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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 unwelcoraed 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 Road might be photographed 
and reproduced ; and to Messrs. Longmans for the use of 
two or three illustrations from my text-book of "Animal 


University College, Bristol, 
October, 1890. 





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

The relation of animals to food-stuffs . . . . . . • • 15 

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

energy . . . . . . • • ] 6 



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

,, „ nutrition . . . . . . . . . . 25 

The utilization of the materials incorporated . . . . 27 

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



Reproduction in the protozoa . . . . . . . . 37 

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

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

Reproduction by budding . . . . . . . . . . 42 

Sexual reproduction . . . . . . . . 42 

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

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

The law of increase. . . . . . . . . . . . 58 



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

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

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

Natural selection . . . . . . .' . . . , . 77 


Elimination and selection 

Modes of natural elimination illustrated 

Protective resemblance and mimicry 

Selection proper illustrated 

The effects of natural selection 

Isolation or segregation 

Its modes, geographical, preferential and physiological 

Its effects 

Utility of specific characters 

Variations in the intensity of the struggle for existence 

Convergence of characters 

Modes of adaptation : Progress 

Evolution and Kevolution 

















Heredity in the protozoa 

Eegeneration of lost parts 

Sexual reproduction and heredity 

The problem of hen and egg 

Reproductive continuity 


Modified pangenesis . . . . .'. 

Continuity of germ-plasm 

Cellular continuity with differentiation 

The inheritance or non-inheritance of acquired characters 

Origin of variations on the latter view 

Hypothesis of organic combination 

The extrusion of the second polar cell 

The protozoan origin of variations 

How can the body influence the germ ? 

Is there sufficient evidence that it does ? 

Summary and conclusion 




The diversity of animal life 

The evolution theory 

Natural selection : not to be used as a magic formula 

Panmixia and disuse 

Sexual selection or preferential mating 

Use and disuse 

The nature of variations 

The inheritance of variations 

The origin of variations 

Summary and conclusion 

. . 177 


. . 183 






. . 231 






Tbe primary object of sensation 

. . 243 

Organic sensations and the muscular sense 



. . 245 

The temperature-sense 



. . 250 




. . 261 

Sense of rotation or acceleration 



. . 273 

Restatement of theory of colour-vision 


Variation in the limits of colour-vision 

. . 281 

The four types of " visual " organs 


Problematical senses 

. . 294 

Permanent possibilities of sensation 




The physiological aspect 

The psychological aspect 

Sensations : their localization, etc. 

Perceptual construction 

Conceptual analysis 

Inferences perceptual and conceptual 

Intelligence and reason 




The two factors in phenomena 

The basis in organic evolution 

Perceptual construction in mammalia 

Can animals analyze their constructs? 

The generic difference between the minds of man and brute 

Perceptual construction in other vertebrates 

" Understanding " of words 

Perceptual construction in the invertebrates 

" The psychic life of micro-organisms " 

The inferences of animals 

Intelligent not rational 

Use of words defined 

Language and analysis . . 

. . 331 


. . 338 


. . 350 


. . 354 


. . 360 


. . 365 


. , 374 





Pleasure and pain : their organic limits 

Their directive value 

An emotion exemplified 

Sensitiveness and sensibility 

The expression of the emotions 

The postponement of action 

The three orders of emotion 

The capacities of animals for pleasure and pain 


Some emotions of animals 

The necessity for caution in interpretation . . 

The sense of beauty 

Can animals be moral ? . . 



















The nature of animal activities 

The outer and inner aspect 

The inherited organization 

Habitual activities . . 

Instinctive activities 

Innate capacity 

Blind prevision 

Consciousness and instinct . . . . 

Mr. Romanes's treatment of instinct 

Lapsed intelligence and modern views on heredity 

Three factors in the origin of instinctive activities 

The emotional basis of instinct 

The influence of intelligence on instinct . . 

The characteristics of intelligent activities 

The place of volition 

Perceptual and conceptual volition 

Consciousness and consentience 

Classification of activities 













. . 452 








Is mind evolved from matter ? 
Kinesis and metakinesis 
Monistic assumptions 
The nature of ejects 





The universe as eject 

Metakinetic environment of mind 

Conceptual ideas not subject to natural selection 

Elimination through incongruity 

Interneural evolution 

Interpretations of nature 

Can fetishism have had a natural genesis ? 

The origin of interneural variations 

Are acquired variations inherited ? 

Summary and conclusion 


. . 478 


. . 483 









Kentish Plover with Eggs and Young Frontispiece 

1. Spiracles and Air-tubes of Cockroach 

2. Gills op Mussel 

3. A Cell greatly magnified 

4. Amceba 

5. Egg-cell and Sperm-cell . . 

6. Diagram op Circulation 

7. Protozoa 

8. Hydra Virides 

9. Aurelia : Life-cycle 

10. Liver-Fluke — Embryonic Stages 

11. Diagram of Development .. 

12. Wing of Bat (Pipistrelle) 

1 3. Variations of the Noctule 

14. „ „ Long-eared Bat 

15. „ „ Pipistrelle 

16. „ „ Whiskered Bat 

17. Variations adjusted to the Standard of the Noctule 

18. Caterpillar of a Moth on an Oak Spray 

19. Locust resembling a Leaf 

20. Mimicry of Bees by Flies 

21. Egg and Hen 

22. Stag-Beetles 

23. Tactile Corpuscules 

24. Touch-hair of Insect 

25. Taste-buds of Babbit 

26. Antennule of Crayfish 

27. Diagram of Ear . . 

28. Tail of Mysis 

29. Leg of Grasshopper 

30. Diagram of Semicircular Canals 































xvi List of Illustrations. 


31. The Human Eye . . . . ... . . . . . . 274 

32. Eetina of the Eye . . . . . . . . . . 274 

33. Variation in the Limits op Colour-vision . . . . . . 281 

34. Pineal Eye . . . . . . . . . . . . 288 

35. Skull op Melanerpeton . . . . . . . . . . 288 

36. Eyes and Eyelets op Bee . . . . . . . . 289 

37. Eye op Fly . . . . . . . . . . . . 290 

38. Diagram op Mosaic Vision . . . . . . . . 291 

39. Direction-retina . . . . . . . . . . . . 295 

40. Antennary Structures of Hymenoptera . . . . 297 




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 

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 

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 / ( 
delicate branching tubes which 
ramify throughout the body. Many 

Organisms, however, SUCh as fish Fig. 1.— Diagram of spiracles 
, , , . -, ,, i j.1 an °l air-tubes (tracheae) of 

and lobsters and molluscs, breathe an insect (cockroach). 
the air dissolved in the water in u ^e skin, etc., of the back has 

been removed, and the crop (o\) 

Which the V Hve. The Special Organs and alimentary canal (al.c.) dis- 

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

developed for this purpose are the s e»ted by dotted lines The ten 

I xl 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; 
s., shell; f„ foot; h., position of heart; e.s., exhalent siphon, whence the water passes out 
from the gill-chamber ; i.s., inhalent fiphon, where "he 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. 5 

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 

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 head 
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 

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 

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 
stables, 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 
oj r ster 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, 
\>y 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." 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. 

io 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 

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 say 
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 


spj — n.m. 

Fig. 3. — A cell, greatly magnified. 

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

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

9. Animals groiv 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 ? 


Animal Life and Intelligence. 

One of the simplest living creatures is the amceba. 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 


Fig. 4. — Amoeba. 

1. An amoeba, showing the inner and outer substance (endosarc and ectosare) ; a pseudo- 
podium, p.s. ; the nucleus, n. ; and the contractile vesicle, c.v. 2. An amceba 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. i 3 

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 


Fig. 5. — Egg-cell and sperm-cell. 
a, ovum or egg; b, spermatozoon or sperm. 

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

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 variability, 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 Nature of Animal Life. 15 

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. 


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 are 
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. Animals utilize 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 

Lastly, we have to consider the relations of animals and 
plants to energy. Energy is defined 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 has 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 limes-tone, while some has been decomposed by plants, the carbon 
being burled as coal, and the oxygen as products of oxidation ? Or, has the 
atmosphere been furnished with continuous fresh supplies of carbonic acid 

The Nature of Animal Life. 1 7 

of an old-fashioned eight-day clock. Some of the potential 
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 


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 N attire 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. 



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. 21 

gation into tissues and organs, it remains true that the body 
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 

Fig. 6, 

-Diagram of circu- 

L.A., left auricle of the heart; 
L.V., left ventricle; H., capillary 
plexus of the head ; B., capillary 
lungS. There the blood-disCS are plexus of the body ;A.C, alimentary 
7 . canal ; Lr., liver ; R.A., right auricle 

again laden with oxveen, the stream of the heart ; E - v - ri s flt ventricle ; 

. J ° ' Lu., lungs. 

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 

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 bod}^ ; 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 j^assages, 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. 

Let 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, the 
alimentary canal is a closed tube, its contents, though 
lying 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 
say, 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 lacteals. 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 lacteals 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 

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 east 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 " Horus and Antlers," in 

30 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- 

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. 3 r 

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 
ivholly 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, tbe term Ttatabolism 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 possible. 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. 


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 perforin. 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 

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. 

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 


6 Animal Life and Intelligence. 



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 

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-anirnalcule, 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 


A, vorticella extended. B, the same contracted. C, D, monads. E, amoeba. F, Para- 
mecium. G, Gregarina. c.f., contractile fibre ; c.v., contractile vesicle ; d., disc ; end., endo- 
plast ; f.v., food-vacuole ; fl„ flagellum ; gu., gubernaculum ; n., nucleus ; p.a., potential anus ; 
ps., (in A) peristome, (in E) pseudopodium ; vs., 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 m 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 amoebae ; while in other instances 

Reproduction and Development. 

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 pararncecia, 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 b, 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 Bichard 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 

40 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 (Chcetogaster 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 

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. 


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. o., bud; /., foot; h.s., hypostome; 
own.., ovum; ovy., ovary; t., tentacles; ts., 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. Rarely 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 (see note, p. 32) ; while the sperm in 
especial, and the male in general, are on their view preponderatingly katabolic. 
Regarding, as I do, the food-yolk as a katabolic product, I cannot altogether 
follow them. The d : fferentiation seems to me to have taken place along diver- 
gent lines of katabolism. In the ovum, katabolism has given rise to storage 
producis; 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 
reintroduces into the fertilized ovum the tendency w T hich, as ovum, it had 
renounced in favour of storage katabohsm. 

Reproduction and Development. 


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 daphnids, 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. Bound 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 Apus are said to coalesce 
to form the single ovum from which one embryo develops. 

Reproduction and Development. 


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- 

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

A. Ovum: em., embryo; op., operculum. B. Limnceus 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. E. Sporocyst: g., gastrula ; 
m., morula; re., redia. F. Redia: b.o., birth-opening; ce., cercaria; col., collar; di., digestive 
sac; ph., pharynx;, 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.j).). 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, Limnceus 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, 
B.). 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 redice (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 redise) embryos of yet another type are produced 
by a process of cell-division. These are known as cercarice 
(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 emhryo, in water or on damp earth, 
passes into pulmonary cavity of Limnceus truncatidus, 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. Cercarice, 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 


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 04.). 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 H. 

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 (<?.).* 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 
futHre 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 mesenteron) communicates with the exterior is called the blastopore. 
When this closes, the new opening for the mouth is called the stomodozum; 
that for the vent, the proctodeum. 

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 
chick 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 

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 yolk 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 

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 

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 48. 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 temporaiy 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 ) 



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 amoeba 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 

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. 

6 4 

Animal Life and Intelligence. 

palm of our hand. They are the metacarpals, and are 
numbered n., in., rv., 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 (PipistreUe). 

Hu., humerus, or arm-bone; Ul., conjoined radius and ulna, a bone in tbe forearm; Po., 
pollex, answering to our thumb ; n., in., rv., 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, tbe chief bone of the shank. 
The digits of the pes, or foot, are short and bear claws. Ca., 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). 

fi a 











































































Hairy-armed bat ( Vespe- 1 















rugo leisleri). S 











































Horseshoe bat (Rhinolo- 1 



































phus ferri-equinum). \ 






























Lesser horseshoe bat ( 















(Rhinolophus hippo- < 















sideros). ( 















It would be troublesome to the reader to pick out the 

A millimetre is about ^ z of an 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 5T5 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. 

6 7 

er 9 

7 2 3 4 5 


Phalanges of Digit 
44 mm 


48.5 mm 


Phalanges of Digit: 
26 mm 


Phalanges of Digift 

16.5 mm 

W mm 


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


Animal Life and Intelligence. 


37 mm 

Phalanges of Digit 
18-5 mm 

77-5 mm 

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

Variation and Natural Selection. 



Phalanges of Digit 
25 mm 

28 mm 


Phalanges of Digit 


27 mm 

Phalanges of Digit 
12-5 mm 

o » ■ 

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


Animal Life and Intelligence. 









9 1 

11 12 1 

3 1 

4 J 

5 7 

6 1 

7 J 

8 ; 

9 . 


Radius and 


32.5 mm 


J— - 


y ■ 






28 mm 


9 < 


29.5 mm 






Phalanges of Digit 

24.5 mm 


i i 










?" — 



28.5 mm 






=a *~-' 




76._5 mm 


— < 



— ^ 

>■ ■ ^ 

Metacarpal ' 







28.5 mm 




Phalanges of Digit ] 


p=— j 


14.5 mm 

- * 

*- - _^ 

- **5 



Fig. 16. — Tlie whiskered bat (Yespertilio my st acinus). 

Variation and Natural 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 ivould 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. 

"]2 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 — 8J) 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. 


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


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 sufficiently 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 sbould 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 Natural 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 ! 

J 6 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. J J 

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-nuke, 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, 

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. ii. 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 

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. f 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. 

t 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/ 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 ISfcdtiral Selection. 

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 larvae 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 being 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 doion on the dark back 
of a fish," says Mr. A. K. 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 (Chcetodon, 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 zebra 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 Spirorhis 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, 1S89. 

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. 

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 






• L"' ~ 


Fig. 18. — Caterpillar of a moth (Ennomos tiliaria) on an oak-spray. (From 
an exhibit in 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 


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 maybe seen in the insect; 
exhibits on the basement at South Kensington, having 
been figured from them by the kind permission of Professor 

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 the 
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 Doliops, a longicorn, resembles the 
strongly encased Pachyrhyncus orbifex, 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. 

t 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 Sir. E. B. Poulton, in his " Colours of 
Animals " (p. 252), where a (probably) homopterous insect mimics a leaf-cutting 
ant, together icitli its leafy burden — a membranous expansion in the mimic 
closely resembling the piece of leaf carried by the particular kind of ant he 

* 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. 

t Nature, vol. xlii. p. 115. 

Variation and Natural Selection. 89 

siclered 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 colouring 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 (Volucetta 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 larvse 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 
Bombas 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 (Nomacla 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 (Plwynocephalus 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. 


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, ~b, Bombus muscorum ; c, d, Volucella bombylans ; e, Eristalis tenax ; f, Apis mellifica. 
The underwings of the hive bee (/) 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 aUowing 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 Natural 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 ? " t 

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. svi. pt. ii. f Ibid. chap. siv. 

g6 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 

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 inOre 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- 
f ulness 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 

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 facit 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 both 
parents, would be absolutely fatal to, divergence of character 
within the interbreeding members of a species. And yet 
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 kill 


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 

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- 

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, 
f Ibid. pp. 217, et 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 

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 

104 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, t 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 Linnxan Society, vol. xix. No. 115 : " Zoology." 
t " Animals and Plants under Domestication," p. 145. 
% 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 

It is interesting to note that almost the only particular 
example given by Mr. Piomanes 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 

106 Animal Life and Intelligence. 

goat seem to be well authenticated. Of rats Darwin 
says that " in some parts of London, especially near 
the docks, where 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 
amherstice), 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, and 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 
hj 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 

108 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 ease 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 

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. 1 1 3 

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 

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 Kainozoie 
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 in 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). 


ii4 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 Bhastic 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 Natural Selection. 1 1 5 

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, aud 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 in 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. 1 1 7 

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 technical examples may be noticed in a note. (1) Professor 
Haeckel has recently {Challenger Reports, vol. xsviii.) shown that the 

1 1 8 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 Heliconidse and the Danaidee), 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 DisconanthsB, traceable to trachomedusoid 
ancestors ; (fc) the Siphonauthae, traceable to anthomedusoid ancestors like 
Sarsia. (2) M. Paul Pelseneer has been 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; 
(6) the Gymnosomes, traceable to apbysiid ancestors. In each case, the 
ancestral sea-slug has been modified for a free-swimming life. 

Variation and Natural Selection. 119 

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, 

120 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. 

Eevolution 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. 
Eevolution 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. : " Yertebrata," by E. Lydekker. 

Variation and Natural Selection. 1 2 1 

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. 



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 

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 & oes no ^ 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. 123 

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 cells. These 
cells are, moreover, not all alike, but have undergone 
differentiation with physiological division of labour. There 
is an inner layer of large nutritive eells, 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 ciystals. 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 xDower 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 

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 

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 appearance, 
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 

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 nest 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 O right 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 

t> j i- 11 rs<^-— Nerve and muscle cells e , , . , . 

Reproductive cell 0^ Glan( , ular and mltrUive cella ^ Skeletal, etc. 

Reproductive cells— - 0^ G , ^ \*^ 

^^Reproductive O. 

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 cell O^H2 ody , ,■ „ ,-.— — - "Body . 
Reproductrve cells O* Reproductive 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 gemmules, 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 ^^ ^^ sk. and pr. ^ s. 

Reproductive cell O Nerve and muscle cells ~~^0^~ n - and m - ~550 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 mid 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 
(pangeneticalry) 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 Eichard) 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 aud Theory 
of Heredity : " Proceedings of the Royal Society of Edinburgh, 1S89. 


6 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. 1 3 7 

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-hypotheticai. 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 gerrn-ce^s," 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 geim-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 

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

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

Heredity and the Origin of Variations. 139 

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, " Eapid 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,| "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-plasm 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 tbe 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 " amcebre." 
But this is no doubt because the amcebse (germ-plasms) are contained in the 
mammals (body-cells). (See the quotations that follow in the text.) 

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

I40 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 

Now, although I value highly Professor "Weismann's 


Fig. 21.— Egg and hen. 

I. "The egg produces the hen." II. "The hen produces the egg." In I. the dints pro- 
duced by the environment are not inherited ; in IX. 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. 

j 42 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. 

The hypothesis of cellular continuity is one 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 

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 07'igin 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 ivork of reproduction, as others 
have been differentiated and set apart for other protoplasmic 

Cell-reproduction is, however, in the metazoa of two 
kinds. There is the direct reproduction of differentiated 
cells, by which muscle-cells, nerve-cells, or others reproduce 
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 amoeba. 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- 

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. 131. 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 


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 then transmission to be accounted for ? 

Every individual organism reacts more or less markedly 
under 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- 

He7'edity 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 

"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 

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.* 




10 ... 

... 10 

8 ... 

... 10 

9 ... 

... 5 

7 ... 

... 9 

6 ... 

,.. 6 

40 40 40 

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

Heredity and the 0?'igin 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 distinc't 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 

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 iu 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 Weismann 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, '67S. 

'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 — 

Parents. Offspring. 

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 balancement was suggested at 
nearly the same time by Goethe and Geoffroy Saint-Hilaire. The application 
in the test has 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 redaction 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 bocly-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 

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. 

(b) 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 Eay 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, 1S76. Since reprinted in " 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 Irypothesis 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 Spev.cer, " Principles of Biology," vol. i. p. 256. 

Heredity and the Origin of Variations. 161 

tory 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 definite answer can be given. 

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


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 
modinability 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 Royal 
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. 16 


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 
pupae 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 says % 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 
urticce) and the surrounding objects, the pupas 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 how 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. 8S. 

% " 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" (q-v.). 

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 larvas 
of a Texan Saturnia fed on a new food-plant develop into 
imagos 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, f 

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 Herdman's Inaugural Address, Liverpool Biological 
Society, 1888. 

i 7° 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. 

t 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, i 7 1 

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 : — 


2 — Survival-mean. 

4 \ 
Birth-mean — 5 \ 

rj > Eliminated individuals. 

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. 175 

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. 

Variacion 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 

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. 

( 177 ) 



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. 


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- 

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 Batistes, 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- 


Animal Life and Intelligence. 


































; — 






■ X 



T3 OS 

§ a 

_ o 

c * 

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 

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- 

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 in 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 Palseontology," 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 ? Eeduced 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 ? 

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 winning 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 

(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.! 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. f 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 certaiij 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 

T?anmixia 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. Ptomanes 
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. Eomanes 
and Professor Eay 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- 

192 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. Eeversion 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. Eomanes 
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. Bomanes 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. 
Bomanes, 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 Evolution. 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. 


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. 

t With regard to blind cave-fish, Professor Eay Lankester has suggested 
that some selection has been effected. Those animals whose sight-sensitive- 
ness 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 antennge are concerned. First, those which preserve 
eyes and antennae 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 antennae 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 Weismann 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 use 
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 

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 antennse 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. vih. 

Organic Evolution. 199 

probably in the large, branching antennse. 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 

200 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." f 
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, " The Evolution 
of Sex," p. 28, also contend that " combative energy and sexual beauty rise 
pari passu with male katabolism." 

Organic Evolution. 201 

mating are, supposing them to be terce causes, 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. 

202 Animal Life and Intelligence. 

adequate explanation of the specific colour-tints of the 
humming-birds, or the pheasants, or the Papilionidse 
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 gaucliness (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. 20; 

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 Eev. 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-niarks, has had 

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

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 sesthetic 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 A ttida," * by George W. 
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 is 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 

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 some 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. 


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 Cope 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. R. 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. 2 1 3 

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 

Still, we should remember that among neuter ants — 
for example, in the Sauba ant of South America (Oecodoma 
cephcdotes) — 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 Roux 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. f See ante, p. 52. 

Organic Evolution. 2 1 5 

all the anterior part of the body should be appropriately 

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," 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 clogs 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. 

t " 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 necessarily in any way 
correlated with any deeper organic variations. They are, 
however, in many cases so correlated. For example, the 
form of the pouter pigeon is correlated 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. 2 1 7 

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 Eoyal 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 

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. 

o. Variations in the time occupied in development. 

6. Variations in the time at which reproduction com- 

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 

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. Eew 
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 

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 

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, f 
" 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. 

t ''Animals and Plants under Domestication," vol. ii. p. 313. 

J Ibid. p. 56. 

Organic Evolution. 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.! 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. 

f Quoted from " Medical Notes and Reflections," 1855, p. 267, by Darwin, 
"Animals and Plants under Domestication," vol. i. p. 446. 

224 Animal Life and Intelligence. 

with Professor Weisinann, 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 to 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 sperrn 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 

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 

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 

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 E. 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 

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. 

% 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.^ 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 

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 

3. 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. Bland Sutton* 
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 vertebras 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 f 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 

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,f 
" 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. 

t Ibid. p. 282. The phenomena of the seasonal dimorphism of butterflies 
and moths show that changes of temperature (and perhaps moisture, etc.) 
determine very striking 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 

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 tinder Domestication," vol. ii. p. 244. 

t " Darwinism," p. 293. % " 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 

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 seq. 

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 
Eimer'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 chemieo- 
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 to 
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 the 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 vifcal 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 

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. 

( 2 43 ) 



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 

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 

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 2| 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 y^ 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. 


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, 

Pig. 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 eat 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 
-Touch-haix of they are sensitive to touch: but in 


t.n., touch-hair ■ cu., cuticle; a g rea t number of cases, although 

cenco h nn P e'cte e rtwkh nerve^S observation shows that they are thus 

gf^M^xh^Snt sensitive, we know nothing definite 

eight of r< ies n s-accesso?y Te ceii^ as to how the surface is specially 

which are not figured here. 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, then, what we may term a telcesthetic 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 


Animal Life and Intelligence. 

continued and healthful fulfilment of the process of 

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-rwre. 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 cir cum vallate papillae ; 
but in the rabbit and some other 
animals they are collected in the 
folds of a little ridged or pleated patch 
— the papilla foliata — on each side 
of the tongue near the cheek-teeth. 
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 Eoyal Society of Edinburgh,* suggests that "a 
group of salts of similar chemical properties have their 

* See abstract in Nature, vol. xxsiv. p. 515. 

Fig. 25.— Taste-buds of 

i., section across part of the 
pleated patch (enlarged) ; ii., 
taste-buds further enlarged. 

The Senses of Animals. 

25 1 

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 : — 


Quinine — 

Male observers 

detected 1 

part in 390,000 parts of water 

Female „ 

» 1 

„ 456,000 

„ „ 


Cane-sugar — 
Male observers 


Female „ 

»5 *• 


9> SJ 


Sulphuric acid — 

Male observers 

„ 1 


» )' 

Female „ 

>5 *■ 


„ ,, 


Bicarbonate of sodium — 

Male observers 

;? A 


„ „ 

Female „ 

5J ■*■ 


,, „ 


Common salt — ■ 

Male observers 



„ ,, 

Female „ 


„ 1,980 

» » 

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. xsxvii. 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 skin 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 f (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 maxillaa 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 
^6o"o"ooo P ar * °f a milligramme of chlorophenol, and the 
46"o"oWoo P ar ^ °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 

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 Eamsay 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 their 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 " telsesthetic 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 telsesthetic sense, informing the 
organism of the presence of more or less distant food. 
Thus, if you stir with your ringer 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 (telsesthetic 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. Xo. 3, p. 235. 

The Senses of Animals. 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 
telaesthetic 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 iu con- 

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 Beaumur, in the feelers or 
antennas, and in some cases also in the palps. If the 
antennas 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 
antennas that the male emperor moth (Satiuiiia carpini) is 
able to find its mate.* If a collector take a virgin female 

* IMr. S. Klein mentions a similar fact in connection with Bombyx quercus 
(Xature, vol. xssv. p. 2S2). 

The Senses of Animals. 


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 antennae 
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 

In the aquatic crayfish there 
are, besides the long antennae, 
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- 

„„„„ „,!,• -U „, ill Fig. 26. — Antennule of crayfish. 

gans, which were regarded by . . . J 

Z. . . ° J 1-3-, mner joint; o.j., outer joint; ol., 

Ley dig, their disCOVerer, aS olfaotor y setEe ; ol'., the same, enlarged; 

' au.op., auditory opening in the basal di- 

olfactory. Observation, too vision > wbich has been cut °pen to show 

' ' au.s., the auditory sac; au.n., auditory 

seems to confirm the view that nervebranohinstothetworidsesbesetwith 

auditory hairs ; au.h., auditory hair, en- 

the sense of smell (or telaes- larged - (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 antennae and antennules. The antennas 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. 

The Senses of Animals. 261 

Hearing is a telgesthetic 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 

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 *j 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. 


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 

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 tile 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, necessarily indicates 
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-danee 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. 


Animal Life and Intelligence. 


Fig. 28.— Tail of Mysis. 

au., auditory organ. 

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 
watched these under the micro- 
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 
mouth-cavity (see Fig. 27). In the organ within 
the leg there is a group of cells, followed by a 
row of similar cells 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 

Fig. 29.— Leg 
of grasshopper. 

ty., tympanic mem- 

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 
antennse 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 smell. 

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 

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. 


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 


Fig. 30. — Diagram of semicircular canals. 

A. bony labyrinth of human ear (after Summering), c, c, the cochlea; s.c, superior 
semicircular canal ; p.c, posterior semicircular canal ; h.c, horizontal semicircular canal ; 
a, a, a, their swellings, or ampullse; f.o., f.r., fenestra ovalis and rotuuda (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. xl. 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 memhranous 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 
Ma eh 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- 

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 spelietts) the 
semicircular canals are, according to Wyman, unusually large. 

272 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 

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 cmd 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 _ , , A . _ _ _ . , 

the eye. Enlarged and that these rods and cones do not face 
section of minute j ^ direction from which the light comes, 

fragment. ° ' 

b., back of retina next but face towards the back of the eyeball, 

the outer coat; l.r.c, , . , n ■, . -, -, , 

layer of rods and cones; where a pigmented substance is developed. 

i.l., intermediate layers; „.. . ,. , , .. „ , .. . 

i.g.c, layer of ganglion- The rays of light are thus locussed through 
nerve-fibres;"/., 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 -^ 
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 25- of an inch (1*1 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 eoW °f an i ncn ('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 eoVo °^ an i nc ^ ('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. Eed 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 E. is unstable to the impact of a con- 
iderable range of liErht-vibrations. 

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 K., 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 E. 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 

" 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 readings, 
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. 





: ==- 










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 of Maxima and Minima in Wave-lengths, expeessed 
Millionths of a Millimetre. 




No. of 








Women under 30 . . 
Men „ „ .. 
Women over 30 . . 
Men „ „ .. 











x \ right eye 
a I left eye 



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 (^g 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 B„, 0., and Gr. 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. slii. 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 chameleon. 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 

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. Nos. 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 

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 (Labridce), 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 chelss, finally raking the sand over its back, and 
gently levelling it with its antennee ; but if the least bit 
be exposed, the wrasses will find it in spite of its protective 

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. 


Animal Life and Intelligence. 

Modified eye-scale of a small lizard, fliat, 111 ancieilt Hfe-formS, 

Yaranus benekalensis. (After Baldwin ' ' 

s P encer the Ichthyosaurus, and Plesio 

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. 
Fig. 34.— Pineal eye. There is some reason to suppose 


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 

A Lab^mthodont amphibian from the Per- oce Jli # These OCelK, Or eye- 
mian of Bohemia (after Fritsch). X 4. Pa., ' J 

the parietal foramen. i e ^ S} differ, in different in- 

sects, as to the details of their structure ; but in general 

Fig. 35.— Skull of Melanerpeton. 

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 
cells, and then follows 

-Eyes and eyelets of bee. the retina, in which 

A. Drone. B. Worker. there are & numDer f 

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 

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 (JEschna) 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, 



Animal Life and Intelligence. 

be made to give a separate image of such an object as a 
candle reflected in the 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 focus sed at the 
point of the cone (where 
Fig. 37,— Eye of fly. the nerve-rod comes), a 

Transverse section through head. (After Hickson.) gpot Q f jjg]^ an d not an 

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 ^ 
a screen placed behind 

,1 -r, e , . ■, . , . Fig. 38. — Diagram of mosaic vision. 

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 
antennas seem almost to take the place of eyes at close quarters. 

t " Senses of Animals," p. 194. 

292 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 

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 
part 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 medusae (jelly-fish) they are sometimes found on the 
margin of the umbrella. Eyen 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 t® 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 

setherial 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, 8 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 

„ ,, ., , Fig. 39. — Direction-retina. 

cases, from the convexity and c . . ° , .. 4 . . . . t . .. t . 

" Simple retina for distinguishing the direction 

position Of the lenS, the for- of the source of light or of shadow. 

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- 

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 claphnias 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. Ked. 

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, 
fo 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. 


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., hypodprmis; c, ordinary hair; d., tactile hair; e., cone; /., depressed 
hair lying over g. cup with rudimentary hair at the .base; h., simple cup; i., champagne- 
cork-like organ of Forel; k., flask-like organ ; I., 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 telsesthetic 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 
Piayleigh 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 sether-vibrations. The figures are those given by 
Professor Langley : — 

Wave-lengths in Number of 
Quality of radiations. thousandths of vibrations per Effects on man. 
a millimetre, second in billions. 
Limit of photography, arti- 
ficial source 0-185 .. 160 .. none known 

Limit of photography, solar 
source .. .. .. .. 0295 .. ;> >> 

Limit of violet to normal 

eyes 0-36 .. 833 > ^ vigion _ 

Limit of red to normal eyes . . 0'81 . . 370 ) 
Probable inferior limit of 

temperature-sensations.. .. 9"25* .. 30 .. temperature- 
Longest waves hitherto re- sense 
cognized with bolometer .. 30-0 1 •• 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 

I I thousandths of a millimetre. I have taken about 925 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 

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 w r orld. 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. 



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 the 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 

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 

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 


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 

308 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 -^^ 
of an inch ("0044 millimetre), which nearly corresponds 
with the space between two cone's 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, as 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 

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 e\es 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 -g-oW 
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. 

f 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 hoy 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. Anew 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, 
3 7 ellow, 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 use this 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 
shall 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, r 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 aud 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 bas the power of supplying its 
own — x, and so we get (througb the imagination of tbe mind and the object) 
x+y — x, or y'pure and simple" (Mivart, " On Truth," p. 135). Mr. Mivart 
devotes a wbole section of this work to the defence of ordinary common-sense 
realism. Tbe 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. Bising 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 clog ? 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 

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 under 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 sich. Its essential character is its inde- 
pendence of man ; and hence its uhknowahility. 

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 of 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 


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 

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 sourfds, 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 and 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 classification 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 

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 

Hon. 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 Muller,! 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. t Ibid. p. 339. 

X " 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. Eomanes (" 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, iu 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 Mi-. Romanes's and Mr. 
Mivart's tabular statements. 

Mr. Eomanes. 

I General, abstract, or notional = Concepts. 
Complex, compound, or mixed = Recepts, or 
generic ideas. 
Simple, particular, or concrete = Memories of per- 


Mr. Mivart. 

-j- ( General or true universals = Concepts. 
\ Particular or individual = Percepts. 

! Groups of actual experiences! 

combined with sensuous = Sensuous umver- 
reminiscences [ sals > or rece P ts - 

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 

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 such 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 : (X) 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. 


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 

* " Outlines of Psychology," p, 414. 

t Mr. Bonmnes adopts a different use of the terms "reason" and " rational," 
to which allusion will be made in the next chapter. 



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- 

332 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 ; the 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. 

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. GL 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 not find 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 clog — 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 by 
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. 3 37 

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 th-e 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 
observtd 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 


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. Eemembering 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 psychoplasrn 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 psychoplasrn sets in by which, in process of 
differentiation, the tissues and organs 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-Q Animal Life and Intelligence. 

to sleep again, and no amount of blowing disturbed her 
further. Similarly, Mr. Bomanes'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 denning 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 Eomanes'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 

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 

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 

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 

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 

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. Bobert 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 

"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. „ „ 


,. 5. 
„ 6. 


91 ' • 11 11 






















' Nought ' once. 





















' Door ' once. 











80 31 

"Thus, out of 113 times, lie brought 'Food' 80 times, 
' 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 
languages ! 

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. Eomanes,* "All the higher animals have general 
ideas of ' good-for-eating ' and ' not-good-for-eating,' quite 
apart from any particular objects of tvhich 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. | 

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 clog, 
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 this 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. Romanes. 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 to 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 

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. 35 

o JO 

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. Komanes 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. 

2 A 

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 

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 lie 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 rhynie-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 

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 ? Bemember 
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. Remember 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. 
Eemember 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 eommon basis of more 
simple sensation, the process of outward projection has its 
rudimentary inception. The earthworm, which finds its way 

* Professor Max Miiller suggests to me that perhaps the ants were 

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 f 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. 4S. 

360 Animal Life and Intelligence. 

merely organic, and how far there enters a psychological 

I ought not, perhaps, to pass over in perfect silence the 
subject of protozoan psychology. M. Binet has published 
a little hook 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. Komanes 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 anirnalculse 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 

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 

2,62 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. Eomanes 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 " consentieuce." I agree to so large an 
extent with ]\Ir. 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 hind 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 5 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 

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. Bae and Mr. Fothergill communicated to Mr. 
Romanes 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 
clone. 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 nest Dr. Rae'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 up 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. Bae as a wonderful instance of " abstract 

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 Get 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. Eae, 
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 
kneio the eggs ivould 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 A nimal L ife 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. Eomanes 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 

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 "Keasoning 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 outmasterecl 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 

The other instance I will quote was communicated by 
Mr. George Bidie to Nature.^ He there gives an account 
* Page 54. t Vol. sx. p. 96. 

2 B 

3JO 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- 

Some stress has 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. 3-1. 

t Romanes, " 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. 
Komanes 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. 

2,7 2 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. Bomanes 
uses them in a different sense. "Beason," 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 heing 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 

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 Muller 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 froni 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 Muller 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 dog-mind 1 ^ p erc epts to be interpreted in terms of (4), being 

(2) x X cat-mind > - j analogous thereto but not identical therewith. 

(3) x X infant-mind > 

(4) x x adult human mind = the percepts of psychologists, named or 


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 have 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. 

,78 Animal Life and Intelligence. 



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 ma}^ call indifferent or neutral, I am inclined to answer 

Appetence and Emotion. 379 

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 

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, with 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, 

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. Eesponsiveness 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 


86 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 ) ^ . , C Stimulus of 

> — > nervous processes m bram— > { 
sense-organ J r 1. motor-organs. 

Consciousness of ■) , .. .. ( Consciousness of 

. ><— perception, emotion —> < ,. .. 
sense-stimulus j I. 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 

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 Richardson, 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 

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 

390 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 with 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 Emotion. 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 most 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 

39 2 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 Jhat 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. Lamont 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. 

;94 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, | " 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. 

* Mature, vol. xxxvii. p. 619. f 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 contraiw, 
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- 

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 Macmillari '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. 
Eomanes'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. 
f " Descent of Man," pt. i. chap. iii. 

Appetence and Emotion. 397 

of my own (the Eev. George H. R. 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 sjmrpathy. 
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 (Mature, vol. sxviii. p. 150). Mr. Duncan 
Stewart gives {Nature, vol. xsviii. 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 1S78 some tame partridges in Aberdeenshire 
brought two wild coveys to be fed near the doorstep of the house. And a 
case has heen communicated to me by Miss Agnes Tanner, of Clifton, of a 
thrush that pulled up worms on the lawn for a lame companion. 

f " 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 

4-CO Animal Life mid 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 -f- 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. Eomanes, 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. t Ibid. p. 444. % 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 seeing 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 

402 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 Cebus 
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 see 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, f " 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 J 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. 

t " Descent of Man," pt. i. chap, iii., quoted from Brehm's " Thierleben." 

% 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 

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 he 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 Man," quoted by Komanes, 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.Eomanes'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 aesthetic 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. si. 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 

41 o 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 VI., 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, and, 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 
selected 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 

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 " aesthetic " 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 
develoiDinent ; 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 

* I have said nothing about the emotions of invertebrates, because I have 
nothing special to say. They have, no doubt, emotions analogous to fear, 
answer, 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 iustinct of play. But this admirable observer has rendered it 
probable that sympathy and affection in ants and bees have been somewhat 

( 415 ) 



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- 
bining of old activities in new modes, and by special applica- 

41 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— > in terneural processes — ^ activities. 

Inner aspect: Accompanying consciousness ^^ mental states — ^ accompany- 
ing consciousness. 

The physical stimulus and the resulting activities are 

2 E 

4i 8 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, u the 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 

420 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 rivetted 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. Bomanes 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. Bomanes 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 bis 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 hank. 

Birds, especially those which are called prcecoces, 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 
twelveUnches distant ; at ten minutes it made a peck at 
its own toes, and the nest 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."! 

Mr. Spalding's experiments also proved that, even 

* Macmillan's Magazine, February, 1873. Professor Eimer, in his " Organic 
Evolution " (English translation, p. 215), 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 thern 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 eeitons 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). J 

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,f " 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 pupae ; 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. Eomanes, 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. 

f "Animal 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 proecoces, 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 

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. Romanes 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. Romanes's view, to be regarded as instincts. 

Having made this initial criticism, I may now state 
that I regard Mr. Romanes'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. Romanes has 
proved himself, I am according it the highest praise in my 
power. I have ventured in this volume to criticize some 
of Mr. Romanes'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- 


434 Animal Life and Intelligence. 

ful inferences, and his lucid and often luminous expo- 

I do not propose to go over the ground so exhaustively- 
covered by Mr. Eomanes in his discussion of instinct. I 
shall first endeavour shortly to set forth his conclusions, 
and then review the subject in the light of modern views of 

Admitting that some instincts may have arisen from 
the growth, extension, and co-ordination of reflex actions, 
Mr. Eomanes 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. Eomanes 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. 
Eeferring the reader to Mr. Eomanes' 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. xxviii. p. 271, quoted in " Mental Evolution in Animals," 
footnote, p. 196. 

436 Animal Life and Intelligence. 

Romanes's secondary instincts depend upon the inheritance 
of habits intelligently acquired. By the school of Professor 
Weisniann, 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 t. 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." Piegarding the 
mason-wasps and their allies, which sting larvae 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, H " Selec- 
tion cannot here have had much influence, since the 

* " Organic Evolution," pp. 223, 224. f Ibid. p. 263. 

% Ibid. p. 303. § Ibid. p. 258. || Ibid. p. 279. \ 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,| 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. 29S. 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. 

438 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- 
mann 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 Eirner. 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 larvae are 
hatched as active little insects, with six legs, two long 
antennae, and four eyes, very different from the larvae 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 
then 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- 

* "Weisruanu, " 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 f can have resulted 

* M. Fabre, as interpreted by Sir John Lubbock, "Scientific Lectures," 
2nd edit., p. 45. 

f 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 bieuspidata, 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. 127, 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 the 
organism they were in their lifetime anxious to protect from harm, for they 

44° 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 closed, 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 conimunrty, mutually dependent on each 
other, and subject to natural selection, that community 
would best escape elimination in which the queen produced 

44 2 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? Any 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 

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." f 

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 he 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 

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 

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 Semnojjithecus 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 shoivn 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- 

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 tbougb tbe great majority of individually acquired 
modifications of babits bave owed tbeir origin to intelligent 
direction, still it is conceivable tbat some of tbem bave 
not. An animal may bave been forced by circumstances to 
modify its babits, witbout any exercise of intelligence ; and 
tbis modification, forced, tbrougb changed conditions, upon 
all tbe members of a species, may, tbrougb inheritance, 
bave passed into tbe stereotyped condition of an instinct. 
Under eacb factor, tben, we bave two several categories. 

1. Elimination . 

2. Selection 

3. Inheritance 

{ a. of unintelligent activities. 
" \ b. of intelligent activities 

(a. of unintelligent activities. 
' \ b. of intelligent activities. 
a. of unintelligent activities. 


of intelligent activities. 

In all cases, however, where intelligence has been a co- 
operating factor, tbis 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 tbe 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. 
a. Drumming of snipe. 

Procedure of Queensland bower-bird. 
f a. 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 bave 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 tbe tail-feathers was not, in its inception, 
intelligently performed with the object of exciting sexual 

Habit and Instinct. 449 

appetence in the hen. The ease 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. 


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 (spicules amoris), practical tangible darts of glistening 
carbonate of lime. Mr. George W. Peckham has recently 
described f the extraordinary "love-dance" of a spider 
(Saitis jyulex). " 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 1 

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 
he 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. 

452 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 

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." Dureau de la Malle, as quoted by Mr. Eomanes,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,| 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. 
f "Mental Evolution in Animals," p. 222. J " 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 larvas. 

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 

4sS 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, 
Avithout 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 — 

„,. , ,. ,. * fulfilment in action, 

fetimulus : perception: emotions . , ., ... „ ,. 

r r > inhibition ot 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 Intelligejice. 

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 pass 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 

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. 


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 : — 




A. Involuntary (auto- 


Unconscious re- 

Automatic or 

matic and reflex) 

action of nerve- 

reflex act 

B. Involuntary (habi- 

Percept (per- 

Impulse (per- 

Involuntary ac- 

tual and instinctive) 

haps lapsed) 

haps lapsed) 


C. Voluntary (percep- 



Voluntary ac- 



1). Voluntary (con- 





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 

* " Moral Order and Progress." 

464 Animal Life and Intelligence. 



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. E. 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 say " 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 Miiller,f 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," and " predominant." I 
can only say that in each case I 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 fuhy 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 " substa