustration, which makes this point
clear at a glance: Among measurements of
2,600 men, taken at random, there is 1 of
4 ft. 8 in. and 1 of 6 ft. 8 in.; 12 of 5 ft. and
about 12 of 6 ft. 4 in.; te. equal numbers at
equal distances from the mean of 5 ft. 8 in.
In other words, when the frequency and the
magnitude of the variations are registered,
they often show what is called the Normal
Curve of Frequency.

This tedious task of registering the varia-
tions that occur may seem far from life-lore,
but a little consideration and a little actual
registration—of buttercup petals, of length of
bird wings, of brittle-star arms, of jelly-fish
canals, or the like—will convince the student
that biometrics may lead him into the very
heart of the matter. If the registration of
the dimensions of a particular character be
carried on year after year in similar material,
and show a consistent increase in the asym-
metry or skewness of the curve, this must
mean that the species is moving in a definite
direction as regards the particular character
measured. Similarly, the persistent occur-

VARIATION AND HEREDITY 128

rence of a well-substantiated double-humped
curve—not the result of modificational
effects—may vividly bring home the fact that
the species is dividing into two sub-species.
Thus, by a statistical path, we are brought
face to face with the most vital of all facts—
Pévolution créatrice.
_ The rapidly growing body of facts in regard
to variation is also confirming what Darwin
-ealled the “correlation of variations.” He
pointed out that the whole organization is so
tied together during its growth and develop-
ment that, when slight variations in any part
occur, and are transmitted, and are accumu-
lated by natural selection, other parts of the
structure may also undergo change, apparently
irrespective of any advantage. The whole
framework is so knit together that if one
member suffer change others suffer with it.
The idea of correlation suggests that the
organism often changes as a unity in many
parts at once, and not like a machine that is
perfected piecemeal by the accumulation of
many little patents independent of each other.
Thus 2 variation important in the present may
bring in its train one that is destined to be
important in the future, and a variation too
small in itself to be of value may be carried
over the dead point into effectiveness because

124 EVOLUTION

it is correlated with another variation of
greater momentum or vital value.

Another result of modern studies on varia-
tion requires to be stated very cautiously.
Evidence is accumulating to show that
organic structure may pass with seeming
abruptness from one position of equilibrium
to another. Changes of considerable amount
sometimes occur at a single leap. These
brusque changes are called “ discontinuous
variations,” or sometimes “sports,” and, in
certain cases, “mutations.” There is nothing
new in the suggestion that evolution may
sometimes have been by leaps and bounds, for
this was a favourite idea of Cuvier’s evolu-
tionist contemporary and antagonist, Etienne
Geoffroy Saint-Hilaire; and it was also a pet
heresy of Huxley’s. There is nothing new in
recognizing that discontinuous variations do
occur, for they correspond to Darwin’s “single
variations’ or “sports.’? What is new is that
we are beginning to accumulate facts in regard
to their frequency and their heritability.

Sir Francis Galton compared organic struc-
ture to a polygonal model, so shaped as to
stand on any one of its sides. “‘ The model
and the organic structure have the cardinal
fact in common, that if either is disturbed
without transgressing the range of its stability,

VARIATION AND HEREDITY 125

it will tend to re-establish itself, but if the
range is overpassed, it will topple over into
a new position; also that both of them are
more likely to topple over towards the posi-
tion of primary stability than away from it.”

THE Mutation THEORY.—In 1900 Professor
Hugo de Vries of Amsterdam published under
the title “‘ The Mutation Theory ” an account
of his very interesting and important experi-
ments and observations on the origin of
species in the vegetable kingdom. The most
striking of his conclusions was that species
arise from one another by discontinuous
leaps and bounds, as opposed to a continuous
process. Whereas Darwin relied on the action
of selection on minute individual variations
or fluctuations, de Vries believes that these
have nothing to do with the origin of species,
which appear “all at once”? by mutations.
Let us quote some of his characteristic state-
ments.

“By the mutation theory I mean the
proposition that the attributes of organisms
consist of distinct, separate and independent
units. These units can be associated in groups,
and we find, in allied species, the same units
and groups of units. Transitions, such as
we so frequently meet with in the external
form both of animals and plants, are as

126 EVOLUTION

completely absent between these units as they
are between the molecules of the chemist.”
“The adoption of this principle influences
our attitude towards the theory of descent
by suggesting to us that species have arisen
from one another by a discontinuous, as
opposed to a continuous, process. Hach new
unit, forming a fresh step in this process,
sharply and completely separates the new
form as an independent species from that from
which it sprang. The new species appears all
at once; it originates from the parent species
without any visible preparation, and without
any obvious series of transitional forms.”
“The mutation theory is opposed to that
conception of the theory of selection which is
now prevalent. According to the latter view
the material for the origin of new species is
afforded by ordinary or so-called individual
variation. According to the mutation theory
individual variation has nothing to do with
the origin of species. This form of variation
. » « cannot even by the most rigid and sus-
tained selection lead to a genuine overstep-
ping of the limits of the species and still less
to the origin of new and constant characters.”
*“* Of course every peculiarity of an organism
arises from a previously existing one; not,
however, by ordinary variation, but by a

~ VARIATION AND HEREDITY 127

sudden though minute change. It is perhaps
appropriate to compare such a change with
a chemical substitution.”

“The name I propose to give to this
* species-forming * variability is Mutability
—a term in general use before Darwin’s time.
The changes brought about by it, the Muta-
tions, are phenomena as to the exact nature
of which we understand very little so far.
The best known examples of such mutations
are the so-called spontaneous variations (the
‘ single variations’ of Darwin) by which new
and distinct varieties arise. They are also
termed, fitly enough, sports. In spite of the
fact that they occur fairly often, they are
usually not noticed until the new form has
already appeared, when of course it is too late
to study the phenomenon of its origin ex-
perimentally. These new forms can be sought
for in cultivated species, which are seldom of
pure origin; as well asin Nature. But as yet
we have no power of inducing them at will.
It is my belief that all the simple characters
of animals and plants arise in this way.”

‘“* Under the general term variation, then,
are included two distinct phenomena: muta-
bility, and fluctuation or ordinary variation.”

“The methods of artificial selection cor-
respond to these two types of variability.

128 EVOLUTION

Ordinary variation, which is also known as
individual, fluctuating or gradual variation,
is always present; and it can be described in
terms of perfectly definite laws which have
now been fairly completely formulated. It
provides the breeder with material for his
improved races. On the other hand, he has
to deal with mutations which do not need
repeated selection, but, at the most, must be
kept free from admixture, and which almost
always breed true from the first.”

In support of his theory, Professor de
Vries has relied mainly on the sudden and
repeated leaps and remarkable subsequent
constancy exhibited by the progeny of a
stock of evening primrose, (Enothera lamarck-
iana, which he found growing in a _ wild
state near Hilversum in Holland. But many
other instances of mutation are adduced, the
oldest and most accurately described being
the origin of the cut-leaved variety of the
greater celandine, Chelidonium majus lacinia-
tum, which occurred suddenly in 1590 in the
garden of an apothecary at Heidelberg, and
has been constant ever since. The evidence’
of mutations in the animal kingdom is only
beginning to be gathered, and there are few
satisfactory cases known outside of experi-
mental stations. There are, however, many

VARIATION AND HEREDITY 129

species, é. g. of birds, which differ from their
relatives in features similar to those which
arise as mutations in experimental breeeding.

The issue at present seems to be this. The
distinctive characteristics of a species may
arise in one of two ways, either (1) by the
accumulation of fluctuations, or (2) suddenly
by mutation. In support of the first theory
there are the numerous cases where species
are connected by inter-grades. In support
of the second theory there is experimental
evidence, showing that many characteristics
remain integral and refuse to blend. Patient
work will be necessary before we can decide
as to the relative importance of fluctuations
and mutations.

MENDELISM.—One of the most important
of recent biological discoveries has been the
“law of heredity,” stated in 1865 by Gregor
Johann Mendel (1822-1884), an Austro-
Silesian abbot, who experimented for many
years on crossing different varieties of garden
peas. His great paper, communicated to the
Natural History Society of Briinn, remained
practically unknown till 1900, when De Vries
in Holland, Correns in Germany, and Tscher-
mak in Austria independently, and almost
simultaneously, reached experimental results
closely resembling Mendel’s. This led to a

E

130 EVOLUTION

rediscovery of the buried paper and to a period
of very active experiment, in connection with
which Bateson, Castle, Cuénot and _ their
collaborateurs have been especially prominent.

Mendel worked chiefly with the edible pea,
Pisum sativum, which has many well-marked
varieties and is habitually self-fertilized.
When he crossed a giant variety of 6 to
7 feet with a dwarf variety, ? to 14 feet
high, the offspring were all tall. The charac-
ter of tallness which appeared in the hybrid
generation (F,,), to the exclusion of dwarfness,
was called by Mendel the “dominant”
character, the other being ‘“‘ recessive.”

The tall cross-bred peas were left to self-
fertilize, which corresponds to close inbreeding
in animals, and in their progeny there were talls
and dwarfs in the average proportions of 8: 1.

When the dwarfs of this F, generation were
allowed to self-fertilize, their offspring (F,)
were all dwarfs, and further generations bred
from them were also all dwarfs. They may
be called pure recessives, being “ pure” as
regards dwarfness.

But when the talls of the F, generation were
left to self-fertilize, their offspring (F',) were of
two kinds : one-third of them (pure dominants)
produced talls only; two-thirds of them (impure
dominants) produced talls and dwarfs in the

VARIATION AND HEREDITY 181

8:1 proportion. Thus the F, generation, re-
sulting from the self-fertilization of the cross-
bred forms or hybrids (F,), consisted of 25 per
cent. pure dominants, 50 per cent. impure
dominants, and 25 per cent. pure recessives.

The results may be expressed in a scheme :—

Parental generation Tall variety Dwarf 7
First filial (hybrid) all the o tall ; self-
generation (F}) fi they yielded
a te :
Second filial OO toure 25 % Talls 50 % Tallis 25 % Dwarfs
generation (F

ure dorminants) (impure a cuetaes (pure recessives)

|
(pure) (impure) (pure)

Or, using D for the forms with the dominant
character, R for the forms with the recessive
character, and D(R) for forms with the
dominant character expressed and the reces-
sive character latent, the facts may be
expressed in a more generalized way thus
(after Punnett) :—

Parents D R

First flial generation (¥)) ie )

Second Alial generation (Fs) ae “4 2 + gs
ure ure
: inants) deateante recegsives)

Third filial generation (F's) ach 1D + 2D(R) +18

Let us take as an illustration from among

animals, one lately well illustrated in the
E2

182 EVOLUTION

admirable Evolutionary Exhibition of the
British (Natural History) Museum. When the
peculiar “ waltzing mice” are crossed with
normal mice, the offspring (F,) are all normal.
The waltzing habit is recessive. But when
the offspring are inbred, their progeny (F,)
are normal mice and waltzing mice in the
proportion of 8:1. The recessive waltzers
of this generation might be sold as pure
waltzers; with others of their kind they will
produce only waltzers for as many generations
as one likes to breed them. But the normals
of the same generation turn out to be of two
kinds—though they are all alike in appear-
ance: one-third of them (pure dominants) will
yield only normal mice; the other two-thirds
(impure dominants) will split up again, when
inbred, into normal mice and waltzing mice
in the old proportions of 8:1. Another form
of the scheme may be used :—

P DxR
WS
F, DR)
F, 1D : 2D(R) : 1R
My
F, D 1D : 2D(R):1R R
PA | dy oa
i gS Me
F, D DID : 2DRy: ik” KR R

VARIATION AND HEREDITY 138

It is interesting now to inquire into the
occurrence of this remarkable mode of inherit-
ance, which is seen when the parent forms
have opposite or contrasted characters which
do not blend. The striking fact is the diver-
sity of the organisms in which it has been
demonstrated in the short period since 1900,
e.g. in mice, rats, rabbits, guinea-pigs, cattle,
poultry, canaries, snails, silk-moths; in beans,
maize, wheat, barley, stocks. Another strik-
ing fact is the great variety of characters
to which it applies, e.g. shades of colour,
peculiarities of fur and feathers, abnormal
features like extra toes, subtle qualities like
‘“* broodiness”” in hens, early ripening or
immunity to rust in wheat, and so on.

Let us give a few examples, arranged in
parallel columns,

ANIMALS
Dominant character. Recessive character.

Hornlessness in cattle. Presence of horns.
Normal short hair in Long “Angora”

rabbits and guinea- hair.
pigs.
Short tail in Manx cat Normal length of
(somewhat imper- tail.
fectly).

Normal movements in Waltzing in mice.
mice,

134 EVOLUTION

Crest in poultry. Absence of crest.
Rose comb and Pea Single comb.
comb.

Extra toes. Normal four toes.
Broodiness. Absence of this
instinct.

Unbanded shell in Banded shell.
wood-snail.

PLANTS
Dominant character. Recesstve character.
Peas :—
Tall stems. Dwarf stems.

Yellow cotyledons. Green cotyledons.
Brown-skinned seeds. White seeds.

Round seeds. Wrinkled seeds.
Wheat :—
Absence of awn. Presence of awn.
Rough and red chaff. Smooth and white
chaff.
Keeled glumes. Rounded glumes.
Flinty endosperm. Fioury endosperm.
Susceptibility to Immunity to rust.
rust.
Barley :—
Two-rowed ears. Six-rowed ears.
Nettles :—
Markedly dentate Slightly dentate
leaves. leaves.

So far we have stated facts—the results of
experiment—but Mendel also suggested an

VARIATION AND HEREDITY 185

interpretation or rationale of the facts. He
made the supposition that the generative
cells or gametes produced by the cross-breds
(F,) are of two kinds, each kind bearing only
one of the two contrasted or alternative
characters, which, as we have seen, do not
blend. He supposed also that the two kinds
are produced in approximately equal numbers.
Now if each of the hybrids of the F’, generation
produces in both sexes 50 per cent. of its germ-
cells bearing the dominant character and 50
per cent. bearing the recessive character, then,
if fertilization be fortuitous, 25 per cent. of the
fertilized egg-cells will bear only the dominant
character, 50 per cent. will bear both the
dominant and the recessive character (only
the former being expressed or well expressed
in development), and 25 per cent. will bear
only the recessive character. This is called
the theory of the segregation of pure gametes,
and it is the corner-stone of Mendelism. A
scheme will make it clearer :—

Male Cells, Female Cells.

(>) ay (>): : - (00) 1 pure dominant
@) —> @) = - (@R) 1 pure recessive

|: impure dominants

186 EVOLUTION

Mendel’s simple theory explains the definite
proportions 1D + 2D(R) + 1R, observed when
D and R are crossed. It has been tested in
various ways, for instance, by crossing D(R)
with D or with R, when, as the hypothesis
demands, equal numbers of D(R) and D, or of
(DR) and R, are obtained.

In his exceedingly clear exposition of
Mendelism (1905), Professor R. C. Punnett,
himself a productive investigator, states the
characteristic Mendelian result thus:
““ Wherever there occurs a pair of differen-
tiating characters, of which one is dominant
to the other, three possibilities exist: there
are recessives which always breed true to
the recessive character; there are dominants
which breed true to the dominant character
and are therefore pure; and thirdly, there are
dominants which may be called impure, and
which on self-fertilization (or inbreeding,
where the sexes are separate) give both
dominant and recessive forms in the fixed
proportion of three of the former to one of
the latter.”

Bringing the theoretical interpretation into
prominence—that is, the theory of gametic
segregation, Professor Bateson, the leader of
the Mendelian school in Britain, says: “ The
essential part of the discovery is the evidence

VARIATION AND HEREDITY 187

that the germ-cells or gametes produced by
cross-bred organisms may in respect of given
characters be of the pure parental types, and
consequently incapable of transmitting the
opposite character; that when such pure
similar gametes are united in fertilization, the
individuals so formed and their posterity are
free from all taint of the cross; that there may
be, in short, perfect or almost perfect discon-
tinuity between these germs in respect of one
of each pair of opposite characters.” This
idea of the segregation of the dominant and
the recessive characters in two different sets
of germ-cells is the essence of Mendelian
theory.

Before passing from this important and
fascinating subject, we may emphasize two
points. There is no dubiety in regard to the
clear cases of Mendelian inheritance. Cases
that seem to be non-Mendelian may turn out
to be Mendelian—disguised by the complexity
of the contrast, by interaction between differ-
ent pairs of characters, and by what is called
incomplete dominance—but there is no mis-
taking the phenomena of Mendelian inherit-
ance in their typical expression. The cer-
tainty of the matter is evident from the
success with which the principle has already
been used in prediction and in practice. On

138 EVOLUTION

the other hand, there are also many heritable
characters which blend, and do not conform
to the Mendelian mode of inheritance. In
illustration we may refer to hybrid trout,
half-bred sheep, and mulattoes.

APPLICATION TO EvoLuTION THEORY.—
Like Weismannism, which has for one of its
foundations the idea of germinal continuity,
Mendelism conceives of the hereditary relation
in the strict sense, 7.e. not as between the
bodies of parent and offspring, but between
the parental and the filial germ-cells.

Like Weismannism, which has for another
of its foundations the idea of determinants
or representative particles constituting the
mosaic of inheritance, Mendelism regards the
organism as built up of a number of definite,
separably heritable characters.

Mendelism has thrown light on at least
eertain kinds of variation, those which are
due to the addition or omission of one or more
definite elements. As Bateson puts it:
“* With the development of the inquiry it has
become clear that variation, in so far as it
consists in the omission of elementary factors,
is the consequence of a process of ‘ unpacking.’
The white sweet pea was created in the
variation by which one of the colour-factors
was dropped out. Such variation is not, as

VARIATION AND HEREDITY 189

it was formerly supposed that all variation
must be, a progress from a lower degree of
complexity to a higher, but the converse.
When from a single wild type man succeeds
in producing a multitude of new varieties,
we may speak of the result as a progress in
differentiation : but we must recognize that
the term is only applicable loosely, and that
the obvious appearance of increased com-
plexity may in reality be the outcome of a
process of simplification.”* Similarly, “‘ rever-
sion occurs when the sum total of the factors
returns to that which it has been in some
original type.” The return may be brought
about by the omission of an element or
by the addition of a missing element. If
certain kinds of variation may be called
‘“‘ unpacking,” reversion is re-packing.

In discussing the bearing of Mendelism on
the theory of evolution, Bateson makes three
important suggestions. (1) “One has only
to glance over trays of birds’ skins, the port-
folios of a herbarium, or drawers of butterflies
and moths, to discover abundant ‘ species’
which are analytical varieties of others,’ 4. e.
differing in the presence or absence of definite
factors. “The principles of heredity we
trace in our experimental breeding are operat-
ing throughout the natural world of species.”

140 EVOLUTION

(2) The fact of discontinuity in variation,
whether it be called mutation or something
else, is undoubted, but hitherto there has been
“nothing to indicate how or when it was
determined. We now see that the discon-
tinuous variations are in the main the outward
manifestations of the presence or absence of
corresponding Mendelian factors, and we
recognize that the unity of these factors
is a consequence of the mode in which they
are treated by the cell-divisions of gameto-
genesis.” (8) “* The notion that a character
once appearing in an individual is in danger
of obliteration by the inter-crossing of that
individual with others lacking that character
proves to be unreal; because in so far as the
character depends on factors which segregate,
no obliteration takes place. The factors are
permanent by virtue of their own properties,
and their permanence is not affected by
crossing. ... Moreover, he continues, “‘ The
conception of Evolution as proceeding through
the gradual transformation of masses of
individuals by the accumulation of impalpable
changes is one that the study of genetics shows
immediately to be false. Once for all, that
burden so gratuitously undertaken in ignor-
ance of genetic physiology by the evolutionists
of the last century must be cast into oblivion.

VARIATION AND HEREDITY 141

For the facts of heredity and variation unite
to prove that genetic variation is a phenome-
non of individuals. Each new character is
formed in some germ-cell of some particular
individual, at some point of time.”

The issue at present seems to be this, that
there are characters which blend when crossed,
and others which segregate when crossed.
Patient work is necessary in order to test
these two groups and to discover what is
the criterion of blending and alternating
respectively. In his interesting work on
‘“‘ Hereditary Characters,” Dr. Charles E.
Walker maintains the thesis that racial
characters tend to blend and that individual
characters are transmitted in an alternative
or Mendelian manner.

ORIGIN OF VARIATIONS.—Since variations
form the raw materials of evolution, it would
be satisfactory if we could conclude this
chapter by stating how they arise. But that
is quite impossible at present. We know
very little that is certain in regard to the
originative factors in evolution. We must
still confess, with Darwin: “ Our ignorance
of the laws of variation is profound.” It
may be of interest, however, to notice some
of the suggestions that have been made in
regard to this fascinating problem.

142 EVOLUTION

There are variations which mean aug-
mentation, or diminution, or re-arrangement
of already existing qualities. Now, if the
hereditary qualities are carried by represent-
ative particles in the germ-cells, we can in
a measure understand the origin of the kind
of variation referred to; for extraordinarily
intricate permutations and combinations go
on in the microcosm of the _ germ-cells.
Particularly in the process of maturation is
there what we might call a shuffling of the
cards—even a throwing away of half of the
pack. In fertilization, again, paternal and
maternal contributions form a new unity.
Perhaps there may be, as Weismann supposes,
a struggle between rival hereditary items.

But there seems to be another kind of
variation, qualitative rather than quantita-
tive, substantive rather than architectural,
when something distinctively new appears.
What can be said as to their origin? Weis-
mann has suggested that the oscillations and
changes in the blood and other nutritive
fluids may stimulate the germ-plasm to a new
departure. It may also be that important
changes in the environment may saturate
through the body and provoke the germ-
plasm to vary. There are other “‘ may be’s.”

With all recognition and appreciation of

SELECTION 143

the work and thought above summarized,
we cannot but think that the secret of varia-
bility lies yet deeper, in the very nature of
the living organism itself. It has been a
Proteus from the first; changefulness is its
most abiding quality; in short, the essence
of the creature is its innate creativeness.

CHAPTER V

SELECTION

Huxley on “ The Quintessence of Darwinism ”—Analytic
Abstract of ‘* The Origin of Species” (Variation under
Domestication—Artificial Selection—Variation under
Natural Conditions—Struggle for Existence—Natural
Selection),

The Case for Natural Selection—Direct Evidence of
Natural Selection—Implications of the Concept of
Natural Selection—Different Kinds of Selection (Sexual
Selection—Germinal Selection)—Family and Group
Selection—Anuxiliary Hypothesis of Isolation—Eugenics
as a Renewal of Evolution.

Darwin’s achievement in ‘“‘ The Origin of

Species” was twofold. In the first place,
“he presented the evidences of the fact of
evolution so forcibly and so fairly that he
made evolutionists of the great majority of
_his readers. Indeed, he made the world

_“ think in terms of evolution.” In the second

place, in ‘his theory of Nature’s sifting of

144 EVOLUTION

hereditary variations he gave a causal inter--
pretation of the age-long process of Becoming.
He made the evolution idea current intellec-
tual coin; but his success in making the fact
clear and credible was in part due to his
discovery of one of the chief factors.

Huxitey on “THE QUINTESSENCE OF
DaRwinisM.’’—Huxley made this distinction
between fact and factors very plain in his
essay “‘On the Reception of the Origin of
Species”? in Darwin’s “ Life and Letters.”
He first states the grounds of his own agnostic
position (up to 1858) with respect to the
doctrine of evolution as promulgated by
Lamarck, Robert Chambers, and even
Spencer: “ Firstly, that up to that time the
evidence in favour of transmutation was
wholly insufficient; and, secondly, no sugges-
tion respecting the causes of the transmuta-
tion assumed, which had been made, was in
any way adequate to explain the phenomena.”

He goes on to say :—

“The suggestion that new species may
result from the selective action of external
conditions upon the variations from their
specific type which individuals present—and
which we call ‘‘ spontaneous” because we
are ignorant of their causation—is as wholly
unknown to the historian of scientific ideas

SELECTION 145

as it was to biological specialists before 1858.
But that suggestion is the central idea of the
‘Origin of Species,’ and contains the quint-
essence of Darwinism. ... That which we
were looking for, and could not find, was an
hypothesis respecting the origin of known
organic forms which assumed the operation
of no causes but such as could be proved
to be actually at work. We wanted, not to
pin our faith to that or any other speculation,
but to get hold of clear and definite concep-
tions which could be brought face to face with
facts and have their validity tested. The
‘Origin’ provided us with the working
hypothesis we sought... .”

Of “the quintessence of Darwinism,’’ then,
a brief account is needed, and this may be
best given by following as closely as possible
upon the lines of the magnum opus itself,
although the full title of this—‘“‘ The Origin
of Species by means of Natural Selection, or the
Preservation of Favoured Races in the Struggle
for Life,” is its own best and briefest summary.

ANALYsIs OF “ THE ORIGIN OF SPECIES.” —
After mentioning that his first light upon the
origin of species was derived from his early
distributional studies, Darwin points out that
“a naturalist, reflecting on the mutual affini-
ties of organic beings, on their embryological

246 EVOLUTION

relations, their geographical distribution, geo-
logical succession, and such other facts, might
come to the conclusion that species had
not been independently created, but had
descended like varieties from other species.
Nevertheless, such a conclusion, even if well
founded, would be unsatisfactory unless it
could be shown how the innumerable species
inhabiting this world have been modified so
as to acquire that perfection of structure
and co-adaptation which justly excites our
admiration.”” Again, “‘ It is therefore of the
highest importance to gain a clear insight
into the means of modification and co-
adaptation. At the commencement of my
observations it seemed to me probable that
a careful study of domesticated animals and
cultivated plants would offer the best chance
of making out this obscure problem. Nor
have I been disappointed: in this and in
all other perplexing cases I have invariably
found that our knowledge, imperfect though
it be, of variation under domestication affords
the best and safest clue.” It was therefore
with variation under domestication that he
began his book.

VARIATION UNDER DOMESTICATION. —A
comparison between the individuals of a cul-
tivated or domesticated “ variety ” shows a

SELECTION 147

greater degree of variation than there obtains
between the individuals of a wild species or
“variety.” The higher variability of domes-
tic productions is to be ascribed to the less
uniform conditions of their upbringing, per-
haps in part to excess of food. Exposure to
new conditions must be continued for genera-
tions to set up any great variation; but this,
once set up, continues indefinitely. Changed
conditions may directly influence the whole
organization of the creature or certain parts
alone; or they may act indirectly through
the reproductive system. With respect to the
direct action, the nature of the organization
seems to count for more than that of the
conditions. The effect on the offspring may
be definite: e.g. size may depend upon the
amount of food, colour upon quality of food,
thickness of skin and hair upon climate, etc.
But indefinite variability is a much com-
moner result of changed conditions, and has
probably played a more important part in
the formation of our domestic races. The
reproductive system is peculiarly sensitive
to very slight external changes. Many plants
and animals will not reproduce in domesti-
cation, even though individually vigorous;
others, though weak and sickly, breed freely.
Hence we need not be surprised at the

148 EVOLUTION

reproductive system acting irregularly and
producing variations. But that variation is
not exclusively associated with sexual repro-
duction is demonstrated by the case of plants
*“ sporting” through bud-variation. Such
eases, moreover, prove that the nature of the
organism counts for more than the conditions.

Changed habits, e.g. changes in the degree
of use or disuse of a part, produce an inherited
effect, witness the lighter wing-bones and
heavier leg-bones of the domestic duck, or
the enlarged udders of cows.

Variations are often definitely correlated :
thus short-beaked pigeons have small feet;
hairless dogs have imperfect teeth; and blue-
eyed white tom-cats are deaf. Hence selec-
tion of any one character will probably modify
others indirectly.

Although the laws of inheritance are mostly
unknown, it seems that probably most, if not
all, characters tend to be inherited. There
is no satisfactory evidence to support the
popular idea that domestic varieties revert
to the primitive stock when they run wild.
Reversions occasionally occur in domestica-
tion, but there is no general tendency to lose
what has been gained—apart, of course, from
breeding with wild stocks, or with other
domesticated ones.

SELECTION 149

Except in being less uniform than natural
species, in often differing more widely in a
single part, and in being fertile when crossed,
there are no well-marked distinctions between
our domestic races and the so-called true
species of a genus. The many breeds of
dogs and cattle may have arisen from more
than one species; but probably those of horses
and fowls, and clearly those of rabbits, ducks
and pigeons, are each descended from a
single wild species. At least a score of varie-
ties of pigeon might be chosen which differ
so thoroughly, internally as well as externally,
that an ornithologist, treating them as wild
birds, would be compelled to grant them
specific, and even distinct generic rank. Yet,
since all these have indisputably arisen from
the wild rock-dove, it is clear that naturalists
who admit a unity to such domestic races,
which professed breeders have often laughed
to scorn, should in turn be cautious before
deriding the unity of wild ones.

ARTIFICIAL SELECTION.—How, then, have
domestic races been produced? By external
conditions or habits alone? One of their
tell-tale features is in exhibiting adaptations,
not to their own good, but to man’s use or
fancy. We know that all the breeds were
not produced in their present state of per-

150 EVOLUTION

fection, and the key is man’s accumulative
selection. Nature gives successive variations;
man adds them up, making for himself useful
breeds. Skilful breeders speak of the organiza-
tion as plastic and under control, and have
effected great changes within our own genera-
tion. Unconscious selection, which results
from every one trying to possess and breed
the best individuals, is even more important.
The accumulation of change which man
effects explains why we so often cannot
recognize the wild parent stocks of our culti-
vated plants, while its absence in countries
inhabited by uncivilized man explains why
these never yield plants worth immediate
culture. Man’s power of selection is facili-
tated by keeping large numbers, in which
variations are more likely to occur. Facility
in preventing crosses is also of importance,
¢.g. in the case of pigeons as contrasted with
cats; some species are, however, less variable
than others, e.g. the goose.

VARIATION UNDER NATURAL CONDITIONS.—
Individual differences arise even in the off-
spring of the same parents and tend to be
inherited; hence they afford material for
natural selection to act on and accumulate,
precisely as they would for human selection.
(It may be that genera with large numbers of

SELECTION 151

slightly different species—e. g. rose, bramble
and hawkweed—owe their protean character
to their variations being of no service or
disservice, and consequently not being acted
on by natural selection.) In determining
whether groups of similar forms should be
ranked as species or as varieties, the opinion
of naturalists of sound judgment and wide
experience is the only guide, yet this lacks
unanimity : for example, of the polymorphic
genera (7.¢. rich in species with a small range
of differences) in the British flora alone, Ben-
tham reckons 112 species, but Babington 251.
Wallace has shown that no certain criterion
can be given by which to define his own con-
venient working categories of Malayan butter-
flies and moths, viz. variable forms, local
forms, sub-species, and representative species.
As De Candolle concluded from his mono-
graph on oaks (in which he shows at least
two-thirds of his 300 species to be provisional),
** so long as a genus is imperfectly known and
its species founded upon a few specimens ”
they seem clearly limited; but, “ just as we
come to know them better, intermediate
forms flow in and doubts as to specific limits
augment.” The terms variety and species
are thus arbitrarily applied to indefinable
groups of more or less closely similar in-

152 EVOLUTION

dividuals. Common species that range wide
and are much diffused are those which vary
most. The species of the larger genera in
each country vary more frequently than the
species of the smaller genera. The species
of large genera present strong analogies with
varieties, which suggests that they originated
as such.

STRUGGLE FOR EXISTENCE. — The term
*‘ struggle for existence” is used in a large
and metaphorical sense, including dependence
of one being upon another, and embracing
(which is more important) not only the life
of the individual, but success in leaving
progeny. From the high (geometric: 1) rate
of increase of all organic beings (even the
slow breeders requiring only a few more years
to people a whole district) struggle inevitably
follows, either one individual with another of
the same species, or with the individuals of
a distinct species, or with the physical con-
ditions of life. It is the doctrine of Malthus
applied with manifold force to the entire
animal and vegetable kingdoms, for in this
case there can be no artificial increase of food
and no prudential restraints from marriage.

The checks to increase are very obscure.
Eggs or young animals generally suffer most,
and plants, mostly as seedlings, both from

SELECTION 153

germinating on ground already occupied and
from animals. The amount of food, of course,
gives the extreme limit of numbers; very
frequently, however, the check is given by
the attacks of enemies, as on game = by
“vermin.” Changes of climate play an im-
portant part, and periodical seasons of extreme
cold have destroyed as many as four-fifths of
the birds of an observed area. Epidemics,
too, may occur. In many a species a large
stock of individuals is often essential to its
continuance.

Complex and unexpected checks and re-
lations exist between organic beings which
have to struggle together; witness the pro-
found alteration of the flora and fauna of a
heath when planted with Scots pine, these
again being wholly dependent upon the ex-
clusion of cattle. But in several parts of
the world insects determine the existence of
cattle. Again, red clover depends for fertil-
ization upon the humble-bees, these upon
immunity from the attacks of field-mice, and
thus indirectly upon the number of cats.
Hence no bees, no clover, and the more cats,
the more clover.

The struggle will almost invariably be most
severe between the individuals of the same
species, for they frequent the same districts,

154 EVOLUTION

require the same food, and are exposed to
the same dangers. In the case of varieties of
the same species, the struggle will generally
be almost equally severe, and we sometimes
see the contest soon decided (as in the case of
varieties of wheat or of sweet pea, of the
mountain sheep or of the medicinal leech).

Similarly, the struggle between species of the
same genus will € more _severe_
than _b i isti

This is illustrated by the inevitable replace-
ment of the black rat by the brown, or
of the large cockroach by the small. The
structure of every organism is related to that
of all others with which it competes, from
which it escapes, or on which it preys; wit-
ness alike the teeth and talons of the tiger, or
the legs and claws of the parasite clinging to
his hair. The albumen of a seedling favours
its struggle with plants already growing around
it. Darwin goes on to speak of two “canine
animals” struggling with each other in a
time of dearth; of mistletoe versus mistletoe
on the same branch; of mistletoe versus other
fruit-bearing plants; of a plant on the edge
of the desert in days of drought; and then
says, “ In these several senses, which pass into
each other, I use, for convenience’ sake, the
general term of Struggle for Existence.”

SELECTION 155

NatTuraL SELEcTION.—How will this
struggle for existence act in regard to varia-
tion ? Can the principle of selection, so potent
in the hands of man, apply under Nature?
Most efficiently; for, when we bear in mind
the constant occurrence of variation, with
the strength of the hereditary tendency, also
how infinitely close and complex are the
mutual relations of organic beings to each
other and to their physical conditions of life,
and consequently what infinitely varied diver-
sities of structure might be of use to each
being under changing conditions of life, can it
be thought improbable, seeing that variations
useful to man have undoubtedly occurred,
‘that other variations, useful in some way to
each being in the great and complex battle
of life, should occur in the course of many
generations ? And if such do occur, can we
doubt (remembering that many more in-
dividuals are born than can possibly survive)
that individuals having any advantage, how-
ever slight, over their fellows would have the
best chance of surviving and of procreating
their kind ? On the other hand, we may feel
sure that any variation in the least degree
injurious would be inevitably destroyed.

This preservation of favourable and this
destruction of injurious variations are called

156 . EVOLUTION

natural selection, or, less metaphorically, the
survival of the fittest, the one term referring
mainly to the process, the other to the result.
The probable course of natural selection may
be understood from the case of a country
undergoing change of climate. The pro-
portional numerical strengths of its species
will be changed; some will probably become
extinct; and these changes will seriously
affect the others. Immigration of new forms
might also occur, with further serious dis-
turbance; or, where this is impossible, there
will be places in the economy of Nature which
might be better filled up. In such_ cases
slight changes in structure or habit which
in any way favoured the individuals of any
species, by adapting them better to their
altered conditions, would tend to be preserved,
and natural selection would have free scope
for its work of improvement. Moreover,
changed conditions increase variability.

As man produces great results by his
artificial selection, what may not natural
selection effect ? Man selects only for his
own purposes, Nature for the good of the
creature itself; man on the more external
characters (he has become more adventurous
since Darwin’s day), Nature on the whole
machinery of life; man irregularly and im-

SELECTION 157

perfectly for a short time, Nature by con-
sistent accumulation during whole geological
periods. Natural selection is daily and hourly
scrutinizing, throughout the world, the slight-
est variations, rejecting those that are bad,
preserving and adding up all that are good,
silently and insensibly working, whenever and
wherever opportunity offers, at the improve-
ment of each organic being in relation to
its animate and inanimate conditions of life.
It may operate on characters which we are
apt to consider of very trifling importance,
and its accumulation of small variations may
set up unexpected correlative changes. It
may affect the egg, the seed, or the young as
easily as the adult; it may adapt the structure
of young to parent and of parent to young;
and in social animals it may adapt the struc-
ture of each for the benefit of all. In the later
editions of the “ Origin” a brief account of
sexual selection is given at this point.

The theory of natural selection is then illus-
trated by particular instances. Thus Darwin
pictures the formation of swift varieties of
wolves, much in the same way as greyhounds
have been evolved by man. Or, again, he
refers to the secretion of nectar by flowers,
its use to insects, the action of these in carry-
ing the fertilizing pollen, its advantage in

158 EVOLUTION

intercrossing, and the resultant finely adjusted
adaptation of flower and insect to each other
through the preservation of their respective
advantageous variations.

Circumstances favourable for the production
of new forms through natural selection are
great variability, large numbers of individuals,
the complex effects of intercrossing, isolation
in confined areas (yet probably still more an
extension over continental areas, especially if
oscillating in level), and considerable lapse of
time. But the lapse of time by itself must
not be supposed to do anything (as if the
forms of life were undergoing change by some
innate law), but merely to afford increased
opportunity for variation and environmental
change. Extinction, to which rare species
are on the way, is the last word of natural
selection.

The divergence of character brought about
by artificial selection in domestic breeds is
efficiently paralleled in Nature, since the
more diversified the offspring of each species,
the more they will seize on diverse places in
the economy of Nature, and so increase in
numbers. The greatest amount of life can
be supported by increased diversification of
structure, each species being adapted to a
particular set of conditions. This divergence

SELECTION 159

of character, with extinction of intermediate
forms, explains the difficulties of classification
—of making a genealogical tree which will
express the facts of the case and represent
diagrammatically “the great tree of life,
which fills with its dead and broken branches
the crust of the earth and covers the sur-
face with its ever-branching and beautiful
ramifications.”

Darwin’s SuMMARY.—The preceding sum-
mary of the classical statement of the doctrine
of natural selection should be supplemented
by reference not only to the original work, to
the corroborative labours of its author, to the
able independent treatise (“‘ Natural Selec-
tion ”) of Wallace, and to the synthetic treat-
ments of the whole subject of evolution given
by Haeckel in his “‘Generelle Morphologie,”
and by Spencer in his “ Principles of Biology,”
but to the enormous mass of exposition,
argument and illustration accumulated by
subsequent writers, commencing with Hooker
and Asa Gray, Huxley and Haeckel, but soon
becoming too numerous for mention. We
indicate, however, a few convenient recent
summaries in the “ Bibliography” at the close
of this volume.

But while we must avoid the error of sup-
posing that the last word on natural selection

160 EVOLUTION

was said by Darwin, or that there is not still
abundant opportunity both for reflection and
research in regard to it, we must be clear as
to the essential simplicity of the general theory.
Darwin himself summed it up in a couple of
sentences: ““As many more individuals of
each species are born than can possibly sur-
vive, and as, consequently, there is frequently
recurring struggle for existence, it follows
that any being, if it vary however slightly
in any manner profitable te itself, under the
complex and sometimes varying conditions of
life, will have a better chance of surviving,
and thus be naturally selected. From the
strong principle of inheritance any selected
variety will tend to propagate its new and
modified form.”’

There are here three main propositions :—

(1) Variability is a fact of life. Variations
are of frequent occurrence, and some of them
are certainly transmissible.

(2) Living creatures are very prolific. The
majority die young. There is a ceaseless
struggle for existence and the web of inter-
relations is such that even minute variations
may determine survival.

(8) If variations occur in the direction of
increased fitness, if the variations are trans-
missible, and if there is discriminate selection

SELECTION 161

with reference to these variations, then the
possessors of the fitter variations are bound
to be favoured with longer life and larger
families—with survival, in short. If this is
kept up consistently, then new adaptations,
and, probably with the help of some form of
isolation, new species, will arise.

THE CasE FoR NATURAL SELECTION.—The
theory of natural selection has the marks of
a good theory—it works well as an interpreta-
tive formula in the most varied cases, it has
proved itself a useful instrument of research,
and it has even been made the basis of success-
ful prediction. Darwin himself was under no
misapprehension as to the logical position of
his theory—that its strength was in its in-
terpretative value, not in its direct evidence.
In a letter to Bentham in 1868, he writes:
“The belief in natural selection must at
present be grounded entirely on general con-
siderations—(1) on its being a vera causa,
from the struggle for existence and the certain
geological fact that species do somehow
change; (2) from the analogy of change under
domestication by man’s selection; (8) and
chiefly from this view connecting under an
intelligible point of view a host of facts.”
Given variability, a high rate of increase, the

struggle for existence, the web of life, the
F

162 EVOLUTION

observed fact that most living creatures die
young—it seems to most naturalists to follow
that natural selection is indeed a vera causa
and the survival of the fittest a reality.

Drrect EvIpENCE FoR NATURAL SELEc-
TIoN.—One of the interesting steps of progress
since Darwin’s day has been the attempt to
secure definite evidence of the operation of
natural selection. The theory works well as —
an interpretation, but what we need is actual
proof of discriminate selection, actual evidence
that survivors do survive in virtue of par-
ticular qualities. A few examples of this in
present-day experience will give strength to
the belief that similar processes occurred, as
Darwin suggested, throughout the past.

It is interesting to note that so strong
a selectionist as Weismann considers that
natural selection can be proved only indirectly.
He says: “ A direct estimation of the relative
protective value of the two colours [of a
Sphingid caterpillar] is altogether out of the
question. The survival of the fittest cannot
be proved in nature, simply because we are
not in a position to decide a priori what the
fittest is.’ As Mr. E. S. Russell remarks:
“This is a significant admission from the pro-
tagonist of pure Darwinism, but he admits too
much. It is true we cannot decide a priori

SELECTION 168

what the fittest is, but we can discover by
observation and experiment whether or no
protective coloration has selective value. A
case in point is given by Mr. A. P. di Cesnola
in a short but highly interesting paper in
* Biometrika ”’ for 1904.

“It is well known that the ‘praying
- Mantis,’ Mantis religiosa, occurs in Italy in
a green and a brown form. The former is
usually to be found on green grass, the latter
on herbage browned by the sun. Mr. Cesnola
tied down among green herbage twenty green
Mantis, and among withered grass a similar
number of brown individuals. After seven-
teen days they were all alive. He also
tethered twenty-five green Mantis among
brown herbage, and they were all dead after
eleven days. The converse experiment was
also made, forty-five brown Mantis being
exposed on green grass, and of these only ten
survived at the end of seventeen days. Most
of the Mantis were killed by birds; five of the
green ones were killed by ants. Here, then, is
a proof, quite conclusive though the numbers
are small, of the selective value of the pro-
tective coloration of both races of Mantis.
If green Mantis and brown Mantis be exposed
on green grass, the green ones will survive

rather than the brown, the death-rate will be
F2

164 EVOLUTION

selective. Such a simple experiment gives
more solid support to the view that protective
coloration is due to natural selection than
any accumulation of probabilities.”

It is of enormous importance that cases
similar to the above should be accumulated,
so that stability may be given to the theory
of natural selection by actual evidence that
the survivors survive and the eliminated are
eliminated because of some differentiating
peculiarity or peculiarities. Hence a few
more examples may be given.

Poulton fastened 600 pupz of the tortoise-
shell butterfly to nettles, tree-trunks, fences,
walls, and so on. At Oxford, the mortality
was 93 per cent., and the only pupe that
survived were on nettles, where they were
least conspicuous. In the Isle of Wight, the
elimination was 92 per cent. on fences, as
against 57 per cent. among nettles. Here,
again, there was definite evidence of dis-
criminate elimination.

Professor Crampton’s very careful research
on the pupe of a Saturnid moth, proved dis-
criminate elimination, and yielded also this
interesting result, that the selected characters
(for the most part concerned with dimensions
and proportions) were not such as would have
appeared to be directly or indirectly “‘ useful ”*

SELECTION 165

to their possessors, though they were de-
monstrated to have the high utility of deter-
mining survival—which is indeed, for the
evolutionist, the final criterion of utility.

Professor Bumpus took 186 benumbed
house-sparrows into his laboratory, where
72 revived and 64 succumbed. There were
general differences—of a somewhat subtle sort
—between those that revived and those that
succumbed. General stability of structure
was the essential characteristic of the former.

The fine researches by which the late Pro-
fessor Weldon proved discriminate elimination
in shore-crabs, and by which Professor Karl
Pearson proved a selective death-rate in man,
are of the highest importance, but they require
more exposition than we can give here.

We may round off this section with two
simple observations whose picturesqueness
may emphasize our present point.

Professor Davenport, of the Carnegie In-
stitution for Experimental Evolution, had
800 chickens in a field, 80 per cent. white
or black and conspicuous, 20 per cent. spotted
and inconspicuous. In a short time twenty-
four were killed by crows, but only one of
the killed was spotted.

Finally, a kindred and recent field obser-
vation of our own. In a heavy snowstorm

166 EVOLUTION

at Johannesburg in August 1909, many
hundreds of trees were destroyed by the weight
of snow on the branches. It was interesting,
after the storm, to notice that the elimination
was in a marked degree discriminate. The
trees that suffered most were the imported
Australian trees, such as the Blue Gums and
Black Wattles, quickly growing, with soft
wood, and with abundant foliage that caught
the snow. On the other hand, the deodars
from the Himalaya mountains, constitution-
ally adapted to let the snow slide from their
pendulous branches and acicular leaves, had
hardly a twig broken.

IMPLICATIONS OF THE CONCEPT OF NATURAL
SELEcTION.—As a naturalist of very rich
experience Darwin realized the complexity
of the evolution problem more than most
naturalists have done, and a careful study of
his sentences makes it quite clear that when
he used phrases like “ struggle for existence ”
and “ natural selection,”” which have acquired
by familiarity a somewhat hard and mechani-
cal sound in our ears, he had a singularly rich
concrete content in his mind.

‘* Nothing is easier,” he said, “‘ than to admit
in words the truth of the universal struggle for
life, or more difficult—at least I have found it
so—than constantly to bear this conclusion in

SELECTION 167

mind.” ... “‘I use this term [‘ struggle for
existence ’] in a large and metaphorical sense,
including dependence of one being on another,
and including (which is more important) not
only the life of the individual, but success in
leaving progeny.” ... “Nature may be
compared to a surface on which rest ten
thousand sharp wedges touching each other,
and driven inward by incessant blows.” ...
“It may be metaphorically said that natural
selection is daily and hourly scrutinizing
throughout the world the slightest varia-
tions.” ... “* Battle within battle must be
continually recurring with varying success;
and yet in the long run the forces are so nicely
balanced that the merest trifle would give the
victory to one organic being over another.”

What we wish to suggest is, that Darwin’s
characteristic fundamental idea of the in-
tricacy of interrelations in the web of life,
lies below the idea of the struggle for existence,
and therefore below the idea of natural
selection. Unless we appreciate the funda-
mental natural history fact of the web of life,
we cannot rightly understand how slight
differences can be of critical moment in
determining survival. The entanglements are
so intricate that a slight variation may be of
survival-value to its possessor.

168 EVOLUTION

There is another consideration which Darwin
had certainly in mind, and which, like that
just explained, has often been lost sight of
since. It is illustrated, for instance, by the
researches of Bumpus and of Crampton on
the survival of sparrows and pupe respectively.
The point was, that the survivors seemed to
survive, not because of single peculiarities,
but because of their general stability and
efficiency. As we have already hinted, we
must still admit what Darwin admitted more
than fifty years ago—that it is extraordinarily
difficult to say precisely why one species has
been victorious over another in the great
battle for life. Part of the difficulty is to be
found in the fact that there is seldom a simple
issue.

As Russell puts it :-—

* We should think of each creature as being,
as it were, the point of intersection of a number
of selection processes, of as many processes as
there are significant characters; and since
the significance of characters must change
with the development and growth of the
organism and with every alteration in its
environment, so the sum of selection processes
to which the organism is subjected must be
an ever-changing one.”

“The survival or non-survival of the

SELECTION 169

organism will be determined by the resultant
of all these selection processes, and though
the exact manner of it be extremely complex,
it will be the most generally efficient organism
which will on the average survive. Its
characters will be such as have remained
‘useful’ throughout its life, such as have
adapted the organism to the generality of
life-conditions under which it has lived.”
DIFFERENT KInps oF SELECTION.—There
are two main modes of natural selection.
There is the ordinary “lethal selection,”
which works by the discriminate elimination
of the relatively less fit; and there is “ repro-
ductive selection,” which works through the
increased and more effective reproductivity
incident on the success of the more fit. When
Darwin says “natural selection acts by life
and death ... by the survival of the fittest
and by the destruction of the less well-fitted
individuals,” he describes lethal selection,
and many use the term natural selection in
this sense only. But when Weismann says:
“Those that are best adapted in colour
will secure the most abundant food and will
reproduce most prolifically, and they will
thus have a better prospect of transmitting
their usual colouring to their offspring,” he is
obviously describing reproductive selection.

170 EVOLUTION

Karl Pearson draws a distinction between
** secular selection,’”? which is Darwin’s natural
selection, and “ periodic selection,” which is
less easily detected. The difference is this:
in the ordinary process of natural selection
a change in the mean value of the selected
character must be effected from one generation
to another. But it might also happen that
the extreme deviations from the mean—e.g. the
giants and the dwarfs—were cut off, while
the mean value of the character, e.g. the
average stature, remained unchanged. This
is “periodic selection,” whose reality Weldon
proved in the case of one of the snails: it can
be detected by the diminution in the extent
or range of variability.

There are other extensions of the selection-
idea. Thus in social insects like ants, where
community competes with community, we
see an adumbration of the intersocietary
struggle and selection which we are familiar
with in mankind. There is also some measure
of “struggle of parts within the organism,”
as Roux called it, t.e. between competing
organs and tissues and cells; and where there
is rapid multiplication of elements and discri-
minate destruction there must be a definite
selective process. There is also a well-known
struggle between potential ova, clearly illus

SELECTION ‘Aa

trated in Hydra and Tubularia, reminding us
of the struggle between sister queen-bees.
There is akind of struggle among the hundreds
of spermatozoa in their race towards the ovum.
Allowing a margin for chance, the most
vigorous and sensitive spermatozoa will tend
to succeed and this will be for the advantage
of the species. We are quaintly reminded
of the race between drones to overtake the
queen-bee in her nuptial flight. There is also
sexual selection and germinal selection, which
may be conveniently considered in separate
sections.

SEXUAL SELECTION.—In extension of his
theory of natural selection Darwin proposed
a theory of sexual selection to account for the
frequent occurrence of markedly contrasted
secondary sex-characters, familiar in cases
like peacock and peahen, stag and _ hind.
There are two modes of this sexual selection:
the combats between rival males, and the
preferential mating where the female chooses
or seems to choose.

The issue is clearer in the case of the combats
of males. For when the younger or weaker
candidates are killed, or expelled from the
herd, or left unmated, there seems little
reason to doubt the discriminateness of the
elimination.

172 EVOLUTION

As to preferential mating, there is no doubt
that the males, especially among birds, some-
times show off their varied attractions, but,
as Wallace has consistently maintained, there
is very little convincing evidence that the
female chooses a partner out of a number of
suitors. Still less is there evidence that she
chooses because of any particular excellence
in colour or in song or in dance. In some
cases, however, there is evidence that certain
males are left unmated, and that these are
inferior in attractiveness. In the mysterious
case of spiders, the fastidious female some-
times kills a suitor who does not adequately
please her; as well as afterwards, it may be,
the one who does.

Since Darwin’s day many of the supposed
cases of preferential mating have broken down
rather badly under criticism, but there are
still many facts to go upon. It seems clear
that the suitors are sometimes highly excited,
and that their displays—often more reflex
than deliberate—impetuously excite the fe-
male and overcome her coyness—a character
which, as Groos points out, is of no incon-
siderable racial value. In some passages
Darwin seems to credit the female with a
high degree of “‘ taste” or esthetic fastidious-
ness; but he was probably on safer ground

SELECTION 173

when he wrote, “it is not probable that she
consciously deliberates; but she is most
excited or attracted by the most beautiful,
or melodious, or gallant males.” We do not
know very clearly what choosing may mean
to a hen-bird; but even when she seems to
choose some slight improvement in colour or
song or dance, the probability is that she is
simply surrendering herself to the male whose
tout ensemble has most successfully excited
her sexual interest.

GERMINAL SELECTION.—In 1895 Weismann
suggested that the concepts of “ struggle”
and “‘ selection’ might be usefully extended
to the individual items which compose the
germ-plasm, or, what comes to the same thing,
the inheritance. If we suppose, as there are
many reasons for supposing, that the physical
basis of inheritance in the germ-cells is com-
posed of a multitude of representative vital
particles which are able to feed, grow, and
multiply, then it is conceivable that fluctua-
tions in the nutritive supply of the germ-cells,
and inequalities in the vigour and assimilating
power of the hereditary constituents, may
result in an intra-germinal struggle and
selection.

The general idea is a familiar one, that
nothing succeeds like success; and vice versa.

174 EVOLUTION

A strengthened representative item or deter-
minant in the germ-plasm will nourish itself
more abundantly than its neighbours. “ It
may get into a permanent upward movement,
and attain a degree from which there is no
falling back.”” On the other hand, a weakened
determinant will have less power of attracting
nutriment, and will tend to go downhill. if
it be the determinant of something useful,
then the ordinary process of natural selection
will eliminate the individual that develops
from the impoverished germ-cell; if it be
the determinant of something useless natural
selection will not interfere, and the deter-
minant will continue getting weaker every
generation.

The theory of germinal selection is, of
course, an hypothesis, dealing like Mendel’s
theory of gametic segregation with the in-
visible, but it may be nevertheless useful
in enabling us provisionally to formulate a
number of very puzzling facts, and in sug-
gesting experimental work, on which, even-
tually, we must base our conclusions as to
these abstruse questions.

According to Weismann, germinal selection
helps us to understand the dwindling away
of organs which have sunk below the level
touched by ordinary natural selection; the

SELECTION 175

occasional exaggeration of organs beyond the
limits of demonstrable utility, as may be
illustrated in artificial conditions by the six
feet long tail-feathers of some Japanese
cocks; the occurrence of definitely directed,
appropriate, and simultaneous variations,
and much more besides. It plays into the
hands of personal selection; or, as Weismann
more elegantly phrases it, “it supplies the
stones out of which personal selection builds
her temples and palaces: adaptations.”
FamMILy AND Group SELEcTIONS.—Though
Darwin did not wholly overlook this (indeed
in at least one notable passage he expresses
it) there is no doubt that the general tone
and treatment of Darwinism, even hitherto,
has been deeply coloured by the acute indi-
vidualism of Darwin’s and the preceding age.
We may therefore restate here the concluding
thesis of our own “Evolution of Sex” (1889),
since elaborated in various ways by Drum- |
mond, by Kropotkin and others. It is that
the general progress both of the plant and
the animal world, and notably the great up-
lifts (see Chapter III above), must be viewed
not simply as individual but very largely in
terms of sex and parenthood, of family and
association; and hence of gregarious flocks
and herds, of co-operative packs, of evolving

176 EVOLUTION

tribes, and thus ultimately of civilized societies
—above all, therefore, of the city. Huxley’s
tragic vision of “nature as a gladiatorial
show,” and consequently of ethical life and
progress as merely superposed by man, as
therefore an interference with the normal
order of Nature, is still far too dominant
among us. It threatens even to-day to con-
fuse the nascent science, and still more to
wreck the incipient art, of Eugenics, in fact
to encourage and defend that massacre of
the innocents which is expressed in the death-
rate of every community; and to extend this
to a corresponding view of legislation and
government. Here, in fact, is opening the
greatest practical controversy of our science,
in comparison to which all others have been
but academic—that ultimately between the
Herodian and the Magian view and treatment
of the child, and between essential renewals
of the Cesarist and of the Christian ideals
of the community, upon our modern spiral.
Yet since this is a modern spiral, we must
harmonize this controversy ; we must seek
the due correlation of the ideals of organic
and of psychic selection. For this we need
above all some clearer vision of the ideals of
evolution—Olympian for the body, Parnassian
for the spirit, and even more—in fact, an

SELECTION 177

evolutionist hope and aim not only for the life
of the individual, but increasingly for the
uplift of the race and of the community. On
the way towards this, selective consciousness
and conscience are indispensable, love as
individual, love as social; and with these
sacrifice also, it may be of love or of parent-
hood itself. Nor is the social control a mere
choice between Draconian harshness on one
hand and shallow philanthropy on the other;
for these are but rival cruelties, that to the
individual, this to the race. To determine,
then, the ideal goal and the true process of
selection for our own species, is thus the
supreme problem and task which are opening
before us as evolutionists.

AuxiLiARY HypoTHEsis oF IsoLATION.—
We have already referred to the occurrence of
particular species on particular islands in the
Galapagos Archipelago, and there are a great
many similar cases which suggest that isola-
tion means something in evolution. The red
grouse is peculiar to Scotland, but it has
doubtless been derived from the closely-related
stock of the Scandinavian willow grouse.
While the zoologist has lately distinguished
an Orkney vole and a St. Kilda wren, every
one knows the Shetland pony, the Highland
cattle. There are said to be eighty species

178 EVOLUTION

of the land-snail Cerion in the Bahamas, and
Gulick records over 200 species of the land-
snail Achatinella in the various valleys of the
Sandwich Island Oahu.

Many evolutionists—Wagner, Weismann,
Gulick, Romanes, Jordan, and others—have
worked at the idea of Isolation, as a directive
factor in evolution; and Romanes maintained
that it was a sine qua non in the origin of new
species. The term must not be thought of
in any narrow sense; it includes all the means
which restrict the range of intercrossing
within a species: geographical barriers, such
as arise when a peninsula becomes an island;
temporal barriers, such as arise when the
members of a species reach sexual maturity
at different times of year; habitudinal barriers,
when a species splits into two or more castes
with different habits of life; physiological
barriers, such as arise by some variation in
the reproductive organs; and psychological
barriers, which rest on profound antipathies.

What probably happens is this: a success-
fully vigorous and adaptive species spreads;
the several contingents become isolated from
one another; and, if different variations
spring up in several or all of the contingents,
then, other things being equal, isolation
will favour the origin of distinct species. “‘I

SELECTION 179

do not doubt,”’ Darwin said, “ that isolation
is of considerable importance in the forma-
tion of new species.” It may be of some
importance in preventing intercrossing, but
it is much more likely that it works by bring-
ing about close inbreeding, which develops
prepotency or stability of type.

In the human world, the manifold range
of individuality presented by regions favour-
able to family, village, and clan isolations,
such as Scotland or Norway, Greece or Pales-
tine, thus becomes intelligible. Again, in
that deterioration of the cities of the plain,
which is so frequent throughout history, so
evident to-day, we may increasingly fear an
organic factor underlying the obvious social
ones—that of reversion through intercrossing;
as when the highly individualized races of
pigeon sink back to the comparative uni-
formity of the ancestral rock-dove. Yet from
this apparent regression, really a profound
and intimate panmixis, a thoroughgoing cross-
fertilization, who shall say what new variations
may arise, what new selections also—even
what evolving guidance of these ?

EUGENICS AS A RENEWAL OF EVOLUTION.
—Thus we return to man as transformist, a
discussion already opened in Chapter II,
but this time appearing in a fresh perspec-

180 EVOLUTION

tive. It is admitted by all inquirers into
the origins of civilization on one hand, into
the origins of cultivated plants and of domes-
ticated animals on the other, that practically
all these familiar and indispensable com-
panions of man are of prehistoric origin, and
have risen along with him, as he with them.
But now the corollary of this: imagine the
immensity not only of patient labour, but
of selective skill, which are comprised within
the steps from wild grasses to cereals, from
crab-apple and wild olive to the vast and
fruitful groves which must assuredly have
covered the prehistoric cultivation terraces
of old, stretching as these did throughout
the Mediterranean region from Portugal to
Syria—thence through Asia Minor to Persia,
to Korea itself. One has taken the pains
to calculate the actual capital value of
these ancient Mediterranean terraces, and
brings out the marvellous, yet credible,
result that the actual economic wealth of
this remote prehistoric world far exceeded
that of the Mediterranean to-day; and this
not merely in its agriculture, or with roads
and railways thrown in, but with the existing
cities as well! Here then is a view of the
early human past very different from the
picture of groping brutishness, of promis-

SELECTION 181

cuity and struggle with which nineteenth-
century anthropology was too much obsessed;
for if we seek the modern representatives
of these old cultivators and selectors, these
breeders and arboriculturists, at their best
we must seek them at the very highest grow-
ing-point of our own civilization to-day. For
with all respect to the great mechanical in-
ventors, and the masters of the physical
sciences who have accompanied them, we
claim a higher primacy in science for Darwin
and his peers, and this alike as regards vision
of the universe, as in organic not merely
physical evolution, and in potential and forth-
coming, if not yet fully actual contribution
to the service and uplift of man. In short,
these prehistoric transformists of wild life
into cultivated fruitfulness and domesticated
use, had already among them their Darwins
and Vilmorins, their Gartons and Burbanks;
with the one important difference—that these
achieved immeasurably greater practical re-
sults than have as yet their modern successors.

Again, is it likely that those who could
transform the lurking, wolfish depredator into
the trusty guardian of their flocks, the wild
cattle into patient ox and gentle cow, the
wild horse into the Arab, neglected their own
breeding as we and our progenitors have done

182 EVOLUTION

—or even misunderstood it as all historie
aristocracies have done? True, we have not
their history in the letter, yet we have much
of it in the spirit; that of the folk-tales and
fairy tales, of which the most childlike and
sympathetic of the sciences is steadily re-
covering the values and the meanings; and
these old child-tales are even returning to-
wards their social and vital applications—
above all that of presenting the ideal of love
as the quest of life which our fathers called
romantic, which we now call eugenic and
think modern. Whereas out of all this re-
covery of the golden age and of the ancient
garden of fruitful labour, does there not
emerge the idea that its guardians, so much
wiser and happier than we knew, had thought
not only for the simpler creatures they cared
for and ruled and elevated, but for themselves
and for each other ?—in short, that our
modern Eugenics, latest-born even among the
evolutionary sciences, may yet be among
the very oldest; and that now once more,
at the opening of that new epoch of world-
consciousness and world-activity which is
involved no less thoroughly by the evolution
theory than was the passing industrial age by
the advance of mechanical science, the ancient
evolutionary past is being again reborn ?

FUNCTION AND ENVIRONMENT 188

CHAPTER VI

ORGANISM, FUNCTION AND ENVIRONMENT :
IN RELATION TO EVOLUTION

The Conception of Life—The Evolution Idea, its History
—Theories of Evolution, Classified—Relations between
Organism and Environment—Indirect Importance of
Modifications— The Réle of Function — The Living
ey et of Vitalism—Initiation into Psy-
chology.

THE ConcepTION OF LirE.—The definition
of life is the last, not the first, question for
the student of Biology. What we have to
do first is to study the actual happenings, the
changes, the movements, the activities that
go on under our eyes. It is only after we
have given careful study to the actual fact
of living—which is a process, a dynamic
relation—that we can profitably inquire into
the particular secret of the agent.

By many who have begun at the wrong
end—wrong from the point of view of scientific
method—the conception of Life, the organ-
ism’s secret, has to be left as a mystery, or
is mistaken as an entity. By others it is
thought of in terms of chemical substance,
like the “ elixir” or “‘ quintessence ” of old,
or again in terms of modes of energy, which
are “physical” or “vital,” to different

184 EVOLUTION

schools, of materialistic or idealistic leanings
respectively, albeit physical rather than
biological in either case. Our present point
is that before inquiring into the secret of the
organism—* Life’’ in the innermost and
organismal sense—we must seek a deeper
appreciation of the process of living. What
then is this? On the one hand there is
the Environment in its action upon the
organism; and on the other the Organism in
its reaction to and action upon the environ-
ment; the dynamic relation, in its twofold
aspect, is called Function.

THe EvoiutTion Ipra: its History.—
Before we seek to relate the various theories
of evolution factors that have been suggested
to the three categories of Biology—Organism,
Function, Environment—it may conduce to
clearness to consider for a little the general
** doctrine of descent.”

While it is true, as Professor Osborn puts it,
that “‘ Before and after Darwin” will always
be the “ Ante et post urbem conditam ” of
biological history, it is also true that the
general idea of organic evolution is very
ancient. Several of the Greek philosophers
looked upon Nature as having developed,
and as being still in process of change. Aris-
totle seems to have recognized an ascending

FUNCTION AND ENVIRONMENT 185

series from polyp to man and an age-long
movement towards increased perfection.
Static conceptions, however, prevailed, with
some rare exceptions, through the long
interval between Aristotle and Bacon, who
was one of the first to think definitely about
the mutability of species. But after the
Renaissance it was among the “ philosophers,”
not among naturalists, that the evolution
idea began again to live and move. The
first naturalist to give a broad and concrete
expression to the evolutionist doctrine of
descent was Buffon (1707-1788). Erasmus
Darwin (1731-1802), Charles Darwin’s grand-
father, was another firm evolutionist, prob-
ably influenced by Buffon, and it is very
interesting to observe how much of the
argument in his “ Zoonomia” might stand
to-day. Lamarck (1744-1829) was above
all thoroughgoing in his evolutionism ; and
Haeckel rightly speaks of his “ Philosophie
Zoologique” as “the first connected and
thoroughly logical exposition of the theory of
descent.” ,
Geesides the three old masters, as we may
call them, Buffon, Erasmus Darwin and
Lamarck, there came other quite convinced
pre-Darwinian evolutionists — Treviranus,
Etienne Geoffroy Saint-Hilaire, Goethe, Robert

186 EVOLUTION

Chambers, and many others. Darwin refers
to thirty-four more or less_ evolutionist
authors in his Historical Sketch, and the list
might be added to. Especially when we come
near 1858 do the numbers increase, and we
must never forget that Herbert Spencer not
only marshalled the arguments for Evolution
in a very forcible way in 1852, but applied
the formula in detail in his “ Principles of
Psychology” in 1855. We must also re-
member that the genetic view of nature was
insinuating itself in regard to other than bio-
logical orders of facts, here a little and there
a little, and that the scientific temper had
ripened considerably since the days when
Cuvier laughed Lamarck out of court.

We have inserted this historical reference
to pre-Darwinian evolutionists, since it is
important to shake ourselves free from all
creationist appreciations of Darwin; but it
would be a perversion of history to suggest
that he simply entered into the labours of his
predecessors. In point of fact, he knew very
little about them till after he had been for
years at work. Let us ask rather how it was
that Darwin succeeded in winning a world-
wide acceptance of the evolution idea, where
so many others had failed !

Because, in the first place, he had clear

FUNCTION AND ENVIRONMENT 187

visions—“‘ pensées de la jeunesse, exécutées
dans l’age mir ”—which his indocile refusals
to submit to outworn university curricula
had made possible, which the “ Beagle”
voyage made fuller and more vivid, which
an unrivalled British doggedness made ever
more positive and real—visions of the web
of life, of the fountain of change within the
organism, of the struggle for existence and its
winnowing, and of the spreading genealogical
tree. Because, in the second place, he put
so much grit into the substantiation of his
visions, putting them to the proof in an argu-
ment which is of its kind—direct demonstra-
tion being out of the question—quite un-
equalled. Because, in the third place, he
broke down the opposition which the most
scientific had felt to the seductive modal
formula of evolution, by bringing forward a
more workable theory of the process than had
been previously stated. Nor can we forget,
since questions of this magnitude are human
and not merely academic, that he wrote, in
his mingled simplicity and condescension,

so that all men could understand.
THEORIES OF EVOLUTION, CLASSIFIED.—

So far the general doctrine of descent; but
some of the pioneers did more than apply
the evolution idea as a modal formula of

188 “ EVOLUTION

becoming: they began to inquire into the
factors in the process. How are their theories
related to the three categories—Organism,
Function, Environment ?

To some the fundamental fact is the living
Organism—a creative agent, a striving will,
a changeful Proteus, selecting its environment,
adjusting itself to it, self-differentiating and
self-adaptive—Life dominating nature, master
of its fate.

To others it has always seemed that the
emphasis should be laid on Function—on
activity and practice, on use and disuse, on
doing and not doing.

To others, again, what counts for most is
the Environment. This wakes the organism
to action, feeds it or starves it, gives it new
experiences or imprisons it within the old.
Environment prompts the organism to self-
expression, yet moulds it and prunes it,
punctuates its life, and finally puts in the
full stop, of death.

Let us take some historical illustrations.
There is no doubt that Buffon laid great
emphasis on Environmental influences—espe-
cially of climate and food—as direct trans-
forming factors.

The central idea of Erasmus Darwin’s
evolutionism was Functional: that wants

FUNCTION AND ENVIRONMENT 189

stimulate exertions and that these result in
improvements, which subsequent generations
make better still. This was Lamarckism
before Lamarck, as his grandson pointed out.
Lamarck agreed with Buffon in maintain-
ing that external conditions directly moulded
plants, but differed from him in denying this
for animals, “‘ for environment can effect no
direct change whatever upon the organiza-
tion of animals.” In so doing, despite the
obvious exaggeration, we must credit him
with clear recognition of the relative passivity
of the vegetative life, the relative activity
of that of the animal. The central idea of
his theory, however, was the cumulative
transmission of functional modifications:
“Changes in environment bring about
changes in the habits of animals. Changes in
their wants necessarily bring about parallel
changes in their habits. If new wants be-
come constant or very lasting, they form new
habits, the new habits involve the use of
new parts, or a different use of old parts,
which results finally in the production of new
organs and the modification of old ones.”
But beyond this he clearly insisted on the
inward urge or effort of the organism to realize
its inmost wants, and to express this in
change of habits and even of structure.

190 EVOLUTION

Treviranus (1776-1837), whom Huxley
ranked beside Lamarck, was on the whole
like Buffon in attaching chief importance to
the influence of a changeful environment,
both in modifying and in eliminating. But
he had another deep idea, which Goethe
shared, of an inherent formative impulse in
the creature. “In every living being there
exists a capability of an endless variety of
form-assumption ; each possesses the power
to adapt its organization to the changes of
the outer world, and it is this power, put
into action by the change of the universe,
that has raised the simple zoophytes of the
primitive world to continually higher stages
of organization, and has introduced a count-
less variety of species into animate Nature.”

But it is in Goethe that we find the fullest
expression of the idea of the innate tendency
of a living creature to fuller self-realization.
At the same time he held with Lamarck that
“the way of life powerfully reacts upon all
form,” and with Buffon that the orderly
growth of form “yields to change from
externally acting causes.”

The main idea of Goethe, of an inherent
growth force, has constantly reappeared,
notably among the American paleontologists :
witness Cope’s “ bathmism ”; and now among

FUNCTION AND ENVIRONMENT 191

the whole rising generation of vitalists,
German and other. The anatomist and sys-
tematist, the chemical and physical physie-
logist, have been, and still are, wont to reject
this; and not without reason—that of the
positivism of science, which rightly shrinks
from the acceptance of abstract entities and
causes. Undeniably, whatever may be our
sympathy for these manifold suggestions of
vitalist evolutionism, they are still too much
open to Moliére’s ridicule, as of explaining the
effect of opium by its “ dormitiveness.”’

We need not continue these _ historical
illustrations, but the important point is this,
that some naturalists, such as Buffon, empha-
sized the importance of the Environment;
others, such as Lamarck, laid the main stress
on Function; others, such as Goethe, discerned
that, after all, the moving spirit in the drama
of evolution is the Organism. It may be
said without dogmatism that the adequacy
of an evolution theory is in proportion to its
recognition of all the three categories, which
give, in point of fact, the three aspects of
life.

Surely, whatever may be the limits of
Darwinism, its superiority to preceding evolu-
tion theories was in part that it got nearer to
seeing life whole. The Organism was appre-

192 EVOLUTION

ciated: it is the fountain of change; it is
aggressive, insurgent, even riotous, in its mul-
tiplication; it struggles, it even chooses.
Rightly or wrongly, Function was also appre-
ciated: use and disuse have their organic
consequences, and for Darwin these were, at
least in part, transmissible. Similarly the
Environment was appreciated, alike in mould-
ing and in pruning. Finally was added the
idea of Nature’s environmental and adaptive
sifting—the essentially new and triumphant
doctrine of Natural Selection.

The post-Darwinian scepticism as to the
transmission of functional and environmental
modifications might seem to involve a denial
of the evolutionary importance of anything
but the varying organism and the winnowing
environment; but what it really means is that
the previous appreciation of the evolutionary
importance of function and of environment
was not subtle enough. We ask, therefore,
wherein the importance of function and en-
vironment may consist, t/ there is no direct
transmission of the individual modifications
which they undoubtedly produce. This in-
volves a careful inquiry into the relation
between organism and environment.

RELATIONS BETWEEN ORGANISM AND EN-
VIRONMENT.—(1) It is impossible to separate

FUNCTION AND ENVIRONMENT 198

living creatures from their surroundings.
To do so in fact is to kill them; to do so in
theory is to turn biology into necrology, a
vice which has always too largely infested
our science, paralyzed its thinkers, sometimes
even skeletonized or mummified them. There
is an endless diversity in environments, and
some of them are most extraordinary—the
iceberg, the hot spring, the mountain top, the
abysses of the ocean, the cave, the interior
of another creature—but for each kind of
organism there is an indispensable minimum
of supplies and influences, apart from which
it cannot develop, or grow, or continue to
live. This is the fundamental relation of
living things, that of constant and normal
environmental dependence.

(2) But surroundings are changeful and the
living creature changes with them. In many
cases, where the external changes are regularly
recurrent, like seasons and tides, the organism
falls into step with them; so that there are
internal rhythms, punctuated by external
periodicities. The latter may come to be
needed only as the liberating stimuli, or
trigger-pullers, of the former. Experiments
show that some young tropical acacias are
hereditarily wound up, as it were, to a twelve

hours’ day and night—times of leaf-expansion
G

194 EVOLUTION

and leaf-closure. The cold of winter is
probably the stimulus rather than the efficient
cause of the brown stoat becoming the white
ermine.

(8) To some of the irregular changes in its
surroundings the living creature is able to
adjust itself temporarily. The warm-blooded
bird or mammal can within limits adjust its
heat-production and heat-loss so that the
temperature of the body remains the same
whether that of the environment rises or falls.
In the case of many of these transient adjust-
ments there remains no abiding result that
can be detected.

(4) Insensibly, however—for it is all a matter
of degree—we pass to cases where the re-
sponses to environmental change last for a
considerable time. Sun-burning on a summer
holiday, increase in the size of a muscle after
a course of exercises, the blanching of the
banked-up celery are familiar illustrations.
The bodily change has taken a firmer hold
than in the case of transient adjustments, but
it is still a passing change. Like a bow
unstrung the organism rebounds, approxi-
mately to its previous state.

Semon has recently propounded a theory—
of the “‘ Mneme ’—which is of interest in
this connection. The general idea of it is,

FUNCTION AND ENVIRONMENT 195

that when living matter is affected by a
stimulus, its quality cannot be the same as
it was before the stimulus. Even a bar of
iron is not quite the same after it has been
once struck; how much more a living creature
which is specialized towards gaining and
garnering experience. There is always some
residual effect; this Semon calls an “ en-
gram,” and the sum of the engrams of a living
creature is its ““Mneme’”’—its organic lore,
its bodily and sub-conscious memory we may
practically say.

The “‘Mneme” may have particular im-
portance in cases where penetrating stimuli,
like those of the seasons, recur periodically,
re-vivifying and re-enforcing the previous
accumulations of experience. Along this line
of thought, Semon, and following him Francis
Darwin and others, may be said to be
returning towards a position again essentially
Lamarckian, for thus the results of experience
may be conceived as accumulating from
generation to generation, even although, as
Weismann maintains, individually acquired
bodily modifications may not be entailed as
such. The effects of an often repeated
stimulus may saturate through the organism
by nerve paths and protoplasmic bridges and

the fluent blood; what then precludes them,
G2

196 EVOLUTION

in some cases at least, from reaching even the
germ-cells in their recesses ? ‘

In this connection, it is only just to recall
the remarkable speculative insight of the late
Samuel Butler, that most convinced and
argumentative of Lamarckians, who, more or
less simultaneously with Hering in Prague,
propounded a generation ago much the same
doctrine of ““ Organic Memory,”’ as that which
we now owe to Semon. Haeckel too has
expounded much the same doctrine; and no
doubt in increasingly clarified form it must
henceforth be reckoned with.

(5) Insensibly, again—for it is all a matter
of degree—we pass from the temporary dints
impressed upon the organism by the environ-
ment to those that last. There are many
cases in which the novel conditions provoke
a structural change from which there can be
no rebound, the limit of organic elasticity
having been passed. These lasting changes
are technically called ‘“‘ modifications” or
“acquired characters.” A tree may be per-
manently blown out of shape; over-exertion
at high altitude may strain the heart beyond
repair; a man may be tanned for life by the
tropical sun.

(6) Quite different from the last are cases
where some change in the environment of

FUNCTION AND ENVIRONMENT 197

the parent provokes a variation in the off-
spring. The best instances, as yet, are to be
found in the experiments carried on for many
years by Tower on beetles of the genus
Leptinotarsa, which he subjected to unusua!
conditions of temperature and humidity, when
the male and female reproductive organs of
the parent were at a certain stage in their
development. The body of the parent ex-
hibited no modification, but the external
influence, saturating through the body, was
sometimes operative on the germ-cells and
thus on the offspring. In some cases there
were remarkable changes in colour and mark-
ings, and even in minute details of structure.
And there was no reversion to the parental
condition.

(7) Another “‘ organism-environment ”’ rela-
tion is that inaplied in the struggle for existence,
which in its widest and truest sense includes
all the reactions of living creatures to their
surroundings and difficulties. The physical
world is careless of life; one living creature
presses upon another, competes with another,
devours another. Thus, while the environ-
ment is a stimulus, it is also a sieve. It has
an eliminating action which, as we have seen,
is often discriminate; it sifts and winnows;
the result is extinction for some, but adapta-

198 EVOLUTION

tion, and this it may be a degree more perfect,
for others.

(8) But we must not think of the matter too
fatalistically, as if organisms were always like
helpless fishes, around which the environ-
mental net closed, only the little ones getting
through the meshes. True, they cannot
by taking thought increase or decrease their
stature, even to save their lives; yet they are
fertile in device, persistent in endeavour.
Even the worm will turn; even the plant will
answer back. Living creatures are agents;
they thrust as well as parry; they act on their
surroundings, modifying them; they are ever
seeking out new environments, and conquering
them.

The foregoing analysis has_ sufficiently
shown that the range of relations between the
living creature and its surroundings is a very
complex one,—of functional dependence, of
periodic punctuation, of transient adjustment,
of more lasting adjustment, of permanent
modification, of variational stimulus, of elimi-
nation or selection, up to active initiative upon
the organism’s part. The evolutionary import
of these relations is no doubt even more intri-
cate than we can yet see. The old theories
of direct adaptation in response to altered
environmental conditions, or as the result

FUNCTION AND ENVIRONMENT 199

of use and disuse, were much too simple. But
there has also been far too great simplicity
in the view too long prevalent in the generation
after Darwin, and to some extent even to-day,
that each species must, so to speak, wait with
folded hands, until fit variations emerge,
whether these be “ spontaneous” (7.e. unex-
plained), or arise in course of shufflings of
qualities and properties that undoubtedly
must occur in the history of the germ-
cells.

InpirEcT ImporTANCE OF MODIFICATIONS.
—The interesting suggestion has been made,
independently by Mark Baldwin, Lloyd
Morgan, and Osborn, that useful “ modifica-
tions”? may serve as the fostering nurses of
‘“‘ variations’? in the same direction. We
quote from Lloyd Morgan a brief statement
of thisidea: ‘* Suppose that a group of plastic
organisms is placed under new conditions.
Those whose innate plasticity is equal to the
occasion are modified and survive. Those
whose plasticity is not equal to the occasion

are eliminated. . . . Such modification
takes place generation after generation, but,
as such, is not inherited... . . But any con-

genital variations similar in direction to these
modifications will tend to support them, and
to favour the organism in which they occur.

200 EVOLUTION

Thus will arise a congenital predisposition to
the modifications in question.”

*“* The plasticity still continuing, the modi-
fications become yet further adaptive. Thus
plastic modification leads, and germinal varia-
tion follows; the one paves the way for the
other.”’

‘** The modification, as such, is not inherited,
but is the condition under which congenital
variations are favoured and given time to get
a hold on the organism, and are thus enabled
by degrees to reach the fully adaptive level.”

Yet another consideration. Although we
do not know of any case of the transmission
of a modification as such, or even in a repre-
sentative degree, we, of course, agree with
Weismann in admitting that modifications
may have secondary effects on the germ-cells,
and thus on the offspring. Inthis way “ nur-
ture ’? may come to have a racial importance.
Nor can we forget that the environment of
mammalian mothers is bound to have an
influence on the unborn young, which shares
the maternal life so closely. Apart from the
‘‘mysterious wireless telegraphy of ante-
natal life,’’ there is a sharing of the diffusible
substances carried by the blood.

THE ROLE oF FunctTion.—We cannot go
back to the cruder forms of the Lamarckian

FUNCTION AND ENVIRONMENT 201

theory, and believe that the giraffe lengthened
its neck by stretching it; yet we must be-
ware of taking too simple a view of what
function implies. What are the certainties ?
We know that development—the expression
of an inheritance—demands functional as
well as environmental stimuli. Practice
makes an organ possible. Without exercise
it will not develop fully. Again, we know
that changes in function have great individual
importance. By force of smiting one be-
comes a smith. Even if there be no multi-
plication of muscle-fibres after the more
strenuous function began, each fibre is larger
and worth more. Contrariwise, disuse means
deterioration; when we rest too much we rust.
No one has ever doubted the individual im-
portance of functional modifications. Further,
although the transmission of a functional
modification remains unproved, the secondary
and indirect results may influence the germ-
cells and the offspring. It is idle to say that
what living creatures do. or fail to do has no
racial importance. Another certainty is that
by its activity a living creature, being no
mere puppet of fate, may alter the whole
situation. This, again, may have evolu-
tionary interest, even if it ends fatally.
Admitting all this, can we say more ?

202 EVOLUTION

THe Livinc Orcanism.—The secret of
Life is baffling to the human intelligence,
refusing to be formulated. Often the con-
ception of Life has seemed to biologists to
be within reach, and then it is perhaps farthest
away. It recedes as we approach. Yet,
though intelligence fails, do we not at times
come nearer to it through sympathy? Words-
worth, Emerson, Meredith, these and many
other Nature-poets are perhaps the truest,
because deepest, biologists of us all.

It is partly in the intrinsic difficulty of the
problem—vital activity being something be-
tween mechanical causality and our conscious
purposing—and partly in the way that
science ever takes on the colour of its time,
that we must look for an explanation of the
historical oscillations of biology between the
mechanistic interpretations of the living organ-
ism and the vitalistic appreciations of it.
Now it is a machine and again it is a spirit,
now an automaton and again a free agent,
now an engine and again an entelechy. The
pendulum of thought continues to swing.

Despite the fact that as yet no vitalist
writer has succeeded in making himself
and his nomenclature really intelligible to
any other, and that the frequent gibes at
vitalistic metaphysics and mysticism remain

FUNCTION AND ENVIRONMENT 2038

largely justified, we confess that the modern
movement of vitalism has our increasing
sympathy. It affects our evolutionism to
this extent at least that we feel compelled to
recognize the persistence of some originative
impetus within the organism, which ex-
presses itself in variation and mutation, and
in all kinds of creative effort and endeavour.

There are two sides to all doctrines of vital-
ism—a negative side which argues towards
the impossibility of holding to the purely
mechanistic interpretation, and a positive
side which attempts some further elucidation
of the life-mystery.

As an outspoken statement by a competent
physiologist and physician of the vitalist
position, on its critical side, we may take
Dr. Haldane’s recent British Association
address (Dublin, 1908). “In Physiology,
and Biology generally, we are dealing with
phenomena which, so far as our present
knowledge goes, not only differ in com-
plexity, but differ in kind from physical and
chemical phenomena; and the fundamental
working hypothesis of Physiology must differ
correspondingly from those of Physics and
Chemistry.” . . . “The physico-chemical
theory of life has not worked in the past and
never can work. As soon as we pass beyond

204 EVOLUTION

the most superficial details of physiological
activity it becomes unsatisfactory; and it
breaks down completely when applied to
fundamental physiological problems, such as
that of reproduction.”

THEORIES OF ViTALISM.—A_ constructive
and comprehensive endeavour to formulate
a doctrine of vitalism is that of Dr. Hans
Driesch’s recent Aberdeen Gifford Lectures,
in which the author, working from his stand-
point as an experimental embryologist, ad-
vances technical proofs of the “ autonomy
of life,” and of its specific distinctiveness
from the not-living. He advances an elabor-
ate threefold argument to show how the
interpretation of a living creature as a
machine breaks down, both in regard to its
functioning and its development; and he
seeks to show that it is necessary to postulate
an immaterial autonomous factor, or “ en-
telechy *” which punctuates the transforma-
tions of energy that go on within the body.
This “‘entelechy” is the living creature’s
innermost secret, in fact its directive soul.

Another clear and comprehensive exposi-
tion of a theory of Vitalism will be found in
Bergson’s “Creative Evolution.” Bergson
dwells on the close resemblance between the
life of the organism and our own personal

FUNCTION AND ENVIRONMENT 205

experience. We change without ceasing; the
organism is in a state of ceaseless flux
which we call metabolism. Both have the
mysterious quality of “‘ durée”—but duration
in more than the merely physical and
chronological sense; for what he means by
it is “‘the continuous progress of the past
which gnaws into the future and which
swells as it advances.” ‘Our personality
shoots, grows and ripens without ceasing.
Each of its moments is something new added to
what was before. We are creating ourselves
continually.” So of an organism it may be
said that “its past, in its entirety, is pro-
longed into its present, and abides there,
actual and acting.” ‘“ Continuity of change,
preservation of the past in the present, real
duration—the living being seems, then, to
share these attributes with consciousness.
Can we go farther and say that life, like
conscious activity, is unceasing creation ? ”
Bergson answers this question by an
emphatic affirmative. The spontaneity of
life is manifested by a continual creation of
new forms. “A hereditary change in a
definite direction, which continues to ae-
cumulate and add to itself so as to build up
a more and more complex machine, must
certainly be related to some sort of effort,

206 EVOLUTION

but to an effort of far greater depth than the
individual effort, far more independent of
circumstances, an effort common to most
representatives of the same species, inherent
in the germs they bear rather than in their
substance alone, an effort thereby assured
of being passed on to their descendants.
There is an original creative impetus in life,
which passes from generation to generation
of germs, is sustained right along the lines of
evolution among which it gets divided, and
is the fundamental cause of variations, or at
least of those variations that count.”

We see, then, how Bergson psychologizes
life without needing to invoke the “ spiritual
influx ”’—too much a “deus ex machina ”—
which is demanded by Wallace, to explain
the genesis of man’s higher faculties, and
indeed to explain the other great steps in
evolution. Metaphysical and abstract though
his interpretation remains, too shadowy as it
is for the needs of the working naturalist,
we must recognize that here is afresh and
forceful re-statement of the essential thought
of Lamarck, of Goethe, of Robert Chambers,
of Butler, and of later vitalists; in fact, of all
who have most deeply felt the supreme im-
portance of the organismal factor in evolution.
More even than this, here is a new conversion

FUNCTION AND ENVIRONMENT 207

of the philosopher into the biologist, and
when we recall the enthusiasm with which
the late Prof. William James proclaimed him-
self as the disciple and exponent of Bergson,
we see how fruitful may be this re-opening
alliance of the abstract with the concrete
thinker. Again, as in Spencer’s day, our
biology and our psychology have to be
correlated and unified anew, and all towards
the philosophy of evolution. Still, with all
respect to the philosophers, who have taken
this great step towards becoming naturalists,
we cannot but feel that the next step in pro-
gress must depend upon how far we naturalists
can in our turn become something of psycho-
logists and even philosophers.

It is a matter of common sense and expe-
rience, which we are all verifying any and
every day for ourselves, that the psycho-
logically-minded person can and does see
farther into life, and sees more aspects of it,
than the most skilled mechanic, be he the in-
ventor of machines or the discoverer in physics.
After all, the biologist cannot be content until
he becomes something more than a physicist
and chemist, an anatomist, systematist and
so on: beyond its structures and reactions,
life has an aspect of behaviour, and that is,
after all, the main one. As he grasps this, he

208 EVOLUTION

becomes a bio-psychologist, and starts upon
fresh quests; at first, no doubt, and properly,
armed cap-a-pie with brass instruments
and copper wires. Faithful to his physico-
mechanical upbringing, he measures reaction-
times, he plots curves, he again reassures him-
self that there is nothing more in Life. But
one day danger and opportunity arouse him;
another love or sorrow awakens him altogether
—not most probably to any mystic vision such
as vitalists are credited with by their oppo-
nents, usually far too generously, we suspect,
but at any rate to make the discovery still so
rare for men of science, albeit an open secret to
plain folk, that beyond the often measurable
bio-psychoses of the psychological laboratory
there are psycho-bioses, often immeasurable,
in the greater world-laboratory of life. After
this initiation, a new and_ before-unsus-
pected thought-world opens; and within this
begins the real controversy, of reconciling the
claims and methods of orderly science with
these deepest, yet most incontestable, data
of experience. In such ways the enduring
contrast, or at least the bias, of the mechan-
istic and the vitalistic training and tempera-
ment may be continued upon a higher spiral,
with results ever more fruitful, yet in principle
already in view—from one side that of carry-

\

\
\

FUNCTION AND ENVIRONMENT 209

ing physical and chemical, structural and
functional inquiries onwards to new triumphs
of analysis; but also, from the other side, that
of tracing the psychic process deeper and
deeper, into the very germs and origins of life.
In a word, then, it is for the mechanistic
biologist to cease from scoffing at the vitalist
as a “mere mystic,” and to set about master-
ing psychology until he can turn scientific
clearness upon his vagueness. Till then he
but lays himself open to a counter-sneer
from the mystic, and a worse nickname—that
of “ necrologist.”

INITIATION INTO PsycHoLtocy.—How is the
biologist, trained in the dissecting-room, the
laboratory, the museum, the herbarium, or
even in the garden or the field, to get at the
psychological point of view, even when he
begins to feel that he here has something
to learn, that he in fact requires it, if he is
to be a biologist indeed ? Even in Bergson,
much more in the German vitalists, there is too
much of the intangible. Let him begin with
Darwin himself, and he may soon feel, that
like many an admiring disciple before now,
he has not grasped the fully rounded thought
of his own master. With rare exceptions,
like Lloyd Morgan for instance, what natural-
ist of us all is not far more at home with

210 EVOLUTION

Darwin when he is in his field watching his
earthworms, in his garden watching the bees,
in his greenhouse among his insectivorous or
moving plants, or in his study writing ‘“‘ The
Origin of Species,” than when already as a
youth upon the “Beagle,” he was keenly
collecting data which eventually formed the
foundation of his “‘ Expression of the Emotions
in Man and Animals,”’ a masterwork of com-
parative psychology; or, as a grandfather in
his easy-chair, keenly and kindly watching
the daily growth of his child-playmate, and
so laying foundations for that great science
of mental embryology still best known by
its fit and homely name of child-study? A
naturalist, too, has a respect for embryology :
let him, then, take as guide the foremost
of American mind-embryologists, President
Stanley Hall (see the American Darwin Cen-
tennial volume, “‘ Fifty Years of Darwinism’’),
who after creating a very paradise for the
guild of brass instruments, and long and lead-
ing services to child-study, has of later years
applied himself to the no less fruitful and
perhaps even more important field of Ado-
lescence; that magic Dionysiac moment of
human metamorphosis, in which wisdom and
folly, madness and genius strive for mastery,
and ferment out from within the issues of

FUNCTION AND ENVIRONMENT 211

each maturing life, in passion or apathy, virtue
or vice, social service or crime, health or in-
sanity. For him as for Darwin “the soul
of man is no whit less the offspring of animals
than is his body. Our psychic powers are
new dispensations of theirs. The ascending
series of gradations is no more broken for the
psyche than for the soma.” Following Dar-
win still, his ““method is always and every-
where objective and observational, never
subjective or introspective. ... The true ulti-
mate knowledge of our psyche is the descrip-
tion of all developmental stages from the
amoeba up; and those move most surely among
the altitudes who have most carefully ex-
plored the depths in which the highest human
powers originate. Emotions are best studied
in their outward expressions of gesture, will
is investigated by the study of behaviour,
intelligence by massed instances of sagacity,
and not by analysis under old rubrics.”

With example like this of Darwin’s, and
guidance like this of Stanley WHall’s, no
biological brother need fear to enter the
school of psychology, as we ourselves have
done, albeit also tardily. From its many and
ever-widening outlooks new views appear;
on one side, perhaps, a glimpse of how to
clear up the vagueness of current vitalism,

212 EVOLUTION

and in any case many ways of mellowing the
crudeness of current mechanism.

CHAPTER VII

EVOLUTION THEORIES IN THEIR SOCIAL
ORIGINS AND INTER-ACTIONS

Evolution theories: their history from social side—Limi-
tations yet advantages of social outlooks—From social
progress to naturalist outlook—Science in its relation
to labour—Science in Philosophy, Education and Life
—The natural sciences once more—Summary of pre-
ceding argument—Education through nature-occupa-
tions to vocations—Rustic and urban as contrasted in
thought—Needed renewal of rustic point of view.

In the introduction we saw that the doctrine

of evolution was on one side a generalization

from science after science—from astronomy
and geology, even sooner and more plainly
than from zoology and botany; from philology
and other human sciences also. We saw the
faith in evolution arising, less consciously,
no doubt, but perhaps all the more deeply;
and through the social transformations of its
age. The generation of culminating political
revolution in France, that of the culmination
of the industrial revolution in England, have
thus expressed themselves through Lamarck
and Darwin more clearly than either thinkers

EVOLUTION THEORIES 218

ever dreamed, or than their respective ex-
ponents and disciples have realized.

The wealth of first-hand observation from
which Darwin and his successors generalized
their conviction of “the all-sufficiency of
natural selection ” was thus a less simple and
child-like discovery of Nature than it seemed;
it was a new and modern selection from the
wealth of Nature’s aspects and interests.
For, when all is said and done, “‘ the eye sees
only what it brings with it the power of seeing.”
What are Lamarck’s interpretations of the
effects of use and disuse, his assured insistence
upon the interior freedom of the organism to
realize its inmost capacities, but the new step
in social progress through abandonment of
outworn orders of society, the freedom open-
ing before new ones. “ La carriére ouverte
aux talents” is pure Lamarckism; so again the
splendid over-assurance of the Napoleonic epic,
that “‘ every French soldier carries a marshal’s
baton in his knapsack.”’ But the colder busi-
ness view so characteristic of English thought
came to prevail over such political and mili-
tary exaggerations; the ideals of mechanical
efficiency and of individual and financial
success rising above the ruins of liberal aspira-
tions and of imperial achievements as they
have so often done. Hence a view of evolu-

214 EVOLUTION

tion essentially mechanical, in terms of the
division of labour, the cumulative patenting
and the like, which were gradually evolving
the express locomotives or the manufacturing
plant of Darwin’s day, and now the flying-
machine in ovr own. Hence, too, views essen-
tially competitive and commercial, albeit of
various shadings, from old-fashioned indivi-
dual efficiency to cheaper and cheaper under-
sellings, with advantages here from advertise-
ments more and more brightly and seductively
coloured, there from deceptive imitations more
and more subtly wrought. ‘‘ Competition is
the life of Trade ” : then why not also the
trade of Life? Yet with all this freshness
and vigour of economic application, there
has prevailed in the main, and still prevails,
a naive forgetfulness of the social origins of
these naturalists’ discoveries.

. Similarly in neo-Darwinian times. With
united and real respect for Weismann, for
whose work one of us has once and again
acted as translator and editor, the other yet
ventures to urge one of the very few criticisms
which that wide and fair-minded and subtle
thinker seems never to have considered: the
striking social parallelism of his own theory
of the germ-plasm, of the ovum’s strict in-
heritance, with the thought of contemporary

EVOLUTION THEORIES 215

Germany; with the victories and hegemony of
Prussia, the renewed claims of its aristocracy
also; and, above all, with its doctrine of race,
political and anthropological combined. The
intermediate step between this ruling Prussian
world of action and Weismann’s ascendancy
in speculative biology is indicated by the
widely diffused doctrine of Count Gobineau,
consciously and avowedly bio-social as this
has been. All these movements alike have
now found eloquent, though hardly scientific,
expression in Houston Stewart Chamberlain,
whose contemporary vogue in Germany is
thus earned and explained.

LIMITATIONS YET ADVANTAGES OF SOCIAL
OvuTLooK.—But the reader may ere now be
saying: If this be true, if biological doctrines -
be even half as much projections of their social
age as is here suggested, what becomes of the
independent scientific value they have claimed,
and which we are asked to grant? Is your
science merely a new anthropomorphism ?—
and if so how does it differ from the mytholo-
gical accounts of Nature it claims to displace ?

The answer is not so difficult as it seems,
the result not so unsatisfactory after all.
The independence of the doctrines of any
science from the social life, the prevalent
thought of the generation in which they arise,

216 EVOLUTION

is indeed a fiction, a superstition of the
scientist which we would fain shatter beyond
repair; but the science itself becomes all the
sounder for recognizing its origins and its
resources, its present limitations and its needs
of fresh light from other minds, from different
social moulds. Robinson Crusoe made an
excellent survey of his island, and felt a
legitimate scientific assurance of its thorough-
ness, a corresponding personal pride also;
but when Friday came, bringing with him a
widely different tradition of culture, his fresh
survey not only enriched his master’s at many
a point, but taught him, indeed each of them,
its relativity as well. Here indeed is the
practical criterion of scientific conclusions,
their verifiability by diverse minds. So far
then from sneering at Lamarck as an impas-
sioned son of the revolution, at Darwin as a
shrewd and prosperous modern Englishman,
at Weismann as a German ennobled, and so
on, we begin to see how, just as “it takes
all kinds of people to make a world,” so it
must also to give anything like a full account
of it, to clear these partial accounts up into
a science. A science is one of the most
collective, most historic, of products; and
most social therefore, though the custodians
of its heritage be as yet few.

EVOLUTION THEORIES 217

There is a time for everything, and since
philosophy, or any portion of it worth calling
generalized science is (or at least should be)
the ripened fruit of experience, the retire-
ment of the student and philosopher from the
noise and turmoil, the daily, hourly pressure ~
of the world, is as necessary and as legitimate
& process as is setting apart the milkpan to
let the cream rise. The mistake arises when
we begin to think of this isolation as the sole
essential, and overlook that all the cream we
get comes from the cow, and from such pasture
as we can give her. The qualities and defects
of the retiring biological philosopher thus
become apparent. Take Mr. Spencer for
choice. After an education unusually scien-
tific, an experience unusually practical, in-
cluding participation in the greatest con-
structive activities of his day, both as railway
engineer, as mechanical inventor, and in its
theoretic discussions also, as editor and as
economist, he takes more and more general
views, first as leader-writer, then as essayist,
and thence abstracts himself into his long and
devoted cloistered life as philosopher. But
after all, how little in essential thought does
his reasoned philosophy get beyond its initial
statement in his sporadic essays ?—and how
largely are these, in qualities and in limitations

218 EVOLUTION

alike, the expressions of his boyish and his
youthful education, his professional experi-
ences ?

From Socrat ProGress To NATURALIST.
OutrLoox.—Once more, then, we insist upon
the progress of evolutionary science as from
social progress to its naturalisi application. In
our opening chapter we put this plainly enough,
but as it were once for all; thence passing as
naturalists into the field, and as biologists into
the laboratory and study. Darwin is again the
example of this life-history of the naturalist.
Malthus once grasped and applied, he drew
no more drafts upon political economy, con-
sciously at least; and his many disciples and
continuators have been no more conscious of
their stoutly utilitarian economics than was
M. Jourdain of his prose: though of course
it has been none the less there all the time.
Wallace, indeed, practically alone among
Darwinians, and more divergent and original
than his generous loyalty has ever allowed
him to realize, has kept in touch with the
movement of economic thought, and that in
later and less canonical schools especially; he
has striven to throw light upon other puzzles
and controversies, from political to psycho-
logical, from geographic to religious; but there-
by, despite services to evolutionary biology

EVOLUTION THEORIES 218

second only to Darwin’s own, he failed to widen
the interests of fellow-workers henceforth
specialized, and perhaps rather intensified
their reluctance to venture beyond their im-
mediate problems. They too were doubtless so
far right in this: their re-examination of Nature
in the light of the Darwinian theory has been
a great task. But now on many sides fresh
chapters of evolutionary study are opening,
and there are many workers who feel free,
even constrained, to relate and unify the
phenomena of development of plants and
animals and man, the intricacies of structures
and functions, variations and diseases, amid
which have lain our various individual train-
ings as organic evolutionists, with those of
other evolutionists, not only the cosmic, but
the social. Hence, then, the planning of this
little book—which starting with the social
origins of biological evolution theories, next
naturally gives its main bulk to the biological
theories themselves, but increasingly suggests
the fruitful parallel of organic and social
evolution; and now, as it draws towards
conclusion, it argues with more and more
insistence for the conscious renewal of this,
as a, working partnership henceforward.
SCIENCE IN Its RELatTions TO LaBour.—
Note here another difference between the

220 EVOLUTION

opening treatment of this parallelism and that
with which we now draw to a close. Bio-
logical evolution as projection of a social philo-
sophy, be this conscious or unconscious, and
the resultant renewal of Nature studies as
observant and inductive in the field, are alike
the expression of that wisely passive mood
in which, with naturalist as with poet, “‘ we
see into the life of things.” But man is born
to labour also; his hands have made him wise;
the complex brain not merely or mainly
growing up in vacuo or in abstracto, nor even
in encyclopedia, as one school of educationists
after another has falsely thought and wrongly
applied, but as we now begin to see and to
apply, in intimate interaction also with the
skilful and strenuous hand. Science, no less
than fine art, is essentially of the working class.
Like art it is craft-experience, craft-skill, craft-
initiative, forthe scientist more reflective, as for
the artist more impassioned. Science is always
observing, inquiring—blundering therefore
also—with the prentice; is in fact a perpetual
apprentice; yet skilled, and that a degree
beyond the customary journeyman—specu-
lative, experimental, inventive, with the best.
Furthermore, Science is experienced, critical,
comprehensive, with the master, and hence of
such service to his large undertakings. True,

EVOLUTION THEORIES 221

the working world around us, bound all day
to the wheel of labour, is hypnotized more even
than is the middle class by nominal wages in
money instead of real wages in life; more even
in its brief leisure than the upper class by fair
abstractions and fine words; and so it has
lost sight of its outstanding artist leaders, its
pioneering scientist ones, as they of each
other. Hence as yet when new leaders emerge
amid its ranks it is as amateur barristers, or
amateur financiers, for the most part. Still,
the reunion of arts and sciences with labour
*‘ is comin’ yet for a’ that,” and with it a new
age of social evolution, and of corresponding
impulse to evolution theory also.

SCIENCE IN PHILOSOPHY, EDUCATION, AND
Lirz.—Of this incipient renewal of philosophy
with social life the discussion of pragmatism
is an example; but for our purpose its change
of stress, from passive knowledges to active
purposes, is more obviously expressed in the
coming in of manual training to-day after
that of scientific instruction yesterday. To-
morrow we shall realize that more of free and
creative art is necded to redeem industry from
its mammonism and its drudgery, as science
from formalism and cram; thereafter, with
the unison of all three will come education
indeed : artistic, scientific and practical; heart,

222 EVOLUTION

head, and hand; and each calling out the
others to fuller expression and development.

Concretely, how can this dream of individual
development so important for the progress of
science, the reading of evolution, be actually
applied and brought about? So far as the
sciences are concerned—and these are com-
monly esteemed the most difficult—the prin-
ciple of its applications are clear. While the
services of each science to practical life are
constantly insisted on, and in no danger of
being overlooked, we far more often and readily
forget the rise of each science from practical
life. But the historic beginnings of geometry
with measurement are again in progress in
the schools. Those of astronomy with naviga-
tion have long been well taught to the sailor
youth, and now the boy scout is learning, like
his pastoral ancestors, to find his time by
the sun, his way by the stars. Nor is this a
matter of elementary education merely; here
lies the main progress of research also, that
higher education of the individual and the
race together. Thus the problems of daily
life, the emergencies of practice, called out
the highest powers and achievements, from
Archimedes of old to Kelvin yesterday.

For fuller illustration—whether we state
on principle more abstractly (as the rise of

EVOLUTION THEORIES 223

science from practice)—or more concretely
(experimental science as proletarian experience
and initiative), we cannot do better than
bring to these tests some of these great leaders
of science, whom the uninitiated still practi-
cally think of as magicians and wizards, much
as they did of their predecessors of old. Take,
then, Kelvin and Lister. Leaving aside the
too common London populace view, to whom
these names are impressive merely as Lords,
albeit a little lower than the brewers; or the
more educated London view, which would ap-
preciate them as successive Presidents of the
Royal Society, it is plain that a more real
and biographic understanding of the one is as
the farthest ranging of the mathematical and
the experimental physicists, both pure and
applied, and of the other as the renewer of
modern surgery. Biographically, we under-
stand Kelvin better in his lifelong environ-
ment of Glasgow; but only fully as we see its
significance, for one thing as the great fiord
of the iron shipbuilders, with their consequent
dangers of deranged compass and the like,
whence a well-known example of Kelvin’s
experimental solutions. Here, too, arose
James Watt, with his Promethean control of
new energies; and here fitly also in turn
Kelvin to control the yet subtler and more

224 EVOLUTION

potent spark of electricity with inventions,
each a literal masterpiece of craft subtlety
and of manual skill. Kelvin, whom in
illustrious old age the world delighted to
honour, was thus as truly the master-smith of
Glasgow as had been Watt before him; so
the spacious physical laboratories of every
university in the world to-day are still above
all the local extensions of William Thomson’s
cellar-workshop.

So Lord Lister is not to be understood
primarily even as surgeon-in-chief: his place
in history, immortal though it be, is also
humble, humbler even than that of the
plebeian branch of the profession, the barber’s.
For he with his antiseptic surgery is “ the
shepherd with his tarbox by his side’’; more
simply still, since full shepherd-craft is far
beyond his ken, he is the “tar-boy,” who
waits upon the shepherd, ready to put on his
dab of antiseptic wherever needed. So Pas-
teur was not essentially a magnate of the
Legion of Honour, the member of two Aca-
demies at home, and of all abroad; not even
primarily the great chemist. He was a
tanner’s son, born and bred, that is, amid the
greatest and oldest of antiseptic processes, and
developing and applying it all his life. More
generally, in character and experience he was

EVOLUTION THEORIES 225

a Jura peasant, with all the French peasant’s
tenacious and tireless industry, his manifold
minute economies. One rare advantage he
had, and this it was which made him the
world’s master-peasant—the daintiest ultra-
feminine eye for dirt, and as its direct and
woman-like application a super-housewifely
passion for cleaning. How, out of these
simple conditions, these homely and humble
antecedents, came discoveries and applications
revolutionizing industries, agriculture, medi-
cine, and through Lister surgery (for Lister
is Pasteur’s tar-boy), we have tried to tell
elsewhere.

So, again, the botanist is in the university
as the representative of the old herbalist, the
wise woman gathering her simples. Linnzeus,
with his world-museum, his proudly entitled
**System of Nature,” albeit traveller and
scholar, is essentially and traditionally a head-
pharmacist, the most orderly on record of that
necessarily tidiest and most careful of guilds.
Jussieu, of the natural system which replaced
the pharmacists’ inevitably more artificial
one, was the king’s gardener, the man of
living flowers, charged to keep the queen
and her ladies in bouquets, and so getting a
free hand to vary them, and an intelligent
and questioning audience sometimes to explain

H

226 EVOLUTION

them to, whereby indeed botany came into
fashion. Of botany there are always these
two schools—the pharmacist’s and the gar-
dener’s; so its professors belong essentially
to one or other, sometimes partly to both, but
never thoroughly: that is too much to ask.
The zoologists then? ‘These are hunters;
first out after big game with its dangers, its
trophies; after birds too, and their plumage.
Sometimes there comes to one the vision of
St. Hubert, and then he lays aside his gun, and
takes up his notebook or his camera. Darwin
was one of these from his Beagle days
at any rate; but before that, he was plainly
of the hunter type—in fact, a born truant,
the stuff true poachers are made of.

Other naturalist-hunters come down to
smaller and smaller deer, next to their fleas
and midges, and now to-day are hunting out
the parasites within these, and to some pur-
pose. Other naturalists, again, are fishermen,
increasingly expert, their huts and pools grow-
ing into zoological stations, their nets searching
the sea from its surface-plankton to abyssal
dredgings; and these from Arctic to Antarctic.
Plainly then, the natural sciences grow up along
with practical life and ever learn from it anew.

SUMMARY OF PRECEDING ARGUMENT.—
Collecting now all the threads of this long

EVOLUTION THEORIES 227

discussion towards a fuller grasp of the studies
of evolution, the result is plain enough. Since
we cannot but project our human thought,
our social progress, upon Nature, let this be
more than that of past or passing phases and
groups, but of the incipient social order as
well, of Society at its very best, since here
is the growing-point of our own evolution.
Yet we must test all anew in the field; for by
our fresh glimpse of theoretic light, the whole
world must be reviewed afresh, and our new
light ray tested in its turn for all it may be
worth, as well for all it can reveal. The true
Darwinian is thus not he who longest swears
by the word of the master, and stretches
some classic adaptations, say of flower and
insect, towards its breaking point, but he
who with a social philosophy advanced beyond
that of Darwin’s teacher, Malthus, goes forth
anew into the field. For one this bettered
social theory may be Marx’s, for another
Ruskin’s, for another Gobineau’s, Nietzsche’s,
and so on: each is actually yielding its bio-
logical result. Most obviously perhaps, Gal-
ton’s, since his studies have been again of the
population question, but in what new light !
And with what fresh results and impulses:
here with biometrician disciples, there with

no less active Mendelian antagonists !
H2

228 EVOLUTION

Yet, as we have seen, it is not enough to
be students even of Man and Nature; we must
also take our part in the world of action, if we
would understand the action of life. The
scientist has affirmed this intensely in his
insistence on field work, on museum work,
on laboratory work: but still too narrowly;
even with zoological stations and experi-
mental institutes thrown in. Here no pre-
paration can be too full, too varied in its
practicality.

Explore our region here, and any other you
may have the good fortune to reach, fully,
thoroughly, repeatedly, from hill-top to sea-
bottom and back again. Realize your environ-
ment, your region through activity also:
and this not only as an excursion-field, a
playing-field, from ski to dive, it may be as
hunting-field in moderate measure, but as
work-field also, and above all. Go down into
mine and quarry; get some turn at hewing
coal, at dressing stone. The anvil, the joiner’s
shop, the carver’s or other studio are all ex-
cellent; already coming into use for afternoons
at any rate of school winters in town: in
summers be out in Nature; see and touch
Nature alive. Go out then with the herring-
fleet for one summer’s holiday at least:
work in the fields a spring, a harvest, and tend

EVOLUTION THEORIES 229

the horse, as well as hold the plough. Work
too in the garden, and this for kitchen as well as
for drawing-room; yet also for general beauty
as well as detailed use. Above all, and not
only for culture’s sake but character’s, get
out with the shepherds, till you know not
oriy something of their work, but of them-
selves. In each craft, at each level, learn not
only something of the immediate work, but
of its workers, and of their ideal aims, their
culture-spirit, for there is no true work and no
true worker without this : then you can choose
your occupation, or rather it will choose you,
and at such level as you may be fit to rise
to, here of its constructive toil and_ skill,
there of its song or story, its science or its
art.

Rustic AND URBAN AS CONTRASTED IN
Txoucut.—Of all the many occupational ex-
periences there are but two main types, those
concerned with organic and with physical
nature, the rustic and the urban, in a word, the
vital and the mechanical. Here is the main
contrast of town and country, in their charac-
teristic experiences, their essential occupations;
and the resultant interpretative evolutionary
standpoints which we are seeking will be
essentially these two, will be characterized
by familiarity with the processes of mechanism

230 EVOLUTION

and of growth respectively. The town in-
tellect is of course the swifter, the clearer,
more precise and definite, the more-assertive
and authoritative accordingly; hence its
characteristic contributions to knowledge and
to social progress, and the satisfaction with
which it proclaims these, and with which it
applies these, doubting nothing, to the educa-
tion of the rustic world, which undoubtedly
comes forward accordingly—but into town.
That surviving slow, heavy-footed peasant,
behind his plough, or gazing over the fence
at his growing corn—what blank stupidity !
That shepherd striding back from the snow-
drift with the lamb within his plaid—what
pretty sentiment! That is what the mechani-
cals and moneyers and paperists of cities see
in these silent servitors of Life.

NEEDED RENEWAL OF Rustic POINT OF
View.—Suppose, however, that they one day
become articulate; that Pasteur is not the
last thinking peasant, but an initiative one, a
forerunner, already followed by the breeders,
cultivators, eugenists of previous pages.
With such contributions to the work of
experimental evolution will there not also be
forthcoming corresponding contributions to
its theory? This will be neither in terms of
the mere mechano-morphism of the physicists

EVOLUTION THEORIES 231

and chemists, nor of the puzzled mysticism
of vitalist philosophers as yet befogged by
their urban environments or bewildered by
reaction from it. It will be in terms of
biology proper, and its processes of nutrition
and reproduction, of metabolism and growth.
Each science is but an aspect of the whole, a
pictured facet of Nature’s unity, but it has
its own categories, its own values. No one
of the main sciences, be they the objective—
physical, biological, social; or the subjective
—ethic, psychologic, zsthetic—is intelligibly
reducible into the concepts of any other,
those of mechanics, physics, chemistry, de-
spite their long exaggerated pretensions, as
little as any—(though their parallelisms may
and should be sought; that is a practicable
and legitimate inquiry). It tells us nothing
of the esthetic value of scarlet blossom, of
golden sunset, of summer green, that these
have such and such relations of wave-length,
interesting in the physical laboratory though
that be. By all means let us correlate brain
growth with mind; but the life of intelli-
gence, idealism, imagination, would have
none the less its psychological independence
were the chemical formule of every brain
metabolism published to-morrow.

So then for biology. Its theory of life, of

282 EVOLUTION

evolution must be in its own terms, of
function and form, and free therefore from
absorption into the lower physical order, as
from exaggeration into the higher ethical and
political one. The latter mode of state-
ment is the transcendentalist’s old-fashioned
fable ; the former is a materialistic fable.
But to correlate and parallelize the biological
with the physical order, as with the social,
whenever we can: that is a different matter.

Above all, however, let us as naturalists
see that we grasp not only the mechanical
and urban point of view but the rustic and
physiological one.

CHAPTER VIilI

THE EVOLUTION PROCESS ONCE MORE
REINTERPRETED

The evolution process again reinterpreted—Antithesis
of vegetation and reproduction; applications in the
plant world—Justification from rustic experience—
Evolution in the animal kingdom—Summary and
conclusions.

THOUGH we must leave that rich mastery

of the evolution secret we once hoped for to

the successors we would fain send out so much
better equipped, can we not meantime be
going at least a step or two farther before we

THE EVOLUTION PROCESS 2383

leave life’s wonder-feast—readers and writers
alike ? Here, then, in preceding chapters
have been offered summaries and interpreta-
tions not a few: some are master-keys, tested
by long and world-wide use, others awaiting
trial and verification; but most, surely, of
some applicability. In conclusion, and not
as dogmatically pressed, but suggestively
offered, the reader may be interested in some
brief outlines of a different reinterpretation of
the evolution process—one not as yet fully
published, still less seriously criticized by
other biologists; one suggested at the close
of our “‘ Evolution of Sex,” outlined in scattered
papers and lecture syllabuses, and with its
beginnings compressed into a too dry abstract
at the close of the old “ Britannica” article
** Variation and Selection,’’ many years ago.
Let us start from the acceptedly known,
from Darwin’s natural selection, and this of
‘‘ indefinite ” variations, and express the pro-
blem before us in the words of Weismann : “‘ We
certainly cannot remain at the purely empiri-
cal conception of variability and heredity as
laid down by Darwin in his admirable work.
In the first enthusiasm over the newly dis-
covered principle of selection, the one factor
of transformation contained in this principle
has been unduly pushed into the background

234 EVOLUTION

to make way for the other more apparent and
better known factors. The first indispensable
factor, and perhaps the most important in any
case, in every transformation is the physical
nature of the organism itself.”

This inquiry into the organismal springs
of variation must lead us far. For Weismann
these have led especially into his subtle
studies of the germ-plasm; but obviously
also they involve a fresh survey of the leading
types of variation as we see them developed
by plant and animal forms. Naturalists are
no longer so much setting out from the analogy
of human selection upon domestic animals and
cultivated plants, and reasoning from the
accumulation of their varietal differences up
to what seem to correspond to species or some-
times even genera in Nature, and thence
arguing on Lyell’s uniformitarian principle,
for the analogous cumulative natural selection
through geological time, of the characters of
larger groups, genera, orders, classes and the
rest. Wehave simply now to group our types
of variation, and to consider them from the
standpoint of general physiology as far as we
know it, and independently of these fascinat-
ing hypotheses of agriculture and geology.

VEGETATION AND REPRODUCTION, AND
THEIR ANTITHESIS.—The largest view of physi-

THE EVOLUTION PROCESS 235

ology, one peculiarly obvious to the botanist,
from the vivid distinctness of flowers and foliage,
but denied bynone for animals and man as well,
is that which treats the functions of living
beings as of two main kinds; grouping on the
one side respiration, irritability, and all the
other activities of the individual in its self-
maintaining life, and then setting over against
the whole of these the great function of the
species-maintaining life, reproduction. Weis-
mann’s main work has been to emphasize this
distinction, especially from the side of the
intimate morphology of the germ-cells; while
some of the best chapters of Spencer’s “ Prin-
ciples of Biology ” are those in which, after
pointing out its intelligibility in terms of the
principle of conservation of energy, he elabor-
ates the antithesis of nutrition and reproduc-
tion by reference to many plant and animal
forms. Yet though the principle is one
familiar since the dawn of physiology, its
applications are still far from exhausted.
** While philosophers are disputing over the
government of the world, hunger and love are
performing the task,” says Schiller; and our
‘* Evolution of Sex ” is essentially an elabora-
tion of one great aspect of this theme.
APPLICATIONS TOWARDS INTERPRETATION
or THE PLant Wortp.—Let us begin with

236 EVOLUTION

the origin of the flower, which all agree in
regarding as a shoot modified for reproduction.
But it is also shortened, as compared with
a vegetative shoot; then why? By natural
selection from two other alternative variations?
—one like the vegetative shoot, and the other
lengthened farther still? These are imagin-
able as forms; there is no morphological
absurdity about them: yet we may be fairly
sure they never existed at all, and so have
not been selected. How so? They are
excluded by the physiological explanation
of inevitable shortening; since the organic
expenses of the onset of the reproductive
function necessarily checks the vegetative
ones.

Similarly for flower groupings, the “ forms
of inflorescence.’”’ The simplest form is the
long flowery stem, each flower with its own
stalk, like the foxglove spire; but such fine
‘““racemes”’? are comparatively uncommon.
Often the flower-stalks are arrested, and we
have the “ spike,” as in the mullein, golden rod;
or again it may be the main stem which stops
short, leaving the minor stalks to grow and
separate the flowers, as in the “ umbel ” of
cowslip (and even primrose), of ivy and of the
parsley and hemlock tribe without number.
But in one great order, and that significantly

THE EVOLUTION PROCESS 287

one of the most successful in the whole world-
flora, the daisy and dandelion order, the axis
of inflorescence is arrested in growth until it
is a flat disk, and the flower stems have
disappeared altogether, so that we have the
crowded ‘‘ head” of flowers, their own indi-
vidual development greatly reduced, so charac-
teristic of the Composites. This principle of
flower-heading is constant in not a few orders
otherwise widely distinct, like willows and
plantains; and appears here and there among
other orders, e.g. in sea-pinks, and even among
labiates and roseworts. It is noticeable that
such forms, like the Composites themselves,
are commonly vigorous and hardy growers, as
may reasonably happen, the saving through
subordination of the reproductive shoots
being applicable to help on the vegetative
ones. In the figs, a peculiarly vigorous and
varied tribe, the arrest of the inflorescence
goes so far as to make this like an inturned
glove-finger, a hollow pouch instead of the
usual ascending cone, and with the tiny
florets inside accordingly.

Now, returning to the individual flower,
it is an interesting fact that this process of
reduction of the great axis of inflorescence
from shoot to head, and thence to fig, is
repeated on that small axis of the flower,

238 EVOLUTICN

which the beginner in flower dissection is apt
to forget altogether. This, however, may be
easily made out as a distinct case, in the butter-
cup, or best of all, in the magnolia, and the
sepals and petals, the stamens and carpels,
may all be seen to arise upon this in ascending
order, like the young crowded leaves of a
vegetative bud. This simple (“‘ hypogynous’’)
arrangement, however, goes farther in the
(‘‘ perigynous ””) strawberry, where, instead
of a short conical shoot, we have now the axis
disk-shaped, recalling the composite head;
while even the hollow fig finds its parallel
in the many flowers which, like rose or
daffodil, have become “ epigynous,”’ 7. e. with
their ovaries, now sunk at the bottom of a cup,
the arrested and overgrown apex. Passing
now to forms so utterly distinct as the fungi,
we find the same process repeating itself, the
essential reproductive organs sinking from
cone to disk, and thence into cup or pouch,
like fig and rose, indeed closing up completely.

Now, the farther we go in our studies of
flower anatomy, the more we find of this
subordination of the vegetative life by the
reproductive ; witness the reduction of the
number of petals, stamens and carpels from
indefinite to few. See, however, what all
this amounts to. All these changes and

THE EVOLUTION PROCESS 239

others, in fact the most important of floral
variations, the big lifts distinctive for the
evolution of orders, are thus seen no longer
as indefinite, and hence dependent on external
selection for their guidance; but, on the con-
trary, as parallel and definite, since determined
through the continued checking of the vegeta-
tive process by the reproductive, and thus
pressed along parallel and definite grooves of
progressive change. But if this be so, the
importance we have been taught by Darwin
to assign to natural selection becomes greatly
changed—from selecting and accumulating
supposed indefinite variations, to that mainly
of retarding definite ones, after their maximum
utility has been independently reached !

The same simple conception unlocks innu-
merable problems of floral morphology, large
and small alike, from the inevitable develop-
ment of angiosperm from gymnosperm (by
the continuous subordination in vegetative
development of the reproductive carpellary
leaf) to the origin of many of the refined
minor “ adaptations ”’ of the dominant school.
Adaptation to insects, to wind also, thus falls
from a primary to at most a very second-
ary place as a factor in the evolution of
flowers; for the characteristics usually ascribed
to the selective action of wind and insects

240 EVOLUTION

constantly appear at the extremes of the
relatively more vegetative and more floral
series which are discernible more or less in
every alliance, great and small. Witness
among the vast group of monocotyledons,
the extremes of the grasses and the orchids
respectively; or in a_ single genus, say
Senecio, its weedy groundsels and gorgeous
cinerarias.

JUSTIFICATION OF THE PRESENT THEORY
IN Rustic Exprrtence.—Now this whole
theoretic reinterpretation: whence is it?
Again from experience. With the resources
of a great garden, at any rate with a
gardener to do all the work for us, we come
out at leisure, and notice the flowers, here
visited by insects, and there swaying in the
wind, and fancy their forms thus fashioned,
adapted, selected from without: our town
friends are readily convinced of this, and their
assent strengthens our convictions and stimu-
lates our researches anew. But when we
set about making a garden for ourselves, and
labour with our own hands, new perspectives
open, fresh points of view appear, above all
that of growth; and this—even at its very
simplest, the wide growth-contrast of lilies
and rushes, of weeds and flowers—reinterprets
the differences we formerly ascribed to form

THE EVOLUTION PROCESS 241

—as scientists we thought, as leisure class we
now see; and essentially urban at that. For
while in our town herbaria we distinguish
grasses and orchids essentially by their post-
mortem structure, the gardener is the fuller
scientist, the true physiologist, knowing their
differences as lives; the grass so vegetative
that cattle and farm and city all live upon
its surplus, the orchids so splendidly floral that
we may easily spend upon their culture more
than our grass-field can earn.

If this rustic point of view be seized, and
the urban and mechanical one correspondingly
subordinated, the present theory will work
itself out just as fully and freshly as did the
selectionist game of thought: if not, it
remains useless to argue for it. The eye sees
only what it brings the means of seeing.

RE-INTERPRETATION OF THE ANIMAL KING-
pom.—Instead then of opening new botanical
sections, of which each would really require
a chapter, sometimes a whole volume, now
dealing with the interpretations of flowers
and of fruits, and again with the great pecu-
liarities of habit—evergreens, thorny plants,
climbers and so on, let us rather ask: Can
any such physiological interpretations be
applied to a survey of the animal kingdom?
Its problems are obviously far more intricate

242 EVOLUTION

and varied: yet the result is scarcely less
definite or comprehensive. In the outline
of our restatement of the cell-theory as a
‘theory of the cell cycle” (Chapter IIT) we
have already interpreted such main forms of
Protozoa as the rhizopods, the gregarines, the
infusors, not from without, as the empirically
selected products of spontaneous variations
among indefinite possibilities, but from within,
as simply the preponderatingly ameeboid,
resting, and motile phases of the cell-cycle,
three forms determined by the properties of
protoplasm itself.

This conception of life-histories, as physio-
logical and not merely structural, rationalizes
our animal no less than our vegetable classi-
fications. Thus the greatest of all steps in
morphological progress, that from the uni-
cellular Protozoa to the multicellular Metazoa,
is plainly not due to the external selection
of the more individuated and highly adapted
Protozoan species, but is understood from
within, as the union of relatively embryonic
and unindividuated cells into an aggregate
in which each becomes diminishingly com-
petitive as regards its fellows, and increasingly
subordinated to the social whole; while within
the body thus developed, a series of cells
remains relatively undifferentiated as the

THE EVOLUTION PROCESS 248

essential sex organ, female or male (prepon-
deratingly anabolic or katabolic) as the case
may be. And as the natural variations and
divergencies of plants may be most con-
veniently summed in terms of vegetative and
fioral preponderance respectively, so those of
animals similarly fall into the broadly recog-
nizable contrast of passive and active, seden-
tary and errant, perpetually renewing itself
in every group. Hence the contrast of fixed
anemone or coral and swimming jelly-fish or
ctenophore, of stony tube-worms and naked
creeping or swimming worms, or the contrast,
yet series, of fixed crinoid and boring urchin
with creeping star-fish and active sand-star;
or again of passive barnacle and active shrimp,
of sluggish beetle and nimble gnat; or again
within the same orders, as moth and butterfly
—always the same dichotomy of passive and
active. Here essentially lies the secret of the
divergence between ascidian and vertebrate,
to take a great difference, or that between
toad and frog for a small one; or again this
is the main contrast between reptile and bird,
Diplodocus and swallow. This lies within the
perpetual redifferentiation of these, witness,
among reptiles, the sluggish and often colossal
tortoises, yet the active and supple snakes;
and these (of course) again differentiating

244 EVOLUTION

anew, here the huge and passive python, and
there the small and nimble fer de lance. | Once
more, for birds, see the contrast of the massive
pedestrian dodo with his pigeon cousins; or
of giant chickens like the ostrich and emu
tribes with exquisite but tiny adults, say the
hummingbirds. The kinship of elephant and
coney, the contrast of stony glyptodon and
gigantic sloth with nimble lemur and agile
monkey, and again of bear and dog, of dog
and cat, of sheep and goat, are thus re-inter-
preted together, no longer as for the early
Darwinians as so many machine-like com-
binations of innumerable indefinite variations
externally selected from among yet more
innumerable ones, nor even among a more
limited number of ancestral possibilities, but
as so many forms thrown from the rhythmic
oscillation of the loom of life. Each of
these types or species, with its exquisite
intricacy of detail and individuality of pat-
tern, its marvellous correlation of organs, is
thus a new unity created from within by its
own interior play and balance of vegetative
and reproductive forces, its inner predomin-
ances here of anabolisms and there of katabol-
isms. Growth and arrest, giant and dwarf,
rest and movement, sleep and waking, even
female and male are contrasts all physio-

THE EVOLUTION PROCESS 245

logicaliy akin; and this single and simple
rhythm of metabolisms, of passivities and
activities goes on into compound and re-
compounding rhythms, like the figures of the
pendulograph. The forms of life are thus
distinct and definite, because harmoniously
unified. They have a certain stability, great
or small, yet they are anew transformable,
like musical variations, like singing flames.
Thus from within are spun and woven and
shaped the manifold garments of Life, always
simple, though ever more and more Protean.
Our clue to the secret of variational evolution
thus holds good, is one and the same from
the ancient contrast of plant and animal up
through the great lifts of evolution, and down
through its ever recurrent falls; and if it
applies equally to the origin of classes and
orders, of genera and of species, why not also
to the varieties and mutations which natural-
ists are discussing, for the most part too
externally, at the present day?

SUMMARY AND ConcLusiIons.—As in plants
the species-maintaining functions prepon-
derate over the individual ones, so that
from annual to agave the plant must flower
although it die, so the same preponderance
appears in animals. The “ self-interest” in
which the utilitarian economists found the

246 EVOLUTION

all-sufficient spring of action, and which
naturalists too long and too uncritically
adopted from these (whence MHuxley’s
“‘ gladiator’s show ’’), turns out to be en-
lightened by family interest, species interest,
however sub-conscious. The _ traditional
primary insistence upon the individual com-
petition for food, and the very subordinate
and tardy recognition of the importance of
sexual and social co-operation, are also trace-
able to a confusion of thought—that of put-
ting the nutritive factor “in the first place ”
because it precedes the reproductive in
time; whereas the organism enters upon re-
production, and so cedes the preponderance,
“the first place,” to the species-regarding
functions. That increase of the reproductive
sacrifice which first makes the mammal, and
then marks each of its distinctive uplifts of
further progress (from monotreme to mar-
supial, and thence to placental), that increase
of parental care, that frequent appearance
of sociality and co-operation which, even in
its rudest forms, so surely secures the success
of the species attaining it, be it mammal or
bird, insect or even worm—all these survivals
of the truly fittest, through love and sacrifice,
sociability and co-operation simple to complex
—need far other prominence than they can

THE EVOLUTION PROCESS 247

possibly receive even by some mildewing
attenuation of the classic economic hypothesis
of the progress of the species essentially
through the internecine struggle among its
individuals at the margin of subsistence.

Our theory thus furnishes a re-interpreta-
tion of the forms attained by plants and
animals comparable to that afforded by the
received hypothesis (and, if space allowed,
traceable into no less refinement of detail),
yet with an essentially allied view of the
process and factors of organic evolution as a
whole. Most briefly stated, the view of evo-
lution thus reached is that of definite varia-
tion: its branchings essentially dichotomous
rather than indefinite, with progress essen-
tially through the subordination of individual
struggle and development to species-maintain-
ing ends. The ideal of evolution is thus no
gladiator’s show, but an Eden; and though
competition can never be wholly eliminated—
the line of progress is thus no straight line
but at most an asymptote—it is much for our
pure natural history to see no longer struggle,
but love as “ creation’s final law.”

Natural selection remains still a vera causa
in the origin of species; but the function
ascribed to it is practically reversed. It
exchanges its former supremacy as_ the

248 EVOLUTION

supposed sole determinant among practically
indefinite possibilities of structure and func-
tion, for the more modest position of simply
accelerating, retarding or terminating the
process of otherwise determined change. It
furnishes the brake rather than the steam or
the rails for the journey of life; or in better
metaphor, instead of guiding the ramifications
of the tree of life, it would, in Mivart’s excel-
lent phrase, do little more than apply the
pruning-knife to them. In other words, its
functions are mainly those of the third Fate,
not the first; of Siva, not of Brahma.

BIBLIOGRAPHY

Tuis list of books has been made longer than in most of
the volumes of the series, and for three reasons. (1) The
scientific study of organic evolution is still very young. There
are Imany uncertainties, there is rapid progress along diverse
lines, there are not a few moot and controversial points. We
wish to recognize this by giving a representative set of refer-
ences, indicative of various schools of evolutionists. (2) We
have met, personally and in correspondence, a large number
of able-minded workers—face to face with evolution problems,
¢.g. as breeders or as gardeners, as medical practitioners or
travellers—who had thought long, and sometimes carefully,
over particular sets of facts, but remained entirely unaware
that these had been threshed out, not once or twice, but
many times over. Not that this refuses value to any new
observation or thought, but it suggests that some literary
research may be reasonably expected from those who have
reached what they feel sure is an upsetting conclusion. We
hope that this little book and this list will facilitate that
research. (3) The problem of Becoming is not particular to
any one science. It is social as well as cosmic and organic.
Therefore in our list we have not forgotten that Darwinism
touches the Humanities.

* Those marked with one asterisk may be the best books
for a student to begin with. But the best beginning is
always where the "pares tendril fixes.

** Those marked with two asterisks record important post-
Darwinian investigations.

It is too difficult to affix marks to suggestive thoughts—
shall we say of Bergson, for instance—which may turn out to
be of much more ‘value than many concrete studies. The
idea of confining ‘‘ research ” to the objective is grotesque.

*** Those marked with three asterisks are ‘‘ slabatna a“

Bartzy, L. H.—‘‘ Plant-breeding.” 3rd Edition, 1904. [A
valuable and practical study of variation and selection
in cultivated plants.] See also ‘‘The Survival of the
Unlike.” 1896.

249

250 BIBLIOGRAPHY

BaLpwin, J. Marx.—*‘ Development and Evolution.” 1902.
{Expounds the author’s theory of the indirect evolu-
tionary importance of modifications.] See also ‘‘ Darwin
and the Humanities.” 1909.

**BatTrson, W.—‘‘ Materials for the Study of Variation.”
1894. [A remarkable collection of data relating to certain
kinds of variation, especially important in its evidence
of discontinuous variation ; a book to consult and to
reckon with, rather than to read, but with a stimulating
introduction. ]

—— ‘*The Methods and Scope of Genetics.” 1908. [An
illuminating introductory lecture, suggesting to an edu-
cated reader something of the import and the fascination
of Mendelian experiments, by which the author has
achieved much. }

**____. ** Mendel’s Principles of Heredity.” 1909. [The most
important statement of what has been achieved by the
experimental study of genetics. ]

Brreson, Henri.—‘‘ Creative Evolution.” 1911. Translation
of ‘‘L’Evolution créatrice.” 1907. [One of the most
profound and original contributions to the philosophical
consideration of the theory of evolution.]

BuTLER, SAMUEL.—‘‘ Evolution: Old and New.” 2nd Edition,
1882. [A keen-witted criticism of orthodox Darwinism. ]
See also ‘‘ Life and Habit.” 1878. [Strong statement
of Lamarckian views.] ‘‘ Luck or Cunning.” 1887.

*CLopp, E.—‘‘ Story of Creation, a plain account of Evolution.”
1888. [A useful introduction. ]

-—— ‘‘Pioneers of Evolution.” 1897. [A very interesting
historical sketch.]

Coz, O. O.—‘‘ Nature versus Natural Selection.” [Extreme
position, denying the efficacy of Natural Selection.]

Conn, H. W.—‘‘ Method of Evolution.” 1900.

Corg, E. D.—‘‘ The Primary Factors of Organic Evolution.”
1896. [Strong exposition of Lamarckian and bathmist
position.] See also ‘‘ The Origin of the Fittest.” 1887.

**OurnoT, L.—‘‘La Genése des espéces animales.” 1911.
[A masterly book, giving a fresh and careful account of
the present state of knowledge in regard to the origin
of animal species. }

***Darwin, CHARLES.—‘‘ Origin of Species” (1859); ‘* Varia-
tion of Animals and Plants under Domestication ”
(1868); ‘‘Descent of Man” (1871).

Davenport, 0. B,—‘‘Experimental Morphology.” 1897. [A

BIBLIOGRAPHY 251

valuable uncompleted treatise on the plasticity and
modifiability ef the organism.]

Davenport C. B.—‘‘ Statistical Methods in the Study of
Variation.” 2nd Edition, 1904. [A useful introduction
to biometrics. ]

**____ ** Inheritance in Poultry.” 1906. [A fine series of
experiments in breeding. ]

**DeLacE, Yves.—‘‘ L’Hérédité et les ds problémes de la
biologie générale.” 1895; 2nd Edition, 1902. [A great
book, discussing with scholarship and impartiality the
chief problems of biology ; Lamarckian on the whole
and against Weismann; with a detailed bibliography. ]
See also an excellent short book by Delage and Goldsmi t,
**Les Théories de l’Evolution.” 1909.

DeptretT, C.—The Transformations of the Animal World.”
1909. [A useful concrete study of the actual history of
Lovet iene eprint

*Doncaster, L.—‘‘ Heredity in the light of recent Research.”
1910. [A pithy and clear introduction.]

Drizscu, Hans.—‘‘ Science and Philosophy of the Organism.”
Gifford Lectures in the University of Aberdeen. 2 vols.,
1908. [A deep and original vindication of vitalism, diffi-
cult for most readers; a fine gymnasium for intellectual
athletes. ]

Ermer, G. H. To.—‘‘ Organic Evolution.” 1890. [Lamarckian
and Goethian, with a theory of orthogenesis, or progres-
sive variation along a definite line. ]

**Ewart, J. Cossar.—‘‘ Penycuik Experiments.” 1899, [An
account of important breeding experiments bearing on
hybridization, reversion, variation, etc. ]

‘* Fifty Years of Darwinism: Modern Aspects of Evolution.”

‘ Centennial addresses in honour of Charles Darwin before
the American Association for the Advancement of Science.
1909. [An exceedingly interesting and valuable series of
lectures on Darwinism, by numerous authorities. ]

***GaLTon, FRaNcis.—‘‘ Natural Inheritance.” 1889. [A
classic book, applying statistical methods to the study
of inheritance, and expounding important generalizations,
such as Filial Regression. }

GEppEs, Patrick.—‘‘ Variation and Selection” in “ Encyclo-
pedia Britannica,” 9th Edition. ‘‘ Darwinian Theory,”
**Evolution,” in ‘‘Chambers’s Encyclopedia,” ‘‘Ohapters
in Modern Botany.” 1893.

Grposs, P., and THomson, J. ArTHUR.—‘‘ The Evolution of

252 BIBLIOGRAPHY

Sex.” 1889. Revised Edition, 1901. [A disecuasion
of sexual selection, the reproductive factor in evolution,
the physiological interpretation of sex, and so forth.
The general thesis is that maleness and femaleness are
expressions of alternatives in the regulated rhythm of
metabolism. |

Groos, K.—‘‘ The Play of Animals.” Translation, 1900. [A
very suggestive book, a proof of the biological importance
of play, with an important contribution to the theory of
sexual selection. ]

Gu1ick, J. T.—‘‘ Evolution, Racial and Habitudinal.” 1905.
[Elaborate discussion of isolation as a factor in evolution. ]

***H AECKEL, Ernst.—‘‘Generelle Morphologie.” 2 vols., 1866.
[A classic work, to be placed beside Spencer’s ‘‘ Principles
of Biology.” It is now out of print, but part of it has
been recently re-issued.]

—— ‘‘Natural History of Creation.” English translation,
1870. [A picturesque book that has passed through
many editions. The early chapters give a vivid account
of the rise of the evolution theory. The statement of
**the evidences” had a deserved success in vindicating
the validity of the evolution formula. ]

*Heapiey, F. W.—‘‘ Life and Evolution.” 1906. [Pictur-
esque concrete illustrations of the problems of evolution. ]
See also ‘‘ Problems of Evolution.” 1900.

Hvtron, F. W.—‘“‘ Darwinism and Lamarckism.” 1899. .

Hoxtiry, T. H.—Article ‘‘ Evolution” in ‘‘ Encyclopedia
Britannica,” 9th Edition.

aOR ** American Addresses.” (1877).

JENKINSON, J. W.—‘‘ Experimental Embryology.” 1909. [A
very able treatise on the external and internal factors in
development. With a valuable discussion of Vitalism
and Driesch’s contributions thereto. ]

**JOHANNSEN, W.—‘‘ Ueber Erblichkeit in Populationen und
in reinen Linien.” 1903. [Important experiments on
beans, barley, etc.; notably on the isolation of ‘‘ pure
lines.”] See also *‘Die Elemente der exakten Erblich-
keitslehre.” 1909,

JorDAN, D. 8., and Kmtioee, V. L.—‘‘ Evolution and Animal
Life.” 1907. [Very interesting concrete studies of
evolution problems. ]

Ketioce, V. L.—‘‘ Darwinism To-day.” 1907. [A remark-
able book, with the frankest and friendliest reconsidera-
tion of Darwinism, in the light of post-Darwinian progress,

BIBLIOGRAPHY 253

by 2 Seen competent critic. With abundant
references to and quotations from recent evolutionary
literature. ]

KropoTxin, P.—‘‘ Mutual Aid a Factor of Evolution.” 1902,
[A valuable account of the inadequately appreciated
‘other side” of the struggle for existence. ]

LANKESTER, E. Ray.—‘*The Advancement of Science.” 1890.
[Important essays on ‘‘ Degeneration: a chapter in
Darwinism,” ‘‘A Theory of Heredity,” ‘‘The History
and Scope of Zoology,” etc.] See also ‘‘The Kingdom
of Man.” 1906.

*Locx, R. H.—‘‘ Recent Progress in the Study of Variation,
Heredity, and Evolution.” 1908, [A useful introduction
to recent researches, |

Lorsy, J. P.—‘‘ Vorlesungen iiber Descendenztheorien. 2 vols,,
1907 and 1909. [A scholarly text-book of evolution. }

*MarsHaLL, A. Mitnes.—‘‘ Lectures on the Darwinian
Theory.” 1894. [An admirably clear and vigorous
presentation of Darwinism and of the evidences of
evolution.] See also ‘* Biological Lectures and Addresses,”
1894.

MarsHaut, F. H. A.—‘‘The Physiology of Reproduction.”
1910. [A masterly work with many bearings on evolution
problems. }

Mexz, J. T.—‘‘ History of Scientific Thought in the Nineteenth
Century.” 2nd vol., 1904. [The finest exposition of the
import and development of ‘‘the genetic view of Nature.”
A work of magistral scholarship and deep dnsigbt.

*Meroatr.—‘‘ Outline of the Theory of Organic Evolution.”
1904. [A useful introduction. }

**Moraan, 0, Luoryp.—‘‘ Habit and Instinct.” 1896. [The
most important book on instinct.] See also ‘‘ Animal
Life and Intelligence” (1890); revised edition, entitled
** Animal Behaviour.”’ 1900,

Morean, T. H.—‘‘ Evolution and Adaptation.” 1903. [An

~- important critical essay.]

**___ ** Experimental Zoology.” 1907. [An indispensable
account of recent experimental researches bearing on
evolution. A worthy supplement to Semper’s great
work, ‘‘ Animal Life.”’]

Nicrui, C. von.—‘‘ Mechanisch-physiologische Theorie der
Abstammmungslehre.” 1884. (‘The most effective pre-
sentation as yet given of the theory of organismal
variation in definite directions. ]

254 BIBLIOGRAPHY

Oszonn, H. F.—‘‘ From the Greeks to Darwin.” 1895. [A
vivid historical sketch. ]

Packarp, A. 8,—‘‘ Lamarck, his Lifeand Work.” 1901. [A
scholarly account of Lamarck’s theory of evolution. }
**Prarson, Karu.—‘‘The Grammar of Science.” 2nd
Edition, 1900. [The biological part includes an in-
valuable discussion of evolution problems from the

biometrician’s point of view.]

Pzrrizer, E.—‘‘ PhiloSophie zoologique avant Darwin.” 1884.
{A scholarly account of pre-Darwinian evolutionists and
generalizers. |

*PratE, L.—‘‘Selektionsprinzip und Probleme der Artbildung.
Ein Handbuch des Darwinismus.” 38rd Edition, 1908.
[A scholarly and lucid text-book of evolution, in part
Lamarckian. ]

**Poutton, E. B.—‘‘Essays on Evolution, 1889-1907.”
1908. [Very valuable critical and historical studies, and
applications of the theory of evolution to mimicry and
protective coloration in insects. ]

* ‘¢ Charles Darwin and the Theory of Natural Selection.”
1896.

**PRZIBRAM.—Experimental Zoology, Part I, Trans. 1908.
{Acute discussion by an expert investigator of the results
of experimental embryology. ]

*PunnErT, R. O.—‘‘ Mendelism.” 2nd Edition, 1905. [An
unsurpassed exposition by an expert investigator. ]
Ravi, Em.—‘‘Geschichte der biologischen Theorien.” 2nd
Part, 1909. [An able historical and critical discussion
of biological theories and of Darwinism in particular.]

Rep, G. ArcHDALL.—‘‘ The Laws of Heredity.” 1910. See
also ‘‘ The Principles of Heredity.” 1906.

RiGNano, E.—‘‘ Ueber die Vererbung erworbener Eigenschaf-
ten.” 1907. [A careful discussion of the question of the
transmission of acquired characters. }

Romanzs, G. J.—‘‘ Darwin and after Darwin.” 3 vols., 1892-
97. [A valuable exposition of Darwinism with many
original suggestions and criticisms, and with an important
discussion of isolation. ]

SonnerpER, K. O.—‘‘ Einfiihrung in die Descendenz-theorie,”
1906. [A fresh and lucid statement of the evidences of
evolution, with a short account of the chief theories. ]

Srmon, R.—‘‘ Die Mneme als erhaltendes Princip im Wechsel
des ee ar Geschehens.” 1904. [A modernized
Lamarckism. ]

BIBLIOGRAPHY 255

**SemperR, Kanu.—‘‘ The Natural Conditions of Existence as
they affect Animal Life.” 1881. [One of the finest and
soundest of biological books, with an educative sceptical
reserve, discussing in particular the influence of the
environment, but before the question of the transmission
of somatic modifications had become urgent. ]

Sewarp, A. O. (Editor).—‘‘ Darwin and Modern Science.”
1909. [A valuable series of essays by representative
biologists. }

***SpencER, HersBert.—‘“‘ Principles of Biology.” 2 vols.,
London, 1866-68, Revised Edition, 1908. [This was, in
its time, a masterpiece,a magnificent ‘‘ materialism,” an in-
comparably acute analysis and re-synthesis of the biology
of the day. The re-edition was, in our judgment, less
valuable, because it did not really assimilate the progress
that had been made. ]

STERNE, Carus [ErnnsT KravsxE].—‘‘ Werden und Vergehen.”
3rd Edition, 1886. [A remarkably vivid book giving an
account of the great steps in evolution. ]

—— ‘Die allgemeine Weltanschauungen.” 1889. [An in-
teresting account of the old interpretations of the
cosmos. |

Sutton, J. Buanp.—‘‘ Evolution and Disease.” 1890. [A
very suggestive contribution to the natural history of

isease. Comparison of pathological and normal changes
of structure.] See also ‘‘Introduction to General
Pathology.” 1886.

THomson, J. ArntHuR.—‘‘ The Science of Life.” 1899. [A
short general survey of the development of biology. ]

—— ‘‘The Study of Animal Life. [See examples of the web
of life, and the chapter on the evolution of evolution
theories. ]

—— ‘* Heredity.” 1909. [An exposition of the problems of
heredity and an estimate of the various contributions,—
biometrical, experimental and cytological ; and with an
extensive pcenaggcatige Oi

*_. ** Darwinism and Human Life.” 1909. [Six lectures
introductory to the study of evolution problems. ]

**TowER, W. L.—‘‘ Evolution in Chrysomelid Beetles.” 1906.
[An important investigation on environmental factors
serving as stimuli to germinal variations. ]

**Varieny, H. Dz.—‘‘ Experimental Evolution.” 1892. [An
admirable introduction to the experimental study of
evolution. ]

256 BIBLIOGRAPHY

*Vernon, H. M.—‘‘ Variation in Animals and Plants.” 1903.
[A useful introduction to the study of variation and espe-
cially to the biometric point of view.]

**Vries, H. Dze.—‘‘Species and Varieties, their Origin by

Mutation.” 1905. [A vivid series of lectures expounding
the author’s mutation theory. ]

**____. ** The Mutation Theory.” ‘Translation. 2 vols., 1910
and 1911. [A detailed account of the author’s remark-
able experiments and observations on the origin of species
in the vegetable kingdom.]

WALKER, C, E,—*‘ Heredi Characters and their Modes of
Transmission.” 1910. [A very interesting endeavour to
harmonize the results of the Mendelian experiments with
the observations of the biometricians. ]

*WALLACE, ALFRED RussEL.—‘‘ Darwinism.” 1889, [A
standard book of great value and interest, ¢g. in
showing how the author’s position differs in certain
respects from Darwin’s. ]

***____ ** Contributions to the Theory of Natural Selection.”
1871.

*WexisMANN, Avaust.—‘' The Evolution Theory.” 2 vols.,
1904. [Expressing the final convictions of a veteran
evolutionist, with a wealth of fact-illustration, which
remain, whatever be the verdict as to theory.]

**___ ‘The Germ-plasm.” Oontemporary Science Series.
1893.

**_____ 6 Essays on Poe and Kindred Subjects.” 1891-92.

Witson, E, B.—‘‘The Cell in Development and in Inherit-
ance.” 2nd. Edition, 1900. [An indispensable book
characterized by its high standard of accuracy and by
its maturity of judgment. ]

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NAPOLEON. By Hersert Fisuer, M.A., F.B.A.

4A SHORT HISTORY OF RUSSIA. By Prof. Mityvouxov.

MODERN TURKEY. By D.G. Hocartn, M.A.

FRANCE OF TO-DAY. By ALsert Tuomas.

GERMANY OF TO-DAY. By Cuarctes Tower.

THE NAVY AND SEA POWER. By Davin Hannay.

HISTORY OF SCOTLAND. ByR.S. Rart, M.A.

SOUTH AMERICA. By Prof. W. R. SHEPHERD.

LONDON. By Sir Laurence Gomme, F.S.A.

HISTORY AND LITERATURE OF SPAIN. By J. Fitzmaurice-
Ketty, F.B.A., Litt.D.

Literature and Art

2. SHAKESPEARE

By Joun Maseriecp. ‘The book isajoy. We have had half-a-dozen more
learned books on Shakespeare in the last few years, but not one so wise.”—
Manchester Guardian.

27. ENGLISH LITERATURE: MODERN
By G. H. Mair, M.A. “ Altogether a fresh and individual book.”—Odserver.
35. LANDMARKS IN FRENCH LITERATURE

By G.L. Srracugy. ‘ Mr Strachey is to be congratulated on his courage and
success. It is difficult to imagine how a better account of French Literature
could be given in 250 small pages than he has given here.”—The Tintes.

3

39. ARCHITECTURE .

By Prof. W. R. Leruasy. (Over forty Illustrations.) ‘‘ Popular guide-books
to architecture are, as arule, not worth much. ‘This volume is a welcome excep-
tion.” —Building News. ‘Delightfully bright reading.”—Christian IVorid.

43. ENGLISH LITERATURE: MEDIA:VAL

By Prof. W. P. Ker, M.A. ‘* Prof. Ker has long proved his worth as one of
the soundest scholars in English we have, and he is the very man to put an
outline of English Medizval Literature before the uninstructed public. His
knowledge and taste are unimpeachable, and his style is effective, simple, yet
never dry.”— The Atheneum.

45. THE ENGLISH LANGUAGE

By L. Pearsaty Smiru, M.A. “A wholly fascinating study of the different
streams that went to the making.of the great river of the English speech.”—
Daily News.

52. GREAT WRITERS OF AMERICA

By Prof. J. Erskine and Prof. W. P. Trent. A popular sketch by two
foremost authorities.

In PREPARATION
ANCIENT ART AND RITUAL. By Miss Janz Harrison, LL.D.,

D.Litt.
GREEK LITERATURE. By Prof. Girperr Murray, D.Litt.
LATIN LITERATURE. By Prof. J. S. PHmtimore.
CHAUCER AND HIS TIME. By Miss G. E. Havow.
THE RENAISSANCE. By Mrs R. A. TAytor.
ITALIAN ART OF THE RENAISSANCE. By RoGer E. Fry, M.A.
THE ART OF PAINTING. By Sir FrepERIcK WEDMORE.
DR JOHNSON AND HIS CIRCLE. By Joun Battey, M.A.
THE VICTORIAN AGE. By G. K. CHESTERTON.
ENGLISH COMPOSITION. By Prof. Wm. T. BREWSTER.
GREAT WRITERS OF RUSSIA. By C. T. Hacperc Wricut, LL.D.
THE LITERATURE OF GERMANY. By Prof. J. G. Roperrson,

M.A., Ph.D.
SCANDINAVIAN HISTORY AND LITERATURE. By T. C.
Snow, M.A.

Science
7. MODERN GEOGRAPHY

_ By Dr Marion Newsicin. (Illustrated.) ‘‘ Geography, again: what a dull,
tedious study that was wont to be! . . . But Miss Marion Newbigin invests its
dry bones with the flesh and blood of romantic interest, taking stock of
geography as a fairy-book of science.”—Daily Telegraph.

9. THE EVOLUTION OF PLANTS

By Dr D. H. Scott, M.A., F.R.S., late Hon. Keeper of the Jodrell Laboratory,
Kew. (Fully illustrated.) ‘The information which the book provides is as
trustworthy as first-hand knowledge can make it. . . . Dr Scott’s candid and
familiar style makes the difficult subject both fascinating and easy.”—
Gardeners’ Chronicle.

17, HEALTH AND DISEASE

By W. Lssuiz Macxenzisz, M.D., Local Government Board, Edinburgh.
‘* The science of public health administration has had no abler or more attractive
exponent than Dr Mackenzie. He adds toa thorough grasp ofthe problems
an illuminating style, and an arresting manner of treating a Subject often
dull and sometimes unsavoury.”—Lconomist. on

4

18 JI’TRODUCTION TO MATHEMATICS

By A. N. Wuirenzap, Sc.D., F.R.S. (With Diagrams.) ‘‘ Mr Whitehead
has discharged with conspicuous success the task he is so exceptionally qualified
tomndertake. For heis one of our great authorities upon the foundations of the
science, and has the breadth of view which is so requisite in presenting to the
reader its aims. His exposition is clear and striking.”—Westiminster Gazette.

19. THE ANIMAL WORLD

By Professor F. W. GamBug, D.Sc., F.R.S. With Introduction by Sir Oliver

Lodge. (Many Illustrations.) ‘* A delightful and instructive epitome of animal

mas vegetable)life. ... A most fascinating and suggestive survey.” —Morning
ost.

20. EVOLUTION

By Professor J. AkrHUR THomson and Professor Patrick GepprEs. “A
many-coloured and romantic panorama, opening up, like no other book we know,
a rational vision of world-development.”— Belfast News-Letter.

22. CRIME AND INSANITY

By Dr C. A. Mercier, F.R.C.P., F.R.C.S., Author of ‘* Text-Book of In-
sanity,” etc. ‘‘Furnishes much valuable information from one occupying the
highest position among medico- legal psychologists.” —A sy/um News. .

28. PSYCHICAL RESEARCH

By Sir W. F. Barrett, F.R.S., Professor of Physics, Royal College of Science,

Dublin, 1873-1910. _“‘ As a former President of the Psychical Research Society,

heis familiar with all the developments of this most fascinating branch of science,

and thus what he has to say on thought-reading, hypnotism, telepathy, crystal-

pe spiritualism, divinings, and so on, will be read with avidity.”—Dundee
ourier.

31. ASTRONOMY

By A. R. Hinks, M.A., Chief Assistant, Cambridge Observatory. ‘‘ Original
in thought, eclectic in substance, and critical in treatment. ... No better
little book is available.”—School World.

32. INTRODUCTION TO SCIENCE

By J. ARTHUR THomsON, M.A., Regius Professor of Natural History, Aberdeen
niversity. ‘* Professor Thomson’s delightful literary style is well known ; and
here he discourses freshly and easily on the methods of science and its relations
with philosophy, art, religion, and practical life.” A derdeen Journai.

36. CLIMATE AND WEATHER

By H. N. Dickson, D.Sc. Oxon., M.A., F.R.S.E., President of the Royal
eteorological Society ; Professor of Geography in University College, Reading.
(With Diagrams.) ‘‘ The author has suocmeued in presenting in a very lucid
and agreeable manner the causes of the movement of the atmosphere and of
the more stable winds.” —Manchester Guardian.

41. ANTHROPOLOGY

By R. R. Marert, M.A., Reader in Social Anthropology in Oxford University.
** An absolutely perfect handbook, so clear that a child could understand it, so
fascinating and human that it beats fiction ‘to a frazzle.'”"—Morning Leader.

44. THE PRINCIPLES OF PHYSIOLOGY

By Prof. J.G. McKenprick, M.D. “Itis a delightful and wonderfully com-
prehensive handling of a subject which, while of importance to all, does not
readily lend itself to untechnical explanation. . . . The little book is more than
@ mere repository of knowledge; upon every page of it is stamped the impress

of a creaitve imagination.”"—Glasgow Heradd.

5

46. MATTER AND ENERGY

By F. Soppy, M.A., F.R.S. ‘‘A most fascinating and instructive account of
the great facts of physical science, concerning which our knowledge, of later
years, has made such wonderful progress.”--The Bookseller.

49. PSYCHOLOGY, THE STUDY OF BEHAVIOUR

By Prof. W. McDoveatt, F.R.S., M.B. ‘A happy example of the non-
technical handling of an unwieldy science, suggesting rather than dogmatising.
It should whet appetites for deeper study.”—Chvistian Worid.

53. THE MAKING OF THE EARTH

By Prof. J. W. Grecory, F.R.S. (With 38 Mapsand Figures.) The Professor
of Geology at Glasgow describes the origin of the earth, the formation and
changes of its surface and structure, its geological history, the first appearance
of life, and its influence upon the globe.

57. THE HUMAN BODY

By A. Keiru, M.D., LL,D., Conservator of Museum and Hunterian Pro-
fessor, Royal College of Surgeons. (Illustrated.) The work of the dissecting-
room is described, and among other subjects dealt with are: the development
of the body ; malformations and monstrosities; changes of youth and age; sex
differences, are they increasing or decreasing? race characters ; bodily features
as indexes of mental character; degeneration and regeneration; and the
genealogy and antiquity of man.

68. ELECTRICITY

By Gispert Kapp, D.Eng., M.I.E.E., M.I.C.E., Professor of Electrical
Engineering in the University of Birmingham. (Illustrated.) Deals with
frictional and contact electricity; potential; electrification by mechanical
means; the electric current; the dynamics of electric currents; alternating
currents ; the distribution of electricity, etc.

In PREPARATION

CHEMISTRY. Py Prof. R. Metpora, F.R.S.

THE MINERAL WORLD. By SirT. H. Houtianp, K.C.I.E., D.Sc.
PLANT LIFE. By Prof. J. B. Farmer, F.R.S.

NERVES. By Prof. D. Fraser Harris, M.D., D.Sc.

ASTUDYVOF SEX. By Prof. J. A. THomson and Prof. Patrick GEDDES.
THE GROWTH OF EUROPE. By Prof. GrRenvitLE COLE.

Philosophy and Religion

15.5 MOHAMMEDANISM

By Prof. D. S. Marco.ioutu, M.A., D.Litt. ‘This generous shilling’s
worth of wisdom... . A delicate, humorous, and most responsible tractate
by an illuminative professor."—Daily Mail.

40. THE PROBLEMS OF PHILOSOPHY

By the Hon. BERTRAND Russet, F.R.S. ‘‘A book that the ‘man in the
street’ will recognise at once to be a boon. . . . Consistently lucid and non-
technical throughout.”—Christian World.

47. BUDDHISM

By Mrs Ruys Davips, M.A. ‘A very able and concise ‘study of the Buddhist
norm.’ ... The author presents very attractively as well as very learnedly
the philosophy of Buddhism as the greatest scholars of the day interpret it.”—
Daily News.

6

50. VONCONFORMITY: Its ORIGIN and PROGRESS

By Principal W. B. Setpiz, M.A, ‘*The historical part is brilliant in its
insight, clarity, and proportion, and in the later chapters on the present position
and aims of Nonconformity Dr Selbie proves himself to be an ideal exponent
of sound and moderate views.”—Christian World.

54. ETHICS

By G. E. Moors, M.A., Lecturer in Moral Science in Cambridge University.
Discusses Utilitarianism, the Objectivity of Moral Judgments, the Test of
Right and Wrong, Free Will, and Intrinsic Value.

56. THE MAKING OF THE NEW TESTAMENT

By Prof. B. W. Bacon, LL.D., D.D. An authoritative summary of the results
of modern critical research with regard to the origins of the New Testament, in
*‘ the formative period when conscious inspiration was still in its full glow rather
than the period of collection into an official canon,” showing the mingling of the
two great currents of Christian thought—- Pauline and ‘ Apostolic,’ the Greek-
Christian gospel adout Jesus, and the Jewish-Christian gospel of Jesus, the
gospel of the Spirit and the gospel of authority.”

60. MISSIONS: THEIR RISE and DEVELOPMENT

By Mrs Creicuton. The beginning of modern missions after the Reforma-
tion and their growth are traced, and an account is given of their present
work, its extent and character.

In PREPARATION

THE OLD TESTAMENT. By Prof. GrorczE Moore, D.D., LL.D.

BETWEEN THE OLD AND NEW TESTAMENTS. By R. H.
CuHarR.Les, D.D.

COMPARATIVE RELIGION. By Prof. J. Esrtin Carpenter, D.Litt.

A HISTORY of FREEDOM of THOUGHT. By Prof. J. B. Bury, LL.D.

A HISTORY OF PHILOSOPHY. By CLement Wess, M.A.

Social Science

1. PARLIAMENT
Its History, Constitution, and Practice. By Sir Courtenay P. ILBert,
K.C.B., K.C.S.1., Clerk of the House of Commons. ‘The best book on the
history and practice of the House of Commons since Bagehot'’s ‘Constitution.’”—
Yorkshire Post.

5. THE STOCK EXCHANGE

By F. W. flrest, Editor of “The Economist.” ‘To an unfinancial mind must
bea revelation. . . . The book is as clear, vigorous, and sane as Bagehot’s ‘ Lom-
bard Street,’ than which there is no higher compliment.”—Morning Leader.

6. IRISH NATIONALITY

By Mrs J. R.Green. ‘“ As glowing as it is learned. No book could be more
timely.” —Daily News. ‘A powerful study. . . . A magnificent demonstration
of the deserved vitality of the Gaelic spirit.”—reeman’s Journal.

10. THE SOCIALIST MOVEMENT

By J. Ramsay MacDonatp, M.P. ‘‘Admirably adapted for the purpose of
exposition. ”"—7he Times. ‘*‘ Mr MacDonald isa very lucid exponent. ... The
volume will be of great use in dispeiling illusions about the tendencies of
Socialism in this country."—The Nation.

11. CONSERVATISM

By Lord Hucu Cecii, M.A.,M.P. ‘One of those great little books which
seldom appear more than once in a generation.”—Morning Post.

7

16. THE SCIENCE OF WEALTH
By J. A. Hoxson, M.A. “Mr J. A. Hobson holds an unique |
living economists. . . . The text-book produced is altoget
Original, reasonable, and illuminating.”—7he ation.

21. LIBERALISM

By L. T. Hosuouss, M. A,, ‘Pisieaa of Sociology i in the University
OA book of rare quality. . . . We have nothing but praise for t
masterly summaries of the arguments from first principles which )
part of this book.”—Westminster Gazette. 2

24. THE EVOLUTION OF INDUSTRY

By D. H. Maccrecor, M.A., Professor of Political Economy i in the
of Leeds. ‘‘A volume so dispassionate i in terms may be read with p
interested in the present state of unrest.”—Aderdeen Journal,

26. AGRICULTURE

By Prof. W. Somervi.ue, F.L.S. ‘It makes the results of la
at the University accessible to the practical farmer.”—A theneum.

30. ELEMENTS OF ENGLISH LAW Sa

By W. M. Getpart, M.A., B.C.L., Vinerian Professor of English

Oxford. ‘‘Contains a very clear account of the elementary principl 3
lying the rules of English law; and we can recommend it to all
become acquainted with these elementary principles with a mini
trouble.”—Scots Law Times.

38. THE SCHOOL

“ n Introduction to the Study of Education,
J. Finpray, M.A., Ph.D., Professor of Education in ]

Uriversity. ‘An amazingly comprehensive volume... . Itisa b :
performance, distinguished in its crisp, striking phraseology as well as |
inclusiveness of subject-matter.”—Morning Post. : . ze

59. ELEMENTS OF POLITICAL ECONOMY |

By S. J. Cuapman, M.A., Professor of Political Economy in Mandl ch
University. A simple explanation, i in the light of the latest economic tho
of the working of demand and supply; the nature of monopoly ; money a’
international trade; the relation of wages, profit, interest, and rent; bas:
effects of labour combination—prefaced by a short sketch of economic s
since Adam Smith.

IN PREPARATION

Cyres, M.A.
COMMONSENSE IN LAW. By Prof. P. VinoGRADOFF, D.C aE
THE CIVIL SERVICE. By Eaepinnsk Wa tuas, M.A. Pat
PRACTICAL IDEALISM. By Maurice HEwterr.
NEWSPAPERS. By G. Binney DresLze. :
ENGLISH VILLAGE LIFE. By E. N. Bennett, M.A. aa
CO - ache esc Pig ot AAD PROFIT-SHARING. By. Ae IR
Wiiuiams, J. 3
THE SOCIAL SETTLEMENT. By Jane AppDAMsS a A.W
GREAT INVENTIONS. By Prof. J. L. Myrzus, M.A., F.S.A.
TOWN PLANNING. By Raymonp Unwin.
POLITICAL THOUGHT IN ENGLAND: From Bentham ah
Mill. By Prof. W. L. Davipson.
POLITICAL THOUGHT iN ENGLAND: From Hertert §
to To-day. By Ernest Barker, M.A

London: WILLIAMS AND NORGATE
And of all Bookshops and Bookstatts.

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