LIBRARY

UNIVERSITY OF
CALIFORNIA
SAN DIEGO

ANIMAL LIFE AND INTELLIGENCE.

j^ LLOYD .MORGAN, F.G.S.,

PROFESSOR IN AND DEAN OF UNIVERSITY COLLEGE, BRISTOL;
LECTURER AT THE BRISTOL MEDICAL SCHOOL;

PRESIDENT OF THE BRISTOL NATURALISTS' SOCIETY, ETC.

AUTHOR OF
"ANIMAL BIOLOGY," "THE SPRINGS OF CONDUCT," ETC.

BOSTON, U.S.A.:

GIXX & COMPANY, PUBLISHERS.
1891.

TO

MY FATHER.

PREFACE.

THERE are many books in our language which deal with
Animal Intelligence in an anecdotal and conventionally
popular manner. There are a few, notably those by Mr.
Eomanes and Mr. Mivart, which bring adequate knowledge
and training to bear on a subject of unusual difficulty. In
the following pages I have endeavoured to contribute some-
thing (imperfect, as I know full well, but the result of
several years' study and thought) to our deeper knowledge
of those mental processes which we may fairly infer from
the activities of dumb animals.

The consideration of Animal Intelligence, from the
scientific and philosophical standpoint, has been my
primary aim. But so inextricably intertwined is the
subject of Intelligence with the subject of Life, the subject
of organic evolution with the subject of mental evolution,
so closely are questions of Heredity and Natural Selection
interwoven with questions of Habit and Instinct, that I have
devoted the first part of this volume to a consideration
of Organic Evolution. The great importance and value
of Professor Weismann's recent contributions to biological
science, and their direct bearing on questions of Instinct,
rendered such treatment of my subject, not only advisable,
but necessary. Moreover, it seemed to me, and to those
whom I consulted in the matter, that a general work on
Animal Life and Intelligence, if adequately knit into a
connected whole, and based on sound principles of science

vi Preface.

and of philosophy, would not be unwelcomed by biological
students, and by that large and increasing class of readers
who, though not professed students, follow with eager
interest the development of the doctrine of Evolution.

Incidentally, but only incidentally, matters concerning
man, as compared with the dumb animals, have been
introduced. It is contended that in man alone, and in no
dumb animal, is the rational faculty, as defined in these
pages, developed ; and it is contended that among human-
folk that process of natural selection, which is so potent a
factor in the lower reaches of organic life, sinks into com-
parative insignificance. Man is a creature of ideas and
ideals. For him the moral factor becomes one of the very
highest importance. He conceives an ideal self which he
strives to realize ; he conceives an ideal humanity towards
which he would raise his fellow-man. He becomes a
conscious participator in the evolution of man, in the
progress of humanity.

But while we must not be blind to the effects of new
and higher factors of progress thus introduced as we rise
in the scale of phenomena, we must at the same time
remember that biological laws still hold true, though moral
considerations and the law of duty may profoundly modify
them. The eagle soars aloft apparently in defiance of
gravitation ; but the law of gravitation still holds good ;
and no treatment of the mechanism of flight which neglected
it would be satisfactory. Moral restraint, a higher standard
of comfort, and a perception of the folly and misery of early
and improvident marriage may tend to check the rate of
growth of population : but the " law of increase " still holds
good, as a law of the factors of phenomena ; and Malthus
did good service to the cause of science when he insisted
on its importance. We may guide or lighten the incidence
of natural selection through competition ; we may in our
pity provide an asylum for the unfortunates who are suffer-

Preface. vii

ing elimination ; but we cannot alter a law which, as that
of one of the factors of organic phenomena, still obtains,
notwithstanding the introduction of other factors.

However profoundly the laws of phenomena may be
modified by such introduction of new and higher factors,
the older and lower factors are still at work beneath the
surface. And he who would adequately grasp the social
problems of our time should bring to them a mind prepared
by a study of the laws of organic life : for human beings,
rational and moral though they may be, are still organisms ;
and man can in no wise alter or annul those deep-lying
facts which nature has throughout the ages been weaving
into the tissue of life.

Some parts of this work are necessarily more technical,
and therefore more abstruse, than others. This is especially
the case with Chapters III., V., and VI. ; while, for those
unacquainted with philosophical thought, perhaps the last
chapter may present difficulties of a different order. With
these exceptions, the book will not be beyond the ready
comprehension of the general reader of average intelligence.

I have to thank many kind friends for incidental help.
Thanks are also due to Professor Flower, who courteously
gave permission that some of the exhibits in our great
national collection in Cromwell Eoad might be photographed
and reproduced ; and to Messrs. Longmans for the use of
two or three illustrations from my text-book of "Animal
Biology."

C. LLOYD MOEGAN.

UNIVERSITY COLLEGE, BRISTOL,
October, 1890.

CONTENTS.

CHAPTER I.

THE NATURE OF ANIMAL LIFE.

PAGE

The characteristics of animals .. .. .. .. •• 2

The relation of animals to food-stuffs . .

„ „ „ the atmosphere , . . . . . . . 15

„ „ „ energy

CHAPTER II.

THE PROCESS OF LIFE.

Illustration from respiration . . . . . . . . 21

„ nutrition .. .. .. .. 25

The utilization of the materials incorporated

The analogy of a gas-engine. Explosive metabolism . . 30

CHAPTER III.

REPRODUCTION AND DEVELOPMENT.

Keproduction in the protozoa .. .. .. .. ..37

Fission in the metazoa . . . . . . . . . . 41

The regeneration of lost parts . . . . . . . . 41

Keproduction by budding . . . . . . . . . . 42

Sexual reproduction . . . . . . . . 42

Illustration of development . . . . . . . . . . 51

Parental sacrifice . . . . . . . . . . 56

The law of increase . . 58

CHAPTER IV.

VARIATION AND NATURAL SELECTION.

The law of persistence . . . . . . . . . . 61

The occurrence of variations . . . . . . . . . . 63

Application of the law of increase . . . . . 76

Natural selection , 77

Contents.

Elimination and selection . . . . 79

Modes of natural elimination illustrated

Protective resemblance and mimicry . . . . 82

Selection proper illustrated ..

The effects of natural selection ..

Isolation or segregation

Its modes, geographical, preferential and physiological . . . • 99

Its effects .. .. .. .. .. .. .. 108

Utility of specific characters

Variations in the intensity of the struggle for existence . .

Convergence of characters . . . . . . . . . . 117

Modes of adaptation : Progress

Evolution and Revolution • • 120

CHAPTER V.

HEREDITY AND THE ORIGIN OF VARIATIONS.

Heredity in the protozoa . . . . . . . . . . 123

Regeneration of lost parts . . . . . . . . 124

Sexual reproduction and heredity . . . . . . . . 129

The problem of hen and egg . . . . . . . . . . 130

Reproductive continuity . . . . . . . . 131

Pangenesis . . . . . . . . . . . . 131

Modified pangenesis . . . . . . . . . . . . 134

Continuity of germ-plasm . . . . . . . . . . 138

Cellular continuity with differentiation . . . . . . . . 142

The inheritance or non-inheritance of acquired characters . . 146

Origin of variations on the latter view . . . . . . . . 149

Hypothesis of organic combination . . . . . . . . 150

The extrusion of the second polar cell .. .. .. ..153

The protozoan origin of variations - . . . . . . . . 156

How can the body influence the germ ? . . . . . . 159

Is there sufficient evidence that it does ? . . . . . . 162

Summary and conclusion . . . . . . . . . . 175

CHAPTER VI.

ORGANIC EVOLUTION.

The diversity of animal life . . . . . . . . . . 177

The evolution theory . . . . . . . . . . 181

Natural selection : not to be used as a magic formula . . . . 183

Panmixia and disuse . . . . . . . . . . 189

Sexual selection or preferential mating . . . . . . . . 197

Use and disuse . . . . . . . . . . . . 209

The nature of variations. . . . . . . . . . . . 216

The inheritance of variations . . . . . . . . 223

The origin of variations . . . . . . . . . , . . 231

Summary and conclusion . . . . . . . . . . 241

Contents.

CHAPTER VII.

THE SENSES OF ANIMALS.

PAGE

Tbe primary object of sensation . . . . 243

Organic sensations and tbe muscular sense . . 244

Touch . . . . . . . . . . . . 245

The temperature-sense . . . . . . . 249

Taste.. .. .. .. .. .. .. ..250

Smell .. .. .. .. .-. , .. .. 257

Hearing .. .. .. .. .. .. ..261

Sense of rotation or acceleration . . . . • . . . . 269

Sight . . . . . . . . . . ..." . . 273

Restatement of theory of colour-vision . . . . . . 278

Variation in the limits of colour-vision . . . . . . . . 281

The four types of " visual " organs . . . . . . . . 293

Problematical senses . . . . . . . . . . . . 294

Permanent possibilities of sensation . . . . . . . . 298

CHAPTER VIII.

MENTAL PEOCESSES IN MAN.

The physiological aspect . . . . . . . . . . 302

The psychological aspect . . . . . . . . . . 304

Sensations : their localization, etc. . . . . . . . . 306

Perceptual construction . . . . . . 312

Conceptual analysis . . . . . . . . . . . . 321

Inferences perceptual and conceptual . . . . . . . . 328

Intelligence and reason . . . . . . . . . . . . 330

CHAPTER IX.

MENTAL PROCESSES IN ANIMALS : THEIR POWERS OF PERCEPTION AND
INTELLIGENCE.

The two factors in phenomena . . . . . . . . . . 331

The basis in organic evolution . . . . . . . . 336

Perceptual construction in mammalia . . . . . . . . 338

Can animals analyze their constructs ? . . . . . . 347

The generic difference between the minds of man and brute . . . . 350

Perceptual construction in other vertebrates . . . . . . 350

" Understanding " of words . . . . . . . . . . 354

Perceptual construction in the invertebrates . . . . . . 356

" The psychic life of micro-organisms " . . . . . . 360

The inferences of animals . . . . . . . . . . 361

Intelligent not rational . . . . . . . . . . . . 365

Use of words defined . . . . . . . . . . 372

Language and analysis .. .. .. .. .. ., 374

Contents.

CHAPTER X.

THE FEELINGS OF ANIMALS: THEIR APPETENCES AND EMOTIONS.

PAGE

Pleasure and pain : their organic limits . . . . . . 379

Their directive value .. .. .. .. ... 380

An emotion exemplified . . . . . . . . . . . . 382

Sensitiveness and sensibility-.. .. .. .. .. 385

The expression of the emotions . . . . . . . . . . 385

The postponement of action . . . . . . . . . . 385

The three orders of emotion . . . . . . . . . . 390

The capacities of animals for pleasure and pain . . . . 391

Sense-feelings . . . . . . . . . . . . . . 393

Some emotions of animals . . . . . . . . . . 395

The necessity for caution in interpretation . . . . . . . . 399

The sense of beauty . . . . . . . . . . 407

Can animals be moral ? . . . . . . . . . . . . 413

Conclusion . . . . . . . . . . . . 414

CHAPTER XI.

ANIMAL ACTIVITIES : HABIT AND INSTINCT.

The nature of animal activities .. .. .. .. ..415

The outer and inner aspect . . . . . . . . . . 417

The inherited organization . . . . . . . . 419

Habitual activities . . . . . . . . . . . . 420

Instinctive activities . . . . . . . . . . . . 422

Innate capacity . . . . . . . . . . . . 426

Blind prevision . . . . . . . . . . . . 429

Consciousness and instinct . . . . . . . . . . 432

Mr. Komanes's treatment of instinct . . . . . . . . 434

Lapsed intelligence and modern views on heredity . . . . 435

Three factors in the origin of instinctive activities . . . . . . 447

The emotional basis of instinct . . . . . . . . 449

The influence of intelligence on instinct . . . . . . . . 452

The characteristics of intelligent activities . . . . . . 456

The place of volition .. .. .. .. ..459

Perceptual and conceptual volition . . . . . . 460

Consciousness and consentience . . . . . . . . . . 46 1

Classification of activities .. .. .. .. .. 462

CHAPTER XII.

MENTAL EVOLUTION.

Is mind evolved from matter ? .. .. .. .. ..464

Kinesis and metakinesis . . . . . . . . . . 467

Monistic assumptions . . . . . . . . . . . . 470

The nature of ejects . . . . . . . . 476

Contents. xiii

PAGE

The universe as eject . . . . . . . . . . . . 478

Metakinetic environment of mind . . . . . . . . 481

Conceptual ideas not subject to natural selection . . . . . . 483

Elimination through incongruity . . . . . . . . 486

Intemeural evolution . . . . . . . . . . . . 490

Interpretations of nature . . . . . . . . ... 492

Gun fetishism have had a natural genesis ? . . . . . . 493

The origin of interneural variations . . . . . . . . 496

Are acquired variations inherited ? . . . . . . . . 497

Summary and conclusion . . . . . . . . . . 501

LIST OF ILLUSTRATIONS.

FIG. PAGB

KENTISH PLOVEK WITH EGGS AND YOUNG Frontispiece

1. SPIRACLES AND AIH-TTJBES OF COCKROACH .. .. .. 3

2. GILLS OF MUSSEL . . . . . . . . . . 4

3. A CELL GREATLY MAGNIFIED . . 11

4. AM<EBA . . . . . . . . . . . . 12

5. EGG-CELL AND SPERM-CELL . . . . . . 13

6. DIAGRAM OF CIRCULATION .... 23

7. PROTOZOA . . . . . . . . . . 38

8. HYDRA VIRIDES . . . . . . . . . . 43

9. AURELIA : LIFE-CYCLE . . . . . . . . 45

10. LITER-FLUKE— EMBRYONIC STAGES ;. . . . . 47

11. DIAGRAM OF DEVELOPMENT .. .. .. .. ..51

12. WING OF BAT (PIPISTRELLE) .... . . . . 64

13. VARIATIONS OF THE NOCTULE ..' .. .. ..67

14. „ „ LONG-EARED BAT . . . . . . 68

15. „ „ PIPISTRELLE .. .. .. ..69

16. „ „ WHISKERED BAT . . . . . . 70

17. VARIATIONS ADJUSTED TO THE STANDARD OF THE NOCTULE . . 73

18. CATERPILLAR OF A MOTH ON AN OAK SPRAY .. .. 85

19. LOCUST RESEMBLING A LEAF . . . . . . . . 86

20. MIMICRY OF BEES BY FLIES . . . . . . . . 91

21. EGG AND HEN .. .. .. .. 141

22. STAG-BEETLES .. .. .. .. .. .. 180

23. TACTILE CORPUSCULES . . . . . . . . . . 247

24. TOUCH-HAIR OF INSECT . . . . . . . . . . 248

25. TASTE-BUDS OF RABBIT . . . . . . . . . . 250

26. ANTENNULE OF CRAYFISH . . . . . . . . 259

27. DIAGRAM OF EAR . . . . . . . . . . . . 263

28. TAIL OF MYSIS . . . . . . . . . . 266

29. LEG OF GRASSHOPPER . . . . . . . . . . 266

30. DIAGRAM OF SEMICIRCULAR CANALS 270

xvi List of Illustrations.

FIG. PAGE

31. THE HUMAN EYE . . . . . . . . . . . . 274

32. EETINA OF THE EYE . . . . . . . . . . 274

33. VARIATION IN THE LIMITS OF COLOUR- VISION . . . . . . 281

34. PINEAL EYE . . . . . . . . . . . . 288

35. SKULL OF MELANERPETON . . . . . . . . 288

36. EYES AND EYELETS OF BEE . . . . . . . . 289

37. EYE OF FLY . . . . . . . . . . . . 290

38. DIAGRAM OF MOSAIC VISION .. .. .. .. 291

39. DiHECTION-BETINA . . . . . . . . . . . . 295

40. ANTENNARY STRUCTURES OF HYMENOPTERA 297

ANIMAL LIFE AND INTELLIGENCE.

CHAPTEE I.

THE NATURE OF ANIMAL LIFE.

I ONCE asked a class of school-boys to write down for me in
a few words what they considered the chief characteristics
of animals. Here are some of the answers —

1. Animals move about, eat, and grow.

2. Animals eat, grow, breathe, feel (at least, most of
them do), and sleep.

3. Take a cat, for example. It begins as a kitten; it
eats, drinks, plays about, and grows up into a cat, which
does much the same, only it is more lazy, and stops grow-
ing. At last it grows old and dies. But it may have
kittens first.

4. An animal has a head and tail, -four legs, and a
body. It is a living creature, and not a vegetable.

5. Animals are living creatures, made of flesh and
blood.

Combining these statements, we have the following
characteristics of animals : —

1. Each has a proper and definite form, at present
described as " a head and tail, four legs, and a body."

2. They breathe.

3. They eat and drink.

4. They grow.

5. They also " grow up." The kitten grows up into a
cat, which is somewhat different from the kitten.

6. They move about and sleep.

Animal Life and Intelligence.

7. They feel — " at least some of them do."

8. They are made of " flesh and blood."

9. They grow old and die.

10. They reproduce their kind. The cat may have
kittens.

11. They are living organisms, but " not vegetables."
Now, let us look carefully at these characteristics, all

of which were contained in the five answers, and were
probably familiar in some such form as this to all the
boys, and see if we cannot make them more general and
more accurate.

1. An animal has a definite form. My school-boy friend
described it as a head and tail, four legs, and a body. But
it is clear that this description applies only to a very limited
number of animals. It will not apply to the butterfly, with
its great wings and six legs ; nor to the lobster, with its
eight legs and large pincer-claws ; to the limbless snake
and worm, the finned fish, the thousand-legs, the oyster
or the snail, the star-fish or the sea-anemone. The
animals to which my young friend's description applies
form, indeed, but a numerically insignificant proportion
of the multitudes which throng the waters and the air,
and not by any means a large proportion of those that
walk upon the surface of the earth. The description
applies only to the backboned vertebrates, and not to
nearly all of them.

It is impossible to summarize in a sentence the form-
characteristics of animals. The diversities of form are
endless. Perhaps the distinguishing feature is the pre-
valence of curved and rounded contours, which are in
striking contrast to the definite crystalline forms of the
inorganic kingdom, characterized as these are by plane
surfaces and solid angles. We may say, however, that all
but the very lowliest animals have each and all a proper
and characteristic form of their own, which they have in-
herited from their immediate ancestors, and which they
hand on to their descendants. But this form does not
remain constant throughout life. Sometimes the change

The Nature of Animal Life.

is slight; in many cases, however, the form alters very
markedly during the successive stages of the life of the
individual, as is seen in the frog, which begins life as a
tadpole, and perhaps even more conspicuously in the
butterfly, which passes through a caterpillar and a chry-
salis stage. Still, these changes are always the same for
the same kind of animal. So that we may say, each
animal has a definite form and shape or series of shapes.

2. Animals breathe. The essential thing here is that
oxygen is taken in by the organism, and carbonic acid gas
is produced by the organism. No animal can carry on its
life-processes unless certain chemical changes take place
in the substance of which it is composed. And for these
chemical changes oxygen is essential. The products of
these changes, the most familiar of which are carbonic
acid gas and urea, must be got rid of by the process of
excretion. Eespiration and excretion are therefore essential
and characteristic life-processes of all animals.

In us, and in all air-breathing vertebrates, there are
special organs set apart for respiration and excretion
of carbonic acid gas. These are
the lungs. A great number of
insects also breathe air, but in a
different way. They have no lungs,
but they respire by means of a
number of apertures in their sides,
and these open into a system of a/ c
delicate branching tubes which
ramify throughout the body. Many

organisms, however, such as fish Fig. 1.— Diagram of spiracles

and lobsters and molluscs, breathe

the air dissolved in the water in The skin, etc., of the back has

. . been removed, and the crop (cr.)

Which they live. The Special Organs and alimentary canal (al.c.) dis-

* . ° played. The air-tubes are repre-

developed for this purpose are the 8eiited by dotted lines- The tei»

A spiracles are numbered to the right

gills. They are freely exposed to of the figure.
the water from which they abstract the air dissolved therein.
When the air dissolved in the water is used up, they sicken
and die. There can be nothing more cruel than to keep

Animal Life and Intelligence.

aquatic animals in a tank or aquarium in which there is
no means of supplying fresh oxygen, either by the action
of green vegetation, or by a jet of water carrying down air-
bubbles, or in some other way. And then there are a
number of animals which have no special organs set apart
for breathing. In them respiration is carried on by the
general surface of the body. The common earthworm is

Fig. 2.— Gills of mussel.

o.g., outer gill ; i.g., inner gill; mo., mouth ; m., muscles for closing shell ; ma., mantle;
*., shell; /.. foot; h., position of heart; e.s., exhalent siphon, whence the water passes out
from the gill-chamber ; i.s., inhalent eiphon, where the water enters.

The left valve of the shell has been removed, and the mantle cut away along the dark line.

one of these ; and most microscopic organisms are in the
same condition. Still, even if there be no special organs
for breathing, the process of respiration must be carried on
by all animals.

3. They eat and drink. The living substance of an
animal's body is consumed during the progress of those
chemical changes which are consequent upon respiration ;
and this substance must, therefore, be made good by
taking in the materials out of which fresh life-stuff can
be formed. This process is called, in popular language,
feeding. But the food taken in is not identical with the
life-stuff formed. It has to undergo a number of chemical
changes before it can be built into the substance of the
organism. In us, and in all the higher animals, there is
a complex system of organs set aside for the preparation,
digestion, and absorption of the food. But there are
certain lowly organisms which can take in food at any
portion of their surface, and digest it in any part of their

The Nature of Animal Life.

substance. One of these is the amoeba, a minute speck of
jelly-like life-stuff, which lives in water, and tucks in a bit
of food-material just as it comes. And there are certain
degenerate organisms which have taken to a parasitic life,
and live within the bodies of other animals. Many of
these can absorb the material prepared by their host
through the general surface of their simple bodies. But
here, again, though there may be no special organs set
apart for the preparation, absorption, and digestion of
food, the process of feeding is essential to the life of all
animals. Stop that process for a sufficient length of time,
and they inevitably die.

4. They grow. Food, as we have just seen, has to be
taken in, digested, and absorbed, in order that the loss of
substance due to the chemical changes consequent on
respiration may be made good. But where the digestion
and absorption are in excess of that requisite for this
purpose, we have the phenomenon of growth.

What are the characteristics of this growth ? We
cannot, perhaps, describe it better than by saying (1) that
it is organic, that is to say, a growth of the various organs
of the animal in due proportion; (2) that it takes place,
not merely by the addition of new material (for a crystal
grows by the addition of new material, layer upon layer),
but by the incorporation of that new material into the very
substance of the old; and (3) that the material incor-
porated during growth differs from the material absorbed
from without, which has undergone a preparatory chemical
transformation within the animal during digestion. The
growth of an animal is thus dependent upon the continued
absorption of new material from without, and its trans-
formation into the substance of the body.

The animal is, in fact, a centre of continual waste and
repair, of nicely balanced constructive and destructive
processes. These are the invariable concomitants of life.
Only so long as the constructive processes outbalance the
destructive processes does growth continue. During the
greater part of a healthy man's life, for example, the two

Animal Life and Intelligence.

processes, waste and repair, are in equilibrium. In old
age, waste slowly but surely gains the mastery ; and at
death the balanced process ceases, decomposition sets in,
and the elements of the body are scattered to the winds or
returned to mother earth.

There are generally limits of growth which are not
exceeded by any individuals of each particular kind of
animal. But these limits are somewhat variable among
the individuals of each kind. There are big men and
little men, cart-horses and ponies, bloodhounds and lap-
dogs. Wild animals, however, when fully grown, do not
vary so much in size. The period of growth is also
variable. Many of the lower backboned animals probably
grow during the whole of life, but those which suckle their
young generally cease growing after a fraction (in us from
one-fourth to one-fifth) of the allotted span of life is
past.

5. But animals not only grow — they also "grow up."
The kitten grows up into a cat, which is somewhat different
from the kitten. We speak of this growing up of an animal
as its development. The proportion of the various parts
and organs progressively alter. The relative lengths of
the arms and legs, and the relative size of the head, are
not the same in the infant as in the man or woman. Or,
take a more marked case. In early spring there is plenty
of frog-spawn in the ponds. A number of blackish specks
of the size of mustard seeds are embedded in a jelly-like
mass. They are frogs' eggs. They seem unorganized.
But watch them, and the organization will gradually
appear. The egg will be hatched, and give rise to a little
fish-like organism. This will by degrees grow into a
tadpole, with a powerful swimming tail and rounded h.ead
and body, but with no obvious neck between them. Legs
will appear. The tail will shrink in size and be gradually
drawn into the body. The tadpole will have developed
into a minute frog.

There are many of the lower animals which go through
a not less wonderful, if not more wonderful, metamorphosis.

The Nature of Animal Life.

The butterfly or the silkworm moth, beginning life as a
caterpillar and changing into a chrysalis, from which the
perfect insect emerges, is a familiar instance. And hosts
of the marine invertebrates have larval forms which have
but little resemblance to their adult parents.

Such a series of changes as is undergone by the frog
is called metamorphosis, which essentially consists in the
temporary development of certain provisional embryonic
organs (such as gills and a powerful swimming tail) and
the appearance of adult organs (such as lungs and legs) to
take their place. In metamorphosis these changes occur
during the free life of the organism. But beneath the
eggshell of birds and within the womb of mammals
scarcely less wonderful changes are slowly but surely
effected, though they are hidden from our view. There
is no metamorphosis during the free life of the organism,
but there is a prenatal transformation. The little embryo
of a bird or mammal has no gills like the tadpole (though
it has for a while gill-slits, pointing unmistakably to its
fishy ancestry), but it has a temporary provisional
breathing organ, called the allantois, pending the full
development and functional use of its lungs.

All the higher animals, in fact — the dog, the chick, the
serpent, the frog, the fish, the lobster, the butterfly, the
worm, the star-fish, the mollusc, it matters not which we
select — take their origin from an apparently unorganized
egg. They all, therefore, pass during their growth from a
comparatively simple condition to a comparatively complex
condition by a process of change which is called develop-
ment. But there are certain lowly forms, consisting
throughout life of little more than specks of jelly-like life-
stuff, in which such development, if it occurs at all, is not
conspicuous.

6. They move about and sleep. This is true of our
familiar domestic pets. The dog and the cat, after periods
of restless activity, curl themselves up and sleep. The
canary that has all day been hopping about its cage, or
perhaps been allowed the freedom of the dining-room, tucks

8 Animal Life and Intelligence.

its head under its wing and goes to sleep. The cattle in
the meadows, the sheep in the pastures, the horses in the
stahles, the birds in the groves, all show alternating periods
of activity and repose. But is this true of all animals ?
Do all animals " move about and sleep " ? The sedentary
oyster does not move about from place to place ; the
barnacle and the coral polyp are fixed for the greater part
of life ; and whether these animals sleep or not it is very
difficult to say. We must make our statement more com-
prehensive and more accurate.

If we throw it into the following form, it will be more
satisfactory : Animals exhibit certain activities ; and
periods of activity alternate with periods of repose.

I shall have more to say hereafter concerning the
activities of animals. Here I shall only say a few words
concerning the alternating periods of repose. No organism
can continue in ceaseless activity unbroken by any inter-
vening periods of rest. Nor can the organs within an
organism, however continuous their activity may appear,
work on indefinitely and unrestfully. The heart is appa-
rently restless in its activity. But in every five minutes
of the continued action of the great force-pump (ventricle)
of the heart, two only are occupied in the efforts of con-
traction and work, while three are devoted to relaxation
and repose. What we call sleep may be regarded as the
repose of the higher brain-centres after the activity of the
day's work — a repose in which the voluntary muscles share.

The necessity for rest and repose will be readily under-
stood. We have seen that the organism is a centre of
waste and repair, of nicely balanced destructive and recon-
structive processes. Now, activity is accompanied by
waste and destruction. But it is clear that these processes,
by which the substance of the body and its organs is used
up, cannot go on for an indefinite period. There must
intervene periods of reconstruction and recuperation.
Hence the necessity of rest and repose alternating with
the periods of more or less prolonged activity.

7. They feel — " at least some of them do" The quali-

The Nature of Animal Life.

fication was a wise one, for in truth, as we shall hereafter
see, we know very little about the feelings of the lower
organisms. The one animal of whose feelings I know
anything definite and at first hand, is myself. Of course,
I believe in the feelings of others ; but when we come to
very lowly organisms, we really do not know whether
they have feelings or not, or, if they do, to what extent
they feel.

Shall we leave this altogether out of account ? Or can
we throw it into some form which is more general and less
hypothetical ? This, at any rate, we know — that all animals,
even the lowest, are sensitive to touches, sights, or sounds.
It is a matter of common observation that their activities
are generally set agoing under the influence of such sugges-
tions from without. Perhaps it will be objected that there
is no difference between feeling and being sensitive. But
I am using the word " sensitive " in a general sense — in
that sense in which the photographer uses it when he
speaks of a sensitive plate, or the chemist when he speaks
of a sensitive test. When I say that animals are sensitive,
I mean that they answer to touches, or sounds, or other
impressions (what are called stimuli) coming from without.
They may feel or not ; many of them undoubtedly do. But
that is another aspect of the sensitiveness. Using the
term, then, with this meaning, we may say, without quali-
fication, that all animals are more or less sensitive to
external influences.

8. They are made of " flesh and blood.'1 Here we have
allusion to the materials of which the animal body is com-
posed. It is obviously a loose and unsatisfactory statement
as it stands. An American is said to have described the
difference between vertebrates and insects by saying that
the former are composed of flesh and bone, and the latter of
skin and squash. But even if we amend the statement that
animals are made of " flesh and blood " by the addition of
the words, " or of skin and squash," we shall hardly have a
sufficiently satisfactory statement of the composition of the
animal body.

10 Animal Life and Intelligence.

The essential constituent of animal (as indeed also of
vegetable) tissues is protoplasm. This is a nearly colour-
less, jelly-like substance, composed of carbon, hydrogen,
nitrogen, and oxygen, with some sulphur and phosphorus,
and often, if not always, some iron ; and it is permeated
by water. Protoplasm, together with certain substances,
such as bony and horny matter, which it has the power
of producing, constitutes the entire structure of simple
organisms, and is built up into the organs of the bodies
of higher animals. Moreover, in these organs it is not
arranged as a continuous mass of substance, but is dis-
tributed in minute separate fragments, or corpuscles, only
visible under the microscope, called cells. These cells are
of very various shapes — spherical, discoidal, polyhedral,
columnar, cubical, flattened, spindle-shaped, elongated, and
stellate.

A great deal of attention has been devoted of late years
to the minute structure of cells, and the great improvements
in microscopical powers and appliances have enabled
investigators to ascertain a number of exceedingly inte-
resting and important facts. The external surface of a cell
is sometimes, but not always in the case of animals, bounded
by a film or membrane. Within this membrane the sub-
stance of the cell is made up of a network of very delicate
fibres (the plasmogen), enclosing a more fluid material (the
plasm) ; and this network seems to be the essential living
substance. In the midst of the cell is a small round or
oval body, called the nucleus, which is surrounded by a very
delicate membrane, In this nucleus there is also a net-
work of delicate plasmogen fibres, enclosing a more fluid
plasm material. At certain times the network takes the
form of a coiled filament or set of filaments, and these
arrange themselves in the form of rosettes and stars. In
the meshwork of the net or in the coils of the filament
there may be one or more small bodies (nucleoli), which
probably have some special significance in the life of the
cell. These cells multiply or give birth to new cells by
dividing into two, and this process is often accompanied

The Nature of Animal Life.

1 1

by special changes in the nucleus (which also divides) and
by the arrangement of its network or filaments into the
rosettes and stars before alluded to.

Instead, therefore, of the somewhat vague statement
that animals are made of flesh and blood, we may now sayj
that the living substance of which animals are composed!
is a complex material called protoplasm ; that organisms
are formed either of single cells or of a number of related
cells, together with certain life-products of these cells ; and

Fig. 3.— A cell, greatly magnified.

c.m., cell-membrane; c.p., cell-protoplasm ; n.m., nuclear membrane ; n.p., nuclear proto-
plasm ; n./., coiled nuclear filament.

that each cell, small as it is, has a definite and wonderful
minute structure revealed by the microscope.

9. Animals grow old and die. This is a familar obser-
vation. Apart from the fact that they are often killed by
accident, by the teeth or claws of an enemy, or by disease,
animals, like human beings, in course of time become less
active and less vigorous ; the vital forces gradually fail,
and eventually the flame of life, which has for some time
been burning dimmer and dimmer, flickers out and dies.
But is this true of all animals ? Can we say that death —
as distinct from being killed — is the natural heritage of
every creature that lives ?

12

Animal Life and Intelligence.

One of the simplest living creatures is the amoeba. It
consists of a speck of nucleated protoplasm, no larger than
a small pin's head. Simple as it is, all the essential life-
processes are duly performed. It is a centre of waste and
repair; it is sensitive and responsive to a stimulus ; respi-
ration and nutrition are effected in a simple and primitive
fashion. It is, moreover, reproductive. First the nucleus
and then the protoplasm of the cell divide, and in place of
one amoeba there are two. And these two are, so far as
we can tell, exactly alike. There is no saying which is
mother and which is daughter ; and, so far as we can see
at present, there is no reason why either should die. It is
conceivable that amoebae never die, though they may be
killed in immense numbers. Hence it has been plausibly

c.v.

n.

Fig. 4. — Amoeba.

1. An amoeba, showing the inner and outer substance (endosarc and ectosarc) ; a pseudo-
podium, p.s. ; the nucleus, n. ; and the contractile vesicle, c.v. 2. An amoeba dividing into
two. 3. The division just effected.

maintained that the primitive living cell is by nature
deathless : that death is not the heritage of all living
things ; that death is indeed an acquisition, painful indeed
to the individual, but, since it leaves the stage free for the
younger and more vigorous individuals, conducive to the
general good.

In face of this opinion, therefore, we cannot say that
all animals grow old and die ; but we may still say that
all animals, with the possible exception of some of the
lowest and simplest, exhibit, after a longer or a shorter
time, a waning of the vital energies which sooner or later
ends in death.

10. Animals reproduce their kind. We have just seen

The Nature of Animal Life. 13

the nature of reproduction in the simple unicellular amoeba.
The reproduction of the constituent cells in the complex
multicellular organism, during its natural growth or to
make good the inevitable loss consequent on the wear and
tear of life, is of the same character.

When we come to the higher organisms, reproduction
is effected by the separation of special cells called egg-cells,
or ova, from a special organ called the ovary ; and these,
in a great number of cases, will not develop into a new
organism unless they be fertilized by the union with them
in each case of another cell — the sperm-cell — produced by a
different individual. The separate parents are called male

I

Fig. 5. — Egg-cell and sperm-cell,
o, ovum or egg; &, spermatozoon or sperm.

and female, and reproduction of this kind is said to be
sexual.

The wonderful thing about this process is the power of
the fertilized ovum, produced by the union of two minute
cells from different parents, to develop into the likeness of
these parents. This likeness, however, though it extends
to minute particulars, is not absolute. The offspring is not
exactly like either parent, nor does it present a precise
mean between the characters of the two parents. There
is always some amount of individual var^iljty, the effects
of which, as we shall hereafter see, are of wide importance.
We are wont to say that these phenomena, the transmis-
sion of parental characteristics, together with a margin of

14 Animal Life and Intelligence.

difference, are due to heredity with variation. But this
merely names the facts. How the special reproductive
cells have acquired the secret of developing along special
lines, and reproducing, with a margin of variability, the
likeness of the organisms which produced them, is a matter
concerning which we can at present only make more or
less plausible guesses.

Scarcely less wonderful is the power which separated
bits of certain organisms, such as the green freshwater
hydra of our ponds, possess of growing up into the com-
plete organism. Cut a hydra into half a dozen fragments,
and each fragment will become a perfect hydra. Repro-
duction of this kind is said to be asexual.

We shall have, in later chapters, to discuss more fully
some of the phenomena of reproduction and heredity.
For the present, it is sufficient to say that animals repro-
duce their kind by the detachment of a portion of the
substance of their own bodies, which portion, in the case
of the higher animals, undergoes a series of successive
developmental changes constituting its life-history, the
special nature of which is determined by inheritance, and
the result of which is a new organism in all essential
respects similar to the parent or parents.

11. Animals are living organisms, and "not vegetables."
The first part of this final statement merely sums up the
characteristics of living animals which have gone before.
But the latter part introduces us to the fact that there are
other living organisms than those we call animals, namely,
those which belong to the vegetable kingdom.

It might, at first sight, be thought a very easy matter
to distinguish between animals and plants. There is no
chance, for example, of mistaking to which kingdom an
oak tree or a lion, a cabbage or a butterfly, belongs. But
when we come down to the simpler organisms, those whose
bodies are constituted by a single cell, the matter is by no
means so easy. There are, indeed, lowly creatures which
are hovering on the boundary-line between the two
kingdoms. We need not discuss the nature of these

The Natiire of Animal Life.

boundary forms. It is sufficient to state that unicellular
plants are spoken of as protophyta, and unicellular animals
as protozoa, the whole group of unicellular organisms being
classed together as protista. The animals whose bodies
are formed of many cells in which there is a differentiation
of structure and a specialization of function, are called
metazoa, and the multicellular plants metaphyta. The re-
lations of these groups may be thus expressed —

Animals. Plants.

Metazoa. Protozoa. Protophyta. Metaphyta.

Protista.

There are three matters with regard to the life-process
of animals and plants concerning which a few words must
be said. These are (1) their relation to food-stuffs ; (2)
their relation to the atmosphere; (3) their relation to
energy, or the power of doing work.

With regard to the first matter, that of food-relation,
the essential fact seems to be the dependence of animals
on plants. Plants can manufacture protoplasm out of its
constituents if presented to them in suitable inorganic
form scattered through earth and air and water. Hence
the peculiar features of their form, the branching and
spreading nature of those parts which are exposed to the
air, and the far-reaching ramifications of those parts
which are implanted in the earth. Hence, too, the flattened
leaves, with their large available surface. Animals^jarfi.
unable to manufacture protoplasm in this way. They
are, sooner or later, dependent for food on plant-products.
It is true that the carnivora eat animal food, but the
animals they eat are directly or indirectly consumers of
vegetable products. Plants are nature's primary producers
of organic material. ' AnimaTTlifilize these products and
carry them to higher developments.

In relation to the atmosphere, animals require a very
much larger quantity of oxygen than do plants. This,
during the respiratory process, combines with carbon so

1 6 Animal Life and Intelligence.

as to form carbonic acid gas ; and the atmosphere would
be gradually drained of its oxygen and flooded with car-
bonic acid gas were it not that plants, through their green
colouring matter (chlorophyll), under the influence of light,
have the power of decomposing the carbonic acid gas,
seizing on the carbon and building it into their tissues,
and setting free the oxygen. Thus are animals and green
plants complementary elements in the scheme of nature.*
The animal eats the carbon elaborated by the plant into
organic products (starch and others), and breathes the
oxygen which the plant sets free after it has abstracted
the carbon. In the animal's body the carbon and
oxygen recombine ; its varied activities are thus kept
going; and the resultant carbonic acid gas is breathed
forth, to be again separated by green, growing plants into
carbonaceous food-stuff and vitalizing oxygen. It must
be remembered, however, that vegetable protoplasm, like
animal protoplasm, respires by the absorption of oxygen
and the formation of carbonic acid gas. But in green
plants this process is outbalanced by the characteristic
action of the chlorophyll, by which carbonic acid gas is
decomposed.

Lastly, we have to consider the relations of animals and
plants to energy. Energy is denned as the power of doing
work, and it is classified by physicists under two modes —
potential energy, or energy of position ; and kinetic energy,
or energy of motion. The muscles of my arm contain
a store of potential energy. Suppose I pull up the weight

* An interesting problem concerning the atmosphere is suggested by
certain geological facts. In our buried coal-seams and other carbonaceous
deposits a great quantity of carbon, for the most part abstracted from the
atmosphere, has been stored away. Still greater quantities of carbon are
imprisoned, in the substance of our limestones, which contain, when pure,
44 per cent, of this element. A large quantity of oxygen lias also been taken
from the atmosphere to combine with other elements during their oxidation.
The question is — Was the atmosphere, in the geological past, more richly laden
with carbonic acid gas, of which some has entered into combination with lime
to form limestone, while some has been decomposed by plants, the carbon
being buried as coal, and the oxygen as products of oxidation? Or, has the
atmosphere been furnished with continuous fresh supplies of carbonic acid
gas?

The Nature of Animal Life. 1 7

of an old-fashioned eight-day clock. Some of the
energy of my arm is converted into the potential energy of
the weight ; that is, the raised weight is now in a position
of advantage, and capable of doing work. It has energy of
position, or potential energy. If the chain breaks, down falls
the weight, and exhibits the energy of motion. But, under
ordinary circumstances, this potential energy is utilized in
giving a succession of little pushes to the pendulum to
keep up its swing, and in overcoming the friction of the
works. Again, the energy of an electric current may be
utilized in decomposing water, and tearing asunder the
oxygen and hydrogen of which it is composed. The
oxygen and hydrogen now have potential energy, and, if
they be allowed to combine, this will manifest itself as the
light and heat of the explosion. These examples will
serve to illustrate the nature of the changes which energy
undergoes. These are of the nature of transferences of
energy from one body to another, and of transformations
from one mode or manifestation to another. The most
important point that has been established during this
century with regard to energy is that, throughout all its
transferences and transformations, it can be neither created
nor destroyed. But there is another point of great im-
portance. Transformations of energy take place more
readily in certain directions than in others. And there is
always a tendency for energy to pass from the higher or
more readily transformable to the lower or less readily
transformable forms. When, for example, energy has
passed to the low kinetic form of the uniformly distributed
molecular motion of heat, it is exceedingly difficult, or
practically impossible, to transform it into a higher and
more available form.

Now, both animals and plants are centres of the trans-
formation of energy ; and in them energy, notwithstanding
that it is being raised to a high position of potentiality, is
constantly tending to be degraded to lower forms. Hence
the necessity of some source from which fresh stores of
available energy may be constantly supplied. Such a

1 8 Animal Life and Intelligence.

source is solar radiance. This it is which gives the
succession of little pushes which keeps the pendulum of
life a-swinging. And it is the green plants which, through
their chlorophyll, are in the best position to utilize the
solar energy. They utilize it in building up, from the
necessary constituents diffused through the atmosphere
and the soil, complex forms of organic material, of which
the first visible product seems to be starch ; and these not
only contain large stores of potential energy, but are
capable, when combined with oxygen, of containing yet
larger stores. The animal, taking into its body these
complex materials, and elaborating them together with
oxygen into yet more complex and more unstable com-
pounds, then, during its vital activity, makes organized
use of the transformation of the potential energy thus
stored into lower forms of energy. Thus there go on side
by side, in both animals and plants, a building up or
synthesis of complex and unstable chemical compounds,
accompanied by a storage of potential energy, and a
breaking down or analysis of these compounds into lower
, and simpler forms, accompanied by a setting free of kinetic
energy. But in the plant, synthetic changes and storage
of energy are in excess, while in the animal, analytic
changes and the setting free of kinetic energy are more
marked. Hence the variety and volume of animal activities.
The building up of complex organic substances with
abundance of stored energy may be roughly likened to the
building up, by the child with his wooden bricks, of houses
and towers and pyramids. The more complex they become
the more unstable they are, until a touch will shatter the
edifice and liberate the stored-up energy of position
acquired by the bricks. Thus, under the influence of
solar energy, do plants build up their bricks of hydrogen,
carbon, and oxygen into complex molecular edifices.
Animals take advantage of the structures so elaborated,
modify them, add to them, and build yet more complex
molecular edifices. These, at the touch of the appropriate
stimulus, topple over and break down — not, indeed, into

The Nature of Animal Life. 19

the elemental bricks, but into simpler molecular forms, and
these again in later stages into yet simpler forms, which
are then got rid of or excreted from the body. Meanwhile
the destructive fall of the molecular edifice is accompanied
by the liberation of energy — as heat, maintaining the
warmth of the body; as visible or hidden movements, in
locomotion, for example, and the heart-beat; and some-
times as electrical energy (in electric fishes) ; as light (in
phosphorescent animals and the glow-worm), or as sound.
It is this abundant liberation of energy, giving rise to
many and complex activities, which is one of the dis-
tinguishing features of animals as compared with plants.

We have now, I trust, extended somewhat and rendered
somewhat more exact our common and familiar knowledge
of the nature of animal life. In the next chapter we will
endeavour to extend it still further by a consideration of
the process of life.

2O Animal Life and Intelligence.

CHAPTER II.

THE PROCESS OF LIFE.

IN the foregoing chapter, on " The Nature of Animal Life,"
we have seen that animals breathe, feed, grow, are sensitive,
exhibit various activities, and reproduce their kind. These
may be regarded as primary life-processes, in virtue of
which the animal characterized by them is a living
creature. We have now to consider some of these life-
processes — the sum of which we may term the process of
life — a little more fully and closely.

The substance that exhibits these life-processes is
protoplasm, which exists in minute separate masses
termed cells. It seems probable, however, that these
cells, separate as they seem, are in some cases united to
each other by minute protoplasmic filaments. In the
higher animals the cells in different parts of the body
take on different forms and perform different functions.
Like cells with like functions are also aggregated together
into tissues. Thus the surfaces of the body, external and
internal, are bounded by or lined with epithelial tissue ;
the bones and framework of the" body are composed of
skeletal tissue ; nervous tissue goes to form the brain
and nerves; contractile tissue is found in the muscles;
while the blood and lymph form a peculiar nutritive tissue.
The organs of the body are distinct parts performing
definite functions, such as the heart, stomach, or liver.
An organ may be composed of several tissues. Thus the
heart has contractile tissue in its muscular walls,
epithelial tissue lining its cavities, and skeletal tissue
forming its framework. Still, notwithstanding their aggre-

The Process of Life. 2 1

gation into tissues and organs, it remains true that the hody
of one of the higher animals is composed of cells, together
with certain cell-products, horny, calcareous, or other.
The simplest animals, called protozoa, are, however, uni-
cellular, each organism being constituted by a single cell.

We must notice that, even during periods of apparent
inactivity — for example, during sleep — many life-processes
are still in activity, though the vigour of action may be
somewhat reduced. When we are fast asleep, respiration,
the heart-beat,* and the onward propulsion of food through
the alimentary canal, are still going on. Even at rest, the
living animal is a going machine. In some cases, however,
as during the hibernating sleep of the dormouse or the
bear, the vital activities fall to the lowest possible ebb.
Moreover, in some cases, the life-processes may be tem-
porarily arrested, but again taken up when the special
conditions giving rise to the temporary arrest are removed.
Frogs, for example, have been frozen, but have resumed
their life-activities when subsequently thawed.

Let us take the function of respiration as a starting-
point in further exemplification of the nature of the
life-processes of animals.

The organs of respiration, in ourselves and all the
mammalia, are the lungs, which lie in the thoracic cavity
of the chest, the walls of which are bounded by the ribs
and breast-bone, its floor being formed of a muscular and
movable partition, the diaphragm, which separates it from
the stomach and other alimentary viscera in the abdominal
region. The lungs fit closely, on either side of the heart,
in this thoracic cavity ; and when the size of this cavity is
altered by movements of the ribs and diaphragm, air is
either sucked into or expelled from the lungs through the
windpipe, which communicates with the exterior through
the mouth or nostrils. It is unnecessary to describe

* It has before been noticed that the organs themselves have their
periods of rest. The rhythm of rest and repose in the heart is not that of
the activity and sleep of the organism, but that of the contraction and
relaxation of the organ itself.

22 Animal Life and Intelligence.

the minute structure of the lungs ; suffice it to say that,
in the mammal, they contain a vast number of tubes, all
communicating eventually with the windpipe, and terminat-
ing in little expanded sacs or bags. Around these little
sacs courses the blood in a network of minute capillary
vessels, the walls of which are so thin and delicate that
the fluid they contain is only separated from the gas
within the sacs by a film of organic tissue.

The blood is a colourless fluid, containing a great
number of round red blood-discs, which, from their minute
size and vast numbers, seem to stain it red. They may
be likened to a fleet of little boats, each capable of being
laden with a freight of oxygen gas, while the stream in
which they float is saturated with carbonic acid gas. This
latter escapes into the air-sacs as the fluid courses through
the delicate capillary tubes.

Whither goes the oxygen ? Whence comes the carbonic
acid gas? The answer to these questions is found by
following the course of the blood-circulation. The pro-
pulsion of the blood throughout the body is effected by the
heart, an organ consisting, in mammals, of two receivers
(auricles) into which blood is poured, and two powerful
force-pumps (ventricles), supplied with blood from the
receivers and driving it through great arteries to various
parts of the body. There are valves between the receivers
and the force-pumps and at the commencement of the
great arterial vessels, which ensure the passage of the
blood in the right direction. The two receivers lie side by
.side ; the two force-pumps form a single muscular mass ;
and all four are bound up into one organ; but there is,
during adult life, no direct communication between the
right and left receivers or the right and left force-pumps.

Let us now follow the purified stream, with its oxygen-
laden blood-discs, as it leaves the capillary tubes of the
lungs. It generally collects, augmented by blood from
other similar vessels, into large veins, which pour their
contents into the left receiver. Thence it passes on into
the left force-pump, by which it is propelled, through a

The Process of Life.

great arterial vessel and the numerous branches it gives
off, to the head and brain, to the body and limbs, to the
abdominal viscera ; in short, to all parts of the body
except the lungs. In all the parts thus supplied, the
vessels at length break up into a delicate capillary net-
work, so that the blood-fluid is se-
parated from the tissue-cells only
by the delicate organic film of the
capillary walls. Then the blood
begins to re-collect into larger and
larger veins. But a change has
taken place ; the blood-discs have
delivered up to the tissues their
freight of oxygen; the stream in
which they float has been charged
with carbonic acid gas. The veins
leading from various parts of the
body converge upon the heart and
pour their contents into the right
receiver; thence the blood passes
into the right force-pump, by which
it is propelled, by arteries, to the i.OeVtTemridT; ~a.r^pm^r

r £ ' J plexus of the head ; S., capillary

lUngS. There the blOOd-dlSCS are plexusofthebody;A.C'.>alimentary

7 . canal; Lr., liver ; R.A., right auricle

again laden with oxygen, the stream °f the heart ; R- T- risht ventricle ;
is again purified of its carbonic acid

gas, and the blood proceeds on its course, to renew the /
cycle of its circulation. *

Now, if we study the process of respiration and that of
circulation, with which it is so closely associated, in other
forms of life, we shall find many differences in detail.
In the bird, for example, the mechanism of respiration is
different. There is no diaphragm, and the lungs are
scarcely distensible. There are, however, large air-sacs in
the abdomen, in the thoracic region, in the fork of the
merry-thought, and elsewhere. These are distensible, and
to reach them the air has to pass through the lungs, and
as it thus passes through the delicate tubes of the lungs, it
supplies the blood with oxygen and takes away carbonic

Fig. 6. — Diagram of circu-
lation.
L.A., left auricle of the heart;

24 Animal Life and Intelligence.

acid gas. In the frog there is no diaphragm, and there
are no ribs. The lungs are hollow sacs with honey-combed
sides, and they are inflated from the mouth, which is
used as a force-pump for this purpose. In the fish there
are no lungs, respiration being effected by means of gills.
In these organs the blood is separated from the water
which passes over them (being gulped in by the mouth
and forced out between the gill-covers) by only a thin
organic film, so that it can take up the oxygen dissolved in
the water, and give up to the water the carbonic acid it
contains. In fishes, too, we have only one receiver and
one force-pump, the blood passing through the gills on its
way to the various parts of the body. In the lobster, again,
there are gills, but the mechanism by which the water is
drawn over them is quite different, and the blood passes
through them .on its way to the heart, after passing
through the various organs of the body, not on its way
from the heart, as in vertebrate fishes. The blood, too,
has no red blood-discs. In the air-breathing insects the
mechanism is, again, altogether different. The air, which
obtains access to the body by spiracles in the sides (see
Fig. 1, p. 3), is distributed by delicate and beautiful tubes
to all parts of the organs ; so that the oxygen is supplied
to the tissues directly, and not through the intervention of
a blood-stream. In the earthworm, on the other hand,
there is a distributing blood-stream, but there is no
mechanism for introducing the air within the body ; while
in some of the lowliest forms of life there is neither any
introduction of air within the body nor any distribution
by means of a circulating fluid. Beginning, therefore,
with the surface of the body simply absorbent of oxygen,
we have the concentration of the absorbent parts in special
regions, and an increase in the absorbent surface, either
(1) by the pushing out of processes into the surrounding
medium, as in gills; or (2) by the formation of internal
cavities, tubes, or branching passages, as in lungs and the
tracheal air-system of insects.

What, then, is the essential nature of the respiratory

The Process of Life. 25

process thus so differently manifested ? Clearly the
supply of oxygen to the cellular tissue-elements, and,
generally closely associated with this, the getting rid of
carbonic acid gas.

Jjet us now glance at the life-processes which minister
to -nutrition, beginning, as before, with the mode in which
these processes are effected in ourselves..

The alimentary canal is a long tube running through
the body from the mouth to the vent. In the abdominal
region it is coiled upon itself, so that its great length may
be conveniently packed away. Opening into this tube are
the ducts of certain glands, which secrete fluids which aid
in the digestion of the food. Into the mouth there open
the ducts of the salivary glands, which secrete the saliva ;
in the stomach there are a vast number of minute gastric
glands ; in the intestine, besides some minute tubular
glands, there are the ducts of the large liver (which
secretes the bile) and the pancreas, or sweetbread. Since,
with the exception of the openings of these ducts, th'e
alimentary canal is a closed tube, its contents, though
tying within the body, are in a sense outside it, just as the
fuel in a tubular boiler, though within the boiler, is really
outside it. The organic problem, therefore, is how to get
the nutritive materials through the walls of the tube and
thus into the body.

At an ordinary meal we are in the habit of consuming
a certain amount of meat, with some fat, together with
bread and potatoes, and perhaps some peas or beans and
a little salt. This is followed by, say, milky rice-pudding,
with which we take some sugar; and a cheese course
may, perhaps, be added. The whole is washed down with
water more or less medicated with other fluid materials.
Grouping these substances, there are (1) water and salts,
including calcium phosphate in the milk ; (2) meat, peas,
milk, and cheese, all of which contain albuminous or allied
materials ; (3) bread, potatoes, and rice, which contain
starchy matters ; and here we may place the sugar ; (4)
fat, associated with the meat or contained in the cream of

26 Animal Life and Intelligence.

the milk. Now, of all the materials thus consumed, only
the water, salts, and sugar are capable, in their unaltered
condition, of passing through the lining membrane of the
alimentary canal, and thus of entering the body. The
albuminous materials, the starchy matter, and the fat —
that is to say, the main elements of the food — are, in their
raw state, absolutely useless for nutritive purposes.

The preparation of the food begins in the mouth. The
saliva here acts upon some of the starchy matter, and
converts it into a kind of sugar, which can pass through
the lining membrane of the alimentary canal, and thus
enter the body. The fats and albuminous matters here
remain unaltered, though they are torn to pieces by the
mastication effected by the teeth. In the stomach the
albuminous constituents of the meat are attacked by
the gastric juice and converted into peptones ; and in this
new condition they, too, can soak through the lining
membrane of the alimentary canal, and thus can enter the
body. In the stomach all action on starch is arrested;
but in the intestine, through the effect of a ferment
contained in the pancreatic juice, this action is resumed,
and the rest of the starch is converted into absorbable
sugar. Another principle contained in pancreatic juice
takes effect on the albuminous matters, and converts them
into absorbable peptones. The pancreatic juice also acts
on the fats, converting them into an emulsion, that is to
Bay, causing them to break up into exceedingly minute
globules, like the butter globules in milk. It furthermore
contains a ferment which splits up the fats into fatty acids
and glycerine; and these fatty acids, with an alkaline
carbonate contained in small quantities in pancreatic juice,
form soluble soaps, which further aid in emulsifying fats.
The bile also aids in emulsifying fats.

The effect, then, of the various digestive fluids upon
the food is to convert the starch, albuminous material,
and fat into sugar, peptones, glycerine, and soap, and thus
render them capable of passing through the lining mem-
brane of the canal into the body.

The Process of Life. 27

The materials thus absorbed are either taken up into
the blood-stream or pass into a separate system of vessels
called laeteals. All the blood which comes away from the
alimentary canal passes into the liver, and there undergoes
a good deal of elaboration in that great chemical labora-
tory of the body. The fluid in the laeteals passes through
lymphatic glands, in which it too undergoes some elabora-
tion before it passes into the blood-stream by a large vessel
or duct.

Thus the blood, which we have seen to be enriched with
oxygen in the lungs, is also enriched with prepared nutri-
tive material through the processes of digestion and absorp-
tion in the alimentary organs and elaboration in the liver
and lymphatic glands.

Here let us again notice that the details of the process
of nutrition vary very much in different forms of life. In
some mammals the organs of digestion are specially fitted
to deal with a flesh diet ; in others they are suited for a
diet of herbs. In the graminivorous birds the grain is
swallowed whole, and pounded up in the gizzard. The
leech swallows nothing but blood. The earthworm pours
out a secretion on the leaves, by which they are partially
digested before they enter the body. Many parasitic
organisms have no digestive canal, the nutritive juices of
their host being absorbed by the general external surface
of the body. But the essential life-process is in all cases
the same — the absorption of nutritive matter to be supplied
to the cell or cells of which the organism is built up.

Thus in the mammal the blood, enriched with oxygen
in the lungs, and enriched also with nutritive fluids, is
brought, in the course of its circulation, into direct or
indirect contact with all the myriads of living cells in the
body.

In the first place, the material thus supplied is utilized
for and ministers to the growth of the organs and tissues.
This growth is effected by the multiplication of the con-
stituent cells. The cells themselves have a very limited
power of growth. But, especially in the early stages of

28 Animal Life and Intelligence.

the life of the organism, when well supplied with nutri-
ment, the cells multiply rapidly, by a process of fission,
or the division of each cell into two daughter cells. The
first part of the cell to divide is the nucleus, the proto-
plasmic network of which shows, during the process, curious
and interesting arrangements and groupings of the fibres.
When the nucleus has divided, the surrounding protoplasm
is constricted, and separates into two portions, each of
which contains a daughter nucleus.

In addition to the multiplication of cells, there is the
formation, especially during periods of growth, of certain
products of cell-life and cell-activity. Bone, for example,
is a more or less permanent product of the activity of
certain specialized cells.

There is, perhaps, no more wonderful instance of rapid
and vigorous growth than the formation of the antlers of
deer. These splendid weapons and adornments are shed
and renewed every year. In the spring, when they are
growing, they are covered over with a dark skin provided
with short, fine, close-set hair, and technically termed "the
velvet." If you lay your hand on the growing antler, you
will feel that it is hot with the nutrient blood that is
coursing beneath it. It is, too, exceedingly sensitive and
tender. An army of tens of thousands of busy living cells
is at work beneath that velvet surface, building the bony
antlers, preparing for the battles of autumn. Each minute
cell knows its work, and does it for the general good — so
perfectly is the body knit into an organic whole. It takes
up from the nutrient blood the special materials it requires ;
out of them it elaborates the crude bone-stuff, at first soft
as wax, but ere long to become as hard as stone ; and then,
having done its work, having added its special morsel to
the fabric of the antler, it remains embedded and immured,
buried beneath the bone-products of its successors or
descendants. No hive of bees is busier or more replete
with active life than the antler of a stag as it grows
beneath the soft, warm velvet. And thus are built up in
the course of a few weeks those splendid "beams," with

The Process of Life. 29

their " tynes " and "snags," which, in the case of the
wapiti, even in the confinement of our Zoological Gardens,
may reach a weight of thirty-two pounds, and which, in
the freedom of the Kocky Mountains, may reach such a
size that a man may walk, without stooping, beneath the
archway made by setting up upon their points the shed
antlers. When the antler has reached its full size, a cir-
cular ridge makes its appearance at a short distance from
the base. This is the " burr," which divides the antler
into a short "pedicel" next the skull, and the "beam"
with its branches above. The circulation in the blood-
vessels of the beam now begins to languish, and the velvet
dies and peels off, leaving the hard, dead, bony substance
exposed. Then is the time for fighting, when the stags
challenge each other to single combat, while the hinds
stand timidly by. But when the period of battle is over,
and the wars and loves of the year are past, the bone
beneath the burr begins to be eaten away and absorbed,
through the activity of certain large bone-eating cells, and,
the base of attachment being thus weakened, the beautiful
antlers are shed ; the scarred surface skins over and heals,
and only the hair-covered pedicel of the antler is left.*

Not only are there these more or less permanent
products of cell-activity which are built up into the
framework of the body ; there are other products of a
less enduring, -but, in the case of some of them, not less
useful character. The secretions, for example, which, as
we have seen, minister in such an important manner to
nutrition, are of this class. The salivary fluids, the gastric
juice, the pancreatic products, and the bile, — all of these
are products of cell-life and cell-activity. And then there
are certain products of cell-life which must be cast out
from the body as soon as possible. These are got rid of
in the excretions, of which the carbonic acid gas expelled
in the lungs and the waste-products eliminated through
the kidneys are examples. They are the ultimate organic

* From a popular article of the author's on " Horns and Antlers," in
Atalanta.

3<D Animal Life and Intelligence.

products of the combustion that takes place in the
muscular, nervous, and other tissues.

The animal organism has sometimes been likened to
a steam-engine, in which the food is the fuel which enters
into combustion with the oxygen taken in through the
lungs. It may be worth while to modify and modernize
this analogy — always remembering, however, that it is an
analogy, and that it must not be pushed too far.

In the ordinary steam-engine the fuel is placed in the
fire-box, to which the oxygen of the air gains access ; the
heat produced by the combustion converts the water in
the boiler into steam, which is made to act upon the
piston, and thus set the machinery in motion. But there
is another kind of engine, now extensively used, which
works on a different principle. In the gas-engine the fuel
is gaseous, and it can thus be introduced in a state of
intimate mixture with the oxygen with which it is to unite
in combustion. This is a great advantage. The two can
unite rapidly and explosively. In gunpowder the same
end is effected by mixing the carbon and sulphur with
nitre, which contains the oxygen necessary for their explo-
sive combustion. And this is carried still further in dyna-
mite and gun-cotton, where the elements necessary for
explosive combustion are not merely mechanically mixed,
but are chemically combined in a highly unstable com-
pound.

But in the gas-engine, not only is the fuel and the
oxygen thus intimately mixed, but the controlled explo-
sions and the resulting condensation are caused to act
directly on the piston, and not through the intervention
of water in a boiler. Whereas, therefore, in the steam-
engine the combustion is to some extent external to the
working of the machine, in the gas-engine it is to a large
extent internal and direct.

Now, instead of likening the organism as a whole to
a steam-engine, it is more satisfactory to liken each cell
to a gas-engine. We have seen that the cell-substance
around the nucleus is composed of a network of proto-

The Process of Life. 31

plasm, the plasmogen, enclosing within its meshes a more
fluid material, the plasm. It is probable that this more
fluid material is an explosive, elaborated through the vital
activity of the protoplasmic network. During the period
of repose which intervenes between periods of activity, the
protoplasmic network is busy in construction, taking from
the blood-discs oxygen, and from the blood-fluid carbona-
ceous and nitrogenous materials, and knitting these
together into relatively unstable explosive compounds.
These explosive compounds are like the mixed air and gas
of the gas-engine. A rested muscle may be likened to a
complex and well-organized battery of gas-engines. On
the stimulus supplied through a nerve-channel a series of
co-ordinated explosions takes place : the gas-engines are set
to work ; the muscular fibres contract ; the products of the
explosions (one of which is carbonic acid gas) are taken
up and hurried away by the blood-stream ; and the proto-
plasm sets to work to form a fresh supply of explosive
material. Long before the invention of the gas-engine, long
before gun-cotton or dynamite were dreamt of, long before
some Chinese or other inventor first mixed the ingre-
dients of gunpowder, organic nature had utilized the
principle of controlled explosions in the protoplasmic cell.

Certain cells are, however, more delicately explosive
than others. Those, for example, on or near the external
surface of the body — those, that is to say, which constitute
the end organs of the special senses — contain explosive
material which may be fired by a touch, a sound, an
odour, the contact with a sapid fluid or a ray of light.
The effects of the explosions in these delicate cells, rein-
forced in certain neighbouring nerve-knots (ganglionic
cells), are transmitted down the nerves as along a fired
train of gunpowder, and thus reach that wonderful aggre-
gation of organized and co-ordinated explosive cells, the
brain. Here it is again reinforced and directed (who, at
present, can say how ?) along fresh nerve-channels to
muscles, or glands, or other organized groups of explosives.
And in the brain, somehow associated with the explosion

32 Animal Life and Intelligence.

of its cells, consciousness and the mind-element emerges ;
of which we need only notice here that it belongs to a
wholly different. order of being from the physical activities
and products with which we are at present concerned.

No analogies between mechanical contrivances and
organic processes can be pushed very far. To liken the
organic cell to a gas-engine is better than to liken the
organism to a steam-engine, because it serves to indicate
the fact that the fuel does not simply combine with the
oxygen in combustion, but that an unstable or explosive
combination of "fuel" and oxygen is first formed; and
again, because the effect of this is direct, and not through
the intervention of any substance to which the combustion
merely supplies the necessary heat. But beyond the fact
that a kind of explosive is formed which, like a fulminating
compound, can be fired by a touch, there is no very close
analogy to be drawn. Nor must we press the explosion
analogy too far. The essential thing would seem to be
this — which, perhaps, the analogy may have served to
lead up to — that the vital protoplasmic network of the
cell has the power of building up complex and unstable
chemical compounds, which are probably stored in the
plasm within the spaces between the threads of the net-
work; and that these unstable compounds, under the
influence of a stimulus (or, possibly, sometimes sponta-
neously) break down into simpler and more stable com-
pounds.*/In the case of muscle-cells, this latter change
is accompanied by an alteration in length of the fibres
and consequent movements in the organism, the products
of the disruptive change being useless or harmful, and
being, therefore, got rid of as soon as possible. But very

* It will be well here to introduce the technical terms for these changes.
The general term for chemical actions occurring in the tissues of a living
creature is metabolism ; where the change is of such a nature that complex
and unstable compounds are built up and stored for a while, it is called
anabolism ; where complex unstable compounds break up into less complex
and relatively stable compounds, the term katabolism is applied. "We shall
speak of anabolic changes as constructive ; katabolic, as disruptive, or some-
times, explosive.

The Process of Life. 33

frequently the products of explosive activity are made use
of. In the case of bone-cells, one of the products of
disruption is of permanent use to the organism, and
constitutes the solid framework of the skeleton. In the
case of the secreting cells of the salivary and other diges-
tive glands, one of the disruptive products is of temporary
value for the preparation of the food. It is exceedingly
probable that these useful products of disruption, perma-
nent or temporary, took their origin in waste products for
which natural selection has found a use, and which have
been, through natural selection, rendered more and more
efficacious. This, however, is a question we are not at
present in a position to discuss.

In the busy hive of cells which constitutes what we
call the animal body, there is thus ceaseless activity.
During periods of apparent rest the protogen filaments
of the cell -net are engaged in constructive work, building
up fresh supplies of complex and unstable materials,
which, during periods of apparent activity, break up into
simpler and more stable substances, some of which are
useful to the organism while others must be got rid
of as soon as possibleu From another point of view, the
cells during apparent rest are storing up energy which
is utilized by the organism during its periods of activity.
The storing up of available energy may be likened to the
winding up of a watch or clock ; it is during apparent rest
that the cell is winding itself up ; and thus we have the
apparent paradox that the cell is most active and doing
most work when it is at rest. During the repose of an
organ, in fact, the cells are busily working in preparation
for the manifestation of energetic action that is to follow.
Just as the brilliant display of intellectual activity in a
great orator is the result of the silent work of a lifetime,
so is the physical manifestation of muscular power the
result of the silent preparatory work of the muscle-cells.*

One point to be specially noted is the varied activity

* I do not mean, of course, to imply that there is no reconstruction during
activity, but that it is then distinctly outbalanced by disruptive changes.

D

34 Animal Life and Intelligence.

of the cells. While they are all working for the general
good of the organism, they are divided into companies, each
with a distinct and definite kind of work. This is known
as the physiological division of labour. It is accompanied
by a morphological differentiation of structure. By the
form of a cell, therefore, we can generally recognize the
kind of work it has to perform. The unstable compounds
produced by the various cells must also be different,
though not much is known at present on this subject.
The unstable compound which forms bone and that which
forms the salivary ferment, the unstable matter elaborated
by nerve-cells and that built up by muscle-cells, are in
all probability different in their chemical nature. Whether
the formative plasmogen from which these different sub-
stances originate is in all cases the same or in different
cases different, we do not know.

It may, perhaps, seem strange that the products of
cellular life should be reached by the roundabout process
of first producing a very complex substance out of which
is then formed a less complex substance, useful for per-
manent purposes, as in bone, or temporary purposes, as
in the digestive fluids. It seems a waste of power to build
up substances unnecessarily complex and stored with an
unnecessarily abundant supply of energy. Still, though
we do not know that this course is adopted in all cases,
there is no doubt that it is adopted in a great number of
instances. And the reason probably is that by this method
the organs are enabled to act under the influence of
stimuli. They are thus like charged batteries ready to
discharge under the influence of the slightest organic touch.
In this way, too, is afforded a means by which the organ
is not dependent only upon the products of the immediate
activity of the protoplasm at the time of action, but can
utilize the store laid up during a considerable preceding
period.

Sufficient has now been said to illustrate the nature
of the process of life. The fact that I wish to stand out
clearly is that the animal body is stored with large

The Process of Life. 35

quantities of available energy resident in highly complex
and unstable chemical compounds, elaborated by the
constructive energy of the formative protoplasm of its
constituent cells. These unstable compounds, eminently
explosive according to our analogy, are built up of materials
derived from two different sources — from the nutritive
matter (containing carbon, hydrogen, and nitrogen)
absorbed in the digestive organs, and from oxygen taken
up from the air in the lungs. The cells thus become
charged with energy that can be set free on the application
of the appropriate stimulus, which may be likened to the
spark that fires the explosive.

Let us note, in conclusion, that it is through the blood-
system, ramifying to all parts of the body, and the nerve-
system, the ramifications of which are not less perfect,
that the larger and higher organisms are knit together into
an organic whole. The former carries to the cell the raw
materials for the elaboration of its explosive products,
and, after the explosions, carries off the waste products
which result therefrom. The nerve-fibres carry the stimuli
by which the explosive is fired, while the central nervous
system organizes, co-ordinates, and controls the explosions,
and directs the process of reconstruction of the explosive
compounds.

36 Animal Life and Intelligence.

CHAPTER III.

REPRODUCTION AND DEVELOPMENT.

WE have now to turn to a fresh aspect of animal life,
that of reproduction ; and it will be well to connect this
process as closely as possible with the process of life in
general, of which it is a direct outcome.

It will be remembered that, in the last chapter, it was
shown that the essential feature in the process of life is
the absorption by living protoplasm of oxygen on the one
hand and nutritive matter on the other hand, and the
kneading of these together, in subtle metabolism, into
unstable compounds, which we likened to explosives. This
is the first, or constructive, stage of the life-process.
Thereupon follows the second, or disruptive, stage. The un-
stable compounds break down into more stable products, —
they explode, according to our analogy ; and accompanying
the explosions are manifestations of motor activity — of heat,
sometimes of light and electrical phenomena. But in the
economy of nature the products of explosion are often
utilized, and in the division of labour among cells the
explosions of some of them are directed specially to the
production of substances which shall be of permanent or
temporary use — for digestion, as in the products of the
salivary, gastric, and intestinal glands ; for support, as in
bone, cartilage, and skeletal tissue generally ; or as a
store of nutriment, in fat or yolk. The constructive pro-
ducts of protoplasmic activity seem for the most part to be
lodged in the spaces between the network of formative
protoplasm. The disruptive products — those of them, that
is to say, which are of temporary or permanent value to

Reproduction and Development. 37

the organism — accumulate either within the cell, some-
times at one pole, sometimes at the centre, as in the case
of the yolk of eggs, or around the cell, as in the case of
cartilage or bone.

Apart from and either preceding or accompanying
these phenomena, is the growth or increase of the forma-
tive protoplasm itself; concerning which the point to be
here observed is that it is not indefinite, but limited.
This was first clearly enunciated by Herbert Spencer, and
may be called Spencer's law. In simplest expression it
may thus be stated : Volume tends to outrun surface. Take
a cube measuring one inch in the side ; its volume is one
cubic inch, its surface six square inches. Eight such cubes
will have a surface of (6 x 8) forty-eight square inches.
But let these eight be built into a larger cube, two inches
in the side, and it will be found that the surface exposed is
now only twenty-four square inches. While the volume
has been increased eight times, the surface has been
increased only four times. With increase of size, volume
tends to outrun surface. But in the organic cell the
nutritive material and oxygen are absorbed at the surface,
while the explosive changes occur throughout its mass.
Increase of size, therefore, cannot be carried beyond certain
limits, for the relatively diminished surface is unable to
supply the relatively augmented mass with material for
elaboration into unstable compounds. Hence the cell
divides to afford the same mass increased surface. This
process of cell-division is called fission, and in some cases
cleavage.

We will now proceed to pass in review the phenomena
of reproduction and development in animals.

Attention has already been drawn to the difference
between those lowly organisms, each of which is composed
of a single cell — the protozoa, as they are termed — and
those higher organisms, called metazoa, in which there
are many cells with varied functions. Confining our
attention at first to the former group of unicellular animals,
we find considerable diversities of form and habit, from

Animal Life and Intelligence.

the relatively large, sluggish, parasitic Gregarina, to the
active slipper-animalcule, or Paramcecium, or the beautiful,
stalked bell-animalcule, or Vorticella / and from the small,
slow-moving amoeba to the minute, intensely active monad.
In many cases reproduction is by simple fission, as in the
amoeba, where the nucleus first undergoes division; and
then the whole organism splits into two parts, each with
its own nucleus. In other cases, also numerous, the

E- .^-iPfrT

A.

Fig. 7.— Protozoa.

A, vorticella extended. B, the same contracted. C, D, monads. E, amceba. F, Para-
mctcium. G, Gregarina. c.f., contractile fibre ; c.v., contractile vesicle ; <i.,disc ; end., endo-
plast ; f.v., food-vacuole ; fl., flagellum ; gu., gubernaculum ; n., nucleus ; p.a., potential anus ;
p*., (in A) peristome, (in E) pseudopodium ; vt., vestibule.

organism passes into a quiescent state, and becomes sur-
rounded with a more or less toughened cyst. The nucleus
then disappears, and the contents of the cyst break up
into a number of small bodies or spores. Eventually the
cyst bursts, and the spores swarm forth. In the case of
some active protozoa the minute creatures that swarm forth
are more or less like the parent ; but .in the more sluggish
kinds the minute forms are more active than the parent.
Thus in the case of the gregarina, the minute spore-
products are like small amoebse ; while in other instances

Reproduction and Development. 39

the embryos, if so we may call them, have a whip-like
cilium like the monads.

Very frequently, however, there is, in the protozoa, a
further process, which would seem to be intimately
associated with fission or the formation of spores, as the
case may be. This is known as conjugation. Among
monads, for example, two individuals may meet together,
conjugate, and completely fuse the one into the other. A
triangular cyst results. After a while, the cyst bursts, and
an apparently homogeneous fluid escapes. The highest
powers of the microscope fail to disclose in it any germ of
life ; and there, at first sight, would seem to be an end of
the matter. But wait and watch ; and there will appear
in the field of the microscope, suddenly and as if by magic,
countless minute points, which prolonged watching shows
to be growing. And when they have further grown, each
distinct point is seen to be a monad.

In the slipper-animalcule, conjugation is temporary.
But during the temporary fusion of the two individuals
important changes are said to occur. In these infusorians
there is, beside the nucleus, a smaller body, the paranu-
cleus. This, in the case of conjugating pararnoacia, appears
to divide into two portions, of which one is mutually ex-
changed. Thus when two slipper-animalcules are in con-
jugation, the paranucleus of each breaks into two parts, a
and 6, of which a is retained and b handed over in exchange.
The old a and the new b then unite, and each paramoecium
goes on its separate way. M. Maupas, who has lately
reinvestigated this matter, considers, as the result of his
observations on another infusorian (Stylonichia) , that
without conjugation these organisms become exhausted,
and multiplication by fission comes to a standstill. If this
be so, conjugation is, in these organisms, necessary for the
continuance of the race. But Eichard Hertwig has recently
shown that this is, at any rate, not universally true.

In the bell-animalcule, fission takes place in such a
manner as to divide the bell into two equal portions.
Thus there are two bells to one stalk. But the fate of the

4O Animal Life and Intelligence.

two is not the same. One remains attached to the stalk,
and expands into a complete vorticella. The other remains
pear-shaped, and develops round the posterior region of
the body a girdle of powerful vibratile cilia, by the lashing
of which the animalcule tears itself away from the parent
stem, and swims off through the water. After a short
active existence, it settles down in a convenient spot,
adhering by its posterior extremity. The hinder girdle of
cilia is lost or absorbed, a stalk is rapidly developed, and
the organism expands into a perfect vorticella.

In some cases, however, the fission is of a different
character, with different results. It may be very unequal,
so that a minute, free-swimming animalcule is disengaged ;
or minute animalcules may result by repetition of division.
In either case the minute form conjugates with an ordinary
vorticella, its smaller mass being completely merged in the
larger volume of its mate.

There are, of course, many variations in detail in the
modes of protozoan reproduction ; but we may say that,
omitting such details, reproduction is either by simple
fission or by spore-formation; and that these processes
are in some cases associated with, and perhaps dependent
on, the temporary or permanent union of two individuals
in conjugation.

It is essential to notice that the results of fission or of
spore-formation separate, each going on its own way. Hence
such development as we find in the protozoa results from
differentiations within the limits of the single cell. Thus
the bell-animalcule has a well-defined and constant form ;
a definite arrangement of cilia round the rim and in the
vestibule by which food finds entrance to the body. The
outer layer of the body forms a transparent cuticle, beneath
which is a so-called "myophan " layer, continuous with a
contractile thread in the stalk. Within the substance of
the body is a pulsating cavity, or contractile vesicle, and a
nucleus. Such is the nature of the differentiation which
may go on within the protozoan cell.

When we pass to the metazoa, we find that the method

Reproduction and Development. 41

of differentiation is different. These organisms are com-
posed of many cells ; and instead of the parts of the cell
differentiating in several directions, the several cells differ-
entiate each in its own special direction. This is known
as the physiological division of labour. The cells merge
their individuality in the general good of the organism.
Each, so to speak, cultivates some special protoplasmic
activity, and neglects everything else in the attainment of
this end. The adult metazoan, therefore, consists of a!,
number of cells which have diverged in several, sometimes
many, directions.

In some of the lower metazoans, reproduction may be
effected by fission. Thus the fresh-water hydra is said to
divide into two parts, each of which grows up into a perfect
hydra. It is very doubtful, however, whether this takes
place normally in natural life. But there is no doubt that
if a hydra be artificially divided into a number of special
pieces, each will grow up into a perfect organism, so long
as each piece has fair samples of the different cells which
constitute the body-wall. Sponges and sea-anemones may
also be divided and subdivided, each part having the power
of reproducing the parts that are thus cut away. When
a worm is cut in half by the gardener's spade, the head
end grows a new tail ; and it is even stated that a worm
not only survived the removal of the first five rings, in-
cluding the brain, mouth, and pharynx, but within fifty-
eight days had completely regenerated these parts.

Higher up in the scale of metazoan life, animals have
the power of regenerating lost limbs. The lobster that
has lost a claw reproduces a new one in its stead. A snail
will reproduce an amputated "horn," or tentacle, many
times in succession, reproducing in each case the eye, with
its lens and retina. Even a lizard will regenerate a lost
tail or a portion of a leg. In higher forms, regeneration
is restricted to the healing of wounds and the mending of
broken bones.

Closely connected with this process of regeneration of
lost parts is the widely prevalent process of reproduction

42 Animal Life and Intelligence.

by budding. The cut stump of the amputated tentacle of
the hydra or the snail buds forth a new organ. But in the
hydra, during the summer months, under normal circum-
stances, a bud may make its appearance and give rise to
a new individual, which will become detached from the
parent, to lead a separate existence. In other organisms
allied to the hydra the buds may remain in attachment,
and a colony will result. This, too, is the result of budding
in many of the sponges. In some worms, too, budding
may occur. In the fresh-water worm (Chtetogaster limncei)
the animal, as we ordinarily see it, is a train of individuals,
one budded off behind the other— the first fully developed,
those behind it in various stages of development. The
individuals finally separate by transverse division. Another
more lowly worm (Microstomum lineare, a Turbellarian) may
bud off in similar fashion a chain of ten or fifteen indi-
viduals. In these cases budding is not far removed from
fission.

Now, in the case of reproduction by budding, as in the
hydra, a new individual is produced from some group of cells
in the parent organism. From this it is but a step — a step,
however, of the utmost importance — to the production of
a new individual from a single cell from the tissues of the
parental organism. Such a reproductive cell is called an
egg-cell, or ovum. In the great majority of cases, to enable
the ovum to develop into a new individual, it is necessary
that the egg-cell should conjugate or fuse with a minute,
active sperm-cell, generally derived from a different parent.
This process of fusion of germinal cells is called fertiliza-
tion (see Fig. 5, p. 13).

In sponges, the cells which become ova or sperms lie
scattered in the mid-layer between the ciliated layers which
line the cavities and spaces of the organism. Sometimes
the individual sponge produces only ova ; sometimes only
sperms ; sometimes both, but at different periods. The
cells which become ova increase in size, are passive, and
rich in reserve material elaborated by their protoplasm.
The cells which become sperms divide again and again,

Reproduction and Development.

43

and thus produce minute active bodies, adance with rest-
less motion. These opposite tendencies are repeated and ]
emphasized throughout the animal kingdom — ova relatively \
large, passive, and accumulative of reserve material; \
sperms minute, active, and the result of repeated fission. \
The active sperm, when it unites with the ovum, imports
into it a tendency to fission, or cleavage ; but the resulting
cells do not part and scatter — they remain associated
together, and in mutual union give rise to a new sponge.

In the hydra, generally near the foot or base of attach-
ment, a rounded swelling often makes its appearance in

' Fig. 8.— Hydra viridis.

A, hydra half retracted, with a bud and an ovum attached to the shrunken ovary ; B, a
small hydra firmly retracted; C, a hydra fully extended. &., bud; /., foot; h.s., hypostome;
own., ovum ; ovy., ovary ; t., tentacles ; ts.t testis.

autumn. Within this swelling one central cell increases
enormously at the expense of the others. It becomes an
ovum. Eventually it bursts through the swelling, but
remains attached for a time. Earely in the same hydra,
more frequently in another, one or two swellings may be
seen higher up, beneath the circle of tentacles. Within
these, instead of the single ovum may be seen a swarm of
sperms, minute and highly active. When these are dis-
charged, one may fuse with and fertilize an ovum, occa-
sionally in the same, but more frequently in another
individual, with the result that it develops into a new
hydra. Here there are definite organs — an ovary and a

44 Animal Life and Intelligence.

testis — producing the ova or the sperms. But they are
indefinite and not permanent in position.

In higher forms of life the organs which are set apart
for the production of ova or sperms become definite in
position and definite in structure. Occasionally, as in the
snail, the same organ produces both sperms and ova, but
then generally in separate parts of its structure. The two
products also ripen at different times. Not infrequently,
as in the earthworm, each individual has both testes and
ovaries, and thus produces both ova and sperms, but from
different organs. The ova of one animal are, however,
fertilized by sperms from another. But in the higher
invertebrates and vertebrates there is a sex-differentiation
among the individuals, the adult males being possessed of
testes only and producing sperms, the adult females pos-
sessed of ovaries only and producing ova. There are also,
in many cases, accessory structures for ensuring that the
ova shall be fertilized by sperms, while sexual appetences
are developed to further the same end. But however the
matter may thus be complicated, the essential feature is
the same — the union of a sluggish, passive cell, more or
less laden with nutritive matter, with a minute active cell
with an hereditary tendency to fission.*

It is not, however, necessary in all cases that fertiliza-
tion of the ovum should take place. The plant-lice, or
Aphides of our rose trees, may produce generation after

* Professor Geddes and Mr. J. Arthur Thomson, in their interesting work
on " The Evolution of Sex," regard the ovum in especial, and the female in
general, as preponderatingly anabolic (s^-e note, p. 32) ; while the sperm in
especial, and the male in genera!, are on their view preponderatingly katabolic.
Kegarding, as I do, the food-yolk as a katubolic product, I cannot altogether
follow them. Thed;fferentiation seems to me to have taken place along diver-
gent lines of katabolism. In the ovum, katabolism has given rise to storage
products; in the sperm, to motor activities associated with a tendency to
fission. The contrast is not between anabolic and katabolic tendencies, but
between storage katabolism and motor katabolism. Nor do I think that " the
essentially katabolic male-cell brings to the ovum a supply of characteristic
waste products, or katastates, which stimulate the latter to division " (I.e., p.
lt;2). I believe that it brings an inherited tendency to fission, and thus
reiutroduces into the fertilized ovum the teudem-y which, as ovum, it had
renounced in favour of storage katabolism.

Reproduction and Development. 45

generation, and their offspring in turn reproduce in like
manner, without any union or fusion of ovum or sperm.
The same is true of the little water-fleas, or Daphnids ;
while in some kinds of rotifers fertilization is said never
to occur. It is a curious and interesting fact, which seems
now to be established beyond question, that drone bees are
developed from unfertilized ova, the fertilized ova pro-
ducing either queens or workers, according to the nature of
the food with which the grubs are supplied. Where, as in
the case of aphids and daptmids, fertilization occasionally
takes place, it would seem that lowered temperature and
diminished food -supply are the determining conditions.
Fertilization, therefore, generally takes place in the
autumn ; the fertilized ovum living on in a quiescent state
during the winter, and developing with the warmth of the
succeeding spring. In the artificial summer of a green-
house, reproduction may continue for three or four years
without the occurrence of any fertilization.

Mention may here be made of some peculiarly modified
modes of reproduction among the metazoa. The aurelia
is a well-known and tolerably common jelly-fish. These

Fig. 9.— Aurelia: Life-cycle.

a, embryo ; b, Hydra tuba ; c, Hydra tuba, with medusoid segments ; d, medusa separated
to lead free existence.

produce ova, which are duly fertilized by sperms from a
different individual. A minute, free- swimming embryo
develops from the ovum, which settles down and becomes
a little polyp-like organism, the Hydra tuba. As growth
proceeds, this divides or segments into a number of se-
parable, but at first connected, parts. As these attain their
full development, first one and then another is detached
from the free end, floats off, and becomes a medusoid

46 Animal Life and Intelligence.

aurelia. Thus the fertilized ovum of aurelia develops, not
into one, but into a number of medusae,* passing through
the Hydra tuba condition as an intermediate stage.

Many of the hydroid zoophytes, forming colonies of
hydra-like organisms, give rise in the warm months to
medusoid jelly-fish, capable of producing ova and sperms.
Fertilization takes place; and the fertilized ova develop
into little hydras, which produce, by budding, new colonies.
In these new colonies, again, the parts which are to become
ovaries or testes float off, and ripen their products in free-
swimming, medusoid organisms. Such a rhythm between
development from ova and development by budding is
spoken of as an alternation of generations.

The fresh-water sponge (Spongilla} exhibits an analogous
rhythm. The ova are fertilized by sperms from a different
short-lived individual. They develop into sponges which
have no power of producing ova or sperms. But on the
approach of winter in Europe, and of the dry season in
India, a number of cells collect and group themselves into a
so-called gemmule. Round this is formed a sort of crust
beset with spicules, which, in some cases, have the form of
two toothed discs united by an axial shaft. When these
gemmules have thus been formed, the sponge dies ; but the
gemmules live on in a quiescent state during the winter or
the dry season, and with the advent of spring develop into
sponges, male or female. These have the power of pro-
ducing sperms or ova, but no power of producing gemmules.
The power of producing ova, and that of producing gem-
mules, thus alternates in rhythmic fashion.

But one more example of these modified forms of
reproduction can here be cited (from the author's text-book
on "Animal Biology"). The liver-fluke is a parasitic
organism, found in the liver of sheep. Here it reaches
sexual maturity, each individual producing many thousands
of eggs, which pass with the bile into the alimentary canal
of the host, and are distributed over the fields with the

* On the other hand, three ova of the crustacean Apris are said to coalesce
to form the single ovum from which one embryo develops.

Reproduction and Development.

47

excreta. Here, in damp places, pools, and ditches, free
and active embryos are hatched .out of the eggs. Each
embryo (Fig. 10, C., much enlarged) is covered with cilia,
except at the anterior end, which is provided with a head-

-p.s.

Fig. 10. — Liver-fluke : Embryonic stages. (After A. P. Thomas.)

A. Ovum: em., embryo; op., operculum. B. Limnaus truncatulus (natural size). C. Free
embryo: e.s., eye-spot; ex., excretory vessel; g.c., germinal cells; h.p., head-papilla. D.
Embryo preparing to become a sporocyst : g.c., germinal cells. K. Sporocyst : g., gastrtila ;
TO., morula; re.., redia. F. Redia: b.o., birth-opening; ce., cercaria; col., collar; di., digestive
sac; ph.., pharynx; p.pr., posterior processes; re., daughter redia. G. Cercaria: cys., cysto-
genous organ ; di., digestive sac ; o.s., oral sucker ; p.s., posterior sucker ; ph., pharynx.

papilla (h.p.}. When the embryo comes in contact with
any object, it, as a rule, pauses for a moment, and then

48 Animal Life and Intelligence.

darts off again. But if that object be the minute water-
snail, Limneeus truncatulus (Fig. 10, B., natural size), instead
of darting off, the embryo bores its way into the tissues
until it reaches the pulmonary chamber, or more rarely
the body-cavity. Here its activity ceases. It passes into
a quiescent state, and is now known as a sporocyst (Fig. 10,
E.). The active embryo has degenerated into a mere
brood-sac, in which the next generation is to be produced.
For within the sporocyst special cells undergo division, and
become converted into embryos of a new type, which are
known as redia (F.), and which, so soon as they are suffi-
ciently developed, break through the wall of the sporocyst.
They then increase rapidly in size, and browse on the
digestive gland of the water-snail (known as the intermediate
host), to which congenial spot they have in the mean time
migrated. The series of developmental changes is even
yet not complete. For within the redise (besides, at times,
daughter rediae) embryos of yet another type are produced
by a process of cell-division. These are known as cercariee
(Fig. 10, G.). Each has a long tail, by means of which
it can swim freely in water. It leaves the intermediate
host, and, after leading a short, active life, becomes encysted
on blades of grass. The cyst is formed by a special larval
organ, and is glistening snowy white. Within the cyst lies
the transparent embryonic liver-fluke, which has lost its
tail in the process of encystment.

The last chapter in this life-history is that in which the
sheep crops the blade of grass on which the parasite lies
encysted ; whereupon the cyst is dissolved in the stomach
of the host, the little liver-fluke becomes active, passes
through the bile-duct into the liver of the sheep, and there,
growing rapidly, reaches sexual maturity, and lays its
thousands of eggs, from each of which a -fresh cycle may
take its origin. The sequence of phenomena is charac-
terized by discontinuity of development. Instead of the
embryo growing up continuously into the adult, with only
the atrophy of provisional organs (e.g. the gills and tail of
the tadpole, or embryo frog), it produces germs from which

Reproduction and Development. 49

the adult is developed. Not merely provisional organs, but
provisional organisms, undergo atrophy. In the case of
the liver-fluke there are two such provisional organisms,
the embryo sporocyst and the redia.

We may summarize the life-cycle thus —

1. Ovum laid in liver of sheep, passes with bile into
intestine, and thence out with the excreta.

2. Free ciliated embryo, in water or on damp earth,
passes into pulmonary cavity of lAmneeus truncatulus, and
develops into

3. Sporocyst, in which secondary embryos are developed,
known as

4. Redice, which pass into the digestive glands of
Limnceus, and within which, besides daughter redise, there
are developed tertiary embryos, or

5. Cercaria, which pass out of the intermediate host
and become

6. Encysted on blades of grass, which are eaten by
sheep. The cyst dissolves, and the young flukes pass into
the liver of their host, each developing into

7. A liver-fluke, sexual, but hermaphrodite.

Here, again, we notice that one fertilized ovum gives
rise to not one, but a number of liver-flukes.

We must now pass on to consider the growth and
development of organisms. Simple growth results from the
multiplication of similar cells. As the child, for example,
grows, the framework of the body and the several organs
increase in size by continuous cell-multiplication. Develop-
ment is differential growth ; and this may be seen either in
the organs or parts of an organism or in the cells themselves.
As the child grows up into a man, there is a progressive
change in his relative proportions. The head becomes
relatively smaller, the hind limbs relatively longer, and
there are changes in the proportional size of other organs.

In the development of the embryo from the ovum, the
differentiation is of a deeper and more fundamental
character. Cells at first similar become progressively
dissimilar, and out of a primitively homogeneous mass of

E

50 Animal Life and Intelligence.

cells is developed a heterogeneous system of different but
mutually related tissues.

This view of development is, however, the outcome of
comparatively modern investigation and perfected micro-
scopical appliances. The older view was that development
in all cases is nothing more than differential growth, that
there is no differentiation of primitively similar into
ultimately different parts. Within the fertilized ovum of
the horse or bird lay, it was supposed, in all perfection of
structure, a miniature racer or chick, the parts all there,
but too minute to be visible. All that was required was
that each part should grow in due proportion. Those who
held this view, however, divided into two schools. The
one believed that the miniature organism was contained
within the ovum, the function of the sperm being merely
to stimulate its subsequent developmental growth. The
other held 'that the sperm was the miniature organism, the
ovum merely affording the food-material necessary for its
developmental growth. In either case, this unfolding of
the invisible organic bud was the evolution of the older
writers on organic life. More than this. As Messrs.
Geddes and Thomson remind us,* "the germ was more
than a marvellous bud-like miniature of the adult. It
necessarily included, in its turn, the next generation, and
this the next — in short, all future generations. Germ
within germ, in ever smaller miniature, after the fashion
of an infinite juggler's box, was the corollary logically
appended to this theory of preformation and unfolding."

Modern embryology has completely negatived any such
view as that of preformation, and as completely established
that the evolution is not the unfolding of a miniature germ,
but the growth and differentiation of primitively similar
cell-elements. In different animals, as might be expected,
the manner and course of development are different. We
may here illustrate it by a very generalized and so to
speak diagrammatic description of the development of a
primitive vertebrate.

* " The Evolution of Sex," p. 84.

Reproduction and Development.

The ovum before fertilization is a simple spherical cell,
without any large amount of nutritive material in the
form of food-yolk (A.}. It contains a nucleus. Previous
to fertilization, however, in many forms of life, portions of
the nucleus, amounting to three parts of its mass, are got
rid of in little " polar cells " budded off from the ovum.
The import of this process we shall have to consider in
connection with the subject of heredity. The sperm is also

Fig. 11. — Diagram of development.
See text. The fine line across G. indicates the plane of section shown in S.

a nucleated cell ; and on its entrance into the ovum there
are for a short time two nuclei — the female nucleus proper
to the ovum, and the male nucleus introduced by the sperm.
These two unite and fuse to form a joint nucleus. Thus the
fertilized ovum starts with a perfect blending of the nuclear
elements from two cells produced by different parents.

52 Animal Life and Intelligence.

Then sets in what is known as the segmentation or
cleavage of the ovum. First the nucleus and then the cell
itself divides into two equal halves (B.), each of these
shortly afterwards again dividing into two. We may call
the points of intersection of these two planes of division the
" poles," and the planes " vertical planes." We thus have
four cells produced by two vertical planes (C.). The next
plane of division is equatorial, midway between the poles.
By this plane the four cells are subdivided into eight (D.).
Then follow two more vertical planes intermediate between
the first two. By them the eight cells are divided into
sixteen. These are succeeded by two more horizontal
planes midway between the equator and the poles. Thus
we get thirty-two cells. So the process continues until, by
fresh vertical and horizontal planes of division, the ovum is
divided into a great number of cells.

But meanwhile a cavity has formed in the midst of the
ovum. This makes its appearance at about the eight-cell
stage, the eight cells not quite meeting in the centre of the
ovum. The central cavity so formed is thus surrounded
by a single layer of cells, and it remains as a single layer
throughout the process of segmentation, so that there
results a hollow vesicle composed of a membrane constituted
by a single layer of cells (E.).

The cells on one side of the vesicle are rather larger
than the others, and the next step in the process is the
apparent pushing in of this part of the hollow sphere ; just
as one might take a hollow squash indiarubber ball, and
push in one side so as to form a hollow, two-layered cup (F.).
The vesicle, then, is converted into a cup, the mouth of
which gradually closes in and becomes smaller, while the
cup itself elongates (G.).* Thus a hollow, two-layered,
stumpy, worm-like embryo is produced, the outer layer of

* In some forms of life the opening of the cup marks the position of the
future mouth ; in others, of the future vent. In yet others it elongates into
a slit, occupying the whole length of the embryo; the middle part of the slit
closes up, and the opening at the far ends mark the position, the one of the
future mouth, the other of the future vent.

Reproduction and Development. 53

which may be ciliated, so that by the lashing of these
cilia it is enabled to swim freely in the water. The inner
cavity is the primitive digestive cavity.

A cross- section through the middle of the embryo at
this stage will show this central cavity surrounded by a two-
layered body- wall (H.). A little later the following changes
take place (J. K.) : Along a definite line on the surface of
the embryo, marking the region of the back, the outer layer
becomes thickened ; the edges of the thickened band so
produced rise up on either side, so as to give rise to a
median groove between them ; and then, overarching and
closing over the groove, convert it into a tube. This tube
is called the neural tube, because it gives rise to the
central nervous system. In the region of the head it
expands ; and from its walls, by the growth and differentia-
tion of the cells, there is formed — in the region of the head,
the brain, and along the back, the spinal cord. Imme-
diately beneath it there is formed a rod of cells, derived
from the inner layer. This rod, which is called the noto-
chord, is the primitive axial support of the body. Around
it eventually is formed the vertebral column, the arches
of the vertebrae embracing and protecting the spinal cord.

Meanwhile there has appeared between the two primitive
body-layers a third or middle layer.* The cells of which
it is composed arise from the inner layer, or from the lips
of the primitive cup when the outer and inner layer pass
the one into the other. This middle layer at first forms
a more or less continuous sheet of cells between the inner
and the outer layers. But ere long it splits into two
sheets, of which one remains adherent to the inner layer
and one to the outer layer. The former becomes the
muscular part of the intestinal or digestive tube, the latter
the lining of the body-wall. The space between the two is
known as the body-cavity. Beneath the throat the heart
is fashioned out of this middle layer.

Very frequently — that is to say, in many animals — the

* In technical language, the outer layer of cells is called the epiblast, the
inner layer the hypoblast, and the mid-layer between them the mesoblast.

54 Animal Life and Intelligence.

opening by which the primitive digestive tube communi-
cated with the exterior has during these changes closed
up, so that the digestive cavity does not any longer
communicate in any way with the exterior. This is
remedied by the formation of a special depression or pit
at the front end for the mouth, and a similar pit at the
hinder end.* These pits then open into the canal, and
communications with the exterior are thus established.
The lungs and liver are formed as special outgrowths from
the digestive tube. The ovaries or testes make their
appearance at a very early period as ridges of the middle
layer projecting into the body-cavity. For some time it
is impossible to say whether they will produce sperms or
ova ; and it is said that in many cases they pass through
a stage in which one portion has the special sperm-pro-
ducing, and another the special ovum-producing, structure.
But eventually one or other prevails, and the organs
become either ovaries or testes.

Thus from the outer layer of the primitive embryo is
produced the outer skin, together with the hairs, scales,
or feathers which it carries ; from it also is produced the
nervous system, and the end-organs of the special senses.
From the inner layer is formed the digestive lining of the
alimentary tube and the glands connected therewith ; from
it also the primitive axial support of the body. But this
primitive support gives place to the vertebral column
formed round the notochord; and this is of mid-layer
origin. Out of the middle layer are fashioned the muscles
and framework of the body ; out of it, too, the heart and
reproductive organs. The tissues of many of the organs
are cunningly woven out of cells from all three layers.
The lens of the eye, for example, is a little piece of the
outer layer pinched off and rendered transparent. The'
retina of that organ is an outgrowth from the brain, which,

* In technical language, the opening by which the primitive digestive
cavity (or mesenterori) communicates with the exterior is called the blastopore.
When this closes, the new opening for the mouth is called the stomodceum;
that for the vent, the proctodceum.

Reproduction and Development. 55

as we have seen, was itself developed from the outer layer.
But round the retina and the lens there is woven from the
middle layer the tough capsule of the eye and the circular
curtain or iris. The lining cells of the digestive tube are
cells of the inner layer, but the muscular and elastic coats
are of middle-layer origin. The lining cells of the salivary
glands arise from the outer layer where it is pushed in to
form the mouth-pit ; but the supporting framework of the
glands is derived from the cells of the middle layer.

Enough has now been said to give some idea of the
manner in which the different tissues and organs of the
organism are elaborated by the gradual differentiation of
the initially homogeneous ovum. The cells into which the
fertilized egg segments are at first all alike; then comes the
divergence between those which are pushed in to line the
hollow of the cup, and those which form its outer layer.
Thereafter follows the differentiation of a special band of
outer cells to form the nervous system, and a special rod,
derived from the inner cells, to form the primitive axial
support. And when the middle layer has come into exist-
ence, its cells group themselves and differentiate along
special lines to form gristle or bone, blood or muscle.

The description above given is a very generalized and
diagrammatic description. There are various ways in
which complexity is introduced into the developmental
process. The store of nutritive material present in the
egg, for example, profoundly modifies the segmentation
so that where, as in the case of birds' eggs, there is a large
amount of food-yolk, not all the ovum, but only a little
patch on its surface, undergoes segmentation. In this little
patch the embryo is formed. Break open an egg upon
which a hen has been sitting for five or six days, and you
'will see the little embryo chick lying on the surface of the
yolk. The large mass of yolk to which it is attached is
simply a store of food-material from which the growing
ohick may draw its supplies.

For it is clear that the growing and developing embryo
must obtain, in some way and from some source, the food-

56 Animal Life and Intelligence.

stuff for its nutrition. And this is effected, among different
animals, in one of three ways. Either the embryo becomes
at a very early stage a little, active, voracious, free-
swimming larva, obtaining for itself in these early days of
life its own living ; as is the case, for example, with the
oyster or the star-fish. Or the egg from which it is de-
veloped contains a large store of food-yolk, on which it can
draw without stint ; as is the case with birds. Or else the
embryo becomes attached to the maternal organism in
such a way that it can draw on her for all the nutriment
which it may require; as is the case with the higher
mammals.

In both these latter cases the food-material is drawn
from the maternal organism, and is the result of parental
sacrifice; but in different ways. In the case of the^bird,
the protoplasm of the ovum has acquired the 'power of
storing up the by-products of its vital activity. The ovum
of such an animal seems at first sight a standing contra-
diction to the statement, made some pages back, that the
cell cannot grow to any great extent without undergoing
division or fission ; and this because volume tends to outrun
surface. For the £olk_of a bird's egg is a single cell, and
is often of large size. But when we come to examine care-
fully these exceptional cases of very large cells — for what
we call the yolk of an egg is, I repeat, composed of a single
cell — we find that the formative protoplasm is arranged as
a thin patch on one side of the yolk in the case of the
bird's egg, or as a thin pellicle surrounding the yolk in the
case of that of the lobster or the insect. All the rest is a
product of protoplasmic life stowed away beneath the patch
or within the pellicle. And this stored material is relatively
stable and inert, not undergoing those vital disruptive
changes which are characteristic of living formative proto-
plasm. The mass of formative protoplasm, even in the
large eggs of birds, is not very great, and is so arranged
as to offer a relatively extensive surface. All the rest, the
main mass of the visible egg-yolk, is the stored product of
a specialized activity of the formative protoplasm. But all

Reproduction and Development. 57

this material is of parental origin — is elaborated from the
nutriment absorbed and digested by the mother.

Thus we see, in the higher types of life, parental sacrifice,
fosterage, and protection. For in the case of mammals
and many birds, especially those which are born in a
callow, half-fledged condition, even when the connection of
mother and offspring is severed, or the supplies of food-yolk
are exhausted, and the young are born or hatched, there is
still a more or less prolonged period during which the
weakly offspring are nourished by milk, by a secretion from
the crop ("pigeon's milk"), or by food-stuff brought with
assiduous care by the parents. There is a longer or
shorter period of fosterage and protection — longer in the
case of man than in that of any of the lower animals — ere
the offspring are fitted to fend for themselves in life's
struggle.

And accompanying this parental sacrifice, first in
supplying food for embryonic' development, and then in
affording fosterage and protection during the early stages
of growth, there is, as might well be supposed, a reduction
in the number of ova produced and of young brought forth
or hatched. Many of the lower organisms lay hundreds of
thousands of eggs, each of which produces a living active
embryo. The condor has but two downy fledglings in a
year; the gannet lays annually but a single egg; while
the elephant, in the hundred years of its life, brings forth
but half a dozen young.

We shall have to consider by what means these opposite
tendencies (a 'tendency to produce enormous numbers of
tender, ill-equipped embryos, and a tendency to produce
few well-equipped offspring) have been emphasized. The
point now to be noted is that every organism, even the
slowest breeder that exists, produces more young than are
sufficient to keep up the numbers of the species. If every
pair of organisms gave birth to a similar pair, and if this
pair survived to do likewise, the number of individuals in
the species would have no tendency either to increase or
to diminish. But, as a matter of fact, animals actually do

58 Animal Life and Intelligence.

produce from three or four times to hundreds or even
thousands of times as many new individuals as are neces-
sary in this way to keep the numbers constant. This is
the law of increase. It may be thus stated : The number of
individuals in every race or species of animals is tending to
increase. Practically this is only a tendency. By war, by
struggle, by competition, by the preying of animals upon
each other, by the stress of external circumstances, the
numbers are thinned down, so that, though the births are
many, the deaths are many also, and the survivals few.
In the case of those species the numbers of which are
remaining constant, out of the total number born only two
survive to procreate their kind. We may judge, then, of
the amount of extermination that goes on among those
animals which produce embryos by the thousand or even
the hundred thousand. The effects of this enormous death-
rate on the progress of the race or species we shall have
to' consider in the next chapter, when the question of the
differentiation of species is before us.

There is one form of differentiation, however, which we
may glance at before closing this chapter — the differentia-
tion of sex. We are not in a position to discuss the ultimate
causes of sex-differentiation, but we may here note the
proximate causes as they seem to be indicated in certain
cases.

Among honey-bees there are males (drones), fertile
females (queens), and imperfect or infertile females (workers).
It has now been shown, beyond question, that the eggs
from which drones develop are not fertilized. The presence
or absence of fertilization in this case determines the sex.
During the nuptial flight, a special reservoir, possessed by
the queen bee, is stored with sperms in sufficient number
to last her egg-laying life. It is in her power either to
fertilize the eggs as they are laid or to withhold fertiliza-
tion. If the nuptial flight is prevented, and the reservoir
is never stored with sperms, she is incapable of laying
anything but drone eggs. The cells in which drones are
developed are somewhat smaller than those for ordinary

Reproduction and Development. 59

workers ; but what may be the nature of the stimulus that
prompts the queen to withhold fertilization we at present do
not know. The difference between the fertile queen and
the unfertile worker seems to be entirely a matter of
nutrition. If all the queen-embryos should die, the
workers will tear down the partitions so as to throw three
ordinary worker-cells into one ; they will destroy two of the
embryos, and will feed the third on highly nutritious and
stimulating diet ; with the result that the ovaries and
accessory parts are fully developed, and the grub that
would have become an infertile worker becomes a fertile
queen. And one of the most interesting points about this
change, thus wrought by a stimulating diet, is that not
only are the reproductive powers thus stimulated, but the
whole organism is modified. Size, general structure, sense-
organs, habits, instincts, and character are all changed
with the development of the power of laying eggs. The
organism is a connected whole, and you cannot modify one
part without deeply influencing all parts. This is the law
of correlated variation.

Herr Yung has made some interesting experiments on
tadpoles. Under normal circumstances, the relation of
females to males is about 57 to 43. But when the tadpoles
were well fed on beef, the proportion of females to males
rose so as to become 78 to 32 ; and on the highly nutritious
flesh of frogs the proportion became 92 to 8. A highly
nutritious diet and plenty of it caused a very large pre-
ponderance of females.

Mrs. Treat, in America, found that if caterpillars were
half-starved before entering upon the chrysalis state, the
proportion of males was much increased; while, if they
were supplied with abundant nutritious food, the proportion
of female insects was thereby largely increased. The same
law is said to hold good for mammals. Favourable vital
conditions are associated with the birth of females; un-
favourable, with that of males. Herr Ploss attempts to
show that, among human folk, in hard times there are more
boys born; in good times, more girls.

60 Animal Life and Intelligence.

On the whole, we may say that there is some evidence
to show that in certain cases favourable conditions of
temperature, and especially nutrition, tend to increase the
number of females. We have seen that many animals
pass through a stage where the reproductive organs are not
yet differentiated into male and female, while in some there
is a temporary stage where the outer parts of the organ
produce ova and the inner parts sperms. We have also
seen that the ova are cells where storage is in excess ; the
sperms are cells in which fission is in excess. Favourable
nutritive conditions may, therefore, not incomprehensibly
lead to the formation of well-stored ova ; unfavourable
nutritive conditions, on the other hand, to the formation of
highly subdivided sperms. By correlated variation,* the
ova-bearing or sperm-bearing individuals then develop into
the often widely different males and females.

* We have seen that when volume tends to outrun surface, fission may
take place, whereby the same volume has increased surface. But in un-
favourable nutritive conditions, the same surface which had before been
sufficient for nutrition may become, under the less favourable circumstances,
insufficient, and fission may again take place to give a larger absorbent sur-
face. Hence, possibly, the connection between insufficient nutriment and
highly subdivided sperms.

( 6i )

CHAPTER IV.

VAKIATION AND NATURAL SELECTION.

EVERYTHING, so far as in it lies, said Benedict Spinoza, tends
to persist in its own being. This is the law of persistence.
It forms the basis of Newton's First Law of Motion, which
enunciates that, if a body be at rest, it will remain so unless
acted on by some external force ; or, if it be in motion, it
will continue to move in the same straight line and at a
uniform velocity unless it is acted on by some external
force. Practically every known body is thus affected by
external forces ; but the law of persistence is not thereby
disproved. It only states what would happen under certain
exceptional or perhaps impossible circumstances. To
those ignorant of scientific procedure, it seems unsatis-
factory, if not ridiculous, to formulate laws of things, not as
they are, but as they might be. Many well-meaning but
not very well-informed people thus wholly misunderstand
and mistake the value of certain laws of political economy,
because in those laws (which are generalized statements of
fact under narrowed and rigid conditions, and do not pre-
tend to be inculcated as rules of conduct) benevolence,
sentiment, even moral and religious duty, are intention-
ally excluded. These laws state that men, under motives
arising out of the pursuit of wealth, will act in such and
such a way, unless benevolence, sentiment, duty, or some
other motive, lead them to act otherwise. Such laws,
which hold good, not for phenomena in their entirety, but
for certain isolated groups of facts under narrowed con-
ditions, are called laws of the factors of phenomena. And
'since the complexity of phenomena is such that it is

62 Animal Life and Intelligence.

difficult for the human mind to grasp all the interlacing
threads of causation at a single glance, men of science
have endeavoured to isolate their several strands, and,
applying the principle of analysis, without which reasoning
is impossible, to separate out the factors and determine
their laws. In this chapter we have to consider some of
the factors of organic progress, and endeavour to determine
their laws.

The law of heredity may be regarded as that of persistence
exemplified in a series of organic generations. When, as
in the amceba and some other protozoa, reproduction is by
simple fission, two quite similar organisms being thus pro-
duced, there would seem to be no reason why (modifications
by surrounding circumstances being disregarded) hereditary
persistence should not continue indefinitely. Where, how-
ever, reproduction is effected by the detachment of a single
cell from a many- celled organism, hereditary persistence *
will be complete only on the condition that this reproductive
cell is in some way in direct continuity with the cells of
the parent organism or the cell from which that parent
organism itself developed. And where, in the higher
animals, two cells from two somewhat different parents
coalesce to give origin to a new individual, the phenomena
of hereditary persistence are still further complicated by
the blending of characters handed on in the ovum and the
sperm ; still further complication being, perhaps, produced
by the emergence in the offspring of characters latent in
the parent, but derived from an earlier ancestor. And if
characters acquired by the parents in the course of their
individual life be handed on to the offspring, yet further
complication will be thus introduced.

It is no matter for surprise, therefore, that, notwith-

* Samuel Butler iu England, and Ewald Hering in Prague, have in-
geniously likened this hereditary persistence to " organic memory." What
are ordinarily called memory, habit, instinct, and embryonic reconstruction,
are all referable to the memory of organic matter. The analogy, if used with
due caution, is a helpful one, what we call memory being the psychical aspect
(under certain special organic and neural conditions) of what under the
physical aspect we call persistence.

Variation and Natural Selection. 63

standing the law of hereditary persistence, variations
should occur in the offspring of animals. At the same
time, it must be remembered that the occurrence of varia-
tions is not and cannot be the result of mere chance ; but
that all such variations are determined by some internal or
external influences, and are thus legitimate and important
subjects of biological investigation. In the next chapter
we shall consider at some length the phenomena of heredity
and the origin of variations. Here we will accept them
without further discussion, and consider some of their con-
sequences. But even here, without discussing their origin,
we must establish the fact that variations do actually occur.

Variations may be of many kinds and in different
directions. In colour, in size, in the relative develop-
ment of different parts, in complexity, in habits, and in
mental endowments, organisms or their organs may vary.
Observers of mammals, of birds, and of insects are well
aware that colour is a variable characteristic. But these
colour-variations are not readily described and tabulated.
In the matter of size the case is different. In Mr. Wallace's
recent work on " Darwinism " a number of observations
on size-variations are collected and tabulated. As this is
a point of great importance, I propose to illustrate it some-
what fully from some observations I have recently made of
the wing-bones of bats. In carrying out these observa-
tions and making the necessary measurements, I have had
the advantage of the kind co-operation of my friend Mr.
Henry Charbonnier, of Clifton, an able and enthusiastic
naturalist.*

The nature of the bat's wing will be understood by
the aid of the accompanying figure (Fig. 12). In the fore
limb the arm-bone, or humerus, is followed by an elongated
bone composed of the radius and ulna. At the outer end
of the radius is a small, freely projecting digit, which
carries a claw. This answers to the thumb. Then follow
four long, slender bones, which answer to the bones in the

* I have also to thank Mr, Edward Wilson for kindly giving me the
measurements of three or four bats in the Bristol Museum.

64 Animal Life and Intelligence.

palm of our hand. They are the metacarpals, and are
numbered n., in., iv., and v. in the tabulated figures in which
the observations are recorded. The metacarpals of the
second and third digits run tolerably close together, and
form the firm support of the anterior margin of the wing.

Fig. 12.— "Wing" of bat (Pipistrette).

Hu., hnmerus, or ann-bone; Ul., conjoined radius and ulna, a bone in the forearm ; Po.,
pollex, answering to our thumb ; n., in., iv., v., second, third, fourth, and fifth digits of the
manus, or hand. The figures are placed near the metacarpals, or palm-bones. These are
followed by the phalanges. Ft., femur or thigh-bone; Ti., tibia, the chief bone of the shank.
The digits of the pes, or foot, are short and bear claws. C'a., calcar.

Those of the third and fourth make a considerable angle
with these and with each other, and form the stays of the
mid part of the wing. Beyond the metacarpals are the
smaller joints or phalanges of the digits, two or three to
each digit. The third digit forms the anterior point or
apex of the wing. The fourth and fifth digits form
secondary points behind this. Between these points the
wing is scalloped into bays.

From the point of the fifth or last digit the leathery
wing membrane sweeps back to the ankle. The bones of
the hind limb are the femur, or thigh-bone, and the tibia
(with a slender, imperfectly developed fibula). There are
five toes, which bear long claws. From the ankle there
runs backward a long, bony and gristly spur, which serves

Variation and Natural Selection.

to support the membrane which stretches from the ankle
to the tip (or near the tip) of the tail.

Thus the wing of the bat consists of a membrane
stretched on the expanded or spread fingers of the hand, and
sweeping from the point of the little finger to the ankle.
Behind the ankle there is a membrane reaching to the tip
of the tail. This forms a sort of net in which some bats, at
any rate, as I have myself observed, can catch insects.

I have selected the wing of the bat to exemplify varia.
tion, (1) because the bones are readily measured even in
dried specimens ; (2) because they form the mutually related
parts of a single organ ; and (3) because they offer facilities
for the comparison of variations, not only among the
individuals of a single species, but also among several
distinct species.

The method employed has been as follows : The several
bones have been carefully measured in millimetres,* and
all the bones tabulated for each species. Such tables of
figures are here given in a condensed form for three species
of bats.

BAT-MEASUREMENTS (IN MILLIMETRES).

~ t

THIRD

FOURTH

FIFTH

fi|

DIGIT.

DIGIT.

DIGIT.

1

1

|

«

ges 2, 3.

rf

»

I

c

i

i

c.

i

s«

jj

•

|

s

=

1

i

S

1

5

03

r

1

1

a

I

I

|

1

1

|

1

I

s
S

41

6*5

88

40

16

1!)

38

14

7

33

8

7

16

41

6

38

40

16

19

39

16-8

7

33

8

6-5

16

Hairy-armed bat ( Vespe-
rugo leisleri).

41
41-5
40

6
5

6

39
39
39

40
37

16
17

15-5

18
30
18

39
39

37

16
16

1-1-5

6*5
7

7

33
33
32

8
8

7
7 •

6-e

16
15
15

41

5-5

38-6

39

UJT,

20

39

15

7-5

33

g

7-5

17

41

6

39

40

IB'B

20*5

N

15-f,

7

83

8

7

16

51

6

39 .

M

19

39

40

11

18

40

13

15

22

Horseshoe bat (Ehinolo-
phus ferri-equinum').

54
52
54

*
5
5

40
39

36
36
34

18
18
18

3-2
32

40
39
40

11

10
11

19

19

17

4(1
40
40

14
13
13

16
14
13

28
23
25

46

5

M

34

16

39

36

10

19

30

13

17

22

Lesser horseshoe bat (

34

4

25

33

12

17

26

6-6

12

36

B

13

17

(Rhinoloplius hipyo- \
sideros). (

37
35

3
3

26

26

34

34-0

13
13

30
17

28
37

8
7

13
12

28
36

9

10

14
13

17
15

It would be troublesome to the reader to pick out the
* A millimetre is about ^V of au inch, or more exactly -03937 inch.

66 Animal Life and Intelligence.

meaning from these figures. I have, therefore, plotted in
the measurements for four other species of bats in tabular
form (Figs. 13, 14, 15, 16).

Fig. 13, for example, deals with the common large
noctule bat, which may often be seen flying high up on
summer evenings. Now, the mean length of the radius and
ulna in eleven individuals was 51*5 millimetres. Suppose
all the eleven bats had this bone (for the two bones form
practically one piece) of exactly the same length. There
would then be no variation. We may express this supposed
uniformity by the straight horizontal line running across
the part of the figure dealing with the radius and ulna.
Practically the eleven bats measured did not have this
bone of the same length ; in some of them it was longer,
in others it was shorter than the mean. Let us run
through the eleven bats (which are represented by the
numbers at the head of the table) with regard to this bone.
The first fell below the average by a millimetre and a half,
the length being fifty millimetres. This is expressed in the
table by placing a dot or point three quarters of a division
below the mean line. Each division on the table represents
two millimetres, or, in other words, the distance between
any two horizontal lines stands for two millimetres
measured. Half a division, therefore, is equivalent to one
measured millimetre ; a quarter of a division to half a milli-
metre. The measurements are all made to the nearest half-
millimetre. The second bat fell short of the mean by one
millimetre. The bone measured 50' 5 millimetres. The
third exceeded the mean by a millimetre and a half ; the
fourth, by three millimetres and a half. The fifth was a
millimetre and a half above the mean ; and the sixth
and seventh were both half a millimetre over the mean.
The eighth fell short by half a millimetre ; the ninth and
tenth by a millimetre and a half; and the eleventh by
two millimetres and a half. The points have been con-
nected together by lines, so as to give a curve of variation
for this bone.

The other curves in these four tables are drawn in exactly

Variation and Natural Selection.

67

Gf 9

72345

III

nges of Dlg±

ibia
mm

Fig. 13.— The noctule (Vesperugo noctula).

68

Animal Life and Intelligence.

Phalanges of Digit
81-5 mm

IV

Phalanges of Digit
18-5 mm ~

V

Metacarpal
31 mm

V

Phalanges of Digit
18-5 mm

Tibia
17- 5 mm

Fig. 14.— The long-eared bat (Plecotus auritus).

Variation and Natural Selection.

69

/ 23456789 70

Fig. 15. — The pipistrelle (Vesperugo pipsitrellus).

Animal Life and Intelligence.

123 4 S 6 7

II

Metacarpal
28mm

III

Phalanges of Digit

24. 5 mm

IV

Metacarpal
28.5mm

IV

Phalanges of Dig
16.5 mm

V

Metacarpal
28.5mm

V

Phalanges of Dig
14.5 mm

Tibia
14.5mm

10 11 12 13 14 15 18 17 18 19 20

Fig. 16.— The whiskered bat (Vespertilio mystacinus).

Variation and Natiiral Selection. 71

the same way. The mean length is stated; and the
amount by which a bone in any bat exceeds or falls short
of the mean can be seen and readily estimated by means
of the horizontal lines of the table. Any one can reconvert
the tables into figures representing our actual measurements.

Now, it may be said that, since some bats run larger
than others, such variation is only to be expected. That is
true. But if the bones of the wing all varied equally, all the
curves would be similar. That is clearly not the case. The
second metacarpal is the same length in 5 and 6. But the
third metacarpal is two millimetres shorter in 6 than in 5.
In 10 the radius and ulna are longer than in 11 ; but the
second metacarpal is shorter in 10 than in 11. A simple
inspection of the table as a whole will show that there is a
good deal of independent variation among the bones.

The amount of variation is itself variable, and in some
cases is not inconsiderable. In the long-eared bats 4 and
5 in Fig. 14, the phalanges of the third digit measured 26'5
millimetres in 4, and 34 millimetres in 5 — a difference of
more than 28 per cent. This is unusually large, and it is
possible that there may have been some slight error in the
measurements.* A difference of 10 or 12 per cent, is,
however, not uncommon.

In any case, the observations here tabulated show (1)
that variations of not inconsiderable amount occur among
the related bones of the bat's wing ; and (2) that these varia-
tions are to a considerable extent independent of each other.

So far we have compared a series of individuals of the
same species of bat, each table in Figs. 13-16 dealing
with a distinct species. Let us now compare the different
species with each other. To effect such a comparison, we
must take some one bone as our standard, and we must
level up our bats for the purposes of tabulation. I have
selected the radius and ulna as the standard. In both the

* In nearly all cases the measurements were checked by comparing the
two wings. In one or two instances there were differences of as much as two
or three millimetres between the bones of the two sides of the body, but in
most cases they exactly corresponded.

72 Animal Life and Intelligence.

noctule and the greater horseshoe bats the mean length of
this bone is 51 '5 millimetres. The bones of each of the
other bats have been multiplied by such a number as will
bring them up to the level of size in these two species.
Mr. Galton, in his investigations on the variations of
human stature, had to take into consideration the fact that
men are normally taller than women. He found, however,
that the relation of man to woman, so far as height is
concerned, is represented by the proportion 108 to 100. By
multiplying female measurements by 1*08, they were brought
up to the male standard, and could be used for purposes of
comparison. In the same way, by multiplying in each case
by the appropriate number, I have brought all the species
in the table (Fig. 17) up to the standard of the noctule.
When so multiplied, the radius and ulna (selected as the
standard of comparison) has the same length in all the
species, and is hence represented by the horizontal line in
the table.

Compared with this as a standard, the mean length of
the second metacarpal in the seven species is forty-three
millimetres ; that of the third metacarpal, forty-four milli-
metres ; and so on. The amount by which each species
exceeds or falls short of the mean is shown on the table,
and the points are joined up as before. Here, again, the
table gives the actual measurements in each case. For
example, if the mean length of the third metacarpal of the
greater horseshoe bat be required, it is seen by the table
to fall short of the mean by four horizontal divisions and
a quarter, that is to say, by eight millimetres and a half.
The length is therefore (44 — 8^) 35'5 millimetres.

Now, it will be seen from the table that the variation in
the mean length of the bones in different species is much
greater than the individual variations in the members of
the same species. The table also brings out in an interest-
ing way the variation in the general character of the wing.
The noctule, for example, is especially strong in the de-
velopment of the second and third metacarpals, the
phalanges of the third digit being also a little above the

Variation and Natural Selection.

73

Noctule Gr.Horse Shoe Hairy Armed Long Eared Lr.Horse Shoe Whiskered Piplstrelle

Radius and

Ulna
51.5 mm

Metacarpal
43 mm

Metacarpal
44 mm

Phalanges of Diffi
43.5 mm

IV

Metacarpal
45 mm

IV

Phalanges of Digit
27.5 mm

Metacarpal
42 mm

'"'"

V

\ges of Digit
24

Tibia
21.5

Fig. 17.— Variations adjusted to the standard of the noctule.

74 Animal Life and Intelligence.

average. Eeference to the figure of the bat's wing on
p. 64 will show that these excellences give length to the
wing. It fails, however, in the metacarpal and phalanges
of the fifth digit, and in the length of the hind leg as
represented by the tibia. On consulting the figure of the
wing, it is seen that these are the bones which give breadth
to the wing. Here the noctule fails. Its wing is, therefore,
long and narrow. It is a swallow among bats.

On the other hand, the horseshoe bats fail conspicu-
ously in the second and third metacarpals, though they
make up somewhat in the corresponding digits. On the
whole, the wing is deficient in length. But the phalanges
of the fourth and fifth digits, and the length of the hind
limb represented by the tibia, give a corresponding increase
of breadth. The wing is, therefore, relatively short and
broad. The long-eared bat, again, has the third meta-
carpal and its digits somewhat above the mean, and there-
fore a somewhat more than average length. But it has
the fifth metacarpal with its digit and also the tibia
decidedly above the mean, and therefore more than average
breadth. Without possessing the great length of the
noctule's wing, or the great breadth of that of the horse-
shoe, it still has a more than average length and breadth.

The total wing-areas are very variable, the females
having generally an advantage over the males. I do not
feel that our measurements are sufiiciently accurate to
justify tabulation. Taking, however, the radius and ulna
as the standard for bringing the various species up to the
same level, the greater horseshoe seems to have decidedly
the largest wing-area ; the noctule stands next ; then come
the lesser horseshoe and the long-eared bat; somewhat
lower stands the hairy-armed bat ; while the pipistrelle
and the whiskered bat (both small species) stand lowest.*

Sufficient has now been said in illustration of the fact

* We are anxious to extend our observations and to compare series of bats
from different localities. If any of my readers should feel disposed to help us,
by sending specimens (with the locality duly indicated) to Mr. H. Charbonnier,
7, The Triangle South, Clifton, Bristol, we shall be grateful.

Variation and Natiiral Selection. 75

that variations in the lengths of the bones in the bat's
wing do actually occur in the various individuals of one
species ; that the variations are independent ; and that the
different species and genera have the character of the wing
determined by emphasizing, so to speak, variations in
special directions. I make no apology for having treated
the matter at some length. Those who do not care for
details will judiciously exercise their right of skipping.

As before mentioned, Mr. Wallace has collected and
tabulated other observations on size and length variations.
And in addition to such variations, there are the numerous
colour-variations that do not admit of being so readily
tabulated. Mr. Cockerell tells us that among snail-shells,
taking variations of banding alone, he knows of 252
varieties of Helix nemoralis and 128 of H. hortensis.*

That variations do occur under nature is thus un-
questionable. And it is clear that all variations necessarily
fall under one of three categories. Either they are of
advantage to the organism in which they occur ; or they are
disadvantageous ; or they are neutral, neither advantageous
nor disadvantageous to the animal in its course through life.

We must next revert to the fact to which attention was
drawn in the last chapter, that every species is tending,
through natural generation, to increase in numbers. Even
in the case of the slow-breeding elephant, the numbers tend
to increase threefold in each generation ; for a single pair
of elephants give birth to three pairs of young. In many
animals the tendency is to increase ten, twenty, or thirty-
fold in every generation ; while among fishes, amphibians,
and great numbers of the lower organisms, the tendency is
to multiply by a hundredfold, a thousandfold, or even in
some cases ten thousandfold. But, as before noticed, this
is only a tendency. The law of increase is a law of one
factor in life's phenomena, the reproductive factor. In any

* Nature, vol. xli. p. 393. The variation in molluscs is often considerable.
In one of the bays in the basement hall of the Natural History Museum is
a series showing the variation in size, form, and sculpturing of Paludomus
loricatus, which is found in the streams of Ceylon. These varieties have in
former times been named as ten distinct species !

76 Animal Life and Intelligence.

area, the conditions of which are not undergoing change,
the numbers of the species which constitute its fauna
remain tolerably constant. They are not actually increasing
in geometrical progression. There is literally no room for
such increase. The large birth-rate of the constituent
species is accompanied by a proportionate death-rate, or
else the tendency is kept in check by the prevention of
certain individuals from mating and bearing young.*

Now, the high death-rate is, to a large extent among
the lower organisms and in a less degree among higher
animals, the result of indiscriminate destruction. When
the ant-bear swallows a tongue-load of ants, when the
Greenland whale engulfs some hundreds of thousands of
fry at a gulp, when the bear or the badger destroys whole
nests of bees, — in such cases there is wholesale and indis-
criminate destruction. Those which are thus destroyed are
nowise either better or worse than those which escape. At
the edge of a coral reef minute, active, free-swimming coral
embryos are set free in immense numbers. Presently they
settle down for life. Some settle on a muddy bottom,
others in too great a depth of water. These are destroyed.
The few which take up a favourable position survive. But
they are no better than their less fortunate neighbours.
The destruction is indiscriminate. So, too, among fishes

* More observations and fuller knowledge on this latter point and on the
relative numbers of the sexes in different species are much to be desired. It
is clear that the number of offspring mainly depends upon the number of
females. But if it be true that good times and favourable conditions lead
to an increased production of females, while hard times and unfavourable
conditions lead to a relative increase of males, then it is evident that good
times will lead to a more rapid increase and hard times to a less rapid increase
of the species. Suppose, for example, in a particular district food and other
conditions were especially favourable for frogs. Among the well-nourished
tadpoles there would be a preponderance of females. In the next generation
the many females would produce abundant offspring (for one male may
fertilize the ova laid by several females). There would be a greater number
of tadpoles to compete for the same amount of nutriment. They would be
less nourished. There would be less females ; and in the succeeding genera-
tion a diminished number of tadpoles. Thus to some extent a balance between
the number of tadpoles and the amount of available nutrition would be main-
tained. These conclusions are, perhaps, too theoretical to be of much value,
while the tendency here indicated would be but one factor among many.

Variation and Natural Selection. 77

and the many marine forms which produce a great number
of fertilized*eggs giving rise to embryos that are from an
early period free-swimming and self-supporting. Such
embryos are decimated by a destruction which is quite
indiscriminate. And again, to take but one more example,
the liver-fluke, whose life-history was sketched in the last
chapter, produces its tens or hundreds of thousands of
ova. But the chances are enormously against their com-
pleting their life-cycle. If the conditions of temperature
and moisture are not favourable, the embryo is not hatched
or soon dies ; even if it emerges, no further development
takes place unless it chances to come in contact with a
particular and not very common kind of water-snail. When
it emerges from the intermediate host and settles on a
blade of grass, it must still await the chance of that blade
being eaten by a sheep or goat. It is said that the chances
are eight millions to one against it, and for the most part
its preservation is due to no special excellence of its own.
The destruction is to a large extent, though not entirely,
indiscriminate.

Even making all due allowance, however, for this indis-
criminate destruction — which is to a large extent avoided
by those higher creatures which foster their young — there
remain more individuals than suffice to keep up the normal
numbers of the species. Among these there arises a
struggle for existence, and hence what Darwin named
natural selection.

" How will the struggle for existence " — I quote, with
some omissions, the words of Darwin — " act in regard to
variation ? Can the principle of selection, which is so
potent in the hands of man, apply under nature ? I think
that we shall see that it can act most efficiently. Let the
endless number of slight variations and individual differ-
ences be borne in mind; as well as the strength of the
hereditary tendency. Let it also be borne in mind how
infinitely complex and close-fitting are the mutual relations
of all organic beings to each other and to their physical
conditions of life ; and consequently what infinitely varied

78 Animal Life and Intelligence.

diversities of structure might be of use to each being under
changing conditions of life. Can it, then, 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 successive generations ?
If such do occur, can we doubt (remembering that many
more individuals are born than can possibly survive) that
individuals having any advantage, however slight, over
others, 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 rigidly destroyed. This preservation of favourable indi-
vidual differences and variations, and the destruction of
those which are injurious, I have called Natural Selection,
or the Survival of the Fittest. Variations neither useful
nor injurious would not be affected by natural selection,
and would be left either a fluctuating element, or would
ultimately become fixed, owing to the nature of the
organism and the nature of the conditions." *

" The principle of selection," says Darwin, elsewhere,
" may conveniently be divided into three kinds. Methodical
selection is that which guides a man who systematically
endeavours to modify a breed according to some pre-
determined standard. Unconscious selection is that which
follows from men naturally preserving the most valued
and destroying the less valued individuals, without any
thought of altering the breed. Lastly, we have Natural
selection, which implies that the individuals which are best
fitted for the complex and in the course of ages changing
conditions to which they are exposed, generally survive
and procreate their kind." f

I venture to think that there is a more logical division
than this. A man who is dealing with animals or plants
under domestication may proceed by one of two well-con-
trasted methods. He may either select the most satisfac-

* " Origin of Species," pp. 62, 63.

t " Animals and Plants under Domestication," vol. it p. 177.

Variation and Natural Selection. 79

tory individuals or he may reject the most unsatisfactory.
We may term the former process selection, the latter
elimination. Suppose that a gardener is dealing with a
bed of geraniums. He may either pick out first the best,
then the second best, then the third, and so on, until he
has selected as many as he wishes to preserve. Or, on
the other hand, he may weed out first the worst, then in
succession other unsatisfactory stocks, until, by eliminating
the failures, he has a residue of sufficiently satisfactory
flowers. Now, I think it is clear that, even if the ultimate
result is the same (if, that is to say, he selects the twenty
best, or eliminates all but the twenty best), the method of
procedure is in the two cases different. Selection is applied
at one end of the scale, elimination at the other. There is
a difference in method in picking out the wheat-grains (like
a sparrow) and scattering the chaff by the wind.

Under nature both methods are operative, but in very
different degrees. Although the insect may select the
brightest flowers, or the hen-bird the gaudiest or most
tuneful mate, the survival of the fittest under nature is in
the main the net result of the slow and gradual process of
the elimination of the unfit.* The best-adapted are not,
save in exceptional cases, selected ; but the ill-adapted are
weeded out and eliminated. And this distinction seems to
me of sufficient importance to justify my suggestion that
natural selection be subdivided under two heads — natural
elimination, of widespread occurrence throughout the
animal world ; and selection proper, involving the element
of individual or special choice.

The term " natural elimination " for the major factor
serves definitely to connect the natural process with that
struggle for existence out of which it arises. The struggle
for existence is indeed the reaction of the organic world
called forth by the action of natural elimination. Organisms
are tending to increase in geometrical ratio. There is not

* I may here draw attention to the fact that the bats whose wing-bone
measurements were given above are those which have so far survived and
escaped such elimination as is now in progress.

80 Animal Life and Intelligence.

room or subsistence for the many born. The tendency is
therefore held in check by elimination, involving the struggle
for existence. And the factors of elimination are three :
first, elimination through the action of surrounding physical
or climatic conditions, under which head we may take such
forms of disease as are not due to living agency ; secondly,
elimination by enemies, including parasites and zymotic
diseases ; and thirdly, elimination by competition. It will
be convenient to give some illustrative examples of each of
these.

Elimination through the action of surrounding physical
conditions, taken generally, deals with the very groundwork
or basis of animal life. There are certain elementary
mechanical conditions which must be fulfilled by every
organism however situated. Any animal which fails to
fulfil these conditions will be speedily eliminated. There
are also local conditions which must be adequately met.
Certain tropical animals, if transferred to temperate or
sub-Arctic regions, are unable to meet the requirements of
the new climatic conditions, and rapidly or gradually die.
Fishes which live under the great pressure of the deep sea
are killed by the expansion of the gases in their tissues
when they are brought to the surface. Many fresh-water
animals are killed if the lake in which they live be invaded
by the waters of the sea. If the water in which corals live
be too muddy, too cold, or too fresh — near the mouth of a
great river on the Australian coast, for example — they will
die off. During the changes of climate which preceded
and followed the oncoming of the glacial epoch, there must
have been much elimination of this order. Even under
less abnormal conditions, the principle is operative. Darwin
tells us that in the winter of 1854-5 four-fifths of the
birds in his grounds perished from the severity of the
weather, and we cannot but suppose that those who were
thus eliminated were less able than others to cope with or
stand the effects of the inclement climatic conditions. My
colleague, Mr. G. Munro Smith, informs me that, in culti-
vating microbes, certain forms, such as Bacillus violaceus

Variation and Natural Selection. 81

and Micrococcus prodigiosus, remain in the field during
cold weather when other less hardy microbes have perished.
The insects of Madeira may fairly be regarded as affording
another instance. The ground-loving forms allied to
insects of normally slow and heavy flight have in Madeira
become wingless or lost all power of flight. Those which
attempted to fly have been swept out to sea by the winds,
and have thus perished ; those which varied in the direction
of diminished powers of flight have survived this eliminating
process. On the other hand, among flower-frequenting
forms and those whose habits of life necessitate flight, the
Madeira insects have stronger wings than their mainland
allies. Here, since flight could not be abandoned without
a complete change of life-habit, since all must fly, those
with weaker powers on the wing have been eliminated,
leaving those with stronger flight to survive and procreate
their kind.* In Kerguelen Island Mr. Eaton has found
that all the insects are incapable of flight, and most of them
in a more or less wingless condition.! Mr. Wallace regards
the reduction in the size of the wing in the Isle of Man
variety of the small tortoiseshell butterfly as due to the
gradual elimination of larger-winged individuals.^: These
are cases of elimination through the direct action of sur-
rounding physical conditions. Even among civilized
human folk, this form of elimination is still occasionally
operative — in military campaigns, for example (where the
mortality from hardships is often as great as the mortality
from shot or steel), in Arctic expeditions, and in arduous
travels. But in early times and among savages it must be
a more important factor.

Elimination by enemies needs somewhat fuller exempli'
fication. Battle within battle must, throughout nature,
as Darwin says, be continually recurring with varying
success. The stronger devour the weaker, and wage war
with each other over the prey. In the battle among co-
ordinates the weaker are eliminated, the stronger prevail.

* " Origin of Species," p. 109. f " Darwinism," p. 106.

J Ibid. p. 106.

82 Animal Life and Intelligence.

When the weaker are preyed upon by the stronger and a
fair fight is out of the question, the slow and heavy succumb,
the agile and swift escape ; stupidity means elimination,
cunning, survival ; to be conspicuous, unless it be for some
nasty or deleterious quality, is inevitably to court death :
the sober-hued stand at an advantage. In these cases, if
there be true selection at work, it is the selection of certain
individuals, the plumpest and most toothsome to wit, for
destruction, not for survival.

This mode of elimination has been a factor in the
development of protective resemblance and so-called
mimicry, and we may conveniently illustrate it by reference
to these qualities. If the hue of a creature varies in the
direction of resemblance to the normal surroundings, it will
render the animal less conspicuous, and therefore less liable
to be eliminated by enemies. This is well seen in the
larvae or caterpillars of many of our butterflies and moths.
It is not easy to distinguish the caterpillar of the clouded
yellow, so closely does its colour assimilate to the clover
leaves on which it feeds, nor that of the Lulworth skipper
on blades of grass. I would beg every visitor to the
Natural History Museum at South Kensington to look
through the drawers containing our British butterflies and
moths and their larvae, in the further room on the base-
ment, behind the inspiring statue of Charles Darwin. Half
an hour's inspection will serve to bring home the fact of
protective resemblance better than many words.

It may,1 however, be remarked that not all the cater-
pillars exhibit protective resemblance ; and it may be
asked — How have some of these conspicuous larvae, that of
the magpie moth, for example, escaped elimination ? What
is sauce for the Lulworth goose should be sauce for the
magpie gander. How is it that these gaudy and variable
caterpillars, cream-coloured with orange and black mark-
ings, have escaped speedy destruction ? Because they are
so nasty. No bird, or lizard, or frog, or spider would touch
them. They oan therefore afford to be bright-coloured.
Nay, their very gaudiness is an advantage, and saves them

Variation and Natural Selection. 83

from being the subject of unpleasant experiments in the
matter. Other caterpillars, like the palmer-worms, are
protected by barbed hairs that are intensely irritating.
They, too, can afford to be conspicuous. But a sweet and
edible caterpillar, if conspicuous, is eaten, and thus by the
elimination of the conspicuous the numerous dull green or
brown larvao have survived.

A walk through the Bird Gallery in the National
collection will afford examples of protective resemblance
among birds. Look, for example, at the Kentish plover
with its eggs and young — faithfully reproduced in our
frontispiece — and the way in which the creature is thus
protected in early stages of its life will be evident. The
stone-curlew, the ptarmigan, and other birds illustrate the
same fact, which is also seen with equal clearness in many
mammals, the hare l^eing a familiar example.

Many oceanic organisms are protected through general
resemblance. Some, like certain medusae, are transparent.
The pellucid or transparent sole of the Pacific (Achirus
pellucidus), a little fish about three inches long, is so trans-
parent that sand and seaweed can be seen distinctly
through its tissues. The salpa is transparent save for the
intestine and digestive gland, which are brown, and look
like shreds of seaweed. Other forms, like the physalia,
are cserulean blue. The exposed parts of flat-fish are
brown and sandy coloured or speckled like the sea-bottom ;
and in some the sand-grains seem to adhere to the skin.
So, too, with other fish. " Looking down on the dark back
of a fish," says Mr. A. R. Wallace, " it is almost invisible,
while to an enemy looking up from below, the light under
surface would be equally invisible against the light of
clouds and sky." Even some of the most brilliant and
gaudiest fish, such as the coral-fish (Chcstodon, Platyglossus,
and others), are brightly coloured in accordance with the
beautiful tints of the coral-reefs which form their habitat ;
the bright-green tints of some tropical forest birds being
of like import. No conception of the range of protective
.resemblance can be formed when the creatures are seen

84 Animal Life and Intelligence.

or figured isolated from their surroundings. The zehra is
a sufficiently conspicuous animal in a menagerie or a
museum ; and yet Mr. Galton assures us that, in the bright
starlight of an African night, you may hear one breathing
close by you, and be positively unable to see the animal.
A black animal would be visible ; a white animal would be
visible ; but the zebra's black and white so blend in the
dusk as to render him inconspicuous.

To cite but one more example, this time from the
invertebrates. Professor Herdman found in a rock-pool
on the west coast of Scotland " a peculiarly coloured speci-
men of the common sea-slug (Doris tuberculata) . It was
lying on a mass of volcanic rock of a dull-green colour,
partially covered with rounded spreading patches of a
purplish pink nullipore, and having numerous whitish
yellow Spirorbis shells scattered over it — the general effect
being a mottled surface of dull green and pink peppered
over with little cream-coloured spots. The upper surface
of the Doris was of precisely the same colours arranged in
the same way. . . . We picked up the Doris, and remarked
the brightness and the unusual character of its markings,
and then replaced it upon the rock, when it once more
became inconspicuous." *

Then, too, there are some animals with variable pro-
tective resemblance — the resemblance changing with a
changing environment. This is especially seen in some
Northern forms, like the Arctic hare and fox, which change
their colour according to the season of the year, being
brown in summer, white and snowy in winter. The chamse-
leon varies in colour according to the hue of its surround-
ings through the expansion and contraction of certain
pigment-cells ; while frogs and cuttle-fish have similar but
less striking powers. Mr. E. B. Poulton'sf striking and
beautiful experiments show that the colours of caterpillars

* Proceedings Liverpool Biological Society, 1889.

t Since this chapter was written, Mr. Poulton has published his interesting
and valuable work on "The Colours of Animals," from which I have con-
trived to insert one or two additional examples.

Variation and Natural Selection. 85

and chrysalids reared from the same brood will vary accord-
ing to the colour of their surroundings.

If this process of protective resemblance be carried far,
the general resemblance in hue may pass into special
resemblance to particular objects. The stick-insect and

Fig. 18. — Caterpillar of a moth (Ennomos tiliaria) on an oak-spray. (From
an exhibit iu the British Natural History Museum.)

the leaf-insect are familiar illustrations, though no one
who has not seen them in nature can realize the extent of
the resemblance. Most of us have, at any rate, seen the
stick-caterpillars, or loopers (Fig. 18), though, perhaps, few

86 Animal Life and Intelligence.

have noticed how wonderful is the protective resemblance
to a twig when the larva is still and motionless, for the
very reason that the resemblance is so marked that the
organism at that time escapes, not only casual observation,
but even careful search. Fig. 19 gives a representation
of a locust with special protective resemblance to a leaf —
not a perfect leaf, but a leaf with fungoid blotches. This
insect and the stick-caterpillar may be seen in the insect
exhibits on the basement at South Kensington, having
been figured from them by the kind permission of Professor
Flower.

Fig. 19. — A locust (Cycloptera speculata) which closely resembles a leaf.
(From an exhibit in the British Natural History Museum.)

Perhaps one of the most striking instances of special
protective resemblance is that of the Malayan leaf-butterfly
(Kallima paralecta). So completely, when the wings are
closed, does this insect resemble a leaf that it requires a
sharp eye to distinguish it. These butterflies have, more-
over, the habit of alighting very suddenly. As a recent
observer (Mr. S. B. T. Skertchly) remarks, they " fly rapidly
along, as if late for an appointment, suddenly pitch, close
their wings, and become leaves. It is generally done so
rapidly that the insect seems to vanish." * Instances might

* Ann. and Mag. Nat. Hist., September, 1889, p.. 209, quoted by Poulton,
" Colours of Animals," p. 55.

Variation and Natural Selection. 87

be multiplied indefinitely. Mr. Guppy thus describes a
species of crab in the Solomon Islands : " The light purple
colour of its carapace corresponds with the hue of the coral
at the base of the branches, where it lives ; whilst the light
red colour of the big claws, as they are held up in their
usual attitude, similarly imitates the colour of the branches.
To make the guise more complete, both carapace and claws
possess rude hexagonal markings which correspond exactly
in size and appearance with the polyp-cells of the coral." *

When the special protective resemblance is not to an
inanimate object, but to another organism, it is termed
mimicry. It arises in the following way : —

Many forms, especially among the invertebrates, escape
elimination by enemies through the development of offen-
sive weapons (stings of wasps and bees), a bitter taste (the
Heliconidae among butterflies), or a hard external covering
(the weevils among beetles). The animals which prey
upon these forms learn to avoid these dangerous, nasty,
or indigestible creatures ; and the avoidance is often in-
stinctive. It thus becomes an advantage to other forms,
not thus protected, to resemble the animals that have these
characteristics. Such resemblance is termed mimicry,
concerning which it must be remembered that the mimicry
is unconscious, and is reached by the elimination of those
forms which do not possess this resemblance. Thus tlie
Leptalis, a perfectly sweet insect, closely resembles the
Methona, a butterfly producing an ill-smelling yellow fluid.
The quite harmless Clytus arietis, a beetle, resembles, not
only in general appearance, but in its fussy walk, a
wasp. The soft-skinned Dollops, a longicorn, resembles the
strongly encased Pachyrhyncus orUfex, a weevil. The not
uncommon fly Eristalis tenax (Fig. 20), is not unlike a bee,
and buzzes in an unpleasantly suggestive manner.f

* Nature, vol. xxxv. p. 77.

f Many other instances might be added. The hornet clear-wing moth
(Sphecia apiformis) mimics the hornet or wasp; the narrow-bordered bee-
hawk moth (Sesia ~bombyliformis) mimics a bumble-bee. These insects may
be seen in the lepidoptera drawers in the Natural History Museum. But
perhaps the most wonderful instance of insect-mimicry is that observed

Animal Life and Intelligence.

Mimicry is not confined to the Invertebrates. A harm-
less snake, the eiger-eter of Dutch colonists at the Cape,
subsists mainly or entirely on eggs. The mouth is almost
or quite toothless ; but in the throat hard-tipped spines
project into the gullet from the vertebrae of the column in
this region. Here the egg is broken, and there is no fear
of losing the contents. Now, there is one species of this
snake that closely resembles the berg-adder. The head
has naturally the elongated form characteristic of the
harmless snakes. But when irritated, this egg-eater flattens
it out till it has the usual viperine shape of the " club "
on a playing-card. It coils as if for a spring, erects its
head with every appearance of anger, hisses, and darts
forward as if to strike its fangs into its foe, in every way
imitating an enraged berg-adder. The snake is, however,
quite harmless and inoffensive.*

Here we have mimicry both in form and habit. Another
case of imperfect but no doubt effectual mimicry is given
by Mr. W. Larden, in some notes from South America. f
Speaking of the rhea, or South American ostrich, he
says, " One day I came across an old cock in a nest that
it had made in the dry weeds and grass. Its wings and
feathers were loosely arranged, and looked not unlike a
heap of dried grass ; at any rate, the bird did not attract
my attention until I was close on him. The long neck was
stretched out close along the ground, the crest feathers
were flattened, and an appalling hiss greeted my approach.
It was a pardonable mistake if for a moment I thought
I had come across a huge snake, and sprang back hastily
under this impression."

Protective resemblance and mimicry have been con-
by Mr. W. L. Sclater, and given by Mr. E. B. Ponlton, in his " Colours of
Animals " (p. 252), where a (probably) homopterous insect mimics a leaf-cutting
ant, together with its leafy burden — a membranous expansion in the mimic
closely resembling the piece of leaf carried by the particular kind of ant he
resembles.

* The late Mr. H. "W. Oakley .first drew my attention to this snake.
Since then Mr. Hammond Tooke has described the facts in Nature, vol. xxxiv.
p. 547.

f Nature, vol. xlii. p. 115.

Variation and Natural Selection. 89

sidered at some length because, on the hypothesis of
natural selection, they admirably illustrate the results
which may be reached through long-continued elimination
by enemies.

Sufficient has now been said to show that this form of
elimination is an important factor. We are not at present
considering the question how variations arise, or why they
should take any particular direction. But granting the
fact that variations may and do occur in all parts of the
organism, it is clear that, in a group of organisms sur-
rounded by enemies, those individuals which varied in the
direction of swiftness, cunning, inconspicuousness,* or re-
semblance to protected forms, would, other things being
equal, stand a better chance of escaping elimination.

Elimination by competition is, as Darwin well points
out, keenest between members of the same group and
among individuals of the same species, or between different
groups or different species which have, so to speak, similar
aims in life. While enemies of various kinds are preying
upon weaker animals, and thus causing elimination among
them, they are also competing one with another for the
prey. While the slower and stupider organisms are suc-
cumbing to their captors, and thus leaving more active and
cunning animals in possession of the field, the slower and
stupider captors, failing to catch their cunning and active
prey, are being eliminated by competition. While protec-
tive resemblance aids the prey to escape elimination by
enemies, a correlative resemblance, called by Mr. Poulton
aggressive resemblance, in the captors aids them in stealing
upon their prey, and so gives advantage in competition.
Thus the hunting spider closely resembles the flies upon
which he pounces, even rubbing his head with his fore legs
after their innocent fashion.

* Since the above was written and sent to press, there has been added, at
the Natural History Museum, in the basement hall, a case illustrating the
adaptation of external coleuring to the conditions of life. All the animals,
birds, etc., there grouped were collected in the Egyptian desert, whence also
the rocks, stones, and sand on which they are placed were brought. Though
somewhat crowded, they exemplify protective resemblance very well.

90 Animal Life and Intelligence.

As in the case of protective resemblance, so, too, in its
aggressive correlative, the resemblance may be general or
special, or may reach the climax of mimicry. And since
the same organism is not only a would-be captor, but
sometimes an unwilling prey, the same resemblance may
serve to protect it from its enemies and to enable it to
steal upon its prey. The mantis, for example, gains
doubly by its resemblance to the vegetation among which
it lives. Certain spiders, described by Mr. H. 0. Forbes, in
Java, closely resemble birds'-droppings. This may serve
to protect them from elimination by birds; but it also
enables them to capture without difficulty unwary butter-
flies, which are often attracted by such excreta. A parasitic
fly (VoluceUa bombylans) closely resembles (Fig. 20) a
bumble-bee (Bombus muscorum), and is thus enabled to enter
the nest of the bee without molestation. Its larvae feed
upon the larvae of the bee. The cuckoo bee Psithyrus
rupestris, an idle quean, who collects no pollen, and has
no pollen-baskets, steals into the nest of the bumble-bee
Bombus lapidarius, and lays her eggs there. The re-
semblance between the two is very great, and it not only
enables the mother bee to enter unmolested, but the
young bees, when they are hatched, to escape. Another
bee (Nomada solidaginis), which plays the cuckoo on
Halictus cylindricus, does not resemble this bee, but is
wasp-like, and thus escapes molestation, not because it
escapes notice, but because it looks more dangerous than it
really is.*

Many are the arts by which, in keen competition,
organisms steal a march upon their congeners — not, be it
remembered, through any conscious adaptation, but through
natural selection by elimination. Mr. Poulton describes
an Asiatic lizard (Phrynocephalus mystaceus) in which the
" general surface resembles the sand on which it is found,
while the fold of their skin at each angle of the mouth is
of a red colour, and is produced into a flower-like shape

* I have to thank Mr. H. A. Francis for drawing my attention to this,
and showing me the insects in his cabinet.

Variation and Natural Selection. 91

exactly resembling a little red flower which grows in the
sand. Insects, attracted by what they believe to be flowers,
approach the mouth of the lizard, and are, of course,
captured."* The fishing frog, or angler-fish, is possessed
of filaments which allure small fry, who think them
worms, into the neighbourhood of the great mouth in
which they are speedily engulfed ; and certain deep-sea

Fig. 20.— Mimicry of bees by flies.

a, 6, Bombus muscorum ; c, d, Volucella bombylans ; e, Eristalis tenax ; f, Apis mellifica.
The underwings of the hive bee (f) were invisible'in the photograph from which the figure was
drawn. (From an exhibit in the British Natural History Museum.)

forms discovered during the Challenger expedition have the
lure illumined by phosphorescent light.

We need say no more in illustration of the resem-
blances which have enabled certain organisms to escape
elimination by competition. Once more, be it understood

* " Colours of Animals," p. 73.

92 Animal Life and Intelligence.

that we are not at present considering how any of these
resemblances have been brought about ; we are merely
indicating that, given certain resemblances, advantageous
either for captor or prey, those organisms which possess
them not will have to suffer elimination — elimination by
enemies, or else elimination by competition.

The interaction between these two kinds of elimination
is of great importance. Hunters and hunted are both, so
to speak, playing the game of life to the best of their
ability. Those who fail on either side are weeded out ; and
elimination is carried so far that those who are only as
good as their ancestors are placed at a disadvantage as
compared with their improving congeners. The standard
of efficiency is thus improving on each side ; and every
improvement on the one side entails a corresponding
advance on the other. Nor is there only thus a competition
for subsistence, and arising thereout a gradual sharpening
of all the bodily and mental powers which could aid in
seeking or obtaining food ; there is also in some cases a
competition for mates, reaching occasionally the climax of
elimination by battle. There is, indeed, competition for
everything which can be an object of appetence to the brute
intelligence; and, owing to the geometrical tendency in
multiplication — the law of increase — -the competition is
keen and unceasing.

Such, then, in brief, are the three main modes of
elimination : elimination by physical and climatic condi-
tions ; elimination by enemies ; elimination by competition.
Observe that it is a differentiating process. Unlike the
indiscriminate destruction before alluded to, the incidence
of which is on all alike, good, bad, and indifferent, it
separates the well-adapted from the ill-adapted, dooming
the latter to death, and allowing the former to survive and
procreate their kind. The destruction is not indiscriminate,
but differential.

Let us now turn to cases of selection, properly so called,
where Nature is in some way working at the other end of
the scale ; where her method is not the elimination of the

Variation and Natiiral Selection. 93

unfit, but the selection of the fit. Such a case may be
found on Darwin's principles in brightly coloured flowers
and fruits. " Flowers," he says, "rank amongst the most
beautiful productions of nature; but they have been
rendered conspicuous in contrast with the green leaves,
and, in consequence, at the same time beautiful, so that
they may be easily observed by insects. I have come to
this conclusion from finding it an invariable rule that,
when a flower is fertilized by the wind, it never has a gaily
coloured corolla. Several plants habitually produce two
kinds of flowers — one kind open and coloured, so as to
attract insects ; the other closed, not coloured, destitute of
nectar, and never visited by insects. Hence we may con-
clude that, if insects had not been developed on the face of
the earth, our plants would not have been decked with
beautiful flowers, but would have produced only such poor
flowers as we see on our fir, oak, nut, and ash trees, on
grasses, spinach, docks, and nettles, which are all fertilized
through the agency of the wind. A similar line of argu-
ment holds good with fruits ; that a ripe strawberry or
cherry is as pleasing to the eye as to the palate ; that the
gaily coloured fruit of the spindle-wood tree, and the scarlet
berries of the holly, are beautiful objects, — will be admitted
by every one. But this beauty serves merely as a guide
to birds and beasts, in order that the fruit may be devoured
and manured seeds disseminated : I infer that this is the
case from having as yet found no exception to the rule
that seeds are always thus disseminated when embedded
within a fruit of any kind (that is, within a fleshy or pulpy
envelope), if it be coloured of any brilliant tint, or rendered
conspicuous by being white or black." *

Here we have a case of the converse of elimination — a
case of genuine selection under nature. But even here the
process of elimination also comes into play, for the visita-
tions of flowers by insects involve cross-fertilization. The
flowers of two distinct individuals of the same species of
plants in this manner fertilize each other ; and the act of

* " Origin of Species," p. 161.

94 Animal Life and Intelligence.

crossing, as Darwin firmly believed, though it is doubted
by some observers nowadays, gives rise to vigorous seed-
lings, which consequently would have the best chance of
flourishing and surviving — would best resist elimination by
competition. So that we here have the double process at
work; the fairest flowers being selected by insects, and
those plants which failed to produce such flowers being
eliminated as the relatively unfit.

If we turn to the phenomena of what Darwin termed
sexual selection, we find both selection and elimination
brought into play. By the law of battle, the weaker and
less courageous males are eliminated so far as the con-
tinuation of their kind is concerned. By the individual
choice of the females (on Darwin's view, by no means
universally accepted), the finer, bolder, handsomer, and
more tuneful wooers are selected.

Let us again hear the voice of Darwin himself. " Most
male birds," he says, "are highly pugnacious during the
breeding season, and some possess weapons especially
adapted for fighting with their rivals. But the most
pugnacious and the best-armed males rarely or never
depend for success solely on their power to drive away or
kill their rivals, but have special means for charming the
female. With some it is the power of song, or of emitting
strange cries, or of producing instrumental music ; and the
males in consequence differ from the females in their vocal
organs or in the structure of certain feathers. From the
curiously diversified means for producing various sounds,
we gain a high idea of the importance of this means of
courtship. Many birds endeavour to charm the females
by love-dances or antics, performed on the ground or in
the air, and sometimes at prepared places. But ornaments
of many kinds, the most brilliant tints, combs and wattles,
beautiful plumes, elongated feathers, top-knots, and so
forth, are by far the commonest means. In some cases,
mere novelty appears to have acted as a charm. The
ornaments of the males must be highly important to them,
for they have been acquired in not a few cases at the cost

Variation and Natural Selection. 95

of increased danger from enemies, and even at some loss
of power in fighting with their rivals.* . . . What, then,
are we to conclude from these, facts and considera-
tions? Does the male parade his charms with so much
pomp and rivalry for no purpose? Are we not justified
in believing that the female exerts a choice, and that
she receives the addresses of the male who pleases her
most ? " f

Here again, then, we have the combined action of elimi-
nation and selection. And now we may note that selec-
tion involves intelligence — involves the play of appetence
and choice. Hence it is that, when we come to consider
the evolution of human-folk, the principle of elimination is
so profoundly modified by the principle of selection. Not
only are the weaker eliminated by the inexorable pressure
of competition, but we select the more fortunate individuals
and heap upon them our favours. This enables us also to
soften the rigour of the blinder law ; to let the full stress
of competitive elimination fall upon the worthless, the idle,

^ the profligate, and the vicious ; but to lighten its incidence

^ on the deserving but unfortunate.

* Both selection and elimination occurring under nature,

\^\ but elimination having by far the wider scope, we may now
inquire what will be their effect as regards the three modes
of variation — advantageous, disadvantageous, and neutral.
It must be remembered that these modes are relative and
dependent upon circumstances, so that variations, neutral
under certain conditions, may become relatively disadvan-
tageous under other conditions. Selection clearly leads to
the preservation of advantageous variations alone, and
these variations are advantageous in so far as they meet
the taste of the selecting organism. For selection depends
upon individual choice; and uniformity of selection is
entirely dependent upon uniformity in the standard of
taste. If, as Darwin contends, the splendid plumage and
tuneful notes of male birds are the result of a selection of
mates by the hens, there must be a remarkable uniformity
* "Descent of Man," summary of chap. xvi. pt. ii. t Ibid. chap. xiv.

96 Animal Life and Intelligence.

of taste among the hens of each particular species, since
there is a uniformity of coloration among the cock-birds.
It may be said that in all their mental endowments there
is greater uniformity among animals than among men ; and
it is true that individuation has not been carried so far in
them as in human-folk. Still, careful observers of animals
see in them many signs of individual character ; and this
uniformity in the standard of taste in each species of
birds seems to many naturalists a real difficulty in the
way of the acceptance of sexual selection. We shall,
however, return to this point. For the present it is
clear that selection chooses out advantageous variations,
that the advantage is determined by the taste of the
selector, and that uniform selection implies uniformity of
taste.

Turning to elimination, it is clear that it begins by
weeding out, first the more disadvantageous, then the less
disadvantageous variations. It leaves both the advan-
tageous and the neutral in possession of the field. I
imagine that many, perhaps most, of the variations
tabulated by Mr. Wallace and other observers belong to
the neutral category. Their fluctuating character seems
to indicate that this is so. In any case, they are
variations which have so far escaped elimination. And
I think they are of great and insufficiently recognized
importance. They permit, through interbreeding, of end-
less experiments in the combination of variations, some of
which cannot fail to give favourable results.

It is just possible that it may be asked — If in natural
elimination there is nothing more than the weeding out
of the unfit and the suppression of disadvantageous varia-
tions, where is the possibility of advance ? The standard
may thus be maintained, but where is the possibility of
progress ? Such an objection would, however, imply forget-
fulness of the fact that all the favourable variations remain
to leaven the residual lump. Given a mean, with plus and
minus variations : if in any generations the minus varia-
tions are got rid of, the mixture of the mean with the plus

Variation and Natural Selection. 97

variations will give a new mean nearer the plus or advan-
tageous end of the scale than the old mean. By how
much the favourable variations tend to raise the mean
standard, by so much will the race tend to advance.
But in this process I see no reason why the neutral
variations should be eliminated, except in so far as, in
the keen struggle for existence, they become relatively
unfavourable.

It is clear, however, that the intercrossing and inter-
breeding which occurs between average individuals on the
one hand, and those possessing favourable variations on
the other, while it tends gradually to raise the mean
standard, tends also at the same time to reduce the advan-
tageous variations towards the mean. It must tend to check
advance by leaps and bounds, and to justify the adage,
Natura nil fatit per saltum. At the same time, it will
probably have a greater tendency to reduce to a mean level
neutral variations indefinite in direction than advantageous
variations definite in direction. Still, it is a most im-
portant factor, and one not to be neglected. It tends to
uniformity in the species, and checks individualism. It
may act as a salutary brake on what we may figuratively
term hasty and ill-advised attempts at progress. And at
the same time, it favours repeated new experiments in the
combination of variations, occasionally, we may suppose,
with happy results.

But it does more than this. It tends to check, and, if)
the offspring always possessed the blended character of bothf
parents, would be absolutely fatal to, divergence of character \
within the interbreeding members of a species. And yet 1
no fact is more striking than this divergence of character.'
It is seen in the diversified products of human selection ;
for example, among pigeons. It is seen in the freedom of
nature. Mr. Wallace gives many examples. " Among
our native species," he says, "we see it well marked in the
different species of titmice, pipits, and chats. The great
titmouse, by its larger size and stronger bill, is adapted to
feed on larger insects, and is even said sometimes to kifl

H

98 Animal Life and Intelligence.

small and weak birds. The smaller and weaker coal-tit-
mouse has adopted a more vegetarian diet, eating seeds as
well as insects, and feeding on the ground as well as among
trees. The delicate little blue titmouse, with its very small
bill, feeds on the minutest insects and grubs, which it
extracts from crevices of bark and from the buds of fruit
trees. The marsh-titmouse, again, has received its name
from the low and marshy localities it frequents ; while the
crested titmouse is a Northern bird, frequenting especially
pine forests, on the seeds of which trees it partially feeds.
Then, again, our three common pipits — the tree-pipit, the
meadow-pipit, and the rock-pipit, or sea-lark — have each
occupied a distinct place in nature, to which they have
become specially adapted, as indicated by the different
form and size of the hind toe and claw in each species.
So the stone-chat, the whin-chat, and the wheat-ear are all
slightly divergent forms of one type, with modifications in
the shape of the wing, feet, and bill adapting them to
slightly different modes of life." * There is scarcely a
genus that does not afford examples of divergent species.
The question then naturally occurs — How have these
divergent forms escaped the swamping effects of inter-
crossing ?

That perfectly free intercrossing, between any or all of
the individuals of a given group of animals, is, so long as
the characters of the parents are blended in the offspring,
fatal to divergence of character, is undeniable. Through
the elimination of less favourable variations, the swiftness,
strength, and cunning of a race may be gradually improved.
But no form of elimination can possibly differentiate the
group into swift, strong, and cunning varieties, distinct
from each other, so long as all three varieties freely inter-
breed, and the characters of the parents blend in the off-
spring. Elimination may and does give rise to progress in
any given group as a group ; it does not and cannot give
rise to differentiation and divergence, so long as interbreed-
ing with consequent interblending of characters be freely

* " Darwinism," p. 108.

Variation and Natural Selection. 99

permitted. Whence it inevitably follows, as a matter of
simple logic, that where divergence has occurred, inter-
crossing and interblending must in some way have been
lessened or prevented.

Thus a new factor is introduced, that of isolation, or
segregation. And there is no questioning the fact that it is
of great importance.* Its importance can, indeed, only be
denied by denying the swamping effects of intercrossing,
and such denial implies the tacit assumption that inter-
breeding and interblending are held in check by some form
of segregation. The isolation explicitly denied is implicitly
assumed.

There are several ways in which isolation, or segregation,
may be effected. Isolation by geographical barriers is the
most obvious. A stretch of water, a mountain ridge, a
strip of desert land, may completely, or to a large extent,
prevent any intercrossing between members of a species on
either side of the barrier. The animals which inhabit the
several islands of the Galapagos Archipelago are closely
allied, but each island has its particular species or well-
marked varieties. Intercrossing between the several
varieties on the different islands is prevented, and diver-
gence is thus rendered possible and proceeds unchecked.
It is said that in the Zuyder Zee a new variety of herrings,
the fry of which are very small compared with open-sea
herrings, is being developed. And the salmon introduced
into Tasmania seem to be developing a fresh variety
with spots on the dorsal fin and a tinge of yellow on the
adipose fin. In the wooded valleys of the Sandwich Islands
there are allied but distinct species of land-shells. The
valleys that are nearest each other furnish the most nearly
related forms, and the degree of divergence is roughly
measured by the number of miles by which they are
separated. Here there is little or no intercrossing between

* Its importance in artificial selection was emphasized by Darwin : " The
prevention of free crossing, and the intentional matching of individual animals,
are the corner-stones of the breeder's art "(" Animals and Plants under
Domestication," ii. 62).

ioo Animal Life and Intelligence.

the slow-moving molluscs in adjoining valleys ; none at all
between those at any distance apart.

But even if there are no well-marked physical barriers,
the members of a species on a continent or large island
tend to fall into local groups, between which, unless the
animal be of a widely ranging habit, there will be little
intercrossing. Hence local varieties are apt to occur, and
varieties show the first beginnings of that divergence which,
if carried further and more deeply ingrained, results in the
differentiation of species. Geographically, therefore, we
may have either complete isolation or local segregation,
and in both cases the possibility of divergence.

Another mode of segregation arises also out of
geographical conditions. If variations of habits occur
(and structure is closely correlated with habit) such that
certain individuals take to the mountains, others to the
plains or valleys ; or that certain individuals take to the
forests, others to the open country; the probabilities are
that the forest forms will interbreed frequently with each
other, but seldom with those in the open, and so with the
other varieties. The conditions of forest life or mountain
life being thus similar throughout a large area, and life
being through elimination slowly but surely adapted to its
environment, there might thus arise two distinct varieties
scattered throughout the length and breadth of the area,
the one inhabiting the mountains, the other the forests.
In illustration of this mode of segregation, we may take
the case of two species of rats which have recently been
found by Mr. C. M. Woodford on one of the Solomon
Islands. These two quite distinct species are regarded by
Mr. Oldfield Thomas as slightly modified descendants of
one parent species, the modifications resulting from the
fact that of this original species some individuals have
adopted a terrestrial, others an arboreal life, and their
respective descendants have been modified accordingly.
Thus Mus rex lives in trees, has broad foot-pads, and a
long rasp-like, probably semi-prehensile, tail ; while Mus
imperator lives on the ground, has smaller pads, and a

Variation and Natural Selection. 101

short, smooth tail. The segregation of these two species
has probably been effected by the difference of their mode
of life, and each has been adapted to its special environment
through the elimination of those individuals which were
not in harmony with the condition of their life. It is
probable that this mode of segregation has been an im-
portant one. And it is clear that in many cases competition
would be a co-operating factor in this process, weaker
organisms being forced into otherwise uncongenial habitats
through the stress of competitive elimination, the weaker
forms not perishing, but being eliminated from more
favoured areas.

Protective coloration may also be a means of segrega-
tion. A species of insects having no protective resemblance
might vary in two directions — in the direction of green
tints, assimilating their hue to that of vegetation ; and in
the direction of sandy or dull earthy colours, assimilating
them to the colour of the soil. In the one variety elimina-
tion would weed out all but the green forms, and these
would be left to intercross. In the other variety, green
forms would be eliminated, dull-brown forms being left to
interbreed. Stragglers from one group into the other
would stand a chance of elimination before interbreeding
was effected.*

In the case of birds whose freedom of flight gives them
a wide range, sometimes almost a world-wide range, it
would seem at first sight that their facilities for inter-
breeding and intercrossing are so great that divergence is
well-nigh impossible. And yet the examples of divergence I
cited from Mr. Wallace were taken from birds, and it is well
known that divergence is particularly well shown in this
class. But when the habits of birds are studied attentively,
it is found that, wide as is their range, their breeding area
is often markedly restricted. The sanderling and knot

* From the absence of interblending in some cases (to be considered
shortly), both brown and green forms may be produced ; and under certain
circumstances, even a power of becoming either brown or green in the
presence of appropriate stimuli.

102 Animal Life and Intelligence.

range freely during the winter throughout the Northern
hemisphere; but their breeding area is restricted to
the north polar region. The interbreeding within this
area keeps the species one and homogeneous, notwith-
standing its wide range, and, at the same time, prevents
intercrossing with allied species with different breeding-
grounds.

Another most important mode of segregation among
animals arises out of habitual or instinctive preferences.
Where varieties are formed there is a tendency for like to
breed with like. In the Falkland Islands the differently
coloured herds of cattle, all descended from the same stock,
keep separate, and interbreed with each other, but not with
individuals outside their own colour-caste. If two flocks
of merino sheep and heath sheep be mixed together, they
do not interbreed. In the Forest of Dean and in the New
Forest, the dark and pale coloured herds of fallow deer
have never been known to intermingle.* Here we have a
case of selective segregation through preferential mating, and
may find therein the basis of sexual selection in its higher
ranges as advocated by Darwin.

The question of sexual selection will, however, be briefly
considered in the chapter on "Organic Evolution." At
present what we have to notice is that, through preferential
mating, segregation is effected. The forms that interbreed
have a distinguishing colour. From this it is but a step
to the possession, not merely of a distinguishing colour,
but of distinguishing colour-markings. Hence, through
preferential mating, may arise those special markings
which so frequently distinguish allied species. They not
only enable us to recognize species as distinct, but enable
the species which possess them to recognize the members
of their own kind. Mr. Wallace calls these diacritical
marks recognition-marks, and gives many illustrative
examples. f They are especially noticeable in gregarious
animals and in birds which congregate in flocks or which

* Wallace, " Darwinism," p. 172, where other examples are cited,
t Ibid. pp. 217, at seq.

Variation and Natural Selection. 103

migrate together. Mr. Wallace considers that they " have
in all probability been acquired in the process of differentia-
tion for the purpose of checking the intercrossing of allied
forms ; " for " one of the first needs of a new species would
be to keep separate from its nearest allies, and this could
be more readily done by some easily seen external mark
of difference." This language seems, however, to savour
of teleology (that pitfall of the evolutionist). The cart is
placed before the horse. The recognition-marks were, I
believe, not produced to prevent intercrossing, but inter-
crossing has been prevented because of preferential mating
between individuals possessing special recognition-marks.
To miss this point is to miss an important segregation-
factor. Undoubtedly, other tendencies co-operate in main-
taining the standard of the recognition-marks. Stragglers
who failed in the matter of recognition would get separated
from their fellows, and stand a greater chance of elimi-
nation by enemies ; young who failed in this respect would
be in like condemnation. Still, I cannot doubt that the
foundations of recognition-marks were laid in preferential
mating, and that in this we have an important factor in
segregation.

We may here note, in passing, as also arising out of
preference, how the selection of flowers by insects may
lead to segregation ; for insects seem often to have habitual
or instinctive colour-preferences. Flowers of similar colour
would be thus cross-fertilized, but would not intercross with
those of different colour, whence colour-varieties might
arise. It is important to note that in these cases there is
a psychological factor in evolution.

We have so far assumed that intercrossing of parents
and interblending of their characters in the offspring
always go together. This, we must now notice, is not
always the fact. If a blue-eyed Saxon marry a dark-eyed
Italian, the children will have blue eyes or dark eyes, not
eyes of an intermediate tint. The characters do not inter-
blend. The ancon, or otter-sheep, a breed with a long
body and short, bandy legs, appeared in Massachusetts as

IO4 Animal Life and Intelligence.

a chance sport in a single lamb. The offspring of this
ram were either ancons or ordinary sheep. The ancon
characters did not blend. Hence for a time a definite
breed was maintained. We may call this mode of isola-
tion isolation by exclusive inheritance.

A further mode of isolation or segregation, for which
Mr. Eomanes* claims a foremost, indeed, the foremost,
place, is physiological isolation as due to differential fertility.
One among the many variations to which organisms are
subject is a variation in fertility, which may reach the
climax of absolute sterility. But it is clear that a sterile
variation carries with it its own death-warrant, since the
sterile individual leaves no descendants to inherit its pecu-
liarity. Eelative infertility, too, unless it chances to be
correlated with some unusual excellence, would be no
advantage, would be transmitted to few descendants, and
would tend to be extinguished. The same is not true,
however, of differential fertility. "It is by no means
rare," said Darwin, f "to find certain males and females
which will not breed together, though both are known to
be perfectly fertile with other males and females." Mr.
Eomanes assumes, as a starting-point, the converse of
this, namely, that certain males and females will breed to-
gether, though they are infertile with all other members
of the species.

Suppose, then, a variety to arise which is perfectly
fertile within the limits of the varietal form, but im-
perfectly fertile or infertile with the parent species.
Such a variety would have to run the risks of those ill
effects which, as Darwin showed,}: are attendant upon close
interbreeding. But Mr. Wallace points out§ that these
ill effects may not be so marked under nature as they are
under domestication. Suppose, then, that it escapes these
ill effects. In this case, Mr. Eomanes urges, it would
neither be swamped by intercrossing nor die out on

* Journal of the Linnaean Society, vol. xix. No. 115 : " Zoology."
t " Animals and Plants under Domestication," p. 145.
J Ibid. chap. xvii. § " Darwinism," p. 326.

Variation and Natural Selection. 105

account of sterility. But although it could not be swamped
by intercrossing, still, if it arose sporadically, here a case,
there a case, and so on, the chances would be enormously
against the perpetuation of the variety, unless some co-
operating mode of segregation aided in bringing together
the varying individuals. If, for example, there were a
segregation of these variants in a particular habitat — all
the variants meeting in some definite locality for breeding
purposes ; or if there were a further segregation through
mutual preferences; or if, again, there were a further
segregation in time ; the variety might obtain a firm
footing. But without these co-operating factors it is clear
that if one male and one female in a hundred individuals
varied in this particular way, the chances would be at
least forty- nine to one against their happening to mate
together.

It is interesting to note that almost the only particular
example given by Mr. Eomanes in illustration of his theory
is one that involves the co-operation of one of these further
segregation-factors. Suppose, he says, the variation in
the reproductive system is such that the season of flower-
ing or of pairing becomes either advanced or retarded.
This particular variation being inherited, the variety breed-
ing, let us say, in May, the parent species in July, there
would arise two races, each perfectly fertile within its own
limits, but incapable of crossing with the other. Thus is
constituted "a barrier to intercrossing quite as effectual
as a thousand miles of ocean." Yes ! a time-barrier instead
of a space-barrier. The illustration is faulty, inasmuch as
it introduces a mode of segregation other than that in
question. I think it very improbable that differential
fertility alone, without the co-operation of other segregation-
factors, would give rise to separate varieties capable of
maintaining themselves as distinct species.

That distinct species are generally mutually infertile,
or more frequently still, that their male offspring are
sterile, is, however, an undoubted fact. But there are,
exceptions. Fertile hybrids between the sheep and the

io6 Animal Life and Intelligence.

goat seem to be well authenticated. Of rats Darwin
says that "in some parts of London, especially near
the docks, \vhere fresh rats are frequently imported, an
endless variety of intermediate forms may be found
between the brown, black, and snake rat, which are all
three usually ranked as distinct species." * Fertile hybrids
have been produced between the green-tinted Japanese and
the long-tailed Chinese pheasants. Mr. Thomas Moore,
of Fareham, in Hants, has been particularly successful in
producing a hybrid breed between the golden pheasant
(Thaumalia picta), whose habitat is Southern and South-
eastern China, and the Amherst pheasant (Thaumalia
amherstitz), which is found in the mountains of Yunnan
and Thibet. In answer to my inquiries, Mr. Moore kindly
informs me that he "has bred the half-bred gold and
Amherst pheasant, crossed them again with gold, anjl re-
crossed them with half-bred Amherst, and kept on crossing
until only a strain of the gold pheasant remained. The
result is that the birds so produced are far handsomer than
either breed, since the feathers composing their tiplets as
well as those under the chin are of so beautiful a colour
that they beggar description. They all breed most freely,
and are much more vigorous than the pure gold or Amherst,
and their tails reach a length of over three feet. They are
also exceedingly prolific. Out of a batch of forty-two eggs,
forty chickens were hatched out, of which thirty-seven were
reared to perfection."

Still, though there are exceptions, the general infertility
of allied species when crossed is a fact in strong contrast
with the marked fertility of varieties under domestication ;
concerning which, however, it should be noted that our
domesticated animals have been selected to a very large
extent on account of the freedom with which they breed
in confinement, and that domestication has probably a
tendency to increase fertility. The question, therefore,
arises — Is the infertility between species, and the general

* " Animals and Plants under Domestication," vol. ii. p. 65. For Darwin's
general conclusions on hybridism, see vol. ii. p. 162 of the same work.

Variation and Natural Selection. 107

sterility of their male offspring, a secondary effect of their
segregation? or is their segregation the direct effect of
their differential fertility? The former is the general
opinion ; the latter is held by Mr. Eomanes. He contends
that sterility is the primary distinction of species, other
specific characters being secondary, and regards it as a pure
assumption to say that the secondary differences between
species have been historically prior to the primary differ-
ence. I do not propose to discuss this question. While it
seems to me in the highest degree improbable that
differential fertility, apart from other co-operating factors,
has been or could be a practical mode of segregation, it
has probably been a not unimportant factor in association
with other modes of segregation or isolation. Suppose, for
example, two divergent local varieties were to arise in
adjacent areas, and were subsequently (by stress of com-
petition or by geographical changes) driven together into
a single area : we are justified in believing, from the
analogy of the Falkland Island cattle, the Forest of Dean
deer, and other similar observed habits, that preferential
breeding, kind with kind, would tend to keep them apart.
But, setting this on one side, let us say they interbreed.
If, then, their unions are fertile, the isolation will be
annulled by intercrossing — the two varieties will form one
mean or average variety. But if the unions be infertile,
the isolation will be preserved, and the two varieties will
continue separate. Suppose now, and the supposition is
by no means an improbable one, that this has taken place
again and again in the evolution of species : then it is
clear that those varietal forms which had continued to be
fertile together would be swamped by intercrossing ; while
those varietal forms which had become infertile would
remain isolated. Hence, in the long run, isolated forms
occupying a common area would be infertile. Or suppose,
once more, that, instead of the unions between the two
varietal forms being infertile, they are fertile, but give rise
to sterile (mule) or degenerate offspring, as is said to be
the case in the unions of Japanese and Ainos : then it is

io8 Animal Life and Intelligence.

clear that the sterile or degenerate offspring of such unions
would be eliminated, and intercrossing, even though it
occurred, would be inoperative while breeding within the
limits of the variety continued unchecked.

Sufficient has now been said concerning the modes of
isolation and segregation, geographical, preferential, and
physiological. We must now consider their effects. Where
the isolated varieties are under different conditions of life,
there will be, through the elimination of the ill-adapted in
each case, differential adaption to these different conditions.
But suppose the conditions are similar : can there be
divergence in this case ? The supposition is a highly
hypothetical one, because it postulates that all the con-
ditions, climatal, environmental, and competitive, are alike,
which would seldom, if ever, be likely to occur. Let us,
however, make the supposition. Let us suppose that an
island is divided into two equal halves by the submersion
of a stretch of lowland running across it. Then the only
possible causes of divergence would lie in the organisms
themselves * thus divided into two equal groups. We have
seen that variations may be advantageous, disadvantageous,
or neutral. The neutral form a fluctuating, unfixed,
indefinite body. But they afford the material with which
nature may make, through intercrossing, endless experi-
ments in new combinations, some of which may be profit-
able. Such profitable variations would escape elimination,
and, if not bred out by intercrossing, would be preserved.
In any case, the variety would tend to advance through
elimination as previously-indicated. But in the two equal
groups we are supposing to have become geographically
isolated, the chances are many to one against the same
successful experiments in combination occurring in each of
the two groups. Hence it follows that the progress or

* " In every case there are two factors, namely, the nature of the organism
and the nature of the conditions. The former seems to be much the more
important ; for nearly similar variations sometimes arise under, as far as we
can judge dissimilar conditions ; and, on the other hand, dissimilar variations
arise under conditions which appear to be nearly uniform" ("Origin of
Species," p. 6).

Variation and Natural Selection. 109

advance in the two groups, though analogous, would not be
identical, and divergence would thus be possible under
practically similar conditions of life.

In his observations on the terrestrial molluscs of the
Sandwich Islands, Mr. Gulick notes that different forms
are found in districts which present essentially the same
environment, and that there is no greater divergence when
the climatic conditions are dissimilar than there is when
those conditions are similar. As before noticed, the degree
of divergence is, roughly speaking, directly as the distance
the varietal forms are apart. Again, Darwin notes that
the climate and environment in the several islands of the
Galapagos group are much the same, though each island
has a somewhat divergent fauna and flora. These facts
lend countenance to the view that divergence can and does
occur under similar conditions of life, if there be isolation.
They seem, also, so far as they go, to negative the view -
that the species is moulded directly by the external con-
ditions. For, if this factor were powerful, it would over-
ride the effects of experimental combination of characters
when the conditions were similar, and would give rise
to well-marked varietal forms when the conditions were
diverse.

If we admit preferential breeding as a segregation-factor
(and arising out of it sexual selection, in a modified form,
as a determining one in the evolution of the plumage of
male birds), it is evident that the standard of recognition-
marks can only be maintained by a uniformity of preference
or taste. Still, the uniformity is not likely to be absolute.
In this matter, as in others, variations will occur, and
after the lapse of a thousand generations, in which elimina-
tion has been steadily at work, it is hardly probable that
the recognition standard would remain absolutely un-
changed. For, though there may not be any direct
elimination in this particular respect, there might well be
colour-eliminations in other (e.g. protective) respects, and
the mental nature would not remain quite unchanged.
Moreover, we know that secondary sexual characters are

no Animal Life and Intelligence.

remarkably subject to variation, as may be well seen in the
case of ruffs (Machetes pugnax) in the British Natural
History Museum. In the case of our two islands with
isolated faunas, therefore, if they formed separate breeding-
areas for birds, the chances would be many to one against
the change in the standard of recognition -marks being
identical in each area. Hence might arise those minute
but definite specific distinctions which are so noteworthy
in this class of the animal kingdom. Instance the Old and
New World species of teal, the Eastern and Western species
of curlew and whimbrel, and other cases numerous.* This,
in fact, is probably in many cases the true explanation of
the occurrence of representative species, slight specific
variations of the same form as it is traced across a conti-
nent or through an archipelago of islands.

The question has been raised, and of late a good deal
discussed, whether specific characters, those traits by
which species are distinguishable, are always of use to the
species which possess them. Here it is essential to define
what is meant by utility. Characters may be of use in
enabling the possessor to resist elimination; or, like the
colours of flowers, they may be of use in attracting insects,
and thus furthering selection ; or, like recognition-marks,
they may be of use in effecting segregation. This last form
of utility is apt to be overlooked or lost sight of. In speak-
ing of humming-birds, the Duke of Argyll says that " a crest
of topaz is no better in the struggle for existence than a
crest of sapphire. A frill ending in spangles of the emerald
is no better in the battle of life than a frill ending in
spangles of the ruby." But if these characters be recog-
nition-marks, they may be of use in segregation. They are
a factor in isolation. But it may be further asked — What
is the use of the segregation ? Wherein lies the utility of
the divergence into two forms ? This question, however,
involves a complete change of view-point. The question
before us is whether specific characters are of use to the

* See " Evolution without Natural Selection," by Charles Dixon. This
author's facts are valuable ; his theories are ill digested.

Variation and Natural Selection. 1 1 1

species which possesses them. To this question it is sufficient
to answer that they are useful in effecting or preserving
segregation, without which the species, as a distinct species,
would cease to exist. We are not at present concerned
with the question whether divergence in itself is useful or
advantageous. If it be pressed, we must reply that, although
divergence is undoubtedly of immense advantage to life in
general, enabling, as Darwin said, its varying and diver-
gent forms to become adapted to many and highly diversified
places in the economy of nature, still in many individual
cases it is neither possible nor in any respect necessary to
our conception of evolution to assign any grounds of utility
or advantage for the divergence itself.

In any case, we are dealing at present with the utility
of specific characters to the species which possess them ;
and under the head of utility we are including usefulness
in effecting or maintaining segregation. Now, we have
already seen that variations may be either advantageous
(useful), or neutral (useless), or disadvantageous (worse
than useless). The latter class we may here disregard;
elimination will more or less speedily dispose of them.
With regard to neutral (useless) variations, we must also
note that they may be correlated with variations of the
other two classes. If correlated with disadvantageous
variations, they will be eliminated along with them; if
correlated with advantageous variations, they will escape
elimination (or will be selected) together with them. There
remain neutral, or useless, variations, not correlated with
either of the other two classes. Are these in any cases
distinctive of species ?

It is characteristic of specific distinctions that they are
relatively constant. Elimination, selection, or preferential
breeding gives them relative fixity. On the other hand, it
is characteristic of neutral variations that they are incon-
stant. There is nothing to give them fixity. It is, of
course, conceivable that all the migrants to a new area
were possessed of a useless neutral character, which those
in the mother area did not possess ; or that such a useless

1 1 2 Animal Life and Intelligence.

character was in them preponderant, and by intercrossing
formed a less fluctuating, useless character than their pro-
genitors exhibited. Still, the extensive occurrence of such
neutral, or useless, characteristics would be in the highest
degree improbable. Our ignorance often prevents us from
saying in what particular way a character is useful. We
must neither, on the one hand, demand proof that this,
that, or the other specific character is useful, nor, on the
other hand, demand negative evidence (obviously impos-
sible to produce) that it is without utilitarian significance ;
but we may fairly request those who believe in the wide
occurrence of useless specific characters to tell us by what
means these useless characters have acquired their relative
constancy and fixity. A suggestion on this head will be
found in the next chapter.

We must now pass on to consider briefly a most im-
portant factor in the struggle for existence. Hitherto we
have regarded this struggle as uniform in intensity; we
must now regard it as variable, with alternations of good
times and hard times, and indicate the causes to which
such variations are due.

With variations of climate, such as we know to occur
from year to year, or from decade to decade, there are
variations in the productiveness of the soil ; and when we
remember how closely interwoven are the web and woof of
life, we shall see that the increased or diminished produc-
tiveness of any area will affect for good or ill all the life
which that area supports. The introduction of new forms
of life into an area, or their preponderance at certain
periods owing to climatic or other conditions particularly
favourable to them as opposed to other forms, may alter
the whole balance of life in the district. We are often
unable to assign any reason for the sudden increase or
diminution of the numbers of a species ; we can only pre-
sume that it is the result of some favourable or unfavour-
able change of conditions. Thus Mr. Alexander Becker *
has recently drawn attention to the fact that whereas for

* Nature, vol. xlii. p. 136.

Variation and Natural Selection. 113

several years various species of grasshoppers appeared in
great numbers in South-east Bussia, there came then one
year of sudden death for most of them. They were sitting
motionless on the grasses and dying. He gives similar
cases of butterflies for a while numerous, and then rare,
and states that a squirrel common near Sarepta suddenly
disappeared in the course of one summer, probably, he
adds, succumbing to some contagious disease. Such is the
nice balance of life, that the partial disappearance of a
single form may produce remarkable and little-expected
effects. Darwin amusingly showed how the clover crops
might be beneficially affected by the introduction of a
family of old maids into a parish. The clover is fertilized
by humble-bees, the bees are preyed upon by mice ; the
relations between cats and mice, and between old maids
and cats, are well known and familiar : more old maids,
more cats ; more cats, less mice ; less mice, more humble-
bees ; more humble-bees, better fertilization. A little thing
may modify the balance of life, and increase or diminish
the struggle for existence, and the rigour of the process of
elimination.

But when we take a more extended view of the matter,
and include secular changes of climate, the possible range
of variation in the struggle for existence is seen to be
enormously increased. It is well known to those who have
followed the progress of geology, that in early Kainozoic
times a mild climate extended to within the Arctic circle,
while during the glacial epoch much of the north tempe-
rate zone was fast locked in ice, and the climate of the
northern hemisphere was profoundly modified. The animals
in the north temperate zone were driven southwards.*
Not only was there much elimination from the severe
climatic conditions, but the migrants were driven south-
wards into areas already well stocked with life, and the

* We may here note, in passing, the fact that the changes of life-forms in a
succession of beds points jn nine cases out of ten rather to substitution through
migration than to transmutation. Still, there are notable cases of trans-
mutation, as in the fresh-water Planorbes of Steinhem, in Wittenberg (described,
after Hilgendorf, by 0. Schmidt, " The Doctrine of Descent," p. 96).

I

1 14 Animal Life and Intelligence.

competition for means of subsistence in these areas must
have been rendered extremely severe. Elimination was at
a maximum. Then followed the withdrawal of glacial
conditions. The increasing geniality of the climate allowed
an expansion of life within a given area, and the with-
drawal of snow and ice further and further north set free
new areas into which this expanding life could migrate
and find subsistence. The hard times of the glacial period
were succeeded by good times of returning warmth and an
expanding area ; and if, as some geologists believe, there
was an inter-glacial period (or more than one such period)
in the midst of the Great Ice Age, then hard times and
good times alternated during the glacial epoch.

Expansion and contraction of life-areas have also been
effected again and again in the course of geological history
by elevations and subsidences of the land. At the beginning
of Mesozoic times much of Europe was dry land. In
Triassic and Khaetic times there were lakes in England and
in Germany, and a warm Mediterranean Sea to the south.
Subsidence of the European area brought with it a lessened
land-area and an increased sea-area : bad times and in-
creased competition for land animals ; good times and
a widening life-area for marine forms of life. This con-
tinued, with minor variations, till its culmination in the
Cretaceous period. Then came the converse process : the
land-areas increased, the sea was driven back. A good
time had come for terrestrial life ; the marine inhabitants
of estuaries and inland seas felt the pressure of increased
competition in a lessening area. And so there emerged
the continental Europe of the beginning of the Kainozoic
era. And it is scarcely necessary to remind those who
are in any degree conversant with geology that during
tertiary times there have been alternate expansions and
contractions of life-areas, marine and terrestrial, the former
bringing good times, the latter hard times and a heightened
struggle for existence.

Now, what would be the result of this alternation of
good times and hard times ? During good times varieties,

Variation and Natiiral Selection. 115

which would be otherwise unable to hold their own, might
arise and have time to establish themselves. In an ex-
panding area migration would take place, local segregation
in the colonial areas would be rendered possible, differential
elimination in the different migration-areas would produce
divergence. There would be diminished elimination of
neutral variations, thus affording opportunities for experi-
mental combinations. In general, good times would favour
variation and divergence.

Intermediate between good times and hard times would
come, in logical order, the times in which there is neither
an expansion nor a contraction of the life-area. One -may
suppose that these are times of relatively little change.
There is neither the divergence rendered possible by the
expansion of life-area, nor the heightened elimination
enforced by the contraction of life-area.* Elimination is
steadily in progress, for the law of increase must still
hold good. Divergence is still taking place, for the law of
variation still obtains. But neither is at its maximum.
These are the good old-fashioned times of slow and steady
conservative progress. They are, perhaps, well exemplified
by the fauna of the Carboniferous period, and it is not at
all improbable that we are ourselves living in such a quiet,
conservative period.

On the other hand, hard times would mean increased
elimination. During the exhibitions at South Kensington
there were good times for rats. But when the show was
over, there followed times that were cruelly hard. The
keenest competition for the scanty food arose, and the poor
animals were forced to prey upon each other. " Their
cravings for food," we read in Nature, " culminated in a
fierce onslaught on one another, which was evidenced by
the piteous cries of those being devoured. The method of
seizing their victims was to suddenly make a raid upon

* I would ask historians whether there have not been, in English history,
good times of free and beneficial divergence exemplified in diverse intellectual
activity, hard times of rigorous elimination, and intermediate times of placid,
somewhat humdrum conservatism.

n6 Animal Life and Intelligence.

one weaker or smaller than themselves, and, after over-
powering it by numbers, to tear it in pieces." Elimination
by competition, passing in this way into elimination by
battle, would, during hard times, be increased. None but
the best organized and best adapted could hope to escape.
There would be no room for neutral variations, which, in
the keenness of the struggle, would be relatively disadvan-
tageous. Slightly divergent varieties, before kept apart
through local segregation, would be brought into com-
petition. The weakest would in some cases be eliminated.
In other cases, the best-adapted individuals of each variety
might survive. If their experiments in intercrossing,
should such occur, gave rise to fertile offspring, more
vigorous and better adapted than either parent-race, these
would survive, and the parent-forms would be eliminated.
But if such experiments in intercrossing gave rise to
infertile, weakly offspring, these would be eliminated. Thus
sterility between species would become fixed. Wherever,
during the preceding good times, divergence had taken
place in two different directions of adaptation, and some
intermediate forms, fairly good in both directions, had been
able to escape elimination, the chances are that these inter-
mediates would be hi hard times eliminated, and the
divergent forms left in possession of the field. Wherever,
during good times, a species had acquired or retained a
habit of flexibility, that habit would stand it in good stead
in the midst of the changes wrought by hard times ; but
when it had, on the other hand, acquired rigidity (like the
proverbially " inflexible goose "), it would be at a disadvan-
tage in the stress of a heightened elimination.

The alternation of good times and hard times may be
illustrated by an example taken from human life. The
introduction of ostrich-farming in South Africa brought
good times to farmers. Whereupon there followed diver-
gence in two directions. Some devoted increased profits to
improvements upon their farms, to irrigation works which
could not before be afforded, and so forth. For others in-
creased income meant increased expenditure and an easier,

Variation and Natural Selection. 117

if not more luxurious, mode of life. Then came hard times.
Others, in Africa and elsewhere, learnt the secret of ostrich-
farming. Competition brought down profits, and elimina-
tion set in — of which variety need hardly be stated.

I believe that the alternation of good times and hard
times, during secular changes of climate and alternate ex-
pansions and contractions of life-areas through geological
upheavals and depression of the land, has been a factor of
the very greatest importance in the evolution of varied and
divergent forms of life, and in the elimination of inter-
mediate forms between adaptive variations. It now only
remains in this chapter to say a few words concerning con-
vergence, adaptation, and progress.

Convergence, which is the converse of divergence, is
brought about through the adaptation of different forms
of life to similar conditions of existence. The somewhat
similar form of the body and fin-like limbs of fishes, of
ancient reptiles (the ichthyosaurus and its allies), of whales,
seals, and manatees, is a case in point. Both birds, bats,
and pterodactyls have keeled breastbones for the attach-
ment of the large muscles for flight. A whole series of
analogous adaptations, as the result of analogous modes of
life, are found in the placental mammals of Europe and
Asia, on the one hand, and the marsupial forms of Australia
on the other hand. The flying squirrel answers to the
flying phalanger, the fox to the vulpine phalanger, the bear
to the koala, the badger to the pouched badger, the rabbit
to the bandicoot, the wolverine to the Tasmanian devil, the
weasel to the pouched weasel, the rats and mice to the
kangaroo rats and mice, and so on. A familiar example
of convergence is to be seen in our swallows and martins,
on the one hand, and the swifts on the other. Notwith-
standing their superficial similarity in external form and
habits, they are now generally regarded as belonging to
distinct orders of birds.

These are examples of convergence.* Animals of

* Two more teshnical examples may be noticed in a note. (1) Professor
Haeckel has recently (Challenger Keports, vol. xxviii.) shown that the

n8 Animal Life and Intelligence.

diverse descent and ancestry have, through similarity of
surrounding conditions or of habits of life, become, in
certain respects, assimilated. But some zoologists go
further than this. They maintain that the same genus
or species may, through adaptation to similar circum-
-stances, be derived from dissimilar ancestors. Some
palaeontologists, for example, believe that the horse has
been independently evolved along parallel lines in Europe
and in America. Professor Cope considers that in the one
continent Protohippus, and in the other Hipparion, was the
immediate ancestor of Equus. The probabilities are, how-
ever, so strongly against such a view, that it cannot be
accepted until substantiated by stronger evidence than is
yet forthcoming.

A special and particular form of convergence, at any
rate in certain obvious, if superficial, characters, has already
been noticed in our brief consideration of mimicry. In
the first place, among a number of closely related species
of inedible butterflies, the tendency to divergence is checked,
so far as external markings and coloration are concerned,
that all may continue to profit by the resemblance, and
that the numbers tasted by young birds in gaining their
experience (for the avoidance seems to be at most incom-
pletely instinctive) may be divided amongst all the species,
thus lessening the loss to each. Secondly, there may be a
convergence of certain genera of distantly related inedible
groups (e.g. among the Heliconidae and the Danaidae), which
gain by being apparently one species, since the loss from
young birds is shared between them. And lastly, there is
the true mimicry of quite distinct families of butterflies,
not themselves inedible, but sheltering themselves under

Siphonophora include two groups, closely resembling each other, but of
different ancestry: (a) The Disconanthro, traceable to trachomedusoid
ancestors ; (6) the Siphonanthae, traceable to anthomedusoid ancestors like
Sarsia. (2) M. Paul Pelseneer has beeH led to the conclusion that the
pteropod molluscs also include two groups resembling each other, but of
different ancestry : (a) The Thecosomes, traceable to tornatellid ancestors ;
(fc) the Gymnosomes, traceable to aphysiid ancestors. In each case, the
ancestral sea-slug has been modified for a free-swimming life.

Variation and Natural Selection. 1 1 9

the guise and sharing the bad reputation of the mimicked
forms. Such forms of convergence are in special adaptation
to a very special environment.

We must remember that in all cases adaptation is a
matter of life and environment. And these, we may now
note, may be related in one or more of three ways. In
the first place, there is the adaptation of life to an un-
changing environment ; for example, the adaptation of all
forms of life to the fixed and unchanging properties of
inorganic matter. If we liken life to a statue and the
environment to a mould in which it is cast, we have in
this case a rigid mould and a plastic statue. Secondly,
the adaptation may be mutual, as, for example, when the
structures of insects and flowers are fitted each to the
other, or when the speed of hunters and hunted is steadily
increased through the elimination of the slow in either
group. Here the mould and statue are both somewhat
plastic, and yield to each other's influence. Thirdly, the
environment may be moulded to life. This, again, is only
relative, since life never wholly loses its plasticity. The
bird that builds a nest, the beaver that constructs a dam,
the insect that gives rise to a gall, — these, so far, mould
the environment to the needs of their existence. Man in
especial has the power, through his developed intelligence,
of manufacturing his own environment. Here the statue
is relatively rigid, and the mould plastic.

Progress may be defined as continuous adaptation. In
modern phrase, this is called evolution. The continuity
makes the difference between evolution and revolution.
Both are natural. Both occur in the organic, the social,
and the intellectual sphere. Evolution is the orderly
progress of the organism or group of organisms, by which
it becomes more and more in harmony with surrounding
conditions. If the conditions become more and more com-
plex, the organism will progress in complexity ; but if the
conditions be more and more simple, progress (if such it
may still be called) will be towards simplicity of structure,
unnecessary complexity being eliminated, or, in any case,

I2O Animal Life and Intelligence.

disappearing. Hence, in parasites and some forms of life
which live under simple conditions, we have the phenomena
of degeneration, or a passage from a more complex to a
more simple condition.

Revolution in organic life is the destruction of one
organism or group of organisms, and the replacement in
its stead of a wholly different organism or group of
organisms. During hard times there may be much revo-
lution, or replacement of one set of organic forms by
another set of organic forms. It was by revolution that
the dominant reptiles of the Mesozoic epoch were replaced
by the dominant mammals of Kainozoic times. It was by
revolution that pterodactyls were supplanted by birds.
Revolution has exterminated many a group in geological
ages. On the other hand, it was by evolution that the
little-specialized Eocene ungulates gave rise to the horse,
the camel, and the deer ; by divergent evolution that the
bears and dogs were derived from common ancestors.
Palaeontology testifies both to evolution and revolution.*
That history does the same, I need not stay to exemplify.
The same laws also apply to systems of thought. Dar-
winism has revolutionized our conceptions of nature.
Darwin placed upon a satisfactory basis a new order of
interpretation of the organic world. By it other interpre-
tations have been supplanted. And now this new concep-
tion is undergoing evolution, not without some divergence.

In this chapter we have seen how evolution is possible
under natural conditions. If the law of increase be true,
if more are born than can survive to procreate their kind,
natural selection is a logical necessity. We must not
blame our forefathers for not seeing this. Until geology
had extended our conception of time, no such conclusions
could be drawn. If organisms have existed but six or
seven thousand years, and if in the last thousand years
little or no change in organic life has occurred, the
supposition that they could have originated by any such

* For evidence in copious abundance, see Nicholson's "Manual of
Palaeontology," new edition, vol. i. : " Vertebrata," by K. Lydekker.

Variation and Natural Selection. 121

process as natural selection is manifestly absurd. Lyell
was the necessary precursor of Darwin. Given, then,
increase and elimination throughout geological time,
natural selection is a logical necessity. No one who
adequately grasps the facts can now deny it. It is an
unquestionable factor in organic evolution. Whether it is
the sole factor, is quite another matter, and one we will /
consider in the chapter on " Organic Evolution."

122 Animal Life and Intelligence.

CHAPTER V.

HEREDITY AND THE ORIGIN OF VARIATIONS.

THE law of heredity, I have said above, may be regarded
as that of persistence exemplified in a series of organic
generations. Variation results — it is clear that it must
result — from some kind of differentiating influence. Such
statements as these, however, though they are true enough,
do not help us much in understanding either heredity or
variation.

Let us first notice that normal cases of reproduction
exemplify both phenomena — heredity with variation;
hereditary similarity to the parents in all essential respects,
individual variations in minor points. This is seen in
man. Brothers and sisters may present family resem-
blances among each other and to their parents, but each
has individual traits of feature and of character. Only in
particular cases of so-called "identical twins" are the
variations so slight as not to be readily perceptible by even
a casual observer.

Now, when we seek an explanation of these well-known
facts, we may be tempted to find it in the supposition that
the character of the parents does not remain constant, that
the character influences the offspring, and that therefore
the children born at successive periods will differ from each
other, while twins born in the same hour will naturally
resemble each other. As Darwin himself says,* " The
greater dissimilarity of the successive children of the same
family in comparison with twins, which often resemble
each other in external appearance, mental disposition, and

* " Animals and Plants under Domestication," vol ii. p. 239.

Heredity and the Origin of Variations. 1 2 3

constitution, in so extraordinary a manner, apparently
proves that the state of the parents at the exact period of
conception, or the nature of the subsequent embryonic
development, has a direct and powerful influence on the
character of the offspring." But a little consideration will
show that, though this might, in the absence of a better
explanation, account for variation in character, it could not
account for variation in form and feature, unless we regard
these as in some way determined by the character. More-
over, as we shall see presently, it is open to question
whether acquired modifications of structure or character in
the parent can in any way influence the offspring. Again,
in the litter of puppies born of the same bitch by the same
dog there are individual variations, often as well marked
as those in successive births.

The facts, then, to be accounted for are — first, the close
hereditary resemblance in all essential points of offspring
to parent; and, secondly, the individual differences in
minor points among the offspring produced simultaneously
or successively by the same parents. These are the facts
as they occur in the higher animals. It will be well to
lead up to our consideration of them by a preliminary
survey of the facts as they are exemplified by some of the
lower organisms.

In the simpler protozoa, where fission occurs, and where
the organism is composed of a single cell, where also there
is a single nucleus which apparently undergoes division
into two equal and similar parts, it is easy to understand
that the two organisms thus resulting from the halving of
a single organism partake completely of its nature. If the
fission of an amoeba is such as to divide it into two similar
parts, there is no reason why these two similar parts
should not be in all respects alike, and should not, by the
assimilation of new material, acquire the size and all the
characteristics of the parent form. In the higher and
more differentiated protozoa, the case is not quite so simple;
for the two halves are not each like the whole parent, but
have to be remodelled into a similar organism. But if we

124 Animal Life and Intelligence.

suppose, as we seem to hare every right to suppose, that
it is the nucleus that controls the formative processes in
the cell, there is not much difficulty in understanding how,
when the nucleus divides into two similar portions, each
directs, so to speak, the similar refashioning of its own
separated protoplasmic territory.

From the protozoa we may pass to such a comparatively
simple metazoon as the hydra. Here the organism is com-
posed, not of a single cell, but of a number of ce'lls. These
cells are, moreover, not all alike, but have undergone
differentiation with physiological division of labour. There
is an inner layer of large nutritive cells, and an outer layer
of protective cells, some of which are conical with fine pro-
cesses proceeding from the point of the cone ; others are
smaller, and fill in the interstices between the apices of the
cones, while others have developed into thread-cells, each
with a fine stinging filament. Between the two layers
there is a thin supporting lamella. The essential point we
have here to notice is that there are two distinct layers
with cells of different form and function.

Now, it has again and again been experimentally proved
that if a hydra be divided into a number of fragments, each
will grow up into a complete and perfect hydra. All that
is essential is that, in the separated fragment, there shall
be samples of the cells of both layers. Under these con-
ditions, the separated cells of the outer layer regenerate a
complete external wall, and the separated cells of the inner
layer similarly regenerate a complete internal lining. From
these facts, it would appear that such a small adequately
sampled fragment has the power, when isolated, of
assimilating nutriment and growing by the multiplication
of the constituent cells, and that the growth takes such
lines that the original form of the hydra is reproduced.

Here we may note, by way of analogy, what takes place
in the case of inorganic crystals. If a fragment of an
alum crystal be suspended in a strong solution of alum,
the crystal will be recompleted by the growth of new parts
along the broken edges. We say that this is effected under

Heredity and the Origin of Variations. 125

the influence of molecular polarity. Similarly, we may
say that the fragment of the hydra rebuilds the complete
form under the influence of an hereditary morphological
tendency residing in the nuclei of the several cells. The
case, though still comparatively simple, is more complex
than that of the higher protozoa. There the divided nucleus
in two separated cells directs each of these in hereditary
lines of morphological growth. Here not only do the cells
and their nuclei divide, but they are animated by a common
morphological principle, and in their multiplication combine
to form an organism possessing the ancestral symmetry.
If, however, we call this an hereditary morphological
tendency or a principle of symmetry; or, with the older
physiologists, a nisus formativus ; or, with Darwin, " the
co-ordinating power of the organization " (all of these
expressions being somewhat unsatisfactory) ; — we must
remember that these terms merely imply a play of molecular
forces analogous to that which causes the broken crystal
of alum to become recompleted in suitable solution. The
inherent molecular processes in the nuclei * in the one
case enable the cells to regenerate the hydra ; the inherent
molecular stresses in the crystalline fragment in the other
case lead to the reproduction of the complete crystal.
In either case there is no true explanation, but merely a
restatement of the facts under a convenient name or phrase.
The power of regeneration of lost parts, which is thus
seen in the hydra, is also seen, in a less degree so far as
amount is concerned, but in a higher degree so far as com-
plexity goes, in animals far above the hydra in the scale of
life. The lobster that has lost a claw, the snail whose
tentacle has been removed, the newt which has been docked
of a portion of its tail or a limb, are able more or less com-
pletely to regenerate these lost parts. And the regeneration
may involve complex structures. With the tentacle of the
snail the eye may be removed, and this, not once only, but

* Or in certain " physiological units " (Herbert Spencer), or " plastidules "
(Haeckel), which may be regarded as organic molecules exhibiting their
special properties under vital conditions.

126 Animal Life and Intelligence.

a dozen times. After such mutilation, no part of the eye
remains, though the stump of its nerve is, of course, left ;
still the perfect organ is reconstructed again and again, as
often as the tentacle is removed. The cells at the cut end
of the nerve-stump divide and multiply, as do also those of
the surrounding tissues, and the growing nerve terminates
in an optic cup, as it did previously under the influences of
normal development before the mutilation. Here we have
phenomena analogous to, and in some respects more com-
plex than, those which are seen in the regenerative process
in hydra. It is well known, however, that, in the case of
higher animals, in birds and mammals, this power of
regenerating lost parts does not exist. When a bone is
broken, osseous union of the broken pieces may indeed take
place ; and in flesh-wounds, the gash is filled in and heals
over, not without permanent signs of its existence, as may
often be seen in the faces of German students. But beyond
this there is normally no regeneration. The soldier who
has lost an arm in battle cannot return home and in quiet
seclusion reproduce a new limb. That which seems to be
among lower animals a well-established law of organic
growth does not here obtain. This is probably due to the
fact that the higher histological differentiation of the tissues
in the more highly developed forms of life is a bar to
regeneration. In their devotion to special and minute
details of physiological work, the cells have, so to speak,
forgotten their more generalized reproductive faculties.
In any case, however the fact is to be explained, the
higher organisms have in many cases almost completely
lost the power of regenerating lost parts. But this loss of
the regenerative power in the more highly differentiated
animals does not alter or invalidate the law of organic
growth we are considering. The law may be thus stated :
Whenever, after mutilation, free growth of the mutilated surface
occurs, that growth is directed in such lines as to reproduce
the lost part and restore the symmetrical integrity of the
organism. This is a matter of heredity. And we may
regard the hereditary reconstructive power as residing

Heredity and the Origin of Variations. 127

either (1) in those cells at or adjoining the mutilated
surface which are concerned in the regrowth of the lost
part ; or (2) in the general mass of cells of the mutilated
organism.

There are difficulties in either view. Professor Sollas,
supporting the former, says,* " This power [in the snail]
of growing afresh so complex and specialized an organ as
an eye is certainly, at first sight, not a little astonishing,
but it appears to be capable of a very simple explanation.
The cells terminating the cut stump of the tentacle are the
ancestors of those which are removed; a fresh series of
descendants are derived from them, similarly related to the
ancestral cells as their predecessors which they replace ;
the first generation of descendants become in turn ancestors
to a second generation, similarly related to them as were
the second tier of extirpated cells ; and this process of
descent being repeated, the completed organ will at length
be rebuilt." This explanation is, however, misleading in
its simplicity. The cells terminating the cut stump are
not the direct ancestors of those which are removed, except
in the same sense as gorillas are ancestors of men. They
are rather collateral descendants of common ancestors. I
think that Professor Sollas would probably agree that,
though the lens and " retina " are of epiblastic (outer
layer) origin, their relationship with the epiblastic cells at
the cut stump is a somewhat distant one. In the repro-
duction of the lens the cell-heredity is not direct, but
markedly indirect. And it is somewhat difficult to under-
stand by what means the ordinary epiblastic cells of the
cut stump, which have had no part in the special and
peculiar work of lens-production, should be enabled to
produce cell-offspring, some of which, and those in a
special relation to other deeper-lying cells, possess this
peculiar power.

On the other hand, if we turn to the view that the
reproduction is effected, not by the cells of the cut surface
alone, but by the general mass of cells in the mutilated

* Nature, vol. xxxix. p. 486.

128 Animal Life and Intelligence.

organism, we have to face the difficulty of understanding
how the influence of cells other than those partaking in
the regrowth can be brought to bear on these so as to
direct their lines of development. If we say that the
organism is pervaded by a principle of symmetry such
that both growth and regrowth, whenever they take place,
are constrained to follow the lines of ancestral symmetry,
we are really doing little more than restating the facts
without affording any real organic explanation. That
which we want to know is in what organic way this sym-
metrical growth is effected — how the hereditary tendency is
transmitted through the nuclear network which is concerned
in cell-division. I do not think that we are at present in
a position to give a satisfactory answer to this question.

Let us now return to the hydra, the artificial fission of
which has suggested these considerations. Multiplication
in this way is probably abnormal. Under suitable con-
ditions, however, if well fed, the hydra normally multiplies
by budding. At some spot, generally not far from the
" foot," or base of attachment, a little swelling occurs, and
the growth of the cells in this region takes such lines that
a new hydra is formed. This is at first in direct con-
nection with the parent stem, the two having a common
internal cavity ; but eventually it separates and lives a free
existence as a distinct organism (see Fig. 9, p. 45).

Now, here we may notice, as an implication from these
facts, that the size of the organism is limited. When the
normal limits of size are reached, any further assimilation
of nutriment ministers, not to the further growth of the
organism, but to the formation of a new outgrowth, or
bud. What determines that the outgrowth, or bud, should
originate in this or that group of cells, we do not know.
But, like the isolated fragment in the hydra subdivided
by fission, the little group in which budding commences
contains a fair sample of the various kinds of cells which
constitute the hydra. And here, too, we see that their
growth and development follow definite lines of hereditary
symmetry.

Heredity and the Origin of Variations. 129

But there is a third method of multiplication in hydra :
this is the sexual mode of reproduction, and occurs
generally in the autumn. On the body-wall of certain
individuals, near the tentacles, conical swellings appear.
Within these swellings are great numbers of minute sperms,
with small oval heads and active, thread-like tails. They
appear to originate from the interstitial cells of the outer
layer (see p. 124). Nearer the foot, or base of attachment,
and generally, but not quite always, in separate individuals,
there are other larger swellings, different in appearapce,
of which there is generally only one in the same individual
at the same time. Each contains a single ovum, or egg-
cell, surrounded by a capsule. It, too, and the cells which
surround it would appear to be developed from the inter-
stitial cells. It grows rapidly at the expense of the sur-
rounding tissue, but when mature, it bursts through the
enveloping capsule, and is freely exposed. A sperm-cell,
which seems, in some cases at least, to be produced by the
same individual, now unites with it ; the egg-cell then
begins to undergo division, becomes detached, falls to the
bottom, and develops into a young hydra.

Here, then, we have that sexual mode of reproduction
which occurs in all the higher animals. It is, however, in
some respects peculiar in hydra. In the first place, the
ovum is nearly always in other animals (but occasionally
not in hydra) fertilized by the sperm from a separate and
distinct individual. In the second place, the germinal cells
are generally produced, not from the outer layer, but from
the middle layer, which appears between the two primitive
layers. In some allies of hydra, however, they take their
origin in the inner layer ; and it has been suggested that,
even in hydra, the true germinal cells may migrate from
the inner to the outer layer. But of this there does not
seem to be at present sufficient evidence. In any case,
however, the essential fact to bear in mind is that a new
individual is produced by the union of a single cell pro-
duced by one organism and of another cell produced in
most cases (but not always in the hydra) from a different

K

130 Animal Life and Intelligence.

individual. In the higher forms of animal life, the organisms
are either female (egg-producing) or male (sperm-pro-
ducing). But there are many hermaphrodite forms which
produce both eggs and sperms, as in the common snail and
earthworm. Even in these cases, however, there are
generally special arrangements by which it is ensured that
the sperm from one individual should fertilize the ovum
produced by another individual.

What, we must next inquire, is the relation in the higher
forms of life — for we may now leave the special considera-
tion of hydra — of the ovum or sperm to the organism which
produces it ? This is but one mode of putting a very old
question — Does the hen produce the egg, or does the egg
produce the hen ? Of course, in a sense, both are true ;
for the hen produces an egg which, if duly fertilized, will
develop into a new hen. But the question has of late been
asked in a new sense ; and many eminent naturalists reply,
without hesitation — The egg produces the hen, but under
no circumstances does the hen produce the egg. What,
then, it may be asked, does produce the egg ? To this it
is replied — The egg was produced by a previous egg. At
first sight, this may seem a mere quibble ; for it may be
said that, of course, if an egg produces a hen which contains
other eggs, these eggs may be said to be produced by the
first. But it is really more than a quibble, and we must do
our best clearly to grasp what is meant.

We have seen that, in development, the fertilized egg-
cell undergoes division into two cells, each of which again
divides into two, and so on, again and again, until from
one there arises a multitude of cells. Nor is this all. The
multitude are organized into a whole. The constituent
cells have different forms and structures, and perform
diverse functions. Some are skeletal, such as bone and
connective tissue ; some are protective, such as those which
give rise to feathers or scales ; some form nerves or nerve-
centres ; some, muscles ; some give rise to glandular tissue ;
and lastly, some form the essential elements in reproduc-

Heredity and the Origin of Variations. 131

tion. If, now, we express the development of tissues and
the sequence of organisms in the following scheme, the
continuity of the reproductive cells will be apparent : —

^Skeletal and protective cells

Reproductive cell C^^ SM^ cells
> cells

Reproductive

It is clear that there is a continuity of reproductive
cells, which does not obtain with regard to nerve, gland, or
skeleton. If, then, we class together as body-cells those
tissue-elements which constitute what we ordinarily call
the body, i.e. the head, trunk, limbs — all, in fact, except the
reproductive cells, our scheme becomes —

Reproductive ceUO—^ductive cells O^froductive cells O— £

From this, again, it is clear that the body does not pro-
duce the egg, or reproductive cell, but that the reproductive
cell does produce the body. Of course, it should be noted
that we are here using the term " body " as distinguished
from, and not as including, the reproductive cells. But this
is convenient, in that it emphasizes the fact that the mus-
cular, nervous, skeletal, and glandular cells take (on this
view) no part whatever in producing those reproductive
cells which are concerned in the continuance of the species.

Such, in brief, is the view that the egg produces the
hen. We will return to it presently when we have glanced
at the alternative view that the hen produces the egg.

On this view, the reproductive elements are. not merely
cells, the result of normal cell-division, which have been
set aside for the continuance of the species. They are, so
to speak, the concentrated extract of the body, and con-
tain minute or infinitesimal elements derived from all the
different tissues of the organism which produces them.
Darwin * suggested that all the cells of the various tissues
produce minute particles called gemmules, which circulate

* Darwin, " Animals and Plants under Domestication," 2nd edit., vol. ii.
chap, xxvii., from which the following description and quotations are taken.

132 Animal Life and Intelligence.

freely throughout the body, but eventually find a home in
the reproductive cells. Just as the organism produces an
ovum from which an organism like itself develops, so do
the cells of the organism produce gernmules, which find
their way to the ovum and become the germs of similar
cells in the developing embryo. " The child, strictly
speaking," says Darwin, " does not grow into a man, but
includes germs which slowly and successively become
developed and form the man." "Each animal may be
compared with a bed of soil full of seeds, some of which
soon germinate, some lie dormant for a period, whilst
others perish." Or, to vary the analogy, "an organic
being is a microcosm — a little universe formed of a host
of self-propagating organisms." This is Darwin's pro-
visional hypothesis of pangenesis, which has recently been
accepted in a modified form by Professor W. K. Brooks in
America, to some extent by De Vries on the Continent, by
Professor Herdman of Liverpool, and by other biologists.
The ovum on this view is to be regarded as a composite
germ containing the germs of the cellular constituents of
the future organism. The scheme representing this view
will stand thus —

Skeletal and protective cells ^_ ^. »k. and pr. ^^ ^ 8.

Reproductive cell O Nerve and muscle fells "^^O n- an^ m- ^^O ' — n-

^~-_Glandular and nutritive cells ^"^ ^ gl. and nu. '•"" ~^-~- gl.

It is clear that, on this hypothesis, we may frame an
apparently simple and, on first sight, satisfactory theory of
heredity. Since all the . body-cells produce gemmules,
which collect in or give rise to the reproductive cells, and
since each gemmule is the germ of a similar cell, what can
be more natural than that the ovum, thus composed of
representative cell-germs, should develop into an organism
resembling the parent organism ? Modifications of structure
acquired during the life of the organism would thus be
transmitted from parent to offspring ; for the modified cells
of the parent would give rise to modified gemmules, which
would thus hand on the modification. The inheritance of
ancestral traits from grandparent or great-grandparent
might be accounted for by supposing that some of the

Heredity and the Origin of Variations. 133

gemmules remained latent to develop in the second or
third generation. The regeneration of lost parts receives
also a ready explanation. If a part be removed by ampu-
tation, regrowth is possible because there are disseminated
throughout the body gemmules derived from each part and
from every organ. A stock of nascent cells or of partially
developed gemmules may even be retained for this special
purpose, either locally or throughout the body, ready to
combine with the gemmules derived from the cells which
come next in due succession. Similarly, in budding, the
buds may contain nascent cells or gemmules in a some-
what advanced stage of development, thus obviating the
necessity of going through all the early stages in the
genesis of tissues. The gemmules derived from each part
being, moreover, thoroughly dispersed through the system,
a little fragment of such an organism as hydra may con-
tain sufficient to rebuild the complete organism ; or, if it
contains an insufficient number, we may assume that the
gemmules, in their undeveloped state, are capable of multi-
plying indefinitely by self-division. Finally, variations
might arise from the superabundance of certain gemmules
and the deficiency of others, and from the varying potency
of the gemmules contained in the sperm and ovum. Where
the maternal and paternal gemmules are of equal potency,
the cell resulting from their union will be a true mean
between them ; where one or other is prepotent, the result-
ing cell will tend in a corresponding direction. And since
the parental cells are subject to modification, transmitted
through the gemmules to the reproductive elements, it is
clear that there is abundant room and opportunity for
varietal combinations.

It is claimed, as one of the chief advantages of some
form of pangenetic hypothesis, that it, and it alone, enables
us to explain the inheritance of characters or modifications
of structure acquired by use (or lost by disuse) during the
life of the organism, or imprinted on the tissues by en-
vironmental stresses. The evidence for the transmission
of such acquired characters we shall have to consider

134 Animal Life and Intelligence.

hereafter. We may here notice, however, that at first
sight the hypothesis seems to prove too little or too much.
For while modifications of tissues, the effects of use and
disuse, are said to be inherited, the total removal of tissues
by amputation, even if repeated generation after generation,
as in the docking of the tails of dogs and horses, formerly
so common, does not have the effect of producing offspring
similarly modified. Professor Weismann has recently
amputated the tails of white mice so soon as they were
born, for a number of generations, but there is no curtail-
ment of this organ in the mice born of parents who had
not only themselves suffered in this way, but whose
parents, grandparents, and great-grandparents were all
rendered tailless. The pangenetic answer to this objection
is that gemmules multiply and are transmitted during
long series of generations. We have only to suppose that
the gemmules of distantly ancestral tails have been passing
through the mutilated mice in a dormant condition, await-
ing an opportunity to develop, and the constant reappear-
ance of tails is seen to be no real anomaly. In this case
the gemmules of the parental and grandparental tail are
simply absent. But if the muscles of the parental tail
were modified through unwonted use, the modified cells
would give rise to modified gemmules, which would unite
in generation with ancestral gemmules, and to a greater
or less degree modify them. The difference is between the
mere absence of gemmules and the presence of modified
gemmules. And the fact that it takes some generations
for the effects of use or disuse to become marked is
(pangenetically) due to the fact that it takes some time for
the modified gemmules to accumulate and be transmitted
in sufficient numbers to affect seriously the numerous
ancestral gemmules.

The direction in which Professor W. K. Brooks has
recently sought to modify Darwin's pangenetic hypothesis
may here be briefly indicated. He holds that it is under
unwonted and abnormal conditions that the cells are
stimulated to produce gemmules, and that the sperm is

Heredity and the Origin of Variations. 135

the special centre of their accumulation. ' Hence it is the
paternal influence which makes for variation, the maternal
tendency being conservative. The reproductive cell is not
merely or chiefly a microcosm of gemmules. It is a cell
produced by ordinary cell- division from other reproductive
cells. The ovum remains comparatively unaffected by
changes in the body ; but it receives from the sperm, with
which it unites, gemmules from such tissues in the male
as were undergoing special modification. The hen does
not produce the egg; but the cock does produce the sperm ;
and the union of the two hits the happy mean between the
conservatism of the one view and the progressive possi-
bilities of the other.

Mr. Francis Galton, in 1876,* suggested a modification
of Darwin's hypothesis, which included, as does that of
Professor Brooks, the idea of germinal continuity which
had been suggested by Professor (now Sir Kichard) Owen,
in 1849. He calls the collection of gemmules in the
fertilized ovum the " stirp." Of the gemmules which con-
stitute the stirp only a certain number, and they the most
dominant, develop into the body-cells of the embryo. The
rest are retained unaltered to form the germinal cells and
keep up a continuous tradition. Mr. Galton's place in the
history of theories of heredity can scarcely be placed too
high. Only one further modification of pangenesis can
here be mentioned, namely, that proposed in 1883 by
Professor Herdman, of Liverpool. He suggested " that the
body of the individual is formed, not by the development
of gemmules alone and independently into cells, but by the
gemmules in the cells causing, by their affinities and
repulsions, these cells so to divide as to give rise to new
cells, tissues, and organs."

Such are Darwin's provisional hypothesis of pangenesis,
and some more recent modifications thereof. Bold and
ingenious as was Darwin's speculation, supported as it at

* For an excellent account of the genesis and growth of the modern views
of heredity, see Mr. J. Arthur Thomson's paper on "The History and Theory
of Heredity : " Proceedings of the Royal Society of Edinburgh, 1889.

136 Animal Life and Intelligence.

first sight seems to be by organic analogies, it finds to-day
but few adherents. With all our increased modern micro-
scopical appliances, no one has ever seen the production
of gemmules. Although it appears sufficiently logical to
say that, just as a large organism produces a small ovum,
so does each small cell produce an exceedingly minute
gemmule ; when closely investigated, the analogy is not
altogether satisfactory. It is denied, as we have seen, by
many biologists that the organism does produce the ovum.
Multiplication is normally by definite, visible cell-division.
Nuclear fission can be followed in all its phases. But
where is the nuclear fission in the formation of gemmules ?
It is true that the conjugation of monads is followed by
the pouring forth of a fluid which must be crowded with
germs from which new monads arise, and that these germs
are so minute as to be invisible, even under high powers
of the microscope. It might be suggested, then, that in
every tissue some typical cell or cells might thus break up
into a multitude of invisible gemmules. But there is at
present no evidence that they do so. And even if this were
the case, it would not bear out Darwin's view, that every
cell is constantly throwing off numerous gemmules. It is
known, however, or at least generally believed, that there
is a constant replacement of tissues during the life of the
organism. It is said, for example, that in the course of
seven years the whole cellular substance of the human
body is entirely renewed. The fact is, I think, open to
question. Granting it, however, it might be suggested
that the effete cells, ere they vanish, give rise to minute
gemmules, which find their way to the ova. But it must
be remembered that the new tissue-cells in the supposed
successional renewal of the organs are the descendants of
the old tissue-cells ; that these are, therefore, already
reproducing their kind directly ; and that the formation of
gemmules would thus be a special superadded provision
for a future generation. Still, there is no reason why cells
should not have this double mode of reproduction, if any
definite evidence of its existence could be brought forward.

Heredity and the Origin of Variations. 137

Without such definite evidence, we may well hesitate before
we accept it even provisionally.

The existence of gemmules, then, is unproven, and their
supposed mode of origin not in altogether satisfactory
accordance with organic analogies. Furthermore, the
whole machinery of the scheme of heredity is complicated
and hyper-hypothetical. It is difficult to read Darwin's
account of reversion, the inheritance of functionally
acquired characters, and the non-inheritance of mutilation,
or to follow his skilful manipulation of the invisible army
of gemmules, without being tempted to exclaim — What
cannot be explained, if this be explanation ? and to ask
whether an honest confession of ignorance, of which we
are all so terribly afraid, be not, after all, a more satis-
factory position.

That the hen produces the egg, that "gemmules are
collected from all parts of the system to constitute the
sexual elements, and that their development in the next
generation forms a new being," is further rendered im-
probable by direct observation upon the mode of origin of
the germinal cells, ova, or sperms.

It will be remembered that the view that the egg
produces the hen, while the hen does not produce the egg,
suggested the question — What, then, does produce the
egg? to which the answer was — The egg is the product
of a previous egg. On this view, then, the germinal cells,
ova, or sperms are the direct and unmodified descendants
of an ovum and sperm which have entered into fertile
union. Now, in certain cases, notably in the fly Chironomus,
studied by Professor Balbiani, but also in a less degree
in some other invertebrate forms, it is possible to trace the
continuity of the germinal cells with the fertilized ovum
from which they are derived. In Chironomus, for example,
" at a very early stage in the embryo, the future reproduc-
tive cells are distinguishable and separable from the body-
forming cells. The latter develop in manifold variety, into
skin and nerve, muscle and blood, gut and gland; they
differentiate, and lose almost all protoplasmic likeness to

138 Animal Life and Intelligence.

the mother ovum. But the reproductive cells are set apart ;
they take no share in the differentiation, but remain
virtually unchanged, and continue unaltered the proto-
plasmic tradition of the original ovum."* In such a case,
then, observation flatly negatives the view that the germinal
cells are "constituted" by gemmules collected from the
body-cells, though, of course (on a modified pangenetic
hypothesis), they might be the recipients of such gemmules.

It is only in a minority of cases, however, that the direct
continuity of germinal cells as such is actually demonstrable.
In the higher vertebrates, for instance, the future repro-
ductive cells can first be recognized only after differentiation
of some of the body-cells and the tissues they constitute
is relatively advanced. While in cases of alternation of
generations, " an entire asexual generation, or more than
one, may intervene between one ovum and another." In
all such cases the continuity of the chain of recognizably
germinal cells cannot be actually demonstrated.

The impracticability of actually demonstrating a con-
tinuity of germinal cells in the majority of cases has
induced Professor Weismann to abandon the view that
there is a continuity of germinal cells, and to substitute
for it the view that there is a continuity of germ-plasm
(keimplasma) . "A continuity of germ-cells," he says,t
"does not now take place, except in very rare instances;
but this fact does not prevent us from adopting a theory of
the continuity of the germ-plasm, in favour of which much
weighty evidence can be brought forward." It might,
however, be suggested that, although a continuity of
germ-cells cannot be demonstrated, such continuity may,
nevertheless, obtain, the future germinal cells remaining
undifferentiated, while the cells around them are under-
going differentiation. The comparatively slight differentia-
tion of the body-cells in hydroids renders such a view by
no means improbable. But Professor Weismann does not
regard such an idea as admissible, at all events, in certain

* Geddea and Thomson, "The Evolution of Sex," p. 92.

t Weisuiann, " Essays on Heredity," English translation, p. 173.

Heredity and the Origin of Variations. 1 39

cases. "It is quite impossible," he says,* "to maintain
that the germ-cells of hydroids, or of the higher plants,
exist from the time of embryonic development, as undif-
ferentiated cells, which cannot be distinguished from
others, and which are only differentiated at a later period."
The number of daughter-cells in a colony of hydroid
zoophytes is so great that "all the cells of the embryo
must for a long time act as body-cells, and nothing else."
Moreover, actual observation (e.g. in Coryne) convinces Dr.
Weismann that ordinary body-cells are converted into
reproductive cells. After describing the parts of the body-
wall in which a sexual bud arises as in no way different
from surrounding areas, he says, "Bapid growth, then,
takes place at a single spot, and some of the young cells
thus produced are transformed into germ-cells which did not
previously exist as separate cells. "f

This transformation of body-cells or their daughter-
cells into germ-cells seems therefore, if it be admitted, to
negative the continuity of germ-cells as such. But this
fact, says Weismann, does not prevent us from adopting a
theory of the continuity of germ-plasm. "As a result of
my investigations on. hydroids," he says,J "I concluded
that the germ-plasm is present in a very finely divided
and therefore invisible state in certain body-cells, from
the very beginning of embryonic development, and that it
is then transmitted, through innumerable cell-generations,
to those remote individuals of the colony in which the
sexual products are formed."

This_germ-pla^m_ resides in the nucleus of the cell;
and it would seem that by a little skilful manipulation it

* Weismann, " Essays on Heredity," p. 205.

t A few pages earlier (p. 200) in the same essay, Professor Weismann
says, "A sudden transformation of the nucleo-plasm of a somatic cell into
that of a germ-cell would be almost as incredible as the transformation of a
mammal into an amoeba." This at first sight does not seem quite consistent
with the subsequent sentence which I have quoted in the text; for here, at
any rate, the daughters of " mammals " are said to be converted into " amoebae."
But this is no doubt because the amoebse (germ-plasms) are contained in the
mammals (body-cells). (See the quotations that follow in the text.)

J Weismann, " Essays on Heredity," p. 207.

I4O Animal Life and Intelligence.

can be made to account for anything that has ever been
observed or is ever likely to be observed. It is one of
those convenient invisibles that will do anything you
desire. The regrowth of a limb shows that the cells con-
tained some of the original germ- plasm. A little sampled
fragment of hydra has it in abundance. It lurks in the
body- wall of the budding polype. It is ever ready at call.
It conveniently accounts for atavism, or reversion; for*
" the germ-plasm of very remote ancestors can occasionally
make itself felt. Even a very minute trace of a specific
germ-plasm possesses the definite tendency to build up a
certain organism, and will develop this tendency as soon
as the nutrition is, for some reason, favoured above that of
the other kinds of germ-plasm present in the nucleus."

In place, then, of the direct continuity of germ-cells as
distinct from body-cells, we have here the direct continuity
of germ-plasm as opposed to body-plasm. The germ-plasm
can give rise to body-plasm to any extent ; the body-plasm
can never give rise to germ-plasm. If it seems to do so,
this is only because the nuclei of the body-cells contain
some germ-plasm in an invisible form. The body-plasm
dies ; but the life of the germ-plasm is, under appropriate
conditions, indefinitely continuous.

So far as heredity is concerned, it matters not whether
there be a continuity of germ-cells or of germ-plasma. In
either case, the essential feature is that body-cells as such
cannot give rise to the germ — that the hen cannot produce
the egg. On either view, characters acquired by the body
cannot be transmitted to the offspring through the ova or
sperms. The annexed diagram illustrates how, on the
view that the hen produces the egg, dints hammered into
the body by the environment will be handed on ; while, on
the view that the hen does not produce the egg, the dints
of the environment are not transmitted to the offspring.
On the hypothesis of continuity, heredity is due to the fact
that two similar things under similar conditions will give
similar products. The ovum from which the mother is
* Weismann, " Essays on Heredity," p. 179.

Heredity and the Origin of Variations. 141

developed, and the ovum from which the daughter is
developed, are simply two fragments separated at different
times from the same continuous germ-plasm.* Both
develop under similar circumstances, and their products
cannot, therefore, fail to be similar. How variation is
possible under these conditions we shall have to consider
presently.

Now, although I value highly Professor "Weismann's

n.

Fig. 21.— Egg and hen.

7. " The egg produces the hen." II. " The hen produces the egg." In /. the dints pro-
duced by the environment are not inherited ; in //. they are. The letters indicate successive
individuals. The small round circles indicate the eggs.

luminous researches, and read with interest his ingenious
speculations, I cannot but regard his doctrine of the con-
tinuity of germ-plasm as a distinctly retrograde step. His
germ-plasm is an unknowable, invisible, hypothetical entity.
Material though it be, it is of no more practical value than
a mysterious and mythical germinal principle. By a little
skilful manipulation, it may be made to account for any-

* It will, of course, be understood that a minute fragment of germ-plasm
is capable of almost unlimited growth by assimilation of nutritive material,
its properties remaining unchanged during such growth.

142 Animal Life and Intelligence.

thing and everything. The fundamental assumption that
whereas germ-plasm can give rise to body-plasm to any
extent, body-plasm can under no circumstances give rise to
germ-plasm, introduces an unnecessary mystery. Biological
science should set its face against such mysteries. The
fiction of two protoplasms, distinct and yet commingled,
is, in my opinion, little calculated to advance our know-
ledge and comprehension of organic processes. For myself,
I prefer to take my stand on protoplasmic unity and
cellular continuity. ^-a^T'

The hypothesis of cellular continuity is ^me that the
researches of embryologists tend more and more to justify.
The fertilized ovum divides and subdivides, and, by a con-
tinuance of such processes of subdivision, gives rise to all
the cells of which the adult organism is composed. It is
true that in some cases, as in that of peripatus, as inter-
preted by Mr. Adam Sedgwick, the cells of the embryo run
together or remain continuous as a diffused protoplasmic
mass with several or many nuclei. But this seemingly
occurs only in early stages as a step towards the separation
of distinct cells. And even if the process should be proved
of far wider occurrence, it would not disprove the essential
doctrine of cellular continuity. The nucleus is the essence
of the cell. And the doctrine of cellular continuity empha-
sizes the fact that the nuclei of all the cells of the body
are derived by a process of divisional growth from the first
segmentation-nucleus which results from the union of the
nuclei of the ovum and the sperm. In this sense, then,
however late the germinal cells appear as such, they are
in direct continuity with the germinal cell from which
they, in common with all the cells of the organism, derive
their origin. In this sense there is a true continuity of
germ- cells.

Now, it has again and again been pointed out that the
simple cell of which an amoeba is composed is able to per-
form, in simple fashion, the various protoplasmic functions.
It absorbs and assimilates food ; it is contractile and
responds to stimulation ; it respires and exhibits metabolic

Heredity and the Origin of Variations. 143

processes; it undergoes fission and is reproductive. The
metazoa are cell-aggregates ; and in them the cells
exemplify a physiological division of labour. They dif-
ferentiate, and give rise to muscle and nerve, gut and
gland, blood and connective or skeletal tissue, ova and
sperms. Are these germinal cells mysteriously different
from all the other cells which have undergone differentia-
tion ? No. They are the cells which have been differentiated
and set apart for the special work of reproduction, as others
have been differentiated and set apart for other protoplasmic
functions.

Cell-reproduction is, however, in the metazoa of tw<
kinds. There is the direct reproduction of differentiate
cells, by which muscle-cells, nerve-cells, or others reprodm
their kind in the growth of tissues or organs ; and there
is the developmental reproduction, by which the germinal
cells under appropriate conditions reproduce an organism }
similar to the parent. The former is in the direct line of\
descent from the simple reproduction of amceba. The
latter is something peculiarly metazoan, and is, if one
may be allowed the expression, specialized in its generality.

That the metazoa are derived from the protozoa is
generally believed. How they were developed is to a large
extent a matter of speculation. But, however originating,
their evolution involved the production, from cells of one
kind, of cells of two or more kinds, co-operating in the
same organism. Whenever and however this occurred, the
new phase of developmental reproduction must have had
its origin. And if in cell-division there is any continuity
of protoplasmic power, the faculty of producing diverse
co-operating cells would be transmitted. On any view of
the origin of the metazoa, this diverse or developmental
reproduction is a new protoplasmic faculty ; on any view,
it must have been transmitted, for otherwise the metazoa
would have ceased to exist. This new faculty of develop-
mental reproduction, then, with the inception of the metazoa,
takes its place among other protoplasmic faculties, and,
with the progress of differentiation and the division of

144 Animal Life and Intelligence.

labour, will become the special business of certain cells.
On this view, the specialization of the reproductive faculty
and of germinal cells takes its place in line with other cell-
differentiations with division of labour ; and the difficulties
of comprehending and following the process of differentia-
tion in this matter are similar to those which attend
physiological division of labour in general.

It is probable that, in the lower metazoa, in which
differentiation has not become excessively stereotyped, the
power of developmental reproduction is retained by a great
number of cells, even while it is being specialized in certain
cells. Hence the ability to produce lost parts and the
reproduction of hydra by fission. But, on the other hand,
the special differentiation of a tissue on particular lines
has always a tendency to disqualify the cells from perform-
ing other protoplasmic faculties, and that of developmental
reproduction among the number. I do not know of any
definite, well-observed cases on record in the animal kingdom
of ova or sperms being derived from cells which are highly
differentiated in any other respect. In the vertebrata, the
mesoblastic, or mid-layer, cells, from which the germinal
epithelium arises, have certainly not been previously
differentiated in any other line. And in the case of the
hydroid zoophytes, quoted by Professor Weismann, the
cells which give rise to the germinal products have never
been so highly differentiated as to lose the protoplasmic
faculty of developmental reproduction.

Some such view of developmental reproduction, based
upon cellular continuity and the division of labour, seems
to me more in accord with the general teachings of modern
biology than a hypothetical and arbitrary distinction
between a supposed germ-plasm and a supposed body-
plasm.

To which category, then, does this hypothesis belong ?
Does it support the view that the hen produces the egg or
that the egg produces the hen ? Undoubtedly the latter.
It is based on cellular continuity, and is summarized by the
scheme on p. 181. It adequately accounts for hereditary

Heredity and the Origin of Variations. 145

continuity, for there is a continuity of the germinal cells,
the bearers of heredity. But how, it may be asked, on
this view, or on any continuity hypothesis, are the origin
of variations and their transmission to be accounted for ?
To this question we have next to turn. But before doing
so, it will be well to recapitulate and summarize the positions
we have so far considered.

We saw at the outset that the facts we have to account
for are those of heredity with variation. To lead up to the
facts of sexual heredity, we considered fission, the regenera-
tion of lost parts, and budding in the lower animals. We
saw that, if a hydra be divided, each portion reproduces
appropriately the absent parts. But we found it difficult
to say whether this power resides, in such cases, in the
cells along the plane of section or in the general mass of
cells which constitute the regenerating portion.

Having led up to the sexual mode of reproduction, we
inquired whether the egg produces the hen or the hen pro-
duces the egg. We saw that there is a marked difference
between a direct continuity of reproductive cells, giving rise
to body-cells as by-products, and an indirect continuity of
reproductive cells, these cells giving rise to the hen, and
then the hen to fresh reproductive cells, which, on this
view, are to be regarded as concentrated essence of hen.

Darwin's hypothesis of pangenesis as exemplifying the
latter view was considered at some length, and the modi-
fications suggested by Professor Brooks, Mr. Galton, and
Professor Herdman were indicated. The hypothesis, so far
as it is regarded as a theory of the main facts of heredity,
was rejected.

It was then pointed out that only in a few cases has a
direct continuity of germinal cells as such been actually
demonstrated. Whence Professor Weismann has been led
to elaborate his doctrine of the continuity of germ-plasm.
This germ-plasm can give rise to, but cannot originate
from, body-plasm. It may lurk in body-cells, which may,
by its subsequent development, be transformed into germ-
cells. But any external influences which may affect these

L

146 Animal Life and Intelligence,

body-cells produce no change on the germ-plasm which they
may contain. We regarded this hypothesis as a retrograde
step, much as we admire the genius of its propounder, and
considered that the fiction of two protoplasms, distinct and
yet commingled, is little calculated to advance our com-
prehension of organic processes.

In the known and observed phenomena of cellular con-
tinuity and cell-differentiation, we found a sufficiently satis-
factory hypothesis of heredity. The reproductive cells
are the outcome of normal cell-division, and have been
differentiated and set apart for the special work of develop-
mental reproduction, as others have been differentiated
and set apart for other protoplasmic functions. Such a
view adequately accounts for hereditary continuity, for
there is a continuity of the germinal cells, the bearers of
heredity. But how, we repeat, on this view or any other
hypothesis of direct continuity, are the origin of variations
and their transmission to be accounted for ?

Every individual organism reacts more or less markedly
tinder the stress of environing conditions. The reaction
may take the form of passive resistance, or it may be
exemplified in the performance of specially directed motor-
activities. The power to react in these ways is inborn ;
but the degree to which the power is exercised depends
upon the conditions of existence, and during the life of the
individual the power may be increased or diminished accord-
ing to whether the conditions of life have led to its exercise
or not. The effects of training and exercise on the per-
formance of muscular feats and in the employment of mental
faculties are too well known to need special exemplification.
By manual labour the skin of the hand is thickened ; and
by long-continued handling of a rifle a bony growth caused
by the weapon in drilling, the so-called exercierknochen of
the Germans, is developed. Now, it is clear that if these
acquired structures or faculties are transmitted from
parent to offspring, we have here a most important source
and origin of variations — a source from which spring varia-

Heredity and the Origin of Variations. 147

tions just in the particular direction in which they are
wanted. The question is — Are they transmitted? and if
so, how ?

Let us begin with the protozoa. Dr. Dallinger made
some interesting experiments on monads. They extended
over seven years, and were directed towards ascertaining
whether these minute organisms could be gradually ac-
climatized to a temperature higher than that which is
normal to them. Commencing at 60° Fahr., the first
four months were occupied in raising the temperature
10° without altering the life-history. When the temperature
of 73° was reached, an adverse influence appeared to be
exerted on the vitality and productiveness of the organism.
The temperature being left constant for two months, they
regained their full vigour, and by gradual stages of increase
78° was reached in five months more. Again, a long pause
was necessary, and during the period of adaptation a
marked development of vacuoles, or internal watery spaces,
was noticed, on the disappearance of which it was possible
to raise the temperature higher. Thus by a series of
advances, with periods of rest between, a temperature of
158° Fahr. was reached. It was estimated that the re-
search extended over half a million generations. Here,
then, these monads became gradually acclimatized to a
temperature more than double that to which their ancestors
had been accustomed to — a temperature which brought
rapid death to their unmodified relatives.

Now, in such observations it is impossible to exclude
elimination. It is probable that there were numbers of
monads which were unable to accommodate themselves to
the changed conditions, and were therefore eliminated.
But in any case, the fact remains that the survivors had,
in half a million generations, acquired a power of existing
at a temperature to which no individual in its single life
could become acclimatized. Here, then, we have the
hereditary transmission of a faculty. But the organisms
experimented on were protozoa. In them there is no dis-
tinction between germ-cell and body-cell. Multiplication

148 Animal Life and Intelligence.

is by fission. And if the cell which undergoes fission has
been modified, the two separate cell-organisms which result
from that fission will retain the special modification. In
such cases the transmission of acquired characters is readily
comprehensible. We have an hereditary summation of
effects.

With the metazoa the case is different. In the higher
forms the germinal cells are internal and sheltered from
environing influences by the protecting body-wall. It is
the body-cells that react to environmental stresses; it is
muscle and nerve in which faculty is strengthened by use
and exercise, or allowed to dwindle through neglect. The
germ-cells are shielded from external influences. They
lead a sheltered and protected life within the body-cavity.
It is no part of their business to take part in either passive
resistance or responsive activity. During the individual
life, then, the body may be modified, may acquire new
tissue, may by exercise develop enhanced faculties. But
can the body so modified affect the germ-cells which it
carries within it ?

Biologists are divided on this question. Some say that
the body cannot affect the germ ; others believe that it can
and does do so.

It might seem an easy matter to settle one way or
another. But, in truth, it is by no means so easy. Suppose
that a man by strenuous exercise brings certain muscles to
a high degree of strength or co-ordination. His son takes
early to athletics, and perhaps excels his parent. Is this
a case of transmitted fibre and faculty ? It may be. But
how came it that the father took to athletics, and was
enabled to develop so lithe and powerful a frame ? It must
have been " in him," as we say. In other words, it must
have been a product of the germ-cells from which he was
developed. And since his son was developed, in part at
least, from a germ- cell continuous with these, what more
natural than that he too should have an inherent athletic
habit ? Every faculty that is developed in any individual
is potential in the germ-stuff from which he springs ; the

Heredity and the Origin of Variations. 149

tendency to develop any particular faculty is there too ;
and both faculty and tendency to exercise it are handed
on by the continuity of germ-protoplasm or germ-cells.
Logically, there is no escape from the argument if put as
follows: The body and all its faculties (I use the term
"faculties " in the broadest possible sense) are the product
of the germ; the acquisition of new characters or the
strengthening of old faculties by the body is therefore a
germinal product ; there is continuity of the germs of
parent and child; hence the acquisition by the child of
characters acquired by the parent is the result of germinal
or cellular continuity. It is not the acquired character
which influences the germ, but the germ which develops
what appears to be an acquired character. Finally, if an
acquired character, so called, is better developed in the
child than in the parent, what is this but an example of
variation ? And if, in a series of generations, the acquired
character continuously increases in strength, this must
be due to the continued selection of favourable variations.
It is clear that the organism that best uses its organs
has, other things equal, the best chance of survival. It
will therefore hand on to its offspring germinal matter
with an inherent tendency to make vigorous use of its
faculties.

Those who argue thus deny that the body-cells can in
any way affect the germ-cells. To account for any con-
tinuous increase in faculty, they invoke variation and the
selection of favourable varieties. What, then, we may now
ask, is, on their view, the mode of origin of variations ?

In sexual reproduction, with the union of ovum and
sperm, we seem to have a fertile source of variation. The
parents are not precisely alike, and their individual
differences are, ex hypothesi, germinal products. In the
union of ovum and sperm, therefore, we see the union of
somewhat dissimilar germs. And in sexual reproduction
we have a constantly varying series of experiments in
germinal combinations, some of which, we may fairly sup-
pose, will be successful in giving rise to new or favourable

150 Animal Life and Intelligence.

variations. This view, however, would seem to involve an
hypothesis which may be true, but which, in any case,
should be indicated. For it is clear that if new or favour-
able variations arise in this way, the germinal union
cannot be a mere mixture, but an organic combination.

An analogy will serve to indicate the distinction implied
in these phrases. It is well known that if oxygen and
hydrogen be mixed together, at a temperature over 100° C.,
there will result a gaseous substance with characters inter-
mediate between those of the two several gases which are
thus commingled. But if they are made to combine, there
will result a gas, water-vapour, with quite new properties
and characters. In like manner, if, in sexual union, there
is a mere mixture, a mere commingling of hereditary
characters, it is quite impossible that new characters
should result, or any intensification of existing characters
be produced beyond the mean of those of ovum and sperm.
If, for example, it be true, as breeders believe, that when
an organ is strongly developed in both parents it is likely
to be even more strongly developed in the offspring, and
that weakly parts tend to become still weaker, this cannot
be the result of germinal mixture. Let us suppose, for
the sake of illustration, that a pair of organisms have each
an available store of forty units of growth-force, and that
these are distributed among five sets of organs, a to e, as
in the first two columns. Then the offspring will show the
organs as arranged in the third column.*

40 40 40

* Latency is here neglected. Mr. Francis Galton lias shown, statistically,
that the offspring, among human folk, inherit J from each parent, T'g from
each grandparent, and the remaining J from more remote ancestors. In
d >mesticated animals, reversion to characters of distant ancestors sometimes
occurs. This, however, does not invalidate the argument in the text, which

Heredity and the Origin of Variations. 151

There is no increase in the set of organs a, which are
strongly developed in both parents ; and no decrease in
the set of organs e, which are weakly developed in both
parents. By sexual admixture alone there can be no
increase or decrease beyond the mean of the two parental
forms. If, then, the union of sperm and ovum be the
source of new or more favourable variations other than or
stronger than those of either parent, this must be due to
the fact that the hereditary tendencies not merely com-
mingle, but under favourable conditions combine, in some
way different indeed from, but perhaps analogous to, that /
exemplified in chemical combination.

Such organic combination, as opposed to mere com-
mixture, is altogether hypothetical, but it may be worth
while to glance at some of its implications. If it be
analogous to chemical combination, the products would
be of a definite nature; in other words, the variations
would be in definite directions. Selection and elimination
would not have to deal with variations in any and all
directions, but would have presented to them variations
specially directed along certain lines determined by the
laws of organic combination. As Professor Huxley has'
said, " It is quite conceivable that every species tends to
produce varieties of a limited number and kind, and that
the effect of natural selection is to favour the development
of some of these, while it opposes the development of others
along their predetermined line of modification." Mr.
Gulick * and others have been led to believe in a tendency
to divergent evolution residing in organic life-forms. Such
a tendency might be due to special modes of organic com-
bination giving rise to particular lines of divergence.
Again, we have seen that some naturalists believe that
specific characters are not always of utilitarian significance.
But, as was before pointed out, on the hypothesis of all-
is that sexual admixture tends towards the mean of the race (ancestors
included), and cannot be credited with new and unusually favourable variations.
The prepotency of one parent is also here neglected.

* See his valuable paper on " Divergent Evolution," Lin. Soc. Zool., No. cxx.

152 Animal Life and Intelligence.

round variation, there is nothing to give these non-useful
specific characters fixity and stability, nothing to prevent
their being swamped by intercrossing. If, however, on the
hypothesis of combination, we have definite organic com-
pounds, instead of, or as well as, mere hereditary mixtures ;
if, in other words, variations take definite lines determined
by the laws of organic combination (as the nature and
properties of chemical compounds are determined by the
laws of chemical combination) , then this difficulty disappears.
There is no reason why a neutral divergence — one neither
useful nor deleterious — should be selected or eliminated.
And if its direction is predetermined, there is no reason
why it should not persist, though, of course, it will not be
kept at a high standard by elimination. It has again and
again been pointed out as a difficulty in the path of natural
selection that, in their first inception, certain characters or
structures cannot yet be of sufficient utility to give the
possessor much advantage in the struggle for existence.
If, however, these be definite products of organic combina-
tion, this difficulty also disappears. So long as they are
not harmful, they will not be eliminated, and by fortunate
combinations will progress slowly until natural selection
gets a hold on them and pushes them forward, developing
to the full the inherent tendency. Finally, we must notice
that, on this hypothesis, our conception of panmixia, or
intercrossing, would have to be modified. As generally
held, this doctrine is based upon hereditary mixture, not
organic combination. It is a doctrine of means and
averages. There is a good deal of evidence that inter-
crossing does not, at least in all cases, produce mean or
average results. And according to the hypothesis of
organic combination, it need not always do so. According
to this hypothesis, then, divergent modifications might arise
and be perpetuated without the necessity of isolation.
Sterility might result from the fact that divergence had
been carried so far that organic combination was no longer
possible ; reversion, due to intercrossing, from the fact
that combinations long rendered impossible by the isolation

Heredity and the Origin of Variations. 153

of the necessary factors in distinct varieties, are again
rendered possible when these varieties interbreed.

On this hypothesis of organic combination, to which we
shall recur in the chapter on " Organic Evolution," the
varied forms of animal life are the outcome of definite
organic products with definite organic structure, analogous
to the definite chemical compounds with definite crystalline
and molecular structure ; and the analogy between the
regeneration of hydra and the reconstruction of a crystal
is carried on a step further. I do not say that I am myself
at present prepared to adopt the hypothesis, at least in
this crude form ; but it is, perhaps, worth a passing con-
sideration. Its connection with Mr. Herbert Spencer's
doctrine of physiological units is obvious. The analogy
there is with crystallization ; here it is with chemical
combination.

We must now return to the point which gave rise to
this digression, and repeat that mere hereditary com-
mixture in the union of ovum and sperm cannot give rise
to new characters or raise existing structures (1) where
there is free intercrossing beyond the mean of the species,
and (2) where there is rigorous elimination beyond the
existing maximum of the species. Variations beyond this
existing maximum must be due to some other cause.

Professor Weismann has suggested, as a cause of varia-
tion, the extrusion of the polar cells from the ovum. It
has before been mentioned that, generally previous to
fertilization, the ripe ovum buds off two minute polar
bodies. The nucleus of the ovum divides, and one half is
extruded in the first polar cell ; the nucleus then (except in
parthenogenetic * forms, where there is no union of ovum
and sperm) again divides, and a second polar cell is extruded.
In accordance with his special view of the absolute dis-
tinction between the body-plasm and the germ-plasm, the
first polar cell is formed to carry off the body-plasm of the

* One parthenogenetic form — the drone — has been shown by Blochmann
to extrude a second polar cell. This observation is in serious opposition to
Dr. Weismann's theory.

154 Animal Life and Intelligence.

ovum-nucleus. For the ovum, besides being a germ-bearer,
is a specialized cell, and its special form is determined by
the body-plasm it contains. This is got rid of in the first
polar cell, and nothing but germ-plasm remains. Now,
if nothing further took place, all the ova of this same
individual containing similar germ-plasm would be identical,
and similarly with all the sperms from the same parent.
The union of these similar ova from one parent with similar
sperms from another should therefore give rise to similar
offspring. But the offspring are not all similar; they
vary. Professor Weisrnann here makes use of the second
polar cell.* " A reduction of the germ-plasm," he says,
" is brought about by its formation, a reduction not only
in quantity, but above all, in the complexity of its constitu-
tion. By means of the second nuclear division, the excessive
accumulation of different kinds of hereditary tendencies or
germ-plasms is prevented. With the nucleus of the second
polar body, as many different kinds of plasm are removed
from the egg as will be afterwards introduced by the sperm-
nucleus." " If, therefore, every egg expels half the number
of its ancestral germ-plasms during maturation, the germ-
cells of the same mother cannot contain the same hereditary
tendencies, unless we make the supposition that corre-
sponding ancestral germ-plasms chance to be retained by
all eggs— a supposition that cannot be sustained."

The two polar cells are therefore, on this view, of totally
different character ; and the nuclear division in each case
of a special kind and sui generis. I do not think that the
evidence afforded by observation lends much support to
this view. But with that we are not here specially con-
cerned. We have to consider how this reduction of the
number of ancestral germ-plasms can further the kind of
variation required. Now, it is difficult to see, and Professor
Weismann does not explain, how the getting rid of certain
ancestral tendencies can give rise to new characters or the
enhancement of old characters. One can understand how
this "reducing division," as Dr. Weismann calls it, can

* Weismann, "Essays on Heredity," pp. 355, b78.

Heredity and the Origin of Variations. 155

reduce the level of now one and now another character.
But how it can raise the level beyond that attained by
either parent is not obvious. It is perhaps possible, though
Professor Weismann does not, I think, suggest it, that, by
a kind of compensation,* the reduction of certain characters
may lead to the enhancement of others. Let us revert to
the illustration on p. 150, where each individual has an
available store -of forty units of growth- force ; and let us
express by the minus sign the units lost in the parents by
the extrusion of the polar cell and an analogous process
which may occur in the genesis of the sperm. Then the
units of growth-force which may thus be lost by a " reducing
division " in b, c, and e may be, in the offspring, applied
to the further growth of a ; thus —

a 10 10 14

b 8-1 10-3 7

c 9-1 5-1 6

d 7 9 8

e 6-2 6 5

Here the reduction of the characters b, c, and e has
led to the enhancement of a, which thus stands at a higher
level than in either parent.

On such an hypothesis we may, perhaps, explain the
fact to which breeders of stock testify — that the organ
strongly developed in both parents (a) is yet more strongly
developed in some of their offspring, and that weakly parts
(e) tend to become still weaker. I know not whether this
way of putting the matter would commend itself to Professor
Weismann or his followers ; but some such additional
hypothesis of transference of growth-force from one set of
organs to another set of organs seems necessary to complete
his hypothesis.

Professor Weismann's view, then, assumes (1) that the
cell-division which gives rise to the ova in the ovary is so
absolutely equal and similar that all ova have precisely

* The law of compensation of growth or balancemeut was suggested at
nearly the same time by Goethe and Geoffroy Saint-Hilaire. The application
iii the text lias not, so far as I know, been before suggested.

156 Animal Life and Intelligence.

the same characters ; (2) that the first polar cell leaves
the germinal matter unaffected, merely getting rid of
formative body-plasm ; (3) that the nuclear division giving
rise to the second polar cell is unequal and dissimilar,
effecting the differential reduction of ancestral germ-
plasms. Concerning all of which one can only say that
it may be so, but that there is not much evidence that it
is so. And, without strong confirmatory evidence, it is
questionable whether we are justified in assuming these
three quite different modes of nuclear division.

There remains one more question for consideration, on
the hypothesis that the germ-cells cannot in any special
way be affected by the body-cells. In considering the
union of ovum and sperm as a source of variation, we have
taken for granted the existence, of variations. We have
been dealing with the mixture or combination of already
existing variations. How were variations started in the
first instance ?

We have already seen that in the protozoa parent and
offspring are still, in a certain sense, one and the same
thing ; the child is a part, and usually half, of the parent.
If, therefore, the individuals of a unicellular species are
acted upon by any of the various external influences, it is
inevitable that hereditary individual differences will arise
in them ; and, as a matter of fact, it is indisputable that
changes are thus produced in these organisms, and that
the resulting characters are transmitted. Hereditary
variability cannot, however, arise in the metazoa, in which
the germ-plasm and the body-plasm are differentiated and
kept distinct. It can only arise in the lowest unicellular
organisms. But when once individual difference had been
attained by these, it necessarily passed over into the
higher organisms when they first appeared. Sexual repro-
duction coming into existence at the same time, the
hereditary differences were increased and multiplied, and
arranged in ever-changing combinations. Such is Pro-
fessor Weismann's solution of the difficulty, told, for the
most part, in his own words,

Heredity and the Origin of Variations. 157

I do not know that Professor Weismann has anywhere
distinctly stated what he conceives to be the relation of
body-plasm and germ-plasm in the protozoa. Are the two
as yet undifferentiated ? This can hardly be so, seeing the
fundamental distinction he draws between them. Is it
the germ-plasm or the body-plasm that is influenced by
external stresses? If the former, does it transfer its
influence to the body-plasm during the life of the indi-
vidual? If the latter, then the body-plasm must either
directly influence the germ-plasm in unicellular organisms
(it would seem that, according to Professor Weismann, it
cannot do so in the metazoa), or the changed body-plasm,
which shares in the fission of the protozoon, must participate
in that so-called immortality which is often said to be the
special prerogative of germinal matter.

These, however, are matters for Professor Weismann
and his followers to settle. I regard the sharp distinction
between body-plasm and germ-plasm as an interesting
biological myth. For me, it is sufficient that the proto-
plasm of the protozoon is modified, and the modification
handed on in fission. And it is clear that Professor
Weismann is correct in saying that the commixture or
combination of characters takes its origin among the
protozoa. If the unicellular individuals are differently
modified, however slightly, then, whenever conjugation
occurs between two such individuals, there will be a com-
mingling or combination of the different characters. The
transmissible influence of the environment, however, ceases
when the metazoon status is reached, and special cells are
set apart for reproductive purposes — ceases, that is to say,
in so far as the influence on the body is concerned. There
may, of course, be still some direct* influence on the
germinal cells themselves. Except for this further in-
fluence, the metazoon starts with the stock of variations

* Darwin spoke of changed conditions acting " directly on the organization
or indirectly through the reproductive system." Now, since Professor Weis-
mann has taught us to reconsider these questions, we speak of such conditions
as acting directly on the germ or indirectly through the body. The germ is
no longer subordinate to the body, but the body to the germ.

158 Animal Life and Intelligence.

acquired by that particular group of protozoa — whatever it
may be — from which it originated. All future variations
in even the highest metazoa arise from these.

Now, it is obvious that no mere commingling and re-
arrangement of protozoan characters could conceivably
give rise to the indefinitely more complex metazoan
characters. But if there be a combination and recom-
bination of these elements in ever-varying groups, the
possibilities are no longer limited. Let us suppose that
three simple protozoan characters were acquired. The
mere commixture of these three could not give much scope
for further variation. It would be like mixing carbon,
oxygen, and hydrogen in varying proportions. But let
them in some way combine, and you have, perhaps, such
varied possibilities as are open to chemical combinations
of oxygen, hydrogen, and carbon, whose name is legion,
but whose character is determined by the laws of chemical
combination.

Summing up now the origin of variations, apart from
those which are merely individual, on the hypothesis that
particular modifications of the body-cells cannot be trans-
mitted to the germ-cells, we have —

1. In protozoa, the direct influence of the environment
and the induced development of faculty.

2. In metazoa —

(a) Some direct and merely general influence of the
environment on the germ, including under the term " en-
vironment " the nutrition, etc., furnished by the body.

(b) The combination and recombination of elementary
protoplasmic faculties (specific molecular groupings) ac-
quired by the protozoa.

(c) Influences on the germ, the nature of which is at
present unknown.

We may now pass on to consider the position of those
who give an affirmative answer to the question — Can the
body affect the germ ? Two things are here required.
First, definite evidence of the fact that the body does so

Heredity and the Origin of Variations. 159

affect the germ ; i.e. that acquired characters are inherited.
Secondly, some answer to the question — How are the body-
cells able to transmit their modifications to the germ-cells ?
We will take the latter first, assuming the former point to
be admitted.

Let us clearly understand the question. An individual,
in the course of its life, has some part of the epidermis, or
skin, thickened by mechanical stresses, or some group of
muscles strengthened by use, or the activity of certain
brain-cells quickened by exercise : how are the special
modifications of these cells, here, there, or elsewhere in the,
body, communicated to the germ, so that its products are
similarly modified in the offspring ? The following are
some of the hypotheses which have been suggested : —

(a) Darwin's pangenesis.

(6) Haeckel's perigenesis ; Spencer's physiological units.

(c) The conversion of germ-plasm into body-plasm, and
its return to the condition of germ-plasm (Nageli).

(d) The unity of the organism.

(a) Concerning pangenesis, nothing need be added to
what has already been said. Although, as we have seen,
it has been adopted with modifications by Professor Brooks ;
although Mr. Francis Galton, a thinker of rare ability and
a pioneer in these matters, while contending for continuity,
admitted a little dose of pangenesis ; although De Vries
has recently renewed the attempt to combine continuity
and a modified pangenesis ; — this hypothesis does not now
meet with any wide acceptance.

(b) With the pamphlet in which Professor Haeckel
brought forward his hypothesis termed the perigenesis of
the plastidule, I cannot claim first-hand acquaintance.
According to Professor Bay Lankester, who gave some
account of it in Nature,* protoplasm is regarded by Haeckel
as consisting of certain organic molecules called plasti-
dules. These plastidules are possessed of special undulatory
movements, or vibrations. They are liable to have their
undulations affected by every external force, and, once

* July 15, 1876. Since reprinted iu " The Advancement of Science," p. 273.

160 Animal Life and Intelligence.

modified, the movement does not return to its pristine
condition. By assimilation, they continually increase to a
certain size and then divide, and thus perpetuate in the
undulatory movement of successive generations the im-
pressions or resultants due to the action of external
agencies on the individual plastidules. On this view, then,
the form and structure of the organism are due to the
special mode of vibration of the constituent plastidules.
This vibration is affected by external forces. The modified
vibration is transmitted to the plastidules by the germ,
which, therefore, produce a similarly modified organism.
As Mr. J. A. Thomson says, "In metaphorical language,
the molecules remember or persist in the rhythmic dance
which they have learned."

Darwin's hypothesis was frankly and simply organic —
the gemmules are little germs. This of Professor Haeckel
tries to go deeper, and to explain organic phenomena in
terms of molecular motion. Mr. Herbert Spencer long ago
suggested that, just as molecules are built up, through
polarity, into crystals, so physiological units are built up,
under the laws of organic growth, into definite and special
organic forms. Both views involve special units. With
Mr. Herbert Spencer, their " polarity " is the main feature ;
with Professor Haeckel, their "undulatory movements."
According to Mr. Spencer, " if the structure of an organism
is modified by modified function, it will impress some
corresponding modification on the structures and polarities
of its units." * According to Professor Haeckel, the vibra-
tions of the plastidules are permanently affected by external
forces. In either case, an explanation is sought in terms
of molecular science, or rather, perhaps, on molecular
analogies. So far good. Such " explanation," if hypo-
thetical, may be suggestive. It may well be that the pos-
sibilities of fruitful advance will be found on these lines.

But though, as general theories, these suggestions may
be valuable, they do not help us much in the comprehen-
sion of our special point. To talk vaguely about " undula-

* Herbert Spercer, " Principles of Biology," vol. i. p. 256.

Heredity and the Origin of Variations. 161

torj movements " or " polarities " does not enable us to
comprehend with any definiteness how this particular modi-
fication of these particular nerve-cells is so conveyed to the
germ that it shall produce an organism with analogous
nerve-cells modified in this particular way.

(c) The hypothesis that the germ-plasm may be con-
verted into body-plasm, which, on its return again to the
condition of germ-plasm, may retain some of the modifi-
cations it received as body-plasm, seems to be negatived,
so far as most animals are concerned, by the facts of
embryology and development. The distinction of germ-
plasm and body-plasm I hold to be mythical. And there
is no evidence that cells specially differentiated along
certain lines can become undifferentiated again, and then
contribute to the formation of ova or sperms. From the
view-point of cell- differentiation, which seems to me the
most tenable position, there does not seem any evidence
for, or any probability of, the occurrence of any roundabout
mode of development of the germinal cells which could
enable them to pick up acquired characters en route.

(d) We come now to the contention that the organism,
being one and continuous, if any member suffers, the germ
suffers with it. The organs of the body are not isolated or
insulated ; the blood is a common medium ; the nerves
ramify everywhere ; the various parts are mutually de-
pendent : may we not, therefore, legitimately suppose that
long-continued modification of structure or faculty would
soak through the organism so completely as eventually to
modify the germ ? The possibility may fairly be admitted.
But how is the influence of the body brought to bear on
the germ ? The common medium of the blood, proto-
plasmic continuity, the influence of the products of chemical
or organic change, — these are well enough as vague sug-
gestions. But how do they produce their effects ? Once
more, how is this increased power in that biceps muscle
of the oarsman able to impress itself upon the sperms or
the ova ? No_defini^e answer can be given.

We are obliged to confess, then, that no definite and

M

1 62 Animal Life and Intelligence.

satisfactory answer can be given to the question — How can
the body affect the germ so that this or that particular
modification of body-cells may be transmitted to the
offspring ? We may make plausible guesses, or we may
say — I know not how the transmission is effected ; but there
is the indubitable fact.

This leads us to the evidence of the fact.

It must be remembered that no one questions the
modifiability of the individual. That the epidermis of the
oarsman's hand is thickened and hardened ; that muscles
increase by exercise; that the capacity for thinking may
be developed by steady application ; — these facts nobody
doubts. That well-fed fish grow to a larger size than their
ill-fed brethren; that if the larger shin-bone (the tibia)
of a dog be removed, the smaller shin-bone (the fibula) soon
acquires a size equal to or greater than that of the normal
tibia ; that if the humerus, or arm-bone, be shifted through
accident, a new or false joint will be formed, while the old
cavity in which the head of the bone normally works, fills
up and disappears ; that canaries fed on cayenne pepper
have the colour of the plumage deepened, and bullfinches
fed on hemp-seed become black ; that the common green
Amazonian parrot, if fed with the fat of siluroid fishes,
becomes beautifully variegated with red and yellow ; that
climate affects the hairiness of mammals ; — these and many
other reactions of the individual organism in response to
environing conditions, will be admitted by every one.*
That constitutional characters of germinal origin are in-
herited is also universally admitted. The difficulty is to
produce convincing evidence that what is acquired is really
inherited, and what is inherited has been really acquired.

Attempts have been made to furnish such evidence by
showing that certain mutilations have been inherited. I
question -whether many of these cases will withstand rigid

* Mr. J. A. Thomson has published a most valuable " Synthetic Summary
of the Influence of the Environment upon the Organism " (Proceedings Koyal
Physiological Society, Edinburgh : vol. ix. pt. o, 1888). The case of the
Amaz"niau parrots was communicated to Darwin by Mr. Wallace ("Animals
and Plants under Domestication," vol. ii. p. 269).

Heredity and the Origin of Variations. 163

criticism. Nor do I think that mutilations are likely to
afford the right sort of evidence one way or the other. We
must look to less abnormal influences. What we require
is evidence in favour of or against the supposition that
modifications of the body-cells are transmitted to the germ-
cells. Now, these modifications must clearly be of such a
nature as to be receivable by the cells without in any way
destroying their integrity. The destruction or removal of
cells is something very different from this. If it were
proved that mutilations are inherited, this would not
necessarily show that normal cell-modifications are trans-
missible. And if the evidence in favour of inherited
mutilations breaks down, as I believe it does, this does not
show that more normal modifications such as those with
which we are familiar, as occurring in the course of indi-
vidual life, are not capable of transmission. I repeat, we
must not look to mutilations for evidence for or against the
supposition that acquired characters are inherited. We
must look to less abnormal influences.

These readily divide themselves into two classes. The
first includes the direct effects on the organism of the
environment — effects, for example, wrought by changes of
climate, alteration of the medium in which the organism
lives, and so forth. The second comprises the effects of
use and disuse — the changes in the organism wrought by
the exercise of function.

Taking the former first, we have the remarkable case of
Saturnia, which was communicated to Darwin by Moritz
Wagner. Mr. Mivart thus summarizes it : "A number of
pupas were brought, in 1870, to Switzerland from Texas of
a species of Saturnia, widely different from European
species. In May, 1871, the moths developed out of the
cocoons (which had spent the winter in Switzerland), and
resembled entirely the Texan species. Their young were
fed on leaves of Juglans regia (the Texan form feeding on
Juglans nigra), and they changed into moths so different,
not only in colour, but also in form, from their parents,
that they were reckoned by entomologists as a distinct

164 Animal Life and Intelligence.

species."* Professor Mivart also reminds us that English
oysters transported to the Mediterranean are recorded by
M. Costa to have become rapidly like the true Mediterranean
oyster, altering their manner of growth, and forming
prominent diverging rays ; that setters bred at Delhi from
carefully paired parents had young with nostrils more
contracted, noses more pointed, size inferior, and limbs
more slender than well-bred setters ought to have ; and
that cats at Mombas, on the coast of Africa, have short,
stiff hair instead of fur, while a cat from Algoa Bay,
when left only eight weeks at Mombas, underwent a com- -
plete metamorphosis — having parted with its sandy-
coloured fur. Very remarkable is the case of the brine-
shrimp Artemia, as observed and described by Schmanke-
witsch. One species of this crustacean, Artemia salina,
lives in brackish water, while A. milhausenii inhabits water
which is much salter. They have always been regarded
as distinct species, differing in the form of the tail-lobes
and the character of the spines they bear. And yet, by
gradually altering the saltness of the water, either of them
was transformed into the other in the course of a few
generations. So long as the altered conditions remained
the same, the change of form was maintained.

Many naturalists believe that climate has a direct and
determining effect on colour, and contend or imply that it
is hereditary. Mr. J. A. Allen correlates a decrease in the
intensity of colour with a decrease in the humidity of the
climate. Mr. Charles Dixon, in his "Evolution without
Natural Selection," says, " The marsh-tit (Parus palustris)
and its various forms supply us with similar facts [illus-
trative of the effects of climate on the colours of birds].
In warm, pluvial regions we find the brown intensified;
in dry, sandy districts it is lighter; whilst in Arctic
regions it is of variable degrees of paleness, until, in the
rigorous climate of Kamschatka, it is almost white." Mr.
Dixon does not think that these changes are the result of
natural selection. " Depend upon it," he says, with some

* St. George Mivart, " On Truth," p. 378.

Heredity and the Origin of Variations. 165

assurance,* in considering a different case, " it is the white
of the ptarmigan (modified by climatic influence) that has
sent the bird to the snowy wastes and bare mountain-tops,
and rigorously keeps it there; not the bird that has
assumed, by a long process of natural selection, a white
dress to conceal itself in such localities." Professor
Eimerf contends that in the Nile valley the perfectly
gradual transition in the colour of the inhabitants from
brownish-yellow to black in passing from the Delta to the
Soudan is particularly conclusive for the direct influence
of climate, for the reason that various races of originally
various colours dwell there.

Mr. A. E. Wallace saysj of the island of Celebes
"that it gives to a large number of species and varieties
(of Papilionidse) which inhabit it, (1) an increase of size, and
(2) a peculiar modification in the form of the wings, which
stamp upon the most dissimilar insects a mark distinctive
of their common birthplace." But this similarity may
largely, or at least in part, be due to mimicry. Most
interesting and valuable are the results of Mr. E. B.
Poulton's experiments on caterpillars and chrysalids.§ They
show that there is a definite colour-relation between the
caterpillar (e.g. the eyed hawk-moth, Smerinthus ocellatus)
and its food-plant, adjustable within the limits of a single
life ; that the predominant colour of the food-plant is itself
the stimulus which calls up a corresponding larval colour ;
that there is also a direct colour-relation between the
chrysalids of the small tortoiseshell butterfly (Vanessa
urticcK) and the surrounding objects, the pupae being dark
grey, light grey, or golden, according to the nature and

* Op. cit., p. 47. I venture to say, " with some assurance," because Charles
Darwin, who had also considered this matter, writes, "Who will pretend
to decide how far the thick fur of Arctic animals, or their white colour, is
due to the direct action of a severe climate, and bow far to the preservation of
the best-protected individuals during a long succession of generations ? "
(" Animals and Plants under Domestication," p. 415).

t "Organic Evolution," English translation, p. 88.

J " Contributions to Natural Selection," p. 197.

§ Since this was written, Mr. Poulton has described his results in an
interesting volume on " The Colours of Animals "

1 66 Animal Life and Intelligence.

colour of the surroundings; and that the larvae of the
emperor moth (Saturnia carpini] spin dark cocoons in dark
surroundings, but white ones in lighter surroundings.
These are but samples of the interesting results Mr.
Poulton has obtained.

What shall we say of such cases ? Some of them seem
to indicate the very remarkable and interesting fact that
changes of salinity of the medium, or changes of food, or
the more general influence of a special climate, may modify
organisms in particular and little-related ways. The larvae
of a Texan Saturnia fed on a new food-plant develop into
images so modified as to appear new species. Changes of
salinity of the water modify one species of Artemia into
another. If these be adaptations, the nature of the
adaptation is not obvious. If the new character produced
in this way be of utilitarian value, where the utility comes
in is not clear. The facts need further confirmation and
extension, which may lead to very valuable results. Mr.
Poulton's observations, on the other hand, give us evidence
of direct adaptation to colour- surroundings. But the effects
are, in the main, restricted to the individual. What is
hereditary is the power to assume one of two or three
tints, that one being determined by the surrounding colour.
His experiments neither justify a denial nor involve an
assertion of the transmissibility of environmental in-
fluence. Secondly, some of the cases above cited seem to
show clearly that, under changed conditions of life, the
changes which have been wrought in one generation may
reappear in the next. But are they inherited ? Is there
sufficient evidence to show conclusively that the body-cells
have been modified, and have handed on the modification
to the germ? Can we exclude the direct action of the
more or less saline water, or the products of the unwonted
food on the germinal cells ? Can we be sure that there is
really a summation of results — that each generation is not
affected de novo in a similar manner ? No one questions
that the individual is modifiable, and that such modifica-
tion is most readily effected in the early and plastic stages

Heredity and the Origin of Variations. 167

of life. If each plastic embryo is moulded in turn by
similar influence, how can we conclusivly prove hereditary
summation ? Take a case that has been quoted in support
of hereditary modification. Greyhounds transported from
England to the uplands of Mexico are unable to course,
owing to the rarity of the atmosphere. Their pups are,
however, able to run down the fleetest hares without
difficulty. Now, this may be due to the fact that the dogs
acquire a certain amount of accommodation to a rare
atmosphere, and hand on their acquired power to their
offspring, which carry it on towards perfection. But it
may also be due to the fact that the pups, subject from the
moment of birth to the conditions of a rarified atmosphere,
are developed in accordance with these conditions.

Or take another case that has been brought forward.
English dogs are known in hot climates, like that of India,
to degenerate in a few generations. Let us suppose that
these degenerate dogs are removed back to England, and
that their pups, born in English air and in our temperate
climate, are still degenerate : would not this, it may be
asked, show that the influence of climate on the body is
inherited ? I do not think that such a case would be
convincing. For the climate might well influence the
germ through the body. The body being unhealthy and
degenerate, the germ-cells must, one may suppose, suffer
too. The degenerate pup born in England might well owe
its degeneracy to effects wrought upon the germinal cells.
In other words, such a case would indicate some general
influence of the environment (including the environing
body) on the germ. It does not convince us that particular
modifications of body-cells as such are transmitted under
normal and healthy conditions.

On the whole, it seems to me that the evidence we at
present possess on this head is not convincing or conclu-
sive in favour of the effects on the body alone being
transmitted to offspring. If cases can be brought forward
in which there can be no direct influence on the germ, in
which elimination is practically excluded, and in which

1 68 Animal Life and Intelligence.

there is a gradual and increasing accommodation of succes-
sive generations of organisms to changed conditions which
remain constant, then such transmission will be rendered
probable. I do not know that there are observations of
this kind of sufficient accuracy to warrant our accepting
this conclusion as definitely proved.

Attention may here be drawn to a peculiar and remark-
able mode of influence. If a pure-bred mare have foals by
an ill-bred sire, they will be ill-bred. This we can readily
understand. But if she subsequently have a foal by a
perfectly well-bred sire, that foal, too, may in some cases
be tainted by the blemish of the previous sire. So, too,
with dogs. If a pure-bred bitch once produce a mongrel
litter, no matter how carefully she be subsequently
matched, she will have a tendency to give birth to pups
with a mongrel taint. This subsequent influence of a
previous sire is a puzzling fact. It may be that some of
the male germ-nuclei are absorbed, and influence the germ-
cells of the ovary. But this seems an improbable solution
of the problem. It is more likely, perhaps, that in the
close relation of mother and foetus during gestation, each
influences the other (how it is difficult to say). On this
view the bitch retains the influence of the mongrel puppies
— is herself, in fact, partially mongrelized — and therefore
mongrelizes subsequent litters. It would not be safe, how-
ever, to base any far-reaching conclusions on so peculiar a
case, the explanation of which is so difficult. At all events,
it is impossible to exclude the possibility of direct action on
the germ, though the particular nature of the results of
such influence are noteworthy.

We may pass now to the evidence that has been adduced
in favour of a cumulative effect in the exercise of function,
or of the inheritance of the results of use or disuse. Here,
again, it must be remembered that no one questions the
effects of use and disuse in the individual. What we seek
is convincing evidence that such effects are inherited.

Physiologically, the effects of use or disuse are, in the
main, effects on the relative nutrition, and hence on the

Heredity and the Origin of Variations. 169

differential growth of organs. When an organ is well
exercised, there is increased nutrition and increased growth
of tissue, muscular, nervous, glandular, or other. When
an organ is, so to speak, neglected, there is diminished
blood-supply, diminished growth, and diminished functional
power. The development of a complex activity would
necessitate a complex adjustment of size and efficiency of
parts, involving a nice balance of differential growth de-
pendent on delicately regulated nutrition. What is the
evidence that adjusted nutrition can be inherited ?

With regard to man, there is some evidence which bears
upon this subject. Mr. Arbuthnot Lane, in his valuable
papers in the Journal of Anatomy and Physiology, has shown
that certain occupations, such as shoemaking, coal-heaving,
etc., produce recognizable effects upon the skeleton, the
muscular system, and other parts of the organization. And
he believes * that such effects are inherited, being very
much more marked in the third generation than they were
in the first. Sir William Turner informed Professor Herd-
man that, in his opinion, the peculiar habits of a tribe, such
as tree-climbing among the Australians, or those natives
of the interior of New Guinea whose houses are built in
the upper branches of lofty trees, not only affect each
generation individually, but have an intensified action
through the influence of heredity, t

Mr. Francis Galton's results mainly deal with human
faculty; and though faculty has undoubtedly an organic
basis, I do not propose to consider the evidence afforded
by instinct, intelligence, or intellectual faculties in this
chapter. Mention should, however, be made of the in-
teresting results of his study of twins. Twins are either
of the same sex, in which case they are remarkably alike,
or of different sexes, in which case they are apt to differ
even more widely than is usual with brothers and sisters.
The former are believed to be developed from one ovum

* See Journal of Anatomy and Physiology, vol. xxii. p. 215.
f See Professor Herdmau's Inaugural Address, Liverpool Biological
Society, 1888.

i /o Animal Life and Intelligence.

which has divided into two halves, each of which has given
rise to a distinct individual ; the latter from two different
ova. Mr. Galton collected a large mass of statistics con-
cerning twins of both classes. The result of this analysis
seems to be that, in the case of "identical twins," the
resemblances are not superficial, but extremely intimate ;
that they are not apt to be modified to any large extent
by the circumstances of life ; that where marked diversity
sets in it is due to some form of illness ; and, on the whole,
that innate tendencies outmaster acquired modifications.
"Nature is far stronger than nurture within the limited
range that I have been careful to assign to the latter." On
the other hand, speaking of dissimilar twins, Mr. Galton
says, "I have not a single case in which my correspondents
speak of originally dissimilar characters having become
assimilated through identity of nurture." " The impres-
sion that all this evidence leaves on the mind is one of
some wonder whether nurture can do anything at all,
beyond giving instruction and professional training."
" There is no escape from the conclusion that nature pre-
vails enormously over nurture where the differences of
nurture do not exceed what is commonly to be found among
persons of the same rank of society and in the same
country." *

Combining the results of Messrs. Lane and Galton,
we may say that it requires persistent and long-continued
influence to modify the individual, and change, even by a
little, the structure inherited or given by nature ; but that
if this structure is thus modified, there may be a tendency
for such modification to increase by hereditary summation
of effects. We require, however, further and fuller observa-
tions to render the evidence of such hereditary summation
to any extent convincing.

Turning now from the evidence afforded by man t to

* Francis Galton, " Inquiries into Human Faculty," p. 216.

f That the epidermis is thicker on the palms of the hands and the soles
of the feet in the infant long before birth, may be attributable to the inherited
effects of use or pressure. It can hardly be held that the thickening of the
skin in these parts is of elimination value.

Heredity and the Origin of Variations. 171

that afforded by animals, we may consider first that pre-
sented by domesticated breeds. They might be expected
to afford exceptionally good examples. Their modifiability
and the readiness with which they interbreed are two of
the determining causes of their selection for domestication.
They have, moreover, been placed under new conditions of
life, and they undoubtedly exhibit changes of structure,
many of which Darwin * regarded as attributable to the
effects of use and disuse. In domestic ducks, the relative
weight and strength of the wing-bones have been diminished,
while conversely the weight and strength of the leg-bones
have been increased. The bones of the shoulder-girdle have
been decreased in weight and "the prominence of the crest
of the sternum, relatively to its length, is also much re-
duced in all the domestic breeds. These changes," says
Darwin, "have evidently been caused by the lessened use
of the wings." The shoulder-girdle and breast-bone of
domestic fowls have been similarly reduced. After a care-
ful consideration of numerous facts concerning the brains
of rabbits, Darwin concluded that this " most important
and complicated organ in the whole organization is subject
to the law of decrease in size from disuse." And Sir J.
Crichton Browne has recently shown that, in the wild duck,
the brain is nearly twice as heavy in proportion to the body
as it is in the comparatively imbecile domestic duck. In
pigs, the nature of the food supplied during many genera-
tions has apparently affected the length of the intestines ;
for, according to Cuvier, their length to that of the body
in the wild boar is as 9 to 1, in the common domestic boar
as 13-5 to 1, and in the Siam breed as 16 to 1. With
regard to horses, Darwin tells us that " veterinarians are
unanimous that horses are affected with spavins, splints,
ring-bones, etc., from being shod and from travelling on
hard roads, and they are almost unanimous that a tendency
to these malformations is transmitted."

These are samples of the effects of domestication. It
has been suggested, however, that, quite apart from any
* The instances cited are from " Animals and Plants under Domestication."

172 Animal Life and Intelligence.

diminution from disuse, the reduction of size in parts or
organs may be the result of the absence or cessation of
selection. If an organ be subject to selection, the mean
size in adult creatures will be that of the selected indi-
viduals ; but if selection ceases, it will be the mean of those
born. Let us suppose that nine individuals are born, and
that the size of some organ varies in these from 1, the
most efficient, to 9, the least efficient. The birth-mean will
therefore be, as shown on the left-hand side of the follow-
ing table, at the level of number 5, four being more
efficient, and four less efficient. But if, of these nine, six be
eliminated, then the mean of the survivals will be as shown
on the right-hand side of the table : —

i

2— Survival-mean.
3
4\
Birth-mean — 5 j

7 \ Eliminated individuals.

s)

The result, then, of the cessation of selection will be to
reduce the survival-mean to the birth-mean, and that with-
out any necessary effect of disuse. But unless this be
accompanied by a tendency to diminution due to economy
of growth or some other cause, this cannot produce any
well-marked or considerable amount of reduction. I very
much question, for example, whether the cessation of
selection, even with the co-operation of the principle of
economy of growth, will adequately account for the reduc-
tion to nearly one-half its original proportion of the brain
of the duck. The subject will be more fully discussed,
however, in the next chapter.

There is probably but little tendency for disused parts
to be reduced in size through artificial selection. An
imbecile duck does not probably taste nicer than one with
bigger brains. On the other hand, the increase of size in
organs may presumably, in certain cases, be increased by
selection. Pigs, for example, have been selected according

Heredity and the Origin of Variations. 173

to their fattening capacity. Those with longer intestines,
and therefore increased absorbent surface, may well have
an advantage in this respect. Hence, in selecting pigs for
fattening, breeders may have been unconsciously selecting
those with the longest intestines. Of course, on this view,
the longer intestine must be there to be selected, and the
increased length must be due to variation. But this may
be all-round variation (cause unknown), not variation in
one direction, the result of increased function.

Another point that has to be taken into consideration
is the amount of individual increment or decrement, owing
to individual use or disuse, apart from any possible
summation of results.

Seeing, then, that it is difficult to estimate the amount
of purely individual increment or decrement, and that it is
difficult, if not impossible, to exclude the disturbing effects
of cessation of selection with economy of growth on the
one hand, reducing the size of organs, and artificial
selection on the other hand, increasing the size or efficiency
of parts, it is clear that such cases cannot afford convincing
evidence that the observed variations are the directly
inherited results of use and disuse. Indeed, I am not
aware of any experiments or direct observations on animals
which are individually conclusive in favour of the hereditary
summation of functionally produced modifications.

It may, however, be said — Although no absolutely con-
vincing experiments or observations are forthcoming (for,
from the nature of the case, it is almost impossible logically
to prove that this interpretation of the facts is alone
possible), still there are cases which are much more readily
explained on the hypothesis that the effects of use and
disuse are inherited, than on any other hypothesis. But,
so far as Professor Weismann and his followers are con-
cerned, such an argument is wholly beside the question.
They are ready to admit that inherited modifications of the
body, if they could be proved, would render the explanation
of many results of evolution much easier. It would, no
doubt, they say, be easier to account for the shifting of the

174 Animal Life and Intelligence.

eye of a flat-fish from one side of the head to the other on
the supposition that individual efforts were inherited, until,
by an hereditary summation of effort, the eye at last came
round. The question is — Are we justified in accepting the
easier explanation if it be based on a mere assumption, at
present unproved, the modus operandi of which is in-
explicable ?

Let us consider very briefly these two points — first, the
" mere assumption ; " secondly, " the inexplicable modus
operandi." Is there any reason why we should not assume
the inheritance of effects of use or disuse as a working
hypothesis, if it is not in opposition to any known biological
law, and if it does enable us to explain certain observed
phenomena ? I see no such reason. We do not know
enough about the causes of variation to be rigidly bound
by the law of parcimony. I am not aware of any biological
law that would render the acceptance of this view as a
provisional hypothesis unjustifiable.

But how, it is asked, can we accept it if its modus
operandi is inexplicable ? I question the validity of this
argument. I fear our knowledge of organic nature is not
at present so full and exact as to justify us in excluding
an hypothesis because we are not able to give an adequate
answer to the question — How are these effects produced ?
Of course, if it can be shown that no modus operandi is
possible, there is an end of the matter. But who shall
dare thus to limit the possibilities of organic nature ?
And, if possible, then that natural selection in which the
neo-Darwinians place their sole trust would certainly
develop so advantageous a mode of influence. It is clear
that a species sensitive to every shock of the environment
on the organism would be unstable, and hence at a dis-
advantage. But, on the other hand, the ability to answer
by adaptation to long-continued and persistent environ-
mental influence or to oft-repeated and consistent per-
formance of function would be so distinct an advantage to
the species which possessed it, that, if it lay within the
possibilities of organic nature, natural selection, always, as

Heredity and the Origin of Variations. 1 75

we are told, on the look out for every possible advantage,
would assuredly seize upon it and develop it.

Those who believe in the absolute sway of natural
selection have not at present given any adequate answer
to the question — How are particular variations (e.g. the
twisted skull of flat-fish) produced ? They say that con-
stitutional variations, which are alone inheritable, are due
to variations in the germs. When asked how these
variations are produced, they are forced to reply — We
cannot say. But when it is suggested that they may be
in some unknown way transmitted to the germ from the
body, they are up in arms, and exclaim — You have no
right to believe that, or ask us to believe it, unless you can
tell us plainly how the effect is produced. Unable them-
selves to give the modus operandi of the origin of particular
variations, they demand the exact modus operandi from
those who suggest that variations may arise through this
mode of influence of the body on the germ.

We shall have to consider this question from a more
general standpoint in the next chapter on " Organic Evolu-
tion." We may now very briefly summarize some of the
results we have reached in this chapter.

The ova and sperms are specially differentiated cells
which have, in the division of labour, retained and empha-
sized the function of developmental reproduction.

There is a continuity of such cells. The cells which
become ova or sperms have never become differentiated into
anything else.

Hereditary similarity is due to the fact that parents and
offspring are derived eventually from the same germinal cells.

Variation in the existing world is partly due to sexual
union. But if there be mere admixture, new characters
cannot arise in this way, nor can old characters be
strengthened beyond the existing maximum.

Some mode of organic combination (analogous to
chemical combination) might afford an explanation of the
occurrence of new variations and the increase of existing
characters.

176 Animal Life and Intelligence.

In the protozoa there may be a summation of the effects
of the environment in succeeding generations.

There is no convincing evidence that in the metazoa
special modifications of the body so influence the germ
as to become hereditary.

But there is no reason why such influence should not
be assumed as a provisional hypothesis.

CHAPTER VI.

ORGANIC EVOLUTION.

IT is difficult to realize the wealth, the variety, the diversity,
of "animal life." Even if we endeavour to pass in review
all that we have seen in woodland and meadow, in pond
or pool, in the air, on the earth, in the waters, in temperate
or tropical regions ; even when we try to remember the
results of all anatomical and microscopic investigation dis-
playing new wonders and new diversities hidden from
ordinary and unaided vision ; even when we call to mind
the multifarious contents, recent and fossil, of all the
natural history museums we have ever visited, and throw
in such mental pictures as we have formed of all the diverse
adaptations we have read about or heard described ; — even
so we cannot but be conscious that not one-tenth, not one-
hundredth, part of the diversity and variety of animal life
has passed before our mental vision even in sample. It is
said that our greatest living poet once, when a young man,
left his companions to gaze into the waters of a clear, still
pool. " What an imagination God has ! " he said, as he
rejoined his friends. Fit observation for the poet, whose
sensitive nature must be keenly alive to the varied endow-
ments which Nature has lavishly showered upon her
animate children.

Certain it is that words, mere words, can never present,
though they may aid in recalling, an adequate picture of
either the wealth or the beauty of animal life. Fortunately
for those who visit London (and who nowadays does not ?),
we have, in our national collection in South Kensington,
the means of getting some insight into the wealth of life.

N

178 Animal Life and Intelligence.

And much is being done there to aid the imagination and
to facilitate study for those who are not professed students.
Many of the birds are now to be seen set in their natural
surroundings, with their life-history illustrated. Our
frontispiece is taken from one of these cases. And this
admirable system will, no doubt, so far as space permits,
be extended ; and, perhaps, dramatic incidents may be
introduced, like those (notably in the life of heron and
hawk) which form so marked a feature in the little museum
at Exeter. Anything which leads us to understand the life
of animals, and to go forth and study it for ourselves, has
an educational value.

In our National Museum, again, much is being wisely
done to illustrate the diversity and variety of structure
and the principles that underlie them. Observe, as you
enter the central hall, the case containing stuffed specimens
of ruffs (Machetes pugnax). Among the young autumn
birds there is not much difference between males and
females, the male being distinguished chiefly by its some-
what larger size. Nor do the old birds, male and female,
differ much during the winter months. But in pairing-
time, May and June, the females are somewhat richer in
colour ; while the males not only don the ruff to which the
bird owes its popular name, but develop striking colour-
tints. Among different individuals it will be seen that the
colour-variation is tolerably wide ; but the same individual
keeps strictly, we are told, in successive seasons, to the
same summer dress. Note, next, in a bay to the right,
the great variety of form, ornamentation, and colouring
among the molluscan shells there exhibited. Observe that
the rich colours are often hidden during life by the dull
epidermis. Half an hour's attentive study of these varied
molluscan forms will give a better idea of the beauty and
diversity of these life-products than pages of mere de-
scription.

Pass on, too, to note, in a further bay to the right, the
extraordinary modifications of the antenna, or feeler, in
insects. There is the long, whip-like form in the locust ;

Organic Evolution. 179

the clubbed whip in the ant-lion and the butterfly; the
feathered form in certain moths and flies ; the hooked form
characteristic of the sphinx-moths ; the many-leaf form
in the lamellicorn beetles, like the cockchafer; and the
feathered plate of other beetles. Equally wonderful are
the diverse developments of the mouth-organs of insects,
the spiral tube of the butterfly or moth, the strong jaws of
the great beetles, the lancets of the gnat, the sucking-disc
of the fly, — all of them special modifications of the same
set of structures. Then, in the same bay, note some of
the striking differences between the males and females
of certain insects. In some there is an extraordinary
difference in size (e.g. the locust Xiphocera, and the moth
Attacus) ; in others, like the stag-beetle, it is the size of
the jaws that distinguishes the males ; in others, again,
the most notable differences are in the length, development,
or complexity of the antennae, or feelers ; in some beetles
the males have great horns on the head or thorax ; while
in many butterflies it is in richness of colour that the
difference chiefly lies — the brilliant green of the Ornithoptera
there exhibited contrasting strongly with the sober brown
of his larger mate.

The fact that the special characteristics of the male,
which we have seen to be variable in the ruff, are also
variable among insects, is well exemplified in the case of
the stag-beetle, in some males of which the mandibles are
far larger than in others. This is shown in Fig. 22, which
is copied from the series displayed in the British Museum,
by the kind permission of Professor Flower.

Crossing the hall to where the vertebrate structures are
displayed, the development of hair, of feathers, of teeth,
the modifications of the skull and of legs, wings, and fins
are being exemplified. Note here and elsewhere the special
adaptations of structure, of which we may select two
examples. The first is that seen in the Balistes, or trigger-
fish. The anterior dorsal fin is reduced to three spines, of
which that which lies in front is a specially modified
weapon of defence, while that which follows it is the so-

180 Animal Life and Intelligence.

Organic Evolution. 181

called trigger. These two are so hinged to the underlying
interspinous bones and so related to each other that, when
once the defensive spine in front is erected, it cannot be
forced down until the trigger is lowered. The second
example of special adaptation is well displayed in specimens
of the mud-tortoise Trionyx. Between the last vertebra
of the neck and the first fixed vertebra of the dorsal series
is a beautiful hinge-joint, enabling the neck to be bent
back, S-fashion, when the creature withdraws its head
within the carapace. These are only one or two particular
instances of what any one who will visit the National
Museum may see for himself admirably displayed and
illustrated.

No one can, one would suppose, pass through the
galleries in Cromwell Eoad and remain quite insensible to
the beauties of animal life. Beauty of form and beauty of
colour are conspicuously combined in many species of birds
and insects. And much of this colour-beauty and splendid
iridescence is known to be due to minute scales, to thin
films of air or fluid, and to microscopically fine lines
developed upon scales or feathers. But there is one phase
of beauty which cannot be exhibited in the museum — the
beauty that comes of life as opposed to death. For this
we must go out into the free air of nature, where the
animals not only have lived, but are still instinct with the
glow of life, and where the silence of the museum galleries
is replaced by the song of birds and the hum of insect-
wings.

How have this wealth, this diversity, this beauty, this
manifold activity, which we summarize under the term
" animal life," been produced ?

If we answer this question hi a word — the word " evolu-
tion " * — we must remember that this word merely ex-
presses our belief in a general fact; and we must not

* It is beyond the scope of this book to give the evidences of evolution.
Such evidence from embryology, from distribution, and from palaeontology,
is now abundant. For palseontological evidence, see Nicholson's " Manual
of Palaeontology," 3rd edit., especially the second volume on " Vertebrates,"
by E. Lydekker.

1 82 Animal Life and Intelligence.

forget that many questions remain behind, all centering
round that little question, to which an adequate answer is
so difficult to give, the question — How ? Reduced to its
simplest expression, the doctrine of evolution merely states
that the animal world as it exists to-day is naturally
developed out of the animal world as it existed yesterday,
and will in turn develop into the animal world as it shall
exist to-morrow. This is the central belief of the evolu-
tionist. No matter what moment in the past history of
life you select, the life at that moment was in the act of
insensibly passing from the previous towards a future con-
dition. Then at once arises the question — Does life remain
the same yesterday, to-day, and to-morrow ? A thousand
indubitable facts at once make answer — No ! Underlying
the law of continuity there is a law of change. Life to-day
is not what it was yesterday, nor will it be to-morrow the
same as to-day. What, then, is the nature of this change ?
If it be replied that the change must be either for the
better or the worse, we shall have to answer the further
question — Better or worse in what respects ?

Let us narrow our view from the contemplation of life
as a whole to the more particular consideration of an
organism as one of its constituent units. The individual
life of that organism depends on (some would say consists
in) its ceaseless adaptation to surrounding circumstances.
The circumstances remaining the same, or only varying
within constant limits, the adaptation may be more or less
perfect. A change in the direction of more perfect adapta-
tion will be a change for the better, a tendency to less
perfect adaptation will be a change for the worse.

But the relation of an organism to its circumstances or
environment is itself subject to change. The environment
itself may alter, or the organism may be brought into relation
with a new environment. We have to consider not only
the changes in an organism in the direction of more or
less perfect adaptation to its environment, but also changes
in the environment. These changes are in the direction
of increased simplicity or of increased complexity. So

Organic Evolution. 183

that we may say that the modification of life is in the
direction of more or of less complete adaptation to simpler
or to more complex conditions. Where the adaptation
advances to more complex conditions, we speak of elabora-
tion ; where it retrogrades to less complex conditions, we
speak of degeneration ; but both fall under the head of
evolution in its more general sense. Viewed as a whole,
there can be little doubt that the general tendency of
evolution is towards more complete adaptation to more
diverse and complex environment. And this tendency is
accompanied by a general increase of differentiation and
of integration ; of differentiation whereby the constituent
elements of life, whether cells, tissues, organs, organisms,
or groups of organisms, become progressively more
specialized and more different from one another ; of
integration whereby these elements become progressively
more interdependent one on the other. We may con-
veniently sum up the tendency towards more perfect
adaptation to more complex circumstances in the word
progress; the tendency to differentiation in the word
individuality; and the tendency to integration in the
word association.

Nobody now doubts the propositions thus briefly sum-
marized, and it is therefore unnecessary to bring forward
evidence in their favour.

We may pass, then, to the question — How ? Evolution
being continuity, associated with change, tending in certain
directions, and accompanied by certain processes, how has
it been effected ? What are its methods ?

' L/

Natural Selection.

Natural selection claims a foremost place. We have
already devoted a chapter to its consideration. Animals
vary ; more are born than can survive to procreate their
kind ; hence a struggle for existence, in which the weaker
and less adapted are eliminated, the stronger and better
adapted surviving to continue the race.

184 Animal Life and Intelligence.

It is scarcely possible to over-estimate what Darwin's
labour and genius have done for the study of animal life.
Through Darwin's informing spirit, biology has become a
science. But now we must be on our guard. So long as
natural selection was whining its way to acceptance, every
application of the theory had to be made with caution, and
was subjected to keen, if sometimes ignorant, criticism.
Now there is, perhaps, some danger lest it should suffer
the Nemesis of triumphant creeds, and be used blindly as
a magic formula.

First, we should be careful not to use the phrase, " of
advantage to the species," vaguely and indefinitely, but
should in all cases endeavour clearly to indicate wherein
lies the particular advantage, and how its possession
enables the organism to escape elimination ; next, we must
remember that the advantage must be immediate and
present, prospective advantage being, of course, inoperative ;
then we must endeavour to show that the advantage is
really sufficient to decide the question of elimination or
non-elimination ; lastly, we must distinguish between
indiscriminate and differential destruction, between mere
numerical reduction by death or otherwise and selective
elimination.

(1) In illustration of the first point, we may select a
passage from the writings of even so great a biologist as
Professor Weismann. As is well known, Professor Weis-
mann believes that senility and death are no part of the
natural heritage of animal life, but have been introduced
among the metazoa on utilitarian grounds. In his earlier
papers, he attributed the introduction of death, and the
tissue -degeneration that precedes it, to the direct action of
natural selection.* More lately, he attributes it to the
cessation of selection. f Concerning this later view, we
shall have somewhat to say presently ; we may now con-
sider the former as an example of too indefinite a use of
such phrases as "of advantage to the species." " Worn-
out individuals," says Professor Weismann, "are not only

* Weismann, " Essays on Heredity," p. 24. t Ibid. p. 140.

Organic Evolution. 185

valueless to the species, but they are even harmful, for
they take the places of those which are sound. Hence, by
the operation of natural selection, the life of our hypo-
thetically immortal individual would be shortened by the
amount which was useless to the species. It would be
reduced to a length which would afford the most favourable
conditions of existence of as large a number as possible of
vigorous individuals at the same time." This may be so,
but, as it stands, the modus operandi is not given, and is
not obvious. We start with a hypothetically immortal
metazoon. Barring accidents, it will go on existing in-
definitely. But you cannot bar accidents for an indefinite
time; hence, the longer the individual lives, the more
defective and crippled it becomes. There is neither natural
decay nor natural death here. The organism is gradually
crippled through accident and injury. But the crippled
individuals are harmful to the species, because they take
the places of those which are sound. Therefore, says
Professor Weismann, natural decay and death step in to
take them off before they have time to become cripples.
Now, the point I wish to notice is that there is no definite
statement how or why natural decrepitude should thus
be introduced. We must remember that it is not until a
late stage in evolution that, through the association of its
members, groups of organisms compete with other groups.
In the earlier stages, when we must suppose decrepitude
and death to arise on Professor Weismann's hypothesis, the
law of the struggle for existence is — each for himself
against all. The question, therefore, is — What advantage
to the individual is there in natural decay and death to
enable it, through the possession of these attributes, to
escape elimination ? Surely none as such. At the same
time, it is quite conceivable that natural decay and death
may be the penalty the individual has to pay for increased
strength and vitality in the early stages of life. This,
probably, was Professor Weismann's meaning. But, if so,
it would surely have been better to state the matter in
such a way as to lay the chief stress on the really important

1 86 Animal Life and Intelligence.

feature, and to say that, through natural selection, those
individuals have survived which exhibited predominant
strength and vitality for a shortened period, even at the
expense of natural decay and death. The increased life-
power, not the seeds of decay and death, was that which
natural selection picked out for survival, or rather that
which elimination allowed to survive.

In such ways — a short life with heightened activity
being of advantage to some forms, a more prolonged
existence at a lower level of vitality being essential to
others — natural selection may have determined in some
degree the relative longevity of different organisms. That
it caused the introduction of senility as a preparation for
death is a less tenable hypothesis.

And here we may note, in passing, that in using the
phrase, "of advantage to the race or species," we must
steadily bear in mind the fact that it is with individuals
that the process of elimination deals. In the individual it
is that every modification must make good its claim to
existence and transmission. Where the principle of asso-
ciation for mutual benefit obtains, as in the case of social
insects, it is still the individual that must resist elimina-
tion. Self-sacrifice, whether conscious or unconscious,
must not be carried so far as to lead to the elimination of
the self-sacrificing individual, for in this event it cannot
but defeat its own ends. Within these limits, self-sacrifice
is of advantage, as in the case of parental self-sacrifice, in
that it enables certain other individuals to escape elimina-
tion. We should endeavour, then, not to use the phrase,
" of advantage to the species," vaguely and indefinitely, but
to indicate in what particular ways certain individuals are
to be so advantaged as to escape the Nemesis of elimination.

(2) The second point that I mentioned above scarcely
needs exemplification. That the advantage which enables
an organism to escape elimination must be present and
existent, not merely prospective, is obvious. Still, the
mistake is sometimes made. I have heard it stated that
feathers were evolved for the sake of flight. But clearly,

Organic Evolution. 187

unless the wing sprang into existence already sufficiently
developed for flight, this would be impossible. The same
is true of the first stages of many structures which could
not be of service for the purpose and use to which they
were subsequently turned. Not impossibly, the earliest
"wings" were for diving, and flight was, so to speak, an
after-thought. Undoubtedly, structures which have been
fostered under the wing of one form of advantage have
been subsequently applied to new purposes, and fostered
through new modes of adaptation. Teeth, for example, are
probably modified scales, such as are found in the thorn-
back skate. But the early development of these scales
could have had no reference to their future application to
purposes subservient to alimentation.

Again, such and such a structure is sometimes spoken
of as a " prevision against emergencies." In his interest-
ing and valuable work on " The Colours of Animals,"
for example, Mr. E. B. Poulton says, "Dimorphism [in
the larvae of butterflies and moths] is also valuable in
another way : the widening range of a species may carry it
into countries in which one of its forms may be especially
well concealed, while in other countries the other form may
be more protected. Thus a dimorphic form is more fully
provided against emergencies than one with only a single
form." And after giving, as an example, the fact that the
convolvulus hawk-moth has a browner and a greener form
of caterpillar, of which the browner is more prevalent
under European conditions, and the greener under those
which obtain in the Canary Islands, Mr. Poulton adds,
" This result appears to have been brought about by the
ordinary operation of natural selection, leading to the
extermination of the less-protected variety." Now, I do
not mean for one moment to imply that so careful and able
a naturalist as Mr. Poulton believes that any character has
been evolved through natural selection in prevision for
future emergencies. But I do think that his statement is
open to this criticism.

(3) It is sometimes said, in bold metaphor, that natural

1 88 Animal Life and Intelligence.

selection is constantly on the watch to select any modifica-
tion, however slight, which is of advantage to the species.
And it is true that elimination is ceaselessly operative.
But it is equally certain that the advantage must be of
sufficient value to decide the question whether its possessor
should be eliminated or should escape elimination. If it
does not reach this value, Natural Selection, watch she
never so carefully, can make no use of it. Elimination
need not, however, be to the death ; exclusion from any
share in continuing the species is sufficient. To breed or
not to breed, that is the question. Any advantage affect-
ing this essential life-function will at once catch the eye of
a vigilant natural selection. But it must be of sufficient
magnitude for the machinery of natural selection to deal
with. That machinery is the elimination of a certain
proportion of the individuals which are born. Which shall
be eliminated, and which shall survive, depends entirely on
the way in which the individuals themselves come out in
life's competitive examination. The manner in which that
examination is conducted is often rude and coarse, too rough-
and-ready to weigh minute and infinitesimal advantages.

What must be the value of a favourable or advantageous
modification to decide the question of elimination, to make
it an available advantage, must remain a matter of conjec-
ture. It will vary with the nature and the pressure of the
eliminative process. And perhaps it is scarcely too much
to say that, at present, we have not observational grounds
on which to base a reliable estimate in a single instance.
We must not let our conviction of its truth and justice
blind us to the fact that natural selection is a logical
inference rather than a matter of direct observation. A
hundred are born, and two survive ; the ninety-eight are
eliminated in the struggle for existence ; we may therefore
infer that the two escaped elimination in virtue of their
possession of certain advantageous characters. There is
no flaw in the logic that has thus convinced the world that
natural selection is a factor in evolution. But by what
percentage of elimination-marks the second of the two

Organic Evolution. 189

successful candidates beats the senior on the list of failures
we do not know. We can only see that, on the hypothesis
of natural selection, it must have been sufficiently ap-
preciable to determine success or failure.

(4) And then, to come to our fourth point, we must
remember that, apart from the differentiating process of
elimination, there is much fortuitous destruction. A
hundred are born, and but two survive. But of the ninety-
eight which die, and fail to procreate, how many are
eliminated, how many are fortuitously destroyed, we do
not find it easy to say. And indiscriminate destruction
gets rid of good, bad, and indifferent alike. It is a mistake
to say that of the hundred born the two survivors are
necessarily the very best of the lot. It is quite possible
that indiscriminate destruction got rid of ninety of all sorts,
and left only ten subject to the action of a true elimina-
tion. " In the majority of birds," says Professor Weis-
mann, " the egg, as soon as it is laid, becomes exposed to
the attacks of enemies; martens and weasels, cats and
owls, buzzards and crows, are all on the look out for it.
At a later period, the same enemies destroy numbers of the
helpless young, and in winter many succumb in the struggle
against cold and hunger, or to the numerous dangers which
attend migration over land and sea — dangers which decimate
the young birds." There is here, first, a certain amount
of fortuitous destruction ; secondly, some selection applied
to the eggs ; thirdly, a selection among the very young
nestlings ; and, fourthly, a selection among the young
migratory birds. What may be the proportion of elimina-
tion to destruction at each stage it is difficult to say.
Among the eggs and fry of fishes fortuitous destruction
probably very far outbalances the truly differentiating
process.

Panmixia and Disuse.

We may now pass on to consider shortly some of the
phenomena of degeneration, and the dwindling or dis-
appearance of structures which are no longer of use.

190 Animal Life and Intelligence.

Many zoologists believe, or until lately have believed,
that disuse is itself a factor in the process. Just as the
well-exercised muscle is strengthened, so is the neglected
muscle rendered weak and flabby. Until recently it was
generally held that the effects of such use or disuse are
inherited. But now Professor Weismann has taught us,
if not to doubt ourselves, at least to admit that doubt is
permissible. On the older view, the gradual dwindling of
unused parts was readily comprehensible. But now, if Pro-
fessor Weismann is right, we must seek another explanation
of the facts ; and, in any case, we may be led to recognize
other factors (than that of disuse alone) in the process.

Professor Weismann regards panmixia, or free inter-
crossing, when the preserving influence of natural selection
is suspended, as the efficient cause of a reduction or de-
terioration in the organ concerned. And Mr. Romanes
had, in England, drawn attention to the fact that the
" cessation of natural selection " would lead to some
dwindling of the organ concerned, since it was no longer
kept up to standard. In illustration of his panmixia, Pro-
fessor Weismann says, "A goose or duck must possess
strong powers of flight in the natural state, but such
powers are no longer necessary for obtaining food when it
is brought into the poultry-yard, so that a rigid selection
of individuals with well-developed wings at once ceases
among its descendants. Hence, in the course of genera-
tions, a deterioration of the organs of flight must neces-
sarily ensue, and the other members and organs of the
bird will be sensibly affected." * And, again, " As at each
stage of retrogressive transformation individual fluctuations
always occur, a continued decline from the original degree
of development will inevitably, although very slowly, take
place, until the last remnant finally disappears." f Now,
I think it can be shown that panmixia, or the cessation of
selection, alone cannot affect much reduction. It can only

* Weismann, " Essays on Heredity," p. 90.

t Ibid. p. 292. See also a discussion in Nature, in which Mr. Romanes
and Professor Ray Lankester took part, beginning vol. xli. p. 437.

Organic Evolution.

191

affect a reduction from the " survival-mean " to the " birth-
mean." This was referred to in the chapter on "Heredity
and the Origin of Variations," but may be again indicated.
Suppose the number of births among wild ducks be repre-
sented by the number nine, of which six are eliminated
through imperfections in the organs of flight. Let us
place the nine in order of merit in this respect, as is done
in the table on p. 172. The average wing-power of the
nine will be found in No. 5, there being four ducks with
superior wing-power (1 — 4), and four with inferior wing-
power (6 — 9). The birth-mean will therefore be at the
level of No. 5, as indicated to the left of the table. But if
six ducks with the poorest wings be eliminated, only three
survive. The average wing-power will now be found in
No. 2, one duck being superior and one inferior to it
in this respect. It is clear that this survival-mean
is at a level of higher excellence than the birth-mean.
Now, when the ducks are placed in a poultry-yard,
selection in the matter of flight ceases, and, since all
nine ducks survive, the survival-mean drops to the birth-
mean. We may variously estimate this retrogression ; but
it cannot be a large percentage — I should suppose, in the
case under consideration, one or two per cent, at most.
But Professor Weismann says, " A continued decline from
the original degree of development must inevitably take
place." It is not evident why such decline should continue.
If variations continue in the same proportion as before,
the birth-mean will be preserved, since there are as many
positive or favourable variations above the mean as there
are negative or unfavourable variations below the mean.
A continuous decline must result from a preponderance of
negative over positive variations, and for this some other
principle, such as atavism, or reversion to ancestral
characters, must be called in. But in the case of so long-
established and stable an organ as that of flight, fixed
and rendered constant through so many generations, it is
hardly probable that reversion would be an important
factor. Mr. Galton has calculated that among human-

1 92 Animal Life and Intelligence.

folk the offspring inherits one-fourth from each parent,
one-sixteenth from each grandparent, leaving one-fourth
to be contributed by more remote ancestors. There is no
doubt, however, that among domesticated animals rever-
sion occurs to characters which have been lost for many
generations. But we should probably have to go a very
long way back in the ancestry of wild ducks for any marked
diminution in wing-power. It must be remembered that,
in the case of the artificial selection of domesticated
animals, man has been working against and not with the
stream of ancestral tendency. Reversion in their case is
towards a standard which was long maintained and had
become normal before man's interference. Reversion in
domesticated ducks should therefore be towards the greater
wing-power of their normal ancestry before domestication,
not in the direction of lessened wing-power and diminished
wing- structure. The whole question of reversion is full of
interest, and needs further investigation.

In the dwindling of disused structures, Mr. Romanes
has suggested " failure of heredity " as an efficient cause.
I find it difficult, however, to distinguish this failure of
heredity from the effects of disuse. To what other cause
is the failure of heredity due? If natural selection has
intervened to hasten this failure, this can only be because
the failure is advantageous, since it permits the growth-force
to be applied more advantageously elsewhere. And this
involves a different principle. Even so it is difficult to
exclude the possibility (to put it no stronger) that the
diversion of growth-force from a less useful to a more
useful organ is in part due to the use of the one and the
disuse of the other. • But of disuse Mr. Romanes says,
"There is the gravest possible doubt lying against the.
supposition that any really inherited decrease is due to
the inherited effects of disuse." We may fairly ask Mr.
Romanes, therefore, to explain to what cause the failure of
heredity is due. In any case, Professor Weismann and
his school are not likely to accept this failure of heredity
as an efficient factor in the process. Nor is Professor

Organic Evohition. 193

Weismann likely to fall back upon any innate tendency to
degeneration. Unless, therefore, some cause be shown
why the negative variations should be prepotent over the
positive variations, we must, I think, allow that unaided
panmixia cannot affect any great amount of reduction.

In this connection we may notice Professor Weismann's
newer view of the introduction of bodily mortality. He
says, " The problem is very easily solved if we seek
assistance from the principle of panmixia. As soon as
natural selection ceases to operate upon any character,
structural or functional, it begins to disappear. As soon,
therefore, as the immortality of somatic [body-] cells became
useless, they would begin to lose this attribute." * Even
granting that panmixia could continuously reduce the size
of ducks' wings, it is not easy to see how it could get rid of
immortality. The essence of the idea of panmixia is that,
when the natural selection which has raised an organ to
a high functional level, and sustains it there, ceases or is
suspended, the organ drops back from its high level. But
on Professor Weismann's hypothesis, immortality has
neither been produced nor is it sustained by natural selec-
tion. How, therefore, the cessation of selection can cause
the disappearance of immortality — a character with which
natural selection has had nothing whatever to do — Pro-
fessor Weismann does not explain. He seems to be using
"panmixia" in the same vague way that, in his previous
explanation, he used " natural selection."

If panmixia alone cannot, to any very large extent,
reduce an organ no longer sustained by natural selection,
to what efficient cause are we to look ? Mr. Eomanes has
drawn attention to the reversal of selection as distinguished
from its mere cessation. When an organ is being improved
or sustained by selection, elimination weeds out all those
which have the organ in an ill-developed form. Under a
reversal of selection, elimination will weed out all those
which possess the organ well developed. In burrowing
animals, the eyes may have been reduced in size, or even

* Weismann, " Essay on Heredity," p. 140.

O

194 Animal Life and Intelligence.

buried beneath the skin, through a reversal of selection.
The tuco-tuco (Ctenomys), a burrowing rodent of South
America, is frequently blind. One which Darwin kept
alive was in this condition, the immediate cause being
inflammation of the nictitating membrane. "As frequent
inflammation of the eyes," says Darwin, "must be in-
jurious to any animal, and as eyes are certainly not
necessary to animals having subterranean habits, a reduc-
tion in their size, with the adhesion of the eyelids and
growth of fur over them, might in such cases be an
advantage ; and, if so, natural selection would aid the effect
of disuse.* Granting that the inflammation of the eyes is
a sufficient disadvantage to lead to elimination, such cases
may be assigned to the effects of a reversal of selection.

Perhaps the best instances of the reversal of selection
are to be found in the insects of wind-swept islands, in
which, as we have already seen (p. 81), the power of flight
has been gradually reduced or even done away with.
Such instances are, however, exceptional. And one can
hardly suppose that such reversal of selection can be very
far-reaching in its effects, at least, through any direct
disadvantage from the presence of the organ. One can
hardly suppose that the presence of an eye in a cave-
dwelling fisht could be of such direct disadvantage as to
lead to the elimination of those members which still possess
this structure.

But may it not be of indirect disadvantage ? May not
this structure be absorbing nutriment which would be more
advantageously utilized elsewhere ? This is Darwin's
principle of economy. Granting its occurrence, is it effec-
tive ? We may put the matter in this way : The Crustacea
which have been swept into a dark cave may be divided
into three classes so far as fortuitous variations of eyes

* " Origin of Species," p. 110.

f With regard to bliud cave-fish, Professor Ray Lankester has suggested
that some selection has been effected. Those animals whose sight-sensitive-
Bess enabled them to detect a glimmer of light would escape to the exterior,
leaving those with congenitally weak sight to remain and procreate in the
darkness of the cave.

Organic Evolution. 195

and antennae are concerned. First, those which preserve
eyes and antennas in the original absolute and relative
proportion and value ; secondly, those in which, while the
eyes remain the same, the antennas are longer and more
sensitive ; thirdly, those in which, while the antennas are
longer and more sensitive, the eyes are reduced in size and
elaboration. According to the principle of economy, the
third class have sufficient advantage over the first and
second to enable them to survive and escape the elimina-
tion which removes those with fully developed eyes. It
may be so. We cannot estimate the available advantage
with sufficient accuracy to deny it. But we may fairly
suppose that, in general, it is only where the useless organ
in question is of relatively large size, and where nutriment
is deficient, that economy of growth is an important factor.

We may here note the case of the hermit crab as one
which exemplifies degeneration through the reversal of
natural selection. This animal, as is well known, adopts
an empty whelk-shell or other gasteropod shell as its own.
The hinder part of the body which is thus thrust into the
shell loses its protective armour, and is quite soft. Pro-
fessor WTeismann seems to regard this loss of the hardened
cuticle as due entirely to panmixia. If what has been
urged above has weight, this explanation cannot be correct.
No amount of promiscuous interbreeding of crabs could
reduce the cuticle to a level indefinitely below that of any
of the interbreeding individuals. But it is clear that an
armour-sheathed "tail" would be exceedingly ill adapted
to thrusting into a whelk-shell. Hence there would, by
natural selection, be an adaptation to new needs, involving
not the higher development of cuticle, but the reverse. So
far as the cuticle is concerned, it is a case of reversed
selection. Whether this reversal alone will adequately
account for the facts is another matter.

Mr. Herbert Spencer has made a number of observa-
tions and measurements of the jaws of pet dogs, which lead
him to conclude that there has been a reduction in size
and muscular power due to disuse. The creatures being

196 Animal Life and Intelligence.

fed on sops, have no need to use to any large extent the
jaw-muscles. In this case, he argues, the principle of
economy is not likely to be operative, since the pampered
pet habitually overeats, and has therefore abundant nutri-
ment and to spare to keep up the jaws. It is possible,
however, that artificial selection has here been a factor.
There may have been a competition among the old ladies
who keep such pets to secure the dear little dog that never
bites, while the nasty little wretch that does occasionally
use his jaws for illegitimate purposes may have been
speedily eliminated. Pet dogs are, moreover, a pampered,
degenerate, and for the most part unhealthy race, often
deteriorated by continued in-breeding, so that we must not
build too much on Mr. Spencer's observations, interesting
as they undoubtedly are.

There is one feature about the reduction of organs
which must not be lost sight of. They are very apt to
persist for a long time as remnants or vestiges. The
pineal gland is the vestigial remnant of a structure con-
nected with the primitive, median, or pineal eye. The
whalebone whales and the duck-bill platypus have teeth
which never cut the gum and are of no functional value.
With regard to these, it may be asked — If disuse leads to
the reduction of unused structures, how comes it that
it has not altogether swept away these quite valueless
structures ? In considering this point, we must notice the
unfortunate and misleading way in which disuse is spoken
of as if it were a positive determinant, instead of the mere
absence of free and full and healthy exercise. Few will
question the fact that in the individual, if an organ is to
be kept up to its full standard of perfection, it must be
healthily and moderately exercised ; and that, if not so
exercised, it will not only cease to increase in size, but will
tend to degenerate. The healthy, functionally valuable
tissue passes into the condition of degenerate, comparatively
useless tissue. Now, those who hold that the inheritance
of functional modifications is still a tenable hypothesis,
carry on into the history of the race that which they find

Organic Evolution.

197

to hold good in the history of the individual. They believe
that, in the race, the continued functional activity of an
organ is necessary for the maintenance of the integrity
and perfection of its structure, and that, if not so exercised,
the organ will inevitably tend to dwindle to embryonic
proportions and to degenerate. The healthy, functionally
valuable tissue passes at last into the condition of
degenerate, comparatively useless tissue. The force of
heredity will long lead to the production in the embryo
of the structure which, in the ancestral days of healthy
exercise, was to be of service to the organism. At this
stage of life the conditions have not changed. The
degeneration sets in at that period when the ancestral use1
is persistently denied. There is no reason why " disuse "
should in all cases remove all remnants of a structure ;
but if the presence of the degenerate tissue is a source of
danger to the organism which possesses it, that organism
will be eliminated, and those (1) which possess it in an
inert, harmless form, or (2) in which it is absent, will
survive. Thus natural selection (which will fall under Mr.
Eomanes's reversed selection) will step in — will in some
cases reduce the organ to a harmless and degenerate
rudiment, and in others remove the last vestiges of the
organ.

On the whole, even taking into consideration the effects
of panmixia, of reversed selection, and of the principle of
economy, the reduction of organs is difficult to explain,
unless we call into play " disuse " as a co-operating factor.

Sexual Selection, or Preferential Mating.

It is well known that, in addition to and apart from
the primary sexual differences in animals, there are certain
secondary characters by which the males, or occasionally
the females, are conspicuous. The antlers of stags, the
tail of the peacock, the splendid plumes of the male bird of
paradise, the horns or pouches of lizards, the brilliant
frilled crest of the newt, the gay colours of male stickle-

198 Animal Life and Intelligence.

backs, the metallic hues of male butterflies, and the large
horns or antennae of other insects, — these and many other
examples which will at once occur to the reader are
illustrations of the fact.

As a contribution towards the explanation of this order
of phenomena, Darwin brought forward his hypothesis of
sexual selection, of which there are two modes. In the
first place, the males struggle together for their mates ; in
this struggle the weakest are eliminated ; those possessed
of the most efficient weapons of offence and defence escape
elimination. In the second place, the females are repre-
sented as exercising individual choice, and selecting (in
the true sense of the word) those mates whose bright
colours, clear voices, or general strength and vigour render
them most pleasing and attractive. For this mode I shall
employ the term "preferential mating." Combining these
two in his summary, Darwin says, " It has been shown
that the largest number of vigorous offspring will be reared
from the pairing of the strongest and best-formed males,
victorious in contests over other males, with the most
vigorous and best-nourished females, which are the first
to breed in the spring. If such females select the more
attractive and, at the same time, vigorous males, they will
rear a larger number of offspring than the retarded females,
which must pair with the less vigorous and less attractive
males. So it will be if the more vigorous males select
the more attractive and, at the same time, healthy and
vigorous females ; and this will especially hold good if the
male defends the female, and aids in providing food for
the young. The advantage thus gained by the more
vigorous pairs in rearing a larger number of offspring has
apparently sufficed to render sexual selection efficient."*

With regard to the first of the two modes, little need
be said. There can be no question that there are both
elimination by battle and elimination by competition in
the struggle for mates. It is well known that the emperor
moth discovers his mate by his keen sense of smell residing

* Darwin, " Descent of Man," pt. ii. chap. viii.

Organic Evolution. 199

probably in the large, branching antennae. There can
be little doubt that, if an individual is deficient in this
sense, or misinterprets the direction in which the virgin
female lies, he will be unsuccessful in the competition for
mates ; he will be eliminated from procreation. And it is
a familiar observation of the poultry-yard that the law of
battle soon determines which among the cock birds shall
procreate their kind. The law of battle for mates is, in-
deed, an established fact among many animals, especially
those which are polygamous, and the elimination of the
unfit in this respect is a logical necessity.

It is when we come to the second of the two' modes,
that which involves selection proper, that we find differences
of opinion among naturalists.

Darwin, as we have seen, suggested that those secondary
sexual characters which can be of no value in aiding their
possessor to escape elimination by combat result from the
preferential choice of the female, the female herself remain-
ing comparatively unaffected. But Mr. Wallace made an
exceedingly valuable suggestion with regard to these com-
paratively dull colours of the female. He pointed out that
conspicuousness (unless, as we have seen, accompanied by
some protective character, such as a sting or a bitter taste)
increased the risk of elimination by enemies. Now, the
males, since they are generally the stronger, more active,
and more pugnacious, could better afford to run this risk
than their mates. They could to some extent take care
of themselves. Moreover, when impregnation was once
effected, the male's business in procreation was over. Not
so the female ; she had to bear the young or to lay the
eggs, often to foster or nourish her offspring. Not only
were her risks greater, but they extended over a far longer
period of time. Hence, according to Mr. Wallace, the dull
tints of the females, as compared with those of the males,
are due to natural selection eliminating the conspicuous
females in far greater proportion than the gaudy males.

There is clearly no reason why this view should not be
combined with Darwin's ; preferential mating being one

2oc Animal Life and Intelligence.

factor, natural elimination being another factor; both
being operative at the same time, and each contributing to
that marked differentiation of male and female which we
find to prevail in certain classes of the animal kingdom.

But Mr. Wallace will not accept this compromise. He
rejects preferential mating altogether, or, in any case,
denies that through its agency secondary sexual characters
have been developed. He admits, of course, the striking
and beautiful nature of some of these characters ; he
admits that the male in courtship takes elaborate pains to
display all his finery before his would-be mate ; he admits
that the " female birds may be charmed or excited by the
fine display of plumage by the males ; " but he concludes
that " there is no proof whatever that slight differences in
that display have any effect in determining their choice of
a partner."*

How, then, does Mr. Wallace himself suppose that
these secondary sexual characters have arisen ? His
answer is that " ornament is the natural outcome and
direct product of superabundant health and vigour," and
is "due to the general laws of growth and development."!
At which one rubs one's eyes and looks to the title-page to
see that Mr. Wallace's name is really there, and not that
of Professor Mivart or the Duke of Argyll. For, if the
plumage of the argus pheasant and the bird of paradise
is due to the general laws of growth and development,
why not the whole animal ? If Darwin's sexual selection
is to be thus superseded, why not Messrs. Darwin and
Wallace's natural selection ?

Must we not confess that Mr. Wallace, for whose genius
I have the profoundest admiration, has here allowed him-
self to confound together the question of origin and the
question of guidance or direction ? Natural selection by
elimination and sexual selection through preferential

* " Darwinism," chap. x.

t "Darwinism," p. 295. Messrs. Geddes and Thomson, " Tlie Evolution
of Sex," p. 28, also contend that "combative energy and sexual beauty rise
part passu with male katabolism."

Organic Evolution. 201

mating are, supposing them to be vera causa, guiding or
selecting agencies. Given the variations, however caused,
these agencies will deal with them, eliminating some,
selecting others, with the ultimate result that those
specially fitted for their place in nature will survive.
Neither the one nor the other deals with the origin of
variations. That is a wholly different matter, and con-
stitutes the leading biological problem of our day. Mr.
Wallace's suggestion is one which concerns the origin of
variations, and as such is worthy of careful consideration.
It does not touch the question of their guidance into certain
channels or the maintenance of specific standards. Con-
cerning this Mr. Wallace is silent or confesses ignorance.
"Why, in allied species," he says, "the development of
accessory plumes has taken different forms, we are unable
to say, except that it may be due to that individual
variability which has served as the starting-point for so
much of what seems to us strange in form or fantastic in
colour, both in the animal and vegetable world."* It is
clear, however, that "individual variability" cannot be
regarded as a vera causa of the maintenance of a specific
standard — a standard maintained in spite of variability.

The only directive agency (apart from that of natural
selection) to which Mr. Wallace can point is that suggested
by Mr. Alfred Tylor, in an interesting, if somewhat fanciful,
posthumous work on " Coloration in Animals and Plants,"
" namely, that diversified coloration follows the chief lines
of structure, and changes at points, such as the joints,
where function changes." But even if we admit that
coloration -bands or spots originate at such points or
along such lines — and the physiological rationale is not
altogether obvious — even if we admit that in butterflies the
spots and bands usually have reference to the form of the
wing and the arrangement of the nervures, and that in
highly coloured birds the crown of the head, the throat,
the ear-coverts, and the eyes have usually distinct tints,
still it can hardly be maintained that this affords us any

* " Darwinism," p. 293.

2O2 Animal Life and Intelligence.

adequate explanation of the specific colour-tints of the
humming-birds, or the pheasants, or the Papilionidae
among butterflies. If, as Mr. Wallace argues, the immense
tufts of golden plumage in the bird of paradise owe their
origin to the fact that they are attached just above the
point where the arteries and nerves for the supply of the
pectoral muscles leave the interior of the body, are there
no other birds in which similar arteries and nerves are
found in a similar position ? Why have these no similar
tufts ? And why, in the birds of paradise themselves, does
it require four years (for it takes so long for the feathers
of the male to come to maturity) ere these nervous and
arterial influences take effect upon the plumage ? Finally,
one would inquire how the colour is determined and held
constant in each species. The difficulty of the Tylor-
Wallace view, even as a matter of origin, is especially great
in those numerous cases in which the colour is determined
by delicate lines, thin plates, or thin films of air or fluid.*
Under natural selection, as we have seen, the develop-
ment of colour is fostered under certain conditions. The
colour is either protective, rendering the organism incon-
spicuous amid its normal surroundings, or it is of warning
value, advertising the organism as inedible or dangerous,
or, in the form of recognition-marks, it is of service in
enabling the members of a species to recognize each other.
Now, in the case of both warning colour and recognition-
marks, their efficacy depends upon the perceptual powers
of animals. Unless there be a rapidly acquired and close
association of the quality we call nastiness with the quality
we call gaudiness (though, for the animal, there is no such
isolation of these qualities as is implied in our words t),
such that the sight of the gaudy insect suggests that it
will be unpleasant to eat, the gaudiness will be of no avail.
And if there is any truth in the doctrine of mimicry, the
association is particular. It is not merely that bright

* Mr. Poulton, who takes a similar line of argument in his " Colours of
Animals," lays special stress upon the production of white (see p, 326).
t See Chapter VIII.

Organic Evolution. 203

colours are suggestive of a nasty taste. The insect-eating
birds associate nastiness especially with certain markings
and coloration — " the tawny Danais, the barred Heliconias,
the blue-black Euplceas, and the fibrous Acrceas;" and
this is proved by the fact that sweet insects mimicking
these particular forms are thereby protected.

So, too, with recognition-marks. If the bird or the
mammal have not sufficient perceptive powers to distinguish
between the often not very different recognition-marks, of
what service can they be ?

Eecognition-marks and mimicry seem, therefore, to show
that in the former case many animals, and in the latter
the insect-eating birds, mammals, lizards, and other
animals concerned, have considerable powers of perception
and association.

Among other associations are those which are at the
base of what I have termed preferential mating. We must
remember how deeply ingrained in the animal nature is
the mating instinct. We may find it difficult to distinguish
closely allied species. But the individuals of that species
are led to mate together by an impelling instinct that is so
well known as to elicit no surprise. Instinct though it be,
however, the mating individuals must recognize each other
in some way. The impulse that draws them together must
act through perceptual agency. It is not surprising, there-
fore, to find, when we come to the higher animals, that,
built upon this basis, there are well-marked mating pre-
ferences. And this, as we have before pointed out, follow-
ing Wallace, is an efficient factor in segregation. Let us,
however, hear Mr. Wallace himself in the matter.

There is, he says,* " a very powerful cause of isolation
in the mental nature — the likes and dislikes — of animals ;
and to this is probably due the fact of the rarity of hybrids
in a state of nature. The differently coloured herds of
cattle in the Falkland Islands, each of which keeps
separate, have been already mentioned. Similar facts
occur, however, among our domestic animals, and are

* " Darwinism," p. 172.

204 Animal Life and Intelligence.

well known to breeders. Professor Low, one of the greatest
authorities on our domesticated animals, says, ' The female
of the dog, when not under restraint, makes selection of
her mate, the mastiff selecting the mastiff, the terrier the
terrier, and so on.' And again, ' The merino sheep and
the heath sheep of Scotland, if two flocks are mixed together,
each will breed with its own variety.' Mr. Darwin has
collected many facts illustrating this point.* One of the
chief pigeon-fanciers in England informed him that, if
free to choose, each breed would prefer pairing with its
own kind. Among the wild horses in Paraguay those of
the same colour and size associate together ; while in
Circassia there are three races of horses which have
received special names, and which, when living a free life,
almost always refuse to mingle and cross, and will even
attack one another. In one of the Faroe Islands, not
more than half a mile in diameter, the half-wild native
black sheep do not readily mix with imported white sheep.
In the Forest of Dean and in the New Forest the dark
and pale coloured herds of fallow deer have never been
known to mingle ; and even the curious ancon sheep, of
quite modern origin, have been observed to keep together,
separating themselves from the rest of the flock when put
into enclosures with other sheep. The same rule applies
to birds, for Darwin was informed by the Kev. W. D. Fox
that his flocks of white and Chinese geese kept distinct.
This constant preference of animals for their like, even
in the case of slightly different varieties of the same
species, is evidently a fact of great importance in con-
sidering the origin of species by natural selection, since it
shows us that, so soon as a slight differentiation of form or
colour has been effected, isolation will at once arise by the
selective association of the animals themselves."

Mr. Wallace thus allows, nay, he lays no little stress
on, preferential mating, and his name is associated with
the hypothesis of recognition-marks. But he denies that
preferential mating, acting on recognition-marks, has had

* See " Animals and Plants under Domestication," vol. ii. p. 80.

Organic Evolution. 205

any effect in furthering a differentiation of form or colour.
He admits that so soon as a slight differentiation of form
or colour has been effected, segregation will arise by the
selective association of the animals themselves ; but he
does not admit that such selective association can carry
the differentiation further.

Now, it is clear that mating preferences must be either
fixed or variable. If fixed, how can differentiation occur
in the same flock or herd? And how can selective asso-
ciation be a means of isolation ? Or, granting that dif-
ferentiation has occurred, if the mating preferences are
then stereotyped, all further differentiation, so far as colour
and form are concerned, will be rendered impossible ; for
divergent modifications, not meeting the stereotyped
standard of taste, will for that reason fail to be perpetuated.
We must admit, then, that these mating preferences are
subject to variation. And now we come to the central
question with regard to sexual selection by means of
preferential mating. What guides the variation along
special lines leading to heightened beauty ? This, I take
it, is the heart and centre of Mr. Wallace's criticism of
Darwin's hypothesis. Sexual selection of preferential
mating involves a standard of taste ; that standard has
advanced from what we consider a lower to what we con-
sider a higher aesthetic level, not along one line, but along
many lines. What has guided it along these lines ?

Not as in any sense affording a direct answer to this
question, but for illustrative purposes, we may here draw
attention to what seems to be a somewhat parallel case,
namely, the development of flowers through insect agency.
In his " Origin of Species," Darwin contended that flowers
had been rendered conspicuous and beautiful in order to
attract insects, adding, " Hence we may conclude that, if
insects had not been developed on the earth, our plants
would not have been decked with beautiful flowers, but
would have produced only such poor flowers as we see on
our fir, oak, nut, and ash trees, on grasses, docks, and
nettles, which are all fertilized through the agency of the

206 Animal Life and Intelligence.

wind." " The argument in favour of this view," says Mr.
Wallace,* who quotes this passage, "is now much stronger
than when Mr. Darwin wrote ; " and he cites with approval
the following passage from Mr. Grant Allen's " Colour-
Sense : " " While man has only tilled a few level plains, a
few great river-valleys, a few peninsular mountain slopes,
leaving the vast mass of earth untouched by his hand, the
insect has spread himself over every land in a thousand
shapes, and has made the whole flowering creation sub-
servient to his daily wants. His buttercup, his dandelion,
and his meadowsweet grow thick in every English field.
His thyme clothes the hillside ; his heather purples the
bleak grey moorland. High up among the Alpine heights
his gentian spreads its lakes of blue ; amid the snows of
the Himalayas his rhododendrons gleam with crimson light.
Even the wayside pond yields him the white crowfoot and
the arrowhead, while the broad expanses of Brazilian
streams are beautified by his gorgeous water-lilies. The
insect has thus turned the whole surface of the earth into
a boundless flower-garden, which supplies him from year
to year with pollen or honey, and itself in turn gains
perpetuation by the baits that it offers to his allurement." t
Mr. Grant Allen is perfectly correct in stating that the
insect has produced all this beauty. It is the result of
insect choice, a genuine case of selection as contrasted with
elimination. And when we ask in this case, as we asked
in the case of the beautiful colours and forms of animals,
what has guided their evolution along lines which lead to
such rare beauty, we are given by Mr. Wallace himself the
answer, " The preferential choice of insects." If these
insects have been able to produce through preferential
selection all this wealth of floral beauty (not, indeed, for the
sake of the beauty, but incidentally in the practical business
of their life), there would seem to be no a priori reason why
the same class and birds and mammals should not have
been able to produce, through preferential selection, all the
wealth of animal beauty.

* " Darwinism," p. 332. f " The Colour-Sense," by Grant Allen, p. 95.

Organic Evolution. 207

It should be noted that the answer to the question is in
each case a manifestly incomplete one. For if we say that
these forms of beauty, floral and animal, have been selected
through animal preferences, there still remains behind the
question — How and why have the preferences taken these
(esthetic lines ? To which I do not see my way to a satis-
factory answer, though some suggestions in the matter will
be made in a future chapter.* At present all we can say is
this — to be conspicuous was advantageous, since it furthered
the mating of flowers and animals. To be diversely con-
spicuous was also advantageous. As Mr. Wallace says,
"It is probably to assist the insects in keeping to one
flower at a time, which is of vital importance to the per-
petuation of the species, that the flowers which bloom
intermingled at the same season are usually very distinct,
both in form and colour." f But conspicuousness is not
beauty. And the question still remains — From what source
comes this tendency to beauty ?

Leaving this question on one side, we may state the
argument in favour of sexual selection in the following
form : The generally admitted doctrine of mimicry involves
the belief that birds and other insect-eating animals have
delicate and particular perceptual powers. The generally
received doctrine of the origin of flowers involves the belief
that their diverse forms and markings result from the
selective choice of insects. There are a number of colour
and form peculiarities in animals that cannot be explained
by natural selection through elimination. There is some
evidence in favour of preferential mating or selective asso-
ciation. It is, therefore, permissible to hold, as a pro-
visional hypothesis, that just as the diverse forms of flowers
result from the preferential choice of insects, so do the
diverse secondary sexual characters of animals result, in
part at least, from the preferential choice of animals through
selective mating.

If this be admitted, then the elaborate display of their
finery by male birds, which Mr. Wallace does admit, may

* That on " The Emotions of Animals " (X.). t " Darwinism," p. 318.

208 Animal Life and Intelligence.

fairly be held to have a value which he does not admit.
For if preferential mating is a priori probable, such display
may be regarded as the outcome of this mode of selection.
At the same time, it may be freely admitted that more
observations are required. In a recent paper, " On Sexual
Selection in Spiders of the Family Attidee," * by George \V.
and Elizabeth G. Peckham, a full, not to say elaborate,
description is given of the courtship, as they regard it, of
spiders. The " love-dances " and the display of special
adornments are described in detail. And the observers,
as the result, be it remembered, of long and patient investi-
gation and systematic study, come to the conclusion that
female spiders exercise selective choice in their mates.
And courtship must be a serious matter for spiders, for if
they fail to please, they run a very serious risk of being
eaten by the object of their attentions. Some years ago I
watched, on the Cape Flats, near Capetown, the courtship
of a large spider (I do not know the species). In this case
the antics were strange, and, to me, amusing; but they
seemed to have no effect on the female spider, who merely
watched him. Once or twice she darted forward towards
him, but he, not liking, perhaps, the gleam in her eyes,
retreated hastily. Eventually she seemed to chase him off
the field.

We must remember how difficult it is to obtain really
satisfactory evidence of mating preferences in animals. In
most cases we must watch the animals undisturbed, and
very rarely can we have an opportunity of determining
whether one particular female selects her mate out of her
various suitors. We watch the courtship in this, that, or
the other case. In some we see that it is successful; in
others that it is unsuccessful. How can we be sure that
in the one case it was through fully attaining, in the other
through failing to reach, the standard of taste ? And yet
it 4s evidence of this sort that Mr. Wallace demands. After
noting the rejection by the hen of male birds which had
lost their ornamental plumage, he says, " Such cases do

* Natural History Society of Wisconsin, vol. i. (1889).

Organic Evolution. 209

not support the idea that males with the tail-feathers a
trifle longer, or the colours a trifle brighter, are generally
preferred, and that those which are only a little inferior are
as' generally rejected, — and this is what is absolutely needed
to establish the theory of the development of these plumes
by means of the choice of the female." * If Mr. Wallace
requires direct observational evidence of this kind, I do not
suppose he is likely to get any large body of it. But one
might fairly ask him what body of direct observational
evidence he has of natural selection. The fact is that
direct observational evidence is, from the nature of the
processes involved, almost impossible to produce in either
case. Natural selection is an explanation of organic
phenomena reached by a process of logical inference and
justified by its results. It is not claimed for the hypo-
thesis of selective mating that it has a higher order of
validity.

Use and Disuse.

As we have already seen, biologists are divided into two
schools, one of which maintains that the effects of use and
disuse f have been a potent factor in organic evolution ;
the other, that the effects of use and disuse are restricted to
the individual. My own opinion is that we have not a
sufficient body of carefully sifted evidence to enable us to
dogmatize on the subject, one way or the other. But, the
position of strict equilibrium being an exceedingly difficult
and som'e would have us believe an undesirable attitude
of mind, I may add that I lean to the view that use and
disuse, if persistent and long-continued, take effect, not
only on the individual, but also on the species.

It is scarcely necessary to give examples of the kind of
change which, according to the Lamarckian school, are
wrought by use and disuse. Any organ persistently used
will have a tendency, on this view, to become in successive

* " Darwinism," p. 286.

t On the negative character of disuse, see p. 196.

P

2 TO Animal Life and Intelligence.

generations more and more adapted to its functional work.
To give but one example. It is well known that certain
hoofed creatures are divisible into two groups — first, those
which, like the horse, have in each limb one large and
strong! digit armed with a solid hoof ; and, secondly, those
which, like the ox, have in each limb two large digits, so
that the hoof is cloven or split. It is also well known that
the ancestral forms from which both horse-group and ox-
group are derived were possessed of five digits to each
limb. Professor Cop_g regards the differentiation of these
two groups as the result of the different modes of use
necessitated by different modes of life. " The mechanical
effect," he says, " of walking in the mud is to spread the
toes equally on opposite sides of the middle line. This
would encourage the equal development of the digits on
each side of the middle line, as in the cloven-footed types.
In progression on hard ground the longest toe (the third)
will receive the greatest amount of shock from contact with
the earth." * Hence the solid-hoofed types. Here, then,
the middle digit in the horse-group, or two digits in the ox-
group, having the main burden to bear, increase through
persistent use, while the other digits dwindle through dis-
use, f

On the other hand, one who holds the opposite view will

* Cope, " Origin of the Fittest," p. 374.

t It would appear, from certain passages of his " Darwinism," that Mr.
A. K. Wallace (e.g. p. 139, note) holds or held similar views. "The
genera Aides and Colobus," he says, " are two of the most purely arboreal
types of monkeys, and it is not difficult to conceive that the constant use of
the elongated fingers for climbing from tree to tree, and catching on o
branches while making great leaps, might require all the nervous energy and
muscular growth to be directed to the fingers, the small thumb remaining
useless." I should also have quoted Mr. Wallace's account of the twisting
round of the eyes of flat-fishes — where he says that the constant repetition
of the effort of twisting the eye towards the upper side of the head, when
the bony structure is still soft and flexible, causes the eye gradually to move
round the head till it comes to the upper side — had he not subsequently dis-
claimed this explanation (see Nature, vol. xl. p. 619). It is possible that Mr.
Wallace, notwithstanding the words " constant use " in the passage I have
quoted, merely intends to imply that the elongated fingers are of advantage
in climbing, and are thus subject to natural selection, the thumb diminishing
through economy of growth.

Organic Evolution. 2 1 1

say — I do not believe that use and disuse have had anything
whatever to do with the matter. Fortuitous variations in
these digits have taken place. The conditions have deter-
mined which variations should be preserved. In the horse,
variations in the direction of increase of functional value
of the mid digit, and variations in the simultaneous
decrease of the functional value of the lateral digits, have
been of advantage, and have therefore survived the elimi-
nating process of natural selection.

Now, since it is quite clear, in this and numberless
similar cases, that we can explain the facts either way, it
is obviously not worth while to spend much time or
ingenuity in devising such explanations. They are not
likely to convince any one worth convincing. What we
need is (1) crucial cases which can only be explained one
way or the other ; or (2) direct observation or experiment
leading to the establishment of one hypothesis or the other
(or both).

1. Crucial cases are very difficult to find. We cannot
exclude the element of use or disuse, for on both hypotheses
it is essential. The difference is that one school says the
organ is developed in the species by use ; the other school
says it is developed for use. What we must seek is, there-
fore, the necessary exclusion of natural selection ; and that
is not easy to prove, in any case, to a Darwinian. If it can
be shown that there exist structures which are of use, but
not of vital importance (that is to say, which have not
what I called above the available advantage necessary to
determine the question of elimination or not-elimination),
then we are perhaps able to exclude the influence of natural
selection. I think, if anywhere, such cases are to be found
in faculties and instincts ; * and as such they must be
considered in a later chapter. I will, however, here cite
one case in illustration of my meaning.

* I find, on rereading one of his articles, that I have here unwittingly
adopted one of Mr. Romanes's arguments (see Nature, vol. xxxvi. p. 406).
The instance Mr. Romanes cites is the curious habit of dogs turning round
before they lie down.

212 Animal Life and Intelligence.

We have seen that certain insects are possessed of

warning colours, which advertise their nastiness to the

taste. Birds avoid these bright but unpleasant insects,

and though there is some individual learning, there seems

to be an instinctive avoidance of these unsavoury morsels.

There is hesitation before tasting; and one or two trials

are sufficient to establish the association of gaudiness and

nastiness. Moreover, Mr. Poulton and others have shown

that, under the stress of keen hunger, these gaudy insects

may be eaten, and apparently leave no ill effects. Birds

certainly instinctively avoid bees and wasps ; and yet the

sting of these insects can seldom be fatal. It is, therefore,

improbable that nastiness or even the power of stinging

can have been an eliminating agency. In the development

of the instinctive avoidance, natural selection through

elimination seems to be excluded, and the inheritance of

individual experience is thus rendered probable. As before

pointed out, it is not enough to say that a nasty taste or a

sting in the gullet is disadvantageous; it must be shown

that the disadvantage has an eliminating value. From

my experiments (feeding frogs on nasty caterpillars, and

causing bees to sting chickens), I doubt the eliminating

value in this case. Hence elimination by natural selection

seems, I repeat, to be excluded, and the inheritance of

individual experience rendered probable.

Mr. Herbert Spencer has contended that, in certain
modifications, natural selection is excluded on the grounds
of the extreme complexity of the changes, and adduces the
case of the Irish " elk " with its huge antlers, and the giraffe
with its specially modified structure. He points out that
in either case the conspicuous modification — the gigantic
antlers or the long neck — involves a multitude of changes
affecting many and sometimes distant parts of the body.
Not only have the enormous antlers involved changes in
the skull, the bones of the neck, the muscles, blood-vessels,
and nerves of this region, but changes also in the fore
limbs ; while the long neck of the giraffe has brought with
it a complete change of gait, the co-ordinated movements

Organic Evolution. 213

of the hind limbs sharing in the general modification.
Mr. Spencer, therefore, argues that it is difficult to believe
that these multitudinous co-ordinated modifications are the
result of fortuitous variations seized upon by natural selec-
tion. For natural selection would have to wait for the
fortunate coincidence of a great number of distinct parts,
all happening to vary just in the particular way required.
That natural selection should seize upon the favourable
modification of a particular part is comprehensible enough ;
that two organs should coincidently vary in favourable
directions we can understand ; that half a dozen parts
should, in a few individuals among the thousands born, by
a happy coincidence, vary each independently in the right
way is conceivable ; but that the whole organization should
be remodelled by fortunately coincident and fortuitously
favourable variations is not readily comprehensible. It
may be answered — Notwithstanding all this, we know that
such happy coincidences have occurred, for there is the
resulting giraffe. The question, however, is not whether
these modifications have occurred or not, but whether they
are due to fortuitous variation alone, or have been guided
by functional use. The argument seems to me to have
weight.*

Still, we should remember that among neuter ants —
for example, in the Sauba ant of South America (Oecodoma
cephalotes} — there are certain so-called soldiers with rela-
tively enormous heads and mandibles. The possession of
these parts so inordinately developed must necessitate
many correlated changes. But these cannot be due to
inherited use, since such soldiers are sterile.

Furthermore, according to Professor Weismann, natural
selection is really working, not on the organism at large,
but on the germ-plasm which produces it ; and it is con-

* Mr. Darwin, while contending that the modifications need not all have
been simultaneous, says, " Although natural selection would thus tend to give
the male elk its present structure, yet it is probable that the inherited effects
of use, and of the mutual action of part on part, have been equally or more
important" ("Animals and Plants under Domestication," vol. ii. p. 328).

214 Animal Life and Intelligence.

ceivable that the variation of one or more of the few cells
in early embryonic life may introduce a great number of
variations in the numerous derivative cells. In explana-
tion of my meaning, I will quote a paragraph from a paper
of Mr. E. B. Poulton's on "Theories of Heredity.* "It
appears," he says, "that, in some animals, the great
groups of cells are determined by the first division [of the
ovum in the process of cleavage f]; in others, the right
and left sides, or front and hind ends of the body ; while
the cells giving rise to the chief groups on each side would
then be separated at some later division. This is not
theory, but fact ; for Eoux has recently shown that, if one
of the products of the first division of the egg of a frog be
destroyed with a hot needle, development is not necessarily
arrested, but, when it proceeds, leads to the formation of
an embryo from which either the right or the left side is
absent. When the first division takes place in another
direction, either the hind or the front half was absent from
the embryo which was afterwards produced. After the
next division, when four cells were present, destruction of
one produced an embryo in which one-fourth was absent."
Now, it is conceivable that a single modification or
variation of the primitive germ might give rise to many
correlated modifications or variations of the numerous cells
into which it develops ; just as an apparently trivial
incident in childhood or youth may modify the whole
course of a man's subsequent life. It is difficult, indeed,
to see how this could be effected ; to understand what could
be the nature of a modification of the germ which could
lead simultaneously to many favourable variations of bones,
muscles, blood-vessels, and nerves in different parts of the
body. This, however, is a question of the origin of varia-
tions ; and it is, at any rate, conceivable that, just as by
the extirpation with a hot needle of one cell of the cleaved
frog's ovum all the anterior part of the body should be
absent in development, so by the appropriate modification
of this one cell, or the germinal matter which produced it,

* Midland Naturalist, November, 1889. t See ante, p. 52.

Organic Evolution. 215

all the anterior part of the body should be appropriately
modified.

These considerations, perhaps, somewhat weaken the
force of Mr. Spencer's argument, which is not quite so
strong now as it was when the " Principles of Biology "
was published.

(2) We may pass now to the evidence afforded by direct
observation and experiment. There is little enough of it.
The best results are, perhaps, those which have been
incidentally reached in the poultry-yard and on the farm
in the breeding of domesticated animals. We have seen
that, under these circumstances, certain parts or organs
have very markedly diminished in size and efficiency ;
others have as markedly increased. Of the former, or
decrease in size and efficiency,1 the imbecile ducks with
greatly diminished brains have been already mentioned.
Mr. Herbert Spencer draws attention * to the diminished
efficiency in ear-muscles, giving rise to the drooping ears
of many domesticated animals. " Cats in China, horses in
parts of Eussia, sheep in Italy and elsewhere, the guinea-
pig formerly in Germany, goats and cattle in India, rabbits,
' pigs, and dogs in all long-civilized countries, have dependent
ears." f Since many of these animals are habitually well
fed, the principle of economy of growth seems excluded.
Indeed, the ears are often unusually large; it is only
their motor muscles that have dwindled either relatively
or absolutely. If what has been urged above be valid,
panmixia cannot have been operative ; since panmixia per
se only brings about regression to mediocrity. If the effects
in these two cases, ducks' brains and dogs' ears, be not due
to disuse, we know not at present to what they are due.
In the correlative case of increase by use, we find it exceed-
ingly difficult to exclude the disturbing effects of artificial
selection. The large and distended udders of cows, the
enhanced egg-laying powers of hens, the fleetness or
strength of different breeds of horses, — all of these have been

* Nature, vol. xli. p. 511.

f "Animals and Plants under Domestication," vol. ii. p. 291.

216 Animal Life and Intelligence.

subjects of long-continued, assiduous, and careful selection.
One cannot be sure whether use has co-operated or not.

Sufficient has now, I think, been said to show the
difficulty of deciding this question, the need of further
observation and discussion, and the necessity for a recep-
tive rather than a dogmatic attitude ; and sufficient, also,
to indicate my reasons for leaning to the view that use and
disuse, long-continued and persistent, may be a factor in
organic evolution.

The Nature of Variations.

The diversity of the* variations which are possible, and
which actually occur in animal life, is so great that it is
not easy to sum up in a short space the nature of variations.
Without attempting anything like an exhaustive classifica-
tion, we may divide variations into three classes.

1. Superficial variations in colour, form, etc., not neces-
sarily in any way correlated with

2. Organic variations in the size, complexity, and
efficiency of the organs of the body ;

3. Reproductive and developmental variations.

Any of these variations, if sufficient in amount and
value to determine the question of elimination or not-elimi-
nation, selection or not-selection, may be seized upon by
natural selection.

Our domesticated animals exemplify very fully the
superficial variations which, through man's selection, have
in many cases been segregated and to some extent stereo-
typed. It is unnecessary to do more than allude to the
variations in form and coloration of dogs, cattle, fowls, and
pigeons. These variations are not nec^ssarih^in&Tiy way
correlated witn any deeper organic variations. [TEeylire,
h^eve77in~ma^^cas^8^s^cp£related. For exampLeTlihe
form of the pouter pigeonis~a>rrelated with the increased
size of the crop, the length of the beak carries with it a
modification of the tongue, the widely expanded tail of the
fantail carries with it an increase in the size and number

Organic Evolution. 217

of the caudal vertebrae. And here we might take the whole
series of secondary sexual characters. These and their
like may be said to be direct correlations. But there are
also correlations which are seemingly indirect, their con-
nection being apparently remote. That in pigeons the
size of the feet should vary with the size of the beak ; that
the length of the wing and tail feathers should be corre-
lated ; that the nakedness of the young should vary with
the future colour of the plumage ; that white dogs should
be subject to distemper, and white fowls to the " gapes ; "
that white cats with blue eyes should be nearly always
deaf ; — in these cases the correlation is indirect. But from
the existence of correlation, whether direct or indirect, it
follows that variations seldom come singly. The organism
is so completely a unity that the variation of one part, even in
superficial matters, affects directly or indirectly other parts.
In the freedom of nature such superficial variations are
not so obvious. But among the invertebrates they are not
inconsiderable. The case of land-snails, already quoted,
may again be cited. Taking variations in banding alone,
Mr. Cockerell knows of 252 varieties of Helix nemoralis
and 128 of H. hortensis. Still, among the wild relatives of
our domestic breeds of animals and birds the superficial
variations are decidedly less marked. And this is partly
due to the fact that they are in a state of far more stable
equilibrium than our domestic products, and partly to the
constant elimination of all variants which are thereby
placed at a serious or vital disadvantage. . White rats,
mice, or small birds, in temperate regions, would soon be
seized upon by hawks and other enemies. If the eggs and
young of the Kentish plover, shown in our frontispiece,
were white or yellowish, like the eggs and young of our
fowls, they would soon be snapped up. The varied protec-
tive resemblances, general and special, have been brought
about by the superficial variations of organisms, and the
elimination of those which, from non-variation or wrong
variation, remained conspicuous. We need only further
notice one thing here, namely, that, in the case of special

218 Animal Life and Intelligence.

resemblance to an inorganic object or to another organism,
the variations of the several parts must be very closely,
and sometimes completely, correlated. The correlations,
however, need not, perhaps, have been simultaneous — the
resemblance having been gradually perfected by the filling
in of additional touches, first one here, then another there,
and so on.

Concerning " organic variations," little need be said.
It is clear that an organ or limb may vary in size, such
variation carrying with it a correlative variation in power ;
or it may vary in complexity — the teeth of the horse tribe,
for example, having increased in complexity, while their
limbs have been rendered less complex ; or it may vary
in efficiency through the more perfect correlation and co-
ordination of its parts.

The evidence of such variations from actual observation
is far less in amount than that of superficial variations.
And this is not to be wondered at, since in many cases
it can only be obtained by careful anatomical investigation.
Nevertheless, anatomists, both human and comparative,
are agreed that such variations do occur. And no one can
examine such a collection as that of the Koyal College of
Surgeons without acknowledging the fact.

Thirdly, " reproductive and developmental variations "
are of very great importance. The following are among
the more important modifications which may occur in the
animal kingdom.

1. Variations in the mode of reproduction, sexual or
asexual.

2. Variations in the mode of fertilization.

3. Variations in the number of fertilized ova produced.

4. Variations in the amount of food-yolk and in the
way in which it is supplied.

5. Variations in the time occupied in development.

6. Variations in the time at which reproduction com-
mences.

7. Variations in the duration and amount of parental
protection and fosterage.

Organic Evolution. 219

8. Variations in the period at which secondary sexual
characters and the maximum efficiency of the several
organs is reached.

It is impossible here to discuss these modes of variation
seriatim. I shall therefore content myself with but a few
remarks on the importance of protection and fosterage. It
is not too much to say that, without fosterage and protec-
tion, the higher forms of evolution would be impossible. If
you are to have a highly evolved form, you must allow
time for its evolution from the egg; and that develop-
ment may go on without let or hindrance, you must supply
the organism with food and lighten the labour of self-
defence. Most of the higher organisms are slow in coming
to maturity, passing through stages when they are helpless
and, if left to themselves, would inevitably fall a prey to
enemies.

In those animals in which the system of fosterage and
protection has not been developed a great number of
fertilized ova are produced, only a few of which come to
maturity. It might be suggested that this is surely an
advantage, since the greater the number produced the
greater the chances of favourable variations taking place.
But it has before been pointed out that these great numbers
are decimated, and more than decimated, not by elimina-
tion, but by indiscriminate destruction ; embryos, good,
bad, and indifferent, being alike gobbled up by those who
had learnt the secret of fostering their young. The
alternative has been between producing great numbers * of
embryos which soon fend for themselves, and a few young
who are adequately provided for during development. And
the latter have proved the winners in life's race. If we
compare two flat-fishes belonging to very different groups,
the contrast here indicated will be readily seen. The
skate is a member of the shark tribe, flattened sym-

* In the third chapter we saw that in such cases not only are there an
enormous number of ova produced, but that (e.g. in aurelia and the liver-
fluke) each ovum produces, through the intervention of asexual multiplica-
tion, many individuals.

220 Animal Life and Intelligence.

metrically from above downwards. It lays, perhaps, eighty
to a hundred eggs. Each of these is large, and has a
rich supply of nutritive food-yolk. Each is also protected
by a horny case with pointed corners — the so-called sea-
purse of seaside visitors. These are committed by the
skate to the deep, and are not further cared for. But the
abundant supply of food-yolk gives the little skate which
emerges a good start in life. On the other hand, the
turbot, one of the bony fishes, flattened from side to side
with an asymmetrical head, lays several millions of eggs,
which float freely in the open sea. These are minute and
glassy, and not more than one-thirtieth of an inch in
diameter. When the fishes are hatched, they are not
more than about one-fifth of an inch in length. The
slender stock of food-yolk is soon used up, and henceforth
the little turbot (at present more like a stump-nosed eel
than a turbot) has to get its own living. Hundreds of
thousands of them are eaten by other fishes.

Or, if we compare such different vertebrates as a frog, a
sparrow, and a mouse, we find that the frog produces a
considerable number of fertilized ova, though few in com-
parison with the turbot, each provided with a small store
of food-yolk. The tiny tadpoles very soon have to obtain
their own food and run all the risks of destruction. Few
survive. The sparrow lays a few eggs; but each is
supplied with a large store of food-yolk, sufficient to meet
its developmental needs until, under the fostering influence
of maternal warmth, it is hatched. Even on emerging
from the eggs, the callow fledglings enjoy for a while
parental protection and fosterage, and, when sent forth
into the world, are very fairly equipped for life's struggle.
The mouse produces minute eggs with little or no food-
yolk ; but they undergo development within the womb of
the mother, and are supplied with nutrient fluids elaborated
within the maternal organism. Even when born, they are
cherished for a while and supplied with food-milk by the
mother.

The higher stages of this process involve a mental

Organic Evolution. 221

element, and are developed under the auspices of in-
telligence or instinct. But the lower stages, the supply of
food-yolk and intra-uterine protection, are purely organic.
A hen cannot by instinctive or intelligent forethought
increase the amount of food-yolk stored up in the ovum,
any more than the lily, which, by an analogous process,
stores up in its bulb during one year material for the best
part of next year's growth, can increase this store by a
mental process.

It cannot therefore be questioned that variations in the
amount of capital with which an embryo is provided in
generation would very materially affect its chances of
escaping elimination by physical circumstances, by enemies,
and by competition.

Nor can it be questioned that variations in the time
occupied in reaching maturity would, other things equal,
not a little affect the chances of success of an organism in
the competition of life. Hence we have the phenomena
of what may be termed acceleration and retardation in
development. These terms have, however, been used by
American zoologists, notably Professors Hyatt and Cope,
in a somewhat different and wider sense ; for they include
not merely time-changes, but also the loss of old characters
or the acquisition of new characters. "It is evident,"
says Professor Cope, " that the animal which adds some-
thing to its structure which its parents did not possess
has grown more than they; while that which does not
attain to all the characteristics of its ancestors has grown
less than they." " If the embryonic form be the parent, the
advanced descendant is produced by an increased rate of
growth, which phenomenon is called ' acceleration ; ' but if
the embryonic type be the offspring, then its failure to
attain the condition of the parent is due to the supervention
of a slower rate of growth ; to this phenomenon the term
'retardation' is applied." "I believe that this is the
simplest mode of stating and explaining the law of varia-
tion : that some forms acquire something which their
parents did not possess; and that those which acquire

222 Animal Life and Intelligence.

something additional have to pass through more numerous
stages than their ancestors ; and those which lose some-
thing pass through fewer stages than their ancestors ; and
these processes are expressed by the terms ' acceleration '
and ' retardation.' " *

It is clear, however, that we have here something more
than acceleration and retardation of development in the
ordinary sense of these words. It would be, therefore, more
convenient to use the term " acceleration " for the con-
densation of the same series of developmental changes into a
shorter period of time ; " retardation " for the lengthening of
the period in which the same series of changes are effected ;
and " arrested development " for those cases in which the
young are born in an immature or embryonic condition.
"Whether there is any distinct tendency, worthy of formu-
lation as a law, for organisms to acquire, as a result of
protracted embryonic development, definite characteristics
which their ancestors did not possess, I think very question-
able. If so, this will fall under the head of the origin of
variations.

That acceleration, in the sense in which I have used
the term, does occur as a variation is well known. " With
our highly improved breeds of all kinds," says Darwin,t
" the periods of maturity and reproduction have advanced
with respect to the age of the animal ; and in correspondence
with this, the teeth are now developed earlier than formerly,
so that, to the surprise of agriculturalists, the ancient rules
for judging of the age of an animal by the state of its teeth
are no longer trustworthy." " Disease is apt to come on
earlier in the child than in the parent ; the exceptions in
the other direction being very much rarer." } Professor
Weismann contends that the time of reproduction has been
accelerated through natural selection, since the shorter the
time before reproduction, the less the number of possible
accidents. We may, perhaps, see in the curious cases of

* Cope, " Origin of the Fittest, " pp. 226, 125, and 297.

f " Animals and Plants under Domestication," vol. ii. p. 313.

$ Ibid. p. 56.

Organic Evohition. 223

reproduction during an otherwise immature condition,
extreme instances of acceleration. The axolotl habitually
reproduces in the gilled, or immature condition. Some
species of insects reproduce before they complete their
metamorphoses. And the females of certain beetles (Phen-
godini) are described by Professor Eiley as larviform.*

Precocity is variation in the direction of acceleration,
and that condensed development which is familiar in the
embryos of so many of the higher animals may be regarded
as the result of variations constantly tending in the same
direction. That there are fewer examples of retardation
is probably due to the fact that nature has constantly
favoured those that can do the same work equally well in
a shorter time than their neighbours. But there can be
no doubt that, accompanying that fosterage and protection
which is of such marked import in the higher animals,
there is also much retardation. And as bearing upon the
supposed law of variation as formulated by Messrs. Hyatt
and Cope, it should be noted that this retardation or
decreased rate of growth leads to the production of the
more advanced descendant.

The Inheritance of Variations.

Given the occurrence of variations in certain individuals
of a species, we have the alternative logical possibilities
of their being inherited or their not being inherited. The
latter alternative seems at first sight to be in contradiction
to the law of persistence. Sir Henry Holland, seeing this,
remarked that the real subject of surprise is, not that a
character should be inherited, but that any should ever
fail to be inherited, t Intercrossing may diminish a
character, and sooner or later practically obliterate it :
annihilate it at once and in the first generation it cannot.
This logical view, however, ceases to be binding if we admit,

* Nature, vol. xxxvi. p. 592.

t Quoted from " Medical Notes and Reflections," 1855, p. 267, by Darwiu,
" Animals arid Plants under Domestication," vol. i. p. 446.

224 Animal Life and Intelligence.

with Professor Weismann, that variations may be produced
in the body without in any way affecting the germ. It is
also vitally affected if we believe that the hen does not
produce the egg, though she may, perhaps, modify the eggs
inside her ; for the modification of the hen (i.e. the variety
in question) may not be of the right nature or of sufficient
strength to impress itself upon the germinal matter of the
egg. We may at once admit, then, that acquired varia-
tions need not be inherited.

Passing^P innate variations — variations, that is to say,
which are the outcome of normal development from the
fertilized ovum — must they be inherited, at any rate, in
some degree ? It seems to me that they must, on the
hypothesis that sexual generation involves simply the
blending or commingling of the characters handed on in
the ovum or the sperm. The only cases where this would
apparently fail to hold good would be where the ovum
and the sperm handed on exactly opposite tendencies —
a variation in excess contributed by the male precisely
counterbalancing a variation in the opposite direction con-
tributed by the female parent. Even here the tendency is
inherited, though it is counterbalanced. On the hypothesis
of "organic combination" before alluded to (p. 150), varia-
tions might, however, in the union of ovum and sperm,
be not only neutralized, but augmented. If the variation
be, so to speak, a definite organic compound resulting from
a fortunate combination of characters in ovum and sperm,
it might either fail altogether, or be repeated in an en-
feebled form, or augmented in the offspring, according as
the new conditions of combination were unfavourable or
favourable.

Whether innate variations ever actually fail to be
inherited, even in an enfeebled form, it is very difficult to
say ; for if this, that, or the other variation fail to be thus
inherited, it is difficult to exclude the possibility of its
being an acquired variation not truly innate. Certainly
variations seem sometimes to appear in one generation,
and not to be inherited at all. And, as we have seen, Mr.

Organic Evolution. 225

Eomanes appeals to a gradual failure of heredity, apart
from intercrossing, to explain the diminution of disused
organs.

That a variation strongly developed in both parents is
apt to be augmented in the offspring is commonly believed
by breeders. Darwin was assured that to get a good
jonquil-coloured canary it does not answer to pair two
jonquils, as the colour then comes out too strong, or is
even brown. Moreover,* " if two crested canaries are paired,
the young birds rarely inherit this character ; for in crested
birds a narrow space of bare skin is left on the back of the
head, where the feathers are upturned to form the crest,
and, when both parents are thus characterized, the bare-
ness becomes excessive, and the crest itself fails to be
developed."

On the whole, it would seem that variations may either
be neutralized or augmented in inheritance ; but the deter-
mining causes are not well understood.

Another fact to be noticed with regard to the inheritance
of variations is that some characters blend in the offspring,
while others apparently fail to do so. Mr. Francis Galton,f
speaking of human characters, gives the colour of the skin
as an instance of the former, that of the eyes as an
example of the latter. If a negro marries a white woman,
the offspring are mulattoes. But the children of a light-
eyed father and a dark-eyed mother are either light-eyed
or dark-eyed. Their eyes do not present a blended tint.
Among animals the colour of the hair or feathers is often a
mean or blended tint ; but not always. Darwin gives the
case of the pairing of grey and white mice, the offspring of
which are not whitish-grey, but piebald. If you cross a
white and a black game bird, the offspring are either black
or white, neither grey nor piebald. Sir R. Heron crossed
white, black, brown, and fawn-coloured Angora rabbits, and
never once got these colours mingled in the same animal,
but often all four colours in the same litter. He also

* Darwin, " Animals and Plants under Domestication," vol. i. p. 465.
t " Natural Inheritance," p. 12.

226 Animal Life and Intelligence.

crossed " solid-hoofed " and ordinary pigs. The offspring
did not possess all four hoofs in an intermediate condition ;
but two feet were furnished with properly divided and two
with united hoofs.* Professor Eimerf has noticed that, in
the crossing of striped and unstriped varieties of the
garden snail, Helix hortensis, the offspring are either striped
or unstriped, not in an intermediate or faintly striped
condition.

These facts are of no little importance. They tend to
minimize, for some characters at least, the effects of inter-
crossing. The variations which present this trait may be
likened to stable organic compounds, which may be in-
herited or not inherited, but which cannot be watered down
by admixture and intercrossing. It is well known J that,
in 1791, a ram-lamb was born in Massachusetts, with
short, crooked legs and a long back, like a turn-spit dog.
From this one lamb § the otter, or ancon, breed was raised.
When sheep of this breed were crossed with other breeds,
the lambs, with rare exceptions, perfectly resembled one
parent or the other. Of twin lambs, even, one has been
found to resemble one parent, and the second the other.
All that the breeder has to do is to eliminate those which
do not possess the required character. And very rarely
do the lambs of ancon parents fail to be true-bred.

Now, it can scarcely fail that such sports occur in
nature. And if they are stable compounds, they will not
be readily swamped by intercrossing. It only requires some
further isolation to convert the sporting individuals into a
distinct and separate variety. Now, Darwin tells us that

* Darwin, " Animals and Plants under Domestication," vol. ii. p. 70.

t " Organic Evolution," Mr. Cunningham's translation, p. 76.

J Darwin, " Animals and Plants uuder Domestication," vol. i. p. 104.

§ Similarly, from a chance sport of a one-eared rabbit, Anderson formed a
breed which steadily produced one-eared rabbits (" Animals and Plants under
Domestication," vol. i. p. 456). This is an example of asymmetrical variation.
Variations are generally, but not always, symmetrical. Superficial colour-
variations are sometimes asymmetrical. Gasteropod molluscs are nearly
always asymmetrically developed. Among insects, Anisognathus affords an
example of the asymmetrical development of the mandible. Our right-handed-
ness is a mark of asymmetry.

Organic Evolution. 227

the ancons have been observed to keep together, separating
. themselves from the rest of the flock when put into
enclosures with other sheep. Here, then, we have pre-
ferential mating as the further isolating factor. I feel
disposed, therefore, to agree with Mr. Galton when he
says,* " The theory of natural selection might dispense
with a restriction for which it is difficult to see either the
need or the justification, namely, that the course of evolu-
tion always proceeds by steps that are severally minute,
and that become effective only through accumulation.
That the steps may be small, and that they must be small,
are very different views ; it is only to the latter that I
object, and only when the indefinite word ' small ' is used
in the sense of ' barely discernible,' or as small as com-
pared with such large sports as are known to have been
the origins of new races."

Connected, perhaps, with the phenomena we have just
been considering is that of prepotency .f It is found that,
when two individuals of the same race or of different races
are crossed, one has a preponderant influence in deter-
mining the character of the offspring. Thus the famous
bull Favourite is believed to have had a prepotent influence
on the short-horn race ; and the improved short-horns
possess great power in impressing their likeness on other
breeds. The phenomena are in some respects curiously
variable. In fowls, silkiness of feathers seems to be at
once bred out by intercrossing between silk-fowl and any
other breed. But in the silky variety of the fan-tail
pigeon this character seems prepotent ; for, when the
variety is crossed with any other small-sized race, the
silkiness is invariably transmitted. One may fairly sup-
pose that prepotent characters have unusual stability;
but to what causes this stability is due we are at present
ignorant.

Lastly, we have to consider the phenomenon of latency.

* " Natural Inheritance," p. 32.

f See " Animals and Plants under Domestication," vol. ii. p. 40, from
which illustrations are taken.

228 Animal Life and Intelligence.

This is the lying hid of characters and their subsequent
emergence. We may distinguish three forms of latency.

1. Where characters lie hid till a certain period of life,
and then normally emerge.

2. Where the characters normally lie hid throughout
life, but are, under certain circumstances, abnormally
developed.

8. Where the characters lie hid throughout life, but
appear in the offspring or (sometimes distant) descendants.

Latency is often closely connected with correlated
variations. Secondary sexual characters, for example, are
correlated with the functional maturity or activity of the
reproductive organs. They therefore lie hid until these
organs are mature and ready for activity. When they
are restricted to the male, they normally remain latent
throughout the life of the female, but reappear in her male
offspring. Under abnormal conditions, such as the removal
of the essentially male organs, the secondary sexual charac-
ters correlated with them do not appear, or appear in a
lessened and modified form. The males may even, under
such circumstances, acquire female characters. Thus
capons take to sitting, and will bring up young chickens.
Conversely, females which have lost their ovaries through
disease or from other causes sometimes acquire secondary
sexual characters proper to the male. Characters thus
normally latent abnormally emerge. Mr. Bknd Button*
gives a case of a hen golden pheasant which " presented
the resplendent dress of the cock, but her plumage was not
quite so brilliant ; she had no spurs, and the iris was not
encircled by the ring of white so conspicuous in the male."
Her ovary was no larger than a split pea.

A curious instance of latent characters correlated with
sex is seen in hive bees. The worker bee differs from the
female in the rudimentary condition of the sexual organs,
in size and form, and in the higher development of the
sense-organs. But it is well known that, if a very young
worker grub be fed on " royal jelly," she will develop into

* " Evolution and Disease," p. 169.

Organic Evolution. 229

a perfect queen. Not only are the sexual organs stimulated
to increased growth and functional activity, but the corre-
lated size and condition of the sense-organs are likewise
acquired. The characters of queen and worker are latent
in the grub. According to the nature of the food it receives,
the one set of characters or the other emerges. Professor
Yung's tadpoles and Mrs. Treat's butterflies (ante, p. 59)
afford similar instances.

We come now to those cases of latency in which this
obvious correlation does not occur. They afford examples
of reversion to more or less remote ancestral characters.
In some cases the cause of such reversion — such unexpected
emergence of characters, which have remained latent
through several, perhaps many, generations — is quite un-
known. In others, " at any rate among domesticated
animals, the determining condition of such reversion is the
crossing of distinct breeds.

Darwin gives * an instance of reversion, on the authority
of Mr. E. Walker. He bought a black bull, the son of a
black cow with white legs, white belly, and part of the tail
white; and in 1870 a calf, the gr-gr-gr-gr-grandchild of
this cow, was born, coloured in the same very peculiar
manner, all the intermediate offspring having been black.
In man partial reversions are not infrequent. An addi-
tional pair of lumbar ribs is sometimes developed, and in
such cases the fan-shaped tendons which are normally
connected with the transverse processes of the vertebra are
replaced by functional levator muscles. Since it is probable
that the ancestor of man had more than the twelve pairs
of ribs that are normally present in the human species,
we may, perhaps, fairly regard the supernumerary rib as a
reversion. But it may be a new sport on old lines.

The occasional occurrence in Scotland of red grouse
with a large amount of white in the winter plumage,
especially on the under parts, is justly regarded by Mr.
Wallace t as a good example of reversion or latency in

* " Animals and Plants under Domestication," vol. ii. p. 8.
f " Darwinism," p. 107.

230 Animal Life and Intelligence.

wild birds. There can be little doubt that, as he suggests,
the Scotch red grouse is derived from a form which, like
the wide-ranging willow grouse, has white winter plumage.
During the glacial epoch this would be an advantage.
" But when the cold passed away, and our islands became
permanently separated from the mainland, with a mild
and equable climate, and very little snow in winter, the
change to white at that season became hurtful, rendering
the birds more conspicuous, instead of serving as a means
of concealment." The red grouse has lost its white winter
dress ; but occasional reversions point to the ancestral
habit.

That crossing tends to produce reversion is a fact
familiar to breeders and fanciers, and one which is
emphasized by Darwin. When pigeons are crossed, there
is a strong tendency to revert to the slatey-blue tint and
black bars of the ancestral rock-pigeon. There is always
a tendency in sheep to revert to a black colour, and this
tendency is emphasized when different breeds are crossed.
The crossing of the several equine species (horse, ass, etc.)
" tends in a marked manner to cause stripes to appear on
various parts of the body, especially on the legs," and this
may be a reversion to the condition of a striped and zebra-
like ancestor. Professor Jaeger described a good case with
pigs. " He crossed the Japanese, or masked breed, with
the common German breed, and the offspring were inter-
mediate in character. He then recrossed one of these
mongrels with a pure Japanese, and in the litter thus
produced one of the young resembled in all its characters
a wild pig ; it had a long snout and upright ears, and was
striped on the back. It should be borne in mind that the
young of the Japanese breed are not striped, and that they
have a short muzzle and ears remarkably dependent." *
Darwin crossed a black Spanish cock with a white silk hen.
One of the offspring almost exactly resembled the Gallus
bankiva, the remote ancestor of the parents.

Such cases would seem to show that in our domestic

* Darwin, " Animals and Plants under Domestication," vol. ii. pp. 17, 18.

Organic Evolution. 231

breeds ancestral traits lie latent. The crossing of distinct
varieties may either neutralize the variations artificially
selected, and thus allow the ancestral characters which
have been masked by them to reappear ; or they may
allow the elements of the ancestral traits, long held apart
in separate breeds by domestication, to recombine with the
consequent emergence of the normal characters of the wild
species. But, in truth, any attempted explanations of the
facts are little better than guess-work. There are the
facts. And the importance of crossing as a determining
condition in domesticated animals should make us cautious
in applying reversion, as it occurs in such cases, to wild
species which live under more stable conditions where
crossing is of rare occurrence.

The Origin of Variations. ^ *

The subject of the origin of variations is a difficult one,
one concerning which comparatively little is known, and
one on which I am not able to throw much light.

Taking a simple animal cell as our starting-point, we
have already seen that it performs, in primitive fashion,
certain elementary and essential protoplasmic activities,
and gives rise to certain products of cell-life. In the
metazoa, which are co-ordinated aggregates of animal
cells, together with some of their products, there is seen a
division of labour and a differentiation of structure among
the cells. We see, then, that variation among these related
cells has led to differences in size, in form, in transparency,
and in function ; while the cell-products have been differ-
entiated into those which are of lifelong value, such as
bone, cartilage, connective tissue, horn, chitin, etc.,
together with a variety of colouring matters ; those which
are of temporary value, such as the digestive secretions,
fat, etc. ; and those which are valueless or noxious, such as
carbonic acid gas and urea, which are excreted as soon as
possible. Here are already a number of important and
fundamental variations to be accounted for.

232 Animal Life and Intelligence.

Let us notice that, wide as the variations are, they are /
to a large extent hedged in by physical, chemical, and/
organic limitations. We have already seen that the size
of cells is to a large extent limited, because during growth
mass tends to outrun surface ; and because, while disrup-
tive changes occur throughout the mass, nutriment and
oxygen must be absorbed by the surface. This is a
physical limitation. Since the products of cell-life and
cell-activity are chemical products, it is clear that they can
only be produced under the fixed limitations of chemical
combination ; and though in organic products these limi-
tations are not so rigid as among inorganic substances,
still that there are limitations no chemist is likely to
question. The organic limitations are to the varied, but
not very numerous, modes of protoplasmic activity.

Probably, even at the threshold of metazoan life, such
variations did not affect only individual cells, but rather
groups of cells. In other words, the differentiation was at
once and primarily a tissue-differentiation. What do we
know, however, about the primitive tissue-differentiation of
the earliest metazoa ? Hardly anything. We may fairly
suppose that the first marked difference to appear was
that between the outside and the inside. In the formation
of an embryo this is the first differentiation we notice.
From the beginning of segmentation or, in any case, very
early, the outer-layer cells become marked off from the
inner-layer cells. The next step was, perhaps, the forma-
tion of the mid-layer between the outer and inner. But
how further differentiations were effected we really do not
know, though we may guess a little. This, perhaps, we
may fairly surmise — that fresh differentiations presupposed
previous differentiations, and formed the basis of yet further
differentiations. Thus calcified cartilage presupposes car-
tilage, and leads up to the formation of true bone. In all
this, however, we .are very much in the dark. We can
watch, always with fresh wonder, the genesis of tissues in
the development of the embryo ; but we do not at present
know much of the mode of their primitive genesis in the

Organic Evolution. 233

early days of organic evolution: how can we, then, pre-
tend to understand their origins ?

If we speculate at all on the matter, we are led to the
view that the variations must be primarily due to the
differential incidence of mechanical stresses and physical
or chemical influences. It may be admitted that this is
little more than saying that they are due to some physical
cause. Still, this at least may be taken as certain for
what it is worth — that the primitive tissue-differentiations
are due to physical or chemical influences, direct or indirect,
on the protoplasm of the cell. Here is one mode of the
origin of variations.

I do not wish to reopen the question whether these"
variations originate in the germ or in the body. I content
myself with indicating the difference, from this standpoint,
between the two views. Take, for example, the end-organs
of the special senses, which respond explosively to physical
influences in- ways we shall have to consider more fully in
the next chapter. If we hold that variations originating
in the body may be transmitted through the germ to the
offspring, then we may say that these variations are the
direct result of the incidence of the physical or molecular
vibrations on the protoplasm. But if we believe, with
Professor Weismann, that all variations originate in the
germ, then the variations in the end-organs of the special
senses, fitting them to be the recipients of special modes of
influence, result from physical effects upon the germ of
purely fortuitous origin, that is to say, wholly unrelated to
the end in view. The rods and cones of the retina are due
to purely chance variations, impressed by some chemical
or physical causes completely unknown on the germinal
protoplasmic substance. Those individuals which did not
have these chance variations have been eliminated. It
matters not that the rods and cones are believed to have
reached their present excellence through many intermediate
steps from much simpler beginnings. The fact remains
that the origin of all these step-like variations was fortui-
tous, and not in any way the direct outcome of the physical

234 Animal Life and Intelligence.

influences which their products, the rods and cones, have
become fitted to receive. I am not at present prepared to ac- >
ceptthis theory of the germinal origin of all tissue-variations./

Whether use and disuse are to be regarded as sources
of origin of variations is, again, a matter in which there
is wide difference of opinion. But if we admit that any
variations can take their origin in the body (as dis-
tinguished from the germ), then there is no a priori reason
for rejecting use and disuse as factors. As such, we are, I
think, justified, in the present state of our knowledge, in
reckoning them, at all events, provisionally.

It is clear, however, that they are a proximate, not an
ultimate, source of origin. I mean that the structures
must be there before they can be either strengthened or
weakened by use or disuse. They are at most a source of
positive or negative variations of existing structures. They
cannot be a direct source of origin of superficial variations.
Gain or loss of colour ; form-variations not correlated with
organic variations ; — these cannot be directly due to use or
disuse. It is in the nervous and muscular systems and the
glandular organs that use and disuse are mainly operative.
When, however, organs are brought into relation, or fail to
be brought into relation, to their appropriate stimuli, we
speak of this, too, as use and disuse. We say, for example,
that persistent disuse may impair the essential tissues of
the recipient end-organs of the special senses, implying
that these tissues require to be brought into continued
relation to the appropriate stimuli in order that their
efficiency be maintained. So, too, we say that the epidermis
is thickened by use, meaning that it is brought into rela-
tion with certain mechanical stresses. Through correlation,
too, the effects of use and disuse may be widespread. Thus
increase in the size of a group of muscles may be correlated
with increase in the size of the bones to which they are in
relation. In fact, so knit together and co-ordinated is the
organism into a unity, it is probable that hardly any
variation could take place through use or disuse without
modifying to some extent the whole organic being.

Organic Evolution. 235

Once more, let it be clearly remembered that a large
and important school of zoologists reject altogether use or
disuse as a factor in variation. They believe that those
germs are selected through natural selection in which
there is an increased tendency to use or disuse of certain
organs. In this, however, we are all agreed. The real
question is what is the source of origin of this tendency.
On the view of germinal origin, we are forced back on
unknown physical or chemical influences in no wise related
in origin (though, of course, related in result) with the use
or disuse to which they give rise.

So far the main distinction between the two biological
schools seems to be that the one, placing the origin of
variation in the body-tissues, regards the variations as
evoked in direct reaction to physical or chemical influences ;
while the other, placing the origin of variation in the
germ, regards the variations as of fortuitous origin.

I do not use the phrase, " of fortuitous origin," as in
any sense discrediting the theory. I am not attempting
the cheap artifice of damning a view that does not happen
to be my own with a phrase or a nickname. And I there-
fore hasten to point out what variations I do believe to
have had a fortuitous origin. The phrase is often mis-
understood, and they will serve to explain its meaning.

If the reader will kindly refer to the tables of variations
in the bats' wings (Figs. 14-17), he will see that there are
a great number of bones which vary in length and vary
independently. And if he will also refer to Fig. 18, in
which seven species of bats are compared, he will see that
the differences arise from the increased length of one set
of bones in one species and another set of bones in another
species. Now, let us suppose that the long, swallow-like
wing of the noctule, a high flyer with rapid wing-strokes,
that catches insects in full flight, and the broad wings of
the horse-shoe, a low flyer, flapping slowly, and, at any
rate, sometimes catching insects on the ground, and cover-
ing them with its wings as with a net ; let us suppose, I
say, that to each species its special form of wing is an

236 Animal Life and Intelligence.

advantage. Among thousands of independent variations
in the lengths of the bones there would be occasional com-
binations of variations, giving either increased length or
increased breadth to the wing. In the noctule, the former
would tend to be selected; in the horse-shoe, the latter.
Thus the wing of the noctule would be lengthened, and that
of the horse-shoe broadened, through the selection of for-
tuitous combinations of variations which chanced to be
favourable. Now, each individual bone-variation is, we
believe, due to some special cause ; but the fortunate com-
bination is fortuitous, due to what we term " mere chance."

Darwin believed that chance, in this sense, played a
very important part in the origin of those favourable
variations for which, as he said, natural selection is con-
stantly and unceasingly on the watch. And there can be
little question that Darwin was right.

We must now consider very briefly some of the proxi-
mate causes of variations. In most of these cases we
cannot hope to unravel the nexus of causation. When a
plexus of environing circumstances acts upon a highly
organized living animal, the most we can do in the present
state of knowledge is to note — we cannot hope to explain —
the effects produced.

All readers of Darwin's works know well how insistent
he was that the nature of the organism is more important
than the nature of the environing conditions. " The
organization or constitution of the being which is acted
on," he says,* "is generally a much more important
element than the nature of the changed conditions in
determining the nature of the variation." And, again, t
" We are thus driven to conclude that in most cases the
conditions of life play a subordinate part in causing any
particular modification ; like that which a spark plays
when a mass of combustible matter bursts into flame — the

* " Animals and Plants under Domestication," vol. ii. p. 201.

f Ibid. p. 282. The phenomena of the seasonal dimorphism of butterflies
and moths show that changes of temperature (and perhaps moisture, etc.)
determine very strikiug differences in these insects.

Organic Evolution. 237

nature of the flame depending on the combustible matter,
and not on the spark."

Eecent investigations have certainly not lessened the
force of Darwin's contention. From which there follows
the corollary that the vital condition of the organism is a
fact of importance. Darwin was led to believe that among
domesticated animals and plants good nutritive conditions
were favourable to variation. " Of all the causes which
induce variability," he says,* " excess of food, whether or
not changed in nature, is probably the most powerful."
Darwin also held that the male is more variable than the
female — a view that has been especially emphasized by
Professor W. K. Brooks. Mr. Wallace, as we have already
seen, regards the secondary sexual characters of male birds
as the direct outcome of superabundant health and vigour.
"There is," he says,f "in the adult male a surplus of
strength, vitality, and growth-power which is able to
expend itself in this way without injury." And Messrs.
Geddes and Thomson contend \ that " brilliancy of colour,
exuberance of hair and feathers, activity of scent-glands,
and even the development of weapons, are in origin and
development outcrops of a male as opposed to a female
constitution."

There is, I think, much truth in these several views
thus brought into apposition. Vigour and vitality, pre-
dominant activity and the consequent disruptive changes,
with their abundant by-products utilized in luxuriant out-
growths and brilliant colours, are probably important
sources of variation. They afford the material for natural
selection and sexual selection to deal with. These guide
the variations in specific directions. For I am not pre-
pared to press the theory of organic combination so far as
to believe that this alone has served to give definiteness
to the specific distinctions between secondary sexual charac-
ters, though it may have been to some extent a co-operating
factor. This, however, is a question apart from that of

* " Animals and Plants under Domestication," vol. ii. p. 244.

t " Darwinism," p. 293. J " Evolution of Sex," p. 22.

238 Animal Life and Intelligence.

origin. Superabundant vigour may well, I think, have
been a source of origin, not only of secondary sexual charac-
ters, but of many other forms of variation.

And while these forms of variation may be the special
prerogative of the male, we may perhaps see, in super-
abundant female vigour, a not less important source of
developmental and embryonic variations in the offspring.
The characteristic selfishness of the male applies his surplus
vitality to the adornment of his own person; the charac-
teristic self-sacrifice of the mother applies her surplus
vitality to the good of her child. Here we may have the
source and origin of those variations in the direction of
fosterage and protection which we have seen to have such
important and far-reaching consequences in the develop-
ment of organic life. The storage of yolk in the ovum, the
incubation of heavily yolked eggs, the self-sacrificing de-
velopment in the womb, the elaboration of a supply of
food-milk, — all these and other forms of fosterage may well
have been the outcome of superabundant female vigour,
the advantages of which are thus conferred upon the
offspring.

We may now proceed to note, always remembering the
paramount importance of the organism, some of the effects
produced by changes in the environment.

The most striking and noteworthy feature about the
effects of changes of climate and moisture, changes of
salinity of the water in aquatic organisms, and changes
of food-stuff, is that, when they produce any effect at
all, they give rise to definite variations. Only one or
two examples of each can here be cited. Mr. Merrifield,*
experimenting with moths (Selenia illunaria and S. illus-
traria), finds that the variations of temperature to which
the pupae, and apparently also the larvae, are subjected
tend to produce "very striking differences in the moths."
On the whole, cold " has a tendency, operating possibly
by retardation, to produce or develop a darker hue in

* "Incidental Observations in Pedigree Moth-breeding," F. Merrifield.
Transactions Entomological Society, 1889, pt. i. p. 79, et neq.

Organic Evolution. 239

the perfect insect ; if so, it may, perhaps, throw some
light on the melanism so often remarked in north-country
examples of widely distributed moths." Mr. Cockerell*
regards moisture as the determining condition of a certain
phase of melanism, especially among Lepidoptera. The
same author states that the snail "Helix nemoralis was
introduced from Europe into Lexington, Virginia, a few
years ago. Under the new conditions it varied more than
I have ever known it to do elsewhere, and up to the
present date (1890) 125 varieties have been discovered
there. Of these, no less than 67 are new, and unknown
in Europe, the native country of the species." The effects
of the salinity of the water on the brine-shrimp Artemia
have already been mentioned. One species with certain
characteristics was transformed into another species with
other characteristics by gradually altering the saltness of
the water. So, too, in the matter of food, the effects of
feeding the caterpillars of a Texan species of Saturnia on
a new food-plant were so marked that the moths which
emerged were reckoned by entomologists as a new species.
The point, I repeat, to be especially noted about these
cases and others which might be cited, f is that the varia-
tion produced is a definite variation. Very probably it is
generally, or perhaps always, produced in the embryonic
or larval period of life. In some cases the variation seems
to be transmissible, though definite and satisfactory proofs
of this are certainly wanting. Still, we may say that if
the changed conditions be maintained, the resulting varia-
tion will also be maintained. Under these conditions, at
least, the variation is a stable one. It is probable that,
apart from preferential mating, the varieties thus produced
will tend to breed together rather than to be crossed with
the parent form or varieties living under different con-
ditions. In this way varieties may sometimes arise by

* Nature, vol. xli. p. 393.

t See Professor Meldola's edition of Professor Weismann's " Studies in
the Theory of Descent," and Mr. Cunningham's translation of Professor
Elmer's " Organic Evolution."

240 Animal Life and Intelligence.

definite and perhaps considerable leaps under the influence
of changed conditions. We must not run the adage, Natura
nil facit per saltum, too hard, nor interpret saltum in too
narrow a sense.

It is true, and we may repeat the statement of the fact
for the sake of emphasis, that we do not know how or why
this or that particular variation should result from this or
that change of climate, environment, or food-stuff ; nor do
we know why certain variations (such as that which pro-
duced the ancon breed of sheep) should be stable, while
other variations are peculiarly unstable. But in this we
are not worse off than we are in the study of inorganic
nature. We do not know why calcite should crystallize in
any particular one of its numerous varieties of crystalline
form ; we do not know why some of these are more stable
than others. We may be able to point to some of the
conditions, but we cannot be said to understand why
arragonite should be produced under some circumstances,
calcite under others ; or why the same constituents should
assume the form of augite in some rocks, and hornblende
in other rocks. We are hedged in by ignorance; and
perhaps one of our chief dangers, becoming with some
people a besetting sin, is that of pretending to know more
than we are at present in a position to know. Our very
analogies by which we endeavour to make clear our mean-
ing may often seem to imply an unwarrantable assumption
of knowledge.

In the last chapter I used the term " organic combina-
tion," and drew a chemical analogy. I wished to indicate
the particularity and the stability of certain variations, and
the possibility of new departures through new combinations
of variations, the new departure not being necessarily any-
thing like a mean between the combining variations.* I
trust that this will not be misunderstood as a new chemico-
physical theory of organic forms. I have some fear lest I
should be represented as maintaining that a giraffe or a
peacock is a definite organic compound, with its proper

* See Darwin, " Animals and Plants under Domestication," vol. ii. p. 252.

Organic Evolution. 241

organic form, in exactly the same way as a rhombohedron
of calcite or a rhombic dodecahedron of garnet is a definite
chemical compound, with its proper crystalline form. All
that the analogy is intended to convey is that variations
seem, under certain circumstances, to be definite and stable,
and may possibly combine rather than commingle.

\

Summary and Conclusion.

It only remains to bring this chapter to a close with a
few words of summary and conclusion.

The diversity of animal life must first be grasped. We
believe that this diversity is the result of a process or
processes of evolution. Evolution is the term applied tojj
continuity of development. It involves adaptation ; and
adaptation to an unchanging environment may become
more and more perfect. But the environment to which
organisms are adapted also changes. Where thp, change is
in the direction of complexity, we have elaboration ; where
it is in the direction of simplicity, we have degeneration, [
Of these elaboration is the more important. It involves
both a tendency to differentiation giving rise to indi-
viduality, and a tendency to integration giving rise to
association. Continued elaboration is progress ; and this
is opposed to degeneration.

The factors of evolution fall under two heads — origin
and guidance. The origin of variations lies in mechanical
stresses, and chemical or physical influences. Whether
these act on the body (and are transmitted by inheritance)
or only on the germ, is a question which divides biologists
into two schools. In the latter case all variations are fortui-
tous ; in the former the development of tissue-variations
has been in direct response to the physical or chemical
influences. There are, however, in any case fortuitous
combinations of variations.

Whether use and disuse are factors of origin is also a
debatable point. Those who believe that physical influences

242 Animal Life and Intelligence.

on the body are transmissible believe also that the effects
of use and disuse are transmissible.

The vital vigour of the organism is a determining con-
dition of importance. The vital vigour of males has
favoured the origin of secondary sexual characters ; that of
females, the fostering and protection of young, and therefore
the development in them of vital vigour.

The almost universally admitted factor in guidance is
natural selection. But we must be careful not to use it
as a mere formula.

Whether sexual selection is also a factor is still a matter
of opinion. Without it the specific character and constancy
of secondary sexual features are at present unexplained.
If inherited use and disuse are admitted as factors in
origin, they must also be admitted as important factors in
guidance.

Questions of origin and guidance should, so far as is
possible, be kept distinct. These terms, however, apply to
the origin and guidance of variations. In the origin of
species guidance is a factor, no doubt a most important
factor. The title of Darwin's great work was, therefore,
perfectly legitimate. And those who say that natural
selection plays no part in the origin of species are, there-
fore, undoubtedly in error.

243 )

CHAPTEE VII.

THE SENSES OF ANIMALS.

IT is part of the essential nature of an animal to be recep-
tive and responsive. The forces of nature rain their
influence upon it ; and it reacts to their influence in certain
special ways. Other organisms surround it, compete with
it, contend with it, strive to prey upon it, and occasionally
lend it their aid. It has to adjust itself to this complex
environment.

There are two kinds of organic response — one more or
less permanent, the other temporary and transient. We
have already seen something of the former, by which the
tissues (the epidermis of the oarsman's hand, and the
muscles of his arm) respond to the call made upon them.
The response is here gradual, and the effects on the
organism more or less enduring. This, however, is not
the kind of response with which we have now to deal.
What we have now to consider is that rapid response,
transient, but of the utmost importance, by means of which
the organism directly answers to certain changes in the
environment by the performance of certain activities. The
parts specially set aside and adapted to receive special
modes of influence of the environment are the sense-
organs. We human folk get so much pleasure from and
through the employment of our sense-organs, that it is
important to remember that the primary object of the
process of reception of the influences from without was not
the aesthetic one of ministering to the enjoyment of life by
the recipient organism, but the essentially practical one of
enabling that organism to respond to these influences. In

244 Animal Life and Intelligence.

other words, the raison d'etre of the sense-organs is to set
agoing suitable activities — activities in due response to
the special stimuli.

In this chapter we shall consider the modes in which
the special sense-organs are fitted to receive the influences
of the environment, deferring to a 'future chapter the con-
sideration of the resulting activities. For the present we
take these activities for granted, observing them only in so
far as they give us a clue to the sense-reaction by which
they are originated. In this chapter, too, we shall deal,
for the most part, with the physiological aspects of sensa-
tion. In all other organisms than ourselves, that is to say,
than each one of us individually for himself, the psycho-
logical accompaniments of the physiological reactions of
the sense-organs are matters of inference. Still, so closely
and intimately associated are the physiological and the
psychological aspects, that the exclusion of all reference to
the latter would be impracticable, or, if practicable, unad-
visable. What is practicable and advisable is to remember
that, even if the two are mentioned in a breath, the physio-
logical and the psychological belong to distinct orders of
being.

In addition to the time-honoured "five senses," there
are certain organic sensations, so called, which take their
origin within the body. These are, for the most part,
somewhat vague and indefinite. They do not arise imme-
diately and in direct response to changes in the environ-
ment, but indicate conditions of the internal organs. Such
are hunger, thirst, nausea, fatigue, and various forms of
discomfort. Although they are of vital importance to the
organism, prompting it to perform certain actions or to
desist from others, they need not detain us here.

More definite than these, but still of internal origin, is
the muscular sense. This, too, is of continual service to
every active animal. By it information is given as to the
energy of contraction of the muscles, and of the amount of

The Senses of Animals. 245

movement effected — not to mention the rapidity and dura-
tion of the muscular effort. By it the position, or changes
of position, of the motor-organs are indicated. It is
obvious, therefore, that the sensations obtained in this way,
some of which are exceedingly delicate, are an important
guide to the organism in the putting forth of its activities.
It is through the muscular sense that we maintain an
upright position. It is through an educated and refined
muscular sense that the juggler and the acrobat can
perform their often surprising feats. Concerning the
physiology of the muscular sense, we have at present no
very definite knowledge. Some have held that we judge of
muscular movements by the amount of effort required to
initiate them ; but it is much more probable that there are
special sensory nerves, whose terminations are either in
the muscles themselves or in the membranes which sur-
round them.

We come now to the special senses. Of these we will
take first the sense of touch. Through this sense we are
made aware of bodies solid or liquid (or perhaps gaseous)
which are actually in contact with the skin or its infold-
ings at the mouth, nostrils, etc. There are considerable
differences in the sensitiveness of the skin in different parts
of its surface ; some parts, like the filmy membrane which
covers the eye, being very sensitive, while others, like the
horny skin that covers the heel of a man who is accustomed
to much walking, are relatively callous. Different from
this is the delicacy of the sense of touch. This delicacy is
really the power of discrimination, and therefore involves
some mental activity. But it is also dependent upon the
distribution of the recipient end-organs of the nerve. The
highest pitch of delicacy is reached in the tip of the tongue,
which is about sixty times as delicate as the skin of the
back. The power of discrimination is tested in the follow-
ing way : The points of a pair of compasses are blunted,
and with them the skin is lightly touched. When the
points are close together, the sensation is of one object;

246 Animal Life and Intelligence.

when they are more divergent, each point is felt as distinct
from the other. On the thigh and in the middle of the
back, two distinct points of contact are not felt unless the
compass-tips are about 2J inches (67'7 millimetres) apart.
When the divergence is 2 inches, they are felt as one.
With the tip of the tongue, however, we can distinguish the
two separate points when they are only ^ of an inch (1*1
millimetre) apart. For the finger-tip the distance is
about ^ of an inch (2 millimetres) ; for the tip of the nose,
about | of an inch (6 '8 millimetres) ; for the forehead, a
little less than an inch (22'6 millimetres) ; and so on.
Shut your eyes, and allow a friend to draw the compass
with the points about £ an inch apart, from the forehead
to the tip of your nose, or (setting the points about £ of an
inch apart) from the ball of your thumb to the finger-tip.
The increasing delicacy and power of discrimination is
readily felt, and it is difficult to believe that the compasses
are not being slowly opened.

It is beyond the purpose of this chapter to describe
minutely the nature and structure of the nerve-ends in
the sense-organs. This is a matter of minute anatomy, or
histology. A full description of them as they occur in
man will be found in any standard text-book of physiology ;
while Sir John Lubbock's " Senses of Animals " gives
much information concerning, and many illustrations of,
the minute structure of the sense-organs in the inverte-
brates. Here I can only touch very briefly on some of the
more important points.

One of the larger nerves of the body (e.g. the sciatic
nerve), consists of a bundle of nerve-threads collected from
a considerable area ; some of these (motor threads) end in
muscles, others (sensory threads) in the skin or its neigh-
bourhood. Each nerve-thread has a central axis-fibre,
which is surrounded by a fatty, insulating medullary sheath,
and this by a delicate primitive sheath. In some parts
of the skin the sensory nerve-threads lose their medullary
sheath, and end in very fine branches between the cells of
the tissue. In other cases the cells near their termination

The Senses of Animals.

247

are specially modified to form tactile cells, or tactile
corpuscles, in contact with or surrounding the axis-fibre or
its expansion (Fig. 23).

Hairs are delicate organs of touch, though, of course,

Fig. 23.— Tactile corpuscles.
1. In the beak of a goose. 2. In the finger of a man. 3. In the mesentery of a cat.

this is not their only function. They act as little levers
embedded in the skin.

Turning now to the vertebrate animals other than
man, we find in them a sense of touch closely analogous
to our own. As in us, so in them, 'the specially mobile
parts are eminently sensitive and delicate; for instance,
the lips in many animals, such as the horse, and the finger-
like organ at the end of the elephant's trunk. In some of
them special hairs are largely developed as organs of touch,
as in the whiskers of the cat and the long hairs on the
rabbit's lip. With the aid of these the rabbit finds its way
in the darkness of its burrow ; and it is said that, deprived
of these organs, the poor animal blunders about, and is
unable to steer its course in the dark.

The wing of the bat is very sensitive to touch ; and it
is supposed that it is through this sense that the bat is
able to direct its course in the darkness of caves. Miss
Caroline Bolton thus describes an experimental trial of
this power of the bat at which she was herself present.
A room, about twenty feet by sixteen, was arranged with
strings crossing each other in all directions so as to form a
network with about sixteen inches space between the strands.
To each string was attached a bell in such a way that the
slightest touch would make it ring. One corner of the room

248 Animal Life and Intelligence.

was left free for those who were present at the experiment.
A bat, measuring about one foot from the tip of one wing
to that of the other, was let loose in the room when it was
quite dark, " and it was distinctly heard flying about all
over the room, but never once did it touch a string or stop
flying. It several times came quite near to the spectators,
so that they could feel the vibration of the air in their faces.
The experiment was continued for half an hour. Then,
when the door was opened and light let in, the bat stopped
flying, and settled down in the darkest corner." Now,
here it may be said that, although the room was dark to
human spectators, there may have been light enough for
a bat to see his way. The cruel experiments of Spalanzani,
however, who put out the eyes of bats and obtained a
similar result, seem to show that the animal is guided by
some sense other than that of sight.

The crustaceans and many insects are covered with a
dense armour, and it might be supposed that in them
there could be no sense of touch. But this sense is by
no means absent. Seated on the
tough integument are delicate little
hairs, to the base of which a nerve-
fibril passes through a perforation in
the integument. These are specially
numerous in the antennae of insects.
In yet lower organisms we know
in some cases the manner in which
°f they are sensitive to touch; but in
<JL, touchr;'™, cnticie; a great number of cases, although
observation shows that they are thus
sensitive, we know nothing definite
3$i 'STiSmySS, as to how the surface is specially
fitted to receive the stimuli. Even

the primitive amoeba, however, is sensitive in the sense
spoken of on p. 8 ; that is to say, it reacts under the
influence of a stimulus.

Closely associated with the sense of touch is the

The Senses of Animals. 249

temperature-sense. Goldschneider and others have shown
that on the skin of the human hand, for example, there are
special points that are sensitive to heat and cold. Some
of these little specialized areas are sensitive to cold;
others are sensitive to heat ; and neither of these seem to
be sensitive to pressure. It therefore seems probable that
special nerve-fibrils are set apart for the temperature-
sense ; but of the manner in which these fibrils terminate
little or nothing is known.

Let us note that this temperature-sense, unlike the
sense of touch, may make us aware of distant bodies. It
is, tl^n, what we may term a tekesthetic sense in contra-
distinction to a contact-sense. It is stimulated by a
molecular throb; the throbbing body may be in contact,
but it may be as distant as the sun, in which case the
molecular pulsations are brought to us on waves of sether.
Whether these waves act directly on the nerve end-organs,
or indirectly on them through the warming of the skin-
surface in which they terminate, we cannot say for certain.
But if the hand be held before a heated stove and be
sheltered from the heat by a screen, the removal of the
screen, even for the fraction of a second, gives rise to a
strong stimulation of the temperature-sense, though the
skin-surface be not appreciably raised in temperature.
Hence it is probable that the end-organs are stimulated
directly, and not indirectly.

Concerning the temperature-sense in the lower animals,
nothing definite is known. But it is impossible to see our
familiar pets basking in the sunshine, or a butterfly sunning
itself on a bright summer's day, without feeling confident
that the temperature-sense is a channel of keen enjoy-
ment. As before mentioned, however, this is not to be
regarded as the primary end in sensation. The primary
end is not life-enjoyment, but life-preservation. And we
must regard the temperature-sense as developed in the
first instance to enable the organism to escape from the
ill effects of deleterious heat or cold, and to seek those
temperature -conditions which are most helpful to the

250 Animal Life and Intelligence.

continued and healthful fulfilment of the process of
life.

The sense of taste is called into play by certain soluble
substances, or liquids, which must come in contact with
the specialized nerve-endings. Under normal circum-
stances, the sense of taste is closely associated with that
of smell, the result of the combination of the two special
senses being a flavour. The bouquet of a choice wine, the
flavour of a peach, involve both senses ; quinine involves
taste alone ; and garlic and vanilla are nearly, if not quite,
tasteless, — what we call their taste is in reality their action
on the organ of smell.

It is difficult to classify tastes. Sweet, bitter, salt,
alkaline, sour, acid, astringent, acrid, — these are the pro-
minent and characteristic varieties.

This sense is generally localized in or near the mouth ;
in us mainly in the tongue. One manner, but not the only
manner, in which the nerves in this region terminate is
in the minute flask-shaped taste-buds, which have near
one end, where they reach the surface, a funnel-shaped
opening, the taste-pore. They are made up of elongated
cells, some of which near the centre
are spindle-shaped, and are called
taste-cells. They are found chiefly
round the large circumvallate papillae ;
but in the rabbit and some other
animals they are collected in the
folds of a little ridged or pleated patch
—the papitta foliata— on each side
section across part of the of the tongue near the cheek-teeth.
ta8te-budsafarther eniargei * ' It is probable that the stimulation

of the end-organs of taste is effected by the special mode of
molecular vibration due to the chemical nature of the
sapid substance. Mr. J. B. Haycroft, in a paper read
before the Koyal Society of Edinburgh,* suggests that " a
group of salts of similar chemical properties have their

* See abstract in Nature, vol. xxxiv. p. 515.

The Senses of Animals. 251

molecules in a similar vibrating condition, giving rise to
similar colours and similar tastes." " Thus the chlorides
and sulphates of a series of similar elements — called a
group of elements by Mendeljeff — have similar tastes."

The delicacy of the sense of taste in man has been the
subject of investigation by Messrs. E. H. S. Bailey and
E. L. Nichols.* They give the following table : —

L Quinine —

Male observers detected 1 part in 390,000 parts of water.
Female „ „ 1 „ 456,000 „

II. Cane-sugar —

Male observers „ 1 „ 199 „ „

Female „ „ 1 „ 204 „ „

III. Sulphuric acid-

Male observers „ 1 „ 2,080 „ „

Female „ „ 1 „ 3,280 „

IV. Bicarbonate of sodium —

Male observers „ 1 „ 98 „ „

Female „ „ 1 „ 126 „ „

V. Common salt —

Male observers „ 1 „ 2,240 „

Female 1

The above figures represent means or averages of a
great number of individuals. There was very considerable
variation for some tastes. In the case of the bitter of
quinine, the maximum delicacy was the detection of 1 part
in 5,120,000 parts of water; the minimum 1 part in
456,000 parts of water. Except in the case of salt, the
sense was more delicate in women than in men. It is not
stated whether the men tested were smokers.

It does not seem necessary to say anything concerning
the sense of taste in the lower mammalia.

In birds and reptiles the sense of taste does not appear
to be highly developed. Parrots are, perhaps, better off
in this respect than the majority of their class ; and the
ducks have special organs on the edges of the beak, which
seem to minister to this sense. A python at the Zoological
Gardens, partially blind owing to a change of skin, is said
to have struck at an animal, but to have only succeeded

* See Nature, vol. xxxvii. p. 557.

252 Animal Life and Intelligence.

in capturing its blanket. This, however, it constricted,
and proceeded to swallow with abundant satisfaction.

It may here be mentioned that the scales and skua of
many fishes are provided with sense-organs which very
closely resemble the taste-buds of higher animals. They
occur in the head and along the " lateral line " which runs
down the side of the fish, and may be readily seen, for
example, in the cod. Mr. Bateson's * careful observations
at Plymouth gave, however, no indication of the possession
of an olfactory or gustatory function, and their place in
the sensory economy of the fish remains problematical. In
or near the mouth similar end-organs are found to be some-
what variously developed in different fishes — on the palate
and lips, on the gill-bars, more rarely on the tongue, and on
the barbels of the rockling and the pout. How far any or all
of these have a gustatory function remains to be proved.

Anglers and fishermen, however, from their everyday
experience, and naturalists from special observations, do
not doubt that fishes have a sense of taste. Professor
Herdman's recent experiments on feeding fishes with nudi-
branchs | (naked molluscs) seem to show, for example, that
the fishes concerned, including shannies, flat-fish, cod,
rockling, and others, have a sense of taste leading them
to reject these molluscs as nasty. They show, too, that
some of the nudibranchs (Doris, Ancula, Eolis) are pro-
tected by warning coloration.

Our knowledge of the sense of taste among the lower
(invertebrate) animals is imperfect, and is largely based
rather on observation of their habits than on the evidence
of anatomical structure. Here, again, comes in the
difficulty of distinguishing between taste and smell. But
even if the caterpillars which refuse to eat all but one or
two special herbs, or the races of bloodsuckers which seem
to have individual and special tastes, are guided in part
by an olfactory sense, there is much evidence which seems

* " Sense-Organs and Perception of Fishes : " Journal of Marine Bio-
logical Association, New Series, vol. i. No. 3, p. 225.
t Nature, vol. xlii. p. 201.

The Senses of Animals. 253

to admit of no alternative explanation. Moisten, for
example, the antennae of a cockroach with a solution of
Epsom salts or quinine, and watch him suck it off; or
repeat F. Will's experiments on bees, tempting them with
sugar, and then perfidiously substituting pounded alum.
The way in which these little insects splutter and spit
suggests that, whatever may be the psychological effect,
the physiological effect is analogous to that produced in
us by an exceedingly nasty taste. Here smell would seem
to be excluded. Forel, moreover, mixed strychnine with
honey, and offered it to his ants. The smell of the honey
attracted them, but when they began to feed, the effect of
the taste was at once evident.

The organs of taste in insects are probably certain
minute pits, in each of which is a delicate taste-hair,
which, in some cases, is perforated at the free end. They
occur in the maxillae and tongue in ants and bees, and on
the proboscis of the fly.

In many of the invertebrates, the crayfish and the earth-
worm, for example — to take two instances from very different
groups — observation seems to show that a sense of taste is
developed, for they have marked and decided food-pre-
ferences. Nevertheless, the existence of special organs for
this purpose has not been definitely proved.

The sense of taste no doubt ministers to the enjoyment
of life. But, presumably, it has been developed in sub-
servience to the process of nutrition. Primarily, taste was
not an end in itself, but was to guide the organism in its
selection of food that could be assimilated. Nice and nasty
were at first, and still are to a large extent, synonymous
with good-for-eating and not-good-for-eating. With un-
wonted substances, however, its testimony may be false.
Sugar of lead is sweet, but fatal. Brought to a new
country, cattle often eat, apparently with relish, poisonous
plants. Still, under normal circumstances, the testimony
of taste is reliable.

The sense of smell is, to a large extent, telaesthetic. It

254 Animal Life and Intelligence.

is true that the stimulation of the end-organs is effected by
actual contact with the odoriferous vapour. But since this
vapour may be given off from an odoriferous body at some
distance from the organism, such as a flower or a decom-
posing carcase, it is clear that the sense gives information
of the existence of such bodies before they themselves come
in contact with us. Primitively, we may suppose that it
was developed in connection with that sense of taste with
which, as we have seen, it is so closely associated. In this
respect smell is a kind of anticipatory taste. But it has
now other ends, apart from those which are purely aesthetic.
In us it may serve as a warning of a pestilential atmo-
sphere ; in many organisms, such as the deer, it gives
warning of the presence of enemies ; in many again, and
some insects among the number, it is the guiding sense in
the search for mates.

The organ of smell in ourselves and in all the mammalia
is the delicate membrane that covers the turbinal bones in
the nose. It contains cells with a largish nucleus, around
which the protoplasm is mainly collected. A filament
passes from this to the surface, and ends in a fine hair or
cilium (or a group of hairs or cilia in birds and amphibia) ;
a second filament runs downwards into the deeper parts of
the tissue, and may pass into a nerve-fibril.

In us and air-breathing creatures, the substance which
excites the sensation of smell must be either gaseous or in
a very fine state of division; but in water-breathers the
substance exciting this sensation — or, in any case, one of
anticipatory taste — may be in solution. The sensitiveness
of the olfactory membrane is very remarkable. A grain of
musk will scent a room for years, and yet have not sensibly
lost in weight. Drs. Emil Fischer and Penzoldt found
that our olfactory nerves are capable of detecting the
*67To~ow P8-1* °f a milligramme of chlorophenol, and the
4^<Joooooo Par* °f a milligramme, or about one thirty-
thousand-millionth of a grain, of mercaptan. It may be
that to such substances our olfactory sensibility is especially
delicate.

The Senses of Animals. 255

Not much is known concerning the manner in which
the end-organs of smell are stimulated. As in the case of
taste, it is probably a matter of molecular vibration ; and
Professor William Bamsay has suggested that the end-
organs are stimulated by vibrations of a lower order than
those which give rise to sensations of light and heat. He
has also drawn attention to the fact that to produce a
sensation of smell, the substance must have a molecular
weight at least fifteen times that of hydrogen.

It is well known that the sense of smell is in some of
the mammalia exceedingly acute. The dog can track his
master through a crowded thoroughfare. The interesting
experiments of Mr. Eomanes * show that, under ordinary
conditions of civilized life, the smell of boot-leather is a
factor/and the dog tracks his master's boots. In one case,
the boots were soaked in oil of aniseed, but this to us
powerful scent did not overcome the normal odour of
the master's boots. Mr. W. J. Eussell, in a subsequent
number of the same periodical, describes how his pug could
find a small piece of biscuit by scent, and this odour of
biscuit was not overmastered by a strong smell of eau-de-
Cologne. Deer-stalkers know well how keen is the sense
of smell in the antlered ruminants.

We must not, however, be too ready to conclude, from
these observations, that the olfactory membrane is absolutely
more sensitive in such animals than it is in man. It may
well be that, though they are so keen to detect certain
scents, they are dull to those which affect us power-
fully. It is quite possible that the odour of aniseed or
eau-de-Cologne is — possibly from the fact that iheir end-
organs are not attuned to these special molecular vibrations
— out of their range of smell. Their special interests in
life have led to the cultivation of extreme sensibility to
special tones of olfactory sensation. Under unusual cir-
cumstances, man may cultivate unwonted modes of utilizing
the sense of smell. A boy, James Mitchell, who was born
blind, deaf, and dumb, and who was mainly dependent on

* Nature, vol. xxxvi. p. 273.

256 Animal Life and Intelligence.

the sense of smell for keeping up some connection with the
external world, observed the presence of a stranger in the
room, and formed his opinion of people from their charac-
teristic smell. On the whole, therefore, we may, perhaps,
conclude that the variations in sensitiveness are mainly
relative to the needs of life.

In birds the sense of smell is but little developed, not-
withstanding all that most interesting naturalist, Charles
Waterton, wrote on the subject. Vultures seem unable to
discover the presence of food which is hidden from their
sight. Probably reptiles share with them this dulness of
the sense of smell.

It has already been remarked that, in the case of
aquatic animals, there is probably little distinction between
taste and smell. It would be well, perhaps, to restrict the
word " smell " to the stimuli produced by vapours or air-
borne 'particles, and to use the phrase " telaesthetie taste,"
or simply " taste," for those cases where the effects are
produced through the medium of solution. In this case,
however, the point to be specially noticed is that taste in
aquatic animals becomes a telaesthetic sense, informing the
organism of the presence of more or less distant food.
Thus, if you stir with your finger the water in which
leeches are living, they will soon flock to the spot, showing
that the telsesthetic sense is associated with an appreciation
of direction. If a stick be used to stir the water, they do not
take any notice of it. Mr. W. Bateson * has shown that
there are many fishes, among which are the dog-fish,
skate, conger eel, rockling, loach, sole, and sterlet, which
habitually seek their food by scent (telaesthetic taste), aided
to some extent by touch, and but little, if at all, by sight.
" None of these fishes ever starts in quest of food when it is
first put into the tank, but waits for an interval, doubtless
until the scent has been diffused through the water.
Having perceived the scent of food, they swim vaguely
about, and appear to seek it by examining the whole area
pervaded by the scent, having seemingly no sense of the

* Journal of Marine Biological Association, New Series, vol. i. No. 3, p. 235.

The Senses of A nimals. 257

direction whence it proceeds." I venture to think that
further observation and experiment may show that such a
sense of direction does in some cases exist. Some years
ago I was fishing in Simon's Bay, at the Cape, with a long
casting-line. The sea was unusually calm, and the water
clear as crystal. Beneath me was a clear patch of granite,
two or three yards across, surrounded by tangled seaweed.
Evening was coming on, and I was just going to put up
my tackle when I saw a long dark fish slowly sail into the
open space and take up his position at one side. My line
was out, baited, I think, with a piece of cuttle-fish, and I
tried to draw it into the clear space, but only succeeded
in bringing it to within a foot or so of the side furthest
from the fish. There it got hitched in the weed ; but the
fish being still undisturbed, I awaited further developments.
After two or three minutes the fish slowly turned, crossed
the pool, and remained motionless for a few moments ;
then he proceeded straight to the bait ; and in a few
minutes I had landed a dog-fish between four and five feet
long. I did not then know that the dog-fish sought its
food mainly or solely by scent (taste) ; but in any case I do
not think in this instance he could have seen the bait,
hidden as it was amid the seaweed.

Although I am aware, and have already mentioned,
that Mr. Bateson's observations do not support the view
that the sense-organs of the lateral line minister to this
telsesthetic sense, still I think that further observations
and experiments may show that these sense-organs are
" olfactory," and that the lateral development may be in
relation to the appreciation of the direction in which the
food lies. It is, however, a difficult matter to determine,
and the few experiments I have made are so far incon-
clusive.

Much has been written concerning the sense of smell in
insects. That they possess such a sense few will be dis-
posed to doubt. The classical observations of Huber show
that bees are affected by the smell of honey, and that the
penetrating odour of fresh bee-poison will throw a whole

258 Animal Life and Intelligence.

hive into a state of commotion. He was of opinion that
the impunity with which his assistant, Francis Burnens,
performed his various operations on bees was due to the
gentleness of his motions, and the habit of repressing his
respiration, it being the odour transmitted by the breath to
which the bees objected. Sir John Lubbock formed a little
bridge of paper, and suspended over it a camel's-hair brush
containing scent, and then put an ant at one end. She
ran forward, but stopped dead short when she came to the
scented brush. Dr. McCook introduced a pellet of blotting-
paper saturated with eau-de-Cologne into the neighbour-
hood of some pavement-ants, who were engaged in a free
fight. The effect was instantaneous ; in a very few seconds
the warriors had unclasped mandibles, relaxed their hold
of their enemies' legs, antennae, or bodies.

The correct localization of the sense of smell has been
a matter of difficulty. Kirby and Spence localized it at
the extremity of the " nose," between it and the upper lip.
That the nose, they naively remark, corresponds with the
so-named part in mammalia, both from its situation and
often from its form, must be evident to every one who looks
at an insect. Lehman, Cuvier, and others, misled by the
fact that the organ of smell is in us localized at the
entrance of the air-track, supposed that at or near the
spiracles of insects were the organs of smell. Modern
research tends more and more clearly to localize the sense
of smell, as first suggested by Eeaumur, in the feelers or
antennae, and in some cases also in the palps. If the
antennae of a cockroach be extirpated or coated with
paraffin, he no longer rushes to food, and takes little notice
of, and will sometimes even walk over, blotting-paper
moistened with turpentine or benzoline, which a normal
insect cannot approach without agitation. There can be
little doubt that it is by means of its large branching
antennae that the male emperor moth (Saturnia carpini) is
able to find its mate.* If a collector take a virgin female

* Mr. S. Klein mentions a similar fact in connection with Bombyx quercus
(Xature, voL xxxv. p. 282).

The Senses of Animals.

259

into a locality frequented by these moths, he will soon be
surrounded by twenty or thirty males; but if the moth
be not a virgin, he will at most see one or two males.
The sense of smell is thus delicate enough to distinguish
the fertilized from the unfertilized female, and has asso-
ciated with it a sense of direction by which the insect is
guided to the right spot. Carrion flies whose antennas
have been removed fail to discover putrid flesh; and E.
Hasse has observed that male humble-bees whose antennae
have been removed cannot discover the females. The
sensory elements are lodged in pits or cones, which may be
filled with liquid, peculiar sensory rods or hairs being
associated with the nerve-end-
ings. Of these pits the queen-
bee has, according to Mr.
Cheshire, 1600, the worker 2400,
and the drone nearly 19,000, on
each antennae. On the antennae
of the male cockchafer, Hauser
estimates the number to be
39,000.

In the aquatic crayfish there
are, besides the long antennas,
smaller antennules, each of
which has two filaments, an
inner and an outer. On the
under surface of most of the
joints of the outer filament
there are two bunches of
minute, curiously flattened or-
gans, which were regarded by Fig' 26-Antennule otoayflah.

? ,. ,, . ,. 6 ' J *J- inner joint; o.j., outer joint; ol.,

.Leyd.lg, their diSCOVerer as olfactory set*; ol'., the same, enlarged;

/ & ° au,op., auditory opening in the basal di-

oliactory. Observation, too vision> which has been cut °Pen to show

' au.s., the auditory sac; au.n., auditory

seems to confirm the view that nervebranchiDgtothetworidge8besetwith

aal auditory hairs; au.h., auditory hair, en-

the sense of smell (or telaas- larsed- (After Howes.)
thetic taste) is located in the antennule. I tried on a
crayfish the following experiment: When it was at rest
at the bottom of its tank, I allowed a current of pure

260 Animal Life and Intelligence.

water (the water in which it lived) to flow from a pipette
over its antennas and antennules. The antennae moved
slowly, but the antennules remained motionless. I then
took some water in which a cod's head had been boiled,
and allowed some of this to stream over the antennas and
antennules. The former moved slightly as before, but the
antennules were thrown into a rapid up-and-down jerky
vibration, and shortly afterwards the crayfish began moving
about the bottom of its tank. If only one antennule be
thus stimulated, or stimulated to a higher degree than the
other, the crayfish seems generally (but not always) to
turn to that side in search of food. Mr. Bateson * has
shown to how large an extent shrimps and prawns seek their
food by smell, and states that a prawn, though blind, will
often find his way back to his proper place, and stay in it.
In the snail the anterior pair of " horns," or tentacles,
are said to be olfactory. Near the end of each is a large
ganglion, or nerve-knot, from which fibres pass to the
surface, in which there are said to be developed sensory
knobs. Snails, however, from which these tentacles have
been removed are apparently still possessed of a sense of
smell. Certain lobed processes round the mouth have
been regarded as the seat of olfactory sensation, but this
is doubtful. In the foot of the snail, the part on which
it glides, there is a hollow gland, and in this there are
special cells, each of which gives off a delicate rod, en-
larging at the free end into a ciliated knob. These are
regarded as sensory and, it may be, olfactory. In shell-
fish like the mussel, in which the water is sucked in by
an inhalent tube or siphon, and ejected through an ex-
halent siphon above it (see Fig. 2, p. 4), there is at the
entrance of the incoming current a thin layer of elongated
cells which are described as olfactory, and are in association
with a special ganglion. Olfactory depressions have been
described in some worms. But in a great number of the
lower invertebrates very little or nothing is known concern-
ing a sense of smell.

* Journal of Marine Biological Association, New Series, vol. i. No. 2, p. 211.

*

') i'
The Senses of Animals. 261

Hearing is a telassthetic sense. Through it we become
aware of certain vibratory states of more or less distant
objects. The vibrations of these bodies are transferred to
the air or other medium surrounding the body, and are
transmitted through the air or other medium to the ear.
The sound-waves traverse the air at a rate of 337 metres
(1106 feet) in a second ; but they travel about four times
as fast in water. If the vibration is periodic or regular,
the sound is called a tone ; non-periodic or irregular sounds
are noises. The pitch of a tone is determined by the
number of vibrations in a second. The lowest or gravest
tone most of us can hear is that where there are about 30
vibrations in a second ; twice this number give us a tone
of an octave higher ; twice this again, another octave ; and
so on. In musical composition, tones from about 40 to
about 4000 vibrations per second are employed. This is
a range of somewhat over six octaves. But many of us
are capable of hearing sounds over a range of about ten
octaves, that is to say, from 30 to 30,000 vibrations per
second. The upper limit of hearing is, however, very
variable. Some people are deaf to tones of more than
15,000 or 20,000 vibrations per second.* Others may hear
shrill tones of 40,000, or even in rare cases 50,000. I
could as a boy hear the shrill squeak of a bat ; now I am
quite deaf to it. A friend of mine in South Africa was
unable to hear the piping of the frogs in the pond, which
was to me so loud as almost to drown the tones of his
voice.

Apart from the pitch of a note is its quality. The
same note struck on different instruments or sung by
different persons has a different ring. This is determined
by the number and intensity of overtones, or partials, which
are associated with the fundamental tone. Suppose the
deep fundamental tone of 33 vibrations be sounded ; with it
there may be associated overtones, eight or nine in number,
all of which are simple multiples (twice, thrice, four times,

* A friend of mine informs me that his limit is about 17,500 per second,
20,000 being quite inaudible.

262 Animal Life and Intelligence.

and so on) of the fundamental 33. The effects of these
on the organ of hearing fuse or combine with the pre-
dominant effect of the fundamental tone. In harmonious
chords, also, two or more fundamental tones, with their
accompaniment of partials, blend in sensation so com-
pletely that it requires a keen musical ear and some
training to analyze them into their component elements.

The delicacy of discrimination of tones is greatest in
the mid-region of hearing ; and there is much individual
variation in accuracy of ear. I have made experiments on
many individuals to test their powers in this respect. I
found some who were unable, in the mid-region of hearing,
to state which was the higher of two notes sounded on a
violin, the tones of which were separated by a major third,
and in one case by a fifth. With notes on the piano the
discrimination was more delicate, and yet more delicate
when the notes were sung. In such cases tone-discrimina-
tion is deficient ; and between these and the musician, who
is stated to be able to distinguish tones separated by only
6*f of a tone, there are many intermediate stages.

It is beyond my purpose to describe, in more than a
very general way, the nature of the auditory apparatus of
man. The vibrations of the air are received by the drum-
membrane, which lies in the auditory passage. From this
it is transmitted, by a chain of small bones, to the inner
auditory apparatus. This consists of two small mem-
branous sacs, with one of which three membranous looped
tubes, the semicircular canals, are connected; with the
other is connected a spiral tube, the cochlear canal. These
membranous sacs and canals are filled with fluid, and are
surrounded by the fluid which fills the bony cavity in
which they lie. This bony cavity has two little windows,
one oval and the other round, across each of which a
membrane is stretched. The oval membrane is in con-
nection with the chain of auditory bones ; and when this
is made to vibrate in and out, the membrane of the round
window vibrates out and in. Thus the fluid around and
within the membranous sacs and canals is set in vibration.

The Senses of Animals. 263

And the parts are so arranged that the vibrations, in
passing from the oval to the round membrane/' must run
up one side and down the other side of the cochlear canal.
As they run down they set in vibration a delicate mem-
brane which is supported on beautiful arched rods (the

c. c

Fig. 27.— Diagram of ear.

t.m., tympanic membrane, to which is attached a chain of small bones stretching across
the cavity of the drum, the innermost of which, St., fits into the " oval window." The vibra-
tions are transmitted up one side and down the other side of the cochlear canal, c.c., and thus
reach the " round window," f.r. ; s.c. is one of the semicircular canals, the other two are
omitted ; e.t. is the Eustachian tube connecting the cavity of the drum with the mouth-cavity.

organs of Corti). And this membrane contains a number
of special hair-cells, so called because they bear minute
hair-like structures. These are the special end-organs of
hearing. It has been suggested that the fibres of the
membrane on the arched rods, which are of different
lengths and may be stretched with differing degrees of
tension, respond to vibrations of different pitch. Thus the
hair-cells on that particular part of the membrane would
be stimulated, and the note might be appreciated in its
true position in the scale.

We must now pass on to consider the sense of hearing
in animals. That the mammalia have this sense well
developed is a matter of familiar observation, and in some
of them, such as the horse and the deer, it is exceedingly

264 Animal Life and Intelligence.

acute. The form and movements of the external ear also
enable many of the mammalia to collect and attend to
sounds from special directions. The mammalia possess
also the power of tone-discrimination, as is shown by the
fact that our domesticated animals recognize different
modulations of the human voice, and that wild creatures
distinguish tones or noises of different quality. A New-
foundland dog, possessed by a friend of mine, always
howled when the tenor D was struck on the piano, or sung.
And Theophile Gautier reports that one of his cats could
not endure the note G, and always put a reproving and
silencing paw on the mouth of any one who sang it.

In birds the sense of hearing is not only very sensitive,
but the power of discrimination is exceedingly delicate.
No one who has watched a thrush listening for worms can
doubt that her ear is highly sensitive. The astonishing
accuracy with which many birds imitate, not only the song
of other birds, but such unwonted sounds as the clink of
glasses or the ring of quoits, shows that the delicacy in
discrimination has reached a high level of development.
In birds, however, the cochlear canal has not the same
development that it has in mammals, and there are no
arched rods — no organs of Corti.

Nothing special is to be noted concerning the sense of
hearing in the reptiles, amphibia, and fishes. In all (with
the exception of the lowly lancelet) the auditory organ is
developed. We shall, however, presently see reason to
question whether the possession of an " auditory organ,"
with well-developed semicircular canals,necessarilyindicates
the power of hearing. And Mr. Bateson's recent experi-
ments at Plymouth* seem to indicate that fishes are not so
sensitive in this respect as anglers f are wont to believe.
" The sound made by pebbles rattling inside an opaque
glass tube does not attract or alarm pollack ; neither are
they affected by the sharp sound made by letting a hanging

* Journal of Marine Biological Association, New Series, vol. i. No. 3, p. 251.
t Of course, anglers will say that what may be true for pollack and other
coarse and vulgar sea-fish does not apply to King Salmon or Prince Trout.

The Senses of Animals. 265

stone tap against an opaque glass plate standing vertically
in the water." Carp at Potsdam are, indeed, said to come
to be fed at the sound of a bell. But Mr. Bateson well
remarks that this " can scarcely be taken to prove that the
sound of the bell was heard by them, unless it be clearly
proven that the person about to feed them was hidden from
their sight." There is clearly room for further observation
and experiment in this matter.

Turning to the invertebrata, we find, even in creatures
as low down in the scale of life as jelly-fish, around the
margin of the umbrella in certain medusae, simple auditory
organs. In some cases they are pits containing otoliths
(minute calcareous or other bodies, which are supposed to
be set a-dance by the sound-vibrations) ; in others there is
a closed sac with one or more otoliths ; in others, again,
they are modified tentacles, partially or completely enclosed
in a hood. All these are generally regarded as auditory,
there being specially modified cells of the nature of hair-
cells. We shall see, however, that another interpretation
of organs containing otoliths is at any rate possible. For
the present, we will follow the usual interpretation, and
regard them as auditory.

Vesicular organs containing otoliths are found near the
cerebral ganglia in some of the worms and their relations.
But the common earthworm, though it appears to be sensi-
tive to sound, does not appear to have any such organs.

Molluscan shell-fish are generally provided with auditory
organs. In the fresh-water mussel it is found in the
muscular foot. It can be more readily seen in the Cyclas,
if the transparent foot of this small mollusc be examined
under the microscope. It is a small sac containing an
otolith. Mr. Bateson found that the mollusc Anomia "can
be made to shut its shell by smearing the finger on the
glass of the tank so as to make a creaking sound. The
animals shut themelves thus when the object on which they
were fixed was hung in the water by a thread." In the
snail and its allies the auditory sac is found in close
connection with the nerve-collar that surrounds the gullet.

266 Animal Life and Intelligence.

In the cuttle-fishes it is found embedded in the cartilage of
the head.

In the lobster or crayfish the auditory organs are found
at the base of the smaller feelers or antennules. They are
little sacs formed by an infolding of the external integument
(see Fig. 26, p. 259). Beautifully feathered auditory hairs
project into the sac along specialized ridges, and the sac
in many cases contains grains of sand which play the part
of otoliths. Hensen seems to have proved that shrimps
collect the grains of sand and place them in the auditory
sac for this purpose. The
curious shrimp-like Mysis has
two beautiful auditory sacs in
its tail. These are provided
with auditory hairs. Hensen

scope while a musical scale was
sounded, and found that the special hairs responded each
to a certain note. When this particular note was sounded
the hair was thrown into such violent vibration as to become
invisible, but by other notes it was unaffected.

Passing now to insects, we may first note that grass-
hoppers and crickets have an auditory organ on the front
leg. These are provided with tympanic mem-
branes, and the breathing-tubes, or tracheae,
are so arranged that the pressure of the air
is equalized on the two sides of the mem-
brane—just as in us and other vertebrates the
same end is effected by a tube which runs
from the interior of the drum of the ear to the
Fig. 29.— Leg mouth-cavity (see Fig. 27). In the organ within

of grasshopper. ..,.,. , ,, , ,, , j ,

ty., tympanic mem- ™e ^6§ there ls a g*OUp of Cells, followed by a

brane. row Of simiiar Ceu8 which diminish regularly in
size from above downwards. Each is in connection with a
nerve-fibril, and contains a delicate auditory rod. It has
been suggested that the diminution in size of the cells may
have reference to the appreciation of different notes, but
nothing definite is known on the matter. Ants, too, have

The Senses of Animals. 267

an auditory organ, as shown by Sir John Lubbock, in the
tibia of the front leg. But in locusts it is situated on the
first segment of the abdomen. In flies there are a number
of vesicles, generally regarded as auditory (but by some as
olfactory), at the base of the rudimentary hind wings — the
so-called halteres, or balancers.

Observation seems to point to the fact that in most
insects the sense of hearing is lodged in the feelers, or
antennae. Kirby made the following observation on a little
moth : " I made," he says, " a quiet, not loud, but distinct
noise ; the antenna nearest to me immediately moved
towards me. I repeated the noise at least a dozen times,
and it was followed every time by the same motion of that
organ, till at length the insect, being alarmed, became
more agitated and violent in its motions." Hicks wrote,
in 1859, " Whoever has observed a tranquilly proceeding
Capricorn beetle which is suddenly surprised by a loud
sound, will have seen how immovably outward it spreads
its antennae, and holds them porrect, as it were, with great
attention, as long as it listens." The same observer
described certain highly specialized organs in the antennae
of the hymenoptera (ants, bees, and wasps), which he thus
describes : " They consist," he says, " of a small pit lead-
ing into a delicate tube, which, bending towards the base,
dilates into an elongated sac having its end inverted." Of
these remarkable organs, Sir John Lubbock says there are
about twelve in the terminal segment, and he has suggested
that they may serve as microscopic stethoscopes.

Mayer, experimenting with the feathered antenna of
the male mosquito, found that some of the hairs were
thrown into vigorous vibration when a note with 512
vibrations per second was sounded. And Sir John Lubbock,
who quotes this observation, adds,* "It is interesting
that the hum of the female gnat corresponds nearly to this
note, and would consequently set the hairs in vibration."
The same writer continues, " Moreover, those auditory
hairs are most affected which are at right angles to the
* " Senses of Animals," p. 117,

268 Animal Life and Intelligence.

direction from which the sound comes. Hence, from the
position of the] antennae and the hairs, a sound would act
most intensely if it is directly in front of the head.
Suppose, then, a male gnat hears the hum of a female at
some distance. Perhaps the sound affects one antenna
more than the other. He turns his head until the two
antennae are equally affected, and is thus able to direct his
flight straight towards the female."

It is difficult to determine the range of hearing in the
lower organisms. But it is quite possible, nay, very
probable, that the superior limit of auditory sensation is
much more extended in insects than it is in man. We know
that many insects, such as the cicadas, the crickets and
grasshoppers, many beetles, the death's-head moth, the
death-watch, and others, make, in one way or another,
sounds audible to us. But there may be many insect-
sounds — we may not call them voices — which, though
beyond our limits of hearing, are nevertheless audible to
insects. At the other end of the scale, on the other hand,
slow pulsations may be appreciated — for example, by
aquatic creatures — by means of what we term the auditory
organs, in a way that is not analogous to the sensation of
sound in us. It may be noted that auditory organs are
dotted about the body somewhat promiscuously in the
various invertebrates. We have seen that auditory organs,
or what are generally believed to be such, are found in the
foot of bivalves, in the antennules of lobsters, in the fore
legs of crickets and ants, in the abdomen of locusts, in the
balancers of flies, and in the tail of Mysis. But when we
come to consider the matter, there is no reason why the
organ of hearing should be in any special part of the body.
The waves of sound rain in upon the organism from all sides.
There is no great advantage in having the organs of hearing
in the line of progression, as with sight, where the rays
come in right lines ; nor in having them in close association
with the mouth, as in the case of the organ of smrfll.

Closely connected with the organ of hearing in vertebrates
is the organ of another and but recently recognized sense.

The Senses of Animals. 269

In briefly describing the auditory apparatus in man, mention
was made of three curved membranous loops, the so-called
semicircular canals. A few more words must now be said
about them and the membranous sac with which they are
connected.

The sac lies in a somewhat irregular cavity in a bone
at the side of the head, in the walls of which are five
openings leading into curved tunnels in the bone in which
lie the membranous loops. The planes in which the three
semicircular canals lie are nearly at right angles to each
other, and they are called respectively the horizontal,
the superior, and the posterior. The two latter unite at
one end before they reach the sac ; hence there are five, and
not six, openings into the cavity. At one end of each semi-
circular canal is a swelling, or ampulla, in each of which is
a ridge, or crest, abundantly supplied with hair-cells. And
in a little recess in the sac there is, occupying its floor, its
front wall, and part of its outer wall, a patch of hair-cells
covered by a gelatinous material with numerous small
crystalline otoliths. The only other point that calls for
notice is that the membranous sac does not fit closely in
the bony cavity in which it lies, while the diameter of the
membranous semicircular canals is considerably less than
that of their bony tunnels, except at the ampullae, or swellings,
where they fit pretty closely. Both the bony cavity and the
membranous labyrinth (as it is called) are filled with fluid.

From its close connection with the organ of hearing,
this apparatus was for long regarded as in some way
auditory in its function, and it was surmised that it enabled
us to perceive the direction from which the sound came.
But how it could do so was not clear. In 1820 M.
Flourens made the observation that the injury or division
of a membranous canal gave rise in the patient to rotatory
movements of the animal round an axis at right angles to
the plane of the divided canal ; and he, therefore, suggested
that the canals might be concerned in the co-ordination of
movement. They are now regarded as the organs of a
sense of rotation or acceleration,

270

Animal Life and Intelligence.

That we have such a sense of rotation has been proved
experimentally.* Let a man, blindfolded, sit on a smooth-
running turn-table. When it begins to rotate he feels that
he is being moved round, but if the rotation be continued
at the same rate, this feeling quickly dies away. If the
rotation be increased, he again feels as if he were being
moved round, but this again soon dies away. Further in-
crease gives a fresh sensation, which in turn subsides, and
the man may then be spinning round rapidly, and be per-
fectly unconscious of the fact. He is only aware that he has
been gently turned round a little two or three times. Now
let the speed of rotation be slackened. He has a sensation
of being gently turned round a little in the opposite direction.
Each time the speed is lessened he has this sense of being
turned the reverse way. From these experiments we see
that what we are conscious of is change of rate of rotation,
or, in technical language, acceleration, positive or negative.

From Professor Crum Brown's paper in Nature I tran-
scribe, with some verbal modifications, his account of how
the semicircular canals enable us to feel these changes of
SC.

A /'•

Fig. 30. — Diagram of semicircular canals.

A. bony labyrinth of human ear (after Sommering). c, c., the cochlea; *.c., superior
semicircular canal ; p.c., posterior semicircular canal ; h.c., horizontal semicircular canal ;
a, a, a, their swellings, or ampullae; f.o., f.r., fenestra ovalis and rotunda (oval and round
windows) in the vestibule.

B. Diagram of semicircular canal to illustrate effect of rotation. The large arrows indicate
the direction of the rotation. The small arrow to the left indicates the resulting flow of the
inner fluid into the ampulla ; that to the right, the flow of the outer fluid into the vestibule.

motion. Let us consider the action of one canal. If the
head be rotated about a line at right angles to the plane of
the canal, with the ampulla leading, there will be a tendency

* See a very interesting and lucid paper by Professor Crum Brown, whose
name is intimately connected with this subject, in Nature, vol. il. p. 449.

The Senses of Animals. 271

for the fluid within the sac to flow into the ampulla, and
for the fluid around the semicircular canal to flow into the
cavity in which the sac lies. These movements will con-
spire to stretch the membranous ampulla, and thus to
stimulate the hair-cells. This stretching will not take
place in that canal if the rotation be in the reverse direction.
But on the opposite side of the head is another canal in
the same plane, but turned the other way. In the reversed
rotation the ampulla in this canal will lead, and its hair-
cells will be stimulated. Thus by means of the two canals
on either side of the head in the same plane, rotation in
either direction can be appreciated. And since there are
two other pairs of semicircular canals in two other planes,
rotation in any direction will be recognized by means of
one or more of the six canals.

It is thus by means of the semicircular canals that we
can appreciate acceleration of rotatory motion.* But we
can also appreciate acceleration of movements of translation
— forwards or backwards, up or down. And Professor
Mach has suggested that it is through the stimulation of
the hair-cells in the patch in the sac itself (the so-called
macula acustica) that we are able to appreciate these changes.
The otoliths, held loosely and lightly in position by the
gelatinous substance in which they are embedded, may,
through their inertia, aid in the stimulation of the sense-
hairs.

And this naturally suggests the question whether those
sense-organs in the invertebrates which contain otoliths
may not be regarded with more probability as organs for
the appreciation of changes of motion than as auditory
organs. This for some years has been my own belief. I
have always felt a difficulty in understanding how the
otoliths are set a-dance by auditory vibrations. But their
inertia would materially aid in the appreciation of changes
of motion. In some forms the otoliths are held in suspen-
sion in a gelatinous material. In others — the molluscs,

* It is interesting to note that in the blind-fish (Amblyopsis spelxus) the
semicircular canals are, according to Wyman, unusually large.

2 72 Animal Life and Intelligence.

for example — the otolith (which is generally single) is
retained in a free position by ciliary action. In aquatic
creatures an organ for the appreciation of changes of
motion might be of more service than an auditory organ.
And if one be permitted to speculate, one may surmise that
the sense of hearing may be a refinement of the sense
through which changes of motion are appreciated. First
would come a sense of movements of the organism in the
medium through the stimulation of the sense-hairs by
the relative motion of the otolith ; then these sense-hairs,
with increased delicacy, might appreciate shocks in the
medium; and, eventually, those more delicate shocks
which we know as auditory waves. In this way we might
account for the fact that in the vertebrates the same
organ, through different parts of its structure, appreciates
both change of motion and auditory vibrations. And thus
the organs in the invertebrata which are generally regarded
as auditory, and for which has been suggested the function
of reacting to changes of motion, may, in truth, subserve
both purposes — may be organs in which the differentiation
I have hinted at is taking place.

Sight, like hearing, is a telsesthetic sense. Through it
we become aware of certain vibratory states of more or less
distant objects. The medium by means of which these
vibrations are transmitted is not, as in the case of hearing,
the air, but the aether which pervades all space. The rate
of transmission is about 186,000 miles in a second. That
which answers in vision to pitch in hearing is colour. The
lowest, or gravest, light-tone to which we are sensitive is
deep red, where the number of vibrations per second is
about 370 billions (370,000,000,000,000). The highest, or
most acute, light-tone is violet, with about 833 billion
vibrations in a second. If white light be passed through
a prism, the rays are classified according to their vibration-
periods, and are spread out in a spectrum, or band of
rainbow colours. But different individuals vary, as we
shall presently see, in their sensibility to the lowest and

The Senses of Animals. 273

the highest vibrations. Some people are, moreover,
relatively or absolutely insensible to certain colours,
generally either red or green. Such persons are said to
be colour-blind. When the rainbow colours are combined
in due proportion, or when pairs or sets of them are com-
bined in certain ways, white light is produced.

We saw that in the case of sound-waves, when the
number of vibrations in a second is doubled, the sound is
raised in pitch by an octave. Using this term in an
analogous way for colour-tones, we may say the range in
average vision is about one octave — that is, from about
400 billion to about 800 billion vibrations in a second.
But, though these are the limits in human vision, we know
of the existence of many octaves of radiant energy
physically in continuity with the light-vibrations. Photo-
graphy has made us acquainted with ultra-violet vibrations
up to about 1600 billions per second — an octave above the
violet. And Professor Langley's observations with the
bolometer indicate the existence of waves with as low a
vibration-period as one billion per second, and even here,
in all probability, the limit has not been reached. To the
vibrations more rapid than those that are concerned in
the sensation of violet, the human organism is apparently
in no manner sensitive. But to infra-red vibrations down
to about thirty billions per second the nerves of the skin
respond through the temperature- sense. We shall have to
return to these limits of sensation at the close of this
chapter.

The human eye is a nearly spherical organ, capable of
tolerably free movements of rotation in its socket. What
we may call the outer case, which is white and opaque
elsewhere, is quite transparent in front. Through this
transparent window may be seen the coloured iris, in the
centre of which is a circular aperture, the pupil. The size
of the pupil changes with the amount of light — it dilates
or contracts, according as the light is less or more intense.
Just behind it, and still in the front part of the eye, is the
transparent lens, the convexity of the anterior surface of

274

Animal Life and Intelligence.

which can be altered in the accommodation of the organ
for near or far vision. The space between the lens and

Fig. 31. — The human eye.
Horizontal section, to show general structure.

iris and the corneal window of the eye is filled with a
watery fluid. Behind the lens there is a transparent, semi-
fluid, jelly-like material, filling the rest of
,£ the chamber of the eye. At the back of the
eye is spread out the sensitive membrane
— the retina. The structure of this mem-
brane is very complicated, and cannot be
described here. It is, however, indicated
in Fig. 32. For our present purpose it is
sufficient to note that here are the end-
organs of the optic nerve ; that these con-
. sist of a number of delicate rods and cones ;

Fig. 32.— Retina of >.,...

the eye. Enlarged and that these rods and cones do not face

in the direction from wbicn the Kght comes,
., back of retina next but face towards the back of the eyeball,

the outer coat; Z.r.c., . . i i i i • a i i

layer of rods and cones; where a pigmented substance is developed.

i.l., intermediate layers ; „, , -. . . , , , ,

z.p.c., layer of ganglion- The rays of light are thus focussed through

cells; Z.n./., layer of . *.*_•'• L a i L

. *.*_•• L a i L

., front of the retina on to this pigmented substance ;

retina, the surface turned ,

towards the pupii. the ends of the rods and cones are stimu-
lated ; and the stimulation is handed on, augmented in

The Senses of Animals. 275

certain intermediate ganglia, to the delicate transparent
nerve-fibres in the front of the retina. These collect to a
certain spot, where they pass through the retina to form the
optic nerve. Where they pass through the retina there can,
of course, be no rods and cones. And in this spot there is
no power of vision. It is the blind spot. The reality of its
existence can easily be proved. Make a dot on a piece of
writing-paper, and about three inches to the left of it place
a threepenny or sixpenny bit. Close the right eye, and look
with the left eye at the dot. The sixpenny bit will also be
seen, but not distinctly. Keep the eye fixed on the dot,
and move the head slowly away from the paper. At a
distance of about ten inches the coin will completely dis-
appear from view. Its image then falls on the blind spot.

The organ of vision, then, in us consists of an essential
sensory membrane, the retina, with its delicate rods and
cones ; and an accessory apparatus for focussing an inverted
image on to the sensitive surface of the retina. The
surface is not, however, equally sensitive, or, in any case,
does not give an equal power of discrimination, throughout
its whole extent. This is seen in the experiment above
described. When we look at the dot we see the coin, but
not distinctly. The area of clear and distinct vision is, in
fact, very small, constituting the yellow spot about ^ of
an inch (2 millimetres) long, and 3^ of an inch ('8 milli-
metre) broad. And even within this small area there is a
still more restricted area of most acute sensibility only T^Q
of an inch (-2 millimetre) in diameter. Nevertheless,
within this minute area there are some two thousand
cones, the rods being here absent. In carefully examining
an object we allow this area of acute vision to range over
it. Hence the extreme value of that delicate mobility
which the eye possesses— a mobility that is accompanied
by muscular sensations of great nicety.

We saw that the sense of touch in the tongue is
sufficiently delicate to enable us to recognize, as two,
points of contact separated by ^5 of an inch (I'l milli-
metre). What, in similar terms, is the delicacy of sight ?

276 Animal Life and Intelligence.

At what distance apart, on the most delicate part of the
retina, can two points of stimulation be recognized as dis-
tinct from each other ? If the points of stimulation be not
less than #oW of an inch ('004 millimetre) apart, they
can be distinguished as two. Below this they fuse into
one. The diameter of the end of a single cone in the
yellow spot is also about ^Vo of an inch (-0045 millimetre).

With regard to the mode in which the stimulation of
the retinal elements is effected, we have no complete know-
ledge. Certain observations of Boll and Kiihne, however,
show that when an animal is killed in the dark the retina
has a peculiar purple colour which is at once destroyed if
the retina be exposed to light. If a rabbit be killed at the
moment when the image, say, of a window, is formed on
the retina, and the membrane at once plunged in a solution
of alum, the image may be fixed, and an " optogram " of
the window may be seen on the retina. The discharge of
the colour of the retinal purple may be regarded as the
sign of a chemical change effected by the impact of the
light-vibrations. But in the yellow spot there seems to be
no visual purple. It is, indeed, developed only in the rods,
not in the cones. Here, probably, chemical or metabolic
changes occur without the obvious sign of the bleaching of
retinal purple. In the dusk-loving owl the retinal purple
is well developed, but in the bat it is said to be absent.

We saw that in the case of hearing the auditory organ
is fitted to respond to air-borne vibrations varying from
about thirty to thirty thousand per second. And though
the details of the process are at present not well under-
stood, it is believed that certain parts of the recipient
surface are fitted to respond to low tones, other parts to
intermediate tones, and yet others to high tones. Thus
the reception is serial. If there be two pianos near each
other, accurately in tune, any note struck on one will set
the corresponding note vibrating in the other.* The
auditory organ may be likened to this second piano.
Special parts respond to special tones.

* The dampers must, of course, be lifted by depressing the loud pedal.

The Senses of Animals. 277

Now, in the case of vision, the conditions are different.
The reception cannot be serial. As I range my eye over
a flower-bed, I bring the area of distinct vision on to a
number of different colours, and these are seen to be dis-
tinct, though they are received on the same part of the
retinal surface. It might, perhaps, be suggested that
special cones were set apart for each shade of colour. But
there are only some two thousand cones in the central area
of most acute vision, and Lyons silk-manufacturers prepare
pattern cards containing as many shades of coloured silks.
So that there would be only one cone to each colour. And
Herschel thought that the workers on the mosaics of the
Vatican could distinguish at least thirty thousand different
shades of colour! There are also many phenomena of
colour-blending which show that colour-reception cannot
in any sense be serial.

How, then, are we to account for our wide range of
colour-sensation? Just as the blending by the artist on
his palette of a limited number of pigments gives him the
wide range of colour seen on his canvas, so the blending of
a few colour-tones may give us the many shades we are
able to distinguish. The smallest number of fundamental
colour-tones which will fairly well account for the pheno-
mena of colour-vision, is three. And these three are red,
green, and blue or violet. These are the three so-called
primary colours. All others are produced from these
elements by blending.

To explain our ability to appreciate differences of colour,
then, it ..is supposed, on the hypothesis of Young and Von
Helmholtz, that three kinds of nerve-fibres exist in the
retina, the stimulation of which gives respectively, red,
green, and violet in consciousness. Professor McKendrick,
interpreting Von Helmholtz, gives * the following scheme : —

" 1. Bed excites strongly the fibres sensitive to red, and
feebly the other two.

"2. Yellow excites moderately the fibres sensitive to
red and green, feebly the violet.

* " Special Physiology," p. 636.

278 Animal Life and Intelligence.

" 3. Green excites strongly the fibres sensitive to green,
feebly the other two.

"4. Blue excites moderately the fibres sensitive to
green and violet, feebly the red.

" 5. Violet excites strongly the fibres sensitive to violet,
feebly the other two.

" 6. When the excitation is nearly equal for the three
kinds of fibres, the sensation is white/'

This theory cannot be regarded as more than a pro-
visional hypothesis. Still, by its means we can explain
many colour-phenomena. It is well known, for example,
that if we gaze steadily at a red object, and then look aside
at a grey surface, an after-image of the object will be seen
of a blue colour. According to the theory, the red fibres
have been tired and cannot so readily answer to stimulation.
Over this part of the retina, therefore, the effect of grey
light is to stimulate normally the fibres sensitive to green
and violet, but only slightly those sensitive to red, owing
to their tired condition. The result will be, as we see from
the above scheme (4), the sensation of blue. Colour-blind
people, on this view, are those in whom one set of the fibres,
generally the red or the green, are lacking or ill developed.

We may, perhaps, with advantage restate this theory in
terms of chemical change, or metabolism. On this view
three kinds of "explosives" are developed in the retinal
cones ; for it is seemingly the cones, rather than the rods,
which are concerned in colour-vision. All three explosive
substances are unstable ; but one, which we may call E.,
is especially unstable for the longer waves of the spectrum ;
another, G., for the waves of mid-period ; a third, V., for
those of smallest wave-length.

Suppose that E. only were developed. If, then, we were
to look at a band of light spread out in spectrum wave-
lengths, we should see a band'* of monochromatic r. light.
Its centre would be bright, and here would be the maximum
instability of E. On either side it would fade away. The

* A band and not a line, because K. is unstable to the impact of a con-
iderable range of light-vibratious.

The Senses of Animals. 279

lateral edges of the spectrum would be the limits of the
instability of E. If G. only were developed, we should see
only a band of monochromatic g. light. Its centre would
not coincide with that for E., but would lie in a region of
smaller wave-length. Here would be the maximum in-
stability for G. On either side the green would fade away.
Its lateral edges would mark the limits of the instability
of G. But though their centres would not coincide, the
E. band and the G. band would to a large extent overlap.
Similarly with the band for V. It, too, would have its
centre of maximum instability and its lateral edges of
lessening instability. Its centre would lie in a region of
yet smaller wave-length than that for G. And the v. band
would overlap the green and the red.

Normally, all three bands are developed, and their
blended overlapping gives the colours of the rainbow. For
this reason the monochromatic bands r., g., and v. are un-
known to us in experience. All the colour-tints we know
are blended tints. What we call full-red light causes
strong disruptive change in E., but decomposes slightly
G., and probably also, but in much less degree, V.

Whether E., G., and V. are all three present in each
cone, or whether they are each developed in separate
cones, we do not know for certain. Nor are we certain
that there are separate nerve-fibres for the transmission of
stimuli due to E., G., and V.

When we look steadily at a red object we cause the
disruption of E. ; and since it takes some time for the
reformation and reconstitution of this explosive substance,
on turning the eye to a grey surface, G. and V. are alone,
or in preponderating proportions, caused to undergo dis-
ruption. Hence the phenomena of complementary after-
images. It is not merely a matter of the tiring of certain
nerve-fibres, but a using-up of the explosive material in
certain of the cones.

What is called colour-blindness is probably due to one
of several abnormal conditions. It is possible that in some
cases E., G., or V. may be entirely absent. More fre-

280 Animal Life and Intelligence.

quently they are in abnormal proportions. They probably
vary in their sensitiveness, and not improbably in the
wave-period to which they show the maximum response.

To test the variation, if any, in the limits of instability
for K. and V., or in any case in the limits of colour-vision
at the red end and at the violet end of the spectrum, in
apparently normal individuals, my friend and colleague,
Mr. A. P. Chattock, made, at my suggestion, a number of
observations on some of the students of the University
College, Bristol, to whom my best thanks are due for their
kind willingness to be submitted to experiment. The instru-
ment used * was a single-prism spectro-goniometer.

In the accompanying diagram (Fig. 33) the results of
some of these observations are graphically shown. The
middle part of the spectrum, between the wave-lengths
420 and 740 millionths of a millimetre, is omitted, only the
red end and the violet end being shown. The observations
on thirty-four individuals, seventeen men and seventeen
women, all under thirty years of age, are given for both
eyes. The left-hand vertical line of each pair stands for
the right eye in each case. To the left of the table are
placed the wave-lengths in millionths of a millimetre.

Take, for example, the first pair of vertical lines. The

* Mr. Chattock has kindly supplied me with the following note:—

" Headings at the violet end were taken at the extremity of the lavender
rays, at the point where the faint band of lavender light seemed to end off
about half-way across the field of view (the cross-wires being invisible).

" At the red end the cross-wires were always visible, and were in each
case set to the point where the top horizontal edge of the spectrum lost its
definition.

" Other things equal, the ' red ' readings should be more reliable than the
violet, therefore, from the greater definiteness of the point observed, and the
means of observing it. But against this has to be set off the fact that the
extreme violet rays were spread out by the prism used more than eight times
as much as the red rays.

" In any case, the wide differences observed in the ' red ' readings are much
greater than could have been due to misunderstanding or careless observation
— as shown by setting the instrument to maximum and minimum reading*,
and noting the very obvious difference between them apparent to a normal
eye. The same conclusion is rather borne out by the closer (average) agree-
ment between the two eyes of the same individual than between those of
different persons.

" The source of light was the central portion of an ordinary Argand burner."

The Senses of Animals.

281

VIOLET

282

Animal Life and Intelligence.

individual whose colour-range they represent could detect
red light in the spectrum up to 800 millionths of a milli-
metre wave-length for the right eye, and up to 811 for the
left ; and could detect violet light down to 403 and 404.
Beyond these limits all was dark. But the last individual
in the series, while his range in the violet was about the same,
could only detect red light up to 743 and 750 millionths of
a millimetre. His spectrum was so much shorter.

It is seen that there is more variation at the red end
than at the violet end of the spectrum, and this notwith-
standing that the violet rays are more spread out by the
prism than the red rays. It is seen that the two eyes are
often markedly different. This is not due to inaccuracy of
observation, for certain individuals in which this occurred
were tested several times with similar results. It is seen
that the variations at the red end and the violet end are
often independent, and that the absolute length of the
visible spectrum differs in different individuals.

The following table presents these observations and a
few others in another light : —

TABLE OP MAXIMA AND MINIMA IN WAVE-LENGTHS, EXPRESSED IN
MILLIONTHS OF A MILLIMETRE.

VIOLET.

RED.

No. of

Highest.

Mean.

Lowest.

Highest.

Mean.

Lowest.

viduals.

Women under 30..

410-0

402-75

394-0

811

772-85

743

17

Men „

413-0

405-0

399-0

811

772-8

743

17

Women over 30 . .

4105

406-65

401-5

792

767-8

743

7

Men „ „ ..

407-0

404-5

402-5

787

773-7

758

3

J right eye

406

687

N{ left eye

407

717

The individual N showed signs of colour-blindness,
and is therefore not included in the table, but entered
separately. He was unable to recognize the C line of the
hydrogen spectrum (wave-length 656), which was brilliantly
obvious to the normal eye.

The Senses of Animals. 283

These observations* need further confirmation and
extension. We intend to continue the investigation each
session. They are, however, sufficient to show that in
some individuals E. undergoes disruptive change on the
impact of light- waves which have no noticeable effect on
the retina of other individuals.

It is impossible here to do more than just touch the
fringe of the difficult subject of colour-vision. And the
only further fact that can here be noticed is that trichro-
matic colour-vision is apparently in us limited to the
yellow-spot and its immediate neighbourhood. Around
this is an area which is said to be bichromatic — all of us
being, for this area, more or less green-blind. In the
peripheral area around this, colour is indistinguishable,
and we are only sensitive to light and shade. So far as
the structure of the retina is concerned, we may notice in
this connection that in the central region of most complete
trichromatic vision there are cones only ; around the
yellow spot each cone is surrounded by a circle of rods ;
and further out into the peripheral region by two, three, or
more circles of rods.

Concerning the sense of sight in the lower mammals
little need be said. In many cases the acuteness of vision
is remarkable. Mr. Eomanes's experiments on Sally, the
bald-headed chimpanzee at Eegent's Park, led him to
conclude that she was colour-blind, but I question whether
the experiments described quite justify this conclusion.
Sir John Lubbock was unable to teach his intelligent dog
Van to distinguish between coloured cards ; but the failure
was as complete when the cards were marked respectively
with one, two, or three dark bands. We are not justified,
therefore, in ascribing the failure to colour-blindness. The
real failure, probably, was in each case to make the animal
understand what was wanted. Bulls are, at any rate,

* The variations above indicated throw light on a fact to which Lord Ray-
leigh has directed attention. The yellow of the spectrum may be matched by a
blending of spectral red and spectral green ; but the proportions in which these
spectral colours must be mixed differ for different individuals. The comple-
mentary colours for different individuals are also not precisely the same.

284 Animal Life and Intelligence.

credited with strong colour-antipathies, and insect-eating
mammals are probably not defective in the colour-sense.

It is said that nocturnal animals, such as mice, bats,
and hedgehogs, have no retinal cones ; and if the cones
are associated with colour-vision, they may not improbably
be unable to distinguish colours. Some moles are blind
(e.g. the Cape golden mole). But the common European
mole, though the eyes are exceedingly minute (^ of an
inch in diameter), has the organ fairly developed, and is
even said not to be very short-sighted. It is protected by
long hairs when the animal is burrowing, and is only used
when it comes to the surface of the ground.

It is probably in birds that vision reaches its maximum
of acuteness. A tame jackdaw will show signs of uneasi-
ness when seemingly nothing is visible in the sky. Pre-
sently, far up, a mere speck in the blue, a hawk will come
within the range of far-sighted human vision. Steadily
watch the speck as the hawk soars past, until it ceases to be
visible ; the jackdaw will still keep casting his eye anxiously
upward for some little time. He may be only watching
for the possible reappearance of the hawk. But just as
he saw it before man could see it, so. probably he still
watches it after, to man's sight, it has become invisible.
So, too, for nearer minute objects, the swift, as it wheels
through the summer air, presumably sees the minute
insects which constitute its food. And every one must
have noticed how domestic fowls will pick out from among
the sand-grains almost infinitesimal crumbs.

It is probable that the area of acute vision is much
more widely diffused over the retina of birds than it is with
us. In any case, the cones. are more uniformly and more
abundantly distributed over the general retinal surface.

An exceedingly interesting and important peculiarity
in the retina of birds," which they share with some reptiles
and fishes, is the development, in the cones, of coloured
globules. " The retinae of many birds, especially of the
finch, the pigeon, and the domestic fowl, have been care-
fully examined by Dr. Waelchli, who finds that near the

The Senses of Animals. 285

centre green is the predominant colour of the cones, while
among the green cones red and orange ones are somewhat
sparingly interspersed, and are nearly always arranged
alternately — a red cone between two orange ones, and vice
versa. In a surrounding portion, called by Dr. Waelchli
the red zone, the red and orange cones are arranged in
chains, and are larger and more numerous than near the
yellow spot ; the green ones are of smaller size, and fill up
the interspaces. Near the periphery the cones are scattered,
the three colours about equally numerous and of equal
size, while a few colourless cones are also seen. Dr.
Waelchli examined the optical properties of the coloured
cones by means of the micro-spectroscope, and found, as
the colours would lead us to suppose, that they transmitted
only the corresponding portions of the spectrum ; and it
would almost seem, excepting for the few colourless cones
at the peripheral part of the retina, that the birds examined
must have been unable to see blue, the whole of which
would be absorbed by their colour-globules." *

These facts are of exceeding interest. They seem to
show that for these birds the retinal explosives are not the
same as for us. They are E., 0., and G. Moreover, the
colour-globules will have the effect of excluding the pheno-
mena of overlapping. For each kind of cone the spectrum
must be limited to the narrow spectral band transmissible
through the associated colour-globule. If these facts be
so, it is not too much to say that the colour- vision of birds
must be so utterly different from that of human beings,
that, being human beings, we are and must remain
unable to conceive its nature. The factors being different,
and the blending of the factors by overlap being, by
specially developed structures, lessened or excluded, the
whole set of resulting phenomena must be different from
ours. And this is a fact of the utmost importance when
we consider the phenomena of sexual selection among
birds, and those theories of coloration in insects which
involve a colour-sense in birds.

* " Col our- Vision and Colour-Blindness," E. Brudenell Carter (Nature,
vol. xlii. p. 56).

286 Animal Life and Intelligence.

Concerning the sense of sight in reptiles and in
amphibians, little need here be said. At near distances
some of them undoubtedly have great accuracy of vision.
This is, perhaps, best seen in the chamseleon. In this
curious animal the eyes are conical, and each moves freely,
independently of the other. The eyelids encase the organ,
except for a minute opening, looking like a small ink-spot
at the blunted apex of the cone. The animal catches the
insects on which it feeds by darting on to them its long
elastic tongue and slinging them back into the mouth,
glued to its sticky tip. Its aim is unerring, but it never
strikes until both eyes come to rest on the prey, and great
accuracy of vision must accompany the great accuracy of
aim. Frogs and toads capture their prey in a somewhat
similar way ; and a great number of reptiles and amphibians
are absolutely dependent for their subsistence on the acute-
ness and accuracy of their vision, which is, however, on
the whole, markedly inferior to that of birds.

In fishes, from their aquatic habit, the lens and dioptric
apparatus are specially modified, in accordance with the
denser medium in which they live ; and one curious fish,
the Surinam sprat, is stated to have the upper part of
the lens suited for aerial, and the lower part for aquatic
vision.

Mr. Bateson * has made some interesting observations
on the sense of sight in fishes. He finds that in the great
majority of fishes the shape and size of the pupil do not
alter materially in accordance with the intensity of the
light. The chief exceptions are among the Elasmobranchs
(dog-fishes and skates). In the torpedo the lower limb of
the iris rises so as almost to close the pupil, leaving a
horizontal slit at the upper part of the eye. In the rough
dog-fish, the angel-fish, and the nurse-hound, the pupil
closes by day, forming merely an oblique slit. In the
skate a fern-like process descends from the upper limb of

* Journal of Marine Biological Association, New Series, vol. i. Xos. 2 and
3. His experiments with regard to the colour-sense in fishes gave, for the
most part, negative results.

The Senses of Animals. 287

the iris. The contraction in these cases does not seem to
take place rapidly as in land vertebrates, but slowly and
gradually.

Among diurnal fishes belonging to the group of the
bony fishes (Teleosteans), the turbot, the brill, and the
weever have a semicircular flap from the upper edge of
the iris, which partially covers the pupil by day, but is
almost wholly retracted at night.

None of the fishes observed by Mr. Bateson appears to
distinguish food (worms) at a greater horizontal distance
than about four feet, and for most of them the vertical
limit seemed to be about three feet ; but the plaice at the
bottom of the tank perceived worms when at the surface of
the water, being about five feet above them. Most of them
exhibited little power of seeing an object below them. But
though the distance of clear vision seems to be so short for
small objects in the water, many of these fish (plaice,
mullet, bream) notice a man on the other side of the room,
distant about fifteen feet from the window of the tank.
The sight of some fishes, such as the wrasses (Labridee), is
admirably adapted for vision at very close quarters. "I
have often seen," says Mr. Bateson, "a large wrasse search
the sand for shrimps, turning sideways, and looking with
either eye independently, like a chamaeleon. Its vision is
so good that it can see a shrimp with certainty when the
whole body is buried in grey sand excepting the antennae
and antenna-plates. It should be borne in mind that, if
the sand be fine, a shrimp will bury itself absolutely,
digging with its swimmerets, kicking the sand forwards
with its chelae, finally raking the sand over its back, and
gently levelling it with its antennae ; but if the least bit
be exposed, the wrasses will find it in spite of its protective
coloration."

Although it is probably not functional in any existing
form, mention must here be made of the median or pineal
eye. On the head of the common slow-worm, or blind-
worm, there is a dark patch surrounding a brighter spot.

288

Animal Life and Intelligence.

Fig. 34.— Pineal eye.

Varanus
Spencer.)

This is the remnant of a median eye. It has been found in
varying states of degeneration in many reptiles (Fig. 34), and
in a yet more vestigial form in some fishes and amphibia. It
is connected with a curious struc-
ture, associated with the brain of
all vertebrates, and called the
pineal gland. Descartes thought
that this was the seat of the soul ;
but modern investigation shows
it to be a structure which has
resulted from the degeneration of
that part of the brain which was
connected with the median eye.
There is some reason to suppose

that> in ancient life-forms> like

the Ichthyosaurus, and Plesio-
saurus, and the Labyrinthodont amphibians, it was large
and functional. In any case, there is a large hole in the
skull (Fig. 35) through which the nervous connection with the
brain may have been established . The structure of the eye

is not similar to that of the
lateral eye, but more like that
of some of the invertebrates.
To these invertebrates we
must now turn.

Insects have eyes of two
kinds. If we examine with a
lens the head of a bee, we
shall see, on either side, the
large compound or facetted
eye ; but in addition to these
there is on the forehead or
vertex a triangle of three
small, bright, simple eyes, or

npplli TVlPQP npplli <TT PVP-
OCe111' -^686 OC6111, Or BJQ

J^ differ> jn different in-

sects, as to the details of their structure ; but in general

Fig. 35.— Skull of Meianerpeton.

A Labyrinthodont amphibian from the Per-
mian of Bohemia (after Fritsch). X*. Pa.,
the parietal foramen.

The Senses of Animals. 289

they consist of a lens produced by the thickening of the
integumentary layer which is at the same time rendered

transparent. Behind
this lies the so-called
vitreous body, com-
posed of transparent
A. B. y^V cells, and then follows

Fig. 36.— Eyes and eyelets of bee. the retina, in which

A. Drone. B. Worker. t^ere are a number of

rods, the recipient ends of which are turned towards the
rays of light, and not away from them as in the vertebrate,
Spiders have from six to eight ocelli, arranged in a pattern
on the top of the head. Facetted eyes are not found in
them.

These facetted eyes, which are found in both insects
and Crustacea, have apparently a more complex structure
than the ocelli. Externally — in the bee, for example — the
surface is seen to be divided up into a great number of
hexagonal areas, each of which is called a facet, and forms
(in some insects, but not in all) a little lens. Of these the
queen bee has on each side nearly five thousand ; the worker
some six thousand ; and the drone upwards of twelve
thousand; while a dragon-fly (JSschna) is stated to have
twenty thousand. Beneath each facet (in transverse section,
Fig. 37) is a crystalline cone, its base applied to the lens, its
apex embraced by a group of elongated cells, in the midst
of which is a nerve-rod which is stated to be in direct con-
nection with the fibres of the optic nerve. Dark pigment is
developed around the crystalline cones. And retinal purple
is said to be present in the cells which underlie it.

With regard to these facetted eyes there has been much
discussion. The question is — Is each facetted organ an
eye, or is it an aggregate of eyes ? To this question the
older naturalists answered confidently — An aggregate. A
simple experiment seems to warrant this conclusion. If
the facetted surface be cleared of its internal structures
(the crystalline cones, etc.) and placed under the microscope,
each lens may, at a suitable distance of the object-glass,

u

290 Animal Life and Intelligence.

be made to give a separate image of such an object as a
candle reflected in tbe mirror of the microscope. If each
lens thus gives an image, is not each the focussing apparatus

of a single eye ? But a
somewhat more difficult
experiment points in
another direction. If the
facetted cornea be re-
moved with the crystalline
cones still attached (Gren-
acher was able to do it
with a moth's eye), and
placed under the micro-
scope, when the instru-
ment is focussed at the
point of the cone (where
Fig. 37.— Eye of fly. the nerve-rod comes), a

Transverw section through head. (After Hickson.) gp()t of }ightj and Q()t ftn

image, is seen. No image can be seen unless the micro-
scope be focussed for the centre of the cone ; and here there
are no structures capable of receiving it and transmitting
corresponding waves of change to the " brain."

But what, it may be asked, can be the purpose of an
eye-structure which gives, not an image, but merely a spot
of light ? The answer to this question can only be found
when it is remembered that there are thousands of these
facets and cones giving thousands of spots of light. The
somewhat divergent cones and facets of the insect's eye
(Fig. 37) embrace, as a whole, an extended field of vision ;
each has its special point in that field; and each conveys
to the nerve-rod which lies beneath it a stimulation in
accordance with the brightness, or intensity, or quality of
that special point of the field to which it is directed. The
external field of vision is thus reproduced in miniature
mosaic at the points of the crystalline cones — thus there is
produced by the juxtaposition of contiguous points a stippled
image. And it must be remembered that, even in human
vision, the stimulation is not that of a continuum, but is

The Senses of Animals.

291

stippled with the fine stippling of the ends of the rods and
cones. In insect-vision the stippling is far coarser, and the
image is produced on different principles.

In the vertebrate the image is produced by a lens ; in
the insect's eye, by the elongated cones. How this is effected
will be readily seen with the aid of the diagram. At a b
are a number of trans-
parent rods, separated by
pigmented material absorb-
ent of light. They repre-
sent the crystalline cones.
At c d is an arrow placed
in front of them ; at e f is

Fig. 38. — Diagram of mosaic vision.

a screen placed behind
them. Eays of light start
in all directions from any point, c, of the arrow ; but of these
only that which passes straight down one of the trans-
parent rods reaches the screen. Those which pass obliquely
into other rods are absorbed by the pigmented material.
Similarly with rays starting from any other point of the
arrow. Only those which, in each case, pass straight down
one of the rods reach the screen. Thus there is produced a
reduced stippled image, c' d', of the arrow.

There has been a good deal of discussion as to the
relative functions of the ocelli and the facetted eyes of
insects. The view generally held is that the ocelli are
specially useful in dark places and for near vision ; while
the facetted eyes are for more distant sight and for the
ascertainment of space-relations. How the two sets of
impressions are correlated and co-ordinated in insect-con-
sciousness, who can say ? *

The interesting observations of Sir John Lubbock seem
to show that insects can distinguish between different
colours. " Amongst other experiments," he says,f " I

* We must remember how largely the antennae are used when an insect is
finding its way about. Watch, for example, a wasp as it climbs over your
plate. If the antennae be removed, it seems to stumble about blindly. The
antennae seem almost to take the place of eyes at close quarters.

t " Senses of Animals," p. 194.

29 2 Animal Life and Intelligence.

brought a bee to some honey which I placed on a slip of
glass laid on blue paper, and about three feet off I placed
a similar drop of honey on orange paper. With a drop of
honey before her a bee takes two or three minutes to fill
herself, then flies away, stores up the honey, and returns
for more. My hives were about two hundred yards from
the window, and the bees were absent about three minutes
or even less. After the bee had returned twice, I transposed
the papers ; but she returned to the honey on the blue
paper. I allowed her to continue this for some time, and
then again transposed the papers. She returned to the
old spot, and was just going to alight, when she observed
the change of colour, pulled herself up, and without a
moment's hesitation darted off to the blue. No one who
saw her at that moment could have the slightest doubt
about her perceiving the difference between the two
colours."

Passing now to the Crustacea, we find in them eyes of
the same type as in insects ; but in the higher Crustacea
ocelli are absent. In the crabs and lobsters the eyes are
seated on little movable pedestals; in the former the
crystalline cones are very long, in the latter they are short.
There can be little doubt that vision is by no means want-
ing in acuteness in an animal which, like the lobster, can
dart into a small hole in the rocks with unerring aim from
a considerable distance. The experiments of Sir John
Lubbock have shown that the little water-flea (Daphnia) can
distinguish differences of colour, yellows and greens being
preferred to blues or reds.

Among the molluscs there are great differences in the
power of sight. Most bivalves, like the mussel, are blind.
Interesting stages in the development of the eye may be
seen in such forms as the limpet, Trochus and Murex. The
limpet has simply an optic pit, the Trochus a pit nearly
closed at the orifice and filled with a vitreous mass, and
the Murex a spherical organ completely closed in with a
definite lens. The snail has a well-developed eye on the
hinder and longer horn or tentacle. But it does not seem

The Senses of Animals. 293

to be aware of the presence of an object until it is brought
within a quarter of an inch or less of the tentacle. In all
probability the eye does little more than enable the snail
to distinguish between light and dark. And the same may
be said of the eye of many of the molluscs. In some,
however, the cuttle-fishes and their allies, the eye is so
highly developed that it has been compared with that of
the vertebrate. There is an iris with a contractile pupil.
And the ganglion with which it is connected forms a large
p^art of the so-called brain. The powers of accurate vision
in these higher forms are probably considerable.

It is interesting to note that whereas in the cuttle-fishes
and most molluscs, the rods of the retina are turned
towards the light, in Pecten, Onchidium (a kind of slug),
and some others, they are, as in vertebrates, turned from
the light. In Pecten the nerve to supply the retina bends
round its edge at one side. But in Onchidium it pierces
the retina as in vertebrates.

In worms, eyes are sometimes present, sometimes
absent. In star-fishes and their allies they often occur.
In medusse (jelly-fish) they are sometimes found on the
margin of the umbrella. Even in lowly organisms, like
the infusoria, eye-spots not unfrequently occur. We must
remember, however, that, in these lower forms of life, the
organs spoken of as eyes or eye-spots merely enable the
possessor to distinguish light from darkness.

Even when eyes or eye-spots are not developed, the
organism seems to be in some cases sensitive to light —
using the word "sensitive," once more, in its merely physical
acceptation. The earthworm, for example, though it has
no eyes, is distinctly sensitive to light ; and the same has
been shown to be the case with other eyeless organisms.
Graber holds that his experiments demonstrate that the
eyeless earthworm can distingush between different colours
— in other words, is differentially sensitive to light-waves
of different vibration-period — preferring red to blue or
green, and green to blue. And the same observer has
shown that animals provided with eyes — the newt, for

294 Animal Life and Intelligence.

example — can distinguish between light and darkness by
the general surface of the skin. M. Dubois, by a number
of experiments on the blind Proteus of the grottoes of
Carniola, has shown that the sensitiveness of its skin to
light is about half that of its rudimentary eyes ; and,
further, that this sensibility varies with the colour of the
light employed, being greatest for yellow light.*

We have not been able to do more than make a rapid
survey of the sense of sight as it seems to be developed in
the invertebrates and lower animals. The visual organs
differ, not only in structure, but in principle. We may, I
think, distinguish four types.

1. Organs for the mere appreciation of light or dark-
ness (shadow), exemplified by pigment-spots, with or with-
out concentrating apparatus.

2. Organs for the appreciation of the direction of light
or shadow, with or without a lens. The simple retinal eyes
of gasteropods, and perhaps in some cases the ocelli of
insects, probably belong to this class.

3. True eyes, or organs in which a retinal image is
formed, through the instrumentality of a lens, as in
vertebrates and cephalopods.

4. The facetted eyes of insects, in which a stippled
image is formed, on the principle of mosaic vision.

Unfortunately, all these are called indiscriminately
eyes, or organs of vision. An infusorian or a snail is said
to see. But the terms "eye," "vision," "sight," imply
that final excellence to which only the higher animals,
each on its own line, have attained.

This final excellence probably has its basis and earliest
inception in the fact that the functional activity of proto-
plasm is heightened in the presence of setherial vibrations.
If, then, we imagine, as a starting-point, a primitive
transparent organism with a general susceptibility to the
influence of light-vibrations, the formation within its
tissues of pigment-granules absorbent of light will render
the spots where they occur specially sensitive to the
. * See Nature, vol. xli. p. 407.

The Senses of Animals. 295

aetherial vibrations. Special refraction-globules would also
act as minute lenses, focussing the light, and thus concen-
trating it upon certain spots.

In many of the lower animals we find such organs,
belonging to our first category, and constituting either eye-
spots of pigmented material or simple lenses covering a
pigmented area. If we call these eyes, we must remember
that in all probability they have no power of what we call
vision — only a power of distinguishing light from dark.
Where, however, there exists beneath the lens a so-called
retina, that is," a layer of rod-like endings of a nerve, it
might, at first sight, be thought that there, at any rate, we
have true vision. But in all probability, in a great number
of cases the retinal rods are simply for the purpose of
rendering the organism sensitive, not only to the presence
of light, but to its direction. Light straight ahead (a) stimu-
lates the middle rods ; from one side (b, c) it is focussed on
the rods of the opposite side of
the retina ; and similarly for
intermediate positions. The
presence of a retinal layer is
thus no infallible sign of a
power of vision as apart from
mere sensibility to light. In-
deed, in a great number of c

' ., , Fig. 39.— Direction-retina.

cases, from the convexity and Simple retina for distinguishing the direction
position of the lens, the for-
mation of an image is impossible. Only when it can be
shown that a more or less definite image can be focussed
on the retina, or can be formed on the principle of mosaic
vision, can we justly surmise that a power of true vision
is present. I doubt whether this can be shown to be
unquestionably the case in any forms but the higher
arthropods, the cuttle-fishes and their allies, and the verte-
brates.

There is one more point for consideration before we
leave the sense of sight— Are the limits of vision the same
in the lower forms of life as they are in man ? or, to put

296 Animal Life and Intelligence.

the question in a more satisfactory form — Are the limits
of sensibility to light- vibrations the same in them as in us?
M. Paul Bert concluded that they are. But Sir John
Lubbock has, I think, conclusively shown that they are
not. For the full evidence the reader is referred to his
" Senses of Animals." * His experiments on ants, with
which those of M. Forel are in complete accordance,
satisfied him that these little animals are sensitive to the
ultra-violet rays which lie beyond the range of our vision.
Other experiments with fresh-water fleas (Daphnia) showed
that they have colour-preferences, green and yellow being
the favourite colours.

The daphnias were placed, in a shallow wooden trough,
divided by movable partitions of glass into divisions.
Over this was thrown a spectrum of rainbow colours. The
partitions were removed, and the daphnias allowed to
collect in the differently illuminated parts of the trough.
The partitions were then inserted, and the number of
crustaceans in each division counted. The following
numbers resulted from five such experiments : —

Dark. Violet. Blue. Green. Yellow. Bed.
0 3 18 170 36 23

Special experiments seem to show that their limits of
vision at the red end of the spectrum coincide approxi-
mately with ours ; but at the violet end their spectrum is
longer than ours. Sir John covered up the visible spectrum,
Rr> as to render it dark, and gave the daphnias the option
of collecting in this dark space or in the ultra-violet. To
human eyes both were alike dark. But not so to the
daphnian eye ; for while only 14 collected in the covered
part, 286 were found in the ultra-violet. The width of the
violet visible to man was two inches. Sir John divided
the ultra-violet into three spaces of two inches each. Of
the 286 daphnias, 261 were in the space nearest the violet,
25 in the next space, and none in the furthest of the three
spaces. From which it would seem that, though these
little creatures are sensitive to light of higher vibration-

* Chap. x. p. 202.

The Senses of Animals.

297

period than that which affects the human eye, their limits
do not very far exceed ours. We have seen that human
beings differ not a little in. their limits of violet-sus-
ceptibility. We may presume that Sir John Lubbock
and those who assisted him in these experiments were
normal in this respect. But it is possible that some indi-
viduals could have perceived a faint purple where there
was darkness to them, and that the majority of the 261
daphnias were collected in the region just beyond the
partition between ultra-violet and darkened violet. Still,
there is no cause for doubting the general conclusion that
daphnias are sensible to ultra-violet rays beyond the limits
of human vision.

Sir John Lubbock has an interesting chapter on pro-
blematical organs of sense. In the antennae of ants and

Fig. 40.— Antennary structures of hymenoptera. (After Lubbock.)

a., cuticle; b., hypodf-rmls; c., ordinary hair; d., tactile hair; e., cone; /., depressed
hair lying over a. cup with rudimentary hair at the base; &., simple cup; t., champagne-
cork-like organ of Forel ; k., flask-like organ ; Z., papilla, with a rudimentary hair at the apex.

bees there are modified hairs and pits in the integument
(at least eight different types, according to Sir John
Lubbock), the sensory nature of which is undoubted. But
what the sensory nature in each case may be is more or
less problematical. Many worms have sense-hairs or
bristles of the use of which we are ignorant. Some organs

298 Animal Life and Intelligence.

described as tactile or olfactory in the lower invertebrates
are so described on a somewhat slender basis of evidence.
The sense-value of the bright marginal beads of sea-
anemones is unknown. Even in animals as high in the
scale of life as fishes, there is a complete set of sense-
organs — the muciparous canals, in the head and along the
lateral line down the side, the function of which we can
only guess. By some they are regarded as olfactory ; by
others, as fitted to respond to vibrations or shocks of
greater wave-length than the auditory organ can appre-
ciate ; by others, as of importance for the equilibration or
balancing of the fish.

It will thus be seen that, apart from the possibility of
unknown receptive organs as completely hidden from
anatomical and microscopic scrutiny as the end-organs of
our temperature-sense, there are in the lower animals
organs which may be fitted to receive modes of influence
to which we human folk are not attuned.

And what are the physical possibilities ? We have seen
that, through the telaesthetic senses — hearing, vision, and
the temperature-sense — we are made aware of the vibra-
tions of distant bodies, the effects of which are borne to us
on waves of air or of aether. The limits of hearing with us
are between thirty and about forty thousand (or perhaps,
in very rare cases, fifty thousand) vibrations per second.
But these are by no means the limits of vibrations of the
same class. By experiments with sensitive flames,* Lord
Rayleigh has detected vibrations of fifty- six thousand per
second ; and Mr. W. F. Barrett has shown that a sen-
sitive flame two feet long is sensitive to vibrations beyond
the limit of his own hearing and that of several of his
friends who were present at the experiment. We have
some reason to suppose that vibrations too rapid to be
audible by man are audible by insects, but not much is
known with regard to the exact limits.

The following table shows what is known concerning

* The observations are not yet published, and I have to thank Lord
Rayleigh for his courtesy in allowing me to make use of this fact.

The Senses of Animals.

299

the aBther-vibrations. The figures are those given by
Professor Langley : —

Quality of radiations.

Limit of photography, arti-
ficial source

Limit of photography, solar
source

Limit of violet to normal

eyes

Limit of red to normal eyes
Probable inferior limit of
temperature-sensations . .
Longest waves hitherto re-
cognized with bolometer

Wave-lengths in Number of
thousandths of vibrations pel
a millimetre, second in billio

0-185
0-295

0-36
0-81

9-25*
30-0

160

833)
370 \

30
1

none known

vision.

temperature-

sense
none known

From this table it will be seen that, apart from the
possible extension of sight beyond human limits, there are
possibilities of another sense for the ultra-violet actinic
vibrations as different from sight as is the infra-red
temperature-sense. Moreover, the temperature-sense for
us has no scale ; there is nothing corresponding to pitch
in sound or colour in sight. It may not be so with lower
organisms. Insects, for example, may be sensitive to tones
of heat. The bee may enjoy a symphony of solar radiance.

I am not saying that it is so; I am merely suggesting
possibilities which we have not sufficient knowledge to
authoritatively deny. We have no right to impose the
limits of human sensation on the entire organic world.
Insects may have " permanent possibilities of sensation "
denied to us.

Even within our limits there may be, as we have
already seen, great and inconceivable differences. We saw

* Professor Langley finds that the maximum effect with a radiating
source at 170° C. is at about 5-0 thousandths of a millimetre wave-length.
„ 100° C. „ „ 7-5
0°C. „ „ 11-0

We are sensitive to radiations from a body at 100° C. But when the
temperature falls below the normal temperature of the body we are not
sensitive to heat-vibrations, but to loss of heat from the surface exposed. The
limit of sensibility to heat-vibrations, therefore, probably lies between 7'5 and

II thousandths of a millimetre. I have taken about 9-25 as the limit.

300 Animal Life and Intelligence.

that our own colour-sensations are probably due to the
blending and overlapping in different proportions of three
primitive monochromatic bands, but that in all probability
in birds the bands are different, and overlapping is largely
prevented. Their colour-phenomena must be inconceivably
different from ours. And what shall we say of the colour-
vision of invertebrates ? Are we justified in supposing that
for them, as for us, E., G., and V. are the unstable ex-
plosives, and that they are present in the same proportions
as with us ? If not, their colour-world cannot be the same
as ours. Of the same order it probably is. And all that
we can hope to do is to show, as has been shown, that
colours which differently affect us affect them also
differently.

In conclusion, we may return to the point from which
we set out. The organism is fitted to respond to certain
influences of the external world. The organs for the
reception of these influences are the sense-organs. When
they are stimulated waves of change are transmitted
inwards to the great nerve-centres; they are there co-
ordinated, and issue thence to muscles or glands. Thus the
organism is fitted to respond to the influences from without.
The activities of organisms are in response to stimulation.

We have seen that the cells of the organic tissues are
like little packets of explosives, and that the changes which
occur in the organism may be likened to their explosion
and the setting free of the energy stored up in them. The
end-organs of the special senses may be regarded as
charged with explosives of extreme sensitiveness. Some
are fired by a touch ; the molecular vibrations of sapid or
odorous particles explode others ; yet others are fired by
the coarser vibrations of sound ; others, once more, by the
energy of the aetherial waves. The visual purple is a highly
unstable chemical compound of this kind ; expose it for a
moment to light, and it topples over to a new molecular
arrangement, the colour being at the same time discharged.
If the retina has been removed from the body, this is all

The Senses of Animals. 301

that happens. But if (in the frog) it be replaced on the
choroid layer from which it has been stripped, the visual
purple is reformed. The explosive is thus reconstructed
and the sensibility is restored. Thus, as fast as the
explosives are fired off by sense-stimuli, so fast in normal
life are they reconstituted and the sensibility restored.
Meanwhile the explosion at the end-organs has fired the
train of explosives in the nerve, and created molecular
explosive disturbances in the brain. Thence the explosive
waves pass down other nerves to muscles or glands, and,
giving rise therein to further explosions, take effect in the
activities of the organism.

We shall have to consider these activities hereafter.
We must now turn to the psychical or mental accom-
paniments of the explosive disturbances in the brain or
other aggregated mass of nerve-cells.

302 Animal Life and Intelligence.

CHAPTER VIII.

MENTAL PROCESSES IN MAN.

I HAVE already drawn attention to the fact that the primary
end and object of the reception of the influences (stimuli)
of the external world, or environment, is to enable the
organism to answer or respond to these special modes of
influence, or stimuli. In other words, their purpose is to
set agoing certain activities. Now, in the unicellular
organism, where both the reception and the response are
effected by one and the same cell, the activities are for
the most part simple, though even among these protozoa
there are some which show no little complexity of response.
Where, however, the organism is composed of a number of
cells, in which a differentiation of structure and a specializa-
tion of function have been effected, certain cells are set
apart as recipients, while other cells are set apart to
respond (respondents). There is thus the necessity of a
channel of communication between the two. Hence yet
other cells (transmitters), arranged end to end, form a line
of connection and communication between the group of
receiving cells and the group of responding cells, and con-
stitute what we term a nerve. That which is transmitted
may still be called a stimulus, each cell being stimulated
in turn by its neighbour. Thus a stimulus must be first
received and then transmitted.

But little observation is required to convince us of the
fact that, in ifche higher creatures, a very simple stimulus
may give rise to a very complex response. A light pin-
prick will cause a vigorous leap in a healthy frog — a leap
that involves a most intricate, accurate, and complex

Mental Processes in Man. 303

co-ordination of muscular activities. And anatomical
investigation shows us that in such creatures there is
always, in the course of the channel of communication or
transmission, a group of closely connected cells, which
play the part of co-ordinants. In the vertebrate animals
these co-ordinants are collected in the brain and spinal
cord. In the insects, crustaceans, and worms they are
arranged in a knotted chain running close to the under
surface of the body. To this central nervous system, as it
is called, nerves (afferent nerves) run inwards from the
recipient organs. From it nerves (efferent nerves) run
outwards to the organs of response. And in it the trans-
mitted stimuli, brought in by the afferent nerves, are
modified, through intervention of the co-ordinants, into
stimuli carried out by the efferent nerves. A simple
stimulus may create a great commotion among the co-
ordinants of the central nervous system, and give rise to
many and complex stimuli going out to the muscles and
other organs of response. How this is effected is one of
the many wonders of the animal mechanism. We believe
that the connection and co-ordinations have gradually been
established during a long process of development and evo-
lution, reaching back far into the past. How, we can at
present scarcely guess.

We must picture to ourselves, then, in the animal
organism, a multitude of nerve-fibres running inwards
from all the end-organs of the special senses, from the
muscles, and from the internal organs, and all converging
on the central nervous system. And we must picture to
ourselves a multitude of nerve-fibres passing outwards from
the central system, and diverging to supply the muscles,
glands, and other organs which are to respond to the
stimulation from without. We must picture the fibres
coming from or going to related parts or organs collecting
together to form nerves and nerve-trunks, which are,
however, only bundles of isolated nerve-fibres. And,
lastly, we must picture the central nerve-system itself
co-ordinating and organizing the stimuli brought into it

304 Animal Life and Intelligence.

by afferent nerves, from the organs of special sense, and
handing over the resultants by efferent nerves to the
organs of special activities. So far we have purely
physiological effects, many of which occur with surprising
accuracy and precision when an organism is in a state of
unconsciousness. Place your finger in the palm of a
sleeping child, and the fingers will close over it without
the child awaking to consciousness. If, in a frog, the
brain of which has been extirpated, the side be touched
with a drop of acid, the leg of that side will be drawn up,
and the foot will be used to wipe away the acid. And if
that leg be held and prevented from reaching the side, the
other leg will be brought round so as to try and bring the
foot within reach of the irritated spot. The actions are,
however, in all probability, purely physiological, and are
performed in complete absence of consciousness.

When we turn from the physiological to the psycho-
logical aspect of the question, we enter a new world, the
world of consciousness, wherein the impressions received
by the recipient organs (no longer regarded as mere stimuli,
but as the elements of consciousness) are co-ordinated and
organized, and are built up into those sensations and
perceptions through which the objects of the external
world take origin and shape. It is with this process that
we have now to deal; and we will deal with it first in
man.

The first fact to notice is that, apart from sense-stimuli
received and exciting consciousness, we have also the
revival of past impressions. This revival is the germ of
memory. What exactly is the physical basis of memory,
how the effects of stimuli in consciousness come to be
registered, we do not know. It is clearly a matter that
falls under the general law of persistence ; but in what
organic manner we are largely ignorant. Still, there can
be no question of the fact that, quite apart from impres-
sions due to immediate influences of the environment now
acting on our recipient organs, we have also revivals of

Mental Processes in Man. 305

bygone influences of the environment — shadows or after-
images of previous modes of influence. Without this
process of registration and revival, stimuli could never
give rise to sensations and perceptions such as we know
them. Without it experience would be impossible.

We may say, then, that impressions (resulting from
stimuli) and their revival in memory are the bricks of the
house of knowledge ; and these' are built up through ex-
perience into what we call the world of things around
us. There may be and is a certain amount of mortar,
supplied by the builder, in addition to the elementary
bricks. But without the bricks no house of knowledge
could be built. Let us now examine the bricks and the
building.

From what we have already learnt in the chapter on
" The Senses of Animals," it is clear that the impressions
and their revivals in memory have differences in quality.
Here, on the very threshold of the subject, we must pause.
They have differences of quality. But in consciousness
these differences must be distinguished. And this involves
their recognition and discrimination, presupposing, there-
fore, a corresponding faculty, however simple, on the part
of the recipient. Without cognition and recognition (twin
sisters, born in the same hour) we can never get beyond
mere impressions; which may, indeed, be differentiated
physically, as different stimuli due to diverse action of the
environment, but are psychically undifferentiated. This
recognition and discrimination is thus the primary activity
of the recipient mind. Here is already some of the mortar
supplied by the builder. Memory is absolutely essential to
the process. The sense-impression of external origin gives
rise to an impression of similarity or dissimilarity, which is
part of the internal reaction to the external stimulus.
Thus impressions are raised to the level of sensations. A
sensation is an impression that has been discriminated
from others, and recognized as being of such and such a
nature. The impressions of the sense-organs as we know
them are thus not mere impressions, but impressions

x

306 Animal Life and Intelligence.

raised to the level of sensations, in so far as they are
recognized and discriminated.

Let us now glance at some of the differences in quality
recognized in sensation. First, we have the broadly dis-
tinguished groups of touches and pressures, temperature-
sensations, tastes, smells, sounds, sights, muscular sensa-
tions, and organic sensations from internal parts of the
body. And then, within each of these groups, there are
the more or less delicate and distinct shades of quality,
well exemplified in vision by the different colour-sensations,
in hearing by notes of different pitch, and in smell by the
varieties of scents and odours. Many of those sensations,
moreover, which are apparently simple, are in reality
compound. There are differences of quality in the note A
as sounded on a violin, a piano, and a flute ; and these
differences are due to different admixtures of overtones,
which fuse with the fundamental tone and alter its timbre.
So, too, with vision. The sensation given by a white disc
is a compound sensation, due to waves of different period,
which separately would give sensations of colour. Sensa-
tions, then, differ in quality.

They also differ in quantity or intensity. This needs
little illustration. As evening falls, the sight-sensations
derived from the surrounding objects grow more and more
feeble. They may remain the same in quality, but the
quantity or intensity gradually diminishes. So, too, in
music, the pianos and fortes give us differences in intensity
of sound-sensations.

Sensations also differ in duration. The stimulation
may be either prolonged or instantaneous. Two or more
sensations may, moreover, be simultaneous or successive.
Just as they may be either similar or different in quality
and in intensity, so they may be either simultaneous or
successive in time. Simultaneous sensations are best
exemplified in vision and through touch ; successive sensa-
tions are given most clearly by the sense of hearing,
through which we recognize a sequence of sounds.

And then, again, sensations not only differ in time, but

Mental Processes in Man. 307

they seem also to differ in place. A sensation of touch
may be referred to different parts of the body — the hand,
the foot, or the forehead. But here we open up an im-
portant question — Where do we feel a sensation, such as,
for example, that of pressure on the skin ? Common sense
answers, without hesitation, that we feel it at the particular
part of the body which is affected by the external stimulus.
I feel the pen with which I write with my finger-tips. And
common sense is perfectly right from its own point of
view. But it is a well-known fact that a person whose leg
has been amputated experiences at times tickling and
uneasiness in the absent member. This is due to irritation
of the nerve-ends in the stump of the limb. But the
sensations are referred outwards to the normal source of
origin of impressions, the effects of which were carried
inwards by the nerve affected. We shall have to consider
hereafter the nature of the relation between physiological
and psychological processes — the connection of mind and
body. Assuming for the present that psychical processes
have a physical basis in physiological processes, the fact
given above and others of like implication seem to show
that the sensation has for its physiological basis some
nerve-change in the central nervous system — in us, no
doubt, in the brain. Of course, it must be remembered
that the sensation, as felt, is a mental fact (using the word
" mental " in its broadest sense, as belonging to the
psychical as opposed to the physiological series). But it
would seem that the physiological accompaniment of this
mental fact is some nerve-change in the brain. This
nerve-change is caused by a stimulus having its origin in
the end-organ of the afferent nerve, and we naturally refer
the impression outwards to the place of its source of origin
under ordinary and normal conditions. In other words,
we localize it. That is what common sense means when it
says that we feel pressure at the finger-tips.

To account for this process of localization, it is supposed
that every sensation, apart from its special quality as a
touch, a taste, or a smell, has a more or less defined

3oB Animal Life and Intelligence.

spatial quality, or local sign, dependent upon the part of
the body to which the stimulus is applied. These local
signs have, doubtless, in the long run, been established by
experience — if under this term we may include a more or
less unconscious process, the outcome of evolution. But
they are so rapidly established in the individual, that we
are forced to conclude that we inherit very highly developed
aptitudes for localization.

The refinement of localization is very different in the
different senses. In smell and taste there seems no more
than a general localization in the organ affected — the nose
or the mouth. In hearing there is not much more, unless
we regard the discrimination of pitch as a mode of localiza-
tion. In touch (and temperature) the refinement is much
higher, but it varies with the part of the body affected.

If the back be touched by two points less than two
inches and a third apart, the sensation will be that of a
single point ; the finger-tips, however, can distinguish two
points separated by less than one-tenth of an inch ; and
the tip of the tongue is still more refined in its power of
discrimination, distinguishing as two, points separated by
less than the twenty-fifth part of an inch. So that the
tongue is about sixty times as refined in its discrimination
as the skin of the back. Moreover, the delicacy of localiza-
tion may be cultivated, so that in some cases the refine-
ment may, by practice, be doubled.

When we come to sight, the refinement of localization
reaches its maximum, the local signs in the retina showing
the highest stage of differentiation, the distance on the
retina between two points distinguishable by local signs
being, according to Helmholtz, not much more than -tflfoT
of an inch ('0044 millimetre), which nearly corresponds
with the space between two cones in the yellow spot.

We must remember that the presentations of sense are
in all cases given in a stippled form, that is, by the stimu-
lation of a number of separate and distinct points. In
vision the stippling is very fine, owing to the minute size
and close setting of the retinal cones. In the case of

Mental Processes in Man. 309

hearing, the stippling, if we may so extend the use of this
term, is also very fine, a§ is shown by the fact that
musicians can, according to Weber, distinguish notes
separated in the scale of sounds by only one-sixtieth part
of a musical tone. In touch the stippling is comparatively
coarse. But in all cases there is a stippling; and yet
from these stippled sensations the mind in all cases elabo-
rates a continuum. The visual image is continuous, not-
withstanding the retinal stippling and the existence of the
blind spot. When we lay our hands on a smooth table we
fill in the interstices between the sensational points, and
feel the surface as continuous. In all cases out of the
stippled sense-stimuli we form a continuum.

The next thing that we have to note is that it is not so
much the sensation itself, as that which gives origin to
it, that we habitually refer outwards to the recipient end
of the afferent fibre. In referring a sensation of touch to
a certain part of the skin, it is of something touching us
that we seem to be immediately conscious. We refer the
stimulus to an object in the external world, which we
localize, and which we believe to have given rise to the
sensation.

This, however, is more clearly seen in the case of
vision. When we look through the window and see an
object such as a house before us, we do not habitually
localize the sensation in a certain part of the retina, but
we refer the object to a particular position more or less
distant in the world around us. This projection of the
object outwards in a right line from the eyes is really a
marvellous process, though the wonder of it is lost in its
familiarity. It is the outcome of the experience of hundreds
of generations. And the experience is not gained through
vision alone, but through this in combination with other
senses and activities. We see an object, but we have to
go to it before we can touch it. It is not in contact with
us, but distant from us. Its outness and distance is a
matter of what is termed the geometry of the senses ; and
this geometry has been elaborated through many genera-

310 Animal Life and Intelligence.

tions of organized beings, from data given by sight, touch,
and the muscular sense. It is. true that I can now estimate
the distance of the house without going to it ; but my eyes
go to it, and I can feel them go. The panes of my window
are separated by iron bars. As I look from them to the
distant house and back to them again, I can feel my eyes
going from one to the other. The lens of the eye is
adjusted for near or far distance by the action of a ciliary
muscle, through which its anterior surface can be flattened,
returning again by its own elasticity to the more convex
form when the muscle ceases to act. Each eye, moreover,
is moved in its orbit by six eye-muscles, and in normal
vision the two eyes act as one organ. For near distances
they converge ; for far distances there is less convergence.
Through the muscular sense, which is here extraordinarily
delicate, we can feel the amount of accommodation and
convergence; and thus we can feel the eyes going to or
coming from a near and a distant object. Of course, we
are aided in judging or estimating distances by the apparent
size of the object when the real size is known, by the
clearness of its outlines in a slightly hazy atmosphere, and
so forth. But apart from such judgments, it would pro-
bably be impossible to perceive that an object is near or
distant in the absence of muscles of accommodation and
convergence affording the data of the muscular sense. Not
only the distance of two objects from the eye, but their
distance apart, can be measured by the aid of the muscular
sense as we move the eyes from one to the other. And in
us this is so delicate that, according to Weber, a distinct
muscular sensation is attached to a displacement of a
sensitive point of the yellow spot through less than ^Q^
of an inch.

Now, if it be true that the consciousness aroused by
objects around us, through sensation, is an accompaniment
of certain physiological changes in the brain, it is clear
that the localization of their points of origin in special
parts of the skin, and the outward projection of the objects
exciting vision, is an act of the mind quite distinct from

Mental Processes in Man. 3 1 1

the mere passive response in consciousness which we call
an impression, and more complex than that mental activity
which, through discrimination and recognition, converts the
bare impression into a sensation. It is, in fact, part of
that mental process which is called perception.* Sensa-
tion has nothing to do with the objects around us as such ;
it is by perception that we are aware of their existence.
Let us now follow the process of perception a little further,
always remembering that it involves certain activities of
the mind.

These activities are too often ignored. We often speak
of the senses as the avenues . of knowledge, and John
Bunyan, likening the soul to a citadel, spoke of the five
gateways of knowledge, Eye-gate, Ear-gate, Mouth-gate,
Smell-gate, and Feel-gate. Hence arises a vague notion
that through the eye-gate, for example, a sort of picture
of the external object somehow enters the mind. And this
idea is no doubt fostered by the fact that an inverted image
of the object is formed on the retina, though how the
inverted image is turned right way up again in passing
into the mind bothers some people not a little.f

* I use this term in a broad sense, as the process involved in the formation
of what I shall term constructs.

t And I may add it is not an easy matter to explain to those who have not
considered such questions. It is a matter of the correlation of the testimony
of the sense-organs. A boy stands before me. I go to him and touch him,
and pass my hands downwards from head to foot. Then I stand a little way
off and look at him. His image on my retina is inverted. But as I run my
eye over him I direct my eye downwards to his feet and upwards to his head.
I am not conscious that the stimuli are running upwards along the retinal image.
Thus my eye-muscles and my other muscular and tactile sensations seem to tell
me that he is one way upwards. The image on my retina tells me,, though I am
not conscious of the fact,, that he is the other way upwards. But he cannot
be both ! The testimony of one sense has to give way. One standard or the
other has to be adopted. Practically that of touch and the muscular sensations
is unconsciously selected, and sight-sensations are habitually interpreted in
terms of this standard. So long as the two are sufficiently accurately
correlated, the practical requirements of the case are met. And it is well
known that it is not difficult, with a little practice, to establish a new correlation.
This is indeed done every day by the microscopist, for whom the images are
all reversed by his instrument. He very soon learns, however, that to move
the object, as seen, to the left, he must push it to the right. A new correlation
is rapidly and correctly established.

312 Animal Life and Intelligence.

A much closer analogy is this : Something stands
without and knocks at the doorway of sense, and from the
nature of the knocks we learn somewhat concerning that
which knocks. In other words, at the bidding of certain
stimuli from without we construct that mental product
which we call the object of sense. It is of these mental
constructions — " constructs " * I will call them for con-
venience— that I have now to speak.

In a fruiterer's shop on the opposite side of a street I
see an orange. That is to say, certain cones of the retina
of my eye are stimulated by light-waves of a yellow quality,
and at the bidding of these stimuli I construct the object
which I call an orange. That object is distant, roundish,
yellow, resisting and yet somewhat soft, with a peculiar
smell, and possessed of a taste of its own. Now, it is
obvious that I cannot see all these qualities of the orange,
as we call them. I construct the object on reception of
certain light-waves which are focussed on the retina of my
eye. If I go to the orange, however, I can test the correct-
ness of my construct by the senses of touch, smell, and
taste. But what led me to construct an object with these
qualities ? Experience has taught me that these qualities
are grouped together in special ways in an orange. I
constructed that particular object through what is termed
the principle of association. I have learnt that these
qualities are grouped together in certain relations to each
other, and when I actually receive sight-stimuli of a certain
quality, grouped in certain ways, they immediately call up
the memories of the associated qualities. That which is
actually received is a mere suggestion, the rest is sug-
gested in memory through association. The object might
be suggested through other senses. I come into a dining-
room after dessert, and the object is suggested through
smell. Or my little son says, " Open your mouth and
shut your eyes, and see what the fairies will send you ; "
and an orange is suggested by taste. In all these cases

* I nse tins term because the word " percept " is used in different senses by
different writers, e.g. by Mr. Mivart and Mr. Romanes.

Mental Processes in Man. 313

the object is constructed at the bidding of certain sensa-
tions, which suggest to my mind the associated qualities.
The object is a construct.

And here let us notice that we ascribe the form, the
resistance, the taste, the smell, to the object. We do not
say or think, " Sight-sensations inform me that there is
something which I call an orange, and which is capable of
exciting in me sensations of touch, taste, and smell ; " but we
say, " There is an orange, which has such and such a taste,
smell, and feel." In other words, we refer these sensations,
related in certain ways, outwards to the object, and name
them qualities of the object that we see. But remember,
that we do not necessarily or normally say or think any-
thing about it. We just inevitably construct the object,
what we build in to the construct depending upon associa-
tion through experience.

At this stage, perhaps, Common Sense steps in, and,
shaking his head, says, with characteristic bluntness,
" Nonsense ; you'll never persuade me that the things I
see and feel around me are nothing but fictions of my own
mind. I don't construct them, as you call it ; there they
are for me to see and feel and taste if I will." Now,
Common Sense is a sturdy, hard-headed individual, with
whom I desire to keep on friendly terms. And I therefore
hasten to explain that I most fully agree with every word
that he says. The orange that I see before me is not a
mere fiction of my mind. I can, if I will, take it up, feel
it, smell it, and taste it. If it will satisfy Common Sense,
I will say that it is the idea of the orange that I construct.
Only I think that Common Sense, who has a horror of
roundabout and indirect statements, will not like my say-
ing, " I am receiving certain visual sensations related in
certain ways, which lead me to construct an idea of an
orange." He will prefer my saying simply, "I see an
orange." Since what he wants me to call our ideas of things
answer point for point to the things as they actually exist
for us human-folk, it is not only more satisfactory but more
correct to merge the two in one, and- speak directly and

314 Animal Life and Intelligence.

simply of the object. The object is a thing I construct.
That it is real may be proved by submitting it to the test
of all the senses that I have.

And what do I mean by " real " ? I mean that what it is
for me it is also for you and any other normally constituted
human being. This is, in truth, the only common-sense
criterion of objective reality. Some people are colour-blind,
and tell us that a rose is not red, but green. We reply
that it is really red, but that, through a defect of sight,
they cannot distinguish its redness. Here we take the
normal human being as a standard for objective reality.
For him the rose is red. And this is the only practical
criterion that we have. This, however, does not satisfy
some people, who think that the objects around them have
the same reality, independent of man, that they have for
us human-folk. Annihilate, they say, every human being
— nay, all life — and the objects will remain as they are,
and retain the same reality. Yes, the same reality ; which
means that if just one fortunate fellow escaped annihilation,
he would find them all just as they were. And this nobody
doubts. Nevertheless, it is (to me, at least) inconceivable
that things independently of us are what they appear to
us. Think of what we learnt about the sensations. They
all arose in stimulations of the end-organs of special sense.
Thence the explosive waves of change passed inwards to
the brain, and somewhere therein gave rise to mental pro-
ducts. These mental products, the accompaniments of
nerve-changes, can in no sense be like the outside some-
thing which gave rise to them. They are symbols of that
outside something. And it is these symbols that we build
up into objects. Hence I said that it is not only more
satisfactory and convenient, but more correct, to speak
directly of the object as constructed, and not our idea of
the object. The mental product is the object for us, not
only for me, but for you and all normal human beings,
since the object is the same for all of us. And hence, also,
I said that the analogy of gateways, through which pictures
of objects gain access to the mind, was false and misleading,

Mental Processes in Man. 315

and that a truer analogy is that something stands without
and knocks at the doorway of sense, and that from the
nature of the knocks we learn somewhat concerning that
which knocks. The person inside can never open the door
to see what manner of thing it is which knocks. But he
can build up a most cunning symbolism of knocks which
Bhall suffice for all practical purposes. In other words,
the object-world, symbolic though it is, which you and I
and the rest of us construct at the bidding of something
without us (the existence of which I assume), is amply
sufficient for all our practical needs, and constitutes the
only practical reality for human-folk.

I am well aware that there are many people who
cannot bring themselves to believe in, or even to listen
without impatience to, the view that the world we see
around us is a world of phenomena. It is absurd, they
say, to tell us that yonder tulip,'as an object, is in any
sense dependent on our perception of it. There it is, and
there it would have been had man never been created.
Can one conceive that the new species, of fossil, which was
only yesterday disentombed from the strata in which it has
lain buried for long ages, is dependent on man's observa-
tion for its qualities as an object? To say that it was
"constructed" by the lucky geologist who was fortunate
enough first to set eyes on it is sheer nonsense. Its shelly
substance protected a bivalve mollusc millions of years
before man appeared upon the earth. When we see the
orange in the fruiterer's shop, the sight of it merely
reminds us of its other qualities — its taste, its smell, its
weight, and the rest, which are essentially its own, and no
endowments of ours — nowise bestowed upon it by us.

I have no hope of convincing, and not much desire to
convince, one who thus objects. I would merely ask him
how and when he stepped outside his own consciousness to
ascertain that these things are so. Does he believe that
consciousness is an accompaniment of certain nervous pro-
cesses in the grey cortex of the brain '? If so, let him tell
us how these conscious accompaniments resemble (not

316 Animal Life and Intelligence.

merely symbolize, but resemble) tulips and oranges and
fossil molluscs. If not, let him propound his new theory
of consciousness.

Let it not be supposed that I am denying the existence,
and the richly diversified existence, of the external world.
We are fully justified, I think, in believing that, correspond-
ing to the diversity of mental symbolism, there is a rich
diversity of external existence. But its nature I hold that
we can never know. The objects that we see are the joint
products of two factors — the external existence and the
percipient mind. We cannot eliminate the latter factor
so as to see what the external factor is like without it.
Those who, like Professor Mivart,* say that we can
eliminate the percipient factor, and that the external world
without it is just the same as it is with it, are content to
reduce the human mind, in the matter of perception, to
the level of a piece of looking-glass.

There are some people who seek to get behind
phenomena by an appeal to evolution. It will not do
nowadays, they say, to make the human mind a starting-
point in these considerations ; for the human mind is the
product of evolution, and throughout that evolution has
been step by step moulded to the external world. The
external world has, therefore, the prior existence, and to it
our perceptions have to conform. All this is quite true ;
but it is beside the point. Mind has, throughout the
process of evolution, been moulded to the external world ;
our perceptions do conform to outside existences. But
they conform, not in exact resemblance, but in mental
symbolism. They do not copy, but they correspond to,
external existences. It is just because, throughout the
long ages of evolution, mind has lived and worked in this

* " Let the perception be considered to be made up of x + y ; x being
the ego, or self, and y the object. The mind has the power of supplying ita
own — z, and so we get (through the imagination of the mind and the object)
x +y — x, or y pure and simple " (Mivart, " On Truth," p. 135). Mr. Mivart
devotes a whole section of this work to the defence of ordinary common-sense
realism. The above assertion seems to contain the essence of his teaching in
the matter.

Mental Processes in Man. 3 1 7

symbolic world that common sense is unable to shake off
the conviction that this is the only possible world, and
exists as such independently of mental processes. The
world of phenomena is the world in which we, as conscious
beings, live and move. No one denies it. But it is none
the less a symbolic world; none the less a world which
mind has constructed in the sense that it is an inalienable
factor in its being.

Each of us, when we perceive an object, repeats and
summarizes the constructive process which it has been the
end of mental evolution to compass. Hence it is that, at
the bidding of a simple impression, percepts or constructs
take origin and shape in the mind. In taking possession
of this faculty in the early years of life, we are entering
upon a rich ancestral heritage. But if what I have been
urging has truth, what we call objects are human con-
structs, and cannot by any manipulation be converted into
anything else.

I will now take another and more complex case of
construction, which will bring out some other facts about
what I have termed " constructs." I hear in the street a
piercing howl, which suggests a dog in pain. Eising from
my seat and going to the window, I see a white terrier
with a black patch over the left eye limping down the road
on three legs. Now, what was the nature of the construct
framed at the bidding of the piercing howl ? A dog in
pain. But what dog ? The nature of the howl suggested
a small dog ; but there was nothing further to particularize
him. The construct was, therefore, exceedingly vague and
ill denned, and was not rendered definite and particular
till I went to the window, and saw that it was a white
terrier with a black patch over the eye. The howl, more-
over, suggested certain activities of the dog. The construct
was not merely a passive, inanimate object, like the orange,
but an object capable of performing, and actually perform-
ing, certain actions. Here, again, we can only say that it
is through experience that special activities are associated
with certain objects. Just as the construct orange is

318 Animal Life and Intelligence.

capable of exciting sensations of taste, so the construct dog
is capable of doing certain things and performing certain
actions, that is, of affecting us in certain further ways.

But, further, the howl suggested a dog in pain. No
amount of sensations entering into any manner of relations
could give me that element of the construct. I can neither
see, touch, taste, smell, nor hear pain in another being.
Pain is entirely subjective and known only to the sufferer.
But I have been a sufferer. I have experienced pain and
pleasure. And just as my experiences, individual and
ancestral, lead me to project into inanimate objects certain
qualities, the products of my sensations, so do my ex-
periences, individual and ancestral, lead me to project into
certain animals feelings analogous to those I have myself
experienced. This is sometimes described as an inference.
But if we call this an inference, then we must, I think, call
the taste, smell, and feel of the orange I see before me
inferences. In both cases the inference, if we so call it,
enters at once into the immediate construct.

And when I went to the window and saw the dog limp-
ing down the street, I saw also a small boy, with arm
drawn back, in the act of throwing a stone. In other
words, I saw the objects in the scene before me standing in
certain relations to each other. I concluded that the boy
had thrown a stone at the dog and was about to throw
another. In other words, I saw the scene before me as
part of a sequence of events.

One more example I will give to bring out another and
important feature in the mental process. Strolling before
breakfast in early spring in my friend's garden, there is
borne to me on the morning air a whiff of violet fragrance.
Not only does this lead me to construct violets, but it
reminds me of a scene in my childhood with which the
scent of these flowers was closely associated. Not only is
the object constructed, but a scene with which their fragrant
odour has been associated is reconstructed in memory. The
violets are immediate constructs or presentations of sense ;
the remembered scene is a reconstruct or representation in

Mental Processes in Man. 319

memory. So, too, when I heard a piercing howl in the
street, the dog I constructed was a vague presentation of
sense ; but the street in which I instinctively placed him
was a reconstruct or representation in memory. The
difference between a construct or presentation of sense, and
a reconstruct or representation in memory, is that the
former is directly suggested through the immediate action
of some quality or activity of the object, while the latter is
indirectly suggested through some intermediate agency.

Before proceeding further, let us review the conclusions
we have thus far reached. Through the action of certain
surroundings on our sensitive organization, we receive
certain impressions, and among these impressions and
others revived in memory we recognize certain similarities
or differences in quality, in intensity, in order of sequence,
and in source of origin. The sensations which thus
originate are mental facts in no sense resembling their
causes, but representing them in mental symbolism. The
consciousness of similarity or difference is no part of the
impression, but a further mental fact arising out of
the impression, and with it giving origin to sensation. It
deals with the relation of impressions among each other
and to the recipient. It involves recognition and dis-
crimination. Its basis is laid in memory. The sensations
are instantly localized, referred to objects, and projected
outwards, mainly through the instrumentality of the
muscular sense. The mental symbolism is thus built into
the objects around us, and constructs are formed. But
into the tissue of these constructs are woven, not only the
sensations immediately received, but much that is only
suggested through association as the outcome of past
experience, individual and ancestral. The constructs and
their associated reconstructs are thus endowed with
qualities which have practical reality, since they are not
for me only, but for you and for mankind. They are,
therefore, in a sense independent of me, but nowise
independent of man.*

* If it be said that the object does exist independently of man, though not

320 Animal Life and Intelligence.

Some of the constructs are endowed with activities,
and some with feelings akin to our own. Finally, in the
field of vision which we construct or reconstruct, the objects
are seen to stand in relationship to each other, and the
scene as a whole is perceived to be part of an orderly
sequence of events.

We have already got a long way beyond the impressions
with which we started ; and yet, if I may trust my own
experience, such construction as I have described is direct
and immediate. A child of four or five would not only
construct as much, but might not improbably go a long
way further, and say, " Naughty boy to throw a stone at
poor doggie ! " It is, I say, direct and immediate, and it
implies a wonderful amount of mental activity. Some
people seem to imagine that in the simpler forms of per-
ception, as when I see an orange on the table, the mind is
as passive as the sensitive plate in a photographer's camera.
This surely is not so. It is a false and shallow psychology
which teaches it. Just as a light pin-prick may set agoing
complex physical activities in the frog, so may compara-
tively simple visual sensations give rise to complex mental
activities in construction and reconstruction. It is to
emphasize this mental activity that I have persistently
used the terms "construct" and "construction." And I
wish to emphasize it still further by saying that without
the active and constructive mind no such process of con-
struction or reconstruction is possible or (I speak for
myself) conceivable. We might just as well suppose that
the frog could leap away on stimulation of a pin-prick in
the absence of its complex bodily organization, as that
sensation could give rise to construction and reconstruc-
tion in the absence of a highly organized mind.

We have seen that when a howl suggested the construct
dog, that construct was vague and undefined ; but when I

in the phenomenal guise tinder which we know it, I would reply — Not so ;
for it is to the existence under this phenomenal guise that we apply the word
" object." In philosophical language, the existence, stripped of its pheno-
menal aspect, is called the Ding an 8ich. Its essential character is ita inde-
pendence of man ; and hence its unknowability.

Mental Processes in Man. 321

went to the window and saw the terrier, the construct
became particularized and denned. This seems to me the
normal order of development : first the vague, general,
and indefinite; then the particular, special, and defined.
That which is immediately suggested at the bidding of
sensations received is always more or less general ; it only
becomes specialized on further examination physical or
mental — first a dog or an orange ; then this dog or this
orange. The more unfamiliar the object, the more vague
and indefinite the construct. The more familiar the object,
and the further our examination of it is carried, the more
particular and defined the construct. I would, therefore,
mark two stages in the process of construction : first, the
formation of constructs by immediate association, more or
less vague, indefinite, and ill defined ; and, secondly, the
definition of constructs by examination, by which they are
rendered more definite, particular, and special, and supple-
mented by intelligent inferences.

I need not stay here to point out the immense im-
portance vof this process of defining and particularizing
constructs, or the length to which it may be carried ; nor
need I pause to indicate how, through memory and
association, representative or reconstructive elements crowd
in to link or weave the constructs into more or less vivid
and brilliant scenes. But I have next to notice that out
of this intelligent examination arises a new, distinct
mental process, the analysis of constructs.

This process involves the paying of special attention to
certain qualities of objects, to the intentional exclusion of
other qualities. "When I cease to examine an orange as a
construct, and pay attention to its colour or its taste to the
exclusion of other properties, with the purpose of comparing
this colour or taste with other colours and tastes, I am
making a step in analysis. So, too, when I consider the
form of an orange for the purpose of comparing it with the
form of the earth, I am making a step in analysis. And,
again, when I consider the howl of the dog with the object
of comparing it with other sounds, I am making a step in

Y

322 Animal Life and Intelligence.

analysis. We may call the process by which we select a
certain quality, and consider it by itself to the neglect of
other qualities, isolation, and the products of the process
we may term isolates*

This process could not be initiated till a large body of
constructive and reconstructive experience had been gained.
But once initiated, there is no end to the process. We
pick to pieces all the phenomena of nature, all the qualities
and relationships of objects, the activities and functions of
animals, the mental phenomena of which we are conscious
in ourselves. We isolate the qualities, relationships, feel-
ings ; and we name the isolates we obtain. Hence arises
all our science, all our higher thought. In the terms
which we apply to our isolates consists the richness of our
language.

We name the isolates ; that is, we apply to each an
arbitrary symbol to stand for the isolated quality or rela-
tion. All words (except the obviously onomatopoetic, such
as " bow-wow," " cuckoo," etc.) are arbitrary symbols
associated with objects, or qualities, or relations, or other
phenomena. And abstract names of isolates are, so to
speak, the pegs on which we hang the qualities we have
separated by analysis and isolation, while class-names are
pegs upon which we can hang a group of similars reached
by the process of isolation ; for all classing and grouping
of objects, or qualities, or relations involves, so far as the
process is a conscious one, the principle of analysis. In
classing objects, we group them in reference to certain
characters which they have in common, disregarding
certain other characters in which they differ. We group
together, for example, sights, or sounds, or smells, and
distinguish them from each other and from tastes and
touches. And then we go further, and class all these
together as sensations having certain characteristics in
common whereby they are distinguished from perceptions
of relation arid so forth.

* I avoid, for the present, the use of the terms " abstraction " and " abstract
idea " because they are employed in different senses by different authors.

Mental Processes in Man. 323

Perhaps it may be objected that clasBification comes
much earlier in the mental process than I am now putting
it. It may be said that the recognition of a sensation as
a touch, or a smell, or a sound involves a classification of
sensations in these categories, and that the simple percep-
tion of an orange involves the placing of the object in
this class of bodies. And, undoubtedly, we have here the
germs of the process. Sensation and perception give us
the materials for classification ; the perception of similarity
and difference gives us the sine qua non of the process.
Nevertheless, although there may be an earlier unconscious
grouping of phenomena, it is only when the mind is
specially directed to these materials, with the object of
grouping them according to their similarities, that we can
speak of classification proper — conscious and intentional
classification, as opposed to unconscious grouping. And
this involves the intentional selection of the points of
similarity, and discarding or neglecting the points of
difference. It involves the process of analysis or isolation.
There is a vast difference between the perceptual recogni-
tion of objects as similar, and conceptual classification
on grounds of similarity. Just as the recognition of a
sensation as now and not then, or here and not there, or
as due to something outside us, gives us the germs from
which, on ultimate analysis, our ideas of time, space, and
causation are reached; so does the recognition of these
sensations as of this kind and not that give us the germ
from which, on analysis, the process of classification may
arise. True, conscious, scientific classification is late in
development.

And here let us notice that the conclusions we have
reached in this chapter are the outcome of analysis and
classification. The sensations with which we started are
isolates. In considering their quality, intensity, sequence,
we were isolating and classifying these special modes of
their existence. Localization and outward projection in-
volved isolation. We simply see the orange before us. To
understand and explain how we come to see it as we do

324 Animal Life and Intelligence.

see it involves a somewhat subtle analysis. We perceive
it to be yellow, round, resistant ; and then, isolating these
qualities, we reach conceptions of yellowness, roundness,
and resistance, quite apart from oranges. Throughout our
description the terms we used were very largely terms
denoting classified isolates.

Lastly, having enormously increased our knowledge by
this process of isolation, we proceed to build in the know-
ledge thus gained to the structure of our constructs. This
is the third and last stage in construction. The first stage
is the formation of indefinite constructs by immediate
association ; the second is the definition of constructs by
examination ; and the third is the completion of constructs
by synthesis.

And the further this process of analysis and isolation
is carried, the more we are, so to speak, floated off from
the immediate objects of sense into the higher regions of
abstract thought. Furthermore, by recombining our iso-
lates in new modes and under new relations, we reach the
splendid results of constructive imagination.

In the brief description which I have now given of our
mental processes, I have for the most part avoided certain
terms which are current in the science of psychology. It
will be well here to say a few words concerning these words
and their use. The process of sensation is sometimes
defined as the mere reception of a sense-stimulus. But
it is more convenient, and more in accordance with common
usage, to call the simple result of a stimulus an impres-
sion, and to apply the term "sensation " to the discrimina-
tion and recognition of the impressions as of such and such
a quality. Sensation, then, is the reception and discrimina-
tion of impressions which result from certain modes of
influence (stimuli) brought to bear on our organization.
Viewed in this way, therefore, even sensation involves a
distinct reaction of the mind ; it implies the first stage of
mental activity. But when the sensations are given
objective significance, when they suggest the existence of
an object- world without us, they enter the field of percep-

Mental Processes in Man. 325

tion. Here the discriminated sense-impression is, to use
the words of Mr. Sully, " supplemented by an accompani-
ment or escort of revived sensations, the whole aggregate
of actual and revived sensations being solidified or inte-
grated into the form of a percept; that is, an apparently
immediate apprehension or cognition of an object now
present in a particular locality or region of space."*
Throughout the whole process of the formation of con-
structs by immediate association, and their definition by
examination, we were dealing with perception and percepts.
But when we reach the stage when particular qualities
were isolated, then we enter the field of conception. The
isolates are concepts. Class-names, reached through pro-
cesses involving isolation, stand for concepts. And com-
pleted constructions, involving synthesis of the results of
analysis, contain conceptual elements. The word " con-
cept," however, is used in different senses by different
authors. Mr. Sully says,f for example, " A concept,
otherwise called a general notion, or a general idea, is
the representation in our minds answering to a general
name, such as ' soldier,' ' man,' ' animal.' . . . Thus the
concept ' soldier ' is connected in my mind with the repre-
sentations of various individual soldiers known to me.
When I use the word ' soldier/ . . . what is in my mind
is a kind of composite image formed by the fusion or
coalescence of many images of single objects, in which
individual differences are blurred, and only the common
features stand out distinctly. . . . This may be called a
typical or generic image." But Noire, quoted by Professor
Max Miiller,} taking another illustration, says, " All trees
hitherto seen by me leave in my imagination a mixed
image, a kind of ideal presentation of a tree. Quite
different from this is my concept, which is never an image."
I follow Noire ; and I hold that the image, in so far as it
is an image, whether simple or composite, § is a percept;

* " Outlines of Psychology," p. 153. f Ibid. p. 339,

J " Science of Thought," p. 453.

§ For compound or generic ideas "not consciously fixed and signed by

326 Animal Life and Intelligence.

but that, in so far as there enter into the idea of the
soldier or the tree elements which have been isolated by
analysis, just in so far does the word " soldier " or " tree "
stand for a concept. How far a word stands for a percept,
and how far there enter conceptual elements, depends to
a large extent on the level of intelligence of the hearer.
The moment educated and intellectual folk begin to think

means of an abstract name," Mr. Romanes (" Mental Evolution in Man," p.
36) has suggested the term " recept." In the photographic psychology which
he adopts, the percept is an individual and particular photograph, the recept a
generalized or composite photograph. " The word ' recept,' " he says, " is seen
to be appropriate to the class of ideas in question, because, in receiving such
ideas, the mind is passive." This, it will be observed, is in opposition to the
teaching of this chapter, in which the activity of the mind in perception has
been insisted on. Mr. Romanes's recepts answer in part to what I have
termed constructs, which, as we have seen, are, as a rule, from the first general
rather than particular, and in part to concepts reached through analysis. Mr.
Romanes, for example, speaks of ideas of principles (e.g. the principle of the
screw) and ideas of qualities (e.g. good-for-eating and not-good-for-eating) as
recepts (p. 60). On the other hand, Mr. Mivart (" The Origin of Human
Reason," p. 59 ; see also his work " On Truth ") terms such generic affections
'• sensuous universals." It may be well to append Mr. Romanes's and Mr.
Mivart's tabular statements.

Mr. Romanes.

(General, abstract, or notional = Concepts.
Complex, compound, or mixed = Recepts, or

generic ideas.

{ Simple, particular, or concrete = Memories of per-
cepts.

Mr. Mivart.

-_, / General or true universals = Concepts.

IDEAS \Particularorindividual = Percepts.

Groups of actual experiences |

SENSITIVE COGXI-

combined with sensuous

.1., or recepts.

1 Groups of simply juxtaposed^ . Sense-perceptions,
actual experiences / or sencepts.

In Mr. Mivart's terminology, the representations of the lower group are
"mental images" or " phantasmata." The term " consciousness " is by him
restricted to the higher region of ideas, the term " consentience " being applied
to the faculty by which cognitive affections are felt, unified, and grouped
without consciousness. There is a difference in kind, according to Mr. Mivart,
between " consentience " and " consciousness ; " and the former could therefore
never develop into the latter, nor the latter be evolved from the former. For
this reason (because of the philosophy it is intended to carry with it) I shall
not employ the word "consentience," which would otherwise be a useful
term.

Mental Processes in Man. 327

about their words, or the objects for which they stand,
conceptual elements are sure to crowd in.

There is one more feature of these mental processes in
man, and that by no means the least important, that
remains for brief consideration. I began by saying that
the primary end and object of the reception of the influences
of the external world, or environment, is to enable the
organism to answer to them in activity. We saw that the
sight of an orange suggests, through association, its taste ;
and that the validity of the association could be verified by
going to the orange and tasting it. We saw, too, that
when I heard a dog howl in the street, and, going to the
window, saw a small boy with a stone in his hand, I con-
cluded that he was going to throw it at the dog. What I
wish now to elicit is that out of perceptions through asso-
ciation there arise certain expectations, and that the
activities of organisms are moulded in accordance with
these expectations.

It is clear that these expectations or anticipations
belong partly to the presentative or constructive order, and
partly to the reconstructive or representative order. They
are in some cases directly suggested by the presentations
of sense ; they are also built up out of representations
which have become associated with the constructs in
memory and through experience. But what we have here
especially to notice about them is that, in the latter case,
they involve more or less distinctly the element which we,
in the language of our developed thought, call causation.
There is a sequence of events, and the perception of certain
of these gives rise, through association and experience, to
an expectation of certain succeeding phenomena. Expecta-
tions are, therefore, the outcome of the linked nature of
phenomena. And when we come eventually to think about
the phenomena, and how they are linked together into a
chain (successional) or web (coexistent), we reach the con-
ception of causation as the connecting thread. In early
stages of the mental process, such a conception does not
emerge. Nevertheless, the phenomena are perceived as

328 Animal Life and Intelligence.

linked or woven. And the mental process by which we
pass from any perceived event or existence to other pre-
ceding, concomitant, or subsequent events or existences
linked or woven with it in the chain or web of phenomena,
we call inference* When, for example, I find a footprint
in the sand, I infer that a man has passed that way ; and
when the clouds are heaped up heavy and black, I infer
that a storm is about to burst upon us.

Concerning inference, of which I shall have more to
say in the next chapter, I have now to note that it is of
two kinds : first, perceptual inference, or inference from
direct experience ; secondly, conceptual inference, or infer-
ence based on experience, but reached through the exercise
of the reasoning faculties. The latter involves the process
of analysis or isolation ; the former does not. There is a
marked difference between the two. Perceptual inferences
are the outcome of practical experience, but do not go
beyond euch practical experience. Conceptual inferences
are also based on experience, but they predict occurrences
never before experienced. Perceptual inferences, again,
deal with matters practically; but conceptual thought
explains them.

The expectation of a storm when the thunder-clouds are
heavy is a case of perceptual inference. It is the outcome
of a long-established association, and is not reached by a
process of reasoning involving an analysis of the pheno-
mena. But if, though the sky is clear, a west wind and
a rapidly falling barometer lead me to predict rain, the
inference is conceptual, and gained by me or for me by a
process of reasoning ; for the barometer was the outcome
of the analysis of phenomena. In the mind of the rough
sailor-lad, however, the fall of the mercury and the suc-
ceeding storm may be connected by mere perceptual

* We do not speak of the filling in the complement of a percept (the con-
struction of the object at the bidding of a simple impression) as a matter of
conscious inference. I do not consciously infer that yonder moss-rose is
scented. Scent is an integral part of the construct. From the appearance of
the rose, I may, however, infer that a rose-chafer has disturbed its petals.
The complement of the percept, if inferred at all, is unconsciously inferred.

Mental Processes in Man. 329

inference, the phenomena being simply associated together.
If, however, there is any attempt at explanation, correct or
incorrect, there is so far a conceptual element. In a little
fishing-village on our south coast, a benevolent lady
presented the fishermen with a Fitzroy barometer. I
happened shortly after to remark to one of the men that
the summer had been unusually stormy. " Yes, sir," he
said, " it has. But then, you see, the weather hasn't no
chance against that new glass." Here there was an
attempted explanation of the phenomena. The falling
glass was conceived as somehow causing bad weather.

It is hard to draw the line between perceptual and con-
ceptual inferences, or rather to say, in this or that case, to
which class the inference belongs, because man, through
language, lives in a conceptual atmosphere. Moreover,
the same result may, in different cases, be reached by per-
ceptual or by conceptual inference. A child who had seen
a great number of ascending balloons might, on seeing a
balloon, expect it to ascend by a perceptual inference ; but
a man, knowing that the balloon was full of a gas lighter
than air, might expect it to ascend through the exercise of
conceptual inference. And just as in adult civilized life
our constructs have more and more conceptual elements
built into them, so do our inferences become more and
more reasoned. It is probable that in an adult English-
man every inference has a larger or smaller dose of the
conceptual element.

With the development of language we state our in-
ferences in the form of propositions, and call them
judgments. " Every proposition," says Mr. Sully,* " is
made up of two principal parts : (1) the subject, or the
name of that about which something is asserted ; (2) the
predicate, or the name of that which is asserted. Thus,
when we affirm, ' This knife is blunt,' we affirm or
predicate the fact of being blunt of a certain subject,
namely, 'this knife.' Similarly, when we say, 'Air
corrodes,' we assert or predicate the power of corroding of
* " Outlines of Psychology," p. 392.

330 Animal Life and Intelligence.

the subject ' air.' " The proposition always involves con-
ceptual elements; for the predicate of a proposition is
always an abstract idea or general notion.

Propositions so formed may then become links in a
chain of reasoning. " To reason is," says Mr. Sully,* "to
pass from a certain judgment or certain judgments to a
new one." And so passing on from judgment to judgment,
we may ascend to the higher levels of abstract thought.
According to Mr. Sully's definition, therefore, we start from
a judgment or judgments in the process of reasoning.
The formation of a judgment (conceptual inference) is,
however, the first step in a continuous process ; and I pro-
pose, under this term, "reason," f to include this first step
also. The formation of a conceptual inference I regard as
the first stage of reason. Any mental process involving
conceptual inference I shall call rational.

In contradistinction to this, I shall use the term " in-
telligence " for the processes by which perceptual inferences
are reached. An intelligent act is an act performed as the
outcome of merely perceptual inference. A rational act is
the outcome of an inference which contains a conceptual
element.

* " Outlines of Psychology." p. 414.

t Mr. Romanes adopts a different use of the terms " reason" and " rational,"
to which allusion will be made in the nest chapter.

CHAPTEE IX.

MENTAL PROCESSES IN ANIMALS : THEIR POWERS OF PERCEPTION
AND INTELLIGENCE.

Two things I have been especially anxious to bring out
prominently in the foregoing chapter : first, that the
world we see around us is a joint product of two factors
— the outward existence, on the one hand, and our active
mind on the other; and secondly, that our mental pro-
cesses and products fall under two categories — on the one
hand, perception, giving rise to percepts, perceptual
inferences, and intelligence, and on the other, conception
(involving the analysis of phenomena), giving rise to con-
cepts, conceptual inferences, and reason.

Now, I am anxious that the former — to take that first —
should be laid hold of and really grasped as an indubitable
fact. It is implied in the word " phenomena," that is to say,
appearances. We can only know the world as it appears
to us ; and the world is for us what it appears. There is
nothing here in conflict with common sense ; the practical
reality of phenomena is altered no whit. Suppose philosophy
tries to get behind phenomena, so as to get a peep at the
world beyond. Suppose Carlyle tells us that " All visible
things are emblems ; what thou seest is not there on its
own account ; strictly taken, is not there [as such] at all ;
matter exists only spiritually, and to represent some idea
and body it forth." Has he altered the reality of the
phenomena themselves ? Not in the smallest degree.
Suppose the materialist gives us his analysis of pheno-
mena. Are not the phenomena he analyzes still the same,
still equally real ? No matter how far he analyzes pheno-

Animal Life and Intelligence.

mena, behind phenomena he cannot get. The materialist
resolves all phenomena into matter in motion or into
energy, and says that these are the only real existences.
But they are no more real (they are a good deal less real
to most of us) than the phenomena with which he started.
How can the results of analysis be more real than that
which is analyzed ? Moreover, the matter and energy are
still phenomena, and involve, as such, the percipient mind.
Do what you will, you cannot get rid of the mental factor
in phenomena.

It is possible that my use of the word " construct," my
saying that the object is a thing which each of us constructs
at the suggestion of certain sense-stimuli, may lead some
to suppose that the process is in some sense an arbitrary
one. This, however, would be a misconception. The
process under normal conditions is just as inevitable as is,
under ^normal conditions, the fall of a stone to the ground.
The law of construction for human-folk is as much a law
of nature as the law of gravitation. Both laws are con-
densed statements of the facts of the case. There is
nothing arbitrary, lawless, or unnatural in the one or the
other ; tho phrase merely emphasizes the essential presence
of the mental factor.

If this principle be once thoroughly grasped, it will be
seen how shallow and misleading is the view that the
world is just reflected in consciousness unchanged as in a
mirror, or faithfully photographed as on a sensitive plate.
This is to reduce the human mind, which is surely no whit
less complex than the human body, to the condition of a
mere passive recipient instead of a vital and active agent
in the construction of man's world.

The next point we have to consider is why we believe,
as you and I practically do believe, that the world of
phenomena exists as such, not merely for you and for me,
but for man. Is it not because we believe in the practical
unity of mankind ? Is it not because we believe that,
greatly as the conceptual and intellectual superstructure
may differ in different individuals, the perceptual basis

Mental Processes in Animals. 333

and foundation are practically identical ? The senses and
sense-organs give, in all normal individuals, sense-data,
which differ only within comparatively narrow limits ; and
though the intellectual and moral world of the Bushman
and the North Australian may differ profoundly from those
of Shakespeare and Pascal, the perceptual world is, we
have every reason to suppose, within these narrow limits,
the same. This we may fairly believe ; but even so there
must be, nay, we know that there are, very great differences
in the interpretation of the perceptual world. The indi-
vidual cannot divest himself of the intellectual and con-
ceptual part of his nature. We, for whom phenomena are
more or less conditioned by science, find it difficult to
think ourselves into the position of the savage, whose
perceptual world is conditioned by crude superstition.
The elements of his perceptual world are the same as
ours, but the light of knowledge in which we view them is,
for him, very dim. When we try to realize his world we
find it exceedingly difficult.

And when we come to the lower animals — even those
nearest us in the scale of life — the difficulties are
enormously increased. The sense-data are probably much
the same, but they are combined in different proportions.
Olfactory sensation must, one would suppose, be built into
the constructs of the dog and the deer to an extent which
we cannot at all realize. And then, as Mr. P. G. Hamerton
has well said, we have to take into account the immensity
of the ignorance of animals. That ignorance, in combina-
tion with perfect perceptual clearness (ignorance and
mental clearness are quite compatible) and with incon-
ceivably strong instincts, produces a creature whose mental
states we can never accurately understand.

I am tempted here to give the instance Mr. Hamerton
quotes * in illustration of the ignorance of animals.

" The following account of the behaviour of a cow," he
says, " gives a glimpse of the real nature of the animal.
These long-tailed cows, say Messrs. Hue and Gabet, are so

* " Chapters on Animals," p. 9.

334 Animal Life and Intelligence.

restive and difficult to milk, that to keep them at all quiet
the herdsman has to give them a calf to lick meanwhile.
But for this device, not a single drop of milk can be obtained
from them. One day a Llama herdsman, who lived in the
same house as ourselves, came with a long dismal face to
announce that his cow had calved during the night, and
that, unfortunately, the calf was dying. It died in the
course of the day. The Llama forthwith skinned the poor
beast and stuffed it with hay. This proceeding surprised
us at first, for the Llama had by no means the air of a man
likely to give himself the luxury of a cabinet of natural
history. When the operation was completed, we found
that the hay-calf had neither feet nor head ; whereupon it
occurred to us that, after all, it was perhaps a pillow that
the Llama contemplated. We were in error, but the error
was not dissipated till the next morning, when our herds-
man went to milk his cow. Seeing him issue forth, the
pail in one hand and the hay-calf under the other arm, the
fancy occurred to us to follow him. His first proceeding
was to put the hay-calf down before the cow. He then
turned to milk the cow herself. The mamma at first
opened enormous eyes at her beloved infant ; by degrees
she stooped her head towards it, then smelt at it, sneezed
three or four times, and at last proceeded to lick it with
the most delightful tenderness. This spectacle grated
against our sensibilities ; it seemed to us that he who first
invented this parody upon one of the most touching
incidents in nature must have been a man without a heart.
A somewhat burlesque circumstance occurred one day to
modify the indignation with which this treachery inspired
us. By dint of caressing and licking her little calf, the
tender parent one fine morning unripped it. The hay
issued from within, and the cow, manifesting not the
slightest surprise nor agitation, proceeded tranquilly to
devour the unexpected provender."

Are we surprised at the want of surprise on the part
of the cow ? Why should we be ? What knows she of
anatomy or of physiology ? If she could think at all about

Mental Processes in Animals. 335

the matter, she would, no doubt, have expected her calf to
be composed of condensed milk. But failing that, why
not hay ? She had presumably some little experience of
putting hay inside. Why noifind hay inside ; and, finding
hay, why not enjoy the good provender thus provided ?
But clearly we must not expect the brutes to possess know-
ledge to which they cannot attain about matters which in
no wise concern their daily life.

"In our estimates of the characters of animals," con-
tinues Mr. Hamerton, in his comments on this anecdote,
" we always commit one of two mistakes — either we con-
clude that the beasts have great knowledge because they
are so clever, or else we fancy that they must be stupid
because they are so ignorant." " The main difficulty in
conceiving the mental states of animals," says the same
observer, " is that the moment we think of them as human,
we are lost." Yes, but the pity of it is that we cannot
think of them in any other terms than those of human
consciousness. The only world of constructs that we
know is the world constructed by man.

" To Newton and to Newton's dog, Diamond," said
Carlyle, " what a different pair of universes ! while the
painting in the optical retina of both was most likely the
same." Different, indeed; if we can be permitted, without
extravagance, to speak of the universe as existing at all for
Diamond, or allowed, except in hyperbole, to set side by
side a conception of ultimate generality, like the universe,
the summation of all conceptions, and " the painting in
the optical retina." Carlyle's meaning is, however, clear
enough. Given two different minds and the same facts,
how different are the products ! In the construct formed
on sight of the simplest object, we give far more than we
receive ; and what we give is a special resultant of
inheritance and individual acquisition. No two of us give
quite the same in amount or in quality. It is not too
much to say that for no two human beings is the world we
live in quite the same. And if this be so of human-folk,
how different must be the world of man from the world

336 Animal Life and Intelligence.

of the dog — the world of Newton from the world of
Diamond !

And we must remember that it is not merely that the
same world is differently mirrored in different minds, but
that they are two different worlds. If there is any truth
in what I have urged in the last chapter, we construct the
world that we see. The sensations are, as we have seen,
mental facts, in no sense resembling their causes, but
representing them in mental symbolism. Percepts are the
elaborated products of this mental symbolism. The
question, then, is not — How does the world mirror itself in
the mind of the dog ? but rather — How far does the symbolic
world of the dog resemble the symbolic world of man ?
How far is his symbolism the same as ours ? Only \>y
fully grasping the fact that the external world of objects
does not exist independently of us (though something
exists which we thus symbolize), shall we realize the great-
ness of the difficulty which stands in the path of the student
of animal psychology. So long as we are content to accept
John Bunyan's crude analogy of the gateways of sense, the
difficulty is comparatively small. There is the outside
world self-existent and independent ; a knowledge of it
comes into the mind through the five gateways of sense —
a picture of it through the eye-gate, and so on. The dog
has also five similar gateways. The world for him is,
therefore, much the same as for us. But this is not a true
analogy. The world we see around us is a joint product
of an external existence, the independent nature of which
we can never know, and the human mind. It is something
we construct in mental symbolism. How far does the dog
construct a similar world? The answer to this question
must, as it seems to me, be largely speculative.

And what help have we towards answering it ? That
afforded by the theory of organic evolution. If we accept
that theory, and accept also the view that mental or
psychical products are the inseparable concomitants of
certain organic or physiological processes, then we have a
basis from which to start. That basis I adopt.

Mental Processes in Animals. 337

Unfortunately, we have at present but little particular
knowledge of the correlation of psychical and physiological
processes. We cannot, by the dissection of a brain, draw
much in the way of valid and detailed inference as to the
nature of the psychical processes which accompany its
physiological action. Fortunately, however, on the other
hand, there are certain physical manifestations which do
aid us, and that not a little, in drawing inferences from
the physical to the mental. For organisms exhibit certain
activities, and from these activities we can infer to some
extent the character of the mental processes by which they
are prompted. We are wont, in observing the actions of
our fellow-men, to draw conclusions (often, alas ! erroneous)
as to the mental processes which accompany them. We
are ourselves active, and we are immediately conscious of
the modes of consciousness which accompany our actions.
Thus the activities of organisms give us some clue to their
mental processes, and it is through observation of their
physical activities that we gain nearly all that is of par-
ticular value concerning the mental activities of animals.
These activities we shall have to consider more fully in a
future chapter. In the present chapter we shall consider
them only so far as they give us information concerning
the perceptual world (or worlds) of animals, and the nature
of the inferences which we may suppose animals to draw
from the phenomena which fall within their observation.

I think that, from the fundamental identity of life-stuff,
or protoplasm, in all forms of animal life, and from the
observed similarity of nerves and nerve-cells when nervous
tissue has been developed, and again from the essential
resemblance of life-processes in all animal organisms, we
are justified in believing that mental or conscious pro-
cesses, when they emerge, are essentially similar in kind.
Exactly when they do emerge in the ascending branches
of the great tree of animal life it is exceedingly difficult,
if not quite impossible, to determine. And it is, I fancy,
quite impossible for us so to divest ourselves of the com-
plexity of human consciousness as to imagine what the

z

338 Animal Life and Intelligence.

simplicity of the emergent consciousness in very lowly
organisms is like. But I think that we may fairly believe
that some dim form of discrimination is the germ from
which the spreading tree of mind shall develop.*

I assume, then, that, granting the theory of evolution,
the early stages of the process of construction — discrimina-
tion, localization, and outward projection — are the same
in kind throughout the whole range of animal life, wherever
we are justified in surmising that psychical processes occur,
and the power of registration and revival in memory has
been established. As will be gathered, however, from what
I have already said, I hold that the nature of the con-
structs produced is and must be for us human-folk, since
we are human-folk, to a large extent a matter of specula-
tion. Remembering this, then, endeavouring never to lose
sight of it for a moment, let us consider what we may
fairly surmise concerning the constructs and the process
of construction in animals.

There can be no question that the animals nearest us
in the scale of life — the higher mammalia — form constructs
analogous to, if not closely resembling, ours. I do not
think the resemblance can be in any sense close, seeing to
how large an extent our constructs are literally our handi-
work. For though in many animals the tongue and lips
are delicate organs of touch — not to mention the trunk of
the elephant — and though in the monkeys and many
rodents the hands are used for grasping, still we have no
reason to suppose that in any other mammal the geome-
trical sense of touch plays so determining a part in the
formation of constructs as in man. On the other hand,
in the dog and the deer, for example, not only must the
marvellously acute sense of smell have a far higher sug-

* Or perhaps we may say, in the language of analogy, that when the
germinal psychoplasm of some dim form of organic memory is fertilized by
the union therewith of the more active male element of discrimination, a
process of segmentation of the psychoplasm sets in by which, in process of
differentiation, the tissues and organa of the mind are eventually developed.

Mental Processes in Animals. 339

gestive value, but smells and odours must, one would
suppose, be built into the constructs in a far larger pro-
portion. But although their constructs may not closely
resemble ours, the constructs of animals may, I believe,
be fairly regarded as closely analogous to our own. And
as with us, so with them, a comparatively simple and
meagre suggestion may give rise, through association in
experience, to the construction of a complex object. And
again, as with us, so with them, the suggested construct
may be very vague and indefinite.

A dog, for example, is lying asleep upon the mat, and
hears an unfamiliar step in the porch without. There can
be no question that this suggests the construct man. But
from the very nature of the case, this must be vague and
indefinite. So, too, when a chamois, bounding across the
snow-fields, stops suddenly when he scents the distant foot-
prints of the mountaineer, the construct that he forms
cannot be in any way particularized — no more par-
ticularized than is to me the sheep that I hear bleating
in the meadow behind yonder wall.

And no one is likely to question the fact that animals
habitually proceed from this first stage — the formation of
constructs by immediate association — to the second stage
of construction — the defining of constructs by examination.
In many of the deer tribe, notably the prong-horn of
America, this tendency is so strongly developed that they
may be lured to their destruction by setting up a strange
and unfamiliar object which, as we put it, may excite their
curiosity. A strange noise or appearance will make a dog
uneasy until he has by examination satisfied himself of
the nature of that which produces it. Of this an instance
fell under my observation a few days ago. My cat was
asleep on a chair, and my little son was blowing a toy
horn. The cat, without moving, mewed uneasily. I told
my boy to continue blowing. The cat grew more uneasy,
and at last got up, stretched herself, and turned towards
the source of discomfort. She stood looking at my boy for
a minute as he blew. Then curling herself up, she went

34-O Animal Life and Intelligence.

to sleep again, and no amount of blowing disturbed her
further. Similarly, Mr. Romanes's dog was cowed at the
sound of apples being shot on to the floor of a loft above
the stable ; but when he was taken to the place, and saw
what gave rise to the sound, he ceased to be disquieted by
it. Every one must have seen animals defining their
constructs by examination. A monkey will spend hours
in the examination of an old bottle or a bit of looking-
glass. At the Zoological Gardens connected with the
National Museum at Washington, a monkey was observed
with a female opossum on his knee. He had discovered
the slit-like opening of the marsupial pouch, and took out
first one and then another of the young, looked them over
carefully, and replaced them without injury.*

There may possibly be some difference of opinion as to
whether animals are able to infuse into their constructs
of other animals the element of feeling. One would, per-
haps, fain believe that the beasts of prey were wholly
unaware of the pain they inflict on other organisms. But
I question whether any close observer of animals could
hold this view. Even if it were supposed that when two
dogs fight they are blind to the pain they are inflicting on
each other, their mock-fighting seems to imply a con-
sciousness of the pain they might inflict, but avoid inflict-
ing. And many of us have presumably had experiences
analogous to the following: A favourite terrier of mine
was once brought home to me so severely gashed in the
abdominal region that I felt it necessary to sew up the
wound. In his pain the poor dog turned round and seized
my hand, but he checked himself before the teeth had
closed upon me tightly, and piteously licked my hand.
For myself, I cannot doubt that animals project into each
other the shadows of the feelings of which they are them-
selves conscious.

The fact that dogs may be deceived by pictures f shows
that they may be led through the sense of sight to form

* Nature, vol. xxxviii. p. 257.

t For examples, see Romanes's " Animal Intelligence," p. 455.

Mental Processes in Animals. 341

false constructs, that is to say, constructs which examina-
tion shows to be false. Through my friend and colleague,
Mr. A. P. Chattock, I am able to give a case in point. I
quote from a letter received by Mr. Chattock: "Your
father asks me to tell you about our old spaniel Dash and
the picture. I remember it well, though it must be some-
where about half a century ago. We had just unpacked
and placed on the old square pianoforte, which then stood
at the end of the dining-room, the well-known print of
Landseer's 'A Distinguished Member of the Humane
Society.' When Dash came into the room and caught
sight of it, he rushed forward, and jumped on the chair
which stood near, and then on the pianoforte in a moment,
and then turned away with an expression, as it seemed to
us, of supreme disgust."

I think we may say, then, that the higher animals are
able to proceed a long way in the formation and definition
of highly complex constructs analogous to, but probably
differing somewhat from, those which we form ourselves.
These constructs, moreover, through association with re-
constructs or representations, link themselves in trains, so
that a sensation or group of sensations may suggest a
series of reconstructs or a series of remembered phenomena.
We here approach the question of inferences, of which
more anon. But in this connection passing reference may
be made to the phenomena of dreaming. Dogs and some
other animals undoubtedly seem to dream.

The nature of dreaming may, perhaps, be best illustrated
by a rough analogy. Professor Clifford likened the human
consciousness to a rope made up of a great number of
occasionally interlacing strands. Let us picture such a
rope floating in water. Much of it is submerged; only
the upper part is visible at the surface. This upper part
is like the series of mental phenomena of which we are
distinctly conscious. Below this lie other series in the
half-submerged state of subconsciousness. Deeper still lie
unconscious physiological processes capable of emerging
into the shadow of subconsciousness or the light of distinct

342 Animal Life and Intelligence.

consciousness. Now picture this rope gradually slipping
round as it floats, so that now one part, now another, sees
the light. This is analogous to the musing state, when
we allow our thoughts to wander unchecked by any effort
of attention. Attention is the faculty by which we steady
the rope, so that one particular strand is kept continuously
uppermost. The inattentive mind is one in which the rope
keeps slipping round and refuses to be steadied in this
manner ; and in unquiet sleep, when the faculty of attention
is dormant, the strands come quite irregularly and hap-
hazard to the surface, and we have the phantasmagoria of
dreams.

In the dog or the ape the rope is presumably in-
comparably simpler. But that it is of the nature of a rope
we may, perhaps, not improbably surmise. Interest and
the attention it commands steady the rope. Animals
differ widely in their power of attention, as every one
knows who has endeavoured to educate his pets. Darwin
tells us that those who buy monkeys from the Zoological
Gardens, to teach them to perform, will give a higher price
if they are allowed a short time in which to select those in
which the power of attention is most developed. And
when animals dream, their consciousness-rope is slipping
round unsteadily. That they do apparently dream is,
so far, evidence of their possessing linked chains of
memories.

In speaking of the faculty of attention in animals, it
may be well to note that attention is of two kinds — per-
ceptual or direct, and conceptual or indirect. In perceptual
attention its motive is directly suggested by the object
which stimulates this concentration of the faculties; a
menacing dog, for example, stimulates my perceptual
attention. In conceptual attention the motive is ulterior
and indirect. The concentrated attention which a man
devotes to the acquisition of Sanscrit does not arise directly
out of the symbols over which he pores ; it is of intellectual
origin.

In the normal life of animals the attention is of the

Mental Processes in Animals. 343

perceptual order ; it is a direct stimulation of the faculties
through a perceptual presentation of sense or representa-
tion in memory which gives rise to an appetence or aver-
sion. The importance of such a faculty is obvious. As
M. Eibot well says, it is no less than a condition of life.
The carnivorous animal that had not its attention roused
on sight of prey would stand but a poor chance of survival ;
the prey that had not its attention roused by the approach
of its natural enemy would stand but a poor chance of
escape. The emperor moth that had not its attention
roused by the scent of the virgin female would stand but a
poor chance of propagating its species.

We are not, however, at present in a position further to
discuss this matter. For there is a factor in the process
which we shall have to consider more fully hereafter — the
emotional factor. The hungry lion is in a very different
position, so far as attention is concerned, from the satiated
animal. The force and volume of the attention depends
not merely, or even mainly, upon the intensity of the
stimulus, but on the emotional state of the recipient
organism.

Endeavour to divert the attention of any animal which
is intent upon some action connected with the main busi-
ness of its life — nutrition, self-defence, or the propaga-
tion of the species — the force of attention will at once be
obvious.

In the training of animals (and young children) artificial
associations, pleasurable or painful, have to be established
in connection with certain actions. Abnormal appetences
and aversions have to be introduced into the mental con-
stitution. In this process much depends on the plasticity
of the constitution. In the absence of such plasticity it is
impossible to establish new associations.

We have seen that words are arbitrary * symbols, which
we associate with objects, or qualities, or actions. Can
animals, we may ask, form such arbitrary associations ?

* I use the word " arbitrary " in the sense that they form no part of the
normal construct such as would be formed by the animal.

344 Animal Life and Intelligence.

There can be little question that they can. Many of the
higher animals understand perfectly some of our words.
The word "cat" or "rats" will suggest a construct to
the dog on which he may take very vigorous action. How
far they are able to communicate with each other is a
somewhat doubtful matter. But the signs by which such
communication is effected are probably far less arbitrary.
And, in any case, the communication would seem to
refer only to the here and the now. A dog may be
able to suggest to his companion the fact that he has
descried a worriable cat ; but can a dog tell his neigh-
bour of the delightful worry he enjoyed the day before
yesterday ?

I imagine that what a dog can suggest to his neigh-
bour is what we symbolize by the simple expression
" Come." But I am fully aware that other observers will
interpret the facts in a different way. Here is an anecdote
that is communicated to me by Mr. Eobert Hall Warren,
of Bristol. " My grandfather," he says, " a merchant of
this city, or, as Thomas Poole, of Stowey, would have
preferred calling him, ' a tradesman,' had two dogs, one a
small one and another larger, who, being fierce, rejoiced
in the appropriate name of Boxer. On one of his business
journeys into Cornwall he took the smaller dog with him,
and for some reason left it at an inn in Devonshire,
promising to call for him on his return from Cornwall.
When he did so, the landlord apologized for the absence of
the dog, and said that, some time after my grandfather
left, the little dog fought with the landlord's dog, and
came off much the worse for the fight. He then dis-
appeared, and some time afterwards returned with another
and larger dog, who set upon his enemy, and, I think,
killed him. Then the two dogs walked off, and were no
more seen. From the description given, my grandfather
had no doubt that the larger dog was Boxer, and, on
returning home, found that the little dog had come back,
and that both dogs had gone away, and, after a time, had
returned home, where he found them." Now, some will

Mental Processes in Animals. 345

say that the little dog told Boxer all about it ; but I am
inclined to believe that the facts may be explained by the
communication " Come."

Dogs can also communicate their wishes to us. The
action of begging in dogs is a mode of communication with
us. Mr. Eomanes tells of a dog that was found opposite a
rabbit-hutch begging for rabbits. When I was at the
Diocesan College near Capetown, a retriever, Scamp,
used to come in and sit with the lecturers at supper. He
despised bread, but used to get an occasional bone, which
he was not, however, allowed to eat in the hall. He took
it to the door, and stood there till it was opened for him.
On one occasion he heard without the excited barking of
the other dogs. He trotted round the hall, picked up a
piece of bread which one of the boys had dropped, and
stood with it in his mouth at the door. When it was
opened, he dropped the bread, and raced off into the
darkness to join in the fun. In a similar way, but with
less marked intelligence, I have seen a dog begging before
a door which he wished opened. My cat has been taught
to touch the handle of the door with his paw when he
wishes to leave the room. Mr. Arthur Lee, of Bristol,
tells me that a favourite cat has a habit of knocking for
admittance by raising the door-mat and letting it fall.
This is an action similar to those communicated by several
observers to Nature, where cats have learnt either to knock
for admittance or to ring the bell — an action which, as my
friend, Mr. J. Clifton Ward, informed me, was also per-
formed by a dog of his. I think, therefore, that it is
unquestionable that the higher animals are able to associate
arbitrary signs with certain objects and actions, and to
build these signs into the constructs that they form. Sir
John Lubbock has tried some experiments with his in-
telligent black poodle Van, with the object of ascertaining
how far the dog could be taught to communicate his wishes
by means of printed cards. "I took," he says,* "two
pieces of cardboard, about ten inches by three, and on one
* «< The Senses of Animals," p. 277.

346 Animal Life and Intelligence.

of them printed in large letters the word ' FOOD,' leaving
the other blank. I then placed the two cards over two
saucers, and in the one under the ' Food ' card put a little
bread-and-milk, which Van, after having his attention
called to the card, was allowed to eat. This was repeated
over and over again till he had had enough. In about ten
days he began to distinguish between the two cards. I
then put them on the floor, and made him bring them to
me, which he did readily enough. When he brought the
plain card, I simply threw it back ; while, when he brought
the ' Food ' card, I gave him a piece of bread, and in about
a month he had pretty well learned to realize the difference.
I then had some other cards printed with the words * Out/
' Tea,' ' Bone,' ' Water,' and a certain number also with
words to which I did not intend him to attach any sig-
nificance, such as ' Nought,' ' Plain,' ' Ball,' etc. Van soon
learned that bringing a card was a request, and soon
learned to distinguish between the plain and printed cards ;
it took him longer to realize the difference between words,
but he gradually got to recognize several, such as ' Food,'
'Out,' 'Bone,' 'Tea,' etc. If he was asked whether he
would like to go out for a walk, he would joyfully fish
up the ' Out ' card, choosing it from several others, and
bring it to me or run with it in evident triumph to the
door.

"A definite numerical statement always seems to me
clearer and more satisfactory than a mere general assertion.
I will, therefore, give the actual particulars of certain days.
Twelve cards were put on the floor, one marked ' Food '
and one ' Tea.' The others had more or less similar
words. I may again add that every time a card was
brought, another similarly marked was put in its place.
Van was not pressed to bring cards, but simply left to do
as he pleased.*

* As I understand the observations here tabulated, the twelve cards lay
always within Van's reach and sight. An ordinary untrained dog would have
taken no notice of them. But Van, when he wanted food or tea, went and
fetched the appropriate card, and got what he wanted in exchange. In twelve
days he only made two mistakes, bringing " Nought " once and " Door " once.

Mental Processes in Animals. 347

Day 1. Van brought • Food ' 4 times, ' Tea' 2 times.
» 2- », » 6 „

» 3. „ „ 8 „

,,4. 7 ,

5. „ „ 6

6. „ „ 6

7. „ „ 8

5
4

10.

11.
12.

4 „

3 „ ' Nought * once.

10 „ „ 4 „ ' Door ' once.
10 „ „ 3 „
6 , , 3 ,

31

" Thus, out of 113 times, he brought 'Food' 80 times,
1 Tea ' 31 times, and [one out of] the other 10 cards only
twice. Moreover, the last time he was wrong he brought
a card — namely, ' Door ' — in which three letters out of four
were the same as in ' Food.' "

These experiments and observations are of great
interest. But, of course, no stress whatever must be laid
on the fact that words chanced to be printed on the cards
instead of any other arrangements of lines. I draw
attention to this because I have heard Sir John Lubbock's
interesting experiments quoted, in conversation, as evidence
that the dog understands the meaning of words, not only
spoken, but written ! What they show is that Van is able,
under human guidance, to associate certain arbitrary
symbols with certain objects of appetence ; and, desiring
the object, will bring its symbol. It would have been
better, I think, because less misleading to the general
public, had Sir John Lubbock selected other arbitrary
symbols than the printed words we employ. Then no one
could have run away with the foolish notion that the dog
understands the meaning of these words. No doubt if they
had been written in Greek or Hebrew, some people would
have been interested, but not surprised, to learn that a
dog can be taught to understand with perfect ease these

The next question is — Have the higher animals the
power of analyzing their constructs and forming isolates or

348 Animal Life and Intelligence.

abstract ideas of qualities apart from the constructs of
•which these qualities are elements ? Can we say, with
Mr. Romanes,* "All the higher animals have general
ideas of ' good-for-eating ' and ' not-good-for-eating,' quite
apart from any particular objects of which either of these
qualities happens to be characteristic " ? Or with Leroy,t
that a fox "will see snares when there are none; his
imagination, distorted by fear, will produce deceptive
shapes, to which he will attach an abstract notion of
danger " ?

Now, this is a most difficult question to answer. But
it seems to me that, if we take the term " abstract idea " in
the sense in which I have used the word " isolate," we
must answer it firmly, but not dogmatically (this is the
last subject in the world on which to dogmatize), in the
negative. Fully admitting, nay, contending, that this is a
matter in which it is exceedingly difficult to obtain anything
like satisfactory evidence, I fail to see that we have any
grounds for the assertion that the higher animals have
abstract ideas of "good-for-eating" or "not-good-for-
eating," quite apart from any particular objects of which
either of these qualities happens to be characteristic. J

The particular example is well chosen, since the idea of
food is a dominant one in the mind of the brute. There
can be no question that the quality of eatability is built in
by the dog into a great number of his constructs. But I
question whether this quality can be isolated by the dog,
and can exist in his mind divorced from the eatables which
suggest it. If it can, then the dog is capable of forming a
concept as I have defined the term. I can quite understand

* " Mental Evolution in Man," p. 27.

t "Intelligence of Animals," p. 121.

J Mr. Romanes also says ("Mental Evolution in Animals," p. 235),
" This abstract idea of ownership is well developed in many if not in most
dogs." By an abstract idea of ownership I understand a conception of owner-
ship which, to modify Mr. Romanes's phrase, is quite apart from any objects
or persons of which such ownership happens to be characteristic. Even if we
believe that a dog can regard tliis or that man as his owner, or this or that
object as his master's property, still even this seems to me a very different
thing from his possessing an abstract idea of ownership.

Mental Processes in Animals. 349

that a hungry dog, prowling around for food, has, sug-
gested by his hunger, vague representations in memory
of things good to eat, in which the element of eatability is
predominant and comparatively distinct, while the rest is
vague and indistinct. And that this is a concept in Mr.
Sully's use of the term, I admit. But it appears to me
that there is a very great difference between a perceptual
construct with eatability predominant and the rest vague,
and a conceptual isolate or abstract idea of eatability quite
apart from any object or objects of which this quality is
characteristic. And to mark the difference, I venture to
call the prominent quality a predominant as opposed to
the isolate when the quality is floated off from the object.
No doubt it is out of this perceptual prominence of one
characteristic and vagueness of its accompaniments that con-
ceptual isolation of this one characteristic has grown, as I
believe, through the naming of predominants. But I should
draw the line between the one and the other somewhere
distinctly above the level of intelligence that is attained by
any dumb animal. I am not prepared either to affirm or
deny that this line should be drawn exactly between brute
intelligence and human intelligence and reason, though I
strongly incline to the view that it should. I am not sure
that every savage and yokel is capable of isolation, that he
raises the predominant to the level of the isolate, or abstract
idea. I am not sure that these simple folk submit the
phenomena of nature around them, and of their own
mental states to analysis. But they have in language the
instrument which can enable them to do so, even if
individually some of them have not the faculty for using
language for this purpose. That is, however, a different
question. But I do not at present see satisfactory evidence
of the fact that animals form isolates, and I think that the
probability is that they are unable to do so. I am, there-
fore, prepared to say, with John Locke, that this abstraction
"is an excellency which the faculties of brutes do by no
means attain to."

I am anxious, however, not to exaggerate my divergence,

350 Animal Life and Intelligence.

more apparent, I believe, than real, from so able a student
of animal psychology as Mr. Eomanes. Let me, therefore,
repeat that it is the power of analysis — the power of
isolating qualities of objects, the power of forming " abstract
ideas quite apart from the particular objects of which the
particular qualities happen to be characteristic," as I
understand these words — that I am unable to attribute to
the brute. Animals can and do, I think, form pre-
dominants ; they have not the power of isolation.

Furthermore, it seems to me that this capacity of
analysis, isolation, and abstraction constitutes in the
possessor a new mental departure, which we may describe
as constituting, not merely a specific, but a generic differ-
ence from lower mental activities. I am not prepared,
however, to say that there is a difference in kind between
the mind of man and the mind of the dog. This would imply
a difference in origin or a difference in the essential nature
of its being. There is a great and marked difference in kind
between the material processes which we call physiological
and the mental processes we call psychical. They belong
to wholly different orders of being. I see no reason for
believing that mental processes in man differ thus in kind
from mental proceses in animals. But I do think that we
have, in the introduction of the analytic faculty, so definite
and marked a new departure that we should emphasize it
by saying that the faculty of perception, in its various
specific grades, differs generically from the faculty of con-
ception. And believing, as I do, that conception is beyond
the power of my favourite and clever dog, I am forced to
believe that his mind differs generically from my own.

Passing now to the other vertebrates, the probabilities
are that their perceptual processes are essentially similar
to those of the higher animals ; but, in so far as these
creatures differ more and more widely from ourselves, we
may, perhaps, fairly infer that their constructs are more
and more different from ours. Still, the thrush that listens
attentively on the lawn and hops around a particular spot

Mental Processes in Animals. 351

must have a vague construct of the worm he hopes to have
a more particular acquaintance with ere long. The cobra
that I watched on the basal slopes of Table Mountain, and
that raised his head and expanded his hood when I pitched
a pebble on to the granite slope over which he was gliding,
must have had a vague percept suggested thereby. The
trout that leaps at your fly so soon as it touches the water
must have a vague percept of an eatable insect which
suggests his action. The carp * that come to the sound of
a bell must have, suggested by that sound, vague percepts
of edible crumbs. And no one who has watched as a lad
the fish swimming curiously round his bait can doubt that
they are by examination defining their percepts, and drawing
unsatisfactory inferences of a perceptual nature.

And here let us notice that the whole set of phenomena
which have been described in previous chapters under the
heads of recognition-marks, of warning coloration, and of
mimicry, involve close and accurate powers of perception.
Eecognition-marks are developed for the special purpose
of enabling the organisms concerned rapidly and accurately
to form particular perceptual constructs. Of what use
would warning coloration be if it did not serve to suggest
to the percipient the disagreeable qualities with which it
is associated ? The very essence of the principle of mimicry
is that misleading associations are suggested. Here a
false construct, untrue to fact, that is to say, one that
verification would prove to be false, is formed ; just as a
well-executed imitation orange, in china or in soap, may
lead a child to form a false construct, one that is proved
to be incorrect so soon as the suggestions of sight are
submitted ta verification by touch, smell, and taste.

No one who has carefully watched the habits of birds
can have failed to notice how they submit a doubtful object
to examination. Probably the avoidance of insects pro-
tected by warning colours is not perfectly instinctive. I

* Doubt has recently been thrown on this fact. Mr. Bateson has shown
that some fishes do not hear well, and has suggested that the carp may be
attracted by seeing people come to the edge of the pond.

352 Animal Life and Intelligence.

have seen young birds, after some apparent hesitation,
peck once or twice doubtfully at such insects. A young
baboon with whom I experimented at the Cape seemed to
have an undefined aversion to certain caterpillars, which
he could not be induced to taste, though he smelt at them.
Scorpions he darted at, twisted off the sting, and ate with
greedy relish.

If nudibranchs and other marine invertebrates be pro-
tectively coloured, there must be corresponding perceptual
powers in the fishes that are thus led to avoid them ; for
there seems to be definite avoidance, and not merely in-
difference. This, however, might be made the subject of
further experiment, not only with fishes, but with other
animals. I tried some chickens with currant-moth cater-
pillars, to each of which I tied with thread a large looper.
Some of them would have nothing to do with the unwonted
combination. But one persistently pecked at the looper,
and tried to detach it from its fellow-prisoner. Though,
on the whole, there was some tendency for aversion to the
currant-moth caterpillar to overmaster the appetence for
the looper, I was not altogether satisfied with the result
of the experiment. But I think that if the protectively
coloured larva had been regarded with mere indifference
(i.e. neither aversion nor appetence), the appetence for
the loopers should have made the chickens seize them at
once.

To return to fishes. It is probably difficult or impos-
sible for us to imagine what their constructs are like ; but
that they, too, proceed to define them by examination
seems to be a legitimate inference from some of their
actions. Mr. Bateson says, " The rockling searches [for
food] by setting its filamentous pelvic fins at right angles
to the body, and then swimming about, feeling with them.
If the fins touch a piece of fish or other soft body, the
rockling turns its head round and snaps it up with great
quickness. It will even turn round and examine uneatable
substances, as glass, etc., which come in contact with its
fins, and which presumably seem to it to require explana-

Mental Processes in Animals. 353

tion." * And, speaking of the sole, the same observer
says,f " In searching for food the sole creeps about on
the bottom by means of the fringe of fin-rays with which
its body is edged, and, thus slowly moving, it raises its
head upwards and sideways, and gently pats the ground
at intervals, feeling the objects in its path with the peculiar
viliform papillae which cover the lower (left) side of its head
and face. In this way it will examine the whole surface
of the floor of the tank, stopping and going back to in-
vestigate pieces of stick, string, or other objects which it
feels below its cheek."

If we admit the fact that carp come to be fed at the
sound of a bell, we have evidence that some fishes can
associate an arbitrary sound with the advent of things
good to eat. But it is, perhaps, better at present to regard
the fact as one requiring verification.

That some birds can associate arbitrary signs with their
percepts will be admitted by all who have watched their
habits. And from its peculiar and almost unique power
of articulation, the parrot shows us that not only may the
words suggest a construct, but that the sight of the con-
struct may suggest the word that it has heard associated
with the object by man. Mr. Romanes gives evidence
which satisfies him that a parrot which had associated the
word " bow-wow " with a particular dog, uttered this sound
when another dog entered the room. The word was here
suggested at sight, not of the same object, but of an object
which the bird recognized as similar. A somewhat similar
case is furnished by one of my own correspondents (Miss
Mabel Westlake). " We left London," she says, " in
December, 1888, and brought our grey parrot with us ; but
left behind with a friend our favourite cat, a dark tortoise-
shell with a white breast, the forehead clearly marked with
a division down the middle to the tip of the nose. This
led to our calling her 'Demi.' For a week or two after

* Journal of Marine Biological Association, New Series, vol. i. No. 2,
p. 214. I should not myself have used the word " explanation."
t Ibid. vol. i. No. 3, p. 240.

2A

354 Animal Life and Intelligence.

our arrival in Bristol, a black-and-white cat belonging to
the people formerly living here frequented the house. The
parrot seemed delighted to see this cat, which was larger
than our old cat, and called it Dem, as she had been
accustomed to do in London. From that time until the
commencement of January (1890), which was over a year,
the parrot had not seen a cat that we are aware of, nor
had we heard her call it for a long time. About six weeks
ago, as I was coming along Kingsdown Parade, a large
black kitten followed me home. We took it in and fed it.
The next day it came into the room where the parrot was,
and she immediately said ' Puss ! puss ! puss ! Hullo,
dear ! ' and during the day called it by the same name,
' Dem ! Dem ! Dem ! ' that she had called our cat in
London."

We may here notice that, in most of the tricks which
animals are taught to perform, the action is suggested by
a form of words (or the tone and manner in which they
are uttered). Mr. John G. Naish, J.P., of Ilfracombe,*
has taught his cockatoo the following trick (I quote Mr.
Naish's own words) : " I give him a shilling, which he puts
into the slit of a money-box. This is ' enlisting.' After
that, I say to him, ' Will you die for the queen, like a loyal
soldier ? ' Then he lies on his back, with his paws together,
for as long as I hold up my finger. ' Now live for your
master ! ' He takes hold of my finger and resumes his
erect posture. Last year I took him into the street near
my house, and collected on our ' Hospital Saturday.' He
worked for more than an hour before he became impatient.
And then he would do no more, but, flung the coins over
his head or at the giver in the funniest way. He went to
sleep for a long time after that performance ; and when he
awoke and I took him, he covered my face with kisses, as
if he was glad to find his bad dream was over." The
weariness and failure to perform the trick when tired, and
the long sleep which succeeded, are interesting points.

* I have to thank this gentleman for a most interesting account of the
intelligence of his favourite bird.

Mental Processes in Animals. 355

What I wish especially to notice is, however, that the
actions are suggested by certain forms of words ; but that
there is no evidence that the form of words is in any sense
understood. When the onlooker sees a bird lie on its back
when asked if it will die for the queen, and get up again
when told to live for its master, he is apt to think that,
since he understands the form of words, the bird must
understand them too. But I am convinced that Mr.
Naish's intelligent cockatoo could have been taught with
equal ease to lie down at the command "Abracadabra,"
and to stand up again at " Hocus pocus." Tricks taught
to animals involve the performing animal and the human
onlooker. The form of words introduced is for the sake of
the latter, not for the sake of the former.

So much has been written concerning the intelligence
of the parrot, and so much has been said concerning its
imitative power of speech, that I must say somewhat
on this head. I have received from Miss Mildred Sturge,
of Clifton, an interesting account of an African West Coast
parrot which was possessed by Miss Tregelles, of Falmouth.
This parrot used the phrases it had learnt appropriately in
time and place. " At dinner, when he saw the vegetable-
dishes, he generally said, ' Polly wants potato ; ' at tea he
would say, 'Polly wants cake,' or ' Polly's sop,' or ' Polly's
toast.' Our grandmother's house was not far from the
station, and almost before people could hear it, Polly
would announce, ' Grandmamma, the train is coming,' and
presently the train would quietly go by. Besides repeating
much poetry, Polly made new editions by putting lines
together from different authors ; but the remarkable thing
was that he always got the right rhyme. One of his
favourite mixtures was, ' Sing a song of sixpence ' and ' I
love little pussy.' One day my mother overheard —

" ' Four and twenty blackbirds,

When they die,
Go to that world above,
Baked in a pie. ' "

Now, we must not underrate nor overrate the evidence

356 Animal Life and Intelligence.

afforded by parrot-talk. The rhyme-association is interest-
ing ; but since we cannot suppose that the poetry is more
to the parrot than a linked series of sounds, there does not
seem much evidence of intelligence here, though the
evidence of memory is important. The correct association
of words and phrases with appropriate objects and actions
is of great interest. But the fact that they are words and
phrases does not give them a higher value than that of
imitative actions in the dog or other animal. What
parrot-talk does give us evidence of is (1) remarkable
powers of memory ; (2) an almost unique power of articula-
tion ; (3) a great faculty of imitation ; (4) and some in-
telligence in the association of certain linked sounds which
we call phrases with certain objects or actions. The
teaching of phrases to the parrot is certainly not more
remarkable than the teaching of clever tricks to many
birds. But the fact that word-sounds are articulated
throws a glamour over these special tricks, and leads some
people to speak of the parrot's using language, instead of
saying that the parrot can imitate some of the sounds
made by man, and can associate these sounds with certain
objects.

Coming now to the invertebrates, much has been written
concerning the psychology and intelligence of ants and
bees. What shall we say concerning their constructs ?
For reasons already given, I think we may suppose that
they are analogous to ours ; but it can scarcely be that
they in any way closely resemble ours. Their sense-organs
are constructed on a different plan from ours ; they have
probably senses of which we are wholly ignorant. Is it
conceivable, by any one who has grasped the principle of
construction, that with these differently organized senses
and these other senses than ours, the world they construct
can much resemble the world we construct ? Eemember
how largely our perceptual world is the product of our
geometrical senses — of our delicate and accurate sense of
touch, and of our binocular vision, with its delicate and

Mental Processes in Animals.

357

accurate muscular adjustments. Kemember how largely
these muscular adjustments enter into our perceptual world
as constructed in vision. And then remember, on the
other hand, that the bee is encased in a hard skin (the
chitinous exoskeleton), and that its tactile sensations are
mainly excited by means of touch-hairs seated thereon.
Remember its compound eye with mosaic vision, coarser
by far than our retinal vision, and its ocelli of proble-
matical value, and the complete absence of muscular
adjustment in either the one or the other. Can we con-
ceive that, with organs so different, anything like a similar
perceptual world can be elaborated in the insect mind ? I
for one cannot. Admitting, therefore, that their perceptions
may be fairly surmised to be analogous, that their world is
the result of construction, I do not see how we can for one
moment suppose that the perceptual world they construct
can in any accurate sense be said to resemble ours. For
all that, the processes of discrimination, localization, out-
ward projection ; the formation of vague constructs, their
definition through experience, and the association of re-
constructs or representations; — all these processes are
presumably similar in kind to those of which we have
evidence in ourselves.

In considering such organisms as ants and bees, however,
we must be careful to avoid the error of supposing that,
because they happen to have no backbones, they are neces-
sarily low in the scale of life and intelligence. The tree of
life has many branches, and, according to the theory of
evolution, these divergent branches have been growing up
side by side. There is no reason whatever why the bee and
the ant, in their branch of life, should not have attained as
high a development of structure and intelligence as the
elephant or the dog in their branch of life. I do not say
that they have. As it is difficult to compare their structure,
in complexity and efficiency, with that of vertebrates, so is
it difficult to compare their intelligence. The mere matter
of size may have necessitated the condensation of intelli-
gence into instinct in a far higher degree than was required

358 Animal Life and Intelligence.

in the big-brained mammals. Still, their intelligence,
though of a different order and on a different plane, may
well be as high. And Darwin has said that the so-called
brain of the ant may perhaps be regarded as the most
wonderful piece of matter in the world.

That ants have some power of communication seems to
be proved by the interesting experiments of Sir John
Lubbock. He found that they could carry information to
the nest of the presence of larvae, and that the greater the
number of larvae to be fetched, the greater the number of
ants brought out to fetch them in a given time. On one
occasion Sir John Lubbock put an ant to some larvae.
" She examined them carefully, and went home without
taking one. At this time no other ants were out of the
nest. In less than a minute she came out again with eight
friends, and the little group made straight for the heap of
larvae. When they had gone two-thirds of the way, I im-
prisoned the marked ant ; the others hesitated a few
minutes, and then, with curious quickness, returned home."
This is only one observation out of many ; and it shows
(1) that since the marked ant took no larva home, she
must have given information which led the others to come
out — unless we can suppose that the smell of the larvae
she had examined still hung about her ; and (2) that the
communication was not detailed, and probably was no
more than " Come," for, when the leader of the party was
removed, the rest knew not * where to go — very possibly
knew not why they had been summoned.

Passing now to creatures of lower .organization, it is
exceedingly difficult so to divest ourselves of our own special
mental garments as to imagine what their simple and
rudimentary constructs are like. Perhaps we may fairly
surmise that, as visual olfactory and auditory organs
develop, and differentiate from a common basis of more
simple sensation, the process of outward projection has its
rudimentary inception. The earthworm, which finds its way

* Professor Max Muller suggests to me that perhaps the ants were
frightened.

Mental Processes in Animals. 359

to favourite food-stuffs buried in the earth in which it lives,
would seem to possess the power of outward projection in
a dim and possibly not very definite form. Through their
marginal bodies — simple auditory or visual organs — the
medusae may have a rudimentary form of this capacity.
In any case, they seem to have the power of localization.
Mr. Eomanes says,* "A medusa being an umbrella- shaped
animal, in which the whole of the surface of the handle
and the whole of the concave surface of the umbrella is
sensitive to all kinds of stimulation, if any point in the
last-named surface is gently touched with a camel-hair
brush or other soft (or hard) object, the handle or manu-
brium is (in the case of many species) immediately moved
over to that point, in order to examine or brush away the
foreign body." And the same author thus describes t the
process of discrimination in the sea-anemone : " I have
observed that if a sea- anemone is placed in an aquarium
tank, and allowed to fasten upon one side of the tank near
the surface of the water, and if a jet of sea-water is made
to play continuously and forcibly upon the anemone from
above, the result, of course, is that the animal becomes
surrounded by a turmoil of water and air-bubbles. Yet,
after a short time, it becomes so accustomed to this turmoil
that it will expand its tentacles in search of food, just as it
does when placed in calm water. If now one of the ex-
panded tentacles is gently touched with a solid body, all
the others close around that body in just the same way
as they would were they expanded in calm water. That
is to say, the tentacles are able to discriminate between
the stimulus which is supplied by the turmoil of the
water, and that which is supplied by their contact with
the solid body, and they respond to the latter stimulus
notwithstanding that it is of incomparably less intensity
than the former."

Here, in discrimination, we reach the lowest stage of
mental activity. It is exceedingly difficult, however, to
determine how far such simple responses to stimuli are
* " Mental Evolution in Animals," p. 82 f Ibid. p. 48.

360 Animal Life and Intelligence.

merely organic, and how far there enters a psychological
element.

I ought not, perhaps, to pass over in perfect silence the
subject of protozoan psychology. M. Binet has published
a little book on " The Psychic Life of Micro-Organisms,"
in the preface of which he says, " We could, if it were
necessary, take every single one of the psychical faculties
which M. Eomanes reserves for animals more or less
advanced on the zoological scale, and show that the greater
part of these faculties belonged equally to micro-organisms."
He says that " there is not a single infusory that cannot
be frightened, and that does not manifest its fear by a
rapid flight through the liquid of the preparation," and he
speaks of infusoria fleeing " in all directions like a flock of
frightened sheep." He attributes memory to Folliculina,
and instinct " of great precision " to Difflugia. He regards
some of these animalculse as " endowed with memory and
volition," and he describes the following stages : —
" 1. The perception of the external object.
" 2. The choice made between a number of objects.
" 3. The perception of their position in space.
" 4. Movements calculated either to approach the body
and seize it or to flee from it."

But when we have got thus far, we are brought up by
the following sentence : " We are not in a position to
determine whether these various acts are accompanied by
consciousness, or whether they follow as simple physio-
logical processes." Since, therefore, the fear, memory,
instinct, perception, and choice, spoken of by M. Binet,
may be merely physiological processes (though, of course,
they may be accompanied by some dim unimaginable form
of consciousness), it seems scarcely necessary to say more
about them here.

I have now said all that is necessary, and all that I
think justified by the modest scope of this work, concerning
the process of construction in animals, and the nature of
the constructs we may presume that they form. The pro-

Mental Processes in Animals. 361

cess I hold to be similar in kind throughout the animal
kingdom wherever we may presume that it occurs at all.
But the products of the process seem to me to be pre-
sumably widely different. If we steadily bear in mind the
fact that the world of man is a joint product of an external
existence and the human mind, and then ask whether it is
conceivable that the joint products of this external existence
and the dog-mind, the bird-mind, the fish-mind, the bee-
mind, or the worm-mind are exactly or even closely
similar, we must, it seems to me, answer the question with
an emphatic negative.

We will now consider the nature of the inferences of
animals. It will be remembered that a distinction was
drawn between perceptual inferences and inferences in-
volving a conceptual element. As I use the words, per-
ceptual inferences are a matter, at most, of intelligence ;
but conceptual inferences involve the higher faculty of
reason.

It will be necessary here to say somewhat more than
I have already said concerning inference. When I see
an orange, that object is mentally constructed at the
bidding of certain sight-sensations. All that is actually
received is the stimulus of the retinal elements ; the rest is
suggested and supplied by the activity of the mind. It is
sometimes said that this complementary part of the per-
ception is inferred. So, too, when I hear a howl in the
street which suggests the construct dog, it may be said
that I infer the presence of the dog. And again, when the
dog is perceived to be in pain, it may be said that this is
an inference. Now, although the use of the word " infer-
ence " to denote the complementary part of a percept
seems a little contrary to ordinary usage, still there are
some advantages in so — with due qualification — employing
it. But since, as it seems to me, the characteristic of the
inference, if so we style it, in the formation of constructs
by immediate association is its unconscious nature (i.e.
unconscious as a process) we may perhaps best meet the

362 Animal Life and Intelligence.

case by speaking of these as unconscious inferences. When
the inference is not immediate and unconscious, but in-
volves a more individual conscious act of the mind in the
perceptual sphere, we may speak of it as intelligent ; and
when the inference can only be reached by analysis and the
use of concepts, we may call it rational.

Denning, therefore, "inference" as the passing of the
mind from something immediately given to something not
given but suggested through association and experience,
we have thus three stages of inference : (1) unconscious
inference on immediate construction (perceptual) ; (2) in-
telligent inference, dealing with constructs and reconstructs
(perceptual) ; and (3) rational inference, implying analysis
and isolation (conceptual).

Concerning unconscious inferences in animals, I need
add nothing to that which I have already said concerning
the process of construction. It is concerning the intelligent
inferences * of animals that I have now to speak.

I do not propose here to bring forward a number of
new observations on the highly intelligent actions which
animals are capable of performing. Mr. Komanes has
given us a most valuable collection of anecdotes on the
subject in his volume on "Animal Intelligence." It is
more to my purpose to discuss some of the more remark-
able of these, and endeavour to get at the back of them,
so as to estimate what are the mental processes involved.
In doing so, the principle I adopt is to assume that the
inferences are perceptual, unless there seem to be well-
observed facts which necessitate the analysis of the

* These fall under the " practical intelligence " of Mr. Mivart. All their
intelligent activities, in his view, are performed by the exercise of merely
sensitive faculties, through their " consentience." I agree to so large an
extent with Mr. Mivart in his estimate of animal intelligence, and in his
psychological treatment, that I the more regret our wide divergence when we
come to the philosophy of the subject. I am with him in believing that
conception and perception, in the sense he uses the words, are beyond the
reach of the brute. But I see no reason to suppose that these higher faculties
differ in kind from the lower faculties possessed by animals. They differ
generically, but not in kind. I believe that, through the aid of language,
the higher faculties have been developed and evolved from the lower faculties.
Here, therefore, 1 have to part company from Mr. Mivart.

Mental Processes in Animals. 363

phenomena, the formation of isolates, and therefore the
employment of reason (as I have above defined it). In doing
this, I shall seem to differ very widely from Mr. Eomanes
and other interpreters of animal habits and intelligence.
But I believe that the divergence is less wide than it
seems. I believe that it is largely, but I fear not entirely,
a question of the terms we employ.

Why, then, rediscuss the question under these new
terms? Because I believe that such rediscussion may
place the matter in a fresh and, perhaps, clearer light.
The question of the relation of animal intelligence to
human reason is one upon which there is a good deal of
disagreement, and one that has been discussed and re-
discussed. I seek to put it in a somewhat new light. I
have endeavoured to define carefully and accurately the
terms I use, and the sense in which I use them. I have
coined for my own purposes unfamiliar terms such as
"construct," "isolate," and "predominant," that I might
thereby be enabled to avoid the use of terms which, from
the different senses in which they are employed by different
writers, have become invested with a certain ambiguity.
I trust, therefore, that even those with whom I seem most
to disagree will allow that my aim has not been mere
disputation, but scientific accuracy and precision in a
difficult subject where these qualities are of essential
importance.

I take first some observations communicated by Mr.
H. L. Jenkins to Mr. Eomanes, since, though they raise a
point which we have already shortly considered, they form
a transition from unconscious to perceptual inferences.
Speaking of the intelligence of the elephant, Mr. Jenkins
says,* "What I particularly wish to observe is that there
are good grounds for supposing that elephants possess
abstract ideas ; for instance, I think it is impossible to
doubt that they acquire, through their own experience,
notions of hardness and weight." He then details obser-
vations which show that elephants at first hand up things
* Romanes, " Animal Intelligence," p. 401.

364 Animal Life and Intelligence.

of all kinds to their mahouts with considerable force, but
that after a time the soft articles are handed up rapidly
and forcibly as before, but that hard and heavy things are
handed up gently. " I have purposely," he says, " given
elephants things to lift which they could never have seen
before, and they were all handled in such a manner as
to convince me that they recognized such qualities as
hardness, sharpness, and weight."

Now, the question I wish here to ask is — Do the
observations of Mr. Jenkins, the nature of which I have
indicated, afford good or sufficient reasons for supposing
that these animals possess abstract ideas ? And I reply —
That depends upon what is meant by abstract ideas. If it
is implied that the abstract ideas are isolates; that is,
qualities considered quite apart from the objects of which
they are characteristic, I think not. But if Mr. Jenkins
means that elephants, in a practical way, "recognize such
qualities as hardness, sharpness, and weight " as pre-
dominant elements in the constructs they form, I am quite
ready to agree with him. I much question, however,
whether there is any conscious inference in the matter.
The elephant sees a new object, and unconsciously and
instinctively builds the element hardness or weight into
the construct that he forms. And he shows his great
intelligence by dealing in an appropriate manner with the
object thus recognized. But I do not think any reasoning
is required ; that is to say, any process involving an
analysis of the phenomena with subsequent synthesis, any
introduction of the conceptual element.

Let us consider next an observation which shows a
very high degree of perceptual intelligence on the part of
the dog. Several observers have described dogs, which
had occasion to swim across a stream, entering the water
at such a point as to allow for the force of the current.
And both Dr. Eae and Mr. Fothergill communicated to Mr.
Eomanes instances * of the dog's observing whether the
tide was ebbing or flowing, and acting accordingly. Now,

* " Animal Intelligence," p. 465.

Mental Processes in Animals. 365

I believe that the dog performs this action through in-
telligence, and that man explains it by reason. The dog
has presumably had frequent experience of the effect of
the stream in carrying him with it. He has been carried
beyond the landing-place, and had bother with the mud ;
but when he has entered the stream higher up, he has
nearly, if not quite, reached the landing-stage. His keen
perceptions come to his aid, and he adjusts his action nicely
to effect his purpose.

On the bank sits a young student watching him. He
sees in the dog's action a problem, which he runs over
rapidly in his mind. Velocity of stream, two miles an
hour. Width, -one-eighth of a mile. Dog takes ten
minutes to swim one-eighth of a mile. Distance flowed
by the stream in ten minutes, one-third of a mile. Clever
dog that ! He allows just about the right distance. A
little short, though ! Has rather a struggle at the end.

The dog intelligently performs the feat ; the lad reasons
it out.

I do not know whether I am making my point suffi-
ciently clear. A wanton boy is constantly throwing stones
at birds and all sorts of objects. He does not know much
about the force of gravitation or the nature of the curve
his stone marks out ; but he allows pretty accurately for
the fall of the stone during its passage through the air.
He acquires a catapult ; and, being an intelligent lad, he
perceives that he must aim a little above the object he
wishes to hit. This is a perceptual inference. Eeason
may subsequently step in and explain the matter, or very
possibly, being human, sparks of reason fly around his
intelligent action.

Am I using the word "reason" in an unnatural and
forced sense ? I think not. My use is in accord with the
normal use of the word by educated people. Two men are
working in the employ of a mechanical engineer. Listen
to their employer as he describes them. " A most intelligent
fellow is A ; he does everything by rule of thumb ; but he's
wonderfully quick at perceiving the bearing of a new bit of

366 Animal Life and Intelligence.

work ; he sees the right thing to do, though he cannot tell
you why it should be done. Now, B is a very different
man ; he is slow, but he reasons everything out. A knows
the right thing to do ; and B can tell you why it must be
done. A has the keenest intelligence, but B the clearest
reasoning faculty. If I have occasion to question them
about any mechanical contrivance, A says, ' Let me see it
work ; ' but B says, ' Let me think it out.' "

In other words, A, the intelligent man, deals with
phenomena as wholes, and his perceptual inferences are
rapid and exact ; while B, the reasoner, analyzes the
phenomena, and draws conceptual inferences about them.

Let us take next Dr. Eae's* most interesting description
of the cunning of Arctic foxes. These clever animals, he
tells us, soon learn to avoid the ordinary steel and wooden
traps. The Hudson Bay trappers, therefore, set gun-traps.
The bait is laid on the snow, and connected with the
trigger of the gun by a string fifteen or twenty feet long,
five or six inches of slack being left to allow for contraction
from moisture. The fox, on taking tip the bait, discharges
the gun and is shot. But, after one or more foxes have
been shot, the cunning beasts often adopt one of two
devices. Either they gnaw through the string, and then
take the bait ; or they tunnel in the snow at right angles
to the line of fire, and pull the bait downwards, thus dis-
charging the gun, but remaining uninjured. This is
regarded by Dr. Eae as a wonderful instance of " abstract
reasoning."

Here, again, it is the "abstract reasoning" that I
question. Do the clever foxes resemble the intelligent
workman A, or the abstract reasoner B ? I believe that
their actions are the result of perceptual inferences. They
adopt their cunning devices after one or more foxes have
been shot. Their keen perceptions (let me repeat that the
perceptions of wild animals are extraordinarily keen) lead
them to see that this food, quiet as it seems, has to be
taken with caution.

* " Animal Intelligence," p. 430 ; and Nature, vol. xix. p. 409.

Mental Processes in Animals. 367

With regard to the devices adopted, I think we need
further information. Do Arctic foxes tunnel in the snow
for any other purposes ? What is the proportion of those
who adopt this device to those who gnaw through the
string ? Have careful and reliable observers watched the
foxes ? or are their actions, as described by Dr. Kae,
inferences, on the part of the trappers, from the state of
matters they found when they came round to examine
their traps ? Without fuller information on these points,
it is undesirable to discuss the case further. Even if we
had full details, however, we should be as little able to get
at the process of perceptual inference in the case of the fox
as we are in the case of the intelligent workman, who sees
the right thing to do, but cannot tell you how he reached
the conclusion.

No one can watch the actions of a clever dog without
seeing how practical he is. He is carrying your stick in
his mouth, and comes to a stile. A young puppy will go
blundering with the stick against the stile, and, perhaps,
go back home, or get through the bars and leave the stick
behind. But practical experience has taught the clever
dog better. He lays down the stick, takes it by one end,
and draws it backwards through the opening at one side of
the stile. A friend tells me of a dog which was carrying a
basket of eggs. He came to a stile which he was accus-
tomed to leap, poked his head through the stile, deposited
the basket, ran back a few yards, took the stile at a bound,
picked up the basket, and continued on his course. " In-
telligent fellow ! " I exclaim. "Yes," says my friend, "he
knew the eggs would break if he attempted to leap with the
basket ! " This is just the little gratuitous, unwarrantable,
human touch which is so often filled in, no doubt in perfect
good faith, by the narrators of anecdotes. Against such
interpolations we must be always on our guard. It is
so difficult not to introduce a little dose of reason.

Mr. Eomanes obtained from the Zoological Gardens at
Eegent's Park a very intelligent capuchin monkey, on
which his sister made a series of most interesting and

368 Animal Life and Intelligence.

valuable observations. This monkey on one occasion got
hold of a hearth-brush, and soon found the way to unscrew
the handle. After long trial, he succeeded in screwing it
in again, and throughout his efforts always turned the
handle the right way for screwing. Having once succeeded,
he unscrewed it and screwed it in again several times in
succession, each time with greater ease. A month after-
wards he unscrewed the knob of the fender and the bell-
handle beside the mantelpiece. Commenting on these
actions, Mr. Romanes speaks* of "the keen satisfaction
which this monkey displayed when he had succeeded in
making any little discovery, such as that of the mechanical
principle of the screw."

I once watched, near the little village of Ceres, in South
Africa, a dung-beetle trundling his dung-ball over an
uneven surface of sand. The ball chanced to roll into a
sand hollow, from which the beetle in vain attempted to
push it out. The sides were, however, too steep. Leaving
the ball, he butted down the sand at one side of the hollow,
so as to produce an inclined plane of much less angle, up
which he then without difficulty pushed his unsavoury
sphere.

Now, it seems to me that, if we say, with Mr. Eomanes,
that the brown capuchin discovered the principle of the
screw, we must also say that the dung-beetle that I observed
in South Africa was acquainted with the principle of the
inclined plane. Such an expression, I contend, involves
an unsatisfactory misuse of terms. A mechanical principle
is a concept, f and as such, in my opinion, beyond the
reach of the brute — monkey or beetle. That of which the
monkey is capable is the perceptual recognition of the fact
that certain actions performed in certain ways produce
certain results. Why they do so he neither knows nor
cares to know. What the brown capuchin discovered was

* " Animal Intelligence," p. 497.

t Mr. Romanes regards it as, in the case of the capuchin, a recept. But
when he speaks of a generic idea of causation, and generic ideas of principles,
and of qualities as recepts, I find it exceedingly difficult to follow him. They
seem to me to be concepts supposed to be formed in the absence of language.

Mental Processes in Animals. 369

not the principle of the screw, but that the action of screw-
ing produced the results he desired — a very different
matter. My friend, Mr. S. H. Swayne, tells me that the
elephant at the Clifton Zoo, having taking a tennis-racket
from a boy who had been plaguing him, broke it by leaning
it against a step and deliberately stepping on it in the
middle, where it was unsupported. A most intelligent
action. And it would have been a capital piece of exercise
for the lad's reasoning power, had he been required to
analyze the matter, to show why the elephant's action had
the desired effect, and set forth the principle involved. I
do not think the elephant himself possesses the faculty
requisite for such a piece of reasoning. He is content
with the practical success of his actions; principles are
beyond him.

I will now give two instances of intelligence in verte-
brates which exemplify phases of inference somewhat
different from those which we have so far considered. Mr.
Watson, in his " Reasoning Power of Animals,"* tells of an
elephant which was suffering from eye-trouble, and nearly
blind. A Dr. Webb operated on one eye, the animal being
made to lie down for the purpose. The pain was intense,
and the great beast uttered a terrific roar. But the effect
was satisfactory, for the sight was partially restored. On
the following day the elephant lay down of himself, and
submitted quietly to a similar operation on the other eye.
No doubt the elephant's action here was, in part, the result
of its wonderful docility and training. But there was also
probably the inference that, since Dr. Webb had already
given him relief, he would do so again. The anticipation
of relief outmastered the anticipation of immediate dis-
comfort or pain. I do not think, however, that any one
is likely to contend that any rational analysis of the
phenomena is necessarily involved in the elephant's
behaviour.

The other instance I will quote was communicated by
Mr. George Bidie to Nature.] He there gives an account

* Page 54. t Vol. xx. p. 96.

2 B

370 Animal Life and Intelligence.

of a favourite cat which, during his absence, was much
plagued by two boys. About a week before his return the
cat had kittens, which she hid from her tormentors behind
the book-shelves in the library. But when he returned
she took them one by one from this retreat, and carried
them to the corner of his dressing-room where previous
litters had been deposited and nursed. Here abnormal
circumstances and the reign of anarchy and persecution
forced her to adopt a hiding-place where she might bring
forth her young; but the return of normal conditions,
sovereignty, and order led her to take up her old quarters
under the protection of her master. Now, look at the
description I have given in explanation of her conduct.
See how it bristles with conceptual terms : "abnormal," with
its correlative "normal;" "anarchy and persecution,"
"protection " and "order." All this, I believe, is mine, and
not the cat's. For her there was a practical perception,
in the one case of plaguing boys, in the other case of
protecting master ; and her action was the direct outcome
of these perceptions through the employment of her intelli-
gence.

Some stress fcas been laid on the occasional use of tools
by animals. Mr. Peal* observed a young elephant select
a bamboo stake, and utilize it for detaching a huge
elephant-leech which had fixed itself beneath the animal's
fore leg near the body. "Leech-scrapers are," he says,
" used by every elephant daily." He also saw an elephant
select and trim a shoot from the jungle, and use it as a
switch for flapping off flies. How far, we may ask, do
such actions imply " a conscious knowledge of the relation
between the means employed and the ends attained"?!
That, again, depends upon how much or how little is
implied in this phrase.

A boy picks up a stone and throws it at a bird ; he
comes home and unlocks the garden-gate with a key ; he
enters his room, and removes the large " Liddell and

* Nature, vol. xxi. p. 34.

t Komanes, " Animal Intelligence," p. 17 : Definition of reason.

Mental Processes in Animals. 371

Scott " which he uses as a convenient object to keep the
lid of his play-box shut ; he opens the box, and cuts him-
self a slice of cake with his pocket-knife. Then he goes
to his tutor, who is teaching him about means and ends,
and their relation to each other. He is told that the
throwing of the stone was the means by which the death
of the bird, or the end, was to be accomplished ; that the
use of the knife was the means by which the end in view,
the severance of a piece of cake, was to be effected, and so
on. He is led to see that the employment of a great many
different things, differing in all sorts of ways — stones, keys,
lexicons, and knives — may be classified together as means ;
and that a great many various effects, the death of a bird
or the cutting a bit of cake, may be regarded as ends. He
is told that when he thinks of the means and the ends
together, as means and end, he will be thinking of their
relationship. And it is explained to him that means and
ends and their relationships are concepts, and involve the
exercise of his reasoning powers.

Weary and sick to death of concepts and relationships
and reason, at length he escapes to the garden. Picking
up a light stick, he sweeps off the heads of some peculiarly
aggravating poppies, and determines to think no more of
means and ends, continuing to use the stick meanwhile as
a most appropriate means to the end of decapitating the
poppies. By all which I mean to imply that there is a
great difference between selecting and using a tool for an
appropriate purpose, and possessing a conscious knowledge
of the relation between the means employed and the ends
attained. I do not think that any conception of means,
or end, or relationship is possible to the brute. But I
believe that the elephant can perceive that this stick will
serve to remove that leech. And if this is what Mr.
Eomanes means by its possessing a conscious knowledge
of the relation between the means employed and the ends
attained, then I am, so far, at one with him in the inter-
pretation of the facts, though I disagree with his mode of
expressing them.

372 Animal Life and Intelligence.

I do not propose to consider particular instances of
intelligent inferences as displayed by the invertebrates.
Bees in the manipulation of their comb, ants in the
economy of their nest, spiders in the construction of their
web and the use they make of their silken ropes, show
powers of intelligent adaptation which cannot fail to excite
our wonder and admiration. But apart from the fact that
insect psychology is more largely conjectural than that of
the more intelligent mammals, a consideration of these
actions would only lead me to reiterate the opinion above
frequently expressed. In a word, I regard the bees in their
cells, the ants in their nests, the spiders in their webs, as
workers of keen perceptions and a high order of practical
intelligence. But I do not, as at present advised, believe
that they reason upon the phenomena they deal with so
cleverly. Intelligent they are ; but not rational.

Once more, let me repeat that the sense in which I use
the words "rational" and "reason" must be clearly
understood and steadily borne in mind. Mr. Eomanes
uses them in a different sense. " Eeason," he says,* " is
the faculty which is concerned in the intentional adapta-
tion of means to ends. It therefore implies the conscious
knowledge of the relation between means employed and
ends attained, and may be exercised in adaptation to cir-
cumstances novel alike to the experience of the individual
and to that of the species. In other words, it implies the
power of perceiving analogies or ratios, and is in this sense
equivalent to the term 'ratiocination,' or the faculty of
deducing inferences from a perceived equivalency of rela-
tions. This latter is the only sense of the word that is
strictly legitimate."

It is not my intention to criticize this use of the term
" reason." Whether animals are capable of a conscious
knowledge of the relation between means employed and
ends attained, depends, as we have already seen, upon how
much is implied by the word " knowledge " — whether the
knowledge is perceptual or conceptual. My only care is

* " Mental Evolution in Animals," p. 318.

Mental Processes in Animals. 373

to indicate what seem to me the advantages of the usage
(legitimate or illegitimate) I adopt.

I repeat, then, that the introduction of the process of
analysis appears to me to constitute a new departure in
psychological evolution ; that the process differs generically
from the process of perceptual construction on which it is
grafted. And I hold that, this being so, we should mark
the departure in every way that we can. I mark it by a
restriction of the word "intelligence" to the inferences
formed in the field of perception ; and the use of the word
" reason " when conceptual analysis supervenes. Whether
I am justified in so doing, whether my usage is legitimate
or not, I must leave others to decide. But, adopting this
usage, I see no grounds for believing that the conduct of
animals, wonderfully intelligent as it is, is, in any instances
known to me, rational.

I say that the introduction of the process of analysis
appears to me to constitute a new departure. This, how-
ever, must not be construed to involve any breach of
continuity.

I do not believe that there is or has been any such
breach of continuity. Take a somewhat analogous case.
I regard the introduction of aerial respiration in animal
life as a new departure. Organisms which had hitherto
been water-breathers became air-breathers. But I do not
imagine that there was any breach of continuity in respira-
tion. The tadpole begins life as a water-breather only ;
the frog into which he develops is an air-breather; but
there is no breach of continuity between the one state and
the other. So, too, the little child dwells in the perceptual
sphere ; the man into whom he develops is capable of
conceptual thought; but there is no breach of continuity
in the mental life of the child. It is true that, with all
our talk on the subject, we cannot say exactly when in this
continuous mental life the new departure is made. But
this is no proof whatever that there is no new departure.
In a sigmoidal curve there is a new departure where the
convex passes into the concave. We may find it difficult

374 Animal Life and Intelligence.

to mark the exact point of change. But that does not in-
validate the fact that the change does actually take place.

If I be asked how, in the course of mental evolution, the
new departure was rendered possible, I reply — Through
language. The first step was, I imagine, the naming of
predominants. If Noire and Professor Max Miiller be
correct in their views, language took its origin in the asso-
ciation of an uttered sound with certain human activities.
The action thus named was, so to speak, floated off by its
sign. By diacritical marks attached to the word, the
agent, the action, and the object of the action were distin-
guished, and thus came to be differentiated the one from
the other. Inseparable in fact, they came henceforth to
be separable in thought. Here was analysis in the germ.
The action or activity was isolated, and henceforth stood
forth as an element in abstract thought. All the busy
world around was interpreted in terms of activities. The
host of heaven and all the powers of earth were named
according to their predominant activities. The moon
became the measurer, the sun the shining one, the wind the
one who bloweth, the fire the purifier, and so forth. Our
verbs and nouns, then, being named predominants (agents,
actions, or objects), adjectives and adverbs were subse-
quently introduced to qualify these by naming a quality less
predominant, or to indicate the how, the when, and the where.
When once the different activities and different qualities
came to be named or symbolized, they were, as I say,
floated off from the agents or objects, and through isolation
entered the conceptual sphere. The named predominant
became an isolate. Body and mind became separable in
thought ; the self was differentiated from the not-self; the
mind was turned inwards upon itself through the isolation
of its varying phases ; and the consciousness of the brute
became the self-consciousness of man.

Language, and the analytical faculty it renders possible,
differentiates man from the brute. " If a brute," says Mr.
Mivart,* "could think 'is,' brute and man would be

* " Lessons from Nature," pp. 226, 227.

Mental Processes in Animals. 375

brothers. ' Is ' as the copula of a judgment implies the
mental separation and recombination of two terms that
only exist united in nature, and can, therefore, never have
impressed the sense except as one thing. And ' is,' con-
sidered as a substantive verb, as in the example, ' This
man is/ contains in itself the application of the copula of
judgment to the most elementary of all abstractions —
' thing ' or ' something.' Yet if a being has the power of
thinking 'thing' or 'something,' it has the power of
transcending space and time by dividing or decomposing
the phenomenally one. Here is the point where instinct
[intelligence] ends and reason begins." I regard this as
one of the truest and most pregnant sentences that Mr.
Mivart has written.

And when once the Logos had entered into the mind of
man, and made him man, it slowly but surely permeated
his whole mental being. Hence language is not only
involved in our concepts, but also in our percepts, in so far
as they are ours. Professor Max Miiller goes so far as to
question whether an unnamed percept is possible. And
adult intellectual man is so permeated by the Logos that I
am not prepared to disagree with him when he says that
he has no unnamed perceptions. Nevertheless, the actions
of the speechless child and our dumb companions show
that they (children and animals) are capable of forming
mental products of the perceptual order. But here, once
more, we must not forget that it is in terms of these adult
human percepts that we interpret the percepts of children
and animals ; that in doing so we cannot divest ourselves
of the garment of our conceptual thought, that we cannot
banish the Logos, and that, therefore, these percepts other
than ours cannot be identical with ours, though they are of
the same order, saving their conceptual element. We may
put the matter thus —

(1) x X dog-mind 1 Percepts to be interpreted in terms of (4), being

(2) x X cat-mind = | anal thereto but not identical therewith.

(3) x X infant-mind J

(4) x X adult human mind = the percepts of psychologists, named or

namable.

376 Animal Life and Intelligence.

If the views that I have thus very briefly sketched (for
I have no right to offer an opinion on a question of
linguistic science) be correct, language has made analysis,
isolation, and conceptual thought possible. But there may
have been a transitory stage when the word-signs stood for
predominants, not yet for isolates. Granting the possibility
or probability of this, I am prepared to follow Professor
Max Miiller in his contention that language and thought,
from the close of that stage onward, are practically in-
separable, and have advanced hand-in-hand. It is true
that I can now think out a chemical or physical problem
without the use of words — the stages of the experimental
work being visualized, just as a chess-player may think out
a game in pictures of the successive moves. But, his-
torically, I believe the power to do this has been acquired
through language ; and if I am able temporarily to isolate
and analyze without language, thought being at times a
little ahead of naming, yet the fact remains that language
is absolutely necessary to make such advances good, if not
for me, at any rate for man.

And here I would make one more suggestion. Professor
Max Miiller, as the result of analysis of the Aryan language,
finds a comparatively small number of roots which he says
are in all cases symbolic of concepts. Yes, for us now they
symbolize concepts. But in their inception may they not
have been symbolic of predominants? Have we not in
them the signs for predominants not yet converted for the
primitive utterers into isolates ? May not these haye been
the stepping-stones from the perceptual predominants of
animal man, to the conceptual isolates of rational man ?
Or, to modify the analogy, may they not have been the
embryonic wings by which the human race were floated off
from the things of sense into the free but tenuous air of
abstract thought ?

Lastly, before taking leave of the subject of this chapter,
I am most anxious that it should not be thought that, in
contending that intelligence is not reason, I wish in any
way to disparage intelligence. Nine-tenths at least of the

Mental Processes in Animals. 377

actions of average men are intelligent and not rational.
Do we not all of us know hundreds of practical men who
are in the highest degree intelligent, but in whom the
rational, analytic faculty is but little developed ? Is it any
injustice to the brutes to contend that their inferences are
of the same order as those of these excellent practical
folk ? In any case, no such injustice is intended ; and if I
deny them self-consciousness and reason, I grant to the
higher animals perceptions of marvellous acuteness and
intelligent inferences of wonderful accuracy and precision
— intelligent inferences in some cases, no doubt, more
perfect even than those of man, who is often distracted by
many thoughts.

378 Animal Life and Intelligence.

CHAPTEE X.

THE FEELINGS OF ANIMALS : THEIR APPETENCES AND EMOTIONS.

THERE is one aspect of the mental processes of men and
animals that we have so far left unnoticed — the aspect of
feeling, the aspect of pleasure and pain. Quite distinct
from, and yet intimately associated with, our perception of
a beautiful scene, is the pleasure we derive therefrom ; and
quite distinct from, and yet inseparably bound up with,
our perception of a discordant clang, is the painful effect
that it produces.

We have, however, no separate organs for the apprecia-
tion of pleasure and pain. These feelings arise out of, and
are bound up with, our sensations, our perceptions, and
especially with the conscious exercise of our bodily activities.
There may be, at any rate in some cases, separate nerves
for the appreciation of the pleasurable and the painful ;
but even if this be so, these shades of feeling are so closely
associated with our other activities, mental and bodily,
that we may for the present regard them simply as the
accompaniments of these activities.

The question has been raised and much discussed
whether all our activities are accompanied by some shade
or colouring of feeling, pleasurable on the one hand, or
painful on the other ; or whether some of these activities
may not be indifferent in this respect, affording us neither
pleasure nor pain. Put in this way, I think we may say
that there may be activities which are thus indifferent.
But if it be asked whether, in addition to the pleasurable
and painful feelings, there is a third class of feelings, which
we may call indifferent or neutral, I am inclined to answer

Appetence and Emotion. 3/9

it in the negative. I hold that every feeling, as such, must
belong either to the painful or pleasurable class, and that
if the pleasurable and painful, so to speak, exactly balance
each other, then feeling, as such, does not emerge into
consciousness at all. For, as Lotze says, " We apply the
name ' feelings ' exclusively to states of pleasure and pain,
in contrast with sensations as [the elements of] indifferent
perceptions of a certain content."

The broadest division of the feelings is, therefore,
into pleasurable on the one hand, and painful on the
other.

Another general question with regard to the feelings is —
With what condition or state of the bodily organization are
they associated ? In answer to this question we may say
(1) that any very violent and abnormal stimulus produces
pain ; (2) that the conditions of pleasure are to be sought
within the limits of the healthy and normal exercise of the
bodily functions and mental activities; (3) that within
these limits the changes of activity consequent upon the
rhythmic flow of normal organic processes bring with
them, in the aggregate, pleasure, the delight of healthy
life; (4) that within these limits, again, we experience
pleasure or pain, enjoyment or weariness, ease or discom-
fort, happiness or unhappiness, with the continued rise and
fall of our life-tide. For, as Spinoza says, " We live in per-
petual mutation, and are called happy or unhappy accord-
ing as we change for the better or the worse." So long
as our activities remain at a dead level, there is indifference
— neither pleasure nor pain. A rise of the tide of activity
brings pleasure, a fall the reverse. Lastly, we may say
(5) that beyond the limits of healthy and normal exercise
there is, on the one hand, excessive exercise which, carried
far enough, may give rise, first to fatigue, and then to
acute pain; and, on the other hand, deficient exercise,
which may produce that dull and numb form of pain which
we call discomfort, or a sense of craving or want.

Pleasures and pains may thus be either massive or
acute, diffused or locally concentrated. On the whole, we

380 Animal Life and Intelligence.

may say, \vith Mr. Grant Allen,* that " the acute pains, as
a class, arise from the action of surrounding destructive
agencies; the massive pains, as a class, from excessive
function or insufficient nutriment." But since massive
pains, when pushed to an extreme, merge into the acute
class, " the two classes are rather indefinite in their limits,
being simply a convenient working distinction, not a
natural division." "Massive pleasure can seldom or never
attain the intensity of massive pain, because the organism
can be brought down to almost any point of innutrition
or exhaustion; but its efficient working cannot be raised
very high above the average. Similarly, any special organ
or plexus of nerves can undergo any amount of violent
disruption or wasting away, giving rise to very acute pains ;
but organs are very seldom so highly nurtured and so long
deprived of their appropriate stimulant as to give rise to
very acute pleasure." The amount of pleasure varies,
according to Mr. Grant Allen, whose discussion of the
subject is, perhaps, the best and clearest we have, directly
as the number of nerve-fibres involved, and inversely as
the natural frequency of their excitation. No doubt the
principles above sketched out are somewhat vague and
general ; but we are scarcely justified in formulating any
that are more precise and exact.

Accepting now the theory of evolution, we may say,
furthermore, that during the long process of the moulding
of life to its environment, there has been a constant
tendency to associate pleasure with such actions as con-
tribute towards the preservation and conservation of the
individual and the race, and to associate pain with such
actions as tend to the destruction or detriment of the
individual or the race. For there can be little doubt that
pleasure and pain are the primary incentives to action.
Without the association of pleasure with conservative
action, and pain with detrimental action, it is difficult to
conceive how the evolution of conscious creatures would
be possible. Conservative action, if it is to be persisted

* " Physiological ^Esthetics : " chapter on " Pleasure and Pain."

Appetence and Emotion. 381

in by a conscious creature, must be associated directly or
indirectly with pleasurable feelings ; nay, more, if it is to
be persistently persevered in, its non-performance must be
associated with that dull form of pain which we call a
craving or want. Only under such conditions could
activities which tend to the survival of the individual and
the race be fostered and furthered.

It must be remembered, however, that such association
is founded on experience, and has no necessary validity
beyond experience. That quinine, though unpleasant to
the taste, is, under certain circumstances, beneficial to the
individual, and that acetate of lead, though sweet-tasted,
is harmful, cannot be fairly urged in opposition to this
principle, since the effects of these drugs form no part of
the normal experience of the individual and the race. Nor
can it be fairly objected that animals transported to new
countries often eat harmful and poisonous plants pre-
sumably because they are nice ; for these plants form part
of an unwonted environment. Nor, again, is the fact that
the association of pleasure with conservative action and
pain with harmful action is not always perfect, in any
sense fatal to the general principle. For the establishment
of the association is still in progress ; and with the increase
in the complexity of life its accurate establishment is more
and more difficult. No one is likely to contend that what
appears to be a general principle must also be an invariable
rule. The general principle is that under the joint in-
fluence of pleasure (attractive) and pain (repellent) the
needle of animal life sets towards the pole of beneficial
action. That the needle does not always point true only
illustrates the fact that life-activities are still imperfect.

Let us notice that it is under the joint action of pleasure
and pain that the needle sets. We must not think only
of the positive aspect, and neglect the negative. What we
know as wants, cravings, appetites, desires, and dissatis-
factions, are dull and continuous pains,* which tend to

* All of these, at any rate, satisfy Mr. Herbert Spencer's definition.
Pleasure he describes as a feeling which we seek to bring into consciousness

382 . Animal Life and Intelligence.

drive us to actions by which they shall be annulled, and
the performance of which shall give us the pleasures of
gratification. Dr. Martineau regards a felt want as a
mainspring of our energy. " Life," he says,* " is a cluster
of wants, physical, intellectual, affectional, moral, each of
which may have, and all of which may miss, the fitting
object. Is the object withheld or lost ? There is pain :
is it restored or gained? There is pleasure: does it
abide or remain constant? There is content. The two
first are cases of disturbed equilibrium, and are so far
dynamic that they will not rest till they reach the third,
which is their posture of stability and their true end."
To this I would only add that the content which follows on
the keen pleasure of satisfaction is evanescent, and ere
long lapses into indifference, on which in due time follows
the dull pain resulting from the recurrent pressure of the
want or desire.

It is clear that, in introducing these wants and desires,
we are entering the sphere of the emotions, and it is some-
times said that the emotions have their basis in pleasure
and pain. If by this it is meant that the emotions often
exhibit more or less prominently one or other of these two
aspects of feeling, we may agree with the statement. It
will be well, however, to lead up to our consideration of
the emotions by taking a general review of the manner in
which the organism responds to external stimuli.

A dog is lying dreamily on the lawn in the sunshine.
Suddenly he raises his head, pricks his ears, scents the
air, looks fixedly at the hedge, and utters a low growl.
Place your hand upon his shoulder, and you will find that
his muscles are all a-tremble. He can restrain himself no
longer, and darts through the hedge. You follow him,
look over the hedge, and see that it is his old enemy, the
butcher's cur. They are moving slowly past each other,
head down, teeth bared, back roughened. You whistle

and retain there ; pain, as a feeling which we seek to get out of consciousness
and keep out.

* " Types of Ethical Theory," vol. ii. p. 350.

Appetence and Emotion. 383

softly. Such a whistle would generally bring him bounding
to your feet. But now it is apparently unheard. The two
dogs have a short scuffle, and the cur slinks off. Your dog
races after him ; but after a few minutes returns, jumps
up at you playfully, and then lies down again on the grass.
But every now and then, for ten minutes or so, he raises
his head and growls softly.

Let us briefly analyze the dog's actions, reading into
them, conjecturally, the accompaniments in consciousness.
As he lies on the lawn, he receives a sense-stimulus,
auditory or olfactory, which gives rise to the construction
of the percept dog (perhaps particularized through olfactory
discrimination). About the formation of constructs or per-
cepts, however, we have already said enough ; we have
now to consider their effects. The head is raised, the ears
pricked, and so on. The dog is on the alert. His attention
is roused. What are the physiological effects ? Certain
motor-activities or tendencies to activity. These are of
two kinds — first, in connection with the sense-organs, the
muscles of which are brought into play in such a way as
to bring the organs to bear upon the exciting object ;
secondly, in connection with many other muscles, which
are innervated, so as to be ready to act rapidly and
forcibly. The first motor-effect, that on the muscles of
the sense-organs, is a very characteristic physical con-
comitant of the psychological state which we term " atten-
tion ; " the second effect, the incipient innervation of
muscles likely to be called into play, is equally charac-
teristic of the psychological state we call alertness.

Meanwhile an emotional state is rising in the mind of
the dog. We may call it, conjecturally, anger and com-
bativeness. But what we name it does not much signify
for our present purpose. It has a growing tendency to
work itself out in a series of definitely directed actions.
And this reaches its point of culmination when the dog
rushes through the hedge and stands with bared teeth
before his antagonist. A whole set of appropriate muscles
are now strongly innervated. There is probably a double

384 Animal Life and Intelligence.

innervation — an innervation prompting to activity and an
innervation inhibiting or restraining from activity. The
attention is so concentrated that he heeds not, probably
hears not, his master's whistle. He is keenly on the alert.
Then he sees his chance; the inhibition or restraint is
withdrawn, and he flies at his opponent. The emotional
tendency works itself out in action. Even after he has
resumed his place on the lawn, memories of the emotional
state return, and lead him to lift his head, slightly bare
his teeth, and growl.

Now, with regard to the emotional state here indicated,
we may notice, first, that it is initiated by a percept ;
secondly, that associations of pleasure or pain are by no
means the most important or predominant characteristics ;
thirdly, that the motor-tendencies seem to be essential, the
emotional state being the psychological aspect of these
motor -tendencies ; and, fourthly, that we should perhaps be
justified in speaking of a presentative emotion when the
percept which gives rise to the emotion is presentative ;
and a representative emotion where the originating percept
is represented in memory. And with regard to the atten-
tion which was incidentally introduced, we may notice that
it, too, has motor-concomitants, and that it is directly
associated with the emotional state. If no emotional state
is aroused by a percept, attention is not specially directed
to the object. The concentration of the attention is directly
proportional to the intensity of the emotion evoked.

Emotions, then, would seem from this illustration to be
certain psychological states which accompany activities or
tendencies to activity. They are evoked by appropriate
objects perceived or remembered. Where the tendency is
towards the object, as in the sexual emotions, we may
speak of it as an appetence; where it is away from the
object, as in the emotion of fear, we may speak of it as an
aversion. Appetences are normally pleasurable ; aversions,
painful.

It is clear that the organism must be in a condition
fitting it to carry out its various activities. And this con-

Appetence and Emotion. 385

dition is more or less variable. In the terms of our previous
analogy (Chapter II.) the tissues are "explosive." After a
series of explosions have taken place in a tissue, its store
of explosive material becomes exhausted, and a powerful
stimulus is required to liberate further energy in the
exhausted tissue. A period of rest is required to enable
the plasmogen to generate a fresh store of explosive
material. As this store increases to its maximum pitch,
the tissue becomes more and more ready to respond at the
slightest touch. Responsiveness to external stimuli is
spoken of as sensitiveness; emotional responsiveness is
called sensibility. What we have before spoken of as a
want or craving is a state of heightened sensibility, which
often gives rise to a painful state of general uneasiness.
It may also give rise to perceptual representations in
memory, as may be seen in the dreams experienced during
a state of extreme sexual sensibility. If we seek a basis
for the emotional states, therefore, we shall find it in
sensibility rather than in pleasure and pain.

The motor-accompaniments of the emotional states
have long been known under the title of the " expression "
of the emotions. The term is too deeply rooted to be
altered ; but we may notice that what is called the expres-
sion of an emotion is really its partial fulfilment in action.
Some psychologists, dissatisfied with the term "expression
of the emotions," as seeming to imply that the emotion is
one thing and its expression another, go so far as to say
that the motor-accompaniments are the objective aspect of
what, under its subjective aspect, is the emotion. It is
quite possible, however, to experience an emotion without
any motor-accompaniments at all. Nevertheless, there is,
I believe, in such cases an unfulfilled tendency to action.

A most important feature in general physiology and
psychology is the postponement or suppression of action. The
physiological faculty on which it is based is inhibition. I
do not propose to discuss the somewhat conflicting views
on the physiological mechanism of inhibition. It is, how-
ever, a fact of far-reaching importance which no one is

2 c

386 Animal Life and Intelligence.

likely to deny. In its higher ranges it is the objective basis
and aspect of self-restraint.

A stimulus gives rise to sensation and perception ; the
perception gives origin to an emotional state; and the
emotional state is fulfilled in appropriate motor-activities.
The process is a continuous one, and, in the absence of
inhibition, would in all cases inevitably fulfil itself. But
through the faculty of inhibition, the final state of activity
may be postponed or suppressed. We may place side by
side the physiological series and the accompanying psycho-
logical series thus —

Stimulus of 1 . . f Stimulus of

> — > nervous processes in brain— > <
sense-organ/ ^ (. motor-organs.

Consciousness of 1 ( Consciousness of

sense-stimulus j^perceptl°n' emot'°^{ activity.

The arrows pointing away from perception and emotion
are intended to indicate the fact that the consciousness of
sense-stimulus on the one hand, and of activity on the
other, hand, are accompaniments of the nervous processes in
the brain, and are referred outwards to the sense-organ or
the motor-organ, as the case may be. It must be remem-
bered that the two series, physiological and psychological,
belong to distinct phenomenal orders. If one speaks of
emotion being fulfilled in activity, and thus seems to jump
from the psychological to the physiological series, one does
so merely to avoid the appearance of pedantry.

Now, by the postponement or suppression of action, the
process is either arrested in its middle phase, the motor-
organs not being innervated at all, or, as I believe to be
more probable, the motor-organs are doubly innervated, a
stimulus to activity being counteracted by an inhibitory
stimulus, the two neutralizing each other either in the
motor-organ or the efferent nerves which convey the stimuli.
In any case, there is no consciousness * of activity. And
the mind occupies itself more and more completely with
the central processes, perception, and emotion, and also, in

* Such consciousness of activity is probably associated with, the innerva-
tion of afferent, not efferent, nerves.

Appetence and Emotion. 387

human beings, conceptual thoughts and emotions. Never-
theless, at any rate so long as we confine ourselves to the
perceptual sphere, these processes have their normal fulfil-
ments in action, and, if they become sufficiently intense,
actually do so fulfil themselves.

Now, since the emotions with which we are now dealing
(we may call them emotions in the perceptual sphere) are
stages in the fulfilment of activities (though the activities
themselves may be suppressed), it is clear that there may
be as many emotional states as there are modes of activity.
Hence, no doubt, the extreme difficulty of anything like a
satisfactory classification of these emotions, especially
when the activities are regarded as a merely extraneous
expression.

Moreover, when certain emotions reach a high pitch of
intensity, they may defeat their own object, and give rise, not
to definite well-executed motor-activities, but to helpless con-
tradictory actions, affections of glandular and other organs,
and a general condition of collapse. The emotion of fear,
for example, will lead to motor-activities tending to remove
a man from the source of danger; but when it reaches
the degree of dread, or its culmination terror, the effects
are markedly different. The countenance pales, the lips
tremble, the pupils of the eyes become dilated, and there
is an uncomfortable sensation about the roots of the hair.
The bowels are often strongly affected, the heart palpitates,
respiration labours, the secretions of the glands are de-
ranged, the mouth becomes dry, and a cold sweat bursts
from the skin. The muscles cease to obey the will, and the
limbs will scarcely support the weight of the body. Here
we have all the effects of a prolonged struggle to escape.
Just as such a prolonged struggle will at length produce
these motor and other effects accompanied by the emotion
of terror ; so, if the emotion of terror be produced directly,
these motor and other effects are seen to accompany it.

Mr. Charles Eichardson, the well-known engineer of the
Severn Tunnel, has recorded several instances of railway
servants and others being so affected by the approach of a

388 Animal Life and Intelligence.

train or engine that they have been unable to save them-
selves by getting out of the way, though there was ample
time to do so. This may have been through the effect of
terror. But one man, who was nearly killed in this way,
only just saving himself in time, informed me that he
experienced no feeling of terror ; he was unable to explain
why, but he couldn't help watching the train as it darted
towards him. In this case it seems to have been a sort of
hypertrophy of attention. His attention was so rivetted
that he was unable to make, or rather he felt no desire to
make, the appropriate movements. He said, "I had to
shake myself, and only did so just in time. For in another
moment the express would have been on me. When it had
passed, I came over all a cold sweat, and felt as helpless as
a baby. I was frightened enough then." Cases of so-called
fascination in animals may be due in some cases to terror,
but more often, perhaps, to a hypertrophy of attention,
such as is seen in the hypnotic state. Speaking of the
effects of artificial light on fish, Mr. Bateson says,*
" Bass, pollack, mullet, and bream generally get quickly
away at first, but if they can be induced to look steadily
at the light with both eyes, they generally sink to the
bottom of the tank, and on touching the bottom commonly
swim away. ... In the case of mullet, effects apparently
of a mesmeric character sometimes occur, for a mullet
which has sunk to the bottom as described will sometimes
lie there quite still for a considerable time. At other times
it will slowly rise in the water until it floats with its dorsal
fin out of the water, as though paralyzed. . . . When the
light is first shown, turbot generally take no notice of it,
but after about a quarter of an hour I have three times
seen a turbot swim up, and lie looking into the lamp
steadily. It seemed to be seized with an irresistible
impulse like that of a moth to a candle, and throws itself
open-mouthed at the lamp." As a boy I used frequently
to " mesmerize " chickens by making them look at a chalk

* Journal of Marine Biological Association, New Series, vol. i. No. 2,
pp. 216, 217.

Appetence and Emotion. 389

mark. They would then lie for some time perfectly motion-
less. Some such effect has, perhaps, led to the instinct
displayed by some animals of " shamming dead."

Eeturning now to the emotions as displayed in man, we
may take one more example in anger. This is an emotion
that arises from the idea of evil having been inflicted
or threatened. " Under moderate anger," says Darwin,
" the action of the heart is a little increased, the colour
heightened, and the eyes become bright. The respiration
is likewise a little hurried ; and as all the muscles serving
for this purpose act in association, the wings of the nostrils
are sometimes raised to allow of a free draught of air ; and
this is a highly characteristic sign of indignation. The
mouth is commonly compressed, and there is almost always
a frown on the brow. Instead of the frantic gestures of
extreme rage, an indignant man unconsciously throws
himself into an attitude ready for attacking or striking his
enemy, whom he will, perhaps, scan from head to foot in
defiance. He carries his head erect, with his chest well
expanded, and the feet planted firmly on the ground. With
Europeans the fists are generally clenched." " Under rage
the action of the heart is much accelerated, or, it may be,
much disturbed. The face reddens, or it becomes purple
from the impeded return of the blood, or may turn deadly
pale. The respiration is laboured, the chest heaves, and
the dilated nostrils quiver. The whole body often trembles.
The voice is affected. The teeth are clenched or ground
together, and the muscular system is commonly stimulated
to violent, almost frantic, action. But the gestures of a
man in this state usually differ from the purposeless
writhings and struggles of one suffering from an agony of
pain ; for they represent more or less plainly the act of
striking or fighting with an enemy."

These examples will serve to remind the reader of the
nature of those complex aggregates of organized feelings
which we call emotions, and will also show the close
connection of these emotions with the associated bodily
movements and activities which constitute their normal

3QO Animal Life and Intelligence.

fulfilment. So close is this connection, that the assumption
of the appropriate attitude will conjure up a faint revival
of the associated emotion. Let any one stand with squared
shoulders, clenched fists, and set muscles, and he will find
the respiration affected, and perhaps also the heart-beat,
and will experience a faint revival of the emotion of anger.
Very different will be his feelings as he reseats himself,
abandons his limbs to a posture of leisurely repose, and
allows a pleasant smile to steal over his features.

The next point to notice about these emotions is that
they are to a large extent instinctive, and are evidenced in
the infant at so early a period that individual acquisition
is out of the question. In any case, the basis of sensibility
is innate. As Mr. Sully says,* " There are instinctive
capacities of emotion of different kinds, answering to such
well-marked classes of feeling as fear, anger, and love.
These emotions arise uniformly when the appropriate cir-
cumstances occur, and for the most part very early in life.
Thus there is an instinctive disposition in the child to feel
in the particular way known as anger or resentment when
he is annoyed or injured."

In this, as in other cases of instinctive action, of which
we shall have more to say in the next chapter, it is, of
course, impossible to say for certain how far the activities
observed are associated writh psychological states. The
activities are undoubtedly instinctive. And their perform-
ance by an adult would be accompanied by an emotional
state. It is, therefore, probable that in the very young
child they have their emotional concomitants. Still, we
must remember that oft-repeated actions tend to become
automatic, that the accompanying consciousness sinks into
evanescence, and that it is, therefore, possible that the
emotional state may not have that vividness which the
activities seem to bespeak.

There only remains, before passing on to consider the
feelings and emotions of animals, to indicate what Mr.
Sully terms f "the three orders of emotion." The first

* " Outlines of Psychology," p. 481. f Ibid. p. 494.

Appetence and Rmotion. 391

order comprises the individual and personal emotions —
those which are self-interested and have sole reference to
the individual who feels, enjoys, or suffers. They take
origin in percepts, either in presentations of sense or
representations in memory. The second order introduces
the sympathetic emotions. They are evoked on sight of
the sufferings or emotional states of others. If we see a
woman insulted, we are filled with indignation ; and this
emotion has a sympathetic origin. The third order com-
prises the complex feelings known as sentiments. They
have reference to certain qualities of objects or activities of
individuals which inspire admiration or disapprobation.
They are abstract in their nature, and belong to the con-
ceptual sphere. Such are love of truth, beauty, virtue,
liberty, justice. To become operative on conduct, however,
they need, at any rate in the case of mosfc people, to be
particularized and individualized, or brought within the
perceptual sphere, ere they arouse anything that is
emotional in much more than in name. As Dr. McCosh
has well said, "No man ever had his heart kindled by the
abstract idea of loveliness, or sublimity, or moral excellence,
or any other abstraction. That which calls forth our
admiration is a lovely scene ; that which raises wonder or
awe is a grand scene; that which calls forth love is not
loveliness in the abstract, but a lovely and loving person ;
that which evokes moral approbation is not virtue in the
abstract, but a virtuous agent performing a virtuous act.
The contemplation of the beautiful and the good cannot
evoke deep or lively emotion. He who would create
admiration for goodness must exhibit a good being per-
forming a good action."

Turning now to the lower animals, the first question
that suggests itself is — What are their capacities for
pleasure and pain? A very difficult question to answer.
We cannot, I think, hope to know how much or how little
the invertebrates feel — to what degree they are psycho-
logically sensitive. Even among the higher vertebrates we

392 Animal Life and Intelligence.

are very apt, I imagine, to over-estimate the intensity of
their feelings. Among human-folk it is not he who halloas
loudest that is necessarily most hurt. And it is only
through the expression of their feelings in cries and gestures
that we can conjecture the feelings of animals. There are
grounds for supposing fcthat savages are far less keenly
sensitive than civilized people. And we have some reason
for believing and hoping that our dumb companions are
less sensitive to pain than we are. Mr. G. A. Eowell, for
example, in his " Essay on the Beneficent Distribution of
the Sense of Pain," tells us that "a post-horse came down
on the road with such violence that the skin and sinews of
both the fore fetlock joints were so cut that, on his getting
up again, the bones came through the skin, and the two
feet turned up at the back of the legs, -the horse walking
upon the ends of its leg-bones. The horse was put into a
field close by, and the next morning it was found quietly
feeding about the field, with the feet and skin forced some
distance up the leg-bones, and, where it had been walking
about, the holes made in the ground by the leg-bones were
three or four inches deep." Mr. Lament gives a somewhat
similar observation in the case of the reindeer. " On one
occasion," he says, " we broke one of the fore feet of an
old fat stag from an unseen ambush ; his companions ran
away, and the wounded deer, after making some attempts
to follow them, which the softness of the ground and his
own corpulence prevented him doing, looked about him a
little, and then, seeing nothing, actually began to graze on
his three remaining legs, as if nothing had happened of
sufficient consequence to keep him from his dinner."
Colonel Sir Charles W. Wilson, in his work "From Korti
to Khartoum," gives similar instances with regard to
camels. " The most curious thing," he says,* " was that
they showed no alarm, and did not seem to mind being hit.
One heard a heavy thud, and, looking round, saw a stream
of blood oozing out of the wound, but the camel went on
chewing his cud as if nothing at all had happened, not

* Page 70.

Appetence and Emotion. 393

even giving a slight wince to show he was in pain." And,
again,* " I heard the rush of the shot through the air, and
then a heavy thud behind me. I thought at first it had
gone into the field-hospital ; but, on looking round, found
it had carried away the lower jaw of one of the artillery
camels, and then buried itself in the ground. The poor
brute walked on as if nothing had happened, and carried its
load to the end of the day."

With regard to this question, then, of the susceptibility
of animals to pleasure and pain, no definite answer can be
given. That they feel more or less acutely we may be
sure ; how keenly they feel we cannot tell ; but it is better
to over-estimate than to under-estimate their sensitiveness.
In any case, whether their pain be acute or dull, whether
their pleasures be intense or the reverse, we should do all
in our power to increase the pleasures and diminish the
pains of the dumb creatures who so meekly and willingly
minister to our wants.

That the bodily feelings and wants occupy a large
relative space in the conscious life of brutes can scarcely be
questioned. On the one hand are the dull pains resulting
from the organic wants and appetences, and driving the
animal to their gratification; the keen pleasure that
accompanies this gratification, when intelligence is so far
developed that it can be foreseen, being a pull in the same
direction. And on the other hand are the pleasures of
the normal and healthy exercise of the sense-organs and
bodily activities giving rise to the pleasures of existence,
the joys of active and vigorous life. In the main, these
bodily feelings, or sense-feelings, as they are sometimes
called, seem to cluster round three chief centres — food, sex,
and the free exercise of the bodily activities, including in
some cases what seems to be play. Give a wild creature
liberty and the opportunity of gratifying its appetites ;
allow its bodily functions the alternating rhythm of healthy
and vigorous exercise and restorative repose ; and its life
is happy and joyous. It is not troubled by the pressure

* Page 104.

394 Animal Life and Intelligence.

of unfulfilled ideals. The very struggle for existence, keen
as it often is, by calling into play the full exercise of the
activities, ministers to the health and happiness of brutes
as well as men. Sir W. E. Grove has preached * the
advantages of antagonism. Speaking of the rabbit, he
says, " To keep itself healthy, it must exert itself for its
food; this, and perhaps avoiding its enemies, gives it
exercise and care, brings all its organs into use, and thus
it acquires its most perfect form of life. An estate in
Somersetshire, which I once took temporarily, was on the
slope of the Mendip Hills. The rabbits on one part of it,
that on the hillside, were in perfect condition, not too fat
nor too thin, sleek, active, and vigorous, and yielding to
their antagonists, myself and family, excellent food. Those
in the valley, where the pasturage was rich and luxuriant,
were all diseased, most of them unfit for human food, and
many lying dead on the fields. They had not to struggle
for life ; their short life was miserable and their death
early; they wanted the sweet uses of adversity — that is,
of antagonism." Without endorsing the view that these
rabbits were unhealthy only because they had too much
food and comfort — for the food, though abundant, may have
been in some way noxious, and the damp situation may
have been prejudicial — we may still believe that a struggle
for life is better for animals (and men) than unlimited ease
and plenty.

Under the influence, then, of these bodily pleasures and
wants, the activities of animals are drawn out and guided.
As Darwin says, in his autobiography, t " An animal may
be led to pursue that course of action which is most
beneficial to the species by suffering, such as pain, hunger,
thirst, and fear ; or by pleasure, as in eating and drinking,
and in the propagation of the species ; or by both means
combined, as in the search for food. But pain or suffering
of any kind, if long continued, causes depression, and
lessens the power of action, yet it is adapted to make a
creature guard itself against any great or sudden evil.

* Kature, vol. xxxvii. p. 619. t Vol. i. p. 310, under date 1876.

Appetence and Emotion. 395

Pleasurable sensations, on the other hand, may be long
continued without any depressing effect ; on the contrary,
they stimulate the whole system to increased action.
Hence it has come to pass that most or all sentient beings
have been developed in such a manner, through natural
selection, that pleasurable sensations serve as their habitual
guides. We see this in the pleasure from exertion, even
occasionally of great exertion, of the body or mind — in the
pleasure of our daily meals, and especially in the pleasure
derived from sociability, and from loving our families. The
sum of such pleasures as these, which are habitual or
frequently recurrent, give, as I can hardly doubt, to most
sentient beings an excess of happiness over misery, although
they occasionally suffer much. Such suffering is quite
compatible with belief in natural selection ; which is not
perfect in its action, but tends only to render each species
as successful as possible in the battle for life with other
species, in wonderfully complex and changing circum-
stances."

Passing now from the bodily feelings and wants to the
emotions, there can be no question that the simpler
emotions, of which I have taken fear and anger as typical,
are shared with us by the dumb brutes. And the interest-
ing observations of Mr. Douglas Spalding showed beyond
doubt that they are instinctive — their manifestation being
prior to, and not the outcome of, individual experience.
Writing in Macmillan's Magazine, he says, "A young
turkey, which I had adopted when chirping within the
uncracked shell, was, on the morning of the tenth day of
its life, eating a comfortable breakfast from my hand, when
the young hawk in a cupboard just beside us gave a shrill
' Chip ! chip ! chip ! ' Like an arrow, the poor turkey shot to
the other side of the room, and stood there, motionless and
dumb with fear, until the hawk gave a second cry, when it
darted out at the open door right to the extreme end of the
passage, and there, silent and crouched in a corner, re-
mained for ten minutes. Several times during the course
of that day it again heard these alarming sounds, and in

396 Animal Life and Intelligence.

every instance with similar manifestations of fear." And
as an example of combined fear and anger, Mr. Spalding
says, " One day last month, after fondling my dog, I put
my hand into a basket containing four blind kittens three
days old. The smell my hand had carried with it sent
them puffing and spitting in a most comical fashion."

A remarkable instance of inherited antipathy in the dog
was communicated by Dr. Huggins to Mr. Darwin. He
possessed an English mastiff, Kepler, which was brought
when six weeks old from the stable in which he was born.
The first time Dr. Huggins took him out he started back in
alarm at the first butcher's shop he had ever seen, and
throughout his life he manifested the strongest and
strangest antipathy to butchers and all that pertained to
them. On inquiry, Dr. Huggins ascertained that in the
father, in the grandfather, and in two half-brothers of
Kepler the same curious antipathy was innate. Of these,
Paris, a half-brother, on one occasion, at Hastings, sprang
at a gentleman who came into the hotel at which his master
was staying. The owner caught the dog, and apologized,
saying he had never known him to behave thus before
except when a butcher came into the house. The gentle-
man at once said that was his business.

That many animals display affection towards their
offspring and their mates, towards man and towards other
companions, is a matter of familiar observation. Often
the attachments are strange, as of cats and horses, or
contrary to instinctive tendencies, as between cats and
dogs. Sometimes they are capricious, as when Mr.
Romanes's wounded widgeon conceived a strong, persistent,
and unremitting attachment to a peacock ; * or even insane,
as where a pigeon became the victim of an infatuation for
a ginger-beer bottle. Strong attachment to man is often
exhibited. Every one knows the story which Mr. Darwin
tells f of the little monkey who bravely rushed at the
dreaded baboon which had attacked his keeper. A friend

* " Mental Evolution in Animals," p. 318.
t "Descent of Man," pt. i. chap. iii.

Appetence and Emotion. 397

of my own (the Eev. George H. K. Fisk, of Capetown) tells
me the following story (which may be added to the many
similar cases reported of dogs) concerning a favourite cat
he had as a boy. It happened that the children of the
house, my friend among the number, were confined to
their room by measles. Their mother remained with the
children by day and night until they were convalescent.
She then came down and resumed her usual daily life, but
was shocked at the appearance of the cat, which was little
more than skin and bones, and would not touch food or
milk. The cat seemed to know that Mrs. Fisk could help
her, and gave her no peace till she had taken her upstairs
to the convalescent patients. To Mrs. Fisk's surprise, the
cat snarled and beat the young master with her paws.
Why the cat chose this peculiar method of venting her
feelings it is difficult to say. But immediately afterwards
she went down into the kitchen, ate the meat and drank
the milk which she had before refused to touch. Early
next morning she mewed outside the young master's room ;
and, having gained admittance, sat at the foot of the bed
until he woke, and then licked his face and hair.

This leads us on to the class of sympathetic emotions.
For the sympathetic emotions are those which centre, not
round the self, but round some other self in whose welfare
an interest is, in some way and for some reason, aroused.
Not long ago, at the Hamburg Zoological Gardens, I saw
two baboons fighting savagely. One at last retreated
vanquished, with his arm somewhat deeply gashed. He
climbed to a corner of the cage and sat down, moodily
licking his wound. Thither followed him a little capuchin,
and, though his bigger friend took mighty little notice of
his overtures, seemed anxious to comfort him, nestling
against him, and laying his head against his side. So far
as one could judge, it was not curiosity, but sympathy,
that prompted his action.

The following example of sympathetic action on the
part of a dog towards a stranger-dog is communicated to
me by Mrs. Mann, a friend of mine at the Cape. Carlo

39 8 Animal Life and Intelligence.

was a favourite black retriever, and a highly intelligent
animal. " One day," says Mrs. Mann, " a miserable-
looking white dog came into our yard. Carlo went up to
him, looking displeased, dog-fashion, and ready to fly at
the intruder. It was clear, however, that some commu-
nication passed between them, for Carlo's wrath seemed
disarmed, and he trotted into the kitchen, coming out again
with a chop-bone (one with a good deal of meat on it)
which the cook had given him. On looking into the yard,
the miserable cur was seen enjoying the bone, Carlo sitting
straight up watching him with a look of satisfaction." *

That dogs feel sympathy with man will scarcely be
questioned by any one who has known the companionship
of these four-footed friends. At times they seem in-
stinctively to grasp our moods, to be silent with us when
we are busy, to lay their shaggy heads on our knees when
we are worried or sad, and to be quickened to fresh life
when we are gay and glad — so keen are their perceptions.
Their life with man has implanted in them some of the
needs of social beings ; and as they are ever ready to
sympathize with us, so do they rejoice in our sympathy.
To be deprived of that sympathy, to be neglected, to have
no attention bestowed on them, is to some dogs a punish-
ment more bitter than direct reproof. Mr. ' Eomanes
quotes, t an account given him by Mrs. E. Picton of a Skye
terrier who had the greatest aversion to being washed,
snarling and biting during the operation. Threats, beating,
and starvation were all of no avail; but the animal was
reduced to submission by persistent neglect on the part of
his mistress. At the end of a week or ten days he looked
wretched and forlorn, and yielded himself quite quietly and

* Miss Nellie Maclagan describes how her Newfoundland similarly took
a roll to a hungry pauper-friend (Nature, vol. xxviii. p. 150). Mr. Duncan
Stewart gives (Nature, vol. xxviii. p. 31) the case of a cat who used frequently
to provide her blind mother with food. Sir Harry Lumsden states that
during the cold autumn of 1878 some tame partridges in Aberdeenshire
brought two wild coveys to be fed near the doorstep of the house. And a
case has been communicated to me by Miss Agnes Tanner, of Clifton, of a
thrush that pulled up worms on the lawn for a lame companion.

t " Animal Intelligence," p. 440.

Appetence and Emotion. 399

patiently to one of the roughest ablutions it had ever been
his lot to experience.

So far I have been content to credit animals with very
general and simple forms of emotion — anger, fear, antipathy,
affection, and some form of sympathy. If, on the perusal
of familiar anecdotes, we also credit them with jealousy,
envy, emulation, pride, resentment, cruelty, deceitfulness,
and other more complex emotional states, we must re-
member that every one of these, as we know them, is
essentially human. It is necessary to insist on the need
of caution and the danger of anthropomorphism. This
is, perhaps, even more necessary in the case of the emotions
than in that of the perceptions, which we have before con-
sidered. Even among men, different individuals and
different races probably vary far more in their emotions
than in their perceptions. The emotions of civilized man
have assumed their present form in the midst of complex
social surroundings. They one and all bear ineffaceably
stamped upon them the human image and superscription.
In terms of these complex human emotions we have to
decipher the simpler emotional states of the lower animals.
We call them by the same names ; we think of them as
like unto those that we experience. And we can do no
otherwise, if we are to consider them at all. But let us
not lose sight of the fact that all we can ever hope to see
in the mirror of the animal mind is a distorted image of
our own mental and emotional features. And since the
mirrors are of varying and unknown curvature, we can
never hope to be in a position accurately to estimate the
amount of distortion.

Eemembering this, it is always well to look narrowly at
every anecdote of animal intelligence and emotion, and
endeavour to distinguish observed fact from observer's inference.
If we take the great number of stories illustrative of revenge,
consciousness of guilt, an idea of caste, deceitfulness,
cruelty, and so forth, in the higher mammalia, we shall
find but few that do not admit of a different interpretation
from that given by the narrator. A cat's treatment of a

4co Animal Life and Intelligence.

mouse is adduced by a number of witnesses as illustrative
of cruelty ; but others see in this conduct, not cruelty, but
practice and training in an important branch of the
business of cat-life. That is to say, the act, though objec-
tively cruel from the human standpoint, is not on this view
performed from a motive of cruelty. Some time ago I
ventured to stroke the nose of a little lion-cub which had
tottered, kitten-like, to the bars of its cage. " I wish," I
said shortly afterwards to a distinguished animal painter,
" you could have caught the look of conscious dignity
(I speak anthropomorphically) with which the lioness
turned and seemed to say, 'How dare you meddle with
my child!'" "I have seen such a look and attitude,"
said Mr. Nettleship ; " but I attributed it, not to pride, but
to fear." Mr. Eomanes quotes,* as typically illustrative of
an "idea of caste," the case of Mr. St. John's retriever,
which struck up an acquaintance with a rat-catcher and
his cur, but at once cut his humble friends, and denied all
acquaintanceship with them, on sight of his master. I, on
the other hand, should regard this case as parallel with
that which I have noted a hundred times. My dogs would
go out with the nurse and children when I was busy or
absent ; but if I appeared within sight, they raced to me.
The stronger affection prevailed. A dog is described^ as
" showing a deliberate design of deceiving," because he
hobbled about the room as if lame and suffering from pain
in his foot. I would suggest that there was no pretence,
no "deliberate design of deceit," in this case, but a direct
association of ideas between a hobbling gait and more
sympathy and attention than usual. I am not denying
objective deceitfulness to the dog any more than I deny
objective cruelty to the cat. My only question is whether
the motive is deceit. We must not forget that the deceitful
intent is a piece, not of the observed fact, but of the
observer's inference. Mr. Romanes, for example, tells J of
a black retriever who was asleep, or apparently asleep, in
the kitchen of a certain dignitary of the Church. The

• " Animal Intelligence," p. 442. f Ibid. p. 444. J Ibid. p. 451.

Appetence and Emotion. 401

cook, who had just trussed a turkey for roasting, was
suddenly called away. During her temporary absence,
"the dog carried off the turkey to the garden, deposited it
in a hollow tree, and at once returned to resume his place
by the fire, where he pretended to be asleep as before."
Unfortunately, a perfidious gardener had watched him,
and brought back the turkey, so that the retriever did not
enjoy the feast he had reserved for a quiet and undisturbed
moment. Assuming that the gardener and cook were
accurate in their statement of fact, the deceitful intent is
an inference on their part, or that of the dignitary of the
Church, or Mr. Eomanes. I do not deny its correctness
from the objective standpoint. Deceitfulness is apparently
exhibited by children at a very tender age. But for us
civilized adults deceit and its converse, truthfulness in
action, mean something a good deal more definite than
for dogs and infants.

Animals are often described as harbouring feelings of
revenge and vindictiveness. To test this in the elephant,
Captain Shipp gave an elephant a sandwich of cayenne
pepper. "He then waited," says Mr. Eomanes,* "for six
weeks before again visiting the animal, when he went into
the stable, and began to fondle the elephant as he had
previously been accustomed to do. For a time no resent-
ment was shown, so that the captain began to think that
the experiment had failed ; but at last, watching an oppor-
tunity, the elephant filled his trunk with dirty water, and
drenched the captain from head to foot." Here the facts
are that an injury was received, and that the retaliation
followed after an interval of six weeks. The inference
seems to be that the elephant harboured feelings of revenge
or vindictiveness during this period. It may have been so.
It may be, however, that the elephant never once pictured
the captain during the six weeks; but, on s'eeing him
again, remembered the injury, and, as we say, paid him out.
But what we understand by revenge and vindictiveness is
the keeping of an injury before the mind for the express

* " Animal Intelligence," p. 387.

2 D

4O2 Animal Life and Intelligence.

purpose of ultimately avenging it. And this the elephant,
to say the least of it, may not have done.

In Miss Eomanes's interesting observations on the Cehus
monkey, she says,* " He bit me in several places to-day
when I was taking him away from my mother's bed after
his morning's game there. I took no notice; but he
seemed ashamed of himself afterwards, hiding his face in
his arms, and sitting quiet for a time." But, in a footnote,
we read, " On subsequent observation, I find this quietness
was not due to shame at having bitten me ; for whether he
succeeds in biting any person or not, he always sits quiet
and dull-looking after a fit of passion, being, I think,
fatigued." I quote this to illustrate the difference which I
am endeavouring to insist upon between observed fact and
observer's inference.

Mr. Eomanes comments f on the remarkable change
which has been produced in the domestic dog as com-
pared with wild dogs, with reference to the enduring of
pain. "A wolf or a fox will sustain the severest kinds
of physical suffering without giving utterance to a sound,
while a dog will scream when any one accidentally
treads upon its toes. This contrast," says Mr. Eomanes,
"is strikingly analogous to that which obtains between
savage and civilized man: the North American Indian,
and even the Hindoo, will endure without a moan an
amount of physical pain — or, at least, bodily injury —
which would produce vehement expressions of suffering
from a European. And, doubtless, the explanation is in
both cases the same ; namely, that refinement of life en-
genders refinement of nervous organization, which renders
nervous lesions more intolerable." I cannot accept this
as the most probable explanation. In the first place, the
human beings referred to have different ideals in the matter
of conduct under pain and suffering. The American Indian
and the Hindoo have a stoic ideal, which does not influence
the average European. On the other hand, the dog, from
his association with man, has learnt more and more to

* "Animal Intelligence," p. 486. f Ibid. p. 141.

Appetence and Emotion. 403

give expression to his feelings in barks, whines, and yelp-
ings. To howl at every little pain would do a wolf no
good, but rather advertise him to his enemies ; to howl
when his toes are trodden on makes most men look where
they are stepping, and probably pet the sufferer for his
pains. In the one case, to howl is disadvantageous ; in
the other, it is advantageous. I do not, however, put
forward my own explanation as necessarily more correct
than that given by Mr. Eomanes (though I regard it myself
as more probable). My object is to show that it is possible
for two observers to regard the same activities of animals,
and read into them different psychological accompaniments.
Throughout the sections of Mr. Eomanes's work which deal
with the emotions, I feel myself forced at almost every turn
to question the validity of his inferences.

From all that I have said in the last chapter, it will be
gathered that I am not prepared to credit our dumb com-
panions with a single sentiment. A sense of beauty, a
sense of the ludicrous, a sense of justice, and a sense of
right and wrong, — these abstract emotions or sentiments,
as such, are certainly impossible to the brute, if, as I have
contended, he is incapable of isolation and analysis. But,
as we have already seen, even with us these emotions have
to be particularized and brought within the perceptual
sphere ere they are strongly operative on conduct. We
are not roused to indignation by an abstract sense of
injustice, but by the particular performance of an unjust
deed. Even so, however, the emotional state aroused
carries with it in us some of the spirit of the conceptual
sphere from which it has descended. The analogous
emotions in animals cannot possess, if I am right, any
tincture of this conceptual spirit. And since we cannot
divest ourselves of our conceptual spirituality, we cannot
justly estimate what these emotional states, in dog or ape,
are like. Eemembering this, let us eee what can be said
in favour of a perceptual sense of injustice, guilt, the
ludicrous, and the beautiful. In evidence of a sense of
justice, we have the oft-quoted case of the turnspit-dog

404 Animal Life and Intelligence.

reported by Arago the astronomer.* This dog refused,
with bared teeth, to enter out of his turn the drum by the
revolution of which the spit was rotated. M. Arago, for
whom the pullet on the spit was being dressed, requested
that the dog's companion, after turning the spit for a short
time, should be released. Whereupon the dog who had
before been so refractory seemed satisfied that his turn for
drudgery had come, and, entering the wheel of his own
accord, began without hesitation to turn it as usual. Many
will be prepared to maintain that dogs resent unjust
chastisement. A gentleman I met near Eio de Janeiro
possessed a dog whose sensitiveness was such that, after
a reproof, he would leave the house, and sometimes not
return for several days. His owner assured me of his
belief that in such cases the reproof had always been un-
deserved ; and he told me of one definite instance in which
the reproof — never more than verbal — had been for a theft
which was afterwards found to have been committed by his
garden-boy. On this occasion the dog was away for three
days, and returned in a wretched and miserable condition.
What shall we say of such cases ? Seeing how complex is
what we call a sense of justice, I am not prepared to credit
the dog therewith ; and I am disposed to regard such
actions as I have just described as the result of a breach
of normal association. Dogs, like men, are creatures of
habit; and breaches of normal association — occurrences
contrary to expectation — give rise to uneasiness, dissatisfac-
tion, and consequent resentment.

Conversely, many of the cases where dogs and other
animals are said to know when they have done wrong, and
to suffer the pricks of conscience, may probably be satis-
factorily explained by association. When my friend, coming
down into his drawing-room, sees Tim's " guilty " look, he
suspects that the dog has, contrary to rule, been taking a
nap on one of the chairs ; and his suspicions are not a
little strengthened by the unnatural warmth of the easiest
armchair. " Ah ! Tim always knows when he has done

* " Animal Intelligence," p. 443.

Appetence and Emotion. 405

wrong," says my friend. But not improbably the associa-
tion in Tim's mind is a direct one between a nap on that
chair and his master's displeasure. What Tim knows is,
perhaps, not that he has done wrong, but that he will
"catch it." It is the expectation of a reproof, or some-
thing more, that gives rise to his look of conscious guilt.
In the same way, the look of " conscious rectitude " we
often see in some dogs may be due to the anticipation of
a word of commendation. And, in general, I fancy that the
association in an animal's mind is between the perform-
ance of a given act and the occurrence of certain con-
sequences. When this association becomes definite it must,
I imagine, draw after it a dislike of such actions as have
been accompanied by evil consequences, and a delight in
such actions as have been accompanied by pleasant con-
sequences. And eventually this dislike or delight is trans-
ferred from his own actions to the similar actions of others.
Thus dogs punish their puppies for acts of uncleanliness,
while cats are even more particular in this respect. A
correspondent in Nature * gives a case of a cat chastising
by a violent blow with her paw her kitten, who was about
to enjoy a herring which had been set down before the
fire to keep hot. So, too, according to Mr. Darwin,t " when
the baboons in Abyssinia plunder a garden, they silently
follow their leader, and, if an imprudent young animal
makes a noise, he receives a slap from the others to teach
him silence and obedience." And Mr. Schaub com-
municated to Professor Nipher } a case of a black-and-tan
terrier bitch, whose pup had stolen a stocking from his
bedroom, and who followed the young offender, took the
stocking from him, and returned it to the owner. Her
action gave evidence, he says, of displeasure at the action
of the pup. And Mr. Schaub contrived to have the offence
committed on many successive mornings, the same per-
formance being repeated each time.

* Mr. Alexander Mackennal, vol. xxi. p. 397.

f " Descent of Man," pt. i. chap, iii., quoted from Brehm's " Thierleben."

J Nature, vol. xxviii. p. 32.

406 Animal Life and Intelligence.

In this connection I will give two anecdotes of Carlo,
communicated to me by Mrs. Mann. " Once I came upon
Carlo sitting in the dining-room doorway, Dulceline, the
cat, angrily watching him from the stairs, and also
evidently having an eye on a leg of mutton half dragged
off the dish on the dining-table. Carlo had clearly caught
the thief in the act. He was on guard ; and he seemed
much relieved when higher powers came on the scene.
Honesty seemed part of Carlo's nature. In this matter
we never had to give him any lessons. Nor could he bear
to see dishonesty in others. One Sunday, one of the little
girls saw Carlo coming along looking so anxiously at her
that she knew he wanted her to come. She therefore
followed him, and Carlo took her to the store-room, the
door of which her sister had left open. In the doorway
Carlo stopped, and looked first up at his mistress and then
into the store-room, as much as to say, ' What can we
think of this ? ' And truly there was a certain little black-
and-tan terrier, whose principles were by no means of a
high order, regaling himself with some cold meat that he
had dragged on to the floor. Toby knew he was in the
wrong, and tried to flee. But Carlo stopped him as he
endeavoured to fly past. And when Toby was thereupon
duly slapped, Carlo sat straight up, with a face of conscious
rectitude."

These anecdotes, communicated to me by a lady of
culture and intelligence, illustrate how, in describing the
actions of animals, phraseology only, in strictness, applic-
able to the psychology of man, is unwittingly and almost
unavoidably employed. Toby's "principles were not of a
high order," yet he " knew lie icas in the wrong," while Carlo
watched him receive his punishment, and " sat straight up,
with a face of conscious rectitude."

Coming now to a sense of humour or a sense of the
ludicrous, Darwin himself said,* ''Dogs show what may
fairly be called a sense of humour, as distinguished from
mere play ; if a bit of stick or other such object be thrown

* " Descent of Mail," quoted by Romanes, p. 445.

Appetence and Emotion. 407

to one, he will often carry it away for a short distance ; and
then, squatting down with it on the ground close before
him, will wait until his master comes close to take it away.
The dog will seize it and rush away in triumph, repeating
the same manoeuvre, and evidently enjoying the practical
joke." Mr. Eomanes had a dog who used to perform
certain self-taught tricks, "which clearly had the object
of exciting laughter. For instance, while lying on his side
and violently grinning, he would hold one leg in his mouth.
Under such circumstances, nothing pleased him so much
as having his joke duly appreciated, while, if no notice was
taken of him, he would become sulky." To these I may
add an observation of my own. I used sometimes, when
staying at Lancaster with a friend, to take his dog Sambo,
a highly intelligent retriever, to the seashore. His chief
delight there was to bury small crabs in the sand, and then
stand watching till a leg or a claw appeared above the
surface, upon which he would race backwards and forwards,
giving short barks of keen enjoyment. This I saw him do
on many occasions. He always waited till a helpless leg
appeared, and then bounded away as if he could not
contain the canine laughter that was in him. Who shall
say, however, what was passing through the mind of the
dog in any of these three cases ? The motive of Mr.
Darwin's dog may have been to prolong the game, though
I expect there was something more than this. Mr. Romanes's
dog exemplified, perhaps, the sense of satisfaction at being
noticed. Sambo's performance is now, as it was years ago,
beyond me. But a sense of humour, involving a delicate
appreciation of the minor incongruities of life, is, I imagine,
too subtle an emotion for even Sambo.

I pass now to the sense of beauty, and I shall consider
this at greater length, because of its bearing on sexual
selection and the origin of floral beauty.

The interesting experiments of Sir John Lubbock already
alluded to seem to establish the fact that bees have certain
colour-preferences. Blue and pink are the most attractive
colours ; yellow and red are in less favour. No doubt these

408 Animal Life and Intelligence.

preferences have arisen in association with the flowers from
which the bees obtain their nectar. They have a practical
basis of biological value. But there seems no doubt that
certain colours are now for them more attractive than
others. Bees and other insects are, undoubtedly, attracted
by flowers ; these flowers excite in us an esthetic pleasure ;
the bees are, therefore, supposed to be attracted to the
flowers through their possession of an aesthetic sense.
Now, this does not necessarily follow. It is the nectar, not
the beauty of the flower, that attracts the bee. So long as
the flower is sufficiently conspicuous to be rapidly distin-
guished by the insect, the conditions of the case are met
so far as insect psychology is concerned. The fact remains,
however, that the flowers thus conspicuous to the insect
are fraught with beauty for us.

In the case of sexual selection among birds, again, I
believe that the gorgeous plumage has its basis of origin in
that pre-eminent vitality which Mr. Tylor and Mr. Wallace
have insisted on. But, as before indicated, this will not
serve to explain its special character for each several species
of birds. Here, again, conspicuousness and recognition
are unquestionably factors. But that the bright plumage
of male birds awakens emotional states in the hens, that it
probably also arouses sexual appetence, seems to be shown
by the manner in which the finery is displayed by the
male before the female. I think it is probable, also, that
pleasure, becoming thus associated with bright colours in
the mate, is also aroused by bright colours in other asso-
ciations. Thus the gardener bower-bird, described by Dr.
Beccari,* collects in front of its bower flowers and fruits of
bright and varied colours. It removes everything unsightly,
and strews the ground with moss, among which it places
the bright objects from among which the cock bird is said
to select daily gifts for his mate's acceptance ! Dr. Gould
states that certain humming-birds decorate their nests
"with the utmost taste," weaving into their structure
beautiful pieces of flat lichen. If by crediting birds with

* Nature, vol. xl. p. 327.

Appetence and Emotion. 409

a sense of beauty we mean that in them pleasurable
emotions may be aroused on sight of objects which we
regard as beautiful, I am not prepared to deny them such
a sense of beauty, nay, I fully believe that such pleasurable
feelings are aroused in them. When, however, it is said
that the gorgeous plumage of male birds has been produced
by the aesthetic choice of their mates, I am not so ready to
agree. A consciously aesthetic motive has not, I believe,
been a determining cause. The mate selected has been
that which has excited the strongest sexual appetence ; his
beauty has probably not, as such, been distinctly present
to consciousness. Here, then, we have again the question
which arose in conection with floral beauty — How is it
that the sight of the mates selected by hen birds excites in
us, in so many cases, an aesthetic pleasure ?

It is clear that this is a matter rather of human than
of animal or comparative psychology. As such, except for
purposes of illustration, it does not fall within the scope of
this work. I can, therefore, say but a few words on the
subject. The view that I think erroneous is that either
floral beauty or the beauty of secondary sexual characters
has been produced on aesthetic grounds, that is to say, for
the sake of the beauty they are seen by man to possess.
It is, therefore, to the point to 'draw attention to the fact
that many of the objects and scenes which excite in us this
aesthetic sense have certainly not been produced for the
sake of their beauty. Their beauty is an adjunct, a by-
product of rarest excellence, but none the less a by-product.

Nothing can be more beautiful in its way than a well-
grown beech or lime tree; and yet it cannot be held to
have been produced for its beauty's sake. The leaves of
many trees, shrubs, and plants are scarcely less beautiful
than the flowers. But they cannot have been produced by
the aesthetic choice of insects. From the depth of a mine
there may be brought up a specimen of ruby copper ore, or
malachite, or a nest of quartz crystals, or an agate, or a
piece of veined serpentine, which shall be at once pro-
nounced a delight to the eye. But for the eye it was not

4io Animal Life and Intelligence.

evolved. The grandeur of Alpine scenery, the charm of a
winding river, the pleasing undulations of a flowing land-
scape,— no one can say that these were evolved for the
sake of their beauty. The fact of their being beautiful
is, therefore, no proof that the blue gentian, or the red
admiral, or the robin redbreast were evolved for the sake
of, or by means of, the beauty that they possess. Again,
one leading feature in the beauty of flowers is their
symmetry. The beauty is, so to speak, kaleidoscopic
beauty. It is not so much the single veined or marbled
petal that is so lovely, as the group of similar petals
symmetrically arranged. But this symmetry can hardly
be said to have been selected for its aesthetic value; it is
rather part of the natural symmetry of the plant. Even
with butterflies and birds and beasts the symmetrical
element is an important one in their beauty.*

I must not attempt to analzye our sense of beauty or
endeavour to trace its origin. It appears to involve a
pleasurable stimulation of the sense-organs concerned,

* Another example of beauty which can hardly be said to have been
evolved for beauty's sake is to be seen in birds' eggs. Mr. Henry Seebohm
regards the bright colours of some birds' eggs as a difficulty in the way of the
current interpretation of organic nature. " Few eggs," he says (Nature, vol.
xxxv. p. 237), " are more gorgeously coloured [than those of the guillemot],
and no eggs exhibit such a variety of colour. [They are sometimes of a bluish
green, marbled or blotched with full brown or black ; sometimes white streaked
with brown ; sometimes pale green or almost white with only the ghosts of
blotches and streaks ; and sometimes the reddish brown extends so as to
form the ground-tint which is blotched with deeper brown.] It is impossible
to suppose that protective selection can have produced colours so conspicuous
on the white ledges of chalk cliffs ; and sexual selection must have been
equally powerless. It would be too ludicrous a suggestion to suppose that a
cock guillemot fell in love with a plain- coloured hen because he remembered
that last season she laid a gay-coloured egg."

If we connect colour with metabolic changes, its occurrence in association
with the products of the highly vascular oviduct will not be surprising.
Some guidance is, however, on the principles advocated in Chapter VL.required
to maintain a standard of coloration. In many cases such guidance is found
in protective selection, as in the plover's eggs in our frontispiece. In the
guillemot's egg such protective selection seems to be absent, aud, as Mr.
Seebohm himself says, " no eggs exhibit such a variety of colour."

In our present connection, however, the point to be noticed is that many
eggs are undoubtedly beautiful. But they cannot have been in any way
eelected for the sake of their beauty.

Appetence and Emotion. 4 1 1

together with perceptions of symmetry, of diversity and
contrast, and of proportion, with a basis of unity. It is
rich in suggestions and associations. It is heightened by
sympathy. A beautiful scene is doubly enjoyable if a
congenial companion is by our side.

" The whole effect of a beautiful object, so far as we
can explain it," says Mr. Sully,* "is an harmonious con-
fluence of these delights of sense, intellect, and emotion, in
a new combination. Thus a beautiful natural object, as a
noble tree, delights us by its gradations of light and colour,
the combination of variety with symmetry in its contour or
form, the adaptation of part to part, or the whole to its
surroundings ; and, finally, by its effect on the imagination,
its suggestions of heroic persistence, of triumph over the
adverse forces of wind and storm. Similarly, a beautiful
painting delights the eye by supplying a rich variety of
light and shade, of colour, and of outline; gratifies the
intellect by exhibiting a certain plan of composition, the
setting forth of a scene or incident with just the fulness of
detail for agreeable apprehension ; and, lastly, touches the
many-stringed instrument of emotion by an harmonious
impression, the several parts or objects being fitted to
strengthen and deepen the dominant emotional effect,
whether this be grave or pathetic on the one hand, or
light and gay on the other. The effect of beauty, then,
appears to depend on a simultaneous presentment in a
single object of a well-harmonized mass of pleasurable
material or pleasurable stimulus for sense, intellect, and
emotion."

This, too, is what I understand by an aesthetic sense of
beauty ; and if a hen bird has her sexual appetence evoked
by the bright display of her mate, the emotional state she
experiences is something very different from what we know
as a sense of beauty. The adjective " aasthetic " should in
any case, I think, be resolutely excluded in any discussion
of sexual selection.

^Esthetics, like conceptual thought, accompany the sup-

* " Outlines of Psychology," p. 537.

412 Animal Life and Intelligence.

pression or postponement of action. As we have already
seen, the normal and primitive series is (1) sense -stimulus ;
(2) certain nerve-processes in the brain which are asso-
ciated with perception and emotion ; and (3) certain result-
ing activities. By the suppression of action the mind
comes to occupy itself more and more completely with the
central processes. Perception blossoms forth into con-
ceptual thought ; emotion blossoms forth into aesthetics.

" ' Throughout the whole range of sensations, percep-
tions, and emotions which we do not class as aesthetic,' *
says Mr. Herbert Spencer, ' the states of consciousness
serve simply as aids and stimuli to guidance and action.
They are transitory, or, if they persist in consciousness
some time, they do not monopolize the attention ; that
which monopolizes the attention is something ulterior, to
the effecting of which they are instrumental. But in the
states of mind we class as aesthetic the opposite attitude
is maintained towards the sensations, perceptions, and
emotions. These are no longer links in the chain of states
which prompt and guide conduct. Instead of being allowed
to disappear with merely passing recognition, they are kept
in consciousness and dwelt upon, their natures being such
that their continued presence in consciousness is agree-
able.' The action which is the normal consequent on
sensation is here postponed or suppressed; and thus we
are enabled to make knowledge or beauty an end to be
sought for its own sake ; and thus, too, we are able to
make progress, otherwise impossible, in science and in art.
Sensations and perceptions are the roots from which spring
the sturdy trunk of action, the expanded leaves of know-
ledge, and the fair blossoms of art. The leaves and the
flowers are the terminal products along certain lines of
development ; but the function of the leaves is to minister
to the growth of the wood, and the function of the flowers is
to minister to the continuance and well-being of the race.
So, too, in human affairs. Knowledge and art are justified
by their influence on conduct ; truth and beauty must ever

* I should add, "or as conceptual thought."

Appetence and Emotion. 413

guide us towards right living ; and aesthetics are true or
false according as they lead towards a higher or a lower
standard of moral life." *

To sum up, then, concerning this difficult subject, the
following are the propositions on which I would lay stress :
(1) What we term an aesthetic sense of beauty involves a
number of complex perceptual, conceptual, and emotional
elements. (2) The fact that a natural object excites in us
this pleasurable emotion does not carry with it the implica-
tion that the object was evolved for the sake of its beauty.

(3) Even if we grant, as we fairly may, that brightly
coloured flowers, in association with nectar, have been
objects of appetence to insects ; and that brilliant plumage,
in association with sexual vigour, has been a factor in the
preferential mating of birds ; — this is a very different thing
from saying that, either in the selection of flowers by
insects, or in the selection of their mates by birds, a con-
sciously aesthetic motive has been a determining cause.

(4) In fine, though animals may be incidentally attracted
by beautiful objects, they have no aesthetic sense of beauty.
A sense of beauty is an abstract emotion. Esthetics in-
volve ideals ; and to ideals, if what has been urged in these
pages be valid, no brute can aspire.

What applies thus to aesthetics applies also to ethics.
Few, however, will be found to contend that animals can be
moral or immoral, or have any moral ideas properly so called.
Mr. Eomanes does indeed state, in the table he prefixes
to his works on Mental Evolution, that the anthropoid
apes and dogs are capable of "indefinite morality." He
leaves this to be explained, however, in a future work. In
the published instalment of " Mental Evolution in Man "
he seems to contend,! or, at least, admit, " that the funda-
mental concepts of morality are of later origin than the
names by which they have been baptized." But he says
nothing of indefinite morality, which still remains for con-

* This paragraph is quoted from the author's " Springs of Conduct," p. 263.
t Page 347.

414 Animal Life and Intelligence.

sideration in another work. In the mean while we may,
I think, confidently assume that ethics, like conceptual
thought and aesthetics, are beyond the reach of the brute.
Morality is essentially a matter of ideals, and these belong
to the conceptual sphere.

I have now said enough * to indicate what I mean by
advocating the exercise of extreme caution in our inferences
concerning the emotional states of animals. We must
remember, first, how liable to error are our inferences in
these matters ; we must remember, next, how complex and
essentially human are our own emotions. I do not for one
moment deny that in animals are to be found the perceptual
germs of even the higher emotional states. Nevertheless,
if we employ, in our interpretation of the actions of animals,
such terms as " consciousness of guilt," " sense of right
and wrong," "idea of justice," " deceitfulness," "revenge,"
" vindictiveness," "shame," and the rest, we must not
forget that these terms stand for human products, that they
are saturated with conceptual thought, and that they must
be to a large extent emptied of their meaning before they
can become applicable to the emotional consciousness of
brutes.

* I have said nothing about the emotions of invertebrates, because I have
nothing special to say. They have, no doubt, emotions analogous to fear,
anger, and so on. But it is difficult to interpret their actions. The " angry "
wasp is, perhaps, a good deal more frightened than furious. Sir John
Lubbock's interesting experiments seem to show that ants have what is
termed the instinct of play. But this admirable observer has rendered it
probable that sympathy and affection in ants and bees have been somewhat
exaggerated.

CHAPTEE XL
ANIMAL ACTIVITIES: HABIT AND INSTINCT.

So soon as one of the higher animals comes into the world
a number of simple vital activities are already in progress
or are at once initiated. Some of these are what are
termed " automatic actions," or actions which take their
origin within the organ which manifests the activity;
such are the heart-beat and the rhythmical contractions
of the intestines by which the food is pushed onwards
through the alimentary canal. Some are reflex, or
responsive, actions, taking origin from a stimulus coming
from without ; such are the contraction of the pupil of the
eye under bright light, the pouring forth of the secretions
on the presence of food in the alimentary canal, taking the
breast, sneezing, and so forth. Some are partly automatic
and partly reflex ; such is the rhythm of respiration.

In addition to these vital activities, there is a vast body
of more complex activities, for the performance of which
the animal brings with it innate capacities. Some of
these, which we term "instinctive," are performed at once
and without any individual training, as when a chicken steps
out into the world, runs about, and picks up food without
learning or practice. Others, which we term "habitual,"
are more or less rapidly learnt, and are then performed
without forethought or attention. The store of innate
capacity is often very large ; and a multitude of activities
are ere long performed with ease and certainty so soon as
the animal has learnt to use the organization it thus
inherits. And lastly, built upon this as a basis, by recom-
biiiing of old activities in new modes, and by special applica-

4i 6 Animal Life and Intelligence.

tion of the activities to special circumstances, we have the
activities which we term " intelligent ; " and here again the
activities are sometimes divided into two classes, answering
respectively to the reflex and the automatic, but on a
higher plane, according as they are responsive to stimuli
coming more or less directly from without, or spontaneous
and taking their origin from within. But it is probably
rather the remoteness and indirectness of the responsive
element than its absence that characterizes these spon-
taneous activities.

Another classification of activities is into voluntary and
involuntary. Voluntary actions are consciously performed
for the attainment of some more or less definite end or
object. Involuntary actions, though they may be accom-
panied by consciousness, and though they may be apparently
purposive, are performed without intention. Notwith-
standing the conscious element, they may, perhaps, be
regarded as rather physiological than psychological. The
simple vital activities belong to this class. But some are
much more complex. If, when I am watching the cobra at
the Zoo, it suddenly strikes at the glass near my face, I
involuntarily start back. The action is apparently pur-
posive, that is to say, an observer of the action would
perceive that it was performed for a definite end, the
removal from danger ; it is also accompanied by conscious-
ness ; but it is unintentional, no representation of the end
to be gained or the action to be performed being at the
moment of action framed by the mind. On the other
hand, if I perform a voluntary act, such as selecting and
lighting a cigar, there is first a desire or motive directed
to a certain end in view, involving an ill-defined representa-
tion of the means by which that end may be achieved ;
and this is followed by the fulfilment of the desire through
the application of the means to the performance of the act.

In the carrying out of voluntary activities, then, both
perception and emotional appetence are involved. There
are construction and reconstruction, memory and antici-
pation, and interwoven therewith the motive elements of

Habit and Instinct. 4 1 7

appetence or aversion. It is emotion that gives force and
power to the motive. And this must be regarded as the
dynamic element in voluntary activity, while intelligence
is the directive element. Feeling is the horse in the
carriage of life, and Intelligence the coachman.

Let us here note that, in speaking of the activities of
animals and the motives by which they are prompted, we
are forced, if we would avoid pedantry, to leap backwards
and forwards across the chasm which separates the mental
from the physical. Motives, as we know them, are mental
phenomena; the activities, as we see them, are physical
phenomena. The two sets of phenomena belong to distinct
phenomenal categories. In ordinary speech, when we pass
and repass from motives to actions, and from actions to
the feelings they may give rise to, we are apt to be forgetful
of the depth of the chasm we so lightly leap. And this is
no doubt because the, chasm, though so infinitely deep, is
so infinitely narrow. There are, however, no physical
analogies by which we can explain the connection between
the physical and the mental, between body and mind.
The so-called connection is, in reality, as I believe, identity.
Viewed from without, we have a series of physical and
physiological phenomena ; felt from within, we have a
series of mental and psychological phenomena. It is the
same series viewed from different aspects. This is no
explanation ; it is merely a way, and, as I believe, the
correct way, of stating the facts. Why certain physiological
phenomena should have a totally different aspect to the
organism in which they occur from that which they offer
to one who watches them from without, is a question which
I hold to be insoluble. All we have to remember, however,
is that, in passing from the mental to the physical, we are
changing our point of view. The series may be set down
thus —

External aspect : Physical stimulus ^>aterneural processes — ^ actiyities.
Inner aspect: Accompanying consciousfJRT^- mental states — ^ accompany-
ing consciousness.

The physical stimulus and the resulting activities are

2E

418 Animal Life and Intelligence.

occurrences in the external world, and more or less lie
open to our view. But the intervening physical and
physiological neural processes are hidden from us. As
occurring in ourselves, however, tthe mental states which
are the inner aspects of these neural processes stand out
clearly in the light of consciousness. When, therefore, we
are watching the life-activities of others, we naturally fill
in between the physical stimulus and the activities, not the
neural processes of which we are so ignorant, but mental
states analogous to those of which we are conscious under
similar conditions. Thus we leap from the physical to the
mental, and back again to the physical, as represented by
the diagonal lines in the above scheme. And there can be
no objection to our doing so if we bear in mind that we
are thus changing our point of view.

The human organism, then — for at present we may
regard the matter from man's own position — is a wonder-
fully delicate piece of organization, with mental (inner)
and physical (outer) aspects. It is in a condition of the
most delicate equipoise. Under the influence of a percep-
tion associated with an appetence, or of a conception
accompanied by a desire, it is thrown into a state of
unstable equilibrium ; the performance of the action which
leads to the fulfilment or satisfaction of the appetence or
the desire restores the stability of the system. The in-
stability is caused by the conjoint action of an attraction
towards some state represented as desirable, and a repul-
sion from the existing state which is relatively undesirable.
In some cases the attraction, and in others the repulsion, is
predominant. When we are -in an uncomfortable position,
the discomfort is predominant, and we seek relief by
changing our attitude. When the bright sunshine tempts
us to go out for a walk, the attraction is predominant. But
if the uncomfortable attitude is enforced and prolonged, we
have a mental representation of the relief we long for ; and
this is attractive. And if we have work which keeps us
indoors, the irksome restraint brings with it an aversion to
our present lot.

Habit and Instinct. 419

Inseparably associated with the appetence or aversion
there is a representation of the activity which constitutes
the fulfilment of the emotion. On the physiological side
this is probably an incipient excitation of the muscles or
other organs concerned in the requisite actions. The
miser's fingers itch to clutch the gold, the possession of
which he desires. Our muscles twitch as we long to join
in the race or the active contention of a game of football.
Our horse grows restive as the hunt goes by. Our dog can
scarce restrain himself from racing after the rabbits in the
park. Under the influence of emotion, then, the body is
prepared for activity, the organs and muscles are beginning
to be innervated, and, if the appetence or desire be
sufficiently strong, the appropriate actions are initiated,
and the organism tends to pass from the state of unstable
equilibrium arising out of a pressing need to the stable
condition of satisfied appetence. The function of the will
in this process we shall have briefly to consider presently.

Let us here notice, with regard to the activities, what
we have before seen with regard to the process of perceptual
construction. We there noticed that, at the bidding of a
relatively simple suggestion, a complex object may be con-
structed by the mind. This presupposes a highly com-
plex mental organization ready to be set in motion by the
appropriate stimulus. The organization has been. estab-
lished by association and through evolution in the indi-
vidual and his ancestors. It is the same with the activities.
They, too, are the outcomes of associations and experiences
established and registered during generations of ancestral
predecessors. At the bidding of the appropriate stimulus
arousing impulse or appetence, a train of activities of great
intricacy may be set agoing with remarkable accuracy and
precision. It is true that a certain amount of individual
education is required to draw out and establish the latent
powers of the body, as also of the mind ; but the ability is
inborn, and only requires to be cultivated. Every one of
us inherits an organization rendering him capable of per-
forming a vast amount of mental construction and a great

42b Animal Life and Intelligence.

number of bodily activities. All he has to do is to learn
how to use it and to make himself master of the powers
that are given him.

At first, the acquisition of this mastery over the innate
powers, even in the performance of comparatively simple
muscular adjustments, may require a good deal of attention
and practice. But, as time goes on, the frequent repetition
of the ordinary activities of everyday life leads to their
easier and easier performance. In simple responsive
actions the appropriate activity follows readily on the
appropriate stimulus. And, ere long, many acts which at
first required intelligent attention are performed easily
and without consciousness of effort or definite intention.
A close association between certain oft-recurring stimuli
and. the appropriate response in activity is thus established,
and the action follows on the stimulus without hesitation or
trouble. With fuller experience and further practice in the
ordinary avocations of life, the responsive activities link
themselves more and more closely in association, become
more and more complex, are combined in series and classes
of activity of greater length and accuracy, and thus become
organized into habits. Under this head fall those activities
which we learn with difficulty in childhood, and perform
with ease in after-life. At first voluntary and intentional,
they have become, or are becoming, through frequency
and uniformity of performance, more or less involuntary
and unintentional.

" The work of the world is," we are told, " for the most
part done by people of whom nobody ever hears. The
political machine and the social machine are under the
ostensible control of personages who are well to the front ;
but these brilliant beings would be sorely perplexed, and
the machinery would soon come to a standstill, but for
certain experienced, unambitious, and unobtrusive members
of society." So is it also in the economy of animal life.
The work of life is — to paraphrase Mr. Norris's words — for
the most part done by habits of which nobody ever thinks.
The bodily organization is ostensibly under the control of

Habit and Instinct. 421

intellect and reason ; but these brilliant qualities would be
sorely perplexed, and the machinery would soon come to a
standstill, but for certain unobtrusive, habitual activities
which are already as well trained in the routine work of
life as are the permanent clerks in the routine work of a
Government office.

The importance of the establishment of these habitual
activities is immense. As the muscular and other re-
sponses of ordinary everyday life become habitual, the
mind is, so to speak, set free from any special care with
regard to their regulation and co-ordination, and can be
concentrated on the end to be attained by such activities.
The cat that is creeping stealthily upon the bird has all
her attention ri vetted on the object of her appetence, and
has not to trouble herself about the movements of her
body and limbs. When the swallows are wheeling over
our heads in the summer air, their sweeping curves and
graceful evolutions are not the outcome of careful planning,
but are just the normal exercise of activities which from
long practice have become habitual. To swim, to skate,
to cycle, to row, to play the piano^ or the violin, — all these
require our full attention at first. But with practice they
become habitual, and during their performance the atten-
tion may be devoted to quite other matters. This is a
great gain. Without it complex trains of activities could
not be performed with ease by man or beast.

When once habits have been firmly established, their
normal performance is accompanied by a sense of satisfac-
tion. But if their performance is prevented or thwarted,
there arises a sense of want or dissatisfaction. The pining
of a caged wild animal for liberty is a craving for the free
performance of its habitual activities. In an animal born
into captivity the craving is probably less intense, though,
for reasons which will presently become evident, it is
presumably by no means absent. Animals are, to a very
large extent, creatures of habit. Much of the pleasure of
their existence lies in the performance of habitual activities.
Our zoological gardens, interesting as they are to us, are

422 Animal Life and Intelligence.

probably centres of an amount of misery and discomfort,
from unfulfilled promptings of habit and instinct, which
we can hardly realize.

From habitual activities we may pass by easy steps to
those which are instinctive. Both habits and instincts,
or, to use a more convenient and satisfactory mode of
expression for our present purpose, both habitual and
instinctive activities, are based upon innate capacity. But
whereas habitual activities always require some learning
and practice, and very often some intelligence, on the part
of the individual, instinctive activities are performed with-
out instruction or training, through the exercise of no
intelligent adaptation on the part of the performer, and
either at once and without practice (perfect instincts) or
by self-suggested trial and practice (incomplete instincts).*

There is some little difficulty in distinguishing between
instinctive activities and reflex actions. Mr. Herbert
Spencer defines or describes instinct as compound reflex
action. Mr. Komanes defines instinct as reflex action
into which there is imported the element of consciousness.
But, on the one hand, many instincts involve something
more than compound reflex action, since there is an
organized sequence of activities ; and, on the other hand,
the difficulty (which Mr. Romanes admits) or impossibility
(as I contend) of applying the criterion of consciousness
renders unsatisfactory the introduction of the mental
element as distinctive. I would say, therefore, that (1)
reflex actions are those comparatively isolated activities
which are of the nature of organic or physiological re-
sponses to more or less definite stimuli, and which involve
rather the several organs of the organism than the activities
of the organism as a whole; and that (2) instinctive
activities are those organized trains or sequences of co-
ordinated activities which are performed by the individual

* I use the term " incomplete," and not "imperfect," because Mr. Romanes,
in his admirable discussion of the subject, applies the term "imperfect
instinct " to cases where the instinct is not perfectly adapted to the end in
view (see "Mental Evolution in Animals," p. 167).

Habit and Instinct. 423

in common with all the members of the same more or less
restricted group, in adaptation to certain circumstances,
oft-recurring or essential to the continuance of the species.

These instinctive activities may, as I have said, be per-
formed at once and without practice (perfect instincts) or
by self -suggested trial and practice (incomplete instincts).
Most young mammals require some little practice in the
use of their limbs before they are able to walk or run.
But young pigs run about instinctively so soon as they are
born. Thunberg, the South African traveller, relates, on
the testimony of an experienced hunter, the case of a
female hippopotamus which was shot the moment she had
given birth to a calf. " The Hottentots," he said, " who
imagined that after this they could catch the calf alive,
immediately rushed out of their hiding-place to lay hold of
it ; but, though there were several of them, the new-born
calf got away from them, and at once made the best of its
way to the river."

Even in cases where some practice is apparently neces-
sary, the activities may be, and often are, perfectly in-
stinctive. They cannot, however, be performed immediately
on birth, because the nervous and muscular mechanism
is not at that time sufficiently developed. They might,
perhaps, with advantage be termed "deferred instincts."
If time be given for this development, the activities are
carried out at once and without practice. Throw a new-
born puppy into the river, and, after some helpless
floundering, he will be drowned. Throw his brother when
fully grown into the river, and, though he may never have
been in the water in his life, he will swim to shore. He
has not to learn to swim ; this is with him an instinctive
activity. The dog inherits the power which the boy must
with some little difficulty acquire. He probably has to
pay no special attention to the muscular adjustments
involved. The act is accompanied by consciousness, but
not that directed consciousness we call " attention." When
the boy has acquired the habit, he is scarcely conscious of
the special muscular co-ordinations as he swims across the

424 Animal Life and Intelligence.

river ; he is only conscious of a desire to pick the water-
lilies near the further bank.

Birds, especially those which are called proecoces, in
contradistinction from the altrices, which are hatched in a
helpless, callow condition, come into the world prepared at
once to perform complex activities. Mr. Spalding writes,*
" A chicken that had been made the subject of experiments
on hearing [having been blindfolded at birth] was un-
hooded when nearly three days old. For six minutes it
sat chirping and looking about it ; at the end of that time
it followed with its head and eyes the movements of a fly
twelve, inches distant; at ten minutes it made a peck at
its own toes, and the next instant it made a vigorous dart
at the fly, which had come within reach of its neck, and
seized and swallowed it at the first stroke ; for seven
minutes more it sat calling and looking about it, when a
hive-bee, coming sufficiently near, was seized at a dart,
and thrown some distance much disabled. For twenty
minutes it sat on the spot where its eyes had been unveiled
without attempting to walk a step. It was then placed on
rough ground, within sight and call of a hen with a brood
of its own age. After standing chirping for about a minute,
it started off towards the hen, displaying as keen a percep-
tion of the qualities of the outer world as it was ever likely
to possess in after-life. It never required to knock its
head against a stone to discover that there was ' no road
that way.' It leaped over the smaller obstacles that lay in
its path, and ran round the larger, reaching the mother in
as nearly straight a line as the nature of the ground would
permit. This, let it be remembered, was the first time it
had ever walked by sight. "f

Mr. Spalding's experiments also proved that, even

* Macmillan's Magazine, February, 1873. Professor Eimer, in his " Organic
Evolution" (English translation, p. 245), narrates similar experiences.

t Mr. W. Larden states, in Nature (vol. xlii.), that his brother extracted,
from the oviduct of a Vivora de la Cruz snake in the West Indies, two young
snakelets six inches long. Both, though thus from their mother's oviduct
untimely ripped, threatened to strike, and made the burring noise with the
tail, characteristic of the snake.

Habit and Instinct. 425

among the altrices, young birds do not require to be taught
to fly, but fly instinctively so soon as the bodily organiza-
tion is sufficiently developed to render this activity possible.
He kept young swallows caged until they were fully fledged,
and then allowed them to escape. They flew straight off
at the first attempt. They exhibited the instinctive power
of flight in a perfect but deferred form.

It is, however, among the higher invertebrates — •
especially among the insects, and of them pre-eminently
in the social hymenoptera, ants and bees, that the most
remarkable and complete instincts are seen. There is,
however, a tendency to ascribe all the habits of ants and
bees to instinct, often, as it seems to me, without sufficient
evidence that they are performed without instruction, and
through no imitation or intelligent adjustment. This is,
perhaps, a survival of the old-fashioned view that all the
mental activities of the lower animals are performed from
instinct, whereas all the activities of human beings are to
be regarded as rational or intelligent. In popular writings
and lectures, for example, we frequently find some or all of
the following activities of ant-life ascribed to instinct :
recognition of members of the same nest ; powers of com-
munication; keeping aphides for the sake of their sweet
secretion ; collection of aphid eggs in October, hatching
them out in the nest, and taking them in the spring to the
daisies, on which they feed, for pasture ; slave-making and
slave-keeping, which, in some cases, is so ancient a habit
that the enslavers are unable even to feed themselves ;
keeping insects as beasts of burden, e.g. a kind of plant-bug
to carry leaves ; keeping beetles, etc., as domestic pets ;
habits of personal cleanliness, one ant giving another a
brush-up, and being brushed-up in return ; habits of play
and recreation ; habits of burying the. dead; the storage of
grain and nipping the budding rootlet to prevent further
germination ; the habits described by Dr. Lincecum, and
to a large extent confirmed by Dr. McCook,* that Texan

* Dr. McCook confirms the observation that the clearings are kept clean,
that the ant-rice alone is permitted to grow on them, and that the produce of

426 Animal Life and Intelligence.

ants go forth into the prairie to seek for the seeds of a kind
of grass of which they are particularly fond, and that they
take these seeds to a clearing which they have prepared,
and then sow them for the purpose, six months afterwards,
of reaping the grain which is the produce of their agricul-
ture ; the collection by other ants of grass to form a kind
of soil on which there subsequently grows a species of
fungus upon which they feed ; the military organization of
the ecitons of Central America ; and so forth. Now, the
description of the habits of ants forms one of the most
interesting chapters in natural history. But to lump them
together in this way, as illustrations of instinct, is a survival
of an old-fashioned method of treatment. That they have
to a very large extent an innate basis may be readily
admitted. But at present we are hardly in a position to
say how far they are instinctive, that is, performed by each
individual straight off, and without imitation, instruction,
or intelligence ; how far habitual, that is, performed after
some little training and practice ; how far there is the
intelligent element of special adaptation to special circum-
stances ; how far they are the result of imitation ; to what
extent, if any, individual training and instruction are factors
in the process.

To''put the matter in another way. Suppose that an
intelligent ant were to make observations on human
activities as displayed in one of our great ' cities or in an
agricultural district. Seeing so great an amount of routine
work going on around him, might he not be in danger of
regarding all this as evidence of blind instinct ? Might he
not find it difficult to obtain satisfactory evidence of the
establishment of our habits, of the fact that this routine
work has to some extent to be learnt ? Might he not say
(perhaps not wholly without truth), "I can see nothing
whatever in the training of the children of these men to fit
them for their life-activities. The training of their children

this crop is carefully harvested ; but he thinks that the ant-rice sows itself,
and is not actually planted by the ants (see Sir John Lubbock's " Scientific
Lectures," 2nd edit., p. 112). ;

Habit and Instinct. 427

has no more apparent bearing upon the activities of their
after-life than the feeding of our grubs has on the duties of
ant-life. And although we must remember," he might
continue, "that these large animals do not have the
advantage which we possess of awaking suddenly, as by a
new birth, to their full faculties, still, as they grow older,
now one and now another of their instinctive activities are
unfolded and manifested. They fall into the routine of life
with little or no training as the period proper to the various
instincts arrives. If learning thereof there be, it has at
present escaped our observation. And such intelligence as
their activities evince (and many of them do show remark-
able adaptation to uniform conditions of life) would seem
to be rather ancestral than of the present time ; as is
shown by the fact that many of the adaptations are directed
rather to past conditions of life than to those which now
hold good. In the presence of new emergencies to which
their instincts have not fitted them, these poor men are
often completely at a loss. We cannot but conclude, there-
fore, that, although shown under somewhat different and
less favourable conditions, instinct occupies fully as large
a space in the psychology of man as it does in that of the
ant, while their intelligence is far less unerring and, there-
fore, markedly inferior to our own."

Of course, the views here attributed to the ant are very
absurd. But are they much more absurd than the views
of those who, on the evidence which we at present possess,
attribute all the varied activities of ant-life to instinct ?
Take the case of the ecitons, or military ants, or the
harvesting ants, or the ants that keep draught-bugs as
beasts of burden : have we sufficient evidence to enable
us to affirm that these activities are purely instinctive and
not habitual ? That they are to a large extent innate, few
are likely to deny ; but then our own habitual acts have a
basis that is, to a very large extent, innate. The question
is not whether they have an innate basis, but whether
all the varied manoeuvres of the military ants, for example,
are displayed to the full without any learning or imitation,

428 .Animal Life and Intelligence.

without teaching and without intelligence on the part of
every individual in the army.*

That in some cases there is something very like a train-
ing or education of the ant when it emerges from the pupa
condition is rendered probable by the observations of
M. Forel. As Mr. Eomanes says,t " The young ant does
not appear to come into the world with a full instinctive
knowledge of all its duties as a member of a social com-
munity. It is led about the nest and ' trained to a know-
ledge of domestic duties, especially in the case of larvae.'
Later on, the young ants are taught to distinguish between
friends and foes. When an ants' nest is attacked by
foreign ants, the young ones never join in the fight, but
confine themselves to removing the pupse; and that the
knowledge of hereditary enemies is not wholly instinctive
in ants is proved by the following experiment, which we
owe to Forel. He put young ants belonging to three
different species into a glass case with pupae of six other
species — all the species being naturally hostile to one
another. The young ants did not quarrel, but worked
together to tend the pupae. When the latter hatched out,
an artificial colony was formed of a number of naturally
hostile species, all living together after the manner of the
* happy families ' of the showmen."

I have said that the varied activities of ants, though
they may not in all cases be truly instinctive, are never-
theless the outcome of certain innate capacities. It seems
to me necessary to distinguish carefully between innate

* The experiments, both of Sir John Lubbock and Mr. Komanes, show
that the homing instinct of bees is largely the result of individual obser-
vation. Taken to the seashore at no great distance from the hive, where
the objects around them, however, were unfamiliar (since the seashore is not
the place were flowers and nectar are to be found), the ,bees were nonplussed
and lost their way. Similarly, the migration of birds " is now," according to
Mr. Wallace, "well ascertained to be effected by means of vision, long flights
being made on bright moonlight nights, when the birds fly very high, while
on cloudy nights they fly low, and then often lose their way" ("Darwinism,"
p. 442). This, of course, does not explain the migratory instinct — the internal
prompting to migrate — but it indicates that the carrying out of the migratory
impulse is, in part at least, intelligent.

t " Auimal Intelligence," p. 59.

Habit and Instinct. 429

capacity and instinct. Every animal comes into the world
with an innate capacity to perform the activities which
have been necessary for the maintenance of the normal
existence of its ancestors. This is part of its inherited
organization. Only when these activities are performed at
the bidding of impulse, through no instruction and from
no tendency to imitation, can they, strictly speaking, be
termed instinctive. The more uniform the conditions of
ancestral life, and the more highly developed the organism
when it enters upon the scene of active existence, the more
likely are the innate capacities to manifest themselves at
once and without training as perfect instincts. Among
birds, the prcecoces, which reach a high state of develop-
ment within the egg, and among insects, those which
undergo complete metamorphosis, and emerge from the
pupa or chrysalis condition fully formed and fully equipped
for life, display the greatest tendency to exhibit activities
which are truly and perfectly instinctive. But man, whose
ancestors have lived and worked under such complex con-
ditions, and who comes into the world in so helpless and
immature a state, though his innate capacities are
enormous, exhibits but few and rudimentary instincts.

One marked characteristic of many of the habits and
instincts of the lower animals is the large amount of blind
prevision (if one may be allowed the expression) which
they display. By blind prevision I mean that preparation
for the future which, if performed through intelligence or
reason, we should term " foresight," but which, since it is
performed prior to any individual experience of the results,
is done, we must suppose, in blind obedience to the internal
impulse. The sphex, a kind of wasp-like insect, forms a
little mud chamber in which she lays her eggs. She goes
forth, finds a spider, stings it in such a way that it is
paralyzed but not killed, and places it in the chamber for
her unborn young, which she will never see. The hen
incubates her eggs, though she may never have seen a
chicken in her life. The caterpillars of an African moth
weave a collective cocoon as large as a melon. All unite

430 Animal Life and Intelligence.

to weave the enveloping husk; each forms its separate
cocoon within the shell, and all these separate cocoons are
arranged round branch-passages or corridors, by which the
moths, when they emerge from the chrysalis condition,
may escape. Another caterpillar, that of a butterfly
(Thekla) feeds within the pomegranate, but with silken
threads attaches the fruit to the branch of the tree, lest,
when withered, it should fall before the metamorphosis is
complete. An ichneumon fly, mentioned by Kirby and
Spence, " deposits its eggs in the body of a larva hidden
between the scales of a fir-cone, which it can never have
seen, and yet knows where to seek; " and thus provision is
made for young which it will never know. Instances of
such blind prevision might be quoted by the score. It is
idle to speculate as to the accompaniments of consciousness
of such acts. If it be asked — May there not be associated
with the performance of the instinctive activity of incuba-
tion an inherited memory of a generalized chick ? we can
only answer that we do not know, but that we guess not.*

There is, however, one association, in the case of these
and other instincts, which we may fairly surmise to be
frequent, though, for reasons to be specified hereafter, it is
probably not invariable. Just as we saw to be the case
with habits, so too with instinctive activities, their per-
formance is not infrequently associated with pleasurable
feeling, their non-performance with pain and discomfort
and a sense of craving or want. The animal prevented
from performing its instinctive activities is often apparently
unquiet, uneasy, and distressed. Hence I said that the
animals in our zoological gardens, even if born and reared
in captivity, may exhibit a craving for freedom and a
yearning to perform their instinctive activities. This
craving may be regarded as a blind and vague impulse,
prompting the animal to perform those activities which are
for its own good and for the good of the race to which it
belongs. The satisfaction of the craving, the gratification

* The American expression, " I guess," is often far truer to fact than its
English equivalent, " I think."

Habit and Instinct. 431

of the blind impulse, is accompanied by a feeling of relief
and ease. Thus where a motive emerges at all into con-
sciousness, that from which we may presume that instinctive
activities are performed is not any foreknowledge of their
end and purpose, but the gratification of an immediate
and pressing need, the satisfaction of a felt want.

We have, so far, been concerned merely with the
various kinds of activity presented by men and animals,
and with some of their characteristics. The organism, in
virtue of its organization, has an inherited groundwork of
innate capacity. Surrounding circumstances and commerce
with the world draw out and develop the activities which
the innate capacity renders possible. First, there are
automatic and reflex actions, which are comparatively
isolated activities in response to definite stimuli, external
or internal. Secondly, there are those organized trains or
sequences of co-ordinated activities which are performed
by the individual in common with all the members of the
same more or less restricted group, in adaptation to certain
circumstances, oft-recurring or essential to the continuance
of the species. These are the instinctive activities. But
no hard-and-fast line can be drawn between them and
reflex actions. The instinctive activities may be either
perfect or relatively imperfect, according to the accuracy
of their adaptation to the purpose for which the activity is
performed ; but in either case they are carried out without
learning or practice. In some cases, however, they cannot
be performed until the organization is more perfectly
developed than it is at birth ; but when the proper time
arrives they are perfect, and require no practice; these
may be termed " deferred instincts." Where some practice,
but only a little, is required, the instinctive activities may
be regarded as incomplete ; and these pass into those
activities which require at first a good deal of practice,
learning, and attention, but eventually run off smoothly
and without special attention, at times almost or quite
unconsciously. These are habitual activities. Finally,

432 Animal Life and Intelligence.

we have those activities which are performed in special
adaptation to special circumstances. These are intelligent
activities.

All of these may be, and the last, the intelligent actions,
invariably are, accompanied by consciousness. The habitual
activities, and those which are incompletely instinctive, are
also, we may presume, accompanied by consciousness
during the process of their organization and establishment.
It is possible, however, that some of the perfectly instinctive
activities may be performed unconsciously. When we
consider how perfectly organized such activities are, and
when we also remember that perfectly organized habitual
activities are frequently in us unconscious, we shall see
cause for suspecting that instinctive activities may, at any
rate in some cases, be unconscious. No doubt the con-
ditions of consciousness are not well understood. But let
us accept Mr. Eomanes's suggestion, that a physiological
concomitant is ganglionic delay. " Now what," he asks,*
" does this greater consumption of time imply ? It clearly
implies," he answers, " that the nervous mechanism con-
cerned has not been fully habituated to the performance of
the response required, and therefore that, instead of the
stimulus merely needing to touch the trigger of a ready-
formed apparatus of response (however complex this may
be), it has to give rise in the nerve-centre to a play of
stimuli before the appropriate response is yielded. In the
higher planes of conscious life this play of stimuli in the
presence of difficult circumstances is known as indecision ;
but even in a simple act of consciousness — such as signalling
a perception — more time is required by the cerebral
hemispheres in supplying an appropriate response to a
non-habitual experience, than is required by the lower
nerve-centres for performing the most complicated of reflex
actions by way of response to their habitual experience.
In the latter case the routes of nervous discharge have
been well worn by use; in the former case these routes
have to be determined by a complex play of forces amid

* " Mental Evolution in Animals," pp. 73, 74.

Habit and Instinct. 433

the cells and fibres of the cerebral hemispheres. And this
complex play of forces, which finds its physiological ex-
pression in a lengthening of the time of latency, finds also
a psychological expression in the rise of consciousness."
Now, since in many instinctive activities the stimulus
" merely needs to touch the trigger of a ready-formed
apparatus of response," I think that they may be uncon-
scious. And Mr. Eomanes thus himself supplies the
reason for rejecting his own definition of instinct as "reflex
action into which there is imported the element of con-
sciousness." Of course, logically, Mr. Eomanes can reply,
"It is merely a question of where we draw the line ; if the
activity is unconscious, it is a reflex action ; if conscious,
it is an instinct." I think this unsatisfactory, (1) because
the criterion of consciousness, from its purely inferential
nature, is practically impossible of application with
accuracy ; (2) because the same series of activities may
probably at one time be unconscious and at another time
conscious ; and (3) because many actions which are almost
universally regarded as reflex actions may at times be
accompanied by consciousness, and would then have, on
Mr. Eomanes's view, to be regarded as instincts.

Having made this initial criticism, I may now state
that I regard Mr. Eomanes's treatment of instinct as most
admirable and masterly. Building upon the foundation
laid by Charles Darwin, he has worked out the theory of
instinct in a manner at once broad and yet minute, lucid
and yet close, definite in doctrine and yet not blind to
difficulties. If I say that it is a piece of work worthy of
the great master whose devoted disciple Mr. Eomanes has
proved himself, I am according it the highest praise in my
power. I have ventured in this volume to criticize some
of Mr. Eomanes's conclusions in the field of animal in-
telligence. And lest I should seem to undervalue his
work, lest our few divergences should seem to hide our
many parallelisms, I take this opportunity of testifying
to my great and sincere admiration of the results of
his careful and exact observations, his patient and thought-

2F

434 Animal Life and Intelligence.

ful inferences, and his lucid and often luminous expo-
sition.

I do not propose to go over the ground so exhaustively
covered by Mr. Romanes in his discussion of instinct. I
shall first endeavour shortly to set forth his conclusions,
and then review the suhject in the light of modern views of
heredity.

Admitting that some instincts may have arisen from
the growth, extension, and co-ordination of reflex actions,
Mr. Romanes regards the majority of instincts as of two-
fold origin — first, from the natural selection of fortuitous
unintelligent activities which chanced to be profitable to
the agent (primary instincts) ; and, secondly, from the
inheritance of habitual activities intelligently acquired.
These are the secondary instincts, comprising activities
which have become instinctive through lapsed intelligence.
In illustration of primary instincts, Mr. Romanes cites the
instinct of incubation. "It is quite impossible," he says,*
"that any animal can ever have kept its eggs warm with
the intelligent purpose of hatching out their contents, so
that we can only suppose that the incubating instinct began
by warm-blooded animals showing that kind of attention to
their eggs which we find to be frequently shown by cold-
blooded animals. . . . Those individuals which most con-
stantly cuddled or brooded over their eggs would, other
things equal, have been most successful in rearing progeny ;
and so the incubating instinct would be developed without
there ever having been any intelligence in the matter."

Many of the instincts which exhibit what I have termed
above "blind prevision" must, it would seem, belong
completely or in the main to this class. The instincts of
female insects, which lead them to anticipate by blind
prevision the wants of offspring they will never see ; the
instincts of the caterpillars, which lead them to make pro-
vision for the chrysalis or imago condition of which they
can have no experience ; the instinct of a copepod
crustacean, which lays its eggs in a brittle-star, that they

* "Mental Evolution in Animals," p. 177.

Habit and Instinct. 435

may therein develop, probably in the brood- sac, and may
even destroy the reproductive powers of the host for the
future good of her own offspring — these and many others
would seem to have no basis in individual experience.

In illustration of the second class of instincts, those
due to lapsed intelligence, Mr. Eomanes cites the case of
birds living on oceanic islands, which at first show no fear
of man, but which acquire in a few generations an instinc-
tive dread of him — for the wildness or tameness may
become truly instinctive. "If," says Dr. Kae,* "the eggs
of a wild duck are placed with those of a tame one under a
hen to be hatched, the ducklings from the former, on the
very day they leave the egg, will immediately endeavour
to hide themselves, or take to the water if there is any
water, should any person approach, whilst the young from
the tame duck's eggs will show little or no alarm, indicating
in both cases a clear instance of instinct or 'inherited
memory.' "

It must not be supposed that these two modes of origin
are mutually exclusive, and that any particular instinct
must belong either to the one class or the other. On the
contrary, many instincts have, as it were, a double root —
the principle of selection combining with that of lapsing
intelligence in the formation of a joint result. Intelligence
may thus give a new direction to a primary instinct, and,
the intelligent modification being inherited, what is prac-
tically a new instinct may arise. Conversely, selection
may tend to preserve those individuals which perform
some intelligent action, and may, therefore, aid the lapsing
of intelligence in establishing and stereotyping an instinct.
Referring the reader to Mr. Romanes's work for the
examples and illustrations by which he enforces his views,
we may now proceed to consider the subject in the light of
recently developed theories of heredity.

We have seen that a school of biologists has arisen
who deny the inheritance of acquired characters. But Mr.

* Nature, vol. xsviii. p. 2712 quoted in " Mental Evolution in Animals,"
footnote, p. 196.

436 Animal Life and Intelligence.

Bomanes's secondary instincts depend upon the inheritance
of habits intelligently acquired. By the school of Professor
Weismann, therefore (if we may so call it "without injustice
to Mr. Francis Galton), secondary instincts, in so far as
any individual acquisition is concerned, are denied.
Opposed to this school are those who lay great stress on
the inheritance of acquired characters. Some of them
seem driven to the opposite extreme in the matter of
instinct, and appear to hold that instincts are entirely (or
let us say almost entirely) due to lapsed intelligence.
Professor Eimer, of Tubingen, for example, says,* " I
describe as automatic actions those which, originally per-
formed consciously and voluntarily, in consequence of
frequent practice, come to be performed unconsciously and
involuntarily. . . . Such acquired automatic actions can
be inherited. Instinct is inherited faculty, especially is
inherited habit." In his discussion of the subject, Pro-
fessor Eimer seems to make no express allusion to primary
instincts. And he regards at any rate some of those
which are classed by Mr. Eomanes as primary, as due to
lapsed intelligence. "Every bird," he says f " must, from
the first time it hatches its eggs, draw the conclusion that
young will also be produced from the eggs which it lays
afterwards, and this experience must have been inherited
as instinct." He says % .that the infant takes the breast
and sucks " in accordance with its acquired and inherited
faculties." He believes § that " the original progenitors of
our cuckoo, when they began to lay their eggs in other
nests, acted by reflection and with design." Kegarding the
mason-wasps and their allies, which sting larvaB in the
ganglia which govern muscular action, and thus provide
their young with paralyzed but living prey, he exclaims,!
" What a wonderful contrivance ! What calculation on
the part of the animal must have been necessary to discover
it ! " Of the storing instincts of bees he remarks, IT " Selec-
tion cannot here have had much influence, since the

* " Organic Evolution," pp. 223, 224. t Ibid. p. 263.

t Ibid. p. 303. § Ibid. p. 258. || Ibid. p. 279. 1 Ibid. p. 276.

Habit and Instinct. 437

workers do not reproduce. In order to make these favour-
able conditions constant, insight and reflection on the part
of the] animals, and inheritance of these faculties, were
necessary." And he concludes,* " Thus, according to the
preceding considerations, automatic action may be described
as habitual voluntary action ; instinct, as inherited habitual
voluntary action, or the capacity for such action."

Professor Eimer would not probably deny the co-opera-
tion of natural selection in the establishment of these
instincts, but he throws it altogether into the background.
Now, such a view seems to me wholly untenable. Many of
the instincts of insects are performed only once in the
course of each individual life. Can it be supposed that the
weaving of a cocoon by the caterpillar is mainly a matter
of lapsed intelligence ? Even if we credit the hen bird
with the amount of reflection supposed by Professor Eimer,
can we grant to the ancestors of the ichneumon fly such
far-reaching observation and intelligence as really to
foresee (not by blind prevision, but through intelligent
foresight) the future development of the eggs which she
lays in a caterpillar ? Are we to suppose that the instinctive
action of the young cuckoo, which, the day after it is hatched,
will eject all the other occupants of a hedge-accentor's
nest,f can have had its origin in lapsed intelligence ? If,
because of their purposive character, we are to regard such
instincts as of intelligent origin, may we not be told that
through intelligent design the pike has beset its jaws,
palate, and gill-arches with innumerable teeth, all back-
wardly directed for the purpose of holding its slippery prey ;
and the eagle has protected its eye with a bony ring of
sclerotic plates, like the holder of an optician's watch-glass?
If mimicry in form and colour is due to natural selection,
why not mimicry in habits and activities ? If structures of
a wonderfully purposive character have been evolved with-

* " Organic Evolution," p. 298. The late G. H. Lewes held somewhat
similar views.

t See Mr. John Hancock, Natural History Transactions, Northumberland,
Durham, and Newcastle-on-Tyne, vol. viii. (1886) ; and Nature, vol. xxxiii
p. 519.

43 8 Animal Life and Intelligence.

out the intelligent co-operation of the organisms which
possess them, why not some of the highly purposive
activities ?

And here the disciple of the school of Professor Weis-
rnann will echo and extend the question, and will say,
" Yes ! why not all instinctive activities ? You are ready to
admit," he will continue, "that many instincts, wonderfully
purposive in their nature, are of primary origin, that is due
to natural selection ; why, then, invoke any other mode of
origin ? If lapsed intelligence be excluded in these cases,
why introduce it at all ? Why not admit, what our theory
of heredity demands, that * ' all instinct is entirely due to
the operation of natural selection, and has its foundation,
not upon inherited experiences, but upon the variations of
the germ' ?"

Professor Weismann's contention needs much more
serious consideration than that of Professor Eimer. I
think there is force in the a priori argument (as an a priori
argument) that since very complex instincts are probably
of primary origin, there is no a priori necessity for the
introduction of the hypothesis of lapsed intelligence. Let
me first illustrate this further.

A certain beetle (Sitaris) lays its eggs at the entrance
of the galleries excavated by a kind of bee (Anthophora) ,
each gallery leading to a cell. The young larvaB are
hatched as active little insects, with six legs, two long
antennae, and four eyes, very different from the lame of
other beetles. They emerge from the egg in the autumn,
and remain in a sluggish condition till the spring. At that
time (in April) the drones of the bee emerge from the
pupae, and as they pass out through the gallery the sitaris
larvae fasten upon them. There they remain till the
nuptial flight of the anthophora, when the larva passes
from the male to the female bee. Then again they await
their chance. The moment the bee lays an egg, the sitaris
larva springs upon it. " Even while the poor mother is
carefully fastening up her cell, her mortal enemy is be-

* Weismanu, " On Heredity," p. 91.

Habit and Instinct. 439

ginning to devour her offspring ; for the egg of the
anthophora serves not only as a raft, but as a repast.
The honey, which is enough for either, would be too little
for both ; and the sitaris, therefore, at its first meal,
relieves itself from its only rival. After eight days the egg
is consumed, and on the empty shell the sitaris undergoes
its first transformation, and makes its appearance in a
very different form. ... It changes into a white, fleshy
grub, so organized as to float on the surface of the honey,
with the mouth beneath and the spiracles above the
surface. ... In this state it remains until the honey is
consumed ; " * and, after some further metamorphoses,
develops into a perfect beetle in August.

Now, it seems to me difficult to understand how, at any
stage of this long series of highly adaptive, instinctive
activities, lapsed intelligence can have been a factor. And
therefore I say, if such a complex series \ can have resulted

* M. Fabre, as interpreted by Sir John Lubbock, "Scientific Lectures,"
2nd edit., p. 45.

t In further illustration of the fact that purposiveness and complex
adaptation of activities is no criterion of present or past direction by intelli-
gence, we may draw attention to the action of the leucocytes, or white blood-
corpuscles. Metchnikoff found that in the water-flea (Daphnia), affected by
spores of Monospora bicuspidata, a kind of yeast which passes from the
intestinal canal into the body-cavity, the leucocytes attacked and devoured
the conidia. If a conidium. were too much for one cell, a plasmodium, or
compound giant-cell, was formed to repel the invader. The same thing occurs
in anthrax, the bacilli being attacked and devoured by the leucocytes. " If
we summarize," says Mr. Bland Sutton ("General Pathology," pp. J27, 128),
" the story of inflammation as we read it zoologically, it should be likened to
a battle. The leucocytes are the defending army, their roads and lines of
communication the blood-vessels. Every composite organism maintains a
certain proportion of leucocytes as representing its standing army. When the
body is invaded by bacilli, bacteria, micrococci, chemical or other irritants,
information of the aggression is telegraphed by means of the vaso-motor
nerves, and leucocytes rush to the attack ; reinforcements and recruits are
quickly formed to increase the standing army, sometimes twenty, thirty, or
forty times the normal standard. In the conflict, cells die and often are
eaten by their companions; frequently the slaughter is so great that the
tissue becomes burdened by the dead bodies of the soldiers in the form of
pus, the activity of the cell being testified by the fact that its protoplasm
often contains bacilli, etc., in various stages of destruction. These dead cells,
like the corpses of soldiers who fall in battle, later become hurtful to tho
organism they weje in their lifetime anxious to protect from harm, for they

44-O Animal Life and Intelligence.

from natural selection and non-intelligent adaptation, I
see no a priori reason why any instinct, no matter how
complex, should not have had a like origin.

Let us, however, next consider whether Professor Weis-
mann's theory of the origin of instincts necessarily
altogether excludes intelligence as a co-operating factor.
The essential point on which that theory is absolutely
insistent is that what is handed on through inheritance is
an innate, and not an individually acquired, character. Now,
since intelligent actions are characteristically individual, and
performed in special adaptation to special circumstances,
it would seem, at first sight, that the intelligent modification
of an instinct could not, on Professor Weismann's view, be
handed on. Let us consider whether this must be so.

Speaking of ants and bees, Darwin pointed out that
their instincts could not possibly have been acquired by
inherited habit, since they are performed by neuter insects,
that is, by undeveloped females incapable of laying eggs
and continuing their race. For a habit to pass into an
instinct by inheritance, it is obviously necessary that the
organism which performs the habitual actions should be
capable of producing offspring by which these actions might
be inherited. But in this case the parental forms do not
possess these instincts, while the neuter insects which do
possess them are sterile.

And how does Mr. Darwin meet this difficulty ? " It is
lessened, or, as I believe, disappears," he says,* " when it
is remembered that selection may be applied to the family

are fertile sources of septicaemia and pyaemia — the pestilence and scourge so
much dreaded by operative surgeons." Now, if the leucocytes were separate
organisms, whose habits were being described, some might suppose that they
were actuated by intelligence, individual or inherited. But in this case the
activities are purely physiological. The marshalling of the cells during the
growth of tissue (e.g. the antler of a stag before described) is of like import.
And Dr. Verworn has shown that when a (presumably weak) electric current
is passed through a drop of water containing protozoa, they will, when the
current is closefl, flock towards the negative pole, and when the current is
opened will travel towards the positive pole. The implication of all this is
that vital phenomena may be intensely purposive, and yet afford no evidence
or indication of the present or ancestral play of intelligence.
* " Origin of Species," p. 230.

Habit and Instinct. 441

as well as to the individual. Breeders of cattle wish the
flesh and fat to be well marbled together ; an animal thus
characterized has been slaughtered, but the breeder has
gone with confidence to the same stock, and has succeeded.
Such faith may be placed in the power of selection, that a
breed of cattle always yielding oxen with extraordinarily
long horns could, it is probable, be formed by carefully
watching which individual bulls and cows, when matched,
produced oxen with the longest horns ; and yet no one ox
would ever have propagated his kind. . . . Hence we may
conclude that slight modifications of structure or of instinct,
correlated with the sterile condition of certain members of
the community, have proved advantageous ; consequently,
the fertile males and females have flourished, and trans-
mitted to their fertile offspring a tendency to produce
sterile members with the same modifications. This process
must have been repeated many times, until that prodigious
amount of difference between the fertile and sterile females
of the same species has been produced which we see in
many social insects."

Now let us apply this illustration to the case of habits
intelligently acquired. Instead of the possession of long
horns, suppose the performance of some habitual action
be observed in the oxen. Then, by carefully watching
which individual bulls and cows, when matched, produced
oxen which performed this intelligent habitual action, a
breed of cattle always yielding oxen which possessed this
habit might, on Darwin's principles, "be produced. The
intelligence of oxen might in this way be enhanced. Such
faith may be placed in the power of selection that a breed
of cattle <always yielding oxen of marked intelligence
could, it is possible, be formed by carefully watching which
individual bulls and cows, when matched, produced the
most intelligent oxen ; and yet no ox would ever have
propagated its kind. Eegarding, then, a nest of ants or
bees as a social community, mutually dependent on each
other, and subject to natural selection, that community
would best escape elimination in which the queen produced

442 Animal Life and Intelligence.

two sets of offspring — one set in which the procreative
faculty was predominant to the partial exclusion of in-
telligence, and another in which intelligent activities were
predominant to the exclusion of propagation.

It is possible that I have weakened my case by intro-
ducing such a difficult problem as the instincts of neuter
insects. And I would beg the reader to remember that
this is only incidental. What I wish to indicate is that
among the many variations to which organisms are subject,
there are variations in their intelligent activities ; that
these are of elimination value, those animals which con-
spicuously possess them escaping elimination in its several
modes ; that those survivors which thus escape elimination
are likely to hand on, through inheritance, that intelligence
which enabled them to survive ; that if, thoughout a series
of generations, such intelligence be applied to some definite
end, nervous channels will tend to be definitely established,
and the intelligent activity will more and more readily
become habitual ; that eventually, through the lapsing of
intelligence, these habitual activities may become so fixed
and stereotyped as to become instinctive ; that intelligence
has thus been a factor in the establishment of these in-
stinctive activities ; that throughout the sequence there is
no inheritance of anything individually acquired, the in-
telligent variations being throughout of germinal origin ;
and that, therefore, in the origin of instincts, the co-opera-
tion of intelligence and the lapsing of intelligence are not
excluded on the principles advocated by Professor Weismann.

What, then, is excluded? Anjr individually acquired
increment, either in the intelligence displayed or the stereo-
typing process. The subject of instinct and of animal
intelligence has not at present been considered at any
great length by Professor Weismann, but, judging by the
general tenor of his writings, I take it that what he
demands is definite proof that such individually acquired
increment is actually inherited.

As before indicated in the chapter on "Heredity,"
such proof it is, from the nature of the case, almost im-

Habit and Instinct. 443

possible to produce. Suppose that we find evidence of a
gradually increasing application of intelligence to some
important life-activity, or a more and more defined stereo-
typing of some incompletely habitual or instinctive action ;
how are we to prove that the increment in either case is
due to the inheritance of individual acquisitions, not to the
selection of favourable innate (that is to say, germinal)
variations ? Such a hopeless task may at once be
abandoned.

Are we, then, to leave the question as insoluble? I
think not. It is still open to us to consider whether there
are any cases in which the inheritance of acquired modifica-
tions is a more probable hypothesis than the selection of
favourable germinal variations. Now, the acquisition of
an instinctive dread of man, and the loss of this instinctive
timidity under domestication, seem to be of this kind.
And yet I doubt whether the evidence on this head is con-
vincing. For the loss of instinctive timidity, Professor
Weismann may invoke the aid of panmixia. But if there
is truth in what I have already urged on this head, pan-
mixia will not adequately account for the facts. On the
other hand, he may contend that the instinctive dread is
not due to the inheritance of individually acquired ex-
perience, but to the selection of the wilder birds and
animals through the persistent elimination of those which
are tame. And in support of this view, he may quote
Darwin himself, who says,* "It is surprising, considering
the degree of persecution which they have occasionally
suffered during the last one or two centuries, that the
birds of the Falklands and Galapagos have not become
wilder ; it shows that the fear of man is not soon acquired."
It is questionable, however, whether this persecution,
admittedly occasional, can have much elimination value.
There is, however, the element of imitation and instruction
to be taken into account, and the difficulty of proving that
the timidity is really instinctive. It has frequently been
observed that birds become, after a while, quite fearless of

* See Appendix to Mr. Romanes's "Mental Evolution in Animals," p. 361.

444 Animal Life and Intelligence.

trains. Here elimination is practically excluded ; but it
has to be proved that this fearlessness is truly instinctive.
Professor Eimer says,* "In my garden every sparrow and
every crow know me from afar because I persecute these
birds. Once, in the presence of a friend, I shot a crow
from the roof of my house, while the pigeons and starlings
on the same roof, to the great astonishment of my friend,
to whom I had predicted it, remained perfectly quiet.
They had learned by frequent experience at what my gun
was aimed, and knew that it did not threaten them."
There is nothing in this 'interesting observation, however,
to show that what the pigeons had learnt had, by inherited
experience, become instinctive. And Professor Weismann
will not, in all probability, be prepared to accept as a
logical inference " that this instinct of fear, because it can
be dispelled by experience, must be founded on inherited,
acquired experience." t

Fully admitting, then, that this is a matter of relative
probability, and that the observations and inferences in
this matter are not by themselves convincing, I still think
that the balance of probability is here on" the side of some
inheritance of experience. Take next such an instinctive
habit as that which dogs display of turning round in a
narrow circle ere they lie down. In its origin the instinct
probably arose with the object of preparing a couch in the
long grass. Now, is this habit of elimination value ? Can
we suppose that it arose through the elimination of those
ancestral animals which failed to perform this habit ? I
find it difficult to accept this view, though it is just possible
that the animals which did this thereby escaped the
observation of their enemies. It is also possible that this
originally was a merely purposeless habit, a strange trick
of manner, which has been inherited, and rendered constant
and fixed. Here again, however, I think the balance of
probability is that the habit was intelligently acquired and
inherited.

I have before drawn attention to the more or less in-

* " Organic Evolution," p. 227. t Ibid. p. 228.

Habit and Instinct. 445

completely instinctive avoidance, by birds and lizards, of
insects with warning coloration. That the avoidance is
not perfectly instinctive is shown by the fact that young
birds sometimes taste these caterpillars or insects. But
a very small basis of experience, often a single case, is
sufficient to establish the association. And in young
chicks the avoidance of bees and wasps seems to be perfectly
instinctive. The effects on the young birds, however, can
hardly be of elimination value. Mr. Poulton offered un-
palatable insects "to animals from which all other food
was withheld. Under these circumstances, the insects
were eaten, although often after many attempts, and
evidently with the most intense disgust." * I have caused
bees to sting young chickens ; the result was extreme dis-
comfort, but in no cases permanent injury or death. If,
then, the instinct is not of elimination value, that is to say,
not such as to save the possessors from elimination, how
can it have been established by natural selection ? And if
not due to natural selection, to what can it be due, save
inherited antipathy ?

Natural selection is such a far-reaching and ubiquitous
factor in organic evolution, that it is not likely that many
cases can be found in which the play of elimination can be
rigidly excluded. But there are not a few in which elimina-
tion does not appear to be the most important factor. Mr.
G. L. Grant has recently observed that the sparrows near
Auckland, New Zealand, have taken to burrowing holes in
sand-cliffs, like the sand-martin. The cliff-swallow of the
Eastern United States has almost ceased to build nests in
the cliffs, like its progenitors, and now avails itself of the
protection afforded by the eaves of houses. The surviving
beavers in Europe are said to have abandoned the instinct
of building huts and dams. The race being no longer
sufficiently numerous to live in communities, the survivors
live in deep burrows. In Russian Lapland, under the
persecution of hunters, the reindeer are reported to be
abandoning the tundras, or open lichen-covered tracts, for

* " Colours of Animals," p. 180.

446 Animal Life and Intelligence.

the forests. The kea (Nestor notabilis), a brush-tongued
parrot of New Zealand, which normally feeds on honey,
fruits, and berries, has, since the introduction of sheep,
taken to a carnivorous diet. It is said to have begun by
pecking at the sheep-skins hung out to dry ; subsequently
it began to attack living sheep ; and now it has learnt to
tear its way down to the fat which surrounds the kidneys.
This habit, far from being the result of elimination, is
rapidly leading to the elimination of the bird that has so
strangely adopted it.

Now, although in these cases elimination has, I
think, been a quite subordinate factor, I do not adduce
them as convincing evidence that acquired habits are
hereditary. Instruction and imitation in each successive
generation may well have come into play. There is no
proof that they are even incompletely instinctive. But I
think that these are the kinds of activities, renewed and
careful observations and, if possible, experiments on which,
may lead to more decisive results. It would probably not
be difficult to ascertain how far the carnivorous habit of
the kea has become hereditary, and how far it is performed
in the absence of instruction and without the possibility of
imitation.

I confess that when I look round upon the varied habits
of birds and mammals, when I see the frigate bird robbing
the fish-hawk of the prey that it has captured from the sea,
the bald-headed chimpanzee adopting a diet of small birds,
a Semnopithecus in the Mergui Archipelago eating Crustacea
and mollusca, and the koypu, a rodent, living on shell-
fish; when I consider the divergence of habits in almost
every group of organisms, the ground-pigeons, rock-pigeons,
and wood-pigeons, seed-eating pigeons and fruit-eating
pigeons ; the carrion-eating, insect-eating, and fruit-eating
crows ; the aquatic and terrestrial kingfishers, some living
on fish, some on insects, some on reptiles ; * the divergent
habits of the ring-ousel and the water-ousel ; and the
peculiar habits of blood-sucking bats ; — when I see these

* Wallace's " Darwinism," p. 109.

Habit and Instinct. 447

and a thousand other modifications and divergences of
habit, I question whether the theory that they have all
arisen through the elimination of those forms which failed
to possess them may not be pushed too far ; I am inclined
to believe that the inheritance of acquired modifications
has been a co-operating factor. It is not enough to say
that these habits are all useful to their several possessors.
It has to be shown that they are of elimination value — that
their possession or non-possession has made all the differ-
ence between survival and elimination.

On the whole, then, as the result of a careful considera-
tion of the subject of instinctive and habitual activities,
and in accordance with my general view of organic evolu-
tion as set forth in previous chapters, I am disposed to
accept the inheritance of individually acquired modifications
of habit as a working hypothesis. I do not think that
absolutely convincing evidence thereof can at present be
produced. But to the best of my judgment, the probabili-
ties are in favour of the inheritance of modifications of
existing activities, due to intelligence, instruction, and
imitation ; always provided that the exercise of these
modified activities is sufficiently frequent and definite to
give rise to habits in the individual.

I recognize three factors in the origin of instinctive
activities —

1. Elimination through natural selection.

2. Selection through preferential mating.

3. The inheritance of individually acquired modifica-
tions.

Of these I consider the first quite incontrovertible ; the
second as highly probable ; and the third as probable in a
less degree. In all three, intelligence may or may not have
been a factor. Some of the habits which have survived
elimination under the first factor may have been originally
intelligent, some of them from the first unintelligent.
Some of the love-antics (so called), which, through their
tendency to excite sexual appetence in the female, have
been selected under the second factor, may have had a

448 Animal Life and Intelligence.

basis in intelligence ; many of them probably have not.
And though the great majority of individually acquired
modifications of habits have owed their origin to intelligent
direction, still it is conceivable that some of them have
not. An animal may have been forced by circumstances to
modify its habits, without any exercise of intelligence ; and
this modification, forced, through changed conditions, upon
all the members of a species, may, through inheritance,
have passed into the stereotyped condition of an instinct.
Under each factor, then, we have two several categories.

1 Elimination . . \ °' of unintelligent activities.

I 6. of intelligent activities
9 e i t- ( a. of unintelligent activities.

"I 6. of intelligent activities.
3. Inheritance . . / a' of anintelligent activities.

\ b. of intelligent activities.

In all cases, however, where intelligence has been a co-
operating factor, this intelligence has lapsed so soon as the
activity became truly instinctive.

From the co-operation of the factors it is almost im-
possible to give examples which shall illustrate the exclu-
sive action of any one. The following table must therefore
be regarded as indicating the probable predominance of the
factor indicated : —

a. Caterpillars spinning cocoons.

b. Instincts of social hymenoptera.
2 fa. Drumming of snipe.

I 6. Procedure of Queensland bower-bird.
„ fa. Ants forming nests in trees in flooded parts of Siam.
\ b. Instinctive fear of man.

In speaking of the instinct of caterpillars spinning
cocoons as unintelligent, I am regarding the final purpose
of the activity. Intelligence may very possibly have come
into play in modifying the details of procedure. In giving
the drumming of snipe as an example of unintelligent
activities furthered by selection, I am assuming that it has
a sexual import, and that the activity correlated with a
narrowing of the tail-feathers was not, in its inception,
intelligently performed with the object of exciting sexual

(
\

Habit and Instinct. 449

appetence in the hen. The case of the ants of Siam is
given by Mr. Bomanes,* on the authority of Lonbiere, who
says "that in one part of that kingdom, which lies open to
great inundations, all the ants made their settlements upon
trees ; no ants' nests are to be seen anywhere else." Now,
this modification of habits may have been the result of
intelligence ; or it may have been forced upon the ants by
circumstances. The floods drove them on to the trees ;
the instinctive impulse to build a settlement was impera-
tive ; hence the settlement had to be formed on the trees,
because the ground was flooded. The difficulty of ascer-
taining whether intelligence has or has not been a factor
is simply part of the inherent difficulty of comparative
psychology — a difficulty on which sufficient stress has
already been laid in an earlier chapter.

The great majority of the instinctive activities of animals
have arisen through a co-operation of the factors, and it is
exceedingly difficult in any individual case to assign to the
factors their several values.

And here we must once more notice that the separation
off of the instinctive activities from the other activities of
animals is merely a matter of convenience in classification.
In the living organism the activities — automatic actions,
reflex actions, incompletely and perfectly established
instincts, habits, and intelligent activities — are unclassified
and commingled. They are going on at the same time,
shading the one into the other, untrammelled by the limits
imposed by a scientific method of treatment.

Once more, too, we must notice that the activities of
animals are essentially the outcome and fulfilment of
emotional states. When the emotional sensibility is high,
the resulting activities are varied and vigorous. As we
have before seen, this high state of emotional sensibility is
correlated with a highly charged and sensitive condition of
the organic explosives elaborated by the plasmogen of the
cells. After repose, and at certain periodic times, this
state of exalted sensibility is apt to occur. It is exemplified

* " Mental Evolution in Animals," p. 244.

2G

45° Animal Life and Intelligence.

in the so-called instinct of play, which manifests itself in
varied activities in the early morning, in early life, and
in the returning warmth of spring — at such times, in fact,
as the life-tide is in full flood.

But perhaps the activities which result from a highly
wrought state of sensibility are best seen at the periodic
return of sexual appetence or impulse in animals of various
grades of life and intelligence. Many organisms, at certain
periods of the year, and in presence of their mates, are
thrown into a perfect frenzy of sexual appetence. The
love-antics of birds have been so frequently described that
I will merely quote from Darwin * Mr. Strange's account
of the satin bower-bird : "At times the male will chase
the female all over the aviary, then go to the bower, pick
up a gay feather or a large leaf, utter a curious kind of
note, set all his feathers erect, run round the bower, and
become so excited that his eyes appear ready to start
from his head ; he continues opening first one wing, and
then the other, uttering a low, whistling note, and, like the
domestic cock, seems to be picking up something from the
ground, until at last the female goes gently towards him."
Instances might be quoted from almost all classes of the
animal kingdom. Many fish display " love-antics," for
example, the gay-suited, three-spine stickleback, whose
excitement is apparently intense. Newts display similar
activities. Even the lowly snail makes play with its love-
darts (spiculte amoris), practical tangible darts of glistening
carbonate of lime. Mr. George W. Peckham has recently
described! the extraordinary "love-dance" of a spider
(Saitis pulex}. " On May 24 we found a mature female,
and placed her in one of the larger boxes ; and the next
day we put a male in with her. He saw her as she stood
perfectly still, twelve inches away; the glance seemed to
excite him, and he at once moved towards her ; when some
four inches from her he stood still, and then began the

* "Descent of Man," pt. ii. chap. xiii.

t George W. and Elizabeth G. Peckham, "Occasional Papers of the
Natural History of Wisconsin," vol. i. (1889), p. 37.

Habit and Instinct. 45 [

most remarkable performances that an amorous male could
offer to an admiring female. She eyed him eagerly,
changing her position from time to time, so that he might
be always in view. He, raising his whole body on one
side by straightening out the legs, and lowering it on the
other by folding the first two pairs of legs up and under,
leaned so far over as to be in danger of losing his balance,
which he only maintained by sidling rapidly towards the
lowered side. The palpus, too, on this side was turned
back to correspond to the direction of the legs nearest it.
He moved in a semicircle for about two inches, and then
instantly reversed the position of the legs, and circled in
the opposite direction, gradually approaching nearer and
nearer to the female. Now she dashes towards him, while
he, raising his first pair of legs, extends them upward and
forward as if to hold her off, but withal slowly retreats.
Again and again he circles from side to side, she gazing
towards him in a softer mood, evidently admiring the grace
of his antics. This is repeated until we have counted a
hundred and eleven circles made by the ardent little male.
Now he approaches nearer and nearer, and when almost
within reach whirls madly around and around her, she
joining and whirling with him in a giddy maze. Again he
falls back and resumes his semicircular motions, with his
body tilted over ; she, all excitement, lowers her head and
raises her body, so that it is almost vertical ; both draw
nearer ; she moves slowly under him, he crawling over her
head, and the mating is accomplished."

It can scarcely be doubted that such antics, performed
in presence of the female and suggested at sight of her,
serve to excite in the mate sexual appetence. If so, it can,
further, scarcely be doubted that there are degrees of such
excitement, that certain antics excite sexual appetence in
the female less fully or less rapidly than others ; yet others,
perhaps, not at all. If so, again, it can hardly be ques-
tioned that those antics which excite most fully or most
rapidly sexual appetence in the female will be perpetuated
through the selection of the male which performs them.

45 2 Animal Life and Intelligence.

This is sexual selection through preferential mating. And,
I think, the importance of these activities, their wide range,
and their perfectly, or at any rate incompletely instinctive
nature, justifies me in emphasizing this factor in the origin
of instinctive activities. It has hitherto, I think, not
received the attention it deserves in discussions of instinct.

A few more words may here be added to what has
already been said on the influence of intelligence on
instinct. The influence may be twofold — it may aid in
making or in unmaking instincts. We have seen that
instincts may be modified through intelligent adaptation.
A little dose of judgment, as Huber phrased it, often comes
into play. The cell-building instinct of bees is one which
is remarkably stereotyped ; and yet it may be modified in
intelligent ways to meet special circumstances. When,
for example, honey-bees were forced to build their comb
on the curve, the cells on the convex side were made of a
larger size than usual, while those on the concave side
were smaller than usual. Huber constrained his bees to
construct their combs from below upwards, and also
horizontally, and thus to deviate from their normal mode
of building. The nest-construction of birds, again, may
be modified in accordance with special circumstances.
And, perhaps, it is scarcely too much to say that, when-
ever intelligence comes on the scene, it may be employed
in modifying instinctive activities and giving them special
direction.

Now, suppose the modifications are of various kinds
and in various directions, and that, associated with the
instinctive activity, a tendency to modify it indefinitely be
inherited. Under such circumstances intelligence would
have a tendency to break up and render plastic a previously
stereotyped instinct. For the instinctive character of the
activities is maintained through the constancy and uni-
formity of their performance. But if the normal activities
were thus caused to vary in different directions in different
individuals, the offspring arising from the union of these
differing individuals would not inherit the instinct in the

Habit and Instinct. 453

same purity. The instincts would be imperfect, and there
would be an inherited tendency to vary. And this, if con-
tinued, would tend to convert what had been a stereotyped
instinct into innate capacity ; that is, a general tendency
to certain activities (mental or bodily), the exact form and
direction of which is not fixed, until by training, from
imitation or through the guidance of individual intelligence,
it became habitual. Thus it may be that it has come
about that man, with his enormous store of innate capacity,
has so small a number of stereotyped instincts.

But while intelligence, displayed under its higher form
of originality, may, in certain cases, lead to all-round
variation, tending to undermine instinct and render it less
stereotyped, intelligence, under its lower form of imitation,
has the opposite tendency. For young animals are more
likely to imitate the habits of their own species than the
foreign habits of other species, and such imitation would
therefore tend towards uniformity.

Imitation is probably a by no means unimportant factor
in the development of habits and instincts. Mr. A. E.
Wallace, in his " Contributions to the Theory of Natural
Selection," contends that the nest-building habit in birds
is, to a large extent, kept constant by imitation. The
instinctive motive is there, but the stereotyped form is
maintained through imitation of the structure of the nest
in which the builders were themselves reared. Mr. Weir,
however, writing to Mr. Darwin, in 1868, says in a letter,
which Mr. Eomanes quotes,* " The more I reflect on Mr.
Wallace's theory, that birds learn to make their nests
because they have themselves been reared in one, the less
inclined do I feel to agree with him. ... It is usual with
canary-fanciers to take out the nest constructed by the
parent birds, and to place a felt nest in its place, and,
when the young are hatched and old enough to be handled,
to place a second clean nest, also of felt, in the box, remov-
ing the other. This is done to prevent acari. But I never
knew that canaries so reared failed to make a nest when

* "Mental Evolution in Animals," p. 226.

454 Animal Life and Intelligence.

the breeding-time arrived. I have, on the other hand,
marvelled to see how like a wild bird's the nests are con-
structed. It is customary to supply them with a small set
of materials, such as moss and hair. They use the moss
for the foundation, and line with the finer materials, just
as a wild goldfinch would do, although, making it in a
box, the hair alone would be sufficient for the purpose. I
feel convinced nest-building is a true instinct." On the
other hand, Mr. Charles Dixon, quoted* in Mr. Wallace's
"Darwinism," speaking of chaffinches which were taken to
New Zealand and turned out there, says, " The cup of the
nest is small, loosely put together, apparently lined with
feathers, and the walls of the structure are prolonged for
about eighteen inches, and hang loosely down the side of
the supporting branch. The whole structure bears some
resemblance to the nests of the hang-birds (Icteridce), with
the exception that the cavity is at the top. Clearly these
New Zealand chaffinches were at a loss for a design when
fabricating their nest. They had no standard to work by,
no nests of their own kind to copy, no older birds to give
them any instruction, and the result is the abnormal
structure I have just described."

There is more evidence in favour of the view that the
song of birds is, in part at least, imitative. That it has an
innate basis is certain ; and that it may be truly instinctive
is shown by Mr. Couch's observation of a goldfinch which
had never heard the song of its own species, but which
sang the goldfinch-song, though tentatively and imperfectly.
On the other hand, imitation is undoubtedly a factor. The
Hon. Daines Barrington says (1773), "I have educated
nestling linnets under the three best singing larks — the
skylark, woodlark, and titlark — every one of which, instead
of the linnet's song, adhered entirely to that of their
respective instructors. When the note of the titlark linnet
was thoroughly fixed, I hung the bird in a room with two
common linnets for a quarter of a year. They were in full
song, but the titlark linnet adhered steadfastly to that of

* "Darwinism," p. 76, from Nature, vol. xxxi. p. 533.

Habit and Instinct. 455

the titlark." Mr. Wallace, who quotes this, adds,* " For
young birds to acquire a new song correctly, they must be
taken out of hearing of their parents very soon, for in the
first three or four days they have already acquired some
knowledge of the parent's notes, which they afterwards
imitate." Bureau de la Malle, as quoted by Mr. Bomanes,f
describes how he taught a starling the " Marseillaise," and
from this bird all the other starlings in a canton to which
he took it are stated to have learned the air !

That dogs, monkeys, and other mammalia have powers
of imitation needs no illustration. And when we remember
that it is only the imitation of strange and unusual actions
that arrests our attention, while the imitation of normal
activities is likely to pass unnoticed, we may, I think, fairly
surmise that imitation is by no means an unimportant
factor in the acquisition and development of habits. And
where the young animal is surrounded during the early
plastic and imitative period of life by its own kith and kin,
imitation will undoubtedly have a conservative tendency.

The education of young animals by their parents has
also a conservative tendency. Mr. Spalding's observations
show that the flight of birds is instinctive ; but the parent
birds normally aid the development of the instincts by
instruction. Ants, as we have seen, are instructed in the
business of ant-life. Dogs and cats train their young.
And Darwin tells us, on the authority of Youatt,J that
lambs turned out without their mothers are very liable to
eat poisonous herbs.

We may say, then, with regard to the influence of
intelligence on instinctive activities, that it may lead them
to vary along certain definite lines of increased adaptation ;
that it may, in some cases, lead them to vary along divergent
lines, and hence tend to render stereotyped instincts more
plastic ; and that, through imitation and instruction, it
may tend to render instinctive habits more uniform in a
community, and hence, if the habits are tending to vary

* "Contributions," etc., p. 222.
t "Mental Evolution in Animals," p. 222. $ "On Sheep," p. 404.

456 Animal Life and Intelligence.

under changed circumstances in a given direction, may
tend to draw the habits of all the members of the com-
munity in that given direction.

And with regard to the more general question of the
variation of habits and instincts, we may say that, in
addition to those variations in the origin and direction of
which intelligence is a factor, there are other variations
which take their origin without the influence of intelligence
under the stress of changing circumstances, and yet others
which may arise as we say " fortuitively " or "by chance,"
that is, from some cause or causes whereof we are at
present ignorant, and which do not appear to be evoked
directly by the stress of environing circumstances.

Granting, however, the existence of these variations in
whatsoever way arising, and granting the influence of
natural selection, of sexual selection, and perhaps of the
inheritance of individually acquired modifications, those
variations which are for the good of the race or species in
which they occur will have a tendency to be perpetuated,
while those which are detrimental will be weeded out and
will tend to disappear.

Passing on now to consider the characteristics of those
activities which we term "intelligent," we may first notice
what Mr. Charles Mercier, in " The Nervous System and
the Mind," calls the four criteria of intelligence. Intelli-
gence is manifested, he says, first, in the novelty of the
adjustments to external circumstances ; secondly, in the
complexity; thirdly, in the precision; and fourthly, in
dealing with the circumstances in such a way as to extract
from them the maximum of benefit.

Now, I think it is clear that, when it is our object to
distinguish intelligent from instinctive activities, the pre-
cision of the adjustment cannot be regarded as a criterion
of intelligence. Many instinctive acts are wonderfully pre-
cise. The sphex is said to stab the spider it desires to
paralyze with unerring aim in the central nerve-ganglion.
Other species, which paralyze crickets and caterpillars,
pierce them in three and nine places respectively, according

Habit and Instinct. 457

to the number of the ganglia. And yet this seems to be a
purely instinctive action. So, too, to take but one more
example, there is surely no lack of precision in the cell-
making instinct of bees. We may say, then, that, grant-
ing that an action is intelligent, the precision of the
adjustment is a criterion of the level of intelligence; but
that, since there may be instinctive actions of wonderful
precision, this criterion is not distinctive of intelligence.
Nay, more, there are many reflex actions of marvellous
precision and accuracy of adjustment ; and there can be
no question of intelligence, individual or ancestral, in
many of these.

Nor can we regard prevision (which is sometimes
advanced as a criterion of intelligence) as specially dis-
tinctive of intelligent acts regarded objectively in the
study of the activities of animals. For, as we have
already seen, there are many instincts which display an
astonishing amount of what I ventured to term " blind pre-
vision " — instance the instinctive regard for the welfare of
unborn offspring, and the instinctive preparation for an
unknown future state in the case of insect larvae.

Nor, again, is the complexity of the adjustment distinc-
tive of intelligence as opposed to instinct. The case of the
sitaris, before given, the larva of which attaches itself to a
male bee, passes on to the female, springs upon the eggs
she lays, eats first the egg and then the store of honey, —
this case, I say, affords us a series of sufficiently marked
complexity. This instinct, the paralyzing, but not killing
outright, of prey by the sphex ; the marvellous economy of
wax in the cell-building of the honey-bee ; the affixing to
their body, by crabs, of seaweed (Stenorhynchus) , of ascidians
(an Australian Dromia}, of sponge (Dromia vulgaris), of the
cloaklet anemone (Pagurus prideauxii} ; and other cases
too numerous for citation; — these show, too, that the
circumstances may be dealt with in such a way as to
extract from them the maximum of benefit, probably with-
out intelligence. It would be quite impossible intelli-
gently to improve upon the manner of dealing with the

4.S& Animal Life and Intelligence.

circumstances displayed in many instinctive activities,
even those which we have reason to believe were evolved
without the co-operation of intelligence.

There remain, therefore, the novelty of the adjustment
and the individuality displayed in these adjustments. And
here we seem to have the essential features of intelligent
activities. The ability to perform acts in special adaptation
to special circumstances, the power of exercising individual
choice between contradictory promptings, and the indi-
viduality or originality manifested in dealing with the
complex conditions of an ever-changing environment, —
these seem to be the distinctive features of intelligence.
On the other hand, in instinctive actions there seems to be
no choice ; the organism is impelled to their performance
through impulse, as by a stern necessity ; they are so far
from novel that they are performed by every individual of
the species, and have been so performed by their ancestors
for generations ; and, in performing the instinctive action,
the animal seems to have no more individuality or originality
than a piece of adequately wound clockwork.

It may be said that, in granting to animals a power of
individual choice, we are attributing to them free-will ; and
surely (it may be added), after denying to them reason, we
cannot, in justice and in logic, credit them with this, man's
choicest gift. I shall not here enter into the free-will con-
troversy. I shall be content with denning what I mean by
saying that animals have a power of individual choice.
Two weather-cocks are placed on adjoining church pinnacles,
two clouds are floating across the sky, two empty bottles
are drifting down a stream. None of these has any power
of individual choice. They are completely at the mercy of
external circumstances. On the other hand, two dogs are
trotting down the road, and come to a point of divergence ;
one goes to the right hand, the other to the left hand.
Here each exercises a power of individual choice as to
which way he shall go. Or, again, my brother and I are
out for a walk, and our father's dog is with us. After a
while we part, each to proceed on his own way. Pincher

Habit and Instinct. 459

stands irresolute. For a while the impulse to follow me
and the impulse to follow my brother are equal. Then the
former impulse prevails, and he bounds to my side. He
has exercised a power of individual choice. If any one likes
to call this yielding to the stronger motive an exercise of
free-will, I, for one, shall not say him nay. What I wish
specially to notice about it is that we have here a sign of
individuality. There is no such individuality in inorganic
clouds or empty bottles. Choice is a symbol of indi-
viduality ; and individuality is a sign of intelligence.

But though I decline here to enter into the free-will
controversy, I may fairly be asked where I place volition
in the series between external stimulus and resulting
activity; and what I regard as the concomitant physio-
logical manifestation. I doubt whether I shall be able to
say anything very satisfactory in answer to these questions.
I shall have to content myself with little more than stating
how the problem presents itself to my mind.

I believe that volition is intimately bound up and
associated with inhibition. I go so far as to say that,
without inhibition, volition properly so called has no
existence. When the series follows the inevitable sequence —

Stimulus : perception : emotion : fulfilment in action

— the act is involuntary. And such it must ever have re-
mained, had not inhibition been evolved, had not an
alternative been introduced, thus — •

fu'fiment

Stimulus : perception : emotion

N inhibition of action.

At the point of divergence I would place volition. Volition
is the faculty of the forked way. There are two possibilities
— fulfilment in action or inhibition. I can write or I can
cease writing ; I can strike or I can forbear. And my poor
little wounded terrier, whose gashed side I was sewing up,
clumsily, perhaps, but with all the gentleness and tender-
ness I could command, could close his teeth on my hand
or could restrain the action.

I have here, so to speak, reduced the matter to its

460 Animal Life and Intelligence.

simplest expression. It is really more complex. For
volition involves an antagonism of motives, one or more
prompting to action, one or more prompting to restraint.
The organism yields to the strongest prompting, acts or
refrains from acting 'according as one motive or set of
motives or the other motive or set of motives prevails ; in
other words, according as the stimuli to action or the in-
hibitory stimuli are the more powerful.

And then we must remember that the perceptual .
volition of animals becomes in us the conceptual volition
of man. An animal can choose, and is probably conscious
of choosing. This is its perceptual volition. Man not
only chooses, and is conscious of choosing, but can reflect
upon his choice ; can see that, under different circumstances,
his choice would have been different ; can even fancy that,
under the same circumstances (external and internal), his
choice might have been different. This is conceptual
volition. Just as Spinoza said that desire is appetence
with consciousness of self ; so may we say that the volition
of contemplative man is the volition of the brute with con-
sciousness of self. No animal has consciousness of self;
that is to say, no animal can reflect on its own conscious
states, and submit them to analysis with the formation of
isolates. Self-consciousness involves a conception of self,
persistent amid change, and isolable in thought from its
states. It involves the isolation in thought of phenomena
not isolable in experience. We can think about the self
as distinct from its conscious states and the bodily organi-
zation; but they are no more separable in experience than
the rose is separable from its colour or its scent. Such
isolation is impossible to the brute. An animal is con-
scious of itself as suffering, but the consciousness is per-
ceptual. There is no separation of the self as an entity
distinct from the suffering which is a mere accident thereof ;
no conception of a self which may suffer or not suffer, may
act or may not act, maybe connected with the body or may
sever that connection. Just as there is a vast difference
between the perception of an object as here and not there,

Habit and Instinct. 461

of an occurrence as now and not then, of a touch as due
to a solid body; and the conception of space, time, and
causation ; so is there a vast difference between a percep-
tion of an injury as happening to one's self, and a con-
ception of self as the actual or possible subject of painful
consciousness. This difference is clearly seen by Mr.
Mivart, who therefore speaks of the consentience of brutes
as opposed to the consciousness of man. Consciousness
he regards as conceptual ; consentience as perceptual.*
And, as before stated, I should be disposed to accept his
nomenclature, were it not for its philosophical implications.
For Mr. Mivart regards the difference between conscious-
ness and consentience as a difference in kind, whereas I
regard it as a generic difference. I believe that consentience
(perceptual consciousness) can piss and has passed into
consciousness (conceptual consciousness) ; but Mr. Mivart
believes that between the two there is a great gulf fixed,
which no evolutionary process could possibly bridge or
span.

The perceptual volition of animals, then, is a state of
consciousness arising when, as the outcome of perception and
emotion, motor-stimuli prompting to activity conflict with
inhibitory stimuli restraining from activity. The animal
chooses or yields to the stronger motive, and is conscious
of choosing. But it cannot reflect upon its choice, and
bother its head about free-will. This involves conceptual
thought. When physiologists have solved the problem of
inhibition, they will be in a position to consider that of
volition. At present we cannot be said to know much
about it from the physiological standpoint.

Still, as before indicated, the fact of inhibition is un-
questionable and of the utmost importance. It has before
been pointed out that through inhibition, through the
suppression or postponement of action, there has been
rendered possible that reverberation among the nervous
processes in the brain which is the physiological concomi-
tant of aesthetic and conceptual thought. We have just

* In the sense in which I have used the word ; not as he uses it himself.

462

Animal Life and Intelligence.

seen that, in association with inhibition, the faculty of
volition has been developed. And we may now notice that
the postponement or suppression of action is one of the
criteria of intelligent as opposed to instinctive or impulsive
activities. This is, however, subordinate to the criterion
of novelty and individuality.

Granting, then, that an action is shown to be intelligent
from the novelty of the adjustments involved, and from the
individuality displayed in dealing with complex circum-
stances (instinctive adjustments being long-established and
lacking in originality), we may say that the level of intelli-
gence is indicated by the complexity of the adjustments ;
their precision ; the rapidity with which they are made ;
the amount of prevision they display ; and in their being
such as to extract from the surrounding conditions the
maximum of benefit.

Before closing this chapter, I will give a classification of
involuntary and voluntary activities : —

Initiation.

Motive.

Kesult.

A. Involuntary (auto-

Sense-stimulus

Unconscious re-

Automatic or

matic and reflex)

action of nerve-

reflex act

centres

B. Involuntary (habi-
tual and instinctive)

Percept (per-
haps lapsed)

Impulse (per-
haps lapsed)

Involuntary ac-
tivity

C. Voluntary (percep-

Percept

Appetence

Voluntary ac-

tual)

tivity

D. Voluntary (con-

Concept

Desire

Conduct

ceptual)

In the involuntary acts classed as automatic and reflex,
the initiation and the result may be accompanied by con-
sciousness, but the intermediate mental link which answers
to the motive in higher activities is, I think, unconscious.
In habitual and instinctive activities the consciousness of
the percept and the impulse may in some cases have
become evanescent, or, to use G. H. Lewes's phrase, have
lapsed. In the case of some instincts, originating by the
natural selection of unintelligent activities, the perceptual

Habit and Instinct. 463

element may never have emerged, and the initiation may
have been a mere sense-stimulus.

The division of voluntary activities into perceptual and
conceptual follows on the principles adopted and developed
in this work. As to the terminology employed, I agree with
Mr. S. Alexander * that it is convenient to reserve the terms
" desire " and " conduct " for use in the higher conceptual
plane. Animals, I believe, are incapable of this higher
desire and this higher conduct. It only remains to note
that it is within the limits of the fourth class (of voluntary
activities initiated by concepts) that morality takes its
origin. Morality is a matter of ideals. Moral progress
takes its origin in a state of dissatisfaction with one's
present moral condition, and of desire to reach a higher
standard. The man quite satisfied with himself has not
within him this mainspring of progress. The chief deter-
minant of the moral character of any individual is the
ideal self he keeps steadily in view as the object of moral
desire — the standard to be striven for, but never actually
attained.

* " Moral Order and Progress."

464 Animal Life and Intelligence,

CHAPTER XII.

MENTAL EVOLUTION.

THE phrase " mental evolution " clearly implies the existence
of somewhat concerning which evolution can be predicated ;
and the adjective " mental " further implies that this some-
what is that which we term " mind." What is this mind
which is said to be evolved ? And out of what has it been
evolved ? Can we say that matter, when it reaches the
complexity of the grey cortex of the brain, becomes at last
self-conscious ? May we say that mind is evolved from
matter, and that when the dance of molecules reaches a
certain intensity and intricacy consciousness is developed ?
I conceive not.

" If a material element," says Mr. A. R. Wallace,* " or
a combination of a thousand material elements in a molecule,
are alike unconscious, it is impossible for us to believe that
the mere addition of one, two, or a thousand other material
elements to form a more complex molecule could in any
way tend to produce a self-conscious existence. The things
are radically distinct. To say that mind is a product or
function of protoplasm, or of its molecular changes, is to
use words to which we can attach no clear conception.
You cannot have in the whole what does not exist in any
of the parts ; and those who argue thus should put forth
a definite conception of matter, with clearly enunciated
properties, and show that the necessary result of a certain
complex arrangement of the elements or atoms of that
matter will be the production of self-consciousness. There
is no escape from this dilemma — either all matter is con-

* " Contributions to the Theory of Natural Selection," p. 365.

Mental Evolution. 465

scious, or consciousness is something distinct from matter ;
and in the latter case, its presence in material forms is a
proof of the existence of conscious beings, outside of and
independent of what we term ' matter.' "

There is a central core of truth in Mr. Wallace's
argument which I hold to be beyond question, though I
completely dissent from the conclusion which he draws
from it. I do not believe that the existence of conscious
beings, outside of and independent of what we term
" matter," is a tenable scientific hypothesis. In which
case, Mr. Wallace will reply, "You are driven on to the
other horn of the dilemma, and must hold the preposterous
view that all matter is conscious."

Now, I venture to think that the use here of the word
" conscious " is prejudicial to the fair consideration of the
view which I hold in common with many others of far
greater insight than I can lay claim to. And it seems to
me that we cannot fairly discuss this question without the
introduction of terms which, from their novelty, are devoid
of the inevitable implications associated with "mind" and
" consciousness " and their correlative adjectives. Such
terms, therefore, I venture to suggest, not with a view to
their general acceptance, but to enable me to set forth,
without arousing at the outset antagonistic prejudice, that
hypothesis which alone, as it seems to me, meets the con-
ditions of the case.

According to the hypothesis that is known as the
monistic hypothesis, the so-called connection between the
molecular changes in the brain and the concomitant states
of consciousness is assumed to be identity. Professor
Huxley suggested the term " neuroses " for the molecular
changes in the brain, and "psychoses " for the concomitant
states of consciousness. According to materialism, psychosis
is a product of neurosis ; but according to monism, neither
is psychosis a product of neurosis, nor is neurosis a product
of psychosis, but neurosis is psychosis. They are identical.
What an external observer might perceive as a neurosis of
my brain, I should at the same moment be feeling as a

466 Animal Life and Intelligence.

psychosis. The neurosis is the outer or objective aspect ;
the psychosis is the inner or subjective aspect.

It is almost impossible to illustrate this assumption by
any physical analogies. Perhaps the best is that of a
curved surface. The convex side is quite different from
the concave side. But we cannot say that the concavity is
produced by the convexity, or that the convexity is caused
by the concavity. The convex and the concave are simply
different aspects of the same curved surface. So, too, are
molecular brain-changes (neuroses) and the concomitant
states of consciousness (psychoses) simply different aspects
of the same waves on the troubled sea of being. Again,
we may liken the brain-changes to spoken or written words,
and the states of consciousness to the meaning which
underlies them. The spoken word is, from the physical
point of view, a mere shudder of sound in the air ; but it
is also, from the conceptual point of view, a fragment of
analytic thought.

Now, we believe that the particular kind of molecular
motion which we call neurosis, or brain-action, has been
evolved. Evolved from what? From other and simpler
modes of molecular motion. Complex neuroses have been
evolved from less complex neuroses ; these from simple
neuroses ; these, again, from organic modes of motion which
can no longer be called neuroses at all ; and these, once
more, from modes of motion which can no longer be called
organic. And from what have psychoses, or states of con-
sciousness, been evolved? Complex psychoses have been
evolved from less complex psychoses ; these from simple
psychoses ; these, again, from — what ? We are stopped for
want of words to express our meaning. We believe that
psychoses have been evolved. Evolved from what ? From
other and simpler modes of — something which answers on
the subjective side to motion. We can hardly sa'y "of
consciousness ; " for consciousness answers to a particular
mode of motion called neurosis. So that unless we are
prepared to say that all modes of motion are neuroses, we
can hardly say that all modes of that which answers on

Mental Evolution. 467

the subjective side to motion are conscious. I shall venture,
therefore, to coin a word * to meet my present need.

It is generally admitted that physical phenomena, in-
cluding those which we call physiological, can be explained
(or are explicable) in terms of energy. It is also generally
admitted that consciousness is something distinct from,
nay, belonging to a wholly different phenomenal order from,
energy. And it is further generally admitted that con-
sciousness is nevertheless in some way closely, if not
indissolubly, associated with special manifestations of
energy in the nerve-centres of the brain. Now, we call
manifestations of energy "kinetic" manifestations, and we
use the term " kinesis " for physical manifestations of this
order. Similarly, we may call concomitant manifestations
of the mental or conscious order " metakinetic," and may
use the term " metakinesis " for all manifestations belong-
ing to this phenomenal order. According to the monistic
hypothesis, every mode of kinesis has its concomitant mode of
metakinesis, and when the kinetic manifestations assume the
form of the molecular processes in the human brain, the meta-
kinetic manifestations assume the form of human consciousness.
I am, therefore, not prepared to accept the horn of Mr.
Wallace's dilemma in the form in which he states it. All
matter is not conscious, because consciousness is the meta-
kinetic concomitant of a highly specialized^order of kinesis.
But every kinesis has an associated metakinesis ; and
parallel to the evolution of organic and neural kinesis there
has been an evolution of metakinetic manifestations culminating
in conscious thought.

Paraphrasing the words of Professor Max Muller,t I
say, " Like Descartes, like Spinoza, like Leibnitz, like
Noire, I require two orders of phenomena only, but I define
them differently, namely, as kinesis and metakinesis.

* I consider that an apology is needed for the coinage of this and of two
or three other words, such as " construct," " isolate," arid " predominant." I
can only say that in each case 1 endeavoured to avoid them, but found that I
could not make my meaning clear, or bring out the point I wished to emphasize
without them.

t " Science of Thought," pp. 286, 287.

468 Animal Life and Intelligence.

According to these two attributes of the noumenal,
philosophy has to do with two streams of evolution — the
subjective and the objective. Neither of them can be said
to be prior. . . . The two streams of evolution run parallel,
or, more correctly, the two are one stream, looked at from
two opposite shores." And again,* " Like Noire, I would
go hand-in-hand with Spinoza, and carry away with me
this permanent truth, that metakinesis can never be the
product of kinesis (materialism), nor kinesis the product of
metakinesis (spiritualism) , but that the two are inseparable,
like two sides of one and the same substance."

According to this view, the two distinct phenomenal
orders, the kinetic and the metakinetic, are distinct only
as being different phenomenal manifestations of the same
noumenal series. Matter, the unknown substance f of
kinetic manifestations, disappears as unnecessary ; spirit,
the unknown substance of metakinetic manifestations, also
disappears ; both are merged in the unknown substance of
being — unknown, that is to say, in itself and apart from
its objective and subjective manifestations.

It will, no doubt, be objected that the final identity of
• neuroses and psychoses is an assumption. It is pure
assumption, it will be said, that these molecular nervous
processes, and those percepts and emotions which are their
concomitants, are simply different aspects, outer and inner,
objective and subjective, physiological and psychological, of
the same noumenal series. This must fully and freely be
admitted. Any and every explanation of the connection of
mind and body is based on an assumption. The common-
place view of two distinct entities, a mind which can act on
the body and a body which influences the mind, is a pure
assumption. The philosophic view, that there are two
entities, body and mind, that neither can act on the other,
but that there is a pre-established harmony between the
activities of the one and the activities of the other, is, again,
a pure assumption. The materialistic view, that matter

* " Science of Thought," p. 279.

t I use " substance " here in its philosophical sense.

Mental Evolution. 469

becomes at last self-conscious, is a pure assumption. The
idealistic view, that the world of phenomena has no
existence save as a fiction of my own mind, is, once more,
a pure assumption. It is not a question of making or of
not making an initial assumption ; that we must do in any
case. The question is — Which assumption yields the most
consistent and harmonious results ?

Again, an answer will, no doubt, be demanded by some
people to the question — How does that which, objectively
considered, is neurosis become subjectively felt as psychosis ?
Is not the identification of neurosis and psychosis a begging
of the question, unless the how, the modus operandi, is ex-
plained ? If, in the latter query, by " begging the question"
the adoption of an initial assumption is meant, I have
already answered it in the affirmative. To the direct
question — How does the objective neurosis become conscious
as a subjective psychosis ? — while freely admitting that I do
not know, I enter the protest that it is philosophically an
illegitimate question ; for an answer is impossible without
transcending consciousness. An illustration will, perhaps,
make my meaning clear. Suppose that a sentient being
be enclosed within a sphere of opaque but translucent
ground glass, into the substance of which there are wrought
certain characters. Suppose that external to this there is
another similar but larger sphere, similarly inscribed, and
that a second sentient being is enclosed in the space between
the two spheres. By an attentive study of the two spheres,
this second sentient being arrives at the conclusion that
the markings on the convex surface of the inner sphere
answer to the markings on the concave surface of the outer
sphere ; and he is led to the conviction that what he sees
as markings on the convex, the being within the sphere
sees as markings on the concave. He is, however, perplexed
by the question — How can this be ? He is acquainted with
a certain inner surface and a certain outer surface. He is
led to correlate the markings of the one with the markings
of the other. But the question how the two can have such
different aspects is beyond his solution. Puzzle as he

470 Animal Life and Intelligence.

may, he can never solve it. It can only be solved (and
how simple then the solution!) by a being outside both
spheres, who can see what the enclosed being, " cabin'd,
cribb'd, confined," could never see, namely, that the
characters were wrought in the translucent glass of the
spheres. By which parable, imperfect as it is, I would
teach that we can never learn how kinetic manifestations
have a metakinetic aspect without getting outside ourselves
to view kinesis and metakinesis from an independent
standpoint. Or, in the words of Sir W. E. Hamilton,*
''How consciousness in general is possible; and how, in
particular, the consciousness of self and the consciousness
of something different from self are possible . . . these
questions are equally unphilosophical, as they suppose the
possibility of a faculty exterior to consciousness and con-
versant about its operations."

The only course open to us, then, in this difficult but
important problem is to make certain assumptions, and
see how far a consistent hypothesis may be based upon
them. I make, therefore, the following assumptions :
First, that there is a noumenal system of "things in them-
selves " of which all phenomena, whether kinetic or meta-
kinetic, are manifestations. Secondly, that whenever in
the curve of noumenal sequences kinetic manifestations
(convexities) appear, there appear also concomitant meta-
kinetic manifestations (concavities). Thirdly, that when
kinetic manifestations assume the integrated and co-
ordinated complexity of the nerve-processes in certain
ganglia of the human brain, the metakinetic manifestations
assume the integrated and co-ordinated complexity of human
consciousness. Fourthly, that what is called "mental
evolution" is the metakinetic aspect of what is called
brain or interneural evolution.

It would require far more space than I can here com-
mand to deal adequately with these assumptions, and meet
the objections which have been and are likely to be raised
against them. I must content myself with drawing atten-
* Quoted in Professor Veitch's " Hamilton," p. 77.

Mental Evolution. 471

tion to one or two which seem at once obvious and yet
easily met.

It may be asked — What advantage has such a view over
realistic materialism ? Why not assume that neural pro-
cesses, when they reach a certain complexity, give rise to
or produce consciousness ?

First of all, I think, the objection raised by Mr. Wallace,
in the passage before quoted, to materialism is unanswer-
able. Secondly, realistic materialism ignores the fact that
kinetic manifestations for us human-folk are phenomena of
consciousness. To this we will return presently. Thirdly,
realistic materialism, and any view which regards the
physical series as one which is independent of the psychical
accompaniments, and which regards consciousness as in
any sense a by-product of neural processes, are open to an
objection which was forcibly stated by the late Professor
Herbert.* " It is clearly impossible," he says, " for those
. . . who teach that consciousness is [a by-product and]
never the cause of physical change, to dispute that the
actions, words and gestures of every individual of the
human race would have been exactly what they have been
in the absence of mind ; had mind been wanting [had the
by-product never emerged], the same empires would have
risen and fallen, the same battles would have been fought
and won, the same literature, the same masterpieces of
painting and music would have been produced, the same
religious rites would have been performed, and the same
indications of friendship and affection given. To this
absurdity physical science [realistic materialism] stands
committed." I believe that Professor Herbert's argument,
of which this passage is a summary, is, as against realistic
materialism, sound and unanswerable. Finally, as Pro-
fessor Max Miiller has well observed,! " Materialism may
in one sense be said to be a grammatical blunder ; it is a
misapplication of a word which can be used in an oblique

* T. M. Herbert, "The Kealistic Assumptions of Modern Science
Examined," 2nd edit., p. 123.

t " Science of Thought," p. 571.

472 Animal Life and Intelligence.

sense only, but which materialists use in the nominative.
In another sense it is a logical blunder, because it rests
on a confusion between the objective and the subjective.
Matter can never be a subject, it can never know, be-
cause the name was framed to signify what is the object
of our knowledge or what can be known." Materialism,
then, for more than one sufficient reason, stands con-
demned.

It should be stated, however, that Professor Herbert
seems to regard the monistic view I am advocating as
committed to the absurdity indicated in the passage I have
quoted. I am convinced that he was here in error. Indeed,
he seems to have failed to see the full bearing of the
monistic hypothesis ; for while he combats it, he comes
very near adopting it himself. With this, however, I have
no concern. I have only to show that, on the assumptions
above set down, we are not committed to the " absurdity "
of supposing that intelligence and consciousness have had
no influence on the course of events in organic evolution —
that they have only felt the inevitable sequence of physical
phenomena without in any way influencing it. According
to the monistic hypothesis, kinesis and metakinesis are co-
ordinate. The physiologist may explain all the activities
of men and animals in terms of kinesis. The psychologist
may explain all the thoughts and emotions of man in terms
of metakinesis. They are studying the different phenomenal
aspects of the same noumenal sequences. It is just as
absurd to say that kinetic manifestations would have been
the same in the absence of metakinesis, as to say that the
metakinetie manifestations, the thoughts and emotions,
would have been the same in the absence of kinesis. It is
just as absurd to say that the physical series would have
been the same in the absence of mind, as to say that the
mental series would have been the same in the absence of
bodily organization. For on this view consciousness is no
mere by-product of neural processes, but is simply one
aspect of them. You cannot abstract (except in thought
and by analysis) metakinesis from kinesis ; for when you

Mental Evolution. 473

have taken away the one, you have taken the other also.
To speak of the organic activities being conceivably the
same in the absence of consciousness, is like saying that
the outer curve of a soap-bubble would be the same in the
absence of the inner curve. Whatever hypothetical exist-
ences this statement may be true of, it assuredly is not
true of soap-bubbles.

To pass on from this point to another, it is possible — I
trust not probable, but still not impossible — that some
one may say, "But how, on this view, can perception be
accounted for ? Granted that in the neural processes of
the individual organism kinesis is accompanied by those
metakinetic manifestations which we term ' consciousness,'
how will this account for our perception of a distant object ?
Yonder scarlet geranium is a centre of kinetic manifesta-
tions ; it is fifty yards and more away. How can I here,
by any metakinetic process, perceive the kinesis that is going
on out there ? "

For one who can ask this question, I have written the
chapter on " Mental Processes in Man," and have used the
term " construct," in vain. In vain have I endeavoured to
explain that the seat of all mental processes is somewhere
within the brain ; in vain have I indicated the nature of
localization and outward projection ; in vain have I reiterated
that the object is a thing we construct through a (meta-
kinetic) activity of the mind ; in vain have I insisted that
our knowledge is merely symbolic of the noumenal existence ;
and perhaps in vain shall I again endeavour to make my
meaning clear.

When we say that we perceive an object, the mental
process (perception) is the metakinetic equivalent of certain
kinetic changes among the brain-molecules. The object,
as an object (as a phenomenon or appearance), is there
generated. As before stated, I assume the existence of a
noumenal system of which the noumenal existence, sym-
bolized as object, is a part. But what we term the object
is a certain phase of metakinesis accompanying certain
kinetic nerve-processes in the brain. In other words,

474 Animal Life and Intelligence.

phenomena are states of consciousness, and cannot, for
the percipient, be anything else.

" It comes to this, then," an idealist will interpose :
" states of consciousness are metakinetic ; phenomena are
states of consciousness ; therefore phenomena are meta-
kinetic. Your kinesis vanishes, and you are one with us,
a pure idealist."

Before showing wherein I am not a pure idealist, let me
state why I am not. For the pure idealist, phenomena
being states of consciousness, and nothing more, the world
around resolves itself into an individual dream. Were I to
hold this view, this pen which I hold, this table at which I
write, the spreading trees outside my window, my little sons
whose merry voices I can hear in the garden, my very body
and limbs, all are merely states of my own consciousness.
This I am not prepared to accept. Do what I will, I cannot
believe that such an interpretation of the facts is true.

For this reason I make my first assumption that there
is a noumenal system of things in themselves, of which all
phenomena, whether kinetic or metakinetic, are manifesta-
tions. I differ from the pure idealist in that I believe that
phenomena, besides being states of consciousness, have
another, namely, a kinetic, aspect. What are for me states
of consciousness are for you neural processes in my brain.
These are, again, for you states of consciousness ; but still
for some one else they are kinetic processes. And an
ordinary extraneous object, like this table, is the phenomenal
aspect to me of a noumenal existence ; and since that
noumenal existence appears to you also in like phenomenal
guise, the table is an object for you as well as for me, and
not only for us, but for all sentient beings similarly con-
stituted. The world we live in is a world of phenomena ;
and it has a phenomenal reality every whit as valid as the
noumenal reality which underlies it. And that phenomenal
reality has two aspects — an inner aspect as metakinesis,
and an outer aspect as kinesis.

I must not here further develop the manner in which
the hypothesis of monism presents itself to my mind. I

Mental Evolution. 475

will only, before passing on to consider mental or meta-
kinetic evolution, draw passing attention to two matters.
We have seen that Professor Hering and Mr. Samuel
Butler have suggested "organic memory " as a conception
useful for the comprehencion of embryonic reconstruction
in development and other such matters (see p. 62). On the
hypothesis of monism, this may be regarded as a kinetic
manifestation of that which in memory rises to the meta-
kinetic level of consciousness.

The other matter is of far wider import. Monism
affords a consistent and comprehensible theory of the ego,
or conscious self — that which endures amid the flux and
reflux of our conscious states. The ego, or self, is that
matakinetic unity which answers to, or is the inner aspect
of, the kinetic unity of the organism.* Only here and
there, in fleeting and changing series, does the metakinesis
rise to the level of consciousness. But the metakinetic
unity is as completely one, indivisible, and enduring, as is
the physical organism which is its kinetic counterpart.
No one questions that there is an enduring organism of
which certain visible activities are occasional manifesta-
tions ; no one who has adequately grasped the teachings of
monism can question that the enduring ego, of which
certain states of consciousness are occasional manifestations,
is the metakinetic equivalent of the organic kinesis. This
solution of a problem which baffles alike materialists and
idealists is, as it seems to me, as satisfactory as it is
simple.

And now let us pass on to consider the question of
mental or metakinetic evolution. What, on the principles
above laid down, can we be said to know or have learnt
about it ?

The inevitable isolation of the individual mind has long
been recognized. " Such is the nature of spirit, or that
which acts," says Bishop Berkeley, " that it cannot be

* Strictly speaking, of the brain; but since the brain has no organic
independence of the body, it is best here to focus attention on the unity of the
organism.

476 Animal Life and Intelligence.

itself perceived, but only by the effects that it produceth."
" Thinking things, as such," writes Kant, " can never occur
in the outward phenomena ; we can have no outward per-
ception of their thoughts, consciousness, desires ; for all
this is the domain of the inward sense." How comes it,
then, that there is nothing of which, practically speaking,
we are more firmly convinced than that our neighbours
have each a consciousness more or less similar to our
own ? Certain it is that no one can come into sensible
contact with his brother's personality and essential spirit.
My brother's soul can never stand to me in the relation of
object. Subject he never can be to any but himself. What,
then, is he — his metakinetic self, not his kinetic material
body — to me ? In Clifford's convenient phrase, he is an
eject. And what is an eject ? An eject is a more or less
modified image of myself, that I see mirrored, as in a glass
darkly, in the human-folk around me. Into every human
brother I breathe the spirit of this eject, and he becomes
henceforth to me a living soul. Or, if this mode of
presentation does not meet with approval, I will say that
an eject is that metakinetic unity I infer as identically
associated with the organic and kinetic unity of my
brother's living body. And I base the close metakinetic
correspondence that I infer on the close kinetic corre-
spondence that I observe. But since the only form or
kind of metakinesis that I know is that of human self-
conscious personality, it is certain that the metakinetic
eject is an image of myself; it is and must be, in a word,
anthropomorphic .

Too much stress can scarcely, I think, be laid on the
human, nay, even the individual, nature of the eject. All
other-mind I am bound to think of in terms of my own
mind. The men and women I see around me are like
curved mirrors, in which I see an altered reflection of my
own mental features. By certain signs I may be able to
infer in this or that human mirror graces or imperfections
that I lack. But throughout my survey of human nature,
every estimate of intellectual or moral elevation or degra-

Mental Evolution. 477

dation that I form must ever be measured in terms of
my own subjective base-line. My conception of humanity
must always be, not only anthropomorphic, but idiomorphic.

Once more, let it be remembered that the metakinesis
that rises to the level of consciousness is that which forms
the inner aspect of the neural kinesis of my brain or yours.
For each of us, then, that metakinesis is the only possible
metakinesis which we can know as such and at first-hand.
And for the pure idealist it is the only metakinesis which
he can know at all. Not so with us. We have assumed a
noumenal system of "things in themselves," of which all
phenomena, whether kinetic or metakinetic, are manifesta-
tions. We have assumed that kinesis cannot emerge into
the light of being without casting its inseparable metakinetic
shadow. We have assumed that when the kinetic mani-
festations assume the integrated and co-ordinated complexity
of nerve-processes in certain ganglia of the human brain,
the metakinetic manifestations assume the integrated and
co-ordinated complexity of human consciousness. Human
physiology is teaching us more clearly every day that all
human activities are, physically speaking, the outcome of
neural processes. Such neural processes are in us con-
scious. Therefore, granting our assumptions, the conclusion
that my neighbour is a conscious self, just as I am, is not
only legitimate, but (as we see from the daily conduct of
men) inevitable. In other words, certain kinetic phenomena
have for us inevitable metakinetic implications.

Now, when we pass from man to the lower animals,
the metakinetic implications become progressively less in-
evitable and less forcible as the kinesis becomes more
dissimilar from that which obtains in the human organism.
The only metakinesis that we know directly is our own
human consciousness. In terms of this we have to in-
terpret all other forms of metakinesis.

It is unnecessary to go over again the ground that has
already been covered in previous chapters, in which we
have endeavoured to give some account of what seem to us
the legitimate inferences concerning the mental processes

478 Animal Life and Intelligence.

in animals. The point on which I wish here to insist is
that, outside ourselves, we can only know metakinesis in
and through its correlative kinesis. Underlying kinetic
evolution, we see that, on the hypothesis of monism, there
must have been metakinetic evolution. But of this mental
or metakinetic evolution we neither have nor can have
independent evidence. Such evolution is the inevitable
monistic corollary from kinetic evolution. More than this
it is not and cannot be. And only on the monistic
hypothesis, as it seems to me, is it admissible to believe in
mental evolution,* properly so called.

But does not, it may be asked, the hypothesis of
monism, if carried to its logical conclusion, involve the
belief in a world-consciousness on the one hand, and a
crystal-consciousness on the other? If, according to the
hypothesis, every form of kinesis has also its metakinetic
aspect, "must we not maintain," in the words of Mr. J. A.
Symonds, " that the universe being in one rhythm, things
less highly organized than man possess consciousness in
the degree of their descent, less acute than man's ? Must
we not also surmise that ascending scales of existence,
more highly organized, of whom we are at present ignorant,
are endowed with consciousness superior to man's ? Is it
incredible that the globe on which we live is vastly more
conscious of itself than we are of ourselves ; and that the
cells which compose our corporeal frame are gifted with a
separate consciousness of a simpler kind than ours ? " To
such questions W. K. Clifford replied with an emphatic
negative. " Unless we can show," he said, as interpreted
by Mr. Romanes,! " in the disposition of the heavenly

* I ought not to pass over without notice the " psychological scale " which
Mr. Romanes introduces in a table prefixed to " Mental Evolution in Animals."
It would be unjust to criticize this too closely, for it is admittedly provisional
and tentative. If such a scheme is to be framed, I would suggest that the
various phyla of the animal kingdom be kept distinct I question, however,
whether any one can produce a scheme which any other independent observer
will thoroughly endorse. And I am inclined to think that the wisest plan id
to tabulate the kinetic manifestations which we can actually observe rather
than the metakineses of which we can have no independent knowledge.

t Contemporary Bedew, July, 1 886. See Clifford's " Lectures and Essays,' '
ToL L pp. 72 and 248 ; vol. ii. p. 67.

Mental Evolution. 479

bodies some morphological resemblance to the structure of
a human brain, we are precluded from rationally entertain-
ing any probability that self-conscious volition belongs to
the universe."

I conceive that both parties, opposed as they seem, are
logically right ; and I venture to think that the terms I
have suggested will help us here. Mr. Symonds used the
word " consciousness " to signify metakinesis in general ;
Clifford used it to signify that particular kind of meta-
kinesis which in the human brain rises to the level of con-
sciousness. Not only is it not inconceivable, but it is a
logical necessity on the hypothesis of monism, that answer-
ing to the kinetic rhythm of the universe there is a meta-
kinetic rhythm ; but unless the gyrations of the spheres
have some kinetic resemblance to the dance of molecules
in the human brain, the metakinesis cannot be inferred to
be similar to the consciousness of man.

Similarly, with regard to the supposed self-consciousness
of the so-called social organism. Mr. Eomanes, in his article
on " The World as an Eject," * leads up to his conception
of a world-eject through the conception of a society-eject —
an eject, he tells us, that, for aught that any one of its
constituent personalities can prove to the contrary, may
possess self-conscious personality of the most vivid character.
Its constituent human minds may be born into it, and die
out of it, as do the constituent cells of the human body ; it
may feel the throes of war and famine, rejoice in the com-
forts of peace and plenty ; it may appreciate the growth of
civilization in its passage from childhood to maturity.

This, of course, may be so ; or it may not. Who can
tell? But Clifford- was on firm monistic ground when he
maintained that, unless the kinesis be similar, we have no
grounds for inferring similarity of metakinesis.

The study of kinesis leads us to recognize different
kinds or modes of its manifestation. There is one mode
of kinesis in the circling of the planets around the sun,
another mode of kinesis in the orderly evolutions of a great

* Contemporary Review, July, 1886.

480 Animal Life and Intelligence.

army, another mode in the throb of a great printing-press ;
there is one mode of kinesis in the quivering molecules of
the intensely heated sun, another in the wire that flashes
our thought to America, and yet another in the molecular
vibrations of the human brain. All are of the same order,
all are kinetic. But they differ so widely in mode that
each requires separate, patient, and long-continued study.
So is it, we may conclude, with metakinesis. There may
be, nay, there must be, many modes. But our knowledge
is confined to one mode — that in which the metakinesis
assumes the form of human consciousness.

I have been led to discuss this matter in order further
to indicate the inevitable limits of our knowledge of meta-
kinetic evolution. Our conclusions may be thus sum-
marized : First, we can know directly only one product of
metakinetic evolution — that revealed in our own conscious-
ness. Secondly, the process of metakinetic evolution must
be reached, if reached at all, indirectly through a study of
kinetic evolution. Thirdly, we have no right to infer a
mode of metakinesis analogous to human consciousness,
unless the mode of kinesis is analogous to that which is
observed in neural processes. And, fourthly, the closer the
kinetic resemblance we observe, the closer the metakinetic
resemblance we may infer.

The last point we have to notice, and it is by no means
an unimportant one, is that, just as the kinetic evolution of
the organism must be studied in reference to its kinetic
environment, so, too, must the metakinetic evolution of
mind be studied in reference to 4its metakinetic or mental
environment.

Of course, in ordinary speech, and even in careful
scientific description, we are forced, if we would avoid
pedantry, to skip backwards and forwards from the kinetic
to the metakinetic. We speak of a kinetic cow giving rise
to metakinetic fear, and this determining certain kinetic
activities. Why we thus interpose a mental link in a
physical series has already been explained. The physical

Mental Evolution. 481

cow we know, the physical activities we know, the physical
neuroses we scarcely know at all. On the other hand, fear
we have ourselves experienced, and know well. Hence we
introduce the mental link that we know in place of the
physical link of which we are ignorant. And there can be
no harm in our doing so when we are working on the
practical, and not the philosophical plane. But when we
are striving to go deeper, and are employing that gift of
analysis which is man's prerogative, in order to proceed to
a higher and more complete synthesis, — then we must be
careful to keep separate those processes which analysis
discloses to be distinct. And I repeat that, on the philoso-
phical plane of thought, we must remember that metakineses
are determined by other metakineses, and by them alone.

The reader who has kept his head among these slippery
places will at once see that this is and must be so ; for,
as we have already seen (p. 474), all phenomena are states
of consciousness, whatever else they may also be. The cow,
as a phenomenon, is a construct, a product of mental
activity, and woven out of states of consciousness. For the
pure idealist she is this and nothing more. But for us she
is a real external entity, manifested thrpugh phenomenal
kineses. Hence in ordinary speech we separate the kinetic
cow from its metakinetic symbols in consciousness (the
convex from the concave aspect), and call the former the
cow itself, and the latter our idea of the cow. But, as
before maintained, my idea of an object is for me^the object.
And this is now justified by our deeper analysis.

The physiologist, dealing with organic phenomena in
terms of motion (kinesis), proclaims that the physical series
is complete, that there is no necessity for the introduction
of feeling which is at best but a by-product. The idealist,
dealing with the processes of thought and emotion in terms
of consciousness, proclaims that his series is complete — an
external material universe is an unnecessary encumbrance.
Each proclaims a half-truth ; each sees that half of the
truth which alone is visible from his special standpoint.
Monism combines the two (and is, of course, scouted by

2i

482 Animal Life and Intelligence.

both). It sees not only that the one series does not in any
case interfere with the other, but that the conception of
such an interference involves an impossibility and incon-
gruity. As soon could one speak of the convexities of one
side of a curved surface interfering with the corresponding
concavities of the other side, as of the metakinetic series
interfering with the kinetic series, which is its other aspect.
But if the one cannot interfere with the other, neither can
the one exist without the other. To apply the same
analogy, as well might one speak of the convexities of a
curved surface existing without the concavities of its other
side, as of the kinetic phenomena of organic life as being con-
ceivably the same in the absence of conscious intelligence.

Eemembering, then, that just as the environment of
kinetic phenomena is itself kinetic, with which conscious-
ness can in no wise interfere, so is the environment of
metakinetic phenomena, perception, thought, and emotion,
itself metakinetic. Let us now proceed to consider some of
the implications.

We have already seen that, in what we may regard as
the earlier phases of organic and mental life, the series
between stimulus, and activity is a simple one, which may
be kinetically represented thus —

Stimulus — ^ neural processes — > motor-activities ;

but that when inhibition is developed, there arises an
alternative, thus —

^» motor-activities.
Stimulus-^ neural processes ^ .^.^ ^^

And we further saw that, as a result of this inhibition, the
entering stimuli, instead of, as it were, rapidly running out
of the organism in motor-activities, set up a more and
more complex series of diffused and reverberating neural
processes in the brain or other central ganglia.

From the metakinetic view-point these diffused and
reverberating neural processes in the brain culminate in
consciousness as thought, aesthetic emotion, and the higher
conceptual mental activities. Deeply as these influence

Mental Evolution. 483

conduct, they are, to a large extent, independent of con-
duct. A man's thoughts and aesthetic yearnings may be of
the truest and purest; but in the moment of temptation
and action, when stimuli crowding in run through rapidly
to action, he falls away. His conduct belies his ideals.
Nevertheless, the ideals were there, but too far away in the
region of thought and abstract aesthetics to be operative in
action.

Now, we may divide the metakinetic concomitants of
neural processes into two categories : first, those which are
intimately associated with neural processes directly leading
to motor-activities ; secondly, those which are, so to speak,
floated off from these into the region of thought and
aesthetic emotion, and which are therefore associated with
neural processes only indirectly or remotely leading to
motor-activities. Both have, of course, kinetic equivalents
in neural processes, but the former are directly associated
with activities and conduct, and the latter are not.

Let me exemplify. Interpretations of nature, theories,
hypotheses, belong to the latter class. Their association
with activities is in the main indirect. Whether we believe
in materialism, idealism, or monism, our conduct is much
the same. People got out of the way of falling stones,
and guarded against being caught by the incoming tide,
before science comprised both phenomena under the theory
of gravitation. The conduct of human-folk was not much
altered by the replacement of the geocentric by a helio-
centric explanation of the solar system. It matters not
much how a man explains the lightning's flash so long as
he avoids being struck. The bird continues to soar quite
irrespective of man's prolonged discussion of how it can be
explained on mechanical principles. And in general the
practical activities of mankind remain much the same (I
do not say quite the same, for there are remote and indirect
results of the greatest importance in the long run) whatever
their particular theory of the universe may be.

Now, let us note the implication. We have said a good
deal in earlier chapters about natural elimination and

484 Animal Life and Intelligence.

selection. To which category of neural kineses do they
apply — to those associated with practical results; or to
those associated with theoretical results (supposing these
to obtain below the level of man) ; or to both ? Clearly to
those associated with practical results. It matters not
what theories a lion, or an adder, or a spider hold (supposing,
again, that they are capable of theorizing, which I doubt).
Its practical activities determine whether it survives or not.
So, too, with men, so far as they are subject to natural
elimination. It matters not what may be the nature of
their thoughts, their aesthetic yearnings, their ideals.
According to their practical conduct, they are eliminated or
escape elimination. In other words, elimination or natural
selection applies only remotely or indirectly to the human
race regarded as theorists, aesthetes, or interpreters of
nature.

Before proceeding to indicate to what laws our theories
and interpretations of nature and moral ideals are subject,
we may note that there are sundry activities of man, the
outcome of his conceptual thought and emotion, which are
also, under the conditions of social life, to a large extent
beyond the pale of elimination. I refer to the aesthetic
activities — music, painting, sculpture, and the like ; in a
word, the activities associated with art, literature, and pure
science. These, in the main, take rank alongside the ideas
of which they are the outward expression. Natural selec-
tion, which deals with practical, life-preserving, and life-
continuing activities, has little to say to them. They are
neutral variations which, so far as elimination is concerned,
are neither advantageous nor disadvantageous, and, there-
fore, remain unmolested. _

We may, therefore, fully agree with Mr. Wallace, when
he says,* "We conclude, then, that the present gigantic
development of the mathematical faculty [as also of the
musical and artistic faculties] is wholly unexplained by the
theory of natural selection, and must be due to some
altogether distinct cause." Nay, we may go further, and

* " Darwinism," p. 467.

Mental Evolution. 485

say that it is only by misunderstanding the range of
natural selection as an eliminator that any one could suppose
that these faculties could be explained by that theory.

We must admit, then, that there are certain neural
kineses which, from the fact that they are unassociated
with life -pre serving and life-continuing activities, are not
subject to the law of elimination ; and in the development
of which natural selection cannot have been an essential
factor. These, in their metakinetie aspect, are conceptual
thoughts, emotions, and ideas. Eemembering the distinc-
tion drawn in the chapter on " Organic Evolution "
between origin and guidance, let us proceed to inquire, first,
how these ideas have been guided to their present develop-
ment ; and, secondly, how we may suppose these special
variations to have originated.

To understand their development, we must understand
their environment. The environment of metakineses is, as
we have already seen, constituted by other metakineses.
What we have now to note is that the environment of con-
ceptual ideas, as such, is constituted by other ideas. The im-
mediate environment of an hypothesis is other hypotheses ;
of a moral ideal, other moral ideals ; of an aesthetic thought,
other aesthetic thoughts ; of a religious conception, other
religious conceptions. But not only are ideas environed
by ideas of their own order ; they are environed by ideas
of other orders. Thus a scientific hypothesis or a moral
ideal may be in harmony or conflict with religious concep-
tions, and its fate may be thereby determined ; or a
religious conception may be in harmony or conflict with
psychological principles, and its acceptance or rejection
thereby determined. So that we may say, in general, that
the environment of an idea is the system of ideas among which
it is introduced.

Of course, it must be clearly understood that it is with
the individual mind that we are dealing The scientific
ideas, moral ideals, aesthetic standards, religious concep-
tions, of a tribe, nation, or other community, are simply
representative, either of the general views of the majority

Animal Life and Intelligence.

of the individuals, or more frequently of a majority among
a cultivated minority. In any case, we have seen that
metakineses are and must be an individual matter. For
each individual there is a separate ideal world.

Through certain activities, notably language spoken or
written, men can symbolize to each other the ideas that are
taking metakinetic shape in their own minds. All-im-
portant, however, as is this power of intercommunication
by means of language, it does not a whit alter the fact that
the idea and its environment have to work out their rela-
tions to each other separately in each individual mind.
My neighbour may symbolize, through language, his ideas
in such a form that similar ideas may be called up in my
mind ; but it is there that they have to make good their
claim for acceptance in the environment of the system of
ideas among which they are introduced.

Now, what is the guiding principle of the evolution and
development of ideas in the world of their metakinetic
environment ? Is there any principle analogous to that of
elimination which we have seen to be of such high impor-
tance in organic evolution ? I believe that there is. An
idea is accepted or rejected according to its congruity or
incongruity with the system of ideas among which it is
introduced. The process has, perhaps, closer analogy with
elimination than with selection, inasmuch as it would
seem to proceed by the rejection of the incongruous, leaving
both the congruous and the neutral. An idea or hypothesis
may be accepted, at any rate provisionally, so long as it is
not in contradiction to the theories and beliefs already
existing in the mind.

It may, however, be objected that this view is at variance
with the familiar observation that there are many excellent
people who hold and maintain theories which are exceed-
ingly incongruous, which seem, indeed, to us mutually
antagonistic. Yes, to us. Brought into the environment
of our system of ideas, one or other of these antagonistic
views would be eliminated through incongruity. Not so,
however, with those who hold both. Amid the environ-

Mental Evolution. 487

ment of a less logical and less coherent system of ideas,
both can find admission, if not as congruous, still as
neutral. A sense of their incongruity is not aroused.

But there are some people, it may be said, who con-
sciously hold views which they admit to be incongruous ;
who base all their scientific reasonings on a continuity of
causation, but who, nevertheless, believe in miraculous
interruptions of that continuity. In this case, however,
the incongruity is made congruous in a higher synthesis.
They belie themselves when they suppose that they are
holding incongruous views. Stated at length, what they
admit is that miraculous interventions are incongruous,
not for them, but for those whose whole system of thought
is cast in another mould than theirs — for the materialist
and the infidel.

I cannot discuss the matter further here. This is not
the place to show, or attempt to show, how the evolution
of systems of thought has caused, or is causing, certain
ideas, such as that of slavery, religious persecution, the
moral and physical degradation of our poor, to reach that
degree of incongruity which we signify as abhorrent ; or
how that evolution has caused yet more primitive ideas to
seem positively repulsive. Nor is it the place to show, or
attempt to show, how the advance of scientific knowledge
has been constantly accompanied by the elimination of
incongruous conceptions. I must content myself with the
brief indication I have given of the principle of elimination
through incongruity as applied to ideas.

It may be said that such a principle does not account
for the origin of the new congruous ideas, but only for the
getting rid of old incongruous ideas. Quite true. But I
have grievously failed in my exposition of natural selection
through elimination if I have not made it evident that this
objection (if that can be called an objection which, in
truth, is none) lies also at the door of Darwin's gene-
ralization.*

* In both cases, the question to which an answer is suggested is not —
W hat variations will arise ? but— What variations will survive ?

Animal Life and Intelligence.

Now, from all that has been said in this chapter, it will
be seen that, on the hypothesis of monism, we cannot
regard organic and mental evolution as continuous the one
into the other, but rather as parallel the one with the
other — as the kinetic and metakinetic manifestations of
the same process. Organic evolution is a matter of
structure and activity. If the structure or the activity be
not attuned to the environing conditions, it will be elimi-
nated, those sufficiently well attuned surviving. Turning
to the metakinetic aspect, we have seen that there are
certain mental processes which are directly and closely
associated with activities. Their evolution will be in-
timately associated with organic evolution. For if these
processes lead to ill-attuned activities, the organism will
be eliminated ; and thus the evolution of well-attuned
activities and their corresponding mental states will proceed
side by side. We may, therefore, say, not incorrectly, that
these lower phases of mental evolution are subject to the
law of natural selection.

But when the neural processes which intervene between
stimulus and activity become more complex and more
roundabout ; when, instead of being directly and closely
associated with life-preserving activities, they are associated
indirectly and remotely ; — then they become, step by step,
removed from their subjection to natural selection. And
when, in man, the metakineses associated with these neural
kineses assume the form of hypotheses, theories, interpreta-
tions of nature, moral ideals, and religious conceptions,
these are, except in so far as they lead to activities which
may conduce to elimination, no longer subject to the law
of natural selection, unless we use this term in a somewhat
metaphorical, or at least extended, sense. They are subject,
as we have seen, to a new process of elimination through
incongruity.

Similarly with that wide range of conduct in man which
is the outcome of his conceptual life, and is removed from
those merely life-preserving activities which are still, to
some extent, under the influence of natural elimination.

Mental Evolution. 489

Conduct is here modified in accordance with the conceptual
system of which it is the outcome and outward expression.
And this higher conduct is subject, not to elimination
through natural selection, but to elimination through in-
congruity. Slavery would never have been abolished
through natural selection ; by this means the modest
behaviour of a chaste woman could not have been developed.
To natural selection neither the -Factory Acts nor the
artistic products in this year's Academy were due ; by this
process were determined neither the conduct of John
Howard nor that of Florence Nightingale. Some evolu-
tionists have done no little injury to the cause they have at
heart by vainly attempting to defend the untenable position
that natural selection has been a prime factor in the higher
phases of human conduct. I believe that natural selection
has had little or nothing to do with them as such. They
are the outcome of conceptual ideas, and are subject to the
same process of elimination through incongruity.

So soon as, in the course of mental evolution, the idea
of slavery became incongruous, and in certain minds
abhorrent and repulsive, steps were taken to check the
conduct which was the outward expression of this idea. So,
too, in other cases. The reformer must not, however, be too
far in advance of his generation, if his reform is to be practi-
cally carried out. When his ideas are so "advanced" as
to be incongruous with those of all but a very small minority
of his contemporaries, even they are forced to confess that
the nation is not yet ripe for the changes they contemplate.

No one will question that artistic products are the
outcome of artistic ideas. In the slow and difficult progress
of a new school of painting or of music, we see exemplified
the rejection of the new ideas through their incongruity
with the old-fashioned artistic systems. Only gradually do
there grow up new generations for whom these new ideas
are not incongruous. For them the old-fashioned systems
become incongruous ; and if the school becomes dominant,
artistic products embodving the old ideas are eliminated
through incongruity.

49° Animal Life and Intelligence.

We are not all alike. Our mental systems are different.
One artist "will introduce into his canvas effects which, to
the eye of another, will at once strike a jarring note of
incongruity. To some minds the institution of slavery
presents no incongruity. There are not wanting men for
whom the degrading moral and physical conditions under
which many of our poor are forced to live and work present
little or no incongruity. To the Eussian, English fidelity
to the marriage vow is said to be as incongruous as, to an
English woman, is the harem of an Eastern potentate.

In the higher phases of human conduct, then, the
activities are subject to the law of the ideas of which they
are the outcome — the law of elimination through incongruity.
I have said that natural selection has little or nothing
to do with these higher phases of conduct. But has not
human selection through preferential mating? I believe
that it has ; and I trust that it will have a still greater
influence in the future. It is one of the noblest privileges
of woman, for with her mainly lies the choice, that she
may aid in raising humanity to a higher level. If once
the idea of marrying for anything but pure affection could
become utterly incongruous to woman's mental nature ;
and if once the idea of perpetuating any form of moral,
intellectual, or physical deformity could become equally in-
congruous ; the bettering of humanity, through the exclusion
of the deformed in body and mind from any share in its
continuance must inevitably follow. Here, again, ideas
would determine conduct.

And what, we may now proceed to ask, is the physio-
logical or kinetic aspect of this metakinetic process ? The
answer to this question involves the conception of what I
would term "interneural evolution." Just as the environ-
ment of a conceptual idea is constituted by other conceptual
ideas, so is the environment of its neural concomitant con-
stituted by the other neural processes in the brain. Just
as no idea can get itself accepted if it be in incongruity
with the system of ideas among which it is introduced, so,
too, can no neural process become established if it be not

Mental Evolution. 491

in harmony with the other neural processes of the cerebral
hemispheres. The brain is a microcosm; its neural pro-
cesses are interrelated ; and the environment of any neural
process is constituted by other neural processes.

A little consideration will show that this must be so ;
that it is only the physical or kinetic aspect of what is
freely admitted when the mental or metakinetic aspect is
under consideration. If it be admitted that states of con-
sciousness are determined by other states of consciousness,
and that states of consciousness are the concomitants of
certain neural processes in the brain, it follows as a logical
necessity that brain-neuroses, however originating, are
determined in their evolution by other brain-neuroses ; and
that there has been a brain or interneural evolution,
distinct from and yet intimately associated with the
evolution of other bodily structures and activities. The
more closely and directly brain-neuroses are associated
with immediate activities, the more closely implicated is
interneural evolution in the process of organic elimination
through natural selection. But when long trains of neuroses
take place in only remote and distant connection with
other bodily activities, they are removed from the process
of elimination through natural selection, and interneural
evolution is allowed to proceed comparatively untrammelled.

I have already indicated my belief that abstraction
(isolation), analysis, and conceptual ideas have been
rendered possible through language, and are excellences
unto which the lower animals do not attain. Hence I
regard this comparatively untrammelled phase of inter-
neural evolution as something essentially human, something
which differentiates man from brute. And I would correlate
man's greatly developed brain — inexplicable, I think, by
natural selection alone — with this later and special phase
of interneural evolution. Even in the lowest savage this
brain-evolution has proceeded a long way. I am not fitted
in this matter to offer an opinion which would carry much
weight. But from all that I have read I gather that
savages have in all cases elaborated a complex — often a

492 Animal Life and Intelligence.

highly complex — interpretation of nature and theory of
things. The interpretation may seem bizarre and incon-
gruous enough to us, full of fetishism and strange super-
stitions, but it is an interpretation ; to the savage it
presents no incongruity ; to him the incongruity is in the
oddly assorted beliefs of the missionary. His system of
ideas is, in fact, one of the many possible systems to
which mental evolution may give rise.

For what we call systems of thoughts, interpretations
of nature, theories of things, are so many genera and
species which have resulted from this later phase of meta-
kinetic evolution. Our methods are at present too coarse,
our powers too limited, to enable us to determine these
species from their kinetic aspect. The brains of Kaffir and
Boer, of ploughboy and merchant, of materialist and idealist,
are too subtly wrought to enable us to trace the systems of
kineses which were the concomitants of their scheme of
beliefs. But we can learn something of the genera and
species from their metakinetic aspect as symbolized through
language and other bodily activities. They fall into certain
groups, fetishistic, spiritualistic, materialistic, idealistic,
monistic, and so on, and within these groups there are sub-
divisions. This is not the place to consider them or discuss
their characteristics. What I wish to note about them is
that, diverse as they seem and are, each is a coherent pro-
duct of mental evolution. In each, all that is incongruous
to itself has been or is being eliminated.

There are some people, however, who are surprised at
the incongruity of interpretations of nature among each
other. Fetishism, they say, has been proved to be utterly
false. It constitutes a hideous and grotesque delirium.
How can that which is utterly and completely false to
nature have had a natural evolution ? Now, for the elite of
the Aryan race, whose systems of ideas have been moulded
in accordance with the conceptions of modern science, no
doubt the fetishism of the poor savage seems sufficiently
incongruous and grotesque. So, too, does the system of
ideas of the Eight Kev. Bishop of appear no doubt,

Mental Evolution. 493

to the learned and eminent Professor , and vice versa.

And so, too, no doubt, does the system of ideas of the white
man (who introduces firearms and firewater, and preaches
the gospel of forgiveness and temperance) appear to the
poor savage. Each in his degree wonders how this falsity,
this incongruity, can have had a natural genesis. But in
each case the falsity and the incongruity is not within the
system itself, but between different systems.

Once more, I repeat that if the individual nature of the
systems of ideas be not adequately grasped, the nature of
mental evolution will not be apprehended. States of con-
sciousness can only be determined by other states of con-
sciousness ; and states of consciousness are for the indi-
vidual subject, and for him alone. Conceptual ideas are
states of consciousness; and "falsity to nature" means,
and can only mean, incongruity with the environing states
of consciousness in the individual mind. For the savage
there is no falsity to nature in his fetishism. The idea
presents no incongruity with his system of ideas ; no more
incongruity than filed teeth, flattened head, or pierced nose
do to his standard of beauty. It is with our system of
ideas (i.e. mine or yours) that his fetishism is false and
incongruous. The falsity or incongruity, I repeat, is not
within the system itself, but between different systems.

It may still, however, be said — Only one interpretation
of nature can be true ; all others must be false. And the
falsity is not merely incongruity with other ideas in other
systems of thought or belief ; it is falsity to the plain and
obvious facts of nature.

We may freely admit that only one interpretation of
nature can be true. But who is to determine which ? Who
can decide the question between monist and materialist ?
Who dare arbitrate between the bishop and the professor ?
The criterion of fitness in this case, as in others, is survival ;
and who can say what existing interpretation of nature (if
any) shall outlive all its competitors ? Who can say what
will be the nature of the further evolution of any existing
philosophical creed ? The elimination of the false is a slow

494 Animal Life and Intelligence.

and gradual process ; and many degenerate systems of
ideas may linger on in the darker corners of the world of
men. False or out of harmony as they seem to be with
the higher phases of development ; false or out of harmony
as they would be with a different and more exalted environ-
ment ; they are not false or out of harmony with the
environment in the midst of which we find them ; they are
not false or out of harmony with " the plain and obvious
facts of nature," as these exist for the ill-developed or
savage mind.

The plain and obvious facts of nature, as interpreted by
men of science in 1890, have simply no existence for the
untutored or the savage intellect. For him they have not
emerged into the light of consciousness. But while we
cannot blame the savage for entertaining -ideas which are
false to facts which for him have no existence, we may
none the less believe that his system of ideas is not among
those which are destined to become predominant species.
So far as we can judge, the winning species among systems
of ideas and interpretations of nature are those in which
the greatest number of ideas are fused into harmonious
synthesis ; in which all the ideas are congruous, few or
none neutral ; and in which the abstract or conceptual
ideas, when brought into contact with concrete or perceptual
states of consciousness, are found to be in harmony and
congruity therewith.

There is one more question in this connection on which
I must say a few words. How, it may be asked, has the
world become peopled, for many primitive and savage folk,
with a crowd of immaterial spiritual essences, so that it is
scarcely too much to say that, for some of these peoples,
everything has its double ; and there is no material exist-
ence that has not its spiritual counterpart ?

I would connect this almost universal tendency with the
origin of abstract ideas (isolates) through language. When
the named predominant gave rise to the isolate (see p. 374),
it could scarcely fail that the primitive speakers and
thinkers should tend to regard those qualities or properties

Mental Evolution. 495

which they could isolate in thought (conceptually) as also
isolable in fact (perceptually). And we may well suppose,
though this is, of course, hypothetical, that one of the
earliest severances to be thus effected through isolation
was the severance of mind and body. The first phenomena
that the nascent reason would endeavour to explain would
probably be those of daily life and almost hourly experi-
ence. Many familiar facts would seem to point to the
temporary or permanent divorce of the part which is
conscious and feels, from the part which is tangible and
visible. During wakeful life the two are closely associated.
The visible part, or body, is conscious. But during sleep,
or under the influence of a heavy blow, the visible part,
which before was conscious, is conscious no longer. The
conscious part is, therefore, absent, but returns again after
a while. On death the conscious part returns no more.
The divorce of the two has become permanent.

And then comes in the confirmatory testimony of dreams.
In dreams the savage has seen his enemy, though that
enemy's body was far away. Here, then, is the spirit
which has left the body during sleep. In dreams also the
slain enemy or the dead chief appears. The spirit, per-
manently divorced from the body, still walks the earth in
spirit-guise.

Many occurrences would seem like the fulfilled threats
of dead enemies or the fulfilled promises of dead ancestors.
How can these be explained ? Are they not produced by
the ghost of the departed enemy, by the spirit of the
deceased ancestor ? And if these spirits are still powerful
to act, why not petition them to act in certain ways ?

Probably primitive man would explain all activities
anthropomorphically. What knows he of gravitation or
the laws of the winds ? He knows himself as agent, and
attributes his activities to the immaterial spirit within
him ; for when this is absent during sleep or in death
these activities cease. All acting things might, therefore,
come to be regarded as dual in their nature — possessed of
a sensible material bodily part, and an insensible active

496 Animal Life and Intelligence.

spiritual part. And thus the whole world might be peopled
with living existences of the spiritual order.

Now, whether the fetishistic faith arose in some such
way as this or not — and we can never know how it arose,
but can only guess — there would be nothing in such primi-
tive explanations which would violate the law of congruity.
They would have, therefore, a perfectly natural genesis.
The attempted interpolation at such a stage of primitive
reason of any modern scientific conception would be futile.
It would at once be rejected through incongruity.

The history of scientific conceptions seems to show that
they were first adopted with regard to phenomena on the
very horizon of thought — in regions, that is to say, most
remote from the central citadel of the soul. Only gradually
have they, little by little, encroached upon this centre ; and
the application of them to physiology and psychology is a
matter of quite modern times. Even to-day only a minority,
but an increasing minority, of thinkers are prepared in-
dissolubly to unite the mind and body, so long divorced in
thought, so completely united, as many of us believe, in
their essential being.

I have now, I trust, illustrated at sufficient length the
principle of elimination through incongruity in interneural
and its associated metakinetic or mental evolution. This,
however, like natural selection, is a matter of guidance ;
we have still to consider the question of origin.

In truth, we know too little on the subject to enable us
to discuss it with much profit. From the kinetic or
organic point of view, neural variations take their place
among the other variations, the origin of which, as we have
already found, is so hard to account for. There may be a
tendency for neural vibrations to mutually influence each
other (like two clocks placed side by side), and thus
gradually to drag each other into one harmonious and
congruous rhythm. But this, though not improbable, is
purely hypothetical. There is the hypothesis of the in-
heritance of acquired variations, the increased congruity
acquired by the parent being in some degree transmitted

Mental Evolution. 497

to the offspring. There is the view which Mr. Wallace
adopts * with regard to the origin of accessory plumes, that
such variations may be due to "a surplus of strength,
vitality, and growth-power, which is able to expend itself
in this way without injury," and not without profit. The
development of the social habit, the mutual aid and protec-
tion thus afforded, may well have left a balance of the
life-energy, previously employed in individual self-preserva-
tion, available for this purpose. And then there is always
the hypothesis of favourable fortuitous variations to fall
back upon.

On only one of these points do I propose to say a few
words — that of the possible inheritance of acquired varia-
tions.

Let us restate the problem here for the sake of clearness.
There is, according to the suggestion put forward in this
chapter, an interneural evolution, leading to an harmonious
development of the neuroses in the individual brain. But
this special evolution of the brain is nowise independent of
the more general evolution of the body. The human being,
as an organism, is still subject to natural elimination and
human selection. Elimination through the action of sur-
rounding physical conditions, although it has played some
part in the evolution of man, is not a factor of the first
importance. Elimination through enemies is more im-
portant, but has not much bearing on the question at
present before us — the evolution of the conceptual. Elimi-
nation by competition, again, though a factor of yet greater
importance in human evolution, has, nevertheless, so far as
individuals are concerned, but little bearing on our present
question. Few are eliminated through the absence of the
conceptual faculty. Natural elimination, then, is, as Mr.
Wallace well pointed out, practically excluded in this
matter. No doubt, in the struggle between tribes and

* " Darwinism," p. 293. It is strange that Mr. Wallace did not apply this
view to the mathematical and artistic faculties discussed in his last chapter.
It is true that such application tends to undermine the argument there
developed. But Mr. Wallace is far too great and conscientious a thinker to
be influenced by such a consideration.

2K

498 Animal Life and Intelligence.

nations, that community is most likely to be successful in
which there is rational guidance. No doubt, during the
earlier phases of the development of ma-n on our islands,
the elimination of the irrational was a factor in progress.
But if we take the last three centuries of English history, I
doubt whether it can be shown that there has been much
elimination determined by the relative absence of conceptual
ideas and emotions.

Human selection has been a much more important
factor. Those individuals which showed the higher types
of intellectual thought have been constantly selected.
Eiches, rank, and social position have been bestowed upon
them. Of course, there have been exceptions ; great in-
tellects have been allowed to languish in their lifetime,
and have only obtained recognition through their works
after death. But every day there is less chance of a genius
dying in a garret. And the best intellects, being thus
selected and chosen out from among their fellow-men, form
to some extent a distinct social class. Segregation is thus
effected ; and intermarriage takes place within this in-
tellectual caste, with the result that the conditions are
eminently favourable for the inheritance of intellectual
qualities.

Now, is this process of selection of the intellectual, this
segregation into a caste, and the inheritance of innate
intellectual qualities sufficient to account for the facts of
intellectual progress ; or must we call in to our aid the
inheritance of individual increments ? I confess I cannot
say. Direct and satisfactory evidence, one way or the
other, is almost impossible to obtain.

Must we, then, leave the question undecided ? I think
we must so far as direct evidence is concerned. I may
have a general belief that there has been some transmission
of acquired increment of intellectual faculty. But unless I
can substantiate it by definite facts, I cannot expect to con-
vince any one who holds the opposite view. And definite
facts of sufficient cogency I am iinable to adduce. It is
practically impossible to exclude the influence of human

Mental Evolution. 499

selection ; and unless we can do this the followers of Dr.
Weismann will not be satisfied.

Still, general belief — which means the net result of one's
consideration of the subject — counts for something. We
must remember the question is one of origin, and not of
guidance. The guidance of human selection is unquestioned
and unquestionable. But when we consider the intellectual
progress of the last three centuries, and ask whether all
this has originated in fortuitous brain-variations, which
human selection has simply picked out from the total mass
of available material, an affirmative answer seems to me a
little difficult of acceptance. There seems to have been
a definite tendency to vary in this particular direction, a
general raising of the intellectual level, which is difficult to
account for unless it be due to the persistent employment
of the intellectual faculties.

To put the matter in another way. I do not think that,
during the last three centuries, there has been a large
amount of elimination of the unintellectual. Such elimina-
tion as there has been of this nature has probably been
more than compensated by the slower rate of multiplication
of the intellectual classes. Elimination, then, in this
matter may be practically disregarded. But it is obvious
that selection, without the removal or exclusion of the non-
selected, does nothing to alter the general level * with regard
to the particular quality or faculty concerned. It is merely
a classification of the individuals in order of merit in this
particular respect. It is, in a word, a segregation-factor.
It arranges the individuals in classes, but it does not alter
the position of the mean around which they vary.

Let me explain by means of an analogous case. Fifty
boys, who have been admitted to a public school, await
examination in a class-room. They are at present un-
classified, but there is a mean of ability among the whole

* If elimination of the unintellectual (not necessarily of the unintelligent)
may be excluded, and if the unintellectual increase by natural generation
more rapidly than the intellectual, the general level of intellectuality must,
on Professor Weismann's principles, be steadily falling.

500 Animal Life and Intelligence.

fifty. A week afterwards they are distributed in different
forms. Some are selected for a higher form, others have
to take a lower place. But though selection has classified
the material, it has not altered the position of the mean of
ability among the fifty boys. This can only be done by
expelling a certain number or excluding them from the
school.

Granted, therefore, that elimination is practically ex-
cluded, human selection can at most classify the individuals
according to their intellectual faculties. It cannot raise the
mean standard of intellectuality. If, therefore, this mean
standard has been raised during the last three centuries,
there has been a tendency to vary in this particular direction,
which may* to say the least of it, be due to the inheritance
of individual increment.

I am, of course, aware that the matter is complicated
by the increased and increasing diffusion of knowledge
through the printing-press and by the extension and
improvement of education. But education, to take that
first, though it may raise the level of each generation, can
have no cumulative effect. For the effects of education
cannot, on Professor Weismann's hypothesis, be inherited.
You may educate brain and muscle in the individual, but
his heir will inherit no good or ill effects therefrom. Each
generation goes back and starts from the old level. There
is no summation of effect ; or, if there is, it tells so far
against Professor Weismann.

And with regard to the diffusion of knowledge, this,
though it brings more grist to the intellectual mill, can
have no effect in raising the mean standard of excellence in
the mill itself. There is more to grind ; but this does not
improve the grinding apparatus ; or, if it does, it tells so
far against Professor Weismann's hypothesis. To vary the
analogy, the diffusion of knowledge increases the store of
available food ; but it does not bring with it any additional
power of digesting the food; or, if it does, it may be
through inherited increments of mean digestive power.

* It may also, in part, be due to " organic combination."

Mental Evolution. 501

It may, however, be maintained that there is no con-
clusive proof that the mean intellectual level of Englishmen
to-day is any higher than it was in the days of the Tudors.
If so, of course, my argument falls to the ground. I have
no desire to dogmatize on the subject. I merely set down
the reasons, such as they are, and for what they are worth,
which lead me to entertain a general belief that the
intellectual progress* of Englishmen during the past three
hundred years has been in part due to the inheritance of
individually acquired faculty.

Mental evolution, then, is the metakinetic equivalent of
interneural, or, in us vertebrates, brain-evolution. The
brain forms a kinetic system in some sense independent of,
and yet in constant touch with, the kinetic system of the
world around. Its kineses, though they do not resemble,
yet more or less accurately represent or symbolize, the
kineses of the surrounding universe. As the kineses of
the world around are interdependent and harmonious, so
are the neural kineses of the brain interdependent and
harmonious. And no modification of this kinesis which is
out of harmony with the kinetic system already established
in the brain can be incorporated with that existing system.
Such attempted modification is eliminated through in-
congruity.

Associated with this brain-kinesis, and forming its
inner aspect, is a metakinetic system in which the higher
manifestations rise to the level of full consciousness ; others
form sub-conscious states ; others are unconscious. But
the whole form a coherent system answering to the coherent
kinetic system.

Consciousness is thus associated only with the pheno-
mena of that kinetic microcosm which we call the brain
(or other interneural system). Obviously, therefore,
it does not and cannot deal directly with anything
outside the brain. Its knowledge is solely and entirely
a knowledge of the representative occurrences of the
interneural system. But out of these occurrences a sur-

502 Animal Life and Intelligence.

rounding world of phenomena is constructed in mental
symbolism.

The brain itself, however, is part of the world of
phenomena thus constructed in mental symbolism ; and
the world, therefore, dissolves in pure idealism, leaving
only a fleeting series of states of consciousness, if we do
not assume the existence of a system of " things in them-
selves" (noumena), of which kineses and metakineses are
the phenomenal manifestations. Whether the "things in
themselves " in any sense resemble their phenomenal mani-
festations, we cannot say. It is as difficult philosophically
to conceive that they can as it is practically to conceive
that they do not. And since, whether they do or do not,
the world we live in is phenomenal ; since it is to
phenomena that we have to adapt our conduct ; since it is
with phenomena that all our thoughts and emotions have
reference ; since the world we construct in mental symbolism
is the world in which we live and move and have our
being ; it is not only convenient, but logically justifiable,
to call this world of phenomena the really existing world
for us human-folk and other sentient organisms.

As in the kinetic interneural system, or brain, so, too,
in the metakinetic system, no modification of the meta-
kinesis which is out of harmony with the existing rneta-
kinesis can be incorporated therewith. Such attempted
modification is eliminated through incongruity.

In the lower stages of mental evolution, those which
belong to the perceptual sphere, where the neuroses are
closely connected with the life-preserving activities of the
organism, the survival or non-survival of the system of
neuroses is largely dependent on the fitness of the asso-
ciated activities to the conditions of life. But in the highei
stages of mental evolution, those which belong to the con-
ceptual sphere, the connection of certain brain-neuroses
with life -preserving motor-activities becomes less close and
direct. The corresponding ideas, thoughts, and emotions
become floated off into a more abstract region. Here the
system of ideas, as such, that is to say, so far as they ar e

Mental Evolution. 503

removed from life-preserving activities, is determined
mainly by the law of congruity. But there are several
such systems. There are, indeed, as many systems as
there are minds ; but these may be classified in several
distinct groups, which we may liken to genera and species.
These are the various interpretations of nature, theories of
things, and the like ; the systems of ideas, thoughts, con-
ceptions, emotions, beliefs, which, as we say, belong to us,
each and all, and which determine to which metakinetic
species we belong. These are the highest products of
mental evolution ; and among them there is, so to speak,
a struggle, if not for existence, at any rate for prevalence.
Which shall eventually prevail — a spiritual interpretation of
nature, a material interpretation, a monistic interpretation,
or other, who shall say ? But, so far as we can judge, the
winning species among systems of ideas and interpreta-
tions of nature are likely to be those in which the greatest
number of ideas are fused into harmonious synthesis ; in
which all the ideas are congruous; and in which the
abstract or conceptual ideas, when brought into contact
with concrete or perceptual states of consciousness, are
found to be in harmony and congruity therewith.

INDEX.

Abstract ideas, 322, 363

Acceleration, sense of, 269

Acceleration and retardation, 221

Achirus pellucidus, 83

Acquired characters, are they
transmitted ? 147 ; habits, are
they inherited ? 436 ; variations
in the intellectual sphere, 497

Acrcea, 203

Activities, organic basis of com-
parative psychology, 337 ; of
animals, 415 ; voluntary and
involuntary, classification of,
462

Adaptation, analogous, 117 ;
modes of, 119; special, ex-
amples of, 179; to varying
environment, 183

Advantage must be particular,
184; must be immediate and
not prospective, 186 ; must be
"available," 188,211

Mschna, 2S9

./Esthetic preferences in insects
and birds, 207 ; aspect of sen-
sation, not primary, 243 ;
motive not present to animal
consciousness, 409

ALEXANDER, Mr. S., " Moral
Order and Progress," 463

ALLEN, Mr. Grant, on evolution
of flowers, 206 ; on pleasure
»nd pain, 380

, Mr. J. A., on colour and

humidity, 164

Alternation of generations, 46

Ambli/opsis spelceus, 271

American school of evolu-
tionists, 221

Amceha, how it feeds, 5 ; repro-
duction of, 12, 38 ; diagram of,
12 ; protoplasmic functions of,
142
Amphibia, labyrinthodont, 288

Anabolism, constructive process,
32

Analysis (mental), 321

Ancon sheep, 226

ANDHRSON, Mr., on one-eared
rabbits, 226

Anemone, sea, reproduction of,
4] ; marginal beads of, 298 ;
discrimination by, 359

Anger and rage, 3»9

Animal life, nature of, 1; di-
versity of, 177

Animal intelligence, differs
g nerically from man's reason,
350

Animals, characteristics of, 1 ;
divided into protozoa and
metazoa, 15 ; and plants, their
relation to food-stuffs, the
atmosphere, and energy, 15 ;
intelligent not rational, 373 ;
capacities for pleasure and
pain, 391

Animistic ideas of savages, how
developed, 494

Anisognathus, 226

A nom ia, 265

Ant, sauba, of South America,
213; sense of taste in, 253;
sense of smell in, 258 ; audi-
tory organ of, 267; intelli-
gence of, 357 ; activities often
described as instinctive, 425 ;
neuter insects, 440 ; Siamese,
449

Antagonism, advantages of, 394

Antennae of insects, modifications
of, 178 ; of emperor moth, 199 ;
organ of hearing in, 267 ; modi-
fied hairs of, 297

Antennule of crayfish, 259

Anthophora, 438

Anticipation, 327

Antlers of deer in illustration of
growth, 28

Aphides, absence of fertilization
in reproduction, 44

Appetence and aversion, 343,384

Apus, 46

Aquatic organisms, respiration
in, 4 ; sense of smell in, 256

ARAGO, M., observation on
turnspit dog, 404

Arctic hare and fox, 84 ; animals,
colours of, 165 ; fox, cunning
of, 366

ARGYLE, Duke of, on humming-
birds, 110

Artemia salina and milhausenii,
164

Artistic faculties and natural
selection, 484 ; products, evo-
lution of, 489

Association a tendency to inte-
gration, 183; perceptual and
mimicry, 202; and recognition
marks, 203

Ateles, 210

Atmosphere, relations of animals
and plants to, 15

Attacus, 179

Attention, 342

Attidice, 208

Auditory apparatus in man, 262

Aurelia, life-cycle of, 45
Australian mammals and others

convergent, 117
Automatic action, 415
Available advantage, 188, 211
Aversion and appetence, 343,

Baboon, experiments with, 352

Bacilli attacked by leucocyles,
439

Bacillus violaceus, 80

BAILEY, Mr. E. H. S., on taste,
251

BALBIANI on Chironomus, 137

Jialistes, 179

lUuiiF.TT, Mr. W. F., on sensi-
tive-flame experiment, 298

Barrier, geographical, 99; time,
in physiological isolation, 105

BARRINGTON, The Hon. Daines,
on song of linnet, 454

BATESON, Mr. W., on lateral
line, 252; on fishes hunting
by scent, 256 ; on smell in
shrimps, etc., 260 ; on hearing
in fishes, 264 ; on hearing in
Anomia, 265 ; on sight in
fishes, 286; on rockling and
sole, 352 ; on fascination in
fishes, 388

Bats, tabulated measurements of
wing-bones of, 65-73; wings,
fortuitous variations in, 235;
experiment with, 247

Beauty, standard of, 206; sense
of, 407

Beaver, change of habit in, 445

BECCARI on gardener bower bird,
408

BECKER, Alexander, on varia-
tions in the balance of life, 112

Bees, divergent development of,
58; cuckoo, 90; latency in,
228 ; sense of taste, 253 ; sense
of smell, 257 ; smell-hollows,
259 ; eyes and eyelets of, 289 ;
intelligence of, 357 ; colour
preferences in, 408; homing
faculty in, 428 ; neuter insects,

of Madeira, 81; stag-,
variability of male, 180; ob-
servations on dung-, 368
Begging in dogs, 345
BEUKKLEY, Bishop, quoted, 475
BEKT, M. Paul, limits of sensi-
bility to light, 296

506

Index.

BIDIE, Mr. George, anecdote of

Cattle, of Falkland Islands, 203

Construct and construction

cat, 370

Causation, 327

(mental), 312 ; three stages of,

BINET, M., "Psychic Life of

Cell, diagram of animal, 10;

324 ; inevitable nature of, 332 ;

Micro-organisms," 360

controlled explosions in, 31

in mammals, 338

Birds, influence of food-yolk on

Cessation of selection, effects of,

Continuity of reproductive cells,

development of, 56; diver-

172

131; germ -plasm, 13«; cel-

gence among, 97 ; breeding

Cluztodon, 83

lular, 142 ; in mental develop-

area of comparatively re-

Chcetogaster limncei, reproduc-

ment, 373

stricted, 101 ; humming, Duke

tion of, 42

Convergence, phenomena of, 117

of Argyle on, 110; destruction

Chaffiuch, nest of New Zealand,

Co-ordinants, 303

of eggs of, 189; game-, white

454

COPE, Prof., on the effects of use,

and black crossed. 225 ; taste

Chamaeleon, 286

210 ; and HYATT, Prof., on re-

in, 251; smell in, 256; hearing

Chance, 236

tardation and acceleration, 221

in, 264 ; sight in, 284 ; colour-

Change of conditions, 163

Correlated variation, 59, 216

vision in, 285 ; gardener bower,

Characters, specific, 110

CORTI, organ of, 263

408 ; humming, nests of, 408 ;

CHARBONNIER, Mr. Henry, mea-

Coryne, Prof. Weismann on, 139

perfect instincts of proecoces,

surements of bats, 63

COUCH, Mr., on goldfinch song,

424; love antics of satin

CHATTOCK, Mr. A. P., his ex-

454

bower, 450 ; nests of, 453 ;

periments on colour- vision,

Crab, protective resemblance in,

song of, 454

280; letter to, on dog and

87 ; hermit, 195 ; habit of

BLOCHMANN on the development

picture, 341

decking itself, 457

of the drone, 153

CHESHIRE, Mr., on smell-hollows

Crayfish, smell in, 259 ; auditory

Blood, circulation of, 22!

in bees, 259

organ of, 266

Body as distinguished from re-

Chickens' aversion to protected

Crossing, effect on reversion, 230

productive cells, 131
BOLL and KDHITE, Messrs., on

caterpillars, 352 ; perfectly i Cruelty in cat, objective, 400
instinctive activities, 424 1 Crustacea, eyes of, 292

retinal purple, 276
BOLTON, Miss Caroline, on the

C/iironamus, reproductive cells
of, 137

Ctenomys, 194
Cuckoo, the nameonomatopoetic,

bat, 247

Choice, 458

322 ; habits intelligent, 436 ;

Bombus muscorum, 90; lapi-

Circulation of the blood, 22

ejecting young birds, 437

darius, 91

Classification, 323

Curiosity in prong*horn, 339

Bombyx quercus, 258

CLIFFORD, W. K., on human

Cuttlefish, eyes of, 293

Bower bird, 408, 450

consciousness, 341 ; on the

C'yclas, 265

Brain, 31 ; decreased, of rabbits

eject, 476 ; on " world^on-

Cycloptera speculata, locust re-

and ducks, 171 ; a microcosm,

sciousness," 479

sembling leaf, 86

491

Clover and bees, 113

BREHM'S, Thierleben, quotation

Clytus arietis, 87

from, 405

Cockchafer, smell -hollows of,

DALLiNGER,Dr., his temperatnre-

Brine shrimp, modified by sa-

259

experiments on monads, 147

linity of water, 164

COCKERELL, Mr., on variations

Danais, 203

BROOKS, Prof. W. K., his modi-

in snailg, 75 ; on effects of

Daplmids, absence of fertiliza-

fication of pangencsis, 134 ;

moisture, 239

tion in reproduction of, 45 ;

on the greater variability of

Cockroach, diagram of trachea

colour - vision in, 292, 296;

the male, 237

or air-tubes of, 3; sense of

leucocvtes of, 439

BROWN, Prof. Crum, on sense of

taste in, 253 ; sense of smell DARWIN, Charles. Natural selec-

acceleration, 270

in, 258

tion and the struggle for exist-

BROWNE, Sir J. Crichton, on

Cocoon, collective, 429

ence, 77 ; divides the principle

ducks, 171

Colobus, 210

of selection into three kinds,

Budding, reproduction by, 42;

Colour, protective resemblance

78 ; on selection of flowers and

in relation to heredity, 128

in, 82 ; warning of inedibility,

fruits by insects, 93 ; on sexual

Bull, "Favourite," prepotent,

82 ; dependent on humidity,

selection, 94 ; on prevention

227 ; reversion in, 229

164; direct action of climate

of free crossing in breeding,

BUXYAN, John, on gateways of

on, 164 ; development of, 202 ;

99; on differential fertility,

knowledge, 311
BUTLER, Mr. Samuel, on organic
memory, 62, 475

blindness, 273, 279; pheno-
mena of, 278
Combination, organic, hypothesis

104; on London rats, 106; on
Galapagos archipelago, 109;
on diverse adaptation, 111 ; on

Butterfly, protective resem-

of, 150, 240

the influence of old maids on

blance in, 86 ; mimicry in, 87

Communication in dogs, 345 ; in

clover crops, 113; on the in-

bees, 358

fluence of parent on offspring,

Camel, wounded, 392

Compensation of growth, 155

122 ; on the co-ordinating

Canary, crested, 225 ; nest build-

Competition, elimination

power of her organization, 1 25 ;

ing of, 453

through, 89

hypothesis of pangenesis, 131 ;

Capon, taking to sitting. 228

Concept, 325, 326

on fur of arctic animals, 165 ;

Capuchin monkey, Miss Ro-

Conception, 325

changes of structure attributed

manes's observation on, 367 ;

Conceptual conduct and evolu-

to use and disease, 171 ; on

sympathy in, 397

tion, 488

blindness of tuco-tuco, 194 ;

CARLYLE, quoted, 331, 335

Condor, rate of increase of, 57

on the principle of economy,

Carp at Potsdam, 265

Conduct, 463 ; influence of

194; on sexual selection, 198 ;

CARTER, Dr. Brudenell, quoted,

thought and aesthetics on, 483 ;

on preferential mating, 204;

285

conceptual, and natural selec^

on evolution of flowers, 205 ;

Caste, idea of, in dog, 400

tion, 488

on co-ordinated variations in

Cat, effect of African climate on,

Congruity, principle of, 486

the elk, 213 ; on acceleration,

164 ; defining its percept, 339 ; Conjugation in protozoa, 39 ; of

222 ; on ancon sheep, 226 ; on

communication, 345 ; intelli- ovum and sperm-cell, 42

prepotency, 227 ; ou re version,

gence of, 370 ; and mouse, Consciousness, 32 ; and consenti-

229 ; on the effects of crossing,

399 ; punishing kitten, 405

ence, 326, 362 ; as a criterion

230 ; on fortuitous variation.

Caterpillars, protective resem-

of instinct, 432

236 ; on the subordination of

blance in, 82

Consentience, 326, 362

the conditions to the organism,

Index.

507

236 ; on the greater variability

Dromia vulgarin, 457

Expectation, 327

of male, 237 ; on attention in

Drones developed from unfer-

Experience dependent on me-

monkeys, 342; on brain of ant,

tilized ova, 45 ; second polar

mory, SOS

358 ; oil gestures of anger and

cell extruded, 153

Expression of the emotions, 385

rage, 389 ; on pleasures and

DUBOIS, M., on Proteus, 294

Eye, structure of in man, 274 ;

pains of animals, 394 ; on

Ducks, '.Sir J. Crichton Browne

in mole, 284 ; pineal, 287 ; in

bravery of a monkey, 396 ; on

on, 171 ; Dr. Rae on instinc-

insects, 288 ; facetted, 289 ; in

Abyssinian baboons, 405 ; on

tive wildness of, 435

Crustacea, 292 ; in molluscs,

sense of humour in the dog,

Duration of life, 186

292 ; four types of, 294

406 ; on neuter insects, 440 ;

on selection of oxen, 441 ; on

Eagle, sclerotic plates of, 437

acquisition of fear of man by

Ear, 263

FABRE, M., on Sitaris, 439

birds, 443 ; on satin bower

Earthworm, respiration In, 4,

Facetted eye, 289

bird, 450

24 ; regeneration of lost parts,

Factors of phenomena, laws of,

Death, natural introduction of,

41 ; sensitive to light, 293 ;

61

18H, 193

outward projection in, 359

Falkland Islands, cattle of, 102 ;

Deceit in dogs, 400
Degeneration, 183

EATON, Rev. A. E., on insects of
Kerguelen Island, 81

birds of, 443
Fear, dread and terror, 387 ; in-

Desert animals, inoonspicuous-

Ecitons, 427

stinct of, 443

ness of, 89
DESCARTES on pineal gland, 288

Economy, principle of, 194
Education of ants, 428 ; of young

Feelings of animals, 8, 378
Female. See Sex-differentiation.

Desire, 460, 463

animals, 455

Female and male insects, differ-

Destruction, indiscriminate, as

Egg and hen, problem of, 130

ences between, 179; vigour

opposed to elimination, 76
Development of organisms dis-

Egg-cell and sperm-cell, diagram
of, 13 ; conditions which deter-

expended on offspring, 238
Fertilization, nature of, 42 ; ab-

tinct from growth, 6 ; repro-

mine production of, 60

sent in parthenogenetic forms,

duction and, 36 ; is differential

Eggs, influence of food-yolk on

44

growth, 49 ; of a vertebrate,
diagrammatic account of, 51 ;

mode of development of, 56 ;
destruction of birds, 189

Fertility, differential, Darwinand
Romanes on, 104 ; of hybrids,

comparative, of some verte-

Ego, or self, 475

105

brates, 220

EIHER, Prof., on inhabitants of

Fetishism, its natural genesis,

DE VRIES, 132, 159

Nile valley, 165; on Helix

492

Differentiation in protozoa, 40;

hortensis, 226 ; on instinct,

FISCHER, Dr. Emil, on smell, 254

in metazoa, 41 ; during de-

436 ; on differential dread in

Fish, respiration in, 24 ; protec-

velopment, 49 ; of reproduc-

birds, 444

tive resemblance in, 83 ;

tive cells, 143; and integra-

Eject, meaning of, 476

amount of food-yolk in eggs

tion, 183 ; of tissues, 232

Elaboration, 183

of, 220 ; skate and turbot com-

Difflugia, 360

Elephant, rate of increase of, 57 ;

pared, 220; sense of taste in,

Dimorphism in larvae, 187

intelligence of, 363, 369; use

252 ; sense of smell in, 256 ;

Discrimination in the sense of

of tools by, 370 ; vindictive-

sense of hearing in, 264 ; sense

touch, 245; hearing, 262;

ness in, 401

of sight in, 286 ; fascination in,

sight, 275 ; its fundamental

Elimination, as opposed to selec-

388 ; love-antips of, 450

nature, 338 ; in sea-anemone,

tion, 79 ; its three modes, 80 ;

FISK, Rev. G. H. R., on sym-

359

as a factor in the origin of in-

pathy in cat, 397

Disease, elimination by, 80

stinct, 447 ; of ideas through

Fission, a process of cell-division,

Display, 207
Disuse, panmixia and, 189 ; ne-

incongruity, 486 ; as applied
to the intellectual faculties, 497

37 ; in protozoa, 38 ; in meta-
zoa, 41

gative and not positive, 196 ;

Embryology negatives pre forma-

Flight, instinctive nature of, 425

use and, 209

tion, 50

FLOURENS, M., on function of

Divergence among birds, illus-
trated from Wallace, 97 ;

Emotions exemplified, 382; the
expression of, 385 ; three orders

semicircular canals, 269
Flowers and fruits, selection of,

through diverse adaptation, 111

of, 391 ; in vertebrata, 395

93; evolved through insect

DIXON, Mr. Charles, effects of

Encystment, 38, 49

agency, 206

climate on the colours of birds,

Ends and means, 371

Folliculina, 360

164 ; on chaffinch nests, 454

Energy, relations of animals and

Food-stuffs, relations of animals

Dog, effect of Indian climate

plants to, 16

and plants to, 15; nature of

on, 164, 167 ; greyhounds in

Ennomos tiliaria, caterpillar,

and digestion of, 25

Mexico, 167 ; sense of smell

protective resemblance of, 85

Food-yolk, influence of, on de-

in, 255, 338 ; vague percept of,

Environment, direct effects of on

velopment, 55 ; the result of

339 ; and the feelings of other

the organism, 163 ; changes of,

parental sacrifice, 67

animals, 340 ; and pictures,

in relation to the organism,

FORBES, H. 0., on Javan spiders,

341 ; powers of communica-

183 ; are effects of direct or

90

tion, 344 ; swimming rivers,

indirect? 233; instances of

FOREL, M., on taste of ants, 253 ;

365 ; cleverness of, 367 ; sym-

effects of, 238

on vision of daphnids, 296 ; on

pathy in, 397 ; idea of caste,

Equus. 118

happy family of ants, 428

deceit, 400 ; endurance of pain, Eristalis lenav, 87

Form-characteristics of animals,

402 ; sense of justice in, 404 ; Ethics in animals, 413

2

punishing pup, 405 ; sense of | Euplcea, 203
humour in, 406 ; swimming a Evolution of older writers, 50 ;

Fortuitous variation, 235
Fosterage and protection, 219;

deferred instinct in, 423 ; turn- 1 and revolution, 119; organic.

result of female self-sacrifice,

ing round to make a couch, 444 | 177: meaning of term, 182;

238

Dog-lish, sense of smell in, 257 mental, 464 ; organic and men-

FOTHERGILL, Mr., on dogs swim-

Domestication, variations effected tal not continuous, 488 ; inter-

ming rivers, 364

by, 171, 215; crossing and re- neural, 490

Fowl, variations in, attributed by

version, 230 Excrement of birds, resemblance

Darwin to use, 171; crossing

Doris tuberculata, 84 i of spider to, 90
Dreaming, 341 ; and the animis- • Excretion, an essential life-pro-

of, 227, 230
K*>x, cunning of, 366

tic hypothesis, 495 | cess, 3, 29

FRANCIS, Mr. H. A., 90

5o8

Index.

FRITSCH, Dr., Fig. of skull of

Melanerptton, 288
Frog, development of, 6 ; arrest

of life in, 21; respiration in,

24 ; fishing, or angler-fish, 91 ;

modified development of, 214 ;

effects of simple stimulus on,

305
Fruits and flowers, selection of,

GABET, Messrs. H0c and, on
Llama cow, 333

Galapagos Archipelago, species
and varieties in, 99 ; climate
of, 109

Gattus banfciva, 230

GALTON, Mr. Francis, on the
coloration of the zebra, 84;
his modification of pangenesis,
135 ; numerical estimate of in-
heritance, 150, 192 ; his inves-
tigations on twins, 169; on
blended characters, 225; on
the steps of evolution, 227

Ganglia, 31

Gannet, rate of increase of, 57

Gas-engine, analogy of, 30

GACTIER, Theophile, his cat, 264

GEDDES, Prof. Patrick, and THOM-
SON, J. A., on anabolism and
katabolism, 44; quoted, 50,
137, 237

Gemmules, pangenetic, 131

Generations, alternation of, 46

Generic idea, 326

Geographical barriers a means
of segregation, 99

Geological changes, influence on
natural selection, 113

Germ-plasm, continuity of, 138 ;
convenience of, 140

Gills of mussel, 4 ; as respiratory
organs, 24

Giraffe, co-ordinated variations
in, 212

Glacial epoch, effects of, 113

Gland, pineal, 288

Goldfinch, song of, 454

GOLDSCHNEIDER, on tempera-
ture-sense, 249

GOCLD, Dr., on humming-birds'
nests, 408

GRABER, Dr., on colour-sensitive-
ness of earthworm, 293

GRANT, Mr. G. L, on New Zea-
land sparrows, 445

Grasshopper, auditory organ of,

Gregarina, reproduction in, 38

GRENACHER, Dr., experiment on
moth's eye, 290

Grouse, white plumage in, due
to reversion, 229

GROVE, Sir W. R., on antago-
nism, 394

Growth of organisms, 5 ; illus-
tration of a deer's antler, 28 ;
law of, after mutilation, 126

Guidance distinguished from ori-
gin, 242

Guillemot, eggs of, 410

GLLICK, Rev. J. T.,on landshells
of Sandwich Islands, 109; on
tendency to divergence, 151

GI-PPT, Mr., on crab of Solomon
Islands, 87

Habits of animals, 415

Habitual activities, 420; sense
of satisfaction in performance
of, 421

HAECKEL, Prof., plastidules of,
125 ; theory of perigenesis, 159

Halictus cylindricus, 90

HAMERTON, Mr. P. G., on the
ignorance of animals, 333

HAMILTON, Sir Wm., quoted, 470

HANCOCK, Mr. John, on instinct
of cuckoo, 437

HASSE, E., on humble-bees, 259

HAUSER, on cockchafer, 259

HAYCKOFT, Mr. J. B., on taste,
250

Hearing, sense of, 261

Heliconia,203

Helix, nemoralis and hortensis,
variation of, 75, 217, 226, 239

HELMHOLTZ, Von, on colour, 277 ;
on local signs of retina, 308

Hen and egg, problem of, 130

HENSEN, on shrimps, 266

HERBERT, Prof. T. M., quoted,
471

HERDMAN, Prof., on sea-slug
(Doris}, 84; his modification
of pangenesis, 135 ; on warn-
ing coloration in nudibranchs,
252

Heredity, an organic application
of the law of persistence, 62 ;
and the origin of variations,
122; in protozoa, 123; and re-
generation of lost parts, 124;
failure of, 192; and instinct,
435

BERING, Edward, on organic
memory, 62, 475

HERON, Sir R., on crossing rab-
bits, 225

HEKSCHELL, Sir John, on colour,
277

HERTWIG, Richard, observations
on Infusoria, 39

HICKS, on Capricorn beetle, 267

HICKS' organ, 267

HICKSON, Dr., Fig. of eye of fly,
290

Hipparion, 118

Hippopotamus, instinctive acti-
vities in, 423

HOLLAND, Sir Henry, on inheri-
tance, 223

Homing faculty of bees. 428

Horse, two different evolutions
of, 118 ; effects of use on digits
of, 210 ; sense of pain in, 392

HOWSE, Prof., antennule of cray-
fish, 259

HUBER, Pierre, on smell in bees,
257; judgment and instinct,
452

Hue and GABET, Messrs., on
Llama cow, 333

HUGGINS, Dr., his dog Kepler,
396

Humming-birds, 110

Humour, sense of, in dog, 406'

HI-XLEY, T. H., on limitation of
variations, 151 ; on neurosis
and psychosis, 465

HYATT, Prof., on acceleration and
retardation, 221

Hybrids, fertility of, 105

Hydra, reproduction of, 14, 41 ;
diagram of, 43; artificial divi-

sion of, 124: budding in, 128;

sexual reproduction of, 129
Hydra tuba, and medusa of aure-

lia, 45
Hydroids, development of, 46;

Weismann on, 139
Hymenoptera, antennary struc

turesof, 297; instincts of social,

441, 448

Ichneumon fly, instinct of, 430
Ichthyosaurus, pineal eye of, 288
Icterida, 454
Idea of an object, 313
Ideas, conceptual, their environ-
ment, 485 ; the law of their
evolution, 486
Idealism, 474
Ignorance of animals, 333
Image, inverted in retina, 311
Imagination, constructive, 325
Imitation as a factor in habit or

instinct, 443, 453
Immortality of protozoa, 12
Incongruity, elimination by, 486
Increase, law of, 58
Incubation, instinct of, 434
Individuality, a tendency to dif-
ferentiation, 183
Inference, conscious and uncon-
scious, 328 ; in animals, 36 L
Infertility of isolated forms, 103
Infusoria, reproduction in, 39
Inheritance, exclusive, a means
of isolation, 104 ; of variations,
223 ; of acquired habits, 435 ;
of acquiied increments of in-
tellectual faculty, 497
Inhibition, 385; as a condition of

volition, 459

Innate capacity, 422 ; its impor-
tance, 429

Insects, tracheal respiration of,
3, 24; wingless, of Madeira,
81 ; of Kerguelen Island, 81 ;
mimicry and protective re-
semblance in, 85, 88 ; segrega-
tion by colour, 101; antennas
of, 178 ; mouth-organs of, 179 ;
and the evolution of flowers,
206; sense of touch in, 248;
taste in, 253 ; smell in, 257 ;
hearing in, 266 ; sight in, 283 ;
perceptual powers of, 357 ;
neuter, 440

Instinct and available advantage,
211; consideration of, 415;
perfect, imperfect, and incom-
plete, 422 ; deferred, 423 ; blind
prevision in, 429 ; gratification
in performance of, 430 ; con-
sciousness and, 432; primary
and secondary, 434 ; three
factors in the origin of, 447 ;
as influenced by intelligence,
452; by imitation, 453; by edu-
cation, 455 ; as distinguished
from intelligence, 457
Instinctive emotion, 390, 395
Integration and differentiation,

183

Intellectual development, 486
Intelligence involved in selec-
tion, 95; distinguished from
reason, 330, 365 ; lapsed, 435
involved in instinct, 440; as
influencing instinct, 452; cri-
teria of. 456

Index.

509

Interbreeding and intercrossing,

Life-area, expansion and con-

Mathematical faculty and natural

97

traction of, 114

selection, 484

Interneural evolution, 490

Limits of vision, 281 ; of sensa-

MADPAS, M., observations on

Interpretations of nature, genera

tion, 299

infusoria, 39

and species of, 492

Limnceus truncatulus, 48

MATER, on mosquito, 267

Isle of Man, tortoiseshell butter-

LINCECUM, Dr., on habits of

McCooK, Dr., sense of smell in

fly of, 81

Texan ants, 425

ants, 258; habits of Texan

Isolates, 322, 364

Linnet, song of, 454

ants, 425

Isolation, organic, or segregation,

Lion, observation on, 400

McCosH, Dr., quoted, 391

99 ; mental, or abstraction, 322

Liver-fluke, life-history of, 47

Means and ends, 371

Local signs, 308

Medusa, 46 ; sense of hearing in.

Localization, 307 ; in animals,

265 ; eyes of, 293 ; localization

JAEGER, Dr., on crossing of pigs,

230

338 ; in medusa, 359
LOCKE, on difference between

by, 359
Melanerpeton, 288

JENKINS, Mr. H. L., on the
elephant, 363
Judgment, 330

man and brute, 349
Logos makes man human, 375
LONBIERE, on instincts of Siam-

MELDOLA, Prof. R., 239
Memory, the revival of past
impressions, 304 ; organic,

ese ants, 449

Butler and Hering on, 62

LOTZE, quoted, 379

Mental evolution, 464

Kallima paralecta, leaf-butter-

LUBBOCK, Sir J., "Senses of
Animals," 246 ; sense of smell

MERCIER, Dr. Charles, on the
criteria of intelligence, 456

fly, 86
KANT, quoted, 476
Katabolism, a disruption or ex-

in ants, 258 ; auditory organ
of ant, 267; on Hicks's organ,
267 ; on colour-sense in dog,

MERRIFIELD, Mr., experiments
on moths, 238
Metabolism, 32

plosive process, 32
Kea, of New Zealand, 446
Keimplasma. See Germ-plasm
Kentish plover, 83, 217
Kepler, Dr. Huggins's dog, 396
Kerguelen Island, wingless in-

283; in insects, 291 ; in Daph-
nia, 292 ; on limits of colour-
vision, 296 ; on antennary
structures in hymenoptera,
297 ; on power of communica-
tion in dog, 345; in ants, 358 ;

Metakinesis, 467
Metamorphosis and transforma-
tion, 7
Metaphyta, 15
Metazoa, 15
Methona, 87

sects of, 81

on colour preferences in bees,

MIALL, Prof., Fig. of touch-hair

Kinesis, 467
Kingfishers, 446
KIRBT and SPENCE, localization

407 ; on instinct of play and
sympathy in ants, 414; on
homing faculty in bees, 428 ;

of an insect, 248
Mice, white and grey, crossed,
225

of smell in insects, 258; on

on sitaris, 439

Microbes, elimination among, 80

hearing in a moth, 267 ; on

Lucanus cervits, 180

Micrococcus prodigiosus, 81

instinct of ichneumon fly, 430
Kittens, instinctive antipathy to

Ludicrous, sense of, in dog,
406

Microstomum lineare, reproduc-
tion in, 42

dog, 396
KLEIN, Mr. S., on Bornbyx quer-
cus, 258

LTJMSDEN, Sir Harry, on part-
ridges, 398

Mimicry, 87 ; as evidence of per-
ceptual association, 202, 351

KCHNE, Messrs. BOLL and, on
retinal purple, 276

of Darwin, 121

Mineral crystals, analogy of,
240

MITCHELL, James, his delicate

MACH, Prof., on Macuta acustica,

sense of smell, 255

Labyrinthodont amphibia, pineal

271

MFVART, Prof. St. George, on

eye in, 288

Machetes pugnax, 110, 178

Saturnia, 163 ; on common-

LAMONT, on reindeer, 392

MACKENNAL, Mr. Alexander, ob-

sense realism, 316; on ideas,

LANE, Dr. Arbuthnot, on in-

servation on a cat, 405

etc., 326 ; on " practical intel-

fluence of certain trades on

MACLAGAN, Miss Nellie, on sym-

ligence," 362; on man and

structure, 169

pathetic action in dog, 398

brute, 374 ; on consciousness

LANGLET, Prof., on atherial vi-

Madeira, wingless insects of, 81

and oonsentience, 461

brations, 299
Language, 322; the instrument

Malei See Sex-differentiation
Male and female insects, differ-

Modifiability of individual organ-
ism, 163

of analysis, 349 ; its origin

ences between, 179; greater

Modifications of antennae and

and effects, 374
LANKESTER, Prof. E. Ray, his

variability in, 237 ; vigour and
vitality of, in secondary sexual

mouth-organs of insects, 178
Mole, eye of, 284

description of perigenesis, 159 ;

characters, 237

Mollusks, variety of, 178 ; sense

on blind cave-fish, 194

MALLE, Dureau de la, on star-

of smell in, 260 ; hearing in,

Lapsing of intelligence, 435

ling, 455

265; sight in, 292

LARDEN, W., on the Rhea, 89 ;

Mammals, respiration in, 21 ;

Monads, reproduction of, 38 ;

on instinct in a snakelet, 424
Larmarckian school, 209

early nutrition of, the result
of parental sacrifice, 57 ; con-

temperature experiments with,
147

Larvse, dimorphism in, 187

vergence in, 117 ; senseof smell

Mongrelization, 168

Latency, phenomena of, 227
Lateral line of fishes, 252
Leaf-butterfly, 86

in, 255; hearing in, 263; sight
in, 283 ; perceptions of, 338
Man, elimination by physical

Monistic hypothesis, 465
Monkey, ateles and colobus digits
of, 210 ; examining marsupial

LEE, Mr. Arthur, on communi-

circumstances, 81 ; alternation

pouch, 340; attention in, 342;

cation in cat, 345

of good and bad times, 117;

capuchin, intelligence of, 367

Leptalis, 87

reversion in, 229

Monospora biscuspidata, 439

LEROT, on abstract notion of

MANN, Mrs., on sympathetic

MOORE, Mr. Thomas, on hybrids

danger in fox, 348

action of dog, 397 ; anecdotes

between Amherst and golden

Leucocytes, role of, 439

of dogs, 406

pheasants, 106

LEWES, G. H., 437, 462

Mantis, protective and aggres-

Mosaic vision, 291

LETDIG, on antennule of cray-

sive resemblance in, 90

Mouth-organs of infects, 179

fish, 259

Marsupials of Australia, 117

Muciparous canals of fishes, 298

Life, duration of, due to natural

MARTINEAU, Dr., on wants, 382

MILLER, Prof. Max, "Science of

selection, 186

Materialism, 464, 471

Thought," 325; on percepts,

Index.

375 ; on language and thought,

Oyster-embryo set free early, 56 i l phalus mystaceus, 90; on

376 ; paraphrased, 467 ; on

variation of Mediterranean, 164

caterpillars and chrysalids,

materialism, 471

165; dimorphism in larvae,

Murex, 292

187 ; observations on edibility

JUus rex and imperator, 100

Pachyrhyncus orbifex, 87

of caterpi liars, 212; " Theories

Musical and artistic faculty, 484

Pagurus prideauxii, 457

of Heredity," qutotation from,

Mussel, freshwater, gills of, 4 ;

Pain, massive and acute, 379 ;

214; on the eating of un-

olfactory organ of, 260

capacities of animals for, 391

palatable insects, 445

Mutilation, law of growth after,

Pangenesis, 182

Predominant defined, 349 ; and

126 ; not the best kind of evi-

Panmixia and disuse, 189

language, 374

dence of transmitted modifica-

Papilionidce, 202

Preferential mating, a means of

tions, 162

Paradise, birds of, 202

segregation, 102 ; and sexual

Paranucleus in protozoa, 39

selection, 197

Paramcecium, reproduction in, 39

Preformation and evolution of

NAEGELI, 159

Parasites, how they feed, 5

older writers, 50

NAISH, Mr. John G., on the

Parental sacrifice in birds and Prepotency, 227

cockatoo, 354

mammals, 57 ; its litnita, 186 Presentations of sense, 318

Natural selection, variation and,

Parrot, intelligence of, 353

Previous sire, effect of, 168

61 ; two modes, elimination

Parthenogenetic forms, no

Prevision as a criterion of intel-

and selection proper, 79 ; and

second polar cell in, 153 ; the

ligence, 457

the effects of use and disuse,

drone an exception, 153

Principles, mechanical, 368

174 ; not to be used as a magic

Parus palustris, 164

Process of life, 20

formula, 184; and instinct,
445 ; and human thought, 484

PEAL, Mr. S., on use of tools by
elephant, 370

Progress, or continuous adapta-
tion, 119; adaptation to more

Nerves, briefly described, 246;

PECKHAM, Mr. G. W., on love*

complex circumstances, 183

afferent and efferent, 303

antics of a spider, 208, 450

Pronghorn, curiosity in, 339

Nestor notabilis, 446

Pecten, 293

Proposition, 329

Nests of bower-bird and hum-

Pelagic animals, colours of, 83

Protective resemblance and

ming-bird, 408; instinctive

PEXZOLDT, Dr., on smell, 254

mimicry, 82; general resem-

building of, 453

Percept, 325, 326

blance, 83 ; variable resem-

NETTLESHIF, Mr., on a lion, 400

Perception, 31 1,324; in animals,

blance, 84; special resem-

Neural processes, environment

339

blance, 86 ; to another

of, 491

Perceptual association, 202

organism, 87 ; coloration, a

Neurosis and psychosis, 465

Perigenesis of the plastidule, 159

means of segregation, 101

Neuter insects, 440

Peripatus, 142

Protection, fosterage and, 219

New Zealand sparrow, 445;

Persistence, law of, 61

Proteus, sensitive to light, 294

parrot, 446 ; chaffinch, 454

Pheasant, hybrids between Am-

Protista, 15

NICHOLS, on taste, 251

herst and golden, 106; golden,

Protohippus, 118

Noctule, 66

hen with cock's plumage, 228

Protophyta, 15

NOIKB, on concepts, 325

Phenqodini, 223

Protoplasm, 10

Jornada solidaginis, 90

Phenomenal nature of object,

Protozoa, nature of, 15 ; trans-

NORRIS, Mr. W. E., quoted, 420
Noumena, or " things in them-

315, 320, 331
Photographic psychology, 320,

mission of acquired faculty in,
147 ; origin of metazoan varia-

selves," 470

326

tions in, 156 ; psychology of,

Nucleus of animal cell, 10 ; as

Phrynocephalui mystaceus, 90

360

controlling formative process
in, 124

Physiological isolation, 104
Physiological and psychological

Psithyrus rupestris, 90
Psychological and physiological

Nutrition in illustration of the

activities, 304; series, 386,417

activities, 304 ; series, 386, 417

process of life, 25

PICTON, Mrs. E., on Skye terrier,

Psychoses and neuroses, 465

398

Ptarmigan, on colour of, 165

Pigeons, correlated variations in.

Object, nature of, 313, 437

216; silky fantail prepotent,

Ocelli in insects, 288

227

Rabbit, brain of, 171; Angora

Oecodoma cephalotes, 213

Pigs, intestines of, 171 ; cross-

crossed, 225 ; one-eared, 226 ;

Onchidium, 293
Optogram, 276

ing of, 226, 230
Pike, teeth of, 437

deprived of long lip-hairs. 247 ;
papilla foliata of, 250 ; effects

Organic combination, hypothesis Pineal gland, 196, 288
of, 150, 240 j Pipistrelle, wing of, 64

Organic evolution, 177 ; as basis , Pipits as illustrating divergence,
of comparative psychology, I 97
336 Pitch, musical, 261

Organic growth, 5 j Plasm, 10

Organism, unity of, as regards Plasmogen, 10
body and germ, 161 ; relation Platyglossus, 83
of, to environment. 183 > Play, instinct of, 450

Organization, co-ordinating Pleasure and the special senses,
power of, 125 ; of bodily and 243 ; massive and acute, 379 ;
mental activities, 419 capacities of animals for, 391

Origin, distinguished from guid- Plecotus auritt,

Plesiosaurus, pineal eye of, 288
PLOSS, Herr, on sex-differentia-
tion in man, 59

ance, 242

Origin of species, 242
Origin of organic variations, 231 ;

of metakinetic or mental varia- Plover, Kentish, 83, 217

tions, 496 I Polar cells, extrusion of, 51 ; and

Ornithoptera. 179 variation. 153

Otoliths, 265, 271 Postponement of action, 385

OWEN, Sir Richard, suggested POULTON, Mr. E. B., on colours

germinal continuity, 135 | of animals, 84 ; on Phrynoce-

of superabundant food on, 394

RAK, Dr., on dogs swimming
rivers, 364; on "abstract
reasoning " in the fox, 366 ; on
wild and tame ducklings, 435

Rage and anger, 389

RAMSAY, Dr. Wm., on smell, 255

Rats of Solomon Islands, 100;
of the London Docks, 106 ; at
South Kensington, 115

RAYLEIGH, Lord, on colour-blend-
ing. 283; on sensitive-flame
experiments, 298 ;

Reality, meaning of term, 314

Reason distinguished from intel-
ligence, 330, 365; as defined
by Mr. Romanes, 372

Recepts, 326, 368

Kecognition-marks, 103; involve
perception, 351

Reconstructs and reconstruction
(mental;, 318

Index.

Reflex action, 415 ; and instinct,

RUSSELL, Mr. W. J., on smell

SOLLAS, Dr. W. J., on regenera-

422

in the dog, 255

tion of tentacle in snail, 127

Regeneration of lost parts, 41 ;

Somatic, or body-cells, 193

in relation to heredity, 124;

Son MERINO, Fig. of semicircular

law of growth concerned in.

ftaitis pulex, 450

canals, 270

126

Salinity of water, effects of, on

SPALANZANI, his experiments on

Reindeer wounded, 392 ; change
of habit in, 445

brine-shrimp, 161
Salmon, new variety of, in Tas-

bats, 248
SPALDING, Douglas, on instinc-

Remnants or vestiges, 196

mania, 99

tive emotions, 395 ; on perfect

Reproduction, nature of, 13;

Saturnia, modification of, by

instincts of chicken, 424 ; on

and development, 36 ; in the

changed food, 163 ; carpini

deferred instinct in swallow,

protozoa, 3s ; in the metazoa,
41 ; by budding, 42 ; sexual,

(emperor moth), 258
Savages, fetishistic belief in, 494

425
Sparrows in New Zealand, 445

42 ; peculiar modifications of,

SCHAUB, Mr., observations on a

Specific characters, utility of,

45 ; developmental, 143

terrier, 405

110; constancy of, 111

Reproductive cells, continuity

SCHMA.NKEWITSCH on Artemia,

SPENCER, Mr. Baldwin. Fig. of

of, 131

164

pineal eye, 288

Resemblance, protective, 82 ;

SCLATER, Mr. W. L., on mimicry

SPENCER, Mr. Herbert, law asso-

aggressive, 90

in an insect, 88

ciated with his name, 37 ; phy-

Respiration an essential life-

SEDGWICK, Mr. Adam, on de-

siological units, 125, 153; on

process, 3 ; in illustration of

velopment of peripatus, 142

lap-dogs, 195 ; on the Irish elk

the process of life, 21
Retardation and acceleration, 221

SEEBOHM, Mr. H., on birds' eggs,

and giraffe, 212; on diminution
in ear-muscles, 215; definition

Retina of man, 274 ; of birds, 284

Segregation, 99

of pleasure and pain. 38J ; on

Retinal purple, 276

Selection, as compared with eli-

aesthetics, 412; on instinct and

Revenge, 4ul

mination, 79; illustrated, 92;

reflex action, 422

Reversion, 191

artificial, 172; cessation of,

Sperm-cell and egg-cell, 13 ; con-

Revolution and evolution, 119

190; reversal of, 193; sexual,

ditions which determine pro-

Rhea, neck resembling snake, 88

or preferential mating, 197,

duction of, 60

Rhinolophus ferri-equinum,

452 ; as a factor in the origin of

Sphex, instinct of, 429, 456

hipposidt-ros, 65
Rhyme-association in parrot, 356

instinct, 447 ; as applied to the
intellectual faculties. 498

Spiders, hunting, mimicry in, 89 ;
Javan, Mr. H. 0. Forbes on,

RIBOT, M., on attention, 343 1 Selenia, illunaria, and illus-

90; love-antics of, 208, 450;

RICHAHDSON, Mr. Charles, on traria, 238

ocelli of, 289

railway servants killed by ' Self, the, or ego, 475

SPINOZA, quoted, 61, 379, 460

train, 388 Self-consciousness, 460

Sponges, reproduction of, 41, 42

RILKY, Prof., on Phengodini, 223 Semicircular canals, 262, 269

SiJongilla, reproduction of, 46

ROMANES, Prof. G. J., on physio- Senility, introduction of, 184

Spore-formation, reproduction by,

logical isolation, 104; on the

Sensation defined, 305, 324

38

cessation of selection, 190; on

Sense-feelings of animals, 393

Squirrel of Sarepta, 113

the failure of heredity, 192;

Senses of animals, 243-; organic

Stag-beetles, variation in males

on the reversal of selection,

and muscular, 244 ; touch, 245;;

of, 180

193 ; on sense of smell in dog,
on colour-sense in chimpanzee,
283 ; on ideas, 326 ; on dog

temperature-sense, 249 ; taste,
250; smell, 253; hearing, 261;
sight, 272 ; contact and telces-

Star-fish, embryo set free early, 56
Starling, modified song of, 455
ST. JOHN, observations on a re-

cowed by noise, 340; on ab-

thetic, 249 ; problematical, 297

triever, 400

stract ideas in animals, 348 ;

Sensibility, 3»5; variations of,

Stenorhynchus, 457

on parrot, 353 ; on localization

449 '

Sterility, how developed, 108

and discrimination, 359 ; ex-

Sensitive, special use of the term,

STEWART, Mr. Duncan, on sym-

amples of animal intelligence

9

pathy in cat, 398

considered, 362; on abstract

Sensitiveness and sensibility, 385

Stimuli, 302

ideas in the capuchin, 368;

Sentiments, 391 ; in animals, 403

STRANGE, Mr., on love-antics of

definition of reason, 372 ; on

Sex-differentiation, 58 I satin bower-bird, 450

strange attachments in birds,
396 ; on some emotions in

Sexual union of ovum and sperm Striped ancestor of Equidae, 230
a source of variations, 149; Struggle for existence, 79; varia-

animals, 400 ; on endurance of

characters, secondary, 197 ;

tions in the intensity of, 112

pain in dogs and wolves, 402 :

selection, 197

STURGE, Miss Mildred, on the

on sense of humour in dog,

Shame in monkey, 402

parrot, 355

4o7 ; on indefinite morality in

Sheep, YOUATT on, quoted, 455

Stylonichia. observations of M.

animals, 413; definition of

Shells, land, of Sandwich Islands,

Maupas on, 39

instinct, 422 ; on education of

99

SULLY, Mr. James, on concepts,

ant, 428 ; on homing faculty
of bees, 428 ; on consciousness

SHIPP, Captain, experiment on
an elephant, 401

325 ; on propositions, 3^9 ; on
judgment and reason, 330 ; on

and instinct, 432 ; summary

Sight, sense of, 272

emotion, 390 ; on sesthetic sense

of his conclusions on instinct.

Sitaris, instinct of, 438

of beauty, 411

434 ; on instincts of Siamese

SKKRTCHLEY, Mr. S. B. J., on

SUTTON, Mr. Bland, on hen phea-

ants, 449; his psychological

leaf-butterfly, 86

sant like the male, 228 ; on the

scale, 478 ; on the world as an

Slave-making ants, 425

action of leucocytes, 439

eject, 479

Smell, sense of, 253

Swallow and swift, convergence

Rotation, sense of, 269

Smerinthus ocellatus, 165

in, 117 ; cliff, of United States,

Rotifers, absence of fertilization

SMITH, Mr. G. Munro, on elimi-

445

in reproduction, 45

nation among microbes, 80

SWAYNE, Mr. S. H., on the ele-

Roux, on extirpation of cleavage-

Snail, variations in banding of

phant, 369

cell of frog's egg, 214
EOWBLL, G. A., on " Beneficent

shells, 75; sense of smell in,
260 ; auditory sac, 265 ; eye of,

Symbolic nature of mental pro-
ducts, 314

Distribution of Pain," 392

292 ; spiculce amoris of, 459

SYMONDS, Mr. J. A., on " world-

Ruffs, variability of males, 110,

Snakes, mimicry in, 88

consciousness," 478

178

Snipe, drumming of, 448

Sympathy in animals, 397

512

Index.

Tameness, instinctive, 435

area, 113 ; effect of good times

Warning-coloration, 82 ; in-

TANNER, Miss Agnes, on a thrush,

and hard times on, 114 ; here-

volves perception, 351

398

dity and the origin of, 122;

WAHREJT, Mr. Robert Hall, a

Tasmanian salmon, 99

a source of, in use and disuse,

dog anecdote, 344

Taste, standard of, 95, 205 ; sense

146 ; sexual union, a mode of

Wasp, use of antennae, 29 1

of, 25U

origin of, 149 ; in definite direc-

Waste and repair essential life-

Teeth of pike, 437
Temperature-sense, 249
Terror, 387

tions, 151 ; produced by ex-
trusion of second polar cell,
153 ; protozoan origin of, 156 ;

processes, 8
Water, changes of salinity in,
164

Thaumalia picta and amherstice,

due to the action of environ-

AV ater-ouzel, ^46

106

ment, 163; to the effects of

WATERTON, Charles, 256

Thtkla, instinct of, 430

use and disuse, 168 ; to do-

WATSON, " Reasoning Power of

" Things in themselves," or nou-

mestication, 171; in male

Animals," 369

mena, 470

stag-beetles, 180 ; in mating

WEBB, Dr., his operation on an

THOMAS, Mr. Oldfield, on rats of
Solomon Islands, 100

preferences, 205 ; co-ordinated
in Irish "elk" and giraffe,

elephant, 369
WEBER, on musical discrimina-

THOMSON, Mr. J. A., Prof. Patrick

212 ; nature of, 216 ; in amount

tion, 309 ; on muscular sensa-

GEDDES, and, on anabolism and

of developmental capital, 221 ;

tion in eye, 310

katabolism, 44 ; quoted, 50, 137,

inheritance of, 223 ; origin of,

WEIR, Mr. Jenner, on nest-

237 ; his "History and Theory
of Heredity," 35

231 ; limitations of, 232 ; for-
tuitous, in bat's wing, 235;

building in birds, 453
WEISMANN, Dr., on continuity

Thought, 482

definite direction of, 238 ; in

of germ-plasm, 138 ; on dis-

Thrush, hearing in, 264; sym-

limits of colour-vision, 281 ; in

tinctness of germ-plasm fi om

pathy in, 398

habits and instincts, 445, 456 ;

body-plasm, 140 ; on meaning

TBUNBERG on young hippopo-

in mental evolution, 496

of second polar cell, 1^3 ; on.

tamus, 423

Vertebrata, diagrammatic ac-

protozoan origin of variations.

Tissues of the body, 20

count of development of, 51

156 ; on the introduction of

TOOKE, Mr. Hammond, on egg-

VERWOKN, Dr., on protozoa, 440

senility and death, 184; on

eating snake, 88

Vesperlilio mystacinus, 70

the distinction of birds' eggs,

Tools, use of, by animals, 370

Vesperugo leisleri, 65

1»9 ; on the effects of pan-

Touch, sense of, 245

Vesperugo noctula. 67

mixia, 190; on acceleration,

Transformation and metamor-

Vesperugo piputrellus, 69

222; his views applied to

phosis, 7

Vigour and vitality, application

instinct, 438 ; the intellectual

Transparency of some marine

of, in male, 237 ; in female, 238

faculties, 497

organisms, 83

Vindictiveness, 401

WESTLAKE, Miss Mabel, on the

TREAT, Mrs., her experiments on
caterpillars, 59

Vision, 272 ; mosaic, 291
Volition, 459

parrot, 353
Whiskered bat, 70

Tricks, 355

VoluceUa bombyZans, 90

White, in arctic forms, 165 ; Mr.

Trionyx, 181

Voluntary and involuntary ac-

Poulton on production of, 202 ;

Trochui, 292

tivities, 416

in grouse, instance of rever-

Tuco-tuco, 194

Vorticella, 38

sion, 229

TURNER, Sir Wm., on New

Wildness of birds, instinctive,

Guinea natives, 169

435

Turkey, instinctive emotion in

WAELCHLT, Dr., on colour-glo-

WILL, F., on taste in bees, 253

the, 395

bules in birds, 284

WILSON, Sir Charles W., on

Twins, Mr. Gallon's investiga-

WALLACE, Mr. A. R, tabula-

wounded camels, 392

tions on. 169

tions of variations, 63; on

WILSON, Kdward, measurements

TTLOR, Alfred, on coloration in

tortoiseshell butterfly of Isle

of bats, 63

animals and plants, 201

of Man, 81 ; on protective

Wing-bones of bats, measure-

colours in fishes, 83 ; on diver-

ment of, in illustration of

gence among birds, 97 ; on

variation, 63

Udders, enlarged, of cows, 215
Ultra-violet rays, 296

recognition-marks, 1 02 ; on
papilionidas of Celebes ; 165 ;

Words, " understanding" of, by
animals, 347

Unicellular organism. See Pro-

on the dull colours of hen

Wrasse, keeness of vision of, 287

tozoa

birds, 199; on origin of

Unity of organism, 161, 234

secondary sexual characters,

Xiphocera, 179

Use and disuse, 146, 209

200 ; and A. Tylor on physio-

Utility of specific characters, 110

logical;gnidance, 201 ; on pre-

ferential mating, 203; on

YotJATT " On Sheep," 455

reversion in grouse, 229 ; on

YOUNG, Thomas, his colour-

Vanetsa urticce, 165

migration in birds, 428 ; on

vision theory, 277

Varanus benegalensis, 288

nest-building in birds, 453;

YUNG, his experiments on tad-

Variation, correlated, 59 ; and

on the song of birds, 455 ; on

poles, 59

natural selection, 61 ; tabu-

materialism, 464 ; on mathe-

lated by A. R. Wallace, 63 ; in

matical and artistic faculties,

wing- bones of bats, 63 ; advan-

484, 497

Zebra, inconspicuousness of, in

tageous, neutral, and disadvan-

WALKER, R., on reversion in

dusk, 84

tageous, 95; in climatal and

bull, 229

Zuyder Zee, new variety of

geographical conditions, 112 ;

WARD, Mr. J. Clifton, on dog,

herrings in, 99

secular, in climate and life

345

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