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MEIN'TAL EYOLUTIO^ 



IK 
AI^IMALS. 



MENTAL EVOLUTION 

IN ANIMALS. 



BY 



^ 



GEOEGE JOHN EOMANES, M.A., LL.D., F.E.S., 

ATJTHOE OF " ANIMAL INTELLIGENCE." 



POSTHUMOUS ESSAY ON mSTINCT. 

BY 

OHAELES DARWm, M.A., LL.D., F.E.S. 



NEW YORK: 

D. APPLETON AND COMPANY, 

1, 3, AND 5 BOND STEEET. 

1884. 




/^^^r^ 




PEE FACE. 



It will be observed that the title of this volume is " Mental 
Evolution in Animals." The reasons which have led me to 
depart from my intention (as expressed in the Preface of 
" Animal Intelligence") to devote the present essay to mental 
evolution in man as well as in animals, are given in the 
introductory chapter. 

It may appear that in the following pages a somewhat 
disproportionate amount of space has been allotted to the 
treatment of Instinct; but, looking to the confusion which 
prevails with reference to this important branch of psychology 
in the writings of our leading authorities, I have deemed it 
desirable to consider the subject exhaustively. 

It is, I think, desirable briefly to explain the circum- 
stances under which I have been enabled to produce so much 
hitherto unpublished material from the MSS of the late 
Mr. Darwin, and also to state the extent to which I have 
availed myself of such of this unpublished material as came 
into my hands. As I have already explained, in the Preface 
of " Animal Intelligence," Mr. Darwin himself gave me all his 
MSS relating to psychological subjects, with the request that 
I should publish any parts of them that I chose in my works 
on Mental Evolution. But after his death I felt that the cir- 
cumstances with reference to this kind offer were changed, 
and that I should scarcely be justified in appropriating so 
much material, the value of which had become enhanced. I 
therefore pubUshed at the Linnean Society, and with the 
consent of Mr. Darwin's family, as much of this material as 



2 PREFACE. 

could be piiblislied in a consecutive form ; this is the chapter 
which was intended for the " Origin of Species," and which, 
for the sake of reference, I have added as an Appendix to my 
present work. For the rest, the numerous disjointed para- 
graphs and notes which I found among the MSS I have 
woven into the text of this book, feeling on the one hand 
that they were not so well suited to appear as a string of 
disconnected passages, and on the other hand that it was 
desirable to publish them somewhere. I have gone through 
all the MSS carefully, and have arranged so as to introduce 
every passage in them of any importance which I find to 
have been hitherto unpublished. In no case have I found 
any reason to suppress a passage, so that the quotations which 
I have given may be collectively regarded as a full supple- 
mentary publication of all that Mr. Darwin has written in the 
domain of psychology. In order to facilitate reference, I have 
given in the Index, under Mr. Darwin's name, the numbers of 
all the pages in this work where the quotations in question 
occur. 

18, CoHNWAii Teebace, 

Eegent's Park, London, N.W., 
November, 1883. 



CONTENTS. 



Peefacb 
Inteoductiok 
Chaptee I. 
IL 

» in. 

„ IV. 

„ VI. 
„ VII. 
., VIII. 

„ IX. 
X. 

„ XI. 
„ XII. 

„ XIII. 

„ XIV. 

„ XV. 
„ XVI. 
„ XVII. 



The Ckiterion of Mind 

The Stkuctube and Functions of Neete-Tissue 

The Physical Basis of Mind 

The Root-peinciples of Mind 

Explanation op the Diageam 

Consciousness . . 

Sensation 

Pleasuees and Pains, Memoey, aed Association 
OP Ideas 



PAGE 

1 
5 
15 

24 
31 
47 
63 
70 
78 

105 
125 
142 



Peeception 

Imagination . . . . .... 

Instinct .. .. .. .. .. .. •• 159 

.. 177 



Instinct (continued). 

Origin and Development of Instincts 

Instinct (continued). 

Blended Origin, or Plasticity of Instinct. . . . 200 

Instinct (continued) . 

Modes in which Intelligence determines the Varia- 
tion of Instinct in Definite Lines . . • . 19 

Instinct (continued) . 

Domestication - .. .. .. «. •• 230 

Instinct (continued). 

Local and Specific Varieties of Instinct . . . . 243 

Instinct (continued). 

Examination of the Theories of other Writers on 
the Evolution of Instinct, with a General Sum- 
mary of the Theory here Set Forth . . . . 256 



CONTENTS. 



Chapter XVIII. Instinct (continued). 

Cases of Special Difficulty with Eegard to the 
Foregoing Theory of the Origin and Develop- 
ment of Instincts . . . . . . . . 273 

„ XIX. Keason 318 

„ XX. Animal Emotions, and Summaky of Intel- 
lectual Facplties . . 341 

Appendix •• •• 353 





P.O.„CT..,E-0T,0..LO...L0.-.„. 




Emotion, Will, Intellect. 




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Emuhlioi., Pndc, R«m,n,c,.i, ^Eahi.ic lov= of o.n,.m™i, 1 error. 


25 


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Recognition of P.cturra. Undctanding of »ord.. Dreanung. 


Birds. 


8 monlh- 


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Communication of ideas. 


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Jealousy. Anger. Play. 


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Fish and Balnichu. 


.-week. 


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Parental alTection. Social fecliogs, Se;(ual soleciion. Pugnacity. Indtiittry. Curiosity. 


20 


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Recognition of offspring. Secondary mstinrts. 


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Proioplasui.c movements. 


Protoplasmtc organ.sms. 


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3 



INTEODUCTION. 



In tlie family of tlie sciences Comparative Psychology may 
claim nearest kinship with Comparative Anatomy ; for just 
as the latter aims at a scientific comparison of the bodily 
structures of organisms, so the former aims at a similar com- 
parison of their mental structures.* Moreover, in the one 
science as in the other, the first object is to analyze all the 
complex structures with which each has respectively to deal. 
"When this analysis, or dissection, has been completed for as 
great a number of cases as circumstances permit, the next 
object is to compare with one another all the structures which 
have been thus analyzed ; and, lastly, the results of such 
comparison supply, in each case alike, the basis for the final 
object of these sciences, which is that of classifying, with 
reference to these results, all the structures which have been 
thus examined. 

In actual research these three objects are prosecuted, not 
successively, but simultaneously. Thus it is not necessary 
in either case that the final object — that of classification — 
should wait for its commencement upon the completion of 
the dissection or analysis of every organism or every mental 
structure that is to be found upon the earth. On the con- 
trary, the comparison in each case begins with the facts that 
are first found to be comparable, and is afterwards pro- 
gressively extended as knowledge of additional facts becomes 
more extensive. 

Now each of the three objects which I have named affords 

* The word " structure " is used in a metaphorical sense when applied to 
mind, but the usage is convenient. 



6 INTRODUCTION. 

in its pursuit many and varied points of interest, whicli are 
quite distinct from any interest tliat may be felt in the attain- 
ment of the ultimate end — Classification. Thus, for example, 
the study of the human hand as a mechanism has an interest 
apart from all considerations touching the comparison of its 
structure with that of the corresponding member in other 
animals ; and, similarly, the study of the psychological facul- 
ties in any given animal has an interest apart from all con- 
siderations touching their comparison with the corresponding 
faculties in other animals. Again, just as the comparison of 
separate bodily members throughout the animal series has an 
interest apart from any question concerning the classification 
of animal bodies to which such comparison may ultimately 
lead, so the study of separate psychical faculties throughout 
the animal series (including, of course, mankind) has an 
interest quite distinct from any question concerning the 
classification of animal minds to which such comparison may 
ultimately lead. Lastly, around and outside all the objects 
of these sciences as such, there lies the broad expanse of 
General Thought, into which these sciences, in all their 
stages, throw out branches of inference. It is needless to 
say that of late years the interest with which the unpre- 
cedented growth of these branches is watched has become so 
universal and intense, that it may be said largely to have 
absorbed the more exclusive sources of interest which I have 
enumerated. 

With the view of furthering these various lines of interest, 
I have undertaken a somewhat laborious enquiry, part of 
which has already been published in the International 
Scientific Series, and a further instalment of which is con- 
tained in the present volume. The two works, therefore, 
" Animal Intelligence " and " Mental Evolution in Animals," 
although published separately, are really one ; and they have 
been divided only for the following reasons. In the first 
place, to have produced the whole as one volume would have 



INTKODUCTION. 7 

been to present a book, if not of inconvenient bulk, at least 
quite out of keeping with the size of all the other books in 
the same series. Moreover, the subject-matter of each work, 
although intimately related to that of the other, is never- 
theless quite distinct. The first is a compendium of facts 
relating to Animal Intelligence, which, while necessary as a 
basis for the present essay, is in itself a separate and distinct 
treatise, intended to meet the interest already alluded to as 
attaching to this subject for its own sake ; while the second 
treatise, although based upon the former, has to deal with a 
wider range of subject-matter. 

It is evident that, in entering upon this wider field, I shall 
frequently have to quit the narrower limits of direct obser- 
vation within which my former work was confined ; and it is 
chiefly because I think it desirable clearly to distinguish 
between the objects of Comparative Psychology as a science, 
and any inferences or doctrines which may be connected with 
its study, that I have made so complete a partition of the 
facts of animal intelligence from the theories which I believe 
these facts to justify- 
So much, then, for the reasons which have led to the form 
of these essays, and the relations which I intend the one to 
bear to the other. I may now say a few words to indicate 
the structure and scope of the present essay. 

Every discussion must rest on some basis of assumption ; 
every thesis must have some hypothesis. The hypothesis 
which I shall take is that of the truth of the general theory 
of Evolution : I shall assume the truth of this theory so far 
as I feel that all competent persons of the present day will 
be prepared to allow me. I must therefore first define what 
degree of latitude I suppose to be thus conceded. 

I take it for granted, then, that all my readers accept the 
doctrine of Organic Evolution, or the belief that all species of 
plants and animals have had a derivative mode of origin by 
way of natural descent ; and, moreover, that one great law or 



8 INTRODUCTION. 

method of the process has been natural selection, or survival 
of the fittest. If anyone grants this much, I further assume 
that he must concede to me the fact, as distinguished from tlie 
manner and history of Mental Evolution, throughout the whole 
range of the animal kingdom, with the exception of man. I 
assume this because I hold that if the doctrine of Organic 
Evolution is accepted, it carries with it, as a necessary 
corollary, the doctrine of Mental Evolution, at all events as 
far as the brute creation is concerned. For throughout the 
brute creation, from wholly unintelligent animals to the most 
highly intelligent, we can trace one continuous gradation ; so 
that if we already believe that all specific forms of animal 
life have had a derivative origin, we cannot refuse to believe 
that all the mental faculties which these various forms 
present must likewise have had a derivative origin. And, as 
a matter of fact, we do not find anyone so unreasonable as to 
maintain, or even to suggest, that if the evidimce of Organic 
Evolution is accepted, the evidence of Mental Evolution, 
within the limits which I have named, can consistently be 
rejected. The one body of evidence therefore serves as a 
pedestal to the other, such that in the absence of the former 
the latter would have no locus standi (for no one could well 
dream of Mental Evolution were it not for the evidence of 
Organic Evolution, or of the transmutation of species) ; while 
the presence of the former irresistibly suggests the necessity 
of the latter, as the logical structure for the support of which 
the pedestal is what it is. 

It will be observed that in this statement of the case I 
have expressly excluded the psychology of man, as being a 
department of comparative psychology with reference to 
which I am not entitled to assume the principles of Evolu- 
tion. It seems needless to give my reasons for this exclusion 
For it is notorious tliat from the hour when Mr. Darwin and 
Mr. Wallace simultaneously propounded the theory which 
has exerted so enormous an influence on the thought of the 



INTRODUCTION". 9 

present century, the difference between tlie views of these 
two joint originators of the theory has since been shared by 
the ever-increasing host of their disciples. We all know 
what that difference is. We all know that while Mr. Darwin 
believed the facts of human psychology to admit of being 
explained by the general laws of Evolution, Mr. Wallace does 
not believe these facts to admit of being thus explained. 
Therefore, while the followers of Mr. Darwin maintain that 
all organisms whatsover are alike products of a natural 
genesis, the followers of Mr. Wallace maintain that a distinct 
exception must be made to this general atement in the case 
of the human organism ; or at all events in the case of the 
human mind. Thus it is that the great school of evolutionists 
is divided into two sects ; according to one the mind of man 
has been slowly evolved from lower types of psychical exist- 
ence, and according to the other the mind of man, not having 
been thus evolved, stands apart, siti generis, from all other 
types of such existence. 

Now assuredly we have here a most important issue, and 
as it is one the discussion of which will constitute a large 
element of my work, it is perhaps desirable that I should 
state at the outset the manner in which I propose to deal 
with it. 

The question, then, as to whether or not human intelli- 
gence has been evolved from animal intelligence can only be 
dealt with scientifically by comparing the one with the other, 
in order to ascertain the points wherein they agree and the 
points wherein they differ. Now there can be no doubt that 
when this is done, the difference between the mental faculties 
of the most intelligent animal and the mental faculties of the 
lowest savage is seen to be so vast, that the hypothesis of 
their being so nearly allied as Mr. Darwin's teaching implies, 
appears at first sight absurd. And, indeed, it is not until we 
have become convinced that the theory of Evolution can 
alone afford an explanation of the facts of human anatomy, 



10 INTEODUCTION. 

that we are prepared to seek for a similar explanation of the 
facts of human psychology. But wide as is the difference 
between the mind of a man and the mind of a brute, we must 
remember that the question is one, not as to degree, but as to 
kind ; and therefore that our task, as serious enquirers after 
truth, is calmly and honestly to examine the character of the 
diiierence which is presented, in order to determine whether 
it is really beyond the bounds of rational credibility that the 
enormous interval which now separates these two divisions of 
mind can ever have been bridged over, by numberless inter- 
mediate gradations, during the untold ages of the past. 

AVhile writing the first chapters of the present volume, I 
intended that the latter half of it should be devoted to a con- 
sideration of this question, and therefore in " Animal Intelli- 
gence" I said that such would be the case. But as the 
work proceeded it soon became evident that a full treat- 
ment of this question would require more space than could 
be allowed in a single volume, without seriously curtailing 
both the consideration of this question itself and also that of 
Mental Evolution, as this is exhibited in the animal kingdom. 
I therefore determined on restricting the present essay to a 
consideration of Mental Evolution in Animals, and on reserv- 
ing for subsequent publication all the material which I have 
collected bearing on Mental Evolution in Man. I cannot 
yet say how long it will be before I can feel that I am justified 
in publishing my researches concerning this branch of my 
subject; for the more that I have investigated it, the more 
have I found that it grows, as it were, in three dimensions — 
in depth, width, and complexity. But at whatever time I 
shall be able to publiaJi the third and final instalment of 
my work, it will of course rest upon the basis supplied by 
the present essay, as this rests upon the basis supplied by 
the previous one. 

It being understood, then, that the present essay is 
restricted to a consideration of Mental Evolution in Animals 



INTEODUCTION, 11 

I should like to have it also understood that it is further 
restricted to the psychology as distinguished from the philo- 
sophy of the subject. In a short and independent essay, 
published elsewhere,* I have already stated my views con- 
cerning the more important questions of philosophy into 
which the subject-matter of psychology is so apt to dip ; but 
here it is only needful to emphasize the fact that these two 
strata of thought, although assuredly in juxtaposition, are 
no less assuredly distinct. My present enquiry belongs only 
to the upper stratum, or to the science of psychology as dis- 
tinguished from any theory of knowledge. I am in no wise 
concerned with " the transition from the object known to the 
knowing subject," and therefore I am in no wise concerned 
with any of the philosophical theories which have been pro- 
pounded upon this matter. In other words, I have every- 
where to regard mind as an object and mental modifications as 
phenomena ; therefore I have throughout to investigate the 
process of Mental Evolution by what is now generally and 
aptly termed the historical method. I cannot too strongly 
impress upon the memory of those who from previous reading 
are able to appreciate the importance of the distinction, that 
I thus intend everywhere to remain within the borders of 
psychology, and nowhere to trespass upon the grounds of 
philosophy. 

On entering so wide a field of enquiry as that whose limits 
I have now indicated, it is indispensable to the continuity of 
advance that we should be prepared, where needful, to supple- 
ment observation with hypothesis. It therefore seems desira- 
ble to conclude this Introduction with a few words both to 
explain and to justify the method which in this matter I 
intend to follow. 

It has already been stated that the sole object of this 
work is that of tracing, in as scientific a manner as possible, 
the probable history of Mental Evolution, and therefore, of 

* Nineteenth Century, December, 1S82. 



12 INTRODUCTION. 

course, of enquiring into the causes which have determined it. 
So far as observation is available to guide us in tliis enquiry, 
I shall resort to no other assistance. Where, however, from 
the nature of the case, observation fails us, I shall proceed to 
inference. But though I shall use this method as sparingly 
as possible, I am aware that criticism will often find valid 
ground to object — ' It is all very well to map out the sup- 
posed genesis of the various mental faculties in this way, but 
we require some definite experimental or historical proof that 
the genesis in question actually did take place in the order 
and manner that you infer.' 

Now, in answer to this objection, I have only to say that 
no one can have a more lively appreciation than myself of 
the supreme importance of experimental or historical veri- 
fication, in all cases where the possibility of such verification 
is attainable. But in cases where such verification is not 
attainable, what are we to do ? "We may clearly do either of 
two things. We may either neglect to investigate the sub- 
ject at all, or we may Jo our best to investigate it by employ- 
ing the only means of investigation which are at our disposal. 
Of these two courses there can be no doubt which is the one 
that the scientific spirit prompts. The true scientific spirit 
desires to examine everything, and if in any case it is refused 
the best class of instruments wherewith to conduct the 
examination, it will adopt the next best that are available. 
In such cases science clearly cannot be forwarded by neglect- 
ing to use these instruments, while her cause may be greatly 
advanced by using them with care. This is proved by the 
fact that, in the science of psychology, nearly all the con- 
siderable advances which have been made, have been made, 
not by experiment, but by observing mental phenomena and 
reasoning from these phenomena deductively. In such cases, 
therefore, the true scientific spirit prompts us, not to throw 
away deductive reasoning where it is so frequently the only 



INTRODUCTION. 13 

instrument available, but rather to carry it with us, and to 
use it as not abusing it. 

And this, as I have said, is what I shall endeavour to do. 
No one can regret more than myself that the most interesting 
of all regions of scientific enquiry should happen to be the 
one in which experiment, or inductive verification, is least 
of all applicable ; but such being the case, we must take the 
case as we find it, use deductive reasoning where we clearly 
see that it is the only instrument available, but use it to as 
limited an extent as the nature of our subject permits. 



MENTAL EVOLUTION IN ANIMALS. 



CHAPTER I. 

The Ceiterion of Mind. 



The subject of our enquiry being Mental Evolution, it is 
desirable to begin by understanding clearly what we mean by 
Mind,* and then defining the conditions under which known 
Mind is invariably found to occur. In this chapter, therefore, 
I shall deal with what I take to be the Criterion of Mind, 
and shall then pass on in the next chapter to a consideration 
of the objective conditions under which alone Mind is 
observed to exist. 

It is obvious, then, to start with, that by Mind we may 
mean two very different things, according as we contemplate 
it in our own individual selves, or as manifested by other 
beings. Eor if I contemplate my own mind, I have an imme- 
diate cognizance of a certain flow of thoughts and feelings, 
which are the most ultimate things — and, indeed, the only 
things — of which I am cognizant. But if I contemplate 
Mind in other persons or organisms, I can have no such 
immediate cognizance of their thoughts and feelings ; I can 
only infer the existence of such thoughts and feelings from 
the activities of the persons or organisms which appear to 
manifest them. Thus it is that by Mind we may mean 
either that which is subjective or that wliich is objective. 
Now throughout the present work we shall have to consider 
Mind as an object ; and therefore it is well to remember that 
our only instrument of analysis is the observation of activities 

* It was necessary in nay -work on Animal Intelligence briefly to touch 
on this question ; therefore the parts of the analysis which are common to 
the two works I shall render as much as possible in the same words. 



16 MENTAL EVOLUTION IN ANIMALS. 

which we infer to be prompted by, or associated with, mental 
antecedents or accompaniments analogous to those of which 
we are directly conscious in our own subjective experience. 
That is to say, starting from what I know subjectively of the 
operations of my own individual mind, and of the activi- 
ties which in my own organism these operations seem to 
prompt, I proceed by analogy to infer from the observable 
activities displayed by other organisms, the fact that certain 
mental operations underlie or accompany these activities. 

From this statement of the case it will be apparent that 
our knowledge of mental activities in any organism other 
than our own is neither subjective nor objective. That it is 
not subjective I need not wait to show. That it is not 
objective may be rendered obvious by a few moments' reflec- 
tion. For it is evident that mental activities in other 
organisms can never be to us objects of direct knowledge ; as 
I have just said, we can only infer their existence from the 
objective sources supplied by observable activities of such 
organisms. Therefore all our knowledge of mental activities 
other than our own really consists of an inferential inter- 
pretation of bodily activities — this interpretation being 
founded on our subjective knowledge of our own mental 
activities. By inference we project, as it were, the known 
patterns of our own mental chromograph on what is to us 
the otherwise blank screen of another mind ; and our only 
knowledge of the processes there taking place is really due 
to such a projection of our own subjectively. This matter 
has been well and clearly presented by the late Professor 
Clifford, who has coined the exceedingly appropriate term 
eject (in contradistinction to subject and object), whereby to 
designate the distinctive character of a mind (or mental pro- 
cess) other than our own in its relation to our own. I shall 
therefore adopt this convenient term, and speak of all our 
possible knowledge of other minds as ejective. 

Now in this necessarily ejective method of enquiry, what 
is the kind of activities that we are entitled to regard as 
indicative of Mind ? I certainly do not so regard the flowing 
of a river or the blowing of a wind. Why ? First, because 
the subjects are too remote in kind from my own organism to 
admit of my drawing any reasonable analogy between them 
and it ; and, secondly, because the activities which they 
present are invariably of the same kind under the same cir- 



THE CEITERION OF MIND. 17 

cmnstances : they therefore offer no evidence of that which I 
deem the distinctive character of my own mind as such — 
Consciousness. In other words, two conditions require to be 
satisfied before we even begin to imagine that observable 
activities are indicative of mind ; the activities must be dis- 
played by a living organism, and they must be of a kind to 
suggest the presence of consciousness. What then is to 
be taken as the criterion of consciousness ? Subjectively., no 
criterion is either needful or possible ; for to me, individually, 
nothing can be more ultimate than my own consciousness, 
and, therefore, my consciousness cannot admit of any criterion 
having a claim to a higher certainty. But, ejectively, some 
such criterion is required, and as my consciousness cannot 
come within the territory of a foreign consciousness, I can 
only appreciate the latter through the agency of ambassadors 
— these ambassadors being, as I have now so frequently said, 
the observable activities of an organism. The next question, 
therefore, is. What activities of an organism are to be taken 
as indicative of consciousness ? The answer that comes most 
readily is, — All activities that are indicative of Choice ; 
wherever we see a living organism apparently exerting inten- 
tional choice, we may infer that it is conscious choice, and, 
therefore, that the organism has a mind. But physiology 
shows that this answer will not do ; for, while not disputing 
whether there is any mind without the power of conscious 
choice, physiology, as we shall see in the next chapter, is very 
firm in denying that all apparent choice is due to mind. The 
host of reflex actions is arrayed against the proposition, and, 
in view of such non-mental, though apparently intentional 
adjustments, we find the necessity for some test of the choice- 
element as real or fictitious. The only test we have is to ask 
whether the adjustments displayed are invariably the same 
under the same circumstances of stimulation. The only dis- 
tinction between adjustive movements due to reflex action, 
and adjustive movements accompanied by mental perception, 
consists in the former depending on inherited mechanisms 
within the nervous system being so constructed as to effect 
particular adjustive movements in response to particular 
stimulations, while the latter are independent of any such 
inherited adjustment of special mechanisms to the exigencies 
of special circumstances. Eeflex actions, imder the influence 
of their appropriate stimuli, may be compared to the actions 



18 MENTAL EVOLUTION IN ANIMALS. 

of a machine under the manipulations of an operator : when 
certain springs of action are touched by certain stimuli, the 
whole machine is thrown into appropriate action ; there is no 
room for choice, there is no room for uncertainty; but, as 
surely as any of these inherited mechanisms is affected by 
the stimulus with reference to which it has been constructed 
to act, so surely will it act in precisely the same way as it 
always has acted. But the case with conscious mental adjust- 
ment is quite different. For, without going into the question 
concerning the relation of Body and Mind, or waiting to ask 
whether cases of mental adjustment are not really quite as 
mechanical in the sense of being the necessary result or 
correlative of a chain of psychical sequences due to a physical 
stimulation, it is enough to point to the variable and incalcu- 
lable character of mental adjustments as distinguished from 
the constant and foreseeable character of reflex adjustments. 
All, in fact, that in an objective sense we can mean by a 
mental adjustment, is an adjustment of a kind that has not 
been definitely fixed by heredity as the only adjustment 
possible in the given circumstances of stimulation. Tor, were 
there no alternative of adjustment, the case, in an animal at 
least, would be indistinguishable from one of reflex action. 

It is, then, adaptive action by a living organism in cases 
where the inherited machinery of the nervous system does 
not furnish data for our prevision of what the adaptive action 
must necessarily be — it is only in such cases that we recog- 
nize the element of mind. In other words, ejectively con- 
sidered, the distinctive element of mind is consciousness, the 
test of consciousness is the presence of choice, and the 
evidence of choice is the antecedent uncertainty of adjustive 
action between two or more alternatives. To this analysis it 
is, however, needful to add that, although our only criterion 
of mind is antecedent uncertainty of adjustive action, it does 
not follow that all adjustive action in which mind is con- 
cerned should be of an antecedently uncertain character ; or, 
which is the same thing, that because some such action may 
be of an antecedently certain character, we should on this 
account regard it as non-mental. Many adjustive actions 
which we recognize as mental are, nevertheless, seen before- 
hand to be, under the given circumstances, inevitable ; but 
analysis would show that such is only the case when we have 
in view agents whom we already, and from independent 
evidence;, regard as mental. 



THE CRITERION OF MIND. 19 

In positing the evidence of Choice as my objective (or 
ejective) criterion of Mind, I do not think it necessary to 
enter into any elaborate analysis of what constitutes this 
evidence. In a subsequent chapter I shall treat fully of 
what I call the physiology or objective aspect of choice; and 
then it will be seen that from the gradual manner in which 
choice, or the mind-element, arises, it is not practically 
possible to draw a definite line of demarcation between 
choosing and non-choosing agents. Therefore, at this stage 
of the enquiry I prefer to rest in the ordinary acceptation of 
the term, as implying a distinction which common sense has 
always drawn, and probably always will draw, between mental 
and non-mental agents. It cannot be correctly said that a 
river chooses the course of its flow, or that the earth chooses 
an ellipse wherein to revolve round the sun. And similarly, 
however ccmiplex the operations may be of an agent recog- 
nized as non-mental — such, for instance, as those of a calcu- 
lating machine — or however impossible it may be to predict 
the result of its actions, we never say that such operations or 
actions are due to choice ; we reserve this term for operations 
or actions, however simple and however easily the result may 
be foreseen, which are performed, either by agents who in 
virtue of the non-mechanical nature of these actions prove 
themselves to be mental, or by agents already recognized as 
mental — i.e., by agents who have already proved themselves 
to be mental by performing other actions of such a non- 
mechanical or unforeseeable nature as we feel assured can 
only be attributed to choice. And there can be no reasonable 
doubt that this common-sense distinction between choosing 
and non-choosing agents is a valid one. Although it may be 
difficult or impossible, in particular cases, to decide to which 
of the two categories this or that being should be assigned, 
this difficulty does not affect the validity of the classification 
— any more, for instance, than the difficulty of deciding 
whether Limulus should be classified with the crabs or with 
the scorpions affects the validity of the classification which 
marks off the group Crustacea from the group Arachnida. 
The point is that, notwithstanding special difficulties in 
assigning this or that being to one or the other class, the 
psychological classification which I advocate resembles 
the zoological classification which I have cited ; it is a valid 
classification, inasmuch as it recognizes a distinction where 



20 MENTAL EVOLUTION IN ANIMALS. 

there is certainly something to distinguish. For even if we 
take the most mechanical view of mental processes that is 
possible, and suppose that conscious intelligence plays no 
part whatever in determining action, there still remains the 
fact that such conscious intelligence exists, and that prior to 
certain actions it is always affected in certain ways. There- 
fore, even if we suppose that the state of things is, so to 
speak, accidental, and that the actions in question would 
always be performed in precisely the same way whether or 
not they were thus connected with consciousness, it would 
still remain desirable, for scientific purposes, that a marked 
distinction should be drawn between cases of activity that 
proceed without, and those that proceed with this remarkable 
association with consciousness. As the phenomena of sub- 
jectivity are facts at any rate no less real than those of 
objectivity, if it is found that some of the latter are invariably 
and faithfully mirrored in those of the former, such pheno- 
mena, for this reason alone, deserve to be placed in a distinct 
scientific category, even though it were proved that the mirror 
of subjectivity might be removed without affecting any of the 
phenomena of objectivity. 

Without, therefore, entertaining the question as to the 
connexion between Body and Mind, it is enough to say that 
under any view concerning the nature of this connexion, we 
are justified in drawing a distinction between activities which 
are accompanied by feelings, and activities which, so far as 
we can see, are not so accompanied. If this is allowed, there 
seems to be no term better fitted to convey the distinction 
than the term Choice ; agents that are able to choose their 
actions are agents that are able to feel the stimuli which 
determine the choice. 

Such being our Criterion of Mind, it admits of being 
otherwise stated, and in a more practically applicable manner, 
in the following words which I quote from " Animal Intelli- 
gence :" — " It is, then, adaptive action by a living organism 
in cases where the inlierited machinery of the nervous system 
does not furnish data for our prevision of what the adaptive 
action must necessarily be — it is only here that we recognize 
the objective evidence of mind. The criterion of mind, 
therefore, which I propose, and to which I shall adhere 
throughout the present volume, is as follows : — Does the 
organism learn to make new adjustments, or to modify old 



THE CRITERTON OF MIND. 21 

ones, in accordance with the results of its own individual 
experience ? If it does so, the fact cannot be merely due to 
reflex action in the sense above described ; for it is impossible 
that heredity can have provided in advance for innovations 
upon or alterations of its machinery during the lifetime of a 
particular individual." 

Two points have to be observed with regard to this 
criterion, in whichever verbal form we may choose to express 
it. The first is tliat it is not rigidly exclusive either, on the 
one hand, of a possibly mental character in apparently non- 
mental adjustments, or, conversely, of a possibly non-mental 
character in apparently mental adjustments. For it is certain 
that failure to learn by individual experience is not always 
conclusive evidence against the existence of mind; such 
failure may arise merely from an imperfection of memroy, or 
from there not being enough of the mind-element present to 
make the adjustments needful to meet the novel circum- 
stances. Conversely, it is no less certain that some parts of 
our own nervous system, which are not concerned in the 
phenomena of consciousness, are nevertheless able in some 
measure to learn by individual experience. The nervous 
apparatus of the stomach, for instance, is able in so con- 
siderable a degree to adapt the movements of that organ to 
the requirements of its individual experience, that were the 
organ an organism we might be in danger of regarding it as 
dimly intelligent. Still there is no evidence to show that 
non-mental agents are ever able in any considerable measure 
thus to simulate the adjustments performed by mental ones ; 
and therefore our criterion, in its practical appKcation, has 
rather to be guarded against the opposite danger of denying 
the presence of mind to agents that are really mental. For, 
as I observed in " Animal Intelligence," " it is clear that long 
before mind has advanced sufficiently far in the scale of 
development to become amenable to the test in question, it 
has probably begun to dawn as nascent subjectivity. In 
other words, because a lowly organized animal does not learn 
by its own individual experience, we may not therefore con- 
clude that in performing its natural or ancestral adaptations 
to appropiate stimuli, consciousness, or the mind-element, is 
wholly absent ; we can only say that this element, if present, 
reveals no evidence of the fact. But, on the other hand, if a 
lowly organized animal does learn by its own individual 
2 



22 MENTAL EVOLUTION IN ANIMALS. 

experience, we are in possession of the best available evi- 
dence of conscious memory leading to intentional adaptation. 
Therefore, our criterion applies to the upper limit of non- 
mental action, not to the lower limit of mental." 

Or, again adopting the convenient terminology of Clifford, 
we must always remember that we can never know the mental 
states of any mental beings other than ourselves as objects ; 
we can only know them as ejects, or as ideal projections of our 
own mental states. And it is from this broad fact of psycho- 
logy that the difficulty arises in applying our criterion of 
mind to particular cases — especially among the lower animals. 
For if the evidence of mind, or of being capable of choice, 
must thus always be ejective as distinguished from objective, 
it is clear that the cogency of the evidence must diminish as 
we recede from minds inferred to be like our own, towards 
minds inferred to be not so like our own, passing in a gradual 
series into not-minds. Or, otherwise stated, although the 
evidence derived from ejects is practically regarded as good 
in the case of mental organizations inferred to be closely 
analogous to our own, this evidence clearly ceases to be trust- 
worthy in the ratio in which the analogy fails : so that when 
we come to the case of very low animals — where the analogy 
is least — we feel uncertain whether or not to ascribe to them 
any ejective existence. But I must again insist that this 
fact — which springs immediately out of the fundamental 
isolation of the individual mind — is no argument against my 
criterion of mind as the best criterion available ; it tends, 
indeed, to show that no better criterion can be found, for it 
shows the hopelessness of seeking such. 

The other point which has to be noted with regard to this 
criterion is as follows. I again quote from " Animal Intelli- 
gence :" — 

" Of course to the sceptic this criterion may appear un- 
satisfactory, since it depends, not on direct knowledge, but 
on inference. Here, however, it seems enough to point out, 
as already observed, that it is the best criterion available ; 
and, further, that scepticism of this kind is logically bound 
to deny evidence of mind, not only in the case of the lower 
animals, but also in that of the higher, and even in that of 
men other than the sceptic himself. For all objections which 
could apply to the use of this criterion of mind in the animal 
kingdom, would apply with equal force to the evidence of any 



THE CEITEKION OF MI^TD. 23 

mind other than that of the individual ohjector. This is 
obvious, because, as I have already observed, the only evi- 
dence we can have of objective mind is that which is 
furnished by objective activities ; and, as the subjective mind 
can never become assimilated with the objective so as to learn 
by direct feeling the mental processes which there accompany 
the objective activities, it is clearly impossible to satisfy any 
one who may choose to doubt the validity of inference, that 
in any case, other than his own, mental processes ever do 
accompany objective activities. 

" Thus it is that philosophy can supply no demonstrative 
refutation of idealism, even of the most extravagant form. 
Common-sense, however, universally feels that analogy is 
here a safer guide to truth than the sceptical demand for 
impossible evidence; so that if the objective existence of 
other organisms and their activities is granted — ^without 
which postulate comparative psychology, like all the other 
sciences, would be an unsubstantial dream — common sense 
will always and without question conclude that the activities 
of organisms other than our own, when analogous to those 
activities of our own which we know to be accompanied by 
certain mental states, are in them accompanied by analogous 
mental states." 



^ 



24 MENTAL EVOLUTION IN ANIMALS. 



CHAPTER II. 

The Structure and Tunctions of Nerve-Tissue. 

Having thus arrived at the best available Criterion of Mind 
considered as an eject, we have now to pass on to the topic 
which has already been propounded, viz., to a consideration 
of the objective conditions under which known mind is in- 
variably found to occur. 

Mind, then, so far as human experience extends, is only 
certainly known to occur in association with living organisms, 
and, still more particularly, in association with a peculiar 
kind of tissue which does not occur in all organisms, and even 
in those in which it does occur never constitutes more than 
an exceedingly small percentage of their bulk. This peculiar 
tissue, so sparingly distributed through the animal kingdom, 
and presenting the unique characteristic of being associated 
with mind, is, of course, the nervous tissue. It therefore 
devolves upon us, first of all, to contemplate the structure 
and the functions of this tissue, as far as it is needful for the 
purposes of our subsequent discussion that these should be 
clearly understood. 

Throughout the animal kingdom nerve-tissue is invariably 
present in all species whose zoological position is not below 
that of the Hydrozoa. The lowest animals in which it has 
hitherto been detected are the Medusae, or jelly-fishes, and 
from them upwards its occurrence is, as I have said, invari- 
able. Wherever it does occur its fundamental structure is 
very much the same, so that whether we meet with nerve- 
tissue in a jelly-fish, an oyster, an insect, a bird, or a man, 
we have no difficulty in recognizing its structural units as 
everywhere more or less similar. These structural units are 
microscopical cells and microscopical fibres. (Figs. 1, 2.) 

The fibres proceed to and from the cells, so serving to 



THE STRUCTUEE AND FUNCTIONS OF NERVE-TISSUE. 25 





Fig. 1. — Motor Nerve Cells connected by 
intercellular processes {b, b), and giving 
origin to outgoing fibres (c, c, c, and a). 
4. Multipolar cell containing much pig- 
ment around nucleus. Diagrammatic. 
(Vogt.) 



Fig. 2.— Multipolar Ganglion Cell from 
anterior grey matter of Spinal Cord 
of Ox, a, Axis cylinder process ; ft, 
branched processes, magnified 150 dia- 
meters. (Deiters.) 



connect tlie cells with one another, and also with distant 
parts of the animal body. The function of the fibres is that 
of conducting stimuli or impressions (represented by mole- 
cular or invisible movements) to and from the nerve-cells, 
while the function of the cells is that of originating those of 
the impressions which are conducted by the fibres outwards. 
Those of the impressions which are conducted by the fibres 
inwards, or towards the cells, are originated by stimuli affecting 
the nerve-fibre in any part of its length ; such stimuli may 
be contact with other bodies or pressure arising therefrom 
(mechanical stimuli), sudden elevations of temperature (ther- 
mal stimuli), molecular changes in the nerve-substance pro- 



26 MENTAL EVOLUTION IN ANIMALS. 

duced by irritants (chemical stimuli), effects of electrical 
disturbance (electrical stimuli), or lastly, the passage of a 
molecular disturbance from any other nerve- fibre with which 
the one in question may be connected. 

Nerve-cells are usually found collected together in aggre- 
gates, which are called ganglia, to and from which large 
bundles of nerve-fibres come and go. These rope-like 
clusters of nerve-fibres constitute the white threads and 
strings which we recognize as nerves when we dissect an 
animal, (See Fig. 3.) The relation of the clusters of 
fibres to the cluster of cells is now such as to supply the 
anatomical condition to the performance of a physiological 




Fig. 3. — Small Sympathetic Ganglion (human) with Multipolar 
Ceils. Magnified about 400 diameters. (Leydig.) 

process, which is termed Eeflex Action. If we suppose the 
left-hand bundle of fibres represented in the woodcut to be 
prolonged and to terminate in a sensory surface, while 
the other three bundles, when likewise prolonged, terminate 
in a group of muscles, then a stimulus falling upon the 
sensory surface would cause a molecular disturbance to travel 
along the left-hand or in-going nerve to the ganglion; on 
reaching the ganglion this disturbance would cause the 
ganglion to discharge its influence into the right-hand or out- 
going nerves, which would then conduct this disturbance into 
the group of muscles and cause them to contract. This pro- 
cess is called reflex action, because the original stimulus 
falling upon the sensory surface does not pass in a direct line 



THE STRUCTURE AND FUNCTIONS OF NERVE-TISSUE. 27 

to its destination in the muscles, but passes first to tlie 
ganglion, and is thence reflected from the sensory surface to 
the muscles.* This, which at first sight appears a round- 
about or cumbrous sort of process, is really the most economic 
that is available. For we must remember the enormous 
number and complexity of the stimuli to which all the higher 
animals are perpetually exposed, and the consequent neces- 
sity that arises for there being some system of co-ordination 
whereby these innumerable stimuli shall be suitably responded 
to. And such a system of co-ordination is rendered possible, 
and actually realized, through this principle of reflex action. 
For the animal body is so arranged that the innumerable 
nerve-centres, or ganglia, are all more or less in communica- 
tion one with another, and so receive messages from all parts 
of the body, to which they respond by sending appropriate 
messages down the nerve-trunks supplying the particular 
groups of muscles which under the given circumstances it is 
desirable to throw into contraction. In other words, when a 
stimulus falls upon the external surface of an animal, it is 
not diffused in a general way throughout the whole body of 
the animal, so causing general and aimless contractions of all 
the muscles ; but it passes at once to a nerve-centre, and is 
there centralized; the stimulus is dealt with in a manner 
which leads to an appropriate response of the organism to 
that stimulus. For the nerve-centres which receive the 
stimulus only reflect it to those particular muscle-groups 
which it is desirable for the organism, under the circumstances, 
to throw into action. Thus, to take an example, when a 
small foreign body, such as a crumb of bread, lodges in the 
windpipe, the stimulus which it there causes is immediately 
conveyed to a nerve-centre in the spinal cord, and this nerve- 
centre then originates, by reflex action, a highly complicated 
series of muscular movements which we call coughing, and 
which clearly have for their very special object the expul- 
sion of the foreign body from a position of danger to the 
organism. Now it is obvious that so complicated a series 
of muscular movements could not be performed in the 
absence of a centralizing mechanism ; and this is only one 
instance among hundreds of others that might be adduced of 

* The term, however, is not a happy one, because the process is some- 
thing more than the reflection of the original stimvilus or molecular disturb- 
ance ; the ganghon adds a new disturbance. 



28 MENTAL EVOLUTION IN ANIMALS. 

the co-ordinating power which is secured by this principle of 
reflex action. 

Of course we may wonder how it is that the nerve-centres, 
which preside over reflex action, not being endowed with 
consciousness, know what to do with the stimuli which they 
receive. The explanation of this, however, is that the ana- 
tomical arrangement of ganglion and nerves in any particular 
case is such as to leave no choice or alternative of action, if 
the apparatus is called into action at all. Thus, to begin at 
the bottom of the series, in the Medusae the simple ganglia 
are distributed all round the margin of the animal, and 
respond by reflex action to the stimuli which are applied at 
any other part of the surface. This has the effect of increas- 
ing the rate and the strength of the swimming-movements, 
and so of enabling the animal to escape from the source of 
danger. Now, although this is a true reflex action, and has 
an obvious purpose to serve, it does not involve any co-ordi 
nation of muscular movements. For the anatomical plan of 
a jelly-fish is so simple, that all the muscular tissue in the 
body is spread out in the form of one continuous sheet ; so 
that the only function which the marginal ganglia have to 
perform when they are stimulated into reflex action, is that 
of throwing into contraction one continuous sheet of muscular 
tissue. 

Hence we may infer that in its earliest stages reflex action 
is nothing more than a promiscuous discharge of nervous 
energy by nerve-cells, when they are excited by a stimulus 
passing into them from their attached nerve-fibres.* But as 
animals become more highly organized, and distinct muscles 
are by degrees set apart for the performance of distinct actions, 
we can readily understand how particular nerve-centres are 
likewise by degrees set apart to preside over these distinct 
actions ; the nervous centres then perform the part of trig- 
gers to the particular muscular mechanisms over which they 
preside — triggers which can only be loosened by the recep- 
tion of stimuli along their own particular lines of communi- 
cation, or nerves. Thus, for instance, in the star- fish — animals 
which are somewhat higher in the zoological scale than the 
jelly-fish, and which have a more highly de\'eloped neuro- 
muscular system — the ganglia are arranged in a ring round 

* For a full account of reflex action in Medusaj, see Phil. Trans., Croonian 
Lecture, 1875 ; also Phil. Trans., 1877 and 1880 



THE STRUCTURE AND FUNCTIONS OF NERVE-TISSUE. 29 

the bases of the five rays, into which they send, and from 
which they receive, nerve-fibres ; the ganglia are likewise 
connected with one another by a pentagonal ring of fibres. 
Now experiment shows that in this simple, and indeed geo- 
metrical plan of a nervous system, the constituent parts are 
able, when isolated by section, to preside over the movements 
of their respective muscles ; for if a single ray be cut off at 
its base, it will behave in all respects just like the entire star- 
fish — crawling away from injury, towards light, up perpen- 
dicular surfaces, and righting itself when turned upon its 
back. That is to say, the single nerve-centre at the base of 
a single separated ray is able to do for that ray what the 
entire pentagonal ring, or central nervous system, is able to 
do for the entire animal ; it is for that ray the trigger which, 
when touched by the advent of a stimulus, throws the mus- 
cular mechanism into appropriate action. Thus it is evident 
that each of the five nerve-centres stands in such anatomical 
relation to the muscles of its own ray, that when certain 
stimuli fall upon the ray, the process of reflex action leaves 
no choice of response. The beauty and delicacy of this 
mechanism is shown when in the unmutilated animal all the 
nerve-centres are in communication as one compound nerve- 
centre. For now, if one ray is irritated, all the rays will 
co-operate in making the animal crawl away from the source 
of irritation; if two opposite rays are simultaneously irri- 
tated, the star-fish will crawl away in a direction at right 
angles to an imaginary line joining the two points of irrita- 
tion. And, more prettily still, in the globular Echinus, or 
sea-urchin (which is, anatomically considered, a star-fish 
whose five rays have become doubled over in the form of an 
orange, soldered together and calcareous so as to make a 
rigid box), if two equal stimuli be applied simultaneously at 
any two points of the globe, the direction of escape will be 
the diagonal between them ; if a number of points be simul- 
taneously irritated, one effect neutralizes the other, and the 
animal rotates upon its vertical axis ; if a continuous zone of 
injury be made all the way round the equator, the same thing 
happens ; but if the zone be made wider at one hemisphere 
than the other, the animal will crawl away from the greatest 
amount of injury. So that in the Echinoderms the geometrical 
distribution of the nervous system admits of our making ex- 
periments in reflex action with very precise quantitative 



30 MENTAL EVOLUTION IN ANIMALS. 

results; we can, as it were, play upon this beautifully 
adjusted mechanism, so as to produce at will the balancing oi 
this stimulus against that one — the results, as expressed in 
the movements of the animal, being so many exemplifica- 
tions of the mechanical principle of the parallelogram of 
forces.* 

As we proceed through the animal series we find nervous 
systems becoming more and more integrated ; nerve-centres 
multiply, become larger, and serve to innervate more numerous 
and more complex groups of muscles. It is, however, need- 
less for me to devote space to describing this advance of 
structure, because the subject is one belonging to compara- 
tive anatomy. It is enough to say that everywhere the 
nervous machinery is so arranged that, owing to the ana- 
tomical plan of a nerve-centre with its attached nerves, there 
is no alternative of action presented to the nerve-centre 
other than that of co-ordinating the group of muscles over 
the combined contraction of which it presides. The next 
question, therefore, which arises is — How are we to explain 
the fact that the anatomical plan of a ganglion, with its 
attached nerves, comes to be that which is needed to direct 
the nervous tremours into the particular channels required ? 
The following is the theory whereby Mr. Herbert Spencer 
seeks to answer this question, and in order fully to under- 
stand it we must begin by noticing the effects of stimulation 
upon undifferentiated protoplasm. A stimulus, then, applied 
to homogeneous protoplasm, which is everywhere contractile 
and nowhere presents nerves, has the effect of giving rise to 
a visible wave of contraction, which spreads in all directions 
from the seat of stimulation as from a centre. A nerve, on 
the other hand, conducts a stimulus without undergoing any 
contraction, or change of shape. Nerves, then, are func- 
tionally distinguished from undifferentiated protoplasm by 
the property of conducting invisible or molecular waves of 
stimvilation from one part of an organism to another, so 
establishing physiological continuity between such parts 
without the necessary passage of visible waves of contraction. 

Now, beginning with the case of undifterentiated proto- 
plasm, Mr. Spencer starts from thje fact that every portion of 
the colloidal mass is equally excitable and equally contrac- 

* For a full account of these experiments, see Croonian Lecture, Phil. 
Trans., 188:i. 



THE STRUCTURE AND FUNCTIONS OF NERVE-TISSUE. 31 

tile. But soon after protoplasm begins to assume definite 
shapes, recognized by us as specific forms of life, some of its 
parts are habitually exposed to the action of forces different 
from those to which other of its parts are exposed. Conse- 
quently, as protoplasm continues to assume more and more 
varied forms, in some cases it must happen that parts thus 
peculiarly situated with reference to external forces will be 
more frequently stimulated to contract than are other parts 
of the mass. Now in such cases the relative frequency with 
which waves of stimulation radiate from the more exposed 
parts, will probably have the effect of creating a sort of polar 
arrangement of the protoplasmic molecules lying in the line 
through which these waves pass, and for other reasons also 
will tend ever more and more to convert these lines into 
passages offering less and less resistance to the flow of such 
molecular waves, — i.e., waves of stimulation as distinguished 
from waves of contraction. And lastly, when lines offering 
a comparatively low resistance to the passage of molecular 
impulses have thus been organically established, they must 
then continue to grow more and more definite by constant 
use, until eventually they become the habitual channels of 
communication between the parts of the contractile mass 
through which they pass. Thus, for instance, if such a line 
has been established between the points A and B of a con- 
tractile mass of protoplasm, when a stimulus falls upon A, a 
molecular wave of stimulation will course through that line 
to B, so causing the tissue at B to contract — and this even 
though no wave of contraction has passed through the tissue 
from A to B. Such is a very meagre epitome of Mr. Spencer's 
theory, the most vivid conception of which may perhaps be 
conveyed in a few words by employing his own illustration, 
viz., that just as water continually widens and deepens the 
channel through which it flows, so molecular waves of the 
kind we are considering, by always flowing in the same 
tissue tracts, tend ever more and more to excavate for them- 
selves functionally differentiated lines of passage. When 
such a line of passage becomes fully developed, it is a nerve- 
fibre, distinguishable as such by the histologist ; but before it 
arrives at this its completed stage, i.e., before it is observable 
as a distinct structure, Mr. Spencer calls it a " line of dis- 
charge."* 

* A certain amount of experimental verification lias been lent to this 



32 MENTAL EVOLUTION IN ANIMALS. 

Such being the manner in which Mr. Spencer supposes 
nerve-fibres to be evolved, he further supposes nerve-cells to 
arise in positions where a crossing or confluence of fibres 
gives rise to a conflict of molecular disturbances ; but it is 
unnecessary" for our present purposes to enter upon this more 
elaborate and less satisfactory part of his theory * All I 
desire now to point out is the a priori probability that 
nervous channels become developed where they are required 
simply from the fact of their being required — that is by use. 

And this d priori probability derives so much confirma- 
tion from facts that it is scarcely possible to refrain from 
accepting it as an answer to the question above propounded, 
namely, How are we to explain the fact that the anatomical 
plan of a ganglion with its attached nerves comes to be that 
which is needed to direct the nervous tremours into the par- 
ticular channels required ? It is a matter of daily observa- 
tion that " practice makes perfect," and this only means 
that the co-ordinations of muscular movement which are 
presided over by this or that nerve-centre admit of more 
ready performance the more frequently they have been pre- 
viously performed — which, in turn, only means that the dis- 
charges taking place in the nerve-centre travel more and 
more readily through the channels or nerve-fibres which are 
being rendered more and more permeable by use. So much, 
indeed, is this the case, that when an associated muscular 

theory by my own work on the physiology of nerves in Medusae. For a full 
account of this, I may refer to a lecture published in the Proceedings of the 
Royal Institution for 1877, on " Evolution of Nerres." The principal facts 
are that when physiological continuity of a sheet of neuro-muscular tissue is 
inteiTupted by overlapping or spiral sections, so that the passage both of 
visible or muscular waves of contraction and invisible or molecular waves of 
stimulation are blocked, after a long succession of contraction waves are 
allowed to break upon the shore of the physiological interruption, they at 
last begin to force a passage, and very soon this passage becomes perfectly 
free, so that neither the waves of contraction nor those of stimulation are 
any longer hindered. Whether in such a case a definite nerve-fibre is de- 
veloped, or only a " line of discharge," I cannot say ; but most probably the 
passage is effected tlu-ough previously existing fibres of the plexus which 
become more functionally developed by their increase of activity. 

* Less satisfactory, not only because more speculative, but because the 
whole weight of embryological and histological evidence appears to me to be 
opposed to the speculation. For the whole weight of this evidence goes to 
show that nerve-cells are the result of the specialization of epithelial or epi- 
dermal cells— that is, that they arise, not out of undifferentiated protoplasm, 
but by way of a further differentiation of a particular kind of already dif- 
ferentiated tissue, where this is exposed to particular kinds of stimulation. 



THE STRUCTURE AND FUNCTIONS OF NERVE-TISSUE. 33 

movement takes place with sufficient frequency, it cannot by 
any effort of the will become again dissociated ; as is the case, 
for instance, with the associated movement of the eyeballs, 
which does not begin to obtain till some days after birth, but 
which then soon becomes as closely organized as any of the 
associated movements in the muscles of the limbs.* 

And if this is the case even in the life-time of individuals, 
we can scarcely wonder that in the life-time of species heredity 
with natural selection should still more completely adapt the 
anatomical plan of ganglia, with their attached nerves, to the 
performance of the most useful — i.e., the most habitual — 
actions. Thus we may see in a general way how such nervous 
machinery may at last come to be differentiated into specially 
distributed anatomical structures, which, on account of their 
special distribution, are adapted to minister only to particular 
co-ordinations of muscular movements. That is to say, we 
are thus able to understand the rise and development cf 
Eeflex Action. 

* Mr. Darwin called my attention to the following passage in the writinga 
of Lamarck {Phil. Zool., torn, ii, pp. 318-19) : — " Dans toute action, le 
fluide des nerfs qui la provoque, subit un mouTement de deplacement qui y 
donne lieu. Or, lorsque cette action a ete plusieurs fois repetee, il n'est pas 
douteux que le fluide qui I'a executee, ne se soit fraye une route, qui lui 
devient alors d'autant plus facile a parcourir, qu'il I'a effectivement plus 
Bouvant franchie, et qu'il n'ait lui-meme une aptitude plus grand ^ suivre 
cette route frayee que celles qui le sont moins." 



34 MENTAL EVOLUTION IN ANIMALS. 



CHAPTER III. 

The Physical Basis of Mind. 

We have already taken it for granted that Mind has a 
physical basis in the functions of the nervous system, or that 
every mental process has a corresponding equivalent in some 
neural process. I shall next endeavour to show how precise 
this equivalency is. 

We have seen that ganglionic action consists of waves of 
nervous tremours originating in the cells, coursing along the 
attached fibres to other cells, and there arousing fresh impulses 
of the same kind. Moreover, we have seen that this coursing 
of nervous impulses through nervous arcs is not, as it were, 
promiscuous, but that, owing to the anatomical plan of a 
ganglion, it takes place in certain determinate directions, so 
that the result, when expressed in muscular movement, shows 
the function of a ganglion to be that of centraUzing nervous 
action, or of directing nervous tremours into definite channels. 
Lastly, we have seen that this directing or centralizing 
function of ganglia has probably in all cases been due to the 
principle of use combined with that of natural selection. 
Now it is known from experiments on the lower animals, as 
well as from the effects of cerebral disease in man, that the 
part of the nervous system in all the Vertebrata which 
appears to be exclusively concerned in all mental operations, 
is the so-called " large brain," or cerebral hemispheres. This 
is the convoluted part of the brain which appears imme- 
diately below the skull, and is above all the series of ganglia 
or nerve-centres which occupy the rest of the cerebro-spinal 
tract. As some at least of the bewildering multitude of cells 
and fibres which constitute the cerebral hemispheres are in 
connection with these lower ganglia, there is no doubt that 
the hemispheres are able to " play down " upon these ganglia 
as upon so many mechanisms, whose function it is to throw 



THE PHYSICAL BASIS OF MIND. 35 

this and that group of muscles into action. Much light is at 
present being thrown upon this subject by the researches of 
Hitzig, Fritsch, Terrier, Goltz, and others ; but we must pass 
on to consider that function of these great nerve-centres with 
which we shall henceforth be exclusively concerned, the 
function, namely, of being associated with the phenomena of 
Mind. 

As the cerebral hemispheres pretty closely resemble in 
their intimate structure ganglia in general, there can be no 
reasonable doubt that the mode of their operation is substan- 
tially the same ; and as such operation is here attended with 
the phenomena of subjectivity, there can be equally little 
doubt that such phenomena must constitute a sort of obverse 
reflection of ganglionic action. Looking, then, upon this 
obverse reflection, can we detect any fundamental principles 
of mental operation which may reasonably be taken to corre- 
spond with the fundamental principles of ganglionic opera- 
tion? 

The most fundamental principle of mental operation is 
that of memory, for this is the conditio sine qtid non of all 
mental life. But memory on its obverse side, or the side of 
physiology, can only mean that a nervous discharge, having 
once taken place along a certain route, leaves behind it a 
molecular change, more or less permanent, such that when 
another discharge afterwards proceeds along the same route, 
it finds, as it were, the footprints of its predecessor. And 
this, as we have seen, is no more than we find to be the case 
with ganglionic action in general. Even long before move- 
ments involving muscular co-ordination have been repeated 
with sufficient frequency to become consolidated into one 
organized and indissoluble act, they become, in virtue of the 
principle which I have termed the principle of use, more and 
more easy to repeat ; in all but in the absence of a mental 
constituent the nerve-centre concerned remembers the pre- 
vious occurrence of its own discharges ; these discharges have 
left behind them an impress upon the structure of the 
ganglion just the same in kind as that which, when it has 
taken place in the structure of the cerebral hemispheres, we 
recognize on its obverse side as an impress of memory. The 
analogy is much too close to be attributed to accident, for it 
extends into all details. Thus, a ganglion may forget its 
previous activity if too long an interval is allowed to elapse 



36 MENTAL EVOLUTION IN ANIMALS. 

between the repetitions of its activity, as every one must 
know who is in the habit of playing on a musical instrument, 
or performing any other actions entailing the acquirement of 
dexterity. It may also be observed that when such is the 
case the particular activity forgotten by the ganglion may be 
more easily re-acquired than originally it was acquired, which 
is just what we find to be the case with mental attainments. 

As particular illustrations of these facts I may state two 
or three cases, which will also serve to show of how little 
importance (on the objective side) is the occurrence of con- 
sciousness to the memory of a ganglion. 

Eobert Houdin early in life practised the art of juggling 
with balls in the air, and after a month's practice was able to 
keep four balls in the air at once. His neuro-muscular 
machinery was now so well trained, or remembered so well 
how to perform the series of actions required, that he could 
afford to withdraw his attention from the performance to the 
extent of reading a book without hesitation while keeping 
up the four balls. Thirty years afterwards, on trying the 
same experiment, having scarcely once handled the balls 
between times, he found that he could still read with ease 
while keeping up three balls ; the ganglia concerned had 
partly forgotten their work, but on the whole remembered it 
wonderfully well. Again, Lewes gives the case of a waiter 
asleep at a coffee-house, with much noise of talking around 
him, who was instantly aroused by a low cry of " Waiter ;" 
and Dr. Abercrombie gives the case of a man who had long 
been in the habit of taking down a repeater watch from the 
head of his bed to make it strike the last hour, and who 
was observed to do this when otherwise apparently uncon- 
scious from a fit of apoplexy. But perhaps the most remark- 
able of all the cases that can be adduced are the most familiar 
ones of walking and speaking. When we remember the 
immense amount of neuro-muscular co-ordination that is 
required for either of these actions, and the laborious steps 
by which each of them is first acquired in early childhood, it 
is indeed astonishing that in after life they come to be per- 
formed without thought of their performance ; the ganglia 
concerned have fully learned their work. 

So much for memory. But memory would be a useless 
faculty of mind if it did not lay the basis for another, and 
really the most important principle of subjectivity j I mean 



THE PHYSICAL BASIS OF MIND. 37 

the Association of Ideas. This is the root and branch of the 
whole structure psychological, and therefore, if mind has a 
physical basis, we should expect to meet with some very 
general and essential feature of ganglionic action answering 
to this very general and essential feature of mental action. 
And this, beyond question, we do find. 

For the association of ideas is merely a development of 
simple memory. A mental impression, image, memory, or 
idea having once occurred in juxtaposition with another, not 
only are the two memories remembered, but also the fact of 
their juxtaposition, so that when one memory or idea is 
aroused, the other is aroused likewise. Let us, then, look at 
the matter a little more closely, in order to see how this great 
principle of psychology may receive its explanation, so far as 
the collateral principle of physiology is concerned. 

There can be no doubt that in the complex structure of 
the cerebral hemispheres one nervous arc {i.e., fibres, cells, 
and fibres) is connected with another nervous arc, and this 
with another almost ad infinitum ; and there can be equally 
little doubt that processes of thought are accompanied by 
nervous discharges taking place, now in this arc, and now in 
that one, according as the group of nerve-cells in each arc is 
excited to discharge its influence by receiving a discharge 
from some of the other nerve-arcs with which it is united. 
Again, as we have seen, it is practically certain that the 
more frequently a nervous discharge takes place through a 
given group of nervous arcs, the more easy will it be for sub- 
sequent discharges to take place along the same routes — these 
routes having been thus rendered more permeable to the pas- 
sage of subsequent discharges. And now a very little reflec- 
tion will show that in this physiological principle we no 
doubt have the objective side of the psychological principle 
of the association of ideas. Eor it may be granted that a 
series of discharges taking place through the same group of 
nervous arcs will always be attended with the occurrence of 
the same series of ideas ; and it may be further granted that 
the previous passage of a series of discharges through any 
group of nervous arcs, by making the route more permeable, 
will have the effect of making subsequent discharges pursue 
the same course when started from the same origin. And if 
these two propositions be granted, it follows that the tendency 
of ideas to recur in the same order as that in which thev 



38 MENTAL EVOLUTION IN ANIMALS. 

have previously occurred, is merely a psycliological expres- 
sion of the psychological fact that lines of discharge become 
more and more permeable by use. 

We thus see that the most fundamental of physiological 
principles — the association of ideas — is merely an obverse 
expression of the most fundamental of neurological principles 
— reflex action ; and that such, in general terms, is the fact, 
seems to be proved beyond question by such instances as 
those above given of the sleeping waiter and Dr. Abercrombie's 
unconscious patient, &c. ; for such cases prove that actions 
originally due to a conscious association of ideas may, by a 
sufficiently loug course of ganglionic instruction, cease to be 
conscious actions, and therefore become in no way distin- 
guishable from reflex actions.* 

But the proof of the fundamental correlation between 
ganglioriic action and mental action does not end even 
here. There is another line of evidence which, although 
perhaps not quite so definite, nevertheless seems to me most 
cogent, and even more interesting than the considerations 
already adduced. If we take ideation to be in the same 
sense an index of the higher or more complex nervous pro- 
cesses, as muscular movement is of the lower or less complex, 
we shall find evidence to show that the development of 
ideation, or mental evolution, implies a further and continuous 
development of the corresponding nervous processes, which 
is precisely the same in kind as that which on the lower 
plane (that of muscular movement) has led to the advancing 
development of muscular co-ordination. In other words, if 
we consent to change the index from muscles to ideas, w^e 
shall find evidence that the method of nervous evolution has 
throughout been uniform ; we shall find that the progressive 
elaboration of nervous structures — which in the one case has 
found expression in the growing complexity of the muscular 
system, and in the other case has been reflected in the 
advancing phases of mental evolution — we shall find that this 
progressive elaboration has throughout been pervaded by the 
same principles of development, 

* A good instance of this may be found in the fact that men always bring 
their knees together in order to catch a small falling object, such as a coin, 
while women always spread their knees apart. The reason of course is that 
the difference of dress has led to a difference of organized habit — the habit 
in each case having been originally due to intelligent adjustment, but now 
scarcely distinguishable from a reflex. 



THE PHYSICAL BASIS OF MIND. 39 

Disregarding the philosophical question as to how nervous 
action is associated with subjective ideation, and concerning 
ourselves only with the scientific fact that it is thus associated, 
we may most clearly appreciate the parallel which I am about 
to draw if we regard the objective processes as the causes of 
the subjective. Whether or not such is really the case 
matters nothing to the exposition on which I am about to 
enter ; for I throughout take it for granted that the association 
of neurosis and psychosis is as invariable and precise as it 
would be were it proved to be due to a relation of causality. 
Placing therefore neurosis for the purposes of my argument 
as the cause of psychosis, I desire to show that there is a 
very exact parallel between the ganglionic action which pro- 
duces subjective ideation and that which produces muscular 
co-ordination; I desire to show that if we interpret the 
phenomena of ideation in terms of the nervous activity 
which is supposed to produce it, we shall find that this 
activity is just the same in all its laws and principles as that 
which produces muscular co-ordination. 

No doubt it sounds absurd, and from a philosophical 
point of view alone it is absurd, to speak of ideas as the 
psychological equivalents of muscles. So far as subjective 
analysis could teach us, it certainly does not seem that an 
idea presents any further kinship to a muscle than it does to 
a stone, or to the moon ; but when we look at the matter 
from the objective side, we perceive that the kinship is most 
intimate. Taking it for granted that the same idea is only 
and always aroused during the activity of the same nervous 
structure, element, or group of cells and fibres, it follows that 
any particular mental change resembles any particular mus- 
cular contraction in so far as it is the terminal result of the 
activity of a particular nervous structure. The incongruity 
of comparing a mental change to a muscular contraction 
arises, of course, from the emphatic distinction which must 
always be felt to exist between mental and dynamical pro- 
cesses. Physiology, which is concerned only with the dyna- 
mical processes, can take no cognizance of anything that 
happens in the region of mind. It can trace nervous action 
leading to combined muscular movements of greater and 
greater intricacy as we ascend to more and more elaborated 
mechanisms; but even when we reach the brain of man, 
physiology can have nothing to do with the mental side of 



40 MENTAL EVOLUTION IN ANIMALS. 

the nervous processes. All that physiology can see in these 
processes is a greatly improved power of discriminating 
between stimuli, and of issuing impulses to a correspondingly 
greater number and variety of adaptive movements ; the 
mental changes which accompany these nervous processes are 
as wholly without the ken of physiology as these nervous 
processes are without the ken of subjectivity. Therefore it 
is that when we speak of an idea as the analogue of a muscle, 
we feel the incongruity of confusing two things which are 
separated from one another by the whole interval that 
divides subject from object. But although in speaking of an 
idea as the analogue of a muscle, we do and ought to feel the 
incongruity, let it not be supposed that by thus speaking we 
are allowing ourselves to be betrayed into any confusion of 
thought. I speak of a mental change as the analogue of a 
muscular contraction only with reference to its being the ter- 
minal event invariably associated (whether by way of 
causality or not) with the activity of a nervous structure. 
And if we do not seek to press the analogy further than this, 
there is no fear of our confusing ideas which ought always to 
be kept fundamentally distinct. 

So much, then, by way of introduction to the point which 
I have to make plain. Now it admits of being abundantly 
proved that throughout the animal kingdom, so long as we 
regard the muscular system as our index of the structural 
advances taking place in the nervous system, we find this 
index to consist in the growing complexity of the muscular 
system, and the consequent increase in the number and 
variety of co-ordinated movements which this system is 
enabled to execute. Therefore the point which I have to 
prove will be proved if I can make it clear that the process 
of mental evolution bears some such resemblance to that of 
muscular evolution as we should expect that it ought to bear, 
if they are both dependent on a similar process of nervous 
evolution. In other words, I have to show that the process 
of mental evolution consists essentially in a progressive 
co-ordination of progressively developing mental faculties, 
analogous to that which takes place in muscular movements. 

Beginning with the faculties of simple sensation, we 
know, for instance, that when a note of music is struck, it 
appears to produce a single vibration, and yet physical ana- 
lysis shows that the sound is not a single vibration, but a 



THE PHYSICAL BASIS OF MIND. 41 

liighly complex structure of vibrations or harmonics, and that 
the ear takes in all these harmonics by as many separate 
nervous elements (whatever the elements may be which 
minister to the perception of pitch), although they are all 
blended into one compound sensation, which is so well com- 
pounded that the evidence supplied by it alone would never 
have led us to suspect that the sensation was other than 
simple. The same is known to be the case with sensations 
of colour, taste, and smell ; so that Lewes feels justified in 
going to the length of saying, " Every sensation is a group of 
sensible components."* And, taking the same view on the 
psychological side as I take, he further says in general terms, 
" The main fact on which our exposition rests is indisputable, 
namely, that sensation, perception, emotions, conceptions, are 
not simple undecomposable states, but variously com- 
pounded." 

To avoid being tedious, I shall not pursue the analysis 
through all the grades of the psychological faculties ; but, 
taking ideation in its widest sense, as including alike the 
mere memory of a sensation and the most complex process 
of abstract thought, I shall briefly show that it everywhere 
displays a grouping and compounding of subjective elements 
which, if translated into their objective counterparts, display 
precisely the same method of nervous evolution as that which 
obtains in the lower ganglia, as expressed by muscular co- 
ordination. 

As Bain observes, "Movements frequently conjoined 
become associated, or grouped, so as to arise in the aggregate 
at one bidding. Suppose the power of walking attained, and 
also the power of rotating the limbs, one may then be 
taught to combine the walking pace with the turning of the 
toes outward. Two volitions are at first requisite for this act, 
but after a time the rotation of the limb is combined with 
the act of walking, and, unless we wish to dissociate the two, 
they go together as a matter of course ; the one resolution brings 

on the combined movement Articulate speech 

largely exemplifies the aggregation of muscular movements 
and positions. A concurrence of the chest, larynx, tongue, 
and mouth, in a definite group of exertions, is requisite for 
each alphabetical letter. These groupings, at first impossible, 

• Frollems, ^c, p. 260. 



42 MENTAL EVOLUTION IN ANIMALS. 

are, after a time, cemented with all the firmness of tlie 
strongest instinct." 

Precisely analogous to this process of blending many- 
separate muscular movements into one simultaneous and com- 
pounded movement, is the process of blending many simple 
ideas into one complex or compounded idea. Just as mus- 
cular co-ordination is dependent on the simultaneous action 
of a certain group of nerve-centres for the purpose of securing 
the combined action of a number of muscles, so we must 
suppose that a general or a composite idea is dependent on 
the simultaneous activity of several nerve-centres which 
riinister to the several component parts of the blended idea. 
The psychological side of this process has been so well ex- 
pressed by James Mill, that I cannot do better than render it 
in his words : — " Ideas which have been so often conjoined 
that whenever one exists in the mind the other exists along 
with it, seem to run into one another, to coalesce, as it were, 
and out of many to form one idea, which idea, however, in 
reality complex, appears to be no less simple than any one of 

those of which it is compounded The word 

' gold,' for example, or the word ' iron,' appears to express as 
simple an idea as the word ' colour,' or the word ' sound.' 
Yet it is immediately seen that the idea of each of those 
metals is made up of the separate ideas of several sensa- 
tions : colour, hardness, extension, weight. Those ideas, how- 
ever, present themselves in such intimate union, that they 
are constantly spoken of as one, not many. We say, our 
idea of iron, our idea of gold ; and it is only with an effort 
that reflecting men perform the decomposition." And simi- 
larly, of course, with the most highly complex ideas, except 
that the more complex they become the greater is the diffi- 
culty of securing the needful composition, and the more easily 
do they undergo disintegration. Thus it is that, in the words 
of Mr. Spencer, " In the development of mind there is a pro- 
gressive consolidation of states of consciousness. States of 
consciousness once separate become indissoluble. Other states 
that were originally united with difficulty, grow so coherent 
as to follow one another without difficulty. And thus there 
arise large aggregations of states, answering to complex 
external things — animals, men, buildings — which are so 
welded together as to be practically single states. But this 
integration, by uniting a large number of related sensations 



THE PHYSICAL BASIS OF MIND. 43 

into one state, does not destroy them. Though subordinated 
as parts of a whole, they still exist."* 

Again, just as the principle of association is exhibited in 
the case of ideas not only with reference to the simultaneous 
blending of simple ideas into one complex idea, but also 
with reference to the successive sequence or concatenation of 
ideas ; so in the case of muscular co-ordinations we acquire, 
not only the power of a simultaneous co-operation of muscle- 
groups, but also that of a successive co-operation. For 
instance, as Professor Bain observes, " In all manual opera- 
tions there occur successions of movements so firmly asso- 
ciated, that when we will to do the first, the rest follow 
mechanically and unconsciously. In eating, the action of 
opening the mouth mechanically follows the raising of the 

morsel Although the learning of successions of 

movements involves the medium of sensation, in the first 
instance, yet we must assume that there is a power, in the 
system, for associating together movements as such." In 
fact, it might well have been added, there is such a power 
that manifests itself long before the dawn of any of the 
powers of the " will " ; it is as true of the polyp as of the man 
that " in eating, the act of opening the mouth mechanically 
follows the raising of the morsel." 

So with the highest or most abstract powers of mind. 
For abstraction merely means the mental dissociating of 
qualities from objects, and, in its higher phases, blending 
these qualities, or conceptions of them, into new ideal com- 
binations. 

Lastly, just as innumerable special mechanisms of mus- 
cular co-ordinations are found to be inherited, innumerable 
special associations of ideas are found to be the same ; and in 
one case as in the other, the strength of the organically 
imposed connection is found to bear a direct proportion to 
the frequency with which in the history of the species it has 
occurred. Thus, the simplest, oldest, and most constant 
ideas relating to time, space, number, sequence, &c., may be 
compared, in point of organic integrity, with the oldest and 
most indissolubly associated muscular movements, such as 
those concerned in breathing, deglutition, and visceral 
motions. Again, inherited instincts have their counterparts 
in such inherited muscular co-ordinations as are not abso- 

* Principles of Psychology, vol. ii, p. 476. 



44 MENTAL EVOLUTION IN ANIMALS. 

lutely indissoluble. And similarly, of course, associations of 
ideas acquired only during the life-history of the individual 
need to be more or less constantly maintained by repetition, 
just as muscular co-ordinations similarly acquired can only 
be maintained by practice. 

Upon the whole, therefore, it is impossible that there could 
be a more precise parallelism between these two manifesta- 
tions of nervous machinery, and it is one which for recog- 
nition in a general way does not require scientific analysis ; 
it has been perceived by the common sense of mankind — 
witness, for instance, the term " gymnastics " having become 
applicable to mental no less than to muscular co-ordinations. 
But, for the sake of systematic completeness, I shall conclude 
this exposition by briefly pointing out that all those patho- 
logical derangements which occur in the nervous centres that 
preside over muscular activities, have their parallels in 
similar derangements which occur in the nervous centres 
that are concerned in mental activities. Thus "nervous- 
ness," or a disturbance of the normal balance of nerve- 
centres, has a strikingly analogous effect in confusing the 
ideas and in perturbing muscular co-ordinations. Idiotcy has 
its parallel in inability to perform complex muscular move- 
ments, with which inability, indeed, idiotcy is itself almost 
invariably associated. Lunacy has it counterpart in an un- 
balanced, or badly correlated power of muscular co-ordina- 
tion, which in its graver manifestations is known as ataxy ; 
while mania is mental convulsion, and unconsciousness 
mental paralysis. 

I must not, however, take leave of this branch of our 
subject without briefly alhiding to a difl&culty which may 
occur to some minds, and which has been well stated by 
Professor Calderwood in his recently published work.* The 
difficulty to which I allude arises from there being an 
absence of such a constant relationship between the size or 
mass of the brain, and the degree of intelligence displayed 
by it, as the foregoing teaching would reasonably lead us to 
expect. 

Now, I do not deny that the relation of intelligence to 
size, mass, or weight of brain is a perplexing matter when 
we look to the animal kingdom as a whole ; for although 
there is unquestionably a general relation of a quantitative 

* Pp. 211—216. 

A . 



THE PHYSICAL BASIS OF IiIIND. 45 

kind, it is not a constant relation. Even within the limits of 
the hnman species this relation is not so precise as is usually- 
supposed ; for, neglecting particular cases that might be 
quoted of men of genius not having particularly large or 
heavy brains, the converse cases are perhaps in this connec- 
tion more remarkable — viz., those of feeble-minded persons 
having large and apparently well-formed brains. I am 
indebted to Dr. I'rederick Bateman of the Eastern Counties' 
Asylum for directing my attention to the observations of 
Dr. Mierzejewskis, which were published at the international 
congress of psychologists held in Paris in 1878. These 
observations, which appear to have been carefully made, 
seeing that casts of the brains were exhibited, went to show 
that idiotcy is compatible with large and apparently well- 
developed brains — the amount of grey matter in one instance 
being " enormous," 

And, if we turn to the animal kingdom, we find in a still 
larger measure that the mere amount of cerebral substance 
furnishes but a very uncertain index of the level of intelli- 
gence which is attained by the animal. This is the case 
even when we eliminate the element of complexity that is 
introduced by the differences which obtain in different 
animals between the bulk of the brain and the bulk of the 
body — small animals requiring a greater proportional bulk of 
brains than large ones, because the nervous machinery which 
ministers to muscular movement and co-ordination has in. 
both cases to be accommodated. But this element of com- 
plexity may be removed by considering the cases in which 
small animals exhibit remarkable intelligence ; and in this 
respect no animals are so remarkable as the more intelligent 
species of ants alluded to in my former work. As Mr. Darwin 
has observed, the brain of such an insect deserves to be 
regarded as perhaps the most wonderful piece of matter in 
the world. 

But if this whole question touching the relation between 
the mass of brain and degree of intelligence is felt to lie as 
a difficulty in the way of evolutionary theory, I should reply 
to it by the following considerations. 

In the first place, that there is a general relation between 
size of brain and degree of intelligence, both in the case of 
man and in that of animals, is unquestionable. It is, there- 
fore, only with the more special exceptions that we have to 



46 MENTAL EVOLUTION IN ANIMALS. 

deal. But here we have to remember that besides size or 
mass, there must certainly be a no less important factor to be 
taken into account — that, namely, of structure or complexity. 
Now we really know so little about the relations of intelli- 
gence to neural structure, that I do not think we are justified 
in forming any very strong conclusions a priori concerning the 
relation of intelligence to mere size or mass of brain. Know- 
ing in a general way that mass plus structure of brain is 
necessary for intelligence, we do not know how far the 
second of these two factors may be increased at the expense 
of the first. And, as a mere matter of complexity, or of 
multum in parvo, I am not sure that even the brain of an 
ant deserves to be considered more wonderful than the ovum 
of a human being. Lastly, in this connection it may be as 
well to observe that there is as good evidence to show the 
importance of cerebral structure as a factor in determining 
the level of mental development, as there is to show the 
importance of cerebral mass. Throughout the vertebrated 
series of animals the convolutions of the brain — which are 
the coarser expressions of more refined complexities of 
cerebral structure — furnish a wonderfully good general indi- 
cation of the level of intelligence attained; while in the 
case of ants Dujardin says that the degree of intelligence 
exhibited stands in an inverse proportion to the amount of 
cortical substance, or in direct proportion to the amount of the 
peduncular bodies and tubercles. In view of these con- 
siderations, therefore, I do not feel that the supposed diffi- 
culty, which I have thought it desirable to mention, is one of 
any real solidity. 



THE KOOT-PKINCIPLES OF MIND. 47 



CHAPTER IV. 

The Eoot-peinciples of Mind. 

Ai-THOUGH the phenomena of Mind, and so of Choice, are 
both complex, and as to their causation obscure, I think we 
have now seen that we are justified in beheving that they all 
present a physical basis. That is to say, whatever opinion 
we may happen to entertain regarding the ultimate nature of 
these phenomena, in view of the known facts of physiology, 
we ought all to be agreed concerning the doctrine that the 
mental processes which we cognize as subjective, are the 
psychical equivalents of neural processes which we recog- 
nize as objective. As already stated, I have elsewhere con- 
sidered the various hypotheses concerning the nature and the 
various attempts at an explanation of this equivalency 
between mental processes and neural processes ; but here I 
desire to consider the fact of this equivalency merely as a 
fact. It will therefore signify nothing to my discussion 
whether, with the materialists, we rest in this fact as final, or 
endeavour, with men of other schools, to seek an explanation 
of the fact of some more ultimate character. It is enough 
if we are agreed that every psychical change of which we 
have any experience is invariably associated with a definite 
phvsical change, whatever we may suppose to be the nature 
and significance of this association. 

Looking, then, at the phenomena of Mind as invariably 
presenting a physical, or, as we may indifferently call it, a 
physiological side, I shall endeavour to point out what I con- 
ceive to be the most iiltimate principle of physiology which 
analysis shows to be common to them all. On the mental 
side, as we have already seen, we have no difficulty in dis- 
tinguishing this ultimate principle, or common characteristic, 
as that which we designate by the term Choice. Now if the 
power of choice is the distinctive peculiarity of a mental 



48 MENTAL EVOLUTION IN ANIMALS. 

being, and if, as we have taken for granted, every change of 
Mind is associated with some change of Body, it follows that 
this distinctive peculiarity ought to admit of being trans- 
lated into some physiological equivalent. Further, if there 
is any such physiological equivalent to be found, we should 
expect to find it much lower down in the scale of physio- 
logical development than in the functions of the human 
brain. For not only do the lower animals manifest, in a 
long descending scale, powers of choice which gradually fade 
away into greater and greater simplicity ; but we should be 
led a priori to expect, if there is a physiological principle 
which constitutes the objective basis of the psychological 
principle, that the former should manifest itself more early 
in the course of evolution than the latter. For, whatever 
views we may entertain concerning the relation of Body 
and Mind, there can be no question, on the basis of the 
evolution theory which I assume, that, as a matter of his- 
torical sequence, the principles of physiology were prior to 
those of psychology; and therefore, if in accordance with 
our original agreement we allow that the latter have a phy- 
sical basis in the former, it follows that the principles of 
physiology, which now constitute the objective basis of 
choice, whatever they may be, probably came into operation 
long before they were sufficiently evolved thus to constitute 
the foundation of psychology. 

Now I think that the a priori expectation thus briefly 
sketched is fully realized in the occurrence of a physiological 
principle, which first appears very low down in the world of 
life, and which, in its relation to psychology, has not yet 
received the attention which it deserves. I may best state 
the principle by giving an example. I have observed that if 
a sea-anemone is placed in an aquarium tank, and allowed 
to fasten u]3on 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 with a turmoil 
of water and air-bubbles. Yet, after a short time, it becomes 
so accustomed to this turmoil tliat it will expand its tentacles 
in search oi food, just as it does when placed in calm water. 
If now one of the expanded 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 



THE ROOT-PKINCIPLES OF MIND. 49 

water. That is to say, the tentacles are able to discrimi- 
nate between the stimulus which is supplied by the turmoil 
of the water and that which is supplied by their contact 
Math the solid body, and they respond to the latter stimulus 
notwithstanding that it is of incomparably less intensity 
than the former. And it is this power of discriminating 
between stimuli, irrespective of their relative mechanical inten- 
sities, that I regard as the objective principle of which we are 
in search ; it constitutes the physiological aspect of Choice. 

A similar power of discriminative response has long been 
known to occur in plants, though the most carefully observed 
facts with regard to this interesting subject are those which 
we owe to the later researches of Mr. Darwin and his son. 
The extraordinary delicacy of discrimination which these 
researches show the leaves of plants to exercise between 
darkness and light of the feeblest intensity, is not less 
wonderful than the delicacy of discrimination which they 
show the roots of plants to exercise in feeling about for 
moisture and lines of least resistance in the soil. But in the 
present connection the most suggestive facts are those which 
have been brought to light by Mr. Darwin's previous re- 
searches on the climbing and insectivorous plants. For, 
from these researches it appears that the power of discrimi- 
nating between stimuli, irrespective of relative mechanical 
intensity or amount of mechanical disturbance, has here 
proceeded to an extent that rivals the function of nerve- 
tissue, although the tissues which manifest it have not in 
structure passed beyond the cellular stage. Thus, the tenta- 
cles of Drosera, which close around their prey like tlie 
tentacles of a sea-anemone, will not respond to the violent 
stimulation supplied by rain-drops falling upon their sensi- 
tive surfaces or glands, while they will respond to an incon- 
ceivably slight stimulus of the kind caused by an exceedingly 
minute particle of solid matter exerting by gravity a con- 
tinuous pressure upon the same surfaces. For Mr. Darwin 
says, " The pressure exerted by a particle of hair, weighing 
^^^y 7^740 of a grain, and supported by a dense fluid, must 
have been inconceivably slight. We may conjecture that it 
could hardly have equalled the millionth of a grain ; and we 
shall hereafter see that far less than the millionth of a grain 
of phosphate of ammonia in solution, when absorbed by a 
gland, acts on it and induces movement. ... It is 



50 MENTAL EVOLUTION IN ANIMALS. 

extremely doubtful wliether any nerve in the human body, 
even if in an inflamed condition, would be in any way 
affected by such a particle supported in a dense fluid, and 
slowly brought into contact with the nerve. Yet the cells 
of the glands of Drosera are thus excited to transmit a 
motor impulse to a distant point, inducing movement. It 
appears to me that hardly any more remarkable fact than 
this has been observed in the vegetable kingdom." 

But the case does not end here. For in another insec- 
tivorous plant, Dionoea, or Venus' Fly-trap, the principle of 
discriminating between different kinds of stimuli has been 
developed in a direction exactly the opposite to that which 
obtains in Drosera. For while Drosera depends for capturing 
its prey on entangling the latter in a viscid secretion from its 
glands, Dionoea closes upon its prey with the suddenness of 
a sprmg-trap ; and in relation to this difference in the mode 
of capturing prey, the principle of discrimination between 
stimuli has been correspondingly modified. In Drosera, as we 
have seen, it is the stimulus supplied by continuous 2>ressitre 
that is so delicately perceived, while the stimulus supplied 
by impact is disregarded ; but in Dionoea the smallest impact 
upon the irritable surfaces, or filaments, is immediately re- 
sponded to, while the stimulus supplied even by compara- 
tively great pressure upon the same surfaces is wholly 
disregarded. Or, in Mr. Darwin's own words, " Although the 
filaments are so sensitive to a momentary and delicate touch, 
they are far less sensitive than the glands of Drosera to pro- 
longed pressure. Several times I succeeded in placing on 
the tip of a filament, by the aid of a needle moved with 
extreme slowness, bits of rather thick human hair, and these 
did not excite movement, although they were more than ten 
times as long as those Avhich caused the tentacles of Drosera 
to bend ; and although in this latter case they were largely 
supported by the dense secretion. On the other hand, the 
glands of Drosera may be struck with a needle, or any hard 
object, once, twice, or even thrice, with considerable force, 
and no movement ensues. This singular difference in the 
nature of the sensitiveness of the filaments of Dionoea and 
of tlie glands of Drosera evidently stands in relation to the 
habits of the two plants. If a minute insect alights with its 
delicate feet on the glands of Drosera, it is caught by the 
vji^pi^ ^e6retion] and /the slight, though prolonged pressure 



V, 



LIB 



v.- ^ 



THE ROOT-PEINCIPLES OF MIND. 51 

gives notice of the presence of prey, which is secured by the 
slow bending of the tentacles. On the other hand, the sensi- 
tive filaments of Dionoea are not viscid, and the capture of 
insects can only be assured by their sensitiveness to a 
momentary touch, followed by the rapid closure of the lobes." 
So that in these two plants the power of discriminating 
between those two kinds of stimuli has been developed to an 
equally astonishing extent, but in opposite directions. 

But we find definite evidence of this power of discrimina- 
tive selection even lower down in the scale of life than the 
cellular plants; we find it even among the protoplasmic 
organisms. Thus, to quote an instructive case from Dr. Car- 
penter : — 

" The Deep-Sea researches on which I have recently been 
engaged have not ' exercised ' my mind on any topic so much 
as on the following : — Certain minute particles of living jelly, 
having no visible differentiation of organs .... build 
up ' tests ' or casings of the most regular geometrical sym- 
metry of form, and o£the most artificial construction . . . 
From the same sandy hottotn, one species picks up the coarser 
quartz-grains, cements them together with phosphate of iron 
(?), which must be secreted from their own substance; and 
thus constructs a flask-shaped * test ' having a short neck and 
a single large orifice. Another picks up the finer grains, and 
puts them together with the same cement into perfectly 
spherical ' tests ' of the most extraordinary finish, perforated 
with numerous small tubes, disposed at pretty regular inter- 
vals. Another selects the minutest sand-grain and the 
terminal points of sponge-spicules, and works these up 
together — apparently with no cement at all, but by the 
' laying ' of the spicules — into perfect spheres, like homoeo- 
pathic globules, each having a single fissured orifice." * 

Thus, co-extensive with the phenomena of excitability, 
that is to say, with the phenomena of life, we find this func- 
tion of selective discrimination ; and, as I have said, it is this 
function that I regard as the root-principle of Mind. I so 
regard it because, if we consider all the faculties of mind, we 
shall observe that the one feature which on their objective 
side they present as common, is this power of discriminating 
among stimuli, and responding only to those which, irrespec- 
tive of relative mechanical intensity, are the stimuli to which 
* Contem'porary 'Review, April, 1873 



62 MENTAL EVOLUTION IN ANIMALS. 

responses are appropriate. In order to see this, let lis take 
the principal faculties of mind in their ascending order, and 
consider Avhat they are, in their last analysis, upon their 
physiological side. First we have the organs of special 
Sensation, the physiological functions of which clearly con- 
stitute the basis of the whole structure psychological. Yet 
no less clearly, these functions in their last analysis are 
merely so many specially developed aptitudes of response to 
special modes of stimulation. Thus, for instance, the struc- 
ture of the eye is specially adapted to respond only to the 
particular mode of stimulation that is supplied by light, the 
ear to that which is supplied by sound, and so on. In other 
words, the organs of special sense are so many structures 
which have been variously and extremely differentiated in 
several directions, for the express purpose of attaining a 
severally extreme sensitiveness to special modes of stimula- 
tion without reference to any other mode. And this is 
merely to say that the function of an organ of special sense 
is that of sorting out, selecting, or discriminating the par- 
ticular kind of stimulation to which its responsive action is 
appropriate. 

Again, many of the nervous mechanisms which minister to 
various Eeflex Actions are only thrown into activity by special 
modes of stimulation. This is notably the case with those highly 
complicated neuro-muscular mechanisms which are thrown 
into activity only by the mode of stimulation which we call 
tickling. Such instances are of special interest in the present 
connexion from the fact that the distinguishing peculiarity of 
this mode of stimulation consists in its being a stimulation of 
low intensity. The comparatively violent stimulation that is 
caused by the passage of food down the gullet, or by contact 
of the soles of the feet with the ground, is unproductive of 
any response on the part of the mechanisms which are 
thrown into violent activity by the gentlest possible stimula- 
tion of the same surfaces. Similarly with regard to Instincts. 
These, physiologically considered, are the activities of highly 
differentiated nervous mechanisms which have been slowly 
elaborated, through successive generations, for the express 
purpose of responding to some particular stimulus of a highly 
wrought character, and which, on its psychological side, is a 
recognition of the circumstances to which the instinctive 
adjustment is appropriate. And so with the Emotions. For, 



THE ROOT-PKINCIPLES OF MIND 53 

pliysiologically considered, the emotions are the activities of 
highly wrought nervous mechanisms, and these activities are 
only excited by the very special stimuli which, on their sub- 
jective side, we recognize as the particular kind of ideas 
which are appropriate to call up particular emotions. We 
do not laugh at a painful sight, nor does a ludicrous sight 
cause us to weep ; and this, physiologically considered, 
merely means that the nervous machinery whose action is 
accompanied by one emotion, will only respond to one kind of 
very specialized and complex stimulation ; it will not respond 
to another and probably in many respects very similar kind of 
stimulation, which, nevertheless, is competent to evoke re- 
sponses from another and probably very similar piece of nervous 
machinery. And thus, also, it is with Eeasoning and Judg- 
ment. Eeasoning, on its physiological side, is merely a series 
of highly complicated nervous changes, regarding which tlie 
only thing we certainly know is, that not one of them can 
take place without an adequate physical accompaniment, and 
therefore that on its physiological side a train of reasoning is 
a series of nervous changes, every one of which must be 
produced by physical antecedents. And hence on its objec- 
tive side every step in a train of reasoning consists in a 
selective discrimination among all those exceedingly delicate 
stimuli which, on their subjective side, we know as argu- 
ments. Similarly regarded. Judgment is likewise nothing 
more than the final result of the incidence of a vast number 
of very delicate stimuli ; and this final result, like all the 
intermediate steps of the reasoning which led to it, is nothing 
more than the exercise of a power to discriminate between 
the stimulus which on its subjective side we recognize as the 
right, and that which we similarly recognize as the wrong. 
Lastly, Volition, subjectively considered, is the faculty of 
consciously selecting motives ; and motives, objectively con- 
sidered, are nothing more than immensely complex and 
inconceivably refined stimuli to nervous action. 

If we turn from the ascending scale of mental faculties 
in man, to the ascending scale of mind in the animal king- 
dom, we shall meet with further and still more definite evi- 
dence that the distinguishing property of mind, on its 
physiological side, consists in this power of discriminating 
between difi'erent kinds of stimuli, irrespective of their 
degrees of mechanical intensity. But, before giving a brief 



54 MENTAL EVOLUTION IN ANIMALS. 

review of the evidence on this point, I may here meet a 
difficulty which has already arisen. The difficulty is that I 
began by showing it necessary to define Mind as the power 
of exercising Choice, and then proceeded to define the latter 
as a power belonging only to agents that are able to feel. 
Yet, on looking at the objective side of the problem, I 
pointed out that the physiological or objective equivalent of 
Choice is found to occur in its simplest manifestations at 
least as low down as the insectivorous plants, which are 
certainly not agents capable, in any proper sense of the term, 
of feeling. Therefore it seems that my conception of what 
constitutes Choice is in antagonism with my view that the 
essential element of Choice is found to occur among organ- 
isms which cannot properly be supposed to feel. And this 
antagonism, or inherent contradiction, is a real one, though I 
hold it to be unavoidable. For it arises from the fact that 
neither Feeling nor Choice appears upon the scene of life 
suddenly. We cannot say, within extensive limits, where 
either can properly be said to begin. They both dawn 
gradually, and therefore in our everyday use of these terms 
we do not wait to consider where they are first applicable; 
we only apply them where we see their applicability to be 
apparent. But when we endeavour to use these same terms 
in strict psychological analysis, we are at once met with the 
difficulty of drawing the line where the terms are applicable 
and where they are not. There are two ways of meeting the 
difficulty. One is to draw an arbitrary line, and the other is 
not to draw any line at all ; but to carry the terms down 
through the whole gradation of the things until we arrive at 
the terminal or root-principles. By the time that we do arrive 
at these root-principles, it is no doubt true that our terms have 
lost all their original meaning ; so that we might as well call 
an acorn an oak, or an egg a chicken, as speak of a Dionoea 
feeling a fly, or of a Drosera choosing to close upon its prey. 
Yet this use, or rather let us call it abuse, of terms serves one 
important purpose if, while duly regarding the change of 
meaning which during their gradual descent the terms are 
made gradually to undergo, we thus serve to emphasize the 
fact that tliey refer to things which are the product of a 
gradual evolution — things which came from other tilings as 
unlike to them as oaks to acorns or chickens to eggs. And 
this is my justification for tracing back the root-principles of 



THE EOOT-PKINCIPLES OF MIND. 55 

Peeling and of Choice into the vegetable kingdom. If it is 
true that plants manifest so little evidence of Feeling that 
the term can only be applied to them in a metaphorical sense, 
it is also true that the power of Choice which they display is 
of a similarly undeveloped character ; it is limited to a single 
act of discrimination, and therefore no one would think of 
applying the term to such an act, until analysis reveals that 
in such a single act of discrimination we have the germ of 
all volition. 

Let it therefore be understood that the difficulty which 
we are considering arises merely from the gradual manner in 
which the faculties in question arose. The rudimentary 
power of discriminative excitability which a plant displays 
is commensurate with the rudimentary power of selective 
adjustment which it manifests in its movements ; and, just as 
the one is destined by developmental elaboration to become a 
self-conscious subjectivity, so the other is destined, by a 
similar elaboration, to become a deliberative volition. 

I shall now briefly glance at the ascending scale of 
organisms, with the view of showing that this proportional 
relation between the grade of receptive and that of executive 
ability is manifested throughout the series. I desire to make 
it plain that the power of discrimination which in its higher 
manifestations we recognize as Feeling, and the power of 
selective adjustment which in its higher manifestations we 
recognize as Choice, are developed together, and throughout 
their development are commensurate. 

Amoeba is able to distinguish between nutritious and non- 
nutritious particles, and in correspondence with this one act 
of discrimination it is able to perform one act of adjustment ; 
it is able to enclose and to digest the nutritious particles, 
while it rejects the non-nutritious. Some protoplasmic and 
unicellular organisms are able also to distinguish betAveen 
light and darkness, and to adapt their movements to seek the 
one and shun the other ; while in " Animal Intelligence " 
some observations are given which seem to show that the 
discriminative and adjustive powers of these organisms may 
go farther even than this. The insectivorous plants, as we 
have already seen, are able to distinguish, not only between 
nutritious and non-nutritious particles, but also between 
dijfferent kinds of contact ; and, in correspondence with this 
advance in receptive power, w^e observe a commensurate 



56 MENTAL EVOLUTION IN ANIMALS. 

advance in tlie mechanism of adaptive movement. Number- 
less other cases of such simple powers among plants might 
here be noticed ; but none of them rise above the level of 
distinguishing between one or two alternatives of stimula- 
tion, and supplying the correspondingly simple movements 
of response. Where nerve-structure first appears, we find 
that the animals which present it — the Medusse — have organs 
of special sense wherewith to distinguish with comparative 
delicacy and rapidity between light and darkness, and 
probably also between sound and silence. They are also 
provided with an elaborate tentacular apparatus, wherewith 
they ai-e able to distinguish quickly and accurately between 
moving and not moving objects coming upon them from 
various sides, as w^ell as between nutritious and non-nutri- 
tious particles. And in correspondence with this advance of 
receptive capacity we observe a considerable advance of 
executive capacity — the animals being highly locomotive, 
swimming away rapidly from sources of contact which they 
distinguish as dangerous, and manifesting several other reflex 
actions of a similarly adaptive kind. Thus, also, the higher 
organizations of Star-fish, Worms, &c., while serving to supply 
the neuro-muscular mechanisms with still more detailed 
information regarding the outer world, serve likewise to 
supply them with the means of executing a greater variety 
of adaptive movements. In the Mollusca, again, we observe 
another advance in both these respects; the animals feel 
their way with sensitive feelers, select varied kinds of food, 
choose mates of their own species to pair with, and may even 
remember a particular locus as their home, &c. Among the 
Articulata the lower forms present co-ordinated movements 
which are few and simple as compared with the many and 
varied movements of the higher members of the class ; and 
their powers of distinguishing between stimuli are propor- 
tionally small. But in the complicated anatomy of the 
Crabs and Lobsters there is a large provision for the co-ordina- 
tion of movements, and the selective actions are correspond- 
ingly ninnerous and varied ; while among the Insects and 
Spiders the power of muscular co-ordination surpasses that 
of the lower Vertebrata, and the power of intelligent adapta- 
tion, assisted by delicate antennas and highly perfected organs 
of special sense, is also greater. And the same principles 
hold throughout the Vertebrated series. It has already been 



THE ROOT-PEINCIPLES OF MIND. 57 

remarked by Mr. Spencer that there is here a general corre- 
spondence to be observed between the possession of organs 
capable of varied actions, and the degree of intelligence to 
which the animal attains. Thus of Birds the Parrots are the 
most intelligent, and they, more than any other members of 
their class, are able to use their feet, beaks, and tongues in the 
examination of objects. Similarly, the wonderful intelligence 
of the Elephant may be safely considered as correlated with 
the no less wonderful instrument of co-ordinated movement 
which he possesses in his trunk ; while the superior intelli- 
gence of the Monkey, and the supreme intelligence of Man 
may no less safely be considered as correlated with the still 
more wonderful instrument of co-ordinated movement which 
has attained to almost ideal perfection in the human hand. 
Again, and more generally, we may say that throughout the 
animal kingdom the powers of sight and of hearing stand in 
direct ratio to the powers of locomotion ; and the latter are 
conducive to the growth of intelligence.* 

We may now observe that this correlation between 
muscular and mental evolution — or, more generally, between 
power of discrimination and variety of adaptive movements 
— is only what we should expect to find a priori. For it is 
clear that the development of the one function could be of no 
use without that of the other. On the one hand, it would be 
of no use to an organism that it should be able to discern a 
stimulus as hurtful or beneficial, if at the same time it lacked 
the power of co-ordinated movement necessary to adapting 
itself to the result of its discernment ; and, on the other 
hand, it would be equally useless that an organism should 
possess the needful power of co-ordinated movement, if at 
the same time it lacked the power of discernment which 
alone could render the power of co-ordinated movement use- 
ful. Now we know that all the mechanisms of muscular 
co-ordination are correlated with mechanisms of nervous co- 
ordination, and, indeed, that the former without the latter 
would be utterly useless. Yet we know next to nothing of 

* The Dog and Cat seem at first sight to constitute an exception to the 
principle above set forth ; but it must be remembered that both these 
animals, and all their tribe, possess very efficient instruments of touch and 
movements in their tongues, hps, and jaws, as well as to some extent in the 
paws. I think the superior intelligence of the Octopus, among moUusks, is 
to be attributed to the exceptional advantages which are rendered by its large 
and flexible, sensitive and powerful arms. 



58 MENTAL EVOLUTION IN ANIMALS. 

the ultimate nervous mechanisms which play down upon the 
muscular mechanisms; we only see a mazy mexus of cells 
and fibres, the very function of which, much less their inti- 
mate mechanism, could not be guessed, were it not that we 
have the grosser mechanisms of the muscular system whereby 
to study the effects of these finer mechanisms. 

Muscular co-ordinations, then, are so many indices, " writ 
large," of corresponding co-ordinations taking place in the 
nervous system. Now we have seen that mental processes 
may be regarded as indices in precisely the same way, and 
indeed that, like muscular movements, they are the only 
indices we have of the operations of the nervous mechanisms 
with which they are connected. Moreover, we have seen 
that when this new set of indices has reached a certain level 
of development, marking of course a corresponding level 
of development in the nervous system, it begins unmistake- 
ably to show that the functions of receptive discrimination 
and of adaptive movement are taking yet another point of 
departure in the upward course of their development — that 
the nervous system is beginning to discriminate between 
novel and enormously complex stimuli, having reference not 
only to immediate results, but also to remote contingencies ; 
we see in short that the nervous mechanism is beginning to 
develope those higher functions of discriminative and adaptive 
ability which on their subjective side we know as rational. 

Therefore it is clear that these two faculties not only do 
but must proceed together. Every advance in the power of 
discrimination will be followed, in the life of the individual 
and in that of the species, by efforts towards the movements 
of needful adaptation, and in all cases where such movements 
require an advance on the previous power of co-ordination, 
such advance will be favoured by natural selection. Thus 
every advance in the power of discrimination favours an 
advance of the power of co-ordination. And, conversely, we 
may now remark that every advance in the power of co- 
ordination favours an advance of the power of discrimina- 
tion. For, as a greater power of co-ordinated movement 
implies the bringing of nerve-centres into new and more 
varied relations with the outer world, there is thus afforded 
to the nerve-centres a proportionately increased opportunity 
of discrimination — an opportunity which will sooner or later 
be sure to be utilized by natural selection. 



THE EOOT-PKINCIPLES OF MIND. 69 

Thus the two faculties are, as it were, necessarily hound 
together. But here another consideration arises. They are 
thus bound together only up to the point at which the adap- 
tive movements are dependent upon the machinery supplied 
by nature to the organism itself. As soon as the power of 
discrimination has advanced far enough to be, not only con- 
sciously precipient, but deliberatively rational, a wholly new 
state of things is ina^^gurated. For now the organism is no 
longer dependent for its adjustments upon the immediate 
results of its own co-ordinated movements. From the time 
that a stone was first used by a monkey to crack a nut, by a 
bird to break a shell, or even by a spider to balance its web, 
the necessary connexion between the advance of mental dis- 
crimination and muscular co-ordination was severed. With 
the use of tools there was given to Mind the means of pro- 
gressing independently of further progress in muscular co- 
ordination. And so marvellously has the highest animal 
availed itself of such means, that now, among the civilized 
races of mankind, more than a million per cent, of his adjus- 
tive movements are performed by mechanisms of his own 
construction. Wonderful as are the muscular co-ordinations 
of a tight-rope dancer, they are nothing in point of utility as 
compared with the co-ordinated movements of a spinning- 
jenny. Therefore, although man owes a countless debt of 
gratitude to the long line of his brutal ancestry for bequeath- 
ing to him so surpassingly exquisite a mechanism as that of 
the human body — a mechanism without which it would be 
impossible for him, with any powers of mind, to construct 
the artificial mechanisms which he does — still man may justly 
feel that his charter of superiority over the lower animals is 
before all else secured by this, that his powers of adjustive 
movement have been emancipated from their necessary 
alliance with his powers of muscular co-ordination. 

I say, from his powers of muscular co-ordination, because 
it is evident that our powers of adjustive movement, and so 
of adaptation in general, have never been, and can never he, 
emancipated from a necessary alliance with our powers of 
nervous co-ordination. 

I shall now sum up the results of our enquiry so far 
as it has hitherto gone. First, we found the Criterion of 
Mind, ejectively considered, to consist in the exhibition of 



60 MENTAL EVOLUTION IN ANIMALS. 

Choice, and the evidence of Choice we found to consist in the 
performance of adaptive action suited to meet circumstances 
which have not been of such frequent or invariable occur- 
rence in the life-history of the race, as to have been specially 
and antecedently provided for in the individual by the in- 
herited structure of its nervous system. The power of learn- 
ing by individual experience is therefore the criterion of 
Mind. But it is not an absolute or infallible criterion ; all 
that can be said for it is that it is the best criterion available, 
and that it serves to fix the upper limit of non-mental action 
more precisely than it does the lower limit of mental ; for it 
is probable that the power of feeling is prior to that of con- 
sciously learning. 

Having thus arrived at the best available criterion of 
Mind considered as an eject, we next proceeded to consider 
the objective conditions under which known Mind is invari- 
ably found to occur. This led us briefly to inspect the 
structure and functions of the nervous system, and, while 
treating of the physiology of reflex action, we found that 
everywhere the nervous machinery is so arranged that there 
is no alternative of action presented to the nerve-centres 
other than that of co-ordinating the group of muscles over 
the combined contractions of which they severally preside. 
The question therefore arose — How are we to explain the fact 
that the anatomical plan of a nerve-centre with its attached 
nerves comes to be that which is needed thus to direct the 
nervous stimuli into the channels required ? The answer to 
this question we found to consist in the property which is 
shown by nervous tissue to grow by use into the directions 
which are required for further use. This subject is as yet 
an obscure one — especially where the earliest stages of such 
adaptive growth are concerned — but in a general way we can 
imderstand that hereditary usage, combined with natural selec- 
tion, may have been alone sufficient to construct the number- 
less reflex mechanisms which occur in the animal kingdom. 

Passing from reflex action to cerebral action, we first 
noticed that as the cerebral hemispheres pretty closely re- 
semble in their intimate structure ganglia in general, there 
can be no reasonable doubt that the mode of their operation 
is substantially the same. Moreover we noted that, as such 
operation is here unquestionably attended with mental action, 
a strong presumption arises that the one ought to constitute 



THE EOOT-PEINCIPLES OF MIND. 61 

a kind of obverse reflection of the other. Turning, therefore, 
to contemplate this presumably obverse reflection, we found 
that in many respects it is most strikingly true that the 
fundamental principles of mental operation correspond with 
the fundamental principles of ganglionic operation. Thus, we 
found that such is the case with memory and the association 
of ideas both of which we found to have their objective 
counterparts in the powers of non-mental acquisition which 
are presented by the lower ganglia. For we found that these 
ganglia unconsciously learn such exercises as they are made 
frequently to perform, that they forget their exercises if too 
long an interval is allowed to elapse between the times of 
practising them, but that even when apparently quite for- 
gotten such exercises are more easily re-acquired than 
originally they were acquired. More particularly we found 
that the association of ideas by contiguity presents a remark- 
ably detailed resemblance to the association of muscular 
movements by contiguity. For, agreeing to take ideas as the 
objective analogues of muscular movements, we observed when, 
we thus changed the index of nervous operation from muscles 
to ideas, that the strongest evidence was yielded of the method 
of nervous evolution being everywhere uniform. Thus we 
remarked that sensations, perceptions, ideas, and emotions all 
more or less resemble muscular co-ordinations in that they 
are usually blended states of consciousness, wherein each con- 
stituent part must correspond with the activity of some 
particular nervous element — a variety of such elements being 
therefore concerned in the composite state of consciousness, 
just as a variety of such elements are concerned in a com- 
bined movement of muscles. Further, just as the associa- 
tion of ideas is not restricted to a blending of simultaneous 
ideas into one composite idea, but extends to a linking of one 
idea with another in serial succession ; so we saw that mus- 
cular movements exhibit a precisely analogous tendency to 
recur in the same serial order as that in which they have 
previously occurred. Lastly, we noted that all the patholo- 
gical derangements which arise in the nerve-centres that 
preside over muscular activities, have their parallels in simi- 
lar derangements which arise in the nerve-centres that are 
concerned in mental activities. 

Having thus dealt with the Physical Basis of Mind, we 
passed on in the next chapter to consider the Eoot-principles 



62 MENTAL EVOLUTION IN ANIMALS. 

of Mind. Here the object was to trace the ultimate principles 
of physiology that might be taken as constituting the objec- 
tive side of those phenomena which on their subjective and 
ejective sides we regard as mental. These principles we 
found . to be the power of discriminating between different 
kinds of stimuli irrespective of their relative degrees of 
mechanical intensity, coupled with the power of performing 
adaptive movements suited to the results of such discrimina- 
tion. These two powers, or faculties, we saw to occur in 
germ even among the protoplasmic and unicellular organisms, 
and we saw that from them upwards all organization may be 
said to consist in supplying the structures necessary to an 
ever-increasing development of both these faculties, which 
always advance, and must necessarily advance, together. 
When their elaboration has proceeded to a certain extent, 
they begin gradually to become associated with Feeling, and 
when they are fully so associated, the terms Choice and Pur- 
pose become to them respectively appropriate. Continuing 
in their upward course of evolution, they next become con- 
sciously deliberative, and eventually rational. But although 
when viewed from the subjective or ejective side they thus 
appear, during the upward course of their development, to 
become transformed from one entity to another, such is not 
the case when they are viewed from their objective side. 
For, when viewed from their objective side, the most elaborate 
process of reasoning, or the most comprehensive of judg- 
ments, is seen to be nothing more than a case of exceedingly 
refined discrimination, by highly-wrought nervous structures, 
between stimuli of an enormously complex character ; while 
the most far-siglited of actions, adapted to meet the most 
remote contingencies of stinmlation, is nothing more than a 
neuro-muscular adjustment to the circumstances presented by 
the environment. 

Thus, if we again take mental operations as indices 
whereby to study the more refined working of nervous centres, 
as we take muscular movements to be so many indices, 
" writ large," of the less refined working of such centres, 
we again find forced upon us the truth that the method of 
nervous evolution has everywhere been uniform ; it has 
everywhere consisted in a progressive development of the 
power of discriminating between stimuli, combined with the 
complementary power of adaptive response. 



EXPLANATION OF THE DIAGEAM. 63 



CHAPTER V. 

Explanation of the Diageam. 

We have now sufficiently considered the sundry first prin- 
ciples and preliminary questions which lie at the threshold of 
our subject proper. It seemed to me desirable to dispose of 
these principles and questions before we enter upon our 
attempt at tracing the probable history of Mental Evolution. 
But now that these first principles and preliminary questions 
have been disposed of, so far as their nature renders possible, 
the way is as clear as it can be for us to pursue our enquiry 
concerning the Genesis of Mind. In order to give definition 
to the somewhat laborious investigation on which we are thus 
about^to embark, I have thought it a good plan to draw a 
diagram or map of the probable development of Mind from 
its first beginnings in protoplasmic life up to its culmination 
in the brain of civilized man. The diagram embodies the 
results of my analysis throughoiit, and will therefore be 
repeatedly alluded to in the course of that analysis — i.e., 
throughout the present and also my future work. I may 
therefore begin by explaining the plan of this diagram. 

The diagram, as I have just said, is intended to represent 
in one view the whole course of mental evolution, supposing, 
in accordance with our original hypothesis, such evolution to 
have taken place. Being a condensed epitome of the results 
of my analysis, it is in all its parts carefully drawn to a 
scale, the ascending grades or levels of which are everywhere 
determined by the evidence which I shall have to adduce. 
The diagram is therefore not so much the product of my indi- 
vidual imagination, as it is a summary of all the facts which 
science has been able so far to furnish upon the subject ; and 
although it is no doubt true that the progress of science may 
affect the diagram to the extent of altering some of its details, 
I feel confident that the general structure of our knowledge 
concerning the evolution of mind is now sufficiently coherent 



64 MENTAL EVOLUTION IN ANIMALS. 

to render it highly improbable that this diagrammatic repre- 
sentation of it will, in the future, be altered in any of its 
main features by any advances that science may be destined 
to make. 

Erom the groundwork of Excitability, or the distinguish- 
ing peculiarity of living matter, I represent the structure of 
mind as arising by a double root — Conductility and Discrimi- 
nation. To what has already been said on these topics it is 
needless to add more. We have seen that the distinguishing 
property of nerve-fibre is that of transmitting stimuli by a 
propagation of molecular disturbance irrespective of the pas- 
sage of a contraction wave-* and this property, laying as it 
does the basis for all subsequent co-ordination of protoplasmic 
(muscular) movements, as well as of the physical aspect of 
all mental operations, deserves to be marked off in our map 
as a distinct and important principle of development ; it is 
the principle which renders possible the executive faculty of 
appropriately responding to stimuli. Not less deserving of 
similar treatment is the cognate principle of Discrimination, 
which, as we have seen, is destined to become the most 
important of the functions subsequently distinctive of nerve- 
cells and ganglia. But we have also seen that both Conduc- 
tility and Discrimination first appear as manifested by the 
cellular tissues of plants, if not even in some forms of 
apparently undifferentiated protoplasm. It is, however, only 
when these two principles are united within the limits of the 
same structural elements that we first obtain optical evidence 
of that differentiation of tissue which the histologist recognizes 
as nervous ; therefore I have represented the function of 
nerve-tissue in its widest sense, Neurility, as formed by a 
confluence of these two root-principles. Neurility then 
passes into Keflex Action and Volition, which I have repre- 
sented as occupying the axis or stem of the psychological 
tree. On each side of this tree I have represented the out- 
growth of branches, and for the sake of distinctness I have 
confined the branches which stand for the faculties of Intellect 
on one side, while placing those which represent the Emotions 
upon the other. The level to which any branch attains re- 
presents the degree of elaboration which the faculty named 
thereon presents ; so that, for instance, when the branch 
Sensation, taking origin from Neurility, proceeds to a certain 
level of development, it gives off the commencement of Per- 



EXPLANATION OF THE DIAGRAIL C5 

ception, and then continues in its own line of development to 
a somewhat higher level. Similarly, Imagination arises out 
of Perception, and so with all the other branches. Thus, the 
fifty levels which are drawn across the diagram are intended 
to represent degrees of elaboration ; they are not intended to 
represent intervals of time. Such being the case, the various 
products of mental evolution are placed in parallel columns 
upon these various levels, so as to exhibit the comparative 
degrees of elaboration, or evolution, which they severally 
present. One of these columns is devoted to the psycho- 
logical scale of intellectual faculties, and another to the 
psychological scale of the emotional. But for the danger of 
rendering the diagram confused, these faculties might have 
been represented as secondary bra,nches of the psychological 
tree ; in a model this might well be done, but in a diagram it 
would not be practicable, and therefore I have restricted the 
branching structure to represent only the most generic or 
fundamental of the psychological faculties, and relegated those 
of more specific or secondary value to the parallel columns on 
either side of the branching structure. In these two columns 
I have throughout written the name of the faculty at 
what I conceive to be the earliest stage, or lowest level of its 
elaboration ; i.e., where it first gives evidence of its existence. 
In another parallel column I have given the grades of mental 
evolution which I take to be characteristic of sundry groups 
in the animal kingdom, and in yet another column I have 
represented the grades of mental evolution which I take to 
be characteristic of different a^es in the life of an infant. 

In my subsequent work I shall fill up all the levels in 
these vertical columns which are now left blank, on account 
of the text of the present work being restricted to the mental 
evolution of animals. At first I intended in this work to 
truncate the whole diagram at the level where mental evolu- 
tion in animals ends — i.e., at the level marked 28 — and to 
reserve the continuation of the stem and branches, as well as 
that of the parallel columns, for my ensuing work. But 
afterwards I thought it was better to supply the continuation 
of the stem and branches, in order to show the proportion 
which I conceive to obtain between the elaboration of the 
higher faculties as they occur in animals and the same 
faculties as they occur in man. 

Confining, then, our attention to the first twenty-eight 



66 MENTAL EVOLUTION IN ANIMALS. 

levels with which alone the present essay is to be concerned, if 
we pitch upon any one of them at random, we shall obtain a 
certain rough estimate of the grade of mental evolution which 
is presented by the animals named upon that level. 

To avoid misapprehension I may add that in thus render- 
ing a diagrammatic representation of the probable course of 
mental evolution with the comparisons of psychological 
development exhibited in the parallel columns, I do not 
suppose that the representation is more than a rough or 
general outhne of the facts ; and, indeed, I have only 
resorted to the expedient of thus representing the latter for 
the sake of convenience in my subsequent discussion. Eough 
as this outline of historical psychology may be, it will serve 
its purpose if it tends to facilitate the exposition of evidence, 
and afterwards serves as a dictionary of reference to the more 
important of the facts wliich I hope this evidence will be able 
to substantiate. 

Such being the general use to which I intend to put the 
diagram, I may here most fitly make this general remark in 
regard to it. In the case alike of the stem, branches, and the 
two parallel coUmms on either side — i.e., all the parts of the 
diagram which serve to denote psychological faculties — we 
must remember that they are diagrammatic rather than truly 
representative. For in nature it is as a matter of fact impos- 
sible to determine any hard and fast lines between the com- 
pleted development of one faculty and the first origin of the 
next succeeding faculty. The passage from one faculty to 
another is throughout of that gradual kind which is charac- 
teristic of evolution in general, and which, while never pre- 
venting an eventual distinction of species, always renders it 
impossible to draw a line and say — Here species A ends and 
species B begins. Moreover, I cannot too emphatically im- 
press my conviction that any psychological classification of 
faculties, however serviceable it may be for purposes of 
analysis and discussion, must necessarily be artificial. It 
would, in my opinion, be a most erroneous view to take of 
Mind to regard it as really made up of a certain number of 
distinct faculties — as erroneous, for example, as it would be 
to regard the body as made up of the faculties of nutrition, 
excita'oility, generation, and so on. All such distinctions are 
useful only for the purposes of analysis ; they are abstractions 
of our own making for our own convenience, and not 



EXPLANATION OF THE DIAGEAIL 67 

naturally distinct parts of tlie structure which we are 
examining. 

But although it is desirable to keep these caveats in our 
memory, I do not think that either the artificial nature of 
psychological classification or the fact that we have to do 
with a gradual process of evolution, constitutes any serious 
vitiation of the mode of representation which I have adopted. 
For, on the one hand, some classification of faculties we must 
have for the purposes of our inquiry ; and, on the other hand, 
I have as much as possible allowed for the unavoidable defect 
in the representation which arises from evolution being 
gradual, by making the branches of the arborescent structure 
wide at their bases, and by allowing each of them, after giving 
off the next succeeding branch, to continue on its own course of 
development ; so that both the parent and daughter faculty- 
are represented as occupying for a more or less considerable 
distance the same levels of development — in each case my 
estimate of the comparative elaboration which the completed 
faculty betokens being represented by the vertical height of 
its apex. Besides, as already stated, faculties named in the 
two parallel columns are written upon those levels where I 
have either a priori reasons or actual evidence to conclude 
that they first definitely appear in the growing structure of 
Miud ; in this way the difficult question of assigning the 
lower limit of evolution at which any particular faculty 
begins to dawn is as much as possible avoided. 

It is almost needless to add that in preparing this diagram 
I have resorted to speculation in as small a measure as the 
nature of the subject permits. Nevertheless it is obvious 
that the nature of the subject is such that, in order to com- 
plete the diagram in some of its parts, I have been obliged to 
resort to speculation pretty largely. I think, however, that 
as the exposition proceeds, it will be seen that, if the funda- 
mental hypothesis of mental evolution having taken place is 
granted, my reasoning as to the probable history of the pro- 
cess does not anywhere involve speculation of an extravagant 
or dangerous kind. In matters of detail — such, for instance, 
as the comparative elevation of the different branches in the 
psychological tree — my estimates may, probably enough, be 
more or less erroneous ; but the main facts as to the sequence 
of the faculties in the order of their comparative degrees of 
elaboration are mere corollaries from our fundamental hypo- 



68 MENTAL EVOLUTION IN ANIMALS. 

thesis ; and, as we shall see, these facts, as I have presented 
them, are sustained or corroborated by many others drawn 
from observations on the psychology of animals and children. 
Again, in the columns devoted to the emotions and faculties 
of intellect, the results of actual observation predominate over 
those yielded by speculation ; while in the remaining columns 
the results tabulated are for the most part due to observa- 
tion. 

Therefore I submit that if the hypothesis of mental 
evolution be granted, and if all the matters of observable 
fact which the diagram serves to express are eliminated, com- 
paratively little in the way of deductive reasoning is left ; 
and of this little most follows as necessary consequence from 
the original hypothesis of mental evolution having taken 
place. Of course any one who does not already accept the 
theory of evolution in its entirety, may object that I am 
thus escaping from the charge of speculation only by assum- 
ing the truth of that which grants me all that I require. To 
this I answer that as far as the evidence of Mental Evolution, 
considered as a fact, is open to the charge of being specula- 
tive, I must leave the objector to lodge hk objection against 
Mr. Darwin's " Origin of Species " and " Descent of Man." I 
shall be abundantly satisfied with my own work if, taking 
the process of Mental Evolution as conceded, I can make it 
clear that the main outlines of its history may be determined 
without any considerable amount of speculation, as dis- 
tinguished from deduction following by way of necessary 
consequence from the original hypothesis. 

Having thus explained the plan and principles of the 
diagram, I shall now consider the levels from the lowest as 
far as the rise of the first branch, i.e., from 1 to 14. After 
what has already been said in the foregoing chapters on the 
Physical Basis and Eoot-principles of Mind, our consideration 
of this part of the diagram need not detain us long. 

Levels 1 to 4 are occupied by Excitability, Protoplasmic 
Movements, Protoplasmic Organisms, and the generative 
elements which have not yet united to start the Embryo of 
Man. From 4 to 9 we have the levels filled by the rise and 
progress of the functions Conductility and Discrimination, 
which by their subsequent union at 9 lay the basis of 
Neurility, or the stem of Mind ; in these levels occur the 



EXPLANATION OF THE DIAGKAM. 69 

Non-nervous Adjustments, Unicellular Organisms, ana part of 
the Life-history of the Embryo. Between 9 and 14 is repre- 
sented the development of Neurility and its passage into 
Eeflex Action ; the parallel columns within this space are 
therefore respectively filled with Partly-nervous Adjustments 
and the beginning of True Nervous Adjustments, Unknown 
Animals, probably Ccelenterata, perhaps extinct, and another 
portion of the Life-history of the Embryo. I here speak of 
" unknown animals " because, so far as investigation has 
hitherto gone, the animals in which nerve-tissue first began 
to be differentiated have not yet been found. In the lowest 
animals where this tissue has been found — the Medusae — it 
appears as already well differentiated. The ganglion cells, 
however, show in a most unmistakeable manner their parent- 
age from epithelium — their structure, in fact, often resembling 
that of modified epithelium more than that of true nerve- 
cells.* In these structures, therefore (as in the analogous 
histological elements met with in the embryonic nerve-tissue 
of higher animals), we have a link which connects true nerve- 
tissue with its cellular ancestry, and thus it is comparatively 
immaterial whether or not the animals which presented the 
earlier stages of this histological transition are still in exist- 
ence. Thus we need not wait to discuss Kleinenberg's view 
on the " neuro-muscular " cells of Hydra. 

* See Prof. E. A. Seliiifcr on Nervous System of Aurelia Auriia, Phil. 
Trans., 1878, and Profs. O. and H. Hei'Lwig on Das Nerceiisi/ntem und die 
Sinnesorgane der Meduseii. 



70 MENTAL EVOLUTION IN ANILIALS. 



CHAPTEE VI. 

Consciousness. 

Hitherto in this work I have been considering, as exclu- 
sively as the nature of the subject permits, the physical or 
objective aspect of mental processes, and of the antecedents 
of these processes in the non-mental activities of living 
organisms. It now devolves upon us to turn to the sub- 
jective side of the matter, and still more closely, I may 
observe, to the ejective side of it. That is to say, from this 
point onward my endeavour will be to trace the probable 
course of Mental Evolution by having regard to truly mental 
phenomena, so far as these admit of analysis by subjective 
or ejective methods. I desire, therefore, to draw prominent 
attention to the fact that from this point in my treatise I 
take, as it were, a new departure ; for if this is not kept in 
mind, my exposition may appear to resemble two separate 
essays bound together rather than one continuous whole. In 
my endeavour to draw a sharp line of demarcation between 
the physiology and the psychology of my subject, I have^ 
found it impossible to discuss the one without numerous 
allusions to the other — the consequence being that hitherto, 
while treating as exclusively as I could of the physiology of 
vital processes, I have been obliged frequently to refer to the 
psychology of mental processes, a knowledge concerning the 
main facts of which I have taken for granted on the part of 
any one who is likely to read this book. Thus it happens 
that in now turning to investigate the psychology of these 
proce,jSes, it is impossible to avoid a certain amount of over- 
lapping witli what has gone before. For example, in my 
chapter on the Physical Basis of Mind, it was clearly impos- 
sible not to allude to such leading principles of psychology 
as sensation, perception, ideation, and others. Therefore, in 
now undertaking an investigation of these various principles 



CONSCIOUSNESS. 71 

in the order of tlieir probable evolution, it may often appear 
that I am, as it were, going back upon, or in part repeating, 
what I have already said. But this apparent defect in the 
method of my exposition will, I think, be seen on closer 
attention to be more than compensated for by the advantage 
of avoiding confusion between physiology and psychology. 
It would, for instance, have been easy to have split up the 
chapter on the Physical Basis of Mind already alluded to, 
and to have apportioned its various parts to those among the 
succeeding chapters which treat of the psychological aspects 
of the physiological principles set forth in those various 
parts; but the result would have been largely to have 
obscured the doctrine which I desired to make plain through- 
out — viz., that all mental processes must be regarded as pre- 
senting physical counterparts.* 

So much in explanation of my method being understood, 
I shall begin the psychology of mental evolution by con- 
sidering that in which the mind-element must be regarded as 
consisting — namely. Consciousness. Turning to the diagram, 
it will be observed that I have written the word " Con- 
sciousness " in a perpendicular direction, beginning at level 14 
and extending to level 19. My reason for doing this is 
because the rise of Consciousness is probably so gradual, and 
certainly so undefined to observation, that any attempt to 
draw the line at which it does arise would be impossible, 
even on the rough and general scale wherewith I have endea- 
voured to draw the lines at which the sundry mental faculties 
may be regarded as taking origin. Therefore I have repre- 
sented the rise of Consciousness as occupying a considerable 
area in our representative map, instead of a definite line. 
This area I make to begin with the first development of 
" Nervous Adjustments," and to terminate with the earliest 
appearance of the power of associating ideas. 

In now proceeding to justify this assignment of limits 
between the earliest dawn of Consciousness and the place 
where Consciousness may first be regarded as truly such, I 
may best begin by saying that I shall not attempt to define 

* It seems almost needless to add that tlie impossibility of entirely sepa- 
rating psychology from physiology for the purposes of exposition will, mutatis 
mutandis, continue to meet us more or less throughout the following, as it 
has throughout the preceding chapters ; but I shall endeavour always to 
make it clear when I am speaking of mental processes and when of physical. 



72 MENTAL EVOLUTION IN ANIMALS 

■what is meant by Consciousness. For, like the word " Mind," 
" Consciousness " is a term which serves to convey a meaning 
well and generally understood, but a meaning which, from 
the peculiar nature of the case, cannot be comprehended in 
any definition. If we say that a man or an animal is con- 
scious, we mean that the man or animal displays the power of 
Feeling, and if we ask what we mean by Feeling, we can only, 
I think, answer — that which distinguishes Non-extended 
Existence from Extended. Deeper than this we cannot go, 
because Consciousness, being itself the basis of all thought, 
and so of all definition, cannot be itself defined except as the 
antithesis of its logical correlative — No-consciousness. 

Let us first regard the phenomena of Consciousness as 
disclosed in our own or subjective experience. We shall 
subsequently see that the elementary or undecomposable 
units of consciousness are what we call sensations. If we 
interrogate experience we find that an elementary state of 
consciousness, or sensation, may exist in any degree, from 
that of an almost unrecognizable affection, up to that of 
unendurable pain, which monopolizes the entire field of con- 
sciousness. More than this, from the lowest limit of per- 
ceptible sensation there arises a long and indefinite descent 
through sensation that is not perceptible, or through sensation 
that is sub-conscious, before we arrive at nervous action 
which we feel entitled to regard as unconscious. This is 
proved by those grades of almost unconscious action, passing 
at last into wholly unconscious action, which we all know as 
frequently occurring in the descent, through repetition or 
habit, of consciously intelligent adjustments to automatic 
adjustments, or adjustments performed unconsciously. Thus 
it is evident, not only that consciousness admits of numberless 
degrees of intensity, but that in its lower degrees its ascent 
from no-consciousness is so gradual, that even within the 
range of our own subjective experience we find it impossible 
to determine within wide limits where consciousness first 
emerges.* 

With this gradual dawn of consciousness as revealed to 
subjective analysis, we should expect some facts of physiology, 
or of objective analysis, to correspond ; and this we do find. 

* Any one who has gradually fainted, or has slowly been put under the 
influence of an aniesthetic, will remember the peculiar experience of feeling 
consciousness becoming obliterated by stages 



CONSCIOUSNESS, 73 

Tor in our own organisms we know tliat reflex actions are 
not accompanied by consciousness, although the complexity 
of the neuro-muscular systems concerned in these actions 
may be very considerable. Clearly, therefore, it is not mere 
complexity of ganglionic action that determines conscious- 
ness. What, then, is the difference between the mode of 
operation of the cerebral hemispheres and that of the lower 
ganglia, which may be taken to correspond with the great 
subjective distinction between the consciousness which may 
attend the former and the no-consciousness which is inva- 
riably characteristic of the latter ? I think the only difference 
that can be pointed to is a difference of rate or time. We 
know by actual measurement, as we shall subsequently see 
in more detail, that the cerebral hemispheres work more 
slowly while undergoing those changes which are accom- 
panied by consciousness than is the case with the activities 
of the lower centres. In other words, the period between the 
fall of a stimulus and the occurrence of responsive movement 
is notably longer if the stimulus has first to be perceived, than 
it is if no perception is required. And this is proved, not 
only by comparing the latent period (or the time which 
elapses between the stimulation and the response) in the case 
of an action involving one of the lower centres and that of an 
action involving the cerebral hemispheres in perception ; but 
also by comparing the latent period in the case of one and 
the same cerebral action which from having originally involved 
perception has through repetition become automatic. An old 
sportsman will have his gun to the shoulder, by an almost 
unconscious act, the moment that a bird unexpectedly rises ; 
a novice similarly surprised will spend a valuable second in 
"taking in" the situation. And any number of similar facts 
might be given to show that if few things are " as quick as 
thought," reflex or automatic action is one that is quicker. 
Further, in a general way it can be shown that the more 
elaborate a state of consciousness is, the more time is required 
for its elaboration, as we shall see more in detail when we 
come to treat of Perception. 

Now what does this greater consumption of time imply ? 
It clearly implies that the nervous mechanism concerned 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 



74 MENTAL EVOLUTION IN ANIMALS. 

response (liowever complex tliis 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 Jife 
this play of stimuli in the presence of "difficult circum- 
stances " is known as indecision ; but even in a simple act of 
consciousness — such as that of 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 the cells and fibres of the cerebral hemispheres. 
And this complex play of forces, which finds its physiological 
expression in a lengthening of the time of latency, finds also 
a psychological expression in the rise of consciousness. 

The function, then, of the cerebral hemispheres is that of 
dealing with stimuli which, although possibly and in a com- 
parative sense simple, are yet so varied in character that 
special reflex mechanisms have not been set aside to deal 
with them in one particular way ; and it is the consequent 
perturbation of these highest nerve-centres in dealing with 
such stimuli that is accompanied by the phenomena of con- 
sciousness. Or, in the words of Mr. Spencer, " there cannot 
be co-ordination of many stimuli without some ganglion 
through which they are all brought into relation. In the pro- 
cess of bringing them into relation, this ganghon must be 
subject to the influence of each — must undergo many changes. 
And the quick succession of changes in a ganglion, implying 
as it does perpetual experiences of differences and likenesses, 
constitutes the raw material of consciousness."* 

Thus we see, so far as we can ever perhaps hope to see, 
how conscious action gradually arises out of reflex. As the 
stimuli to be dealt with become more complex and varied 
(owing to the advancing evolution of organisms bringing 

* Principles of Psychologi/, vol. i, p. 435. I thint, however, that Mr. 
Spencer is not sufficiently explicit, either in the above quoted passage or else- 
where, in showing that " the raw material of consciousness " is not necessarily 
constituted by the mere complexity of ganglionic action. Indeed, as I have 
said, such complexity in itself does not appear to bave anything to do with the 
rise of consciousness, except in so far as it may be conducive to what we may 
term tlie ganglionic friction, which is expressed by delay of response. 



CONSCIOUSNESS. 75 

tliem into more and more complex and varied relations with 
their environment), the primitive assignment of a special 
nervous mechanism to meet the exigencies of this or that 
special group of stimuli becomes no longer practicable, and 
the higher nerve-centres have therefore to take on the func- 
tion of focussing many and more or less varied stimuli, in 
order to attain to that higher aptitude of discrimination in 
which we have already seen to consist the distinctive attri- 
bute of Mind. And, as Mr. Spencer has observed, " the co- 
ordination of many stimuli into one stimulus is, so far as it 
goes, a reduction of diffused simultaneous changes into con- 
centrated serial changes. Whether the combined nervous 
acts which take place when the fly-catcher seizes an insect 
are regarded as a series passing through its centre of co- 
ordination in rapid succession, or as consolidated into two 
successive states of its centre of co-ordination, it is equally 
clear that the changes going on in its centre of co-ordination 
have a much more decided linear arrangement than have the 
changes going on in the scattered ganglia of a centipede." 
And this linear character of the change is, of course, one of 
the most distinctive features of consciousness as known to 
ourselves subjectively. 

It will have been observed that this interpretation of the 
rise of consciousness is purely empirical. We know by 
immediate or subjective analysis that consciousness only 
occurs when a nerve-centre is engaged in such a focussing 
of varied or comparatively unusual stimuli as have been 
described, and when as a preliminary to this focussing or act 
of discriminative adjustment there arises in the nerve-centre 
a comparative turmoil of stimuli coursing in more or less 
unaccustomed directions, and therefore giving rise to a com- 
parative delay in the occurrence of the eventual response. 
But we are totally in the dark as to the causal connection, if 
any, between such a state of turmoil in a ganglion and the 
occurrence of consciousness. Whether it is the Angel that 
descends to trouble the waters, or the troubling of the waters 
that calls down the Angel, is really the question which divides 
the Spiritualists from the Materialists ; but with this question 
we have nothing to do. It is enough for aU the objects of 
the present work that we never get the Angel without the 
troubling, nor the troubling without the Angel ; we have an 
empirical association between the two which is as valid for 



76 ItlENTAL EVOLUTION IN ANIMALS. 

tlie purposes of merely historical psychology as would be a 
full understanding of the causal connection, if there is any 
such connection to be understood. 

So much, then, for the physical conditions under which 
consciousness is always and only found to occur. It remains 
briefly to conclude this chapter by showing that these con- 
ditions may most reasonably be regarded as first arising 
within the limits between which I have represented the 
origin of consciousness. 

Eemembering what has already been said concerning the 
gradual or undefined manner in which consciousness probably 
dawned upon the scene of life, and that I therefore represent 
its rise as occupying a wide area on the diagram instead of a 
definite line, I think it least objectionable to place the begin- 
ning of this dawn in nervous adjustments or reflex action, 
and the end of it in the association of ideas. For, on the one 
hand, it is clear from what has been said that it is impossible 
to draw any definite line between reflex and conscious action, 
inasmuch as, considered objectively or as action, the latter 
differs from the former, not in kind, but only in a gradual 
advance in the degree of central co-ordination of stimuli. 
Therefore, where such central co-ordination is first well 
established, as it is in the mechanism of the simplest reflex 
act, there I think we may with least impropriety mark the 
advent of consciousness. On the other hand, where vague 
memory of past experiences first passes into a power of asso- 
ciating simple ideas, or of remembering the connections 
between memories, there I think consciousness may most 
properly be held to have advanced sufiiciently far to admit of 
our regarding it as fairly begun. 

In this scheme, therefore — which of course it is needless 
to say I present as a somewhat arbitrary estimate where no 
more precise estimate is possible — the Ccelenterata are repre- 
sented as having what Mr. Spencer calls " the raw material 
of consciousness," the Echinodermata as having such an 
amount of consciousness as I think we may reasonably sup- 
pose that they possess, if we consider how multifarious and 
complicated their reflex actions have become, and if we 
remember that in their spontaneous movements the neuro- 
muscular adjustments which they exhibit almost present the 
appearance of being due to intelligence.* The Annelida I 

* See riiil. Trans,, Croonian Lecture, 1881. 



CONSCIOUSNESS. 77 

place upon a still higher level of consciousness, because, both 
from the facts mentioned in " Animal Intelligence" and from 
those published by Mr. Darwin,* it seems certain that their 
actions so closely border on the intelligent that it is difficult 
to determine whether or not they should be classed as intel- 
ligent. Upon this level, also, I represent the period of the 
embryonic life of Man as coming to a close ; for although the 
new-born child, from the immaturity of its experience, dis- 
plays no adjustments that can be taken as indicative of 
intelligence, still, as its nerve-centres are so elaborate (embo- 
dying the results of a great mass of hereditary experience, 
which although more latent in the new-born child than in the 
new-born of many other mammals and all birds, must still, 
we should infer from analogy, count of something), that we 
can scarcely doubt the presence of at least as much conscious- 
ness as occurs among the annelids. Moreover, pain appears 
to be felt by a new-born child, inasmuch as it cries if injured ; 
and although this action may be largely or chiefly reflex, we 
may from analogy infer that it is also in part due to feeling. 
The remaining levels occupied by the dawn of consciousness 
may be considered as assigned to the lower MoUusca — an 
assignment which I think will be seen to be justified by con- 
sulting the evidence given in my former work of actions 
performed by these animals of a nature which is unques- 
tionably intelligent, 

• See his work on Earlkworms, 1S81. 



V8 MENTAL EVOLUTION IN ANIMALS. 



CHAPTEE VII. 

Sensation. 

By Sensation I mean simply Feeling aroused by a stimulus. 
In my usage, therefore, the term is of course exclusive of 
all the metaphorical meanings which it presents in such 
applications as " sensitive plates," &c. It is also exclusive, on 
the one hand, of Reflex Action, as well as of non-nervous 
adjustments, and on the other, of Perception, Thus, too, it is 
exclusive of the carefully defined meaning which it bears in 
the writings of Lewes. He defined Sensation as the reaction 
of a sense-organ, whether or not accompanied by Feeling, and 
thus he habitually speaks of unfelt sensations. In his nomen- 
clature; therefore. Sensation is a process of a purely physical 
kind, with which consciousness may or may not be involved. 
In my opinion, however, it is most desirable, notwithstanding 
his elaborate justification of this use of the term, to abide by 
its original signification, which I have explained. When I 
have occasion to speak of the physical reaction of a sense- 
organ, I shall speak of it as a physical reaction, and not as a 
sensation. The distinction which, in common with other 
psychologists, I draw between a Sensation and a Perception, 
I shall explain more fully in the chapter where I shall have 
to treat of Perception. Meanwhile it is enough to say that 
the great distinction consists in Perception involving an 
element of Cognition as well as the element of Feeling. 

It is more difficult to draw the distinction between 
Sensation and non- nervous adjustments, and still more so 
between Sensation and nervous adjustments which are un- 
felt (Pieflex Action). Here, however, we are but again 
encountering the difficulty which we have already con- 
sidered, viz., that of drawing the line where consciousness 
begins ; and, as we have previously seen, this difficulty has 
nothing to do with the validity of a classification of psychical 



SENSATION. 79 

faculties ; it only has to do with the question whether such 
and such a faculty occurs in such and such an organism. 
Therefore, so long as the question is one of classifying 
psychical faculties, we can only say that wherever there is 
Feeling there is Sensation, and wherever there is no Feeling 
there is no Sensation.* But where the question is one of 
classifying organisms with reference to their psychical facul- 
ties, it is clear that the difficulty of determining whether or 
not this and that particular low form of life has the begin- 
nings of Sensation, is one and the same as the question 
whether it has the beginnings of Consciousness. Now we 
have already considered this question, and we have found it 
impossible to answer; we cannot say within broad limits 
where in the animal kingdom consciousness may first be re- 
garded as present. But for the sake of drawing the line 
somewhere with reference to Sensation, I draw it at the place 
in the zoological scale where we first meet with organs of 
special sense, that is to say, at the Coelenterata. In doing 
this, it is needless to observe, I am drawing the line quite 
arbitrarily. On the one hand, for anything that is known to 
the contrary, not only the sensitive plant which responds to 
a mechanical stimulus, but even the protoplasmic organisms 
which respond to a luminous stimulus by congregating in or 
avoiding the light, may, while executing their responses, be 
dimly conscious of feeling ; and, on the other hand, the mere 
presence of an organ of special sense is certainly no evidence 
that its activities are accompanied by Sensation. What we 
call an organ of special sense is an organ adapted to respond 
to a special form of stimulation ; but whether or not the pro- 
cess of response is accompanied by a sensation is quite 
another matter. We infer by a strong analogy that it is so 
accompanied in the case of organisms like our own (whether 
of men or of the higher animals) ; but the validity of such 
inference clearly diminishes with the diminishing strength of 
the analogy — i.e., as we recede in the zoological and psycho- 
logical scales from organisms like our own towards organisms 
less and less like. 

Having thus made it as clear as I can that it is only for 
the matter of convenience that I have supposed the rise of 
Sensation to coincide with the rise of organs of special 

* Although this sounds like a truism, it is in direct opposition to the 
classification of Lewes, alluded to above. 



80 MENTAL EVOLUTION IN ANIMALS. 

sense, I shall next proceed to take a brief survey of the 
animal kingdom with reference to the powers of special 
sense. In doing this, however, it is needless, and indeed 
undesirable, that I should enter with much closeness into the 
anatomy of the innumerable organs of special sensation 
which the animal kingdom presents. My object is merely to 
give a general outline of the powers of special sensation pro- 
bably enjoyed by different classes of animals ; for, as these 
powers constitute the foundation of all the other powers of 
mind, it is of importance for us to have a general idea of the 
grade of their development in the sundry grades of the 
zoological scale. 

In some of his recently published experiments, Engel- 
mann found that many of the protoplasmic and unicellular 
organisms are affected by light ; that is to say, their move- 
ments are influenced by light, in some cases causing accele- 
ration, in others slowing, of their movements ; in some cases 
the organisms seeking the light, while in other cases they 
shun it, &c., &c. He found that all these effects were re- 
ducible to one or other of three causes : (1) alteration pro- 
duced by the light in the interchange of gases, (2) consequent 
alteration in the conditions of respiration, and (3) specific 
processes of luminous stimulation. It is with the latter only 
that we are concerned, and the organism which Engelmann 
names as exhibiting it typically is Englena viridis. After 
precautions had been taken to eliminate causes 1 and 2, it 
was still found that this organism sought the light. More- 
over, it was found that it would only do so if the light were 
allowed to fall upon the anterior part of its body. Here 
there is a pigment-spot, but careful experiment showed that 
this was not the point most sensitive to light, a colourless 
and transparent area of protoplasm lying in front of it being 
found to be so. Hence it is doubtful whether this pigment- 
spot is or is not to be regarded as an exceedingly primitive 
organ of special sense. Of the rays of the spectrum, Englena 
viridis prefers the blue.* 

The remarkable observation recorded by Mr. H. J. Carter, 
r.R.S., and quoted from him in my previous work,t seems to 
display almost incredible powers of special sense among the 

* For f uU account of tliese experiments, see PJliiger^s Archiv.f. d.ges. 
rhifsiologie, Bd. XXIX, 1882. 

t Animal Intelligence, pp. 19-21 , 



SENSATION. 81 

Ehizopoda; and Professor Haeckel observes, in his essay on the 
" Origin and Development of the Sense-Organs," that " already 
among the microscopic Protista there ar(; some that love light, 
and some that love darkness rather than light. Many seem also 
to have smell and taste, for they select their food with great 
care. . . . Here also we are met by the weighty fact that 
sense-function is possible without sense-organs, without nerves. 
In place of these, sensitiveness is resident in that wondrous, 
structureless, albuminous substance which, under the name of 
protoplasm, or organic formative material, is known as the 
general and essential basis of all the phenomena of life." 

Again, Engelmann describes a chase of one infusorium 
by another. The former in its free course happened to cross 
the route of a free-swarming vorticella. There was no con- 
tact, but it immediately gave chase, and for five seconds the 
two darted about with the utmost activity, the chasing infu- 
sorium maintaining a distance of about ^ mm. behind the 
chased one. Then, owing to a sudden sideward dart of the 
vorticella, its pursuer lost the object of pursuit. The powers 
of discrimination shown by certain deep-sea protoplasmic 
organisms in selecting sand-grains of a particular size where- 
with to construct their tests has already been alluded to. 

But passing now to animals in which we first meet with 
nerves, viz., the Medusae, it is among them also that we first 
meet with organs of special sense. I have myseK observed 
that several species of Medusae seek the light, following a 
lantern if this is moved round a bell-jar containing them 
in a dark room. The pigmented bodies round the margin of 
the swimming-disk were proved to be the organs of special 
sense here concerned, and the rays in the spectrum by which 
they are affected were shown to be confined to the luminous 
part. It was further observed that some genera of Medusae 
had more highly developed visual sensation than others. The 
least efficient occurs in Tiaropsis polydiademata, as shown by 
the prolonged interval of delay between the fall of a luminous 
stimulus and the occurrence of the response. As the case is 
an interesting one, I shall state the particulars more fully. 
This Medusa, then, always responds to strong luminous 
stimulation by going into a spasm or cramp ; but it will not 
respond at all unless the light is allowed to fall upon its 
sense-organs for a period of more than one second ; if a slip- 
shutter is opened and closed again for a shorter period, no 



82 MENTAL EVOLUTION IN ANIMALS. 

response is made. It therefore seems certain that here we 
have not to deal with what physiologists call the period of 
latent stimulation, but with the time during which the light 
requires to fall in order to constitute an adequate stimulus ; 
just as a photographic plate requu-es a certain period of expo- 
sure in order to admit of the luminous vibrations throwing 
down the salt, so with the ganglionic material of this sense- 
organ. How different is the efficiency or development of 
such a visual apparatus from that of a fully perfected retina, 
which is able to effect the needful nervous changes in response 
to a stimulus as instantaneous as that supplied by a flash of 
lightning.* It is remarkable, looking to the Medusse as a 
whole, in what a wonderful degree these primitive sense- 
organs vary as to their minute structure in different species. 
Nerve-cells and fibres, wrought up into more or less complex 
forms, are clearly discernible in all those which have hitherto 
been carefully examined; but when the particular specific 
forms are compared with one another, it seems almost as if 
organs of special sense, where they first undoubtedly occur 
in the animal kingdom, revel, as it were, in the variety of 
forms which they are able to present. 

It is probable, from the structure of the lithocysts, that 
the Medusse are also affected by sonorous vibrations, and it 
is certain that they are richly supplied with a variety of 
organs ministering to the sense of touch. For not only are 
they furnished with numerous long, highly sensitive, and 
contractile tentacles, but in some species the marginal 
ganglia are provided with minute hair-like appendages, 
which must enable the nerve-cells to which they are attached 
to be exceedingly sensitive to anything touching the hairs. 
And, in connection with the sense of touch in the Meduste, I 
may allude to my own observations on the precision with 
which the point of contact of a foreign body is localized. 
A Medusa being an umbrella-shaped animal, in which the 
whole of the surface of the handle and the whole of the con- 
cave surface of the umbrella is sensitive to all kinds of stimu- 
lation, if any point in the last-named surface is gently 
touched with a camel-hair brush or other soft (or hard) 

* For a full account of these experiments, see Phil. Trans., vol. 166, 
Pt. I, Croonian Lecture, where it is shown that in other species of Medusse, 
the sense-organs of which are more highly developed, there is no such pro- 
longed delay in the response to luminous stimulation. 



SENSATION. 83 

object, the handle or manubrmm is (in the case of many 
species) immediately moved over to that point, in order to 
examine or to brush away the foreign body. This is especially 
the case in a species which for this reason I have called 
Tiaropsis indicans ; and here it is of interest to observe that 
if the nerve-plexus, which is spread all over the concave sur- 
face of the umbrella, is divided by means of an incision 
carried in the form of a short straight line parallel to the 
margin of the umbrella, and if a point below the line of 
incision is touched, the manubrium is no longer able to 
localize the seat of contact. Nevertheless it feels that con- 
tact is taking place someivhere, for it begins actively to dodge 
about from side to side of the umbrella, applying its ex- 
tremity now to one point and now to another of the umbrella 
surface, as if seeking in vain for the offending body. This of 
course shows that the stimulus, on reaching the ends of the 
severed nerve-fibres, spreads through the general nerve- 
plexus, and so arriving at the manubrium by a number of 
different routes, conveys a corresponding number of conflict- 
ing messages to the manubrium as to the point in the 
umbrella at which the stimulus is being applied. This irra- 
diation of a stimulus into other nerve-fibres when the 
stimulus reaches the cut ends of the fibres which constitute 
the habitual route of a stimulus between two points, is ren- 
dered the more interesting from the fact that in the case of 
the external nervous plexus of the Echinodermata there is no 
vestige of such a phenomenon. 

So much for the senses of sight (at least to the extent of 
distinguishing light from darkness), hearing, and touch, as 
localized in organs of special sense among the Medusae. In 
the allied Actiniae Mr. Walter Pollock and myself have ob- 
tained conclusive evidence of the sense of smell. Por we 
found that when a morsel of food is dropped into a pool or 
tank containing sea-anemones in a closed state, the animals 
quickly expand their tentacles.* It has been said that this 
may be taken to argue a sense of taste no less than a sense of 
smell ; but I conceive that here no distinction can be drawn 
between these two senses, any more than we can draw such a 
distinction in the analogous case of fish. Looking, then, to 
the Ccelenterata as a whole, we find that where we first meet 
with unmistakeable organs of special sense, we also first meet 

* See Journal Linnean Society, 1882. 



84 MENTAL EVOLUTION IN ANIMALS. 

with unmistakeable evidence of the occurrence of all the five 
senses — or, more correctly, with unmistakeable evidence of a 
power of adaptive response to all the five classes of stimuli 
which respectively affect the five senses of man. 

Coming next to the Echinodermata, Professor Ewart and 
myself have observed that Star-fish and Echini crawl towards 
and remain in the light, even though this be of such feeble 
intensity as scarcely to be perceptible to human eyes. 
Moreover, we proved that this exceedingly delicate power of 
discrimination between light and darkness is localized in the 
pigmented ocelli situated at the tips of the rays in Star-fish, 
and occupying the homologous positions in Echini. The 
sense of touch we found likewise to be highly delicate, and 
provided for by a variety of specially modified organs. 
Lastly, I found that the sense of smell occurs in Star-fish, 
though it is not localized in any special olfactory organs, 
being in fact distributed equally over the whole of the 
ventral surface of the animal, to the exclusion, however, of 
the dorsal.* 

Among the Articulata we meet with numberless grades of 
visual apparatus, from that of a simple ocellus, capable only 
of distinguishing light from darkness, up to the greatly 
elaborated compound eyes of insects and the higher Crus- 
tacea. These compound eyes are remarkable from the fact 
that each one of their possibly many thousand facets forms 
an image of the corresponding portion of the visual field — 
the multitude of separate sensory impressions being then 
combined into a mosaic-like whole by a sensorial operation 
taking place in the cephalic ganglion. In these compound 
eyes, moreover, the images are thrown upon the receptive 
nerve-surface without inversion. In the uncompounded or 
simple type of eye, on the other hand, the image is inverted, 
and as in the case of ants both kinds of eyes occur in the 
same individual, it has been thought a psychological puzzle 
how to explain the fact that mental confusion in the inter- 
pretation of images does not result. A little thought, how- 
ever, will show that the apparent puzzle is not a real one. 
Thus it is commonly said that we ourselves really see 
objects reversed, and that long practice enables us to correct 
the erroneous impressions. But this statement of the case is 

* See Phil. Trans., 1881, Pt. Ill, Croonian Lecture; and, for smeU in 
Star-fish, Journ. Linn. Soc, 1883. 



SENSATION. 85 

not correct. " We do not really see things reversed, for the 
mind is not a perpendicular object in space, standing behind 
the retina in the manner that a photographer stands behind 
his camera. To the mind there is no up or down in the 
retina, except in so far as the retina is in relation to the 
external world ; and this relation can only be determined, 
not by sight, but by touch. And if only tliis relation is 
constant, it can make no difference to the mind whether the 
images are direct, reversed, or thrown upon the retina at any 
angle with reference to the horizon ; in any case the corre- 
lation between sight and touch would be equally easy to 
establish, and we should always see things, not in the position 
in which they are thrown upon the retina, but in that which 
they occupy with reference to the retina. Thus it really re- 
quires no more * practice' correctly to interpret inverted 
images than it does similarly to interpret upright images ; 
and therefore the fact that some eyes of an ant are sup- 
posed to throw direct images, while others are supposed to 
throw inverted, is not any real objection to the theory* 
that they do.* 

There is no one group in' the animal kingdom where we 
have so complete a series of gradations in the evolution of an 
organ of special sense as is presented by the organ of sight in 
Worms. " In the lowest Vermes," — I quote from Professor 
Heeckelf — ^"the eye is only made up of individual pigment-cells. 
In others, refractive bodies are associated with these, and form 
a very simple lens. Behind these refractive bodies sensory 
cells are developed, forming a retina of the simplest order 
presenting a single layer, the cells of which are in connection 
with extremely delicate terminal fibres of the optic nerve. 
Lastly, in the Alcipidae, which are highly organized Annelidse 
that swim on the surface of the sea, adaptation to this mode 
of life has brought about such perfection of the eye that this 
organ in these animals is in no way inferior to that of the 
lower vertebrata. In these creatures we find a large globular 
eye-ball, enclosing externally a laminated globular lens, 
internally a vitreous body of large circumference. Imme- 
diately investing these are rods of the usual cells sensitive to 
light, which are separated by a layer of pigment-cells from 
the outer expansion of the optic nerve or retina. The ex- 

* Quoted from an article of my own in Nature, June 8, 1882. 
t Essay on Origin and Development of Sense-organs, 



86 MENTAL EVOLUTION IN ANIMALS. 

ternal epidermis invests the whole of the prominent eye-ball, 
and forms in front of it a transparent horny layer, the 
cornea." Further, from the more recent observations of 
Mr. Darwin, it is certain that Earthworms, although destitute 
of eyes, are able to distinguish with much rapidity and pre- 
cision between light and darkness ; and as he found that it is 
only the anterior extremity of the animal which displays this 
power, he concludes that the light affects the anterior ganglia 
immediately, or without the intervention of a sense-organ.* 
Lastly, Schneider says that Serpulse will suddenly withdraw 
their expanded tufts when a shadow falls upon them ; but the 
shadow must be that of an object moving with some rapidity.-f* 
Turning now to the sense of hearing in the Articulata, we 
find the simplest type of ear among the Vermes, where it 
occurs as a closed globular vesicle containing fluid in which 
there is suspended an otolith.^ In some of the Crustacea, 
such as the cray-fish and lobster, the organ of hearing is 
much more complex, and here, " if we give rise, by playing 
the violin, to notes of varying pitch, and at the same time 
observe the auditory organ under the microscope, we see that 
at each note only a particular auditory hair is set in vibra- 
tion."§ Among Insects organs of hearing certainly occur, at 
least in some species, although the experiments of Sir John 
Lubbock appear to show that ants are deaf. The evidence 
that some insects are able to hear is not only morphological, 
but also physiological, because it is only on the supposition 
that they do that the fact of stridulation and other sexual 
sounds being made by certain insects can be explained ; and 
Brunelli found that when he separated a female grasshopper 
from the male by a distance of several metres, the male began 
to stridulate in order to inform her of liis position, upon 
which the female approached him.|| I have myself published 
observations proving the occurrence of a sense of hearing 
among the Lepidoptera.H Turning to the morphological side 
of the subject, it is remarkable that in the Articulata the 

* See JEarthivorms, pp. 19-45. t -Z^^^ thierische Wille, s. 194, 

% Earthworms have no ears and are totally deaf, altliough very sensitive 
to vibrations eommunicated through contact with solid bodies. (See Darwin, 
loc. cit., pp. 26-7.) 

§ Hseckel, loc. cit., English translation, International Library of Science 
and Freethought, vol. vi, p. 325. 

II See Houzeau, Fac. Mem. des Animaux, t. i, p. 60. 

if See Nature, vol. xv, p. 177. 



SENSATION. 87 

auditory organs occur among different members of the group 
in widely different parts of the body. Thus in the lobster 
and cray-fish they are situated in the head at the base of the 
antennules, while in some of the crabs {e.g., Mysis) they occur 
in the tail. Among the Orthoptera, again, they are found in 
the tibige of the front legs, or, in other species, upon the sides 
of the thorax. In other insects, probability points to the 
organs of hearing being placed in the antennae. These facts 
prove that in the Articulata the sundry kinds of auditory 
organs must have arisen independently, and have not been 
inherited from a common ancestor of the group ; and it is 
remarkable that this should have been the case even within 
the limits of so comparatively small a subdivision as that 
which separates a crab from a crayfish or a lobster.* 

There can be no question that the sense of smell is well 
developed in at least many of the Articulata, although, save 
in a few cases, we are not yet in a position to determine the 
olfactory organs. Thus the account which I quoted in 
" Animal Intelligence" (p. 24), from Sir E. Tennent, concern- 
ing the habits of the land leeches of Ceylon, proves that 
these animals must be accredited with a positively astonishing 
delicacy of olfactory perception, seeing that they smeU the 
approach of a horse or a man at a long distance. In earth- 
worms the sense of smell is feeble, and seems to be confined 
to certain odours.-f Sir John Lubbock has proved by direct 
experiment that ants are able to perceive odours, and that 
they appear to do so by moans of their antennae. The same 
remark applies to bees, and the general fact that many insects 
can smell is shown by the general fact that so many species 
of flowering plants, which depend for their fertilization upon 
the visits of insects, give out odours to attract them. That 
the Crustacea are able to smell is rendered evident by the 
rapidity with which they find food. I have recently been 
able to localize the olfactory organs of crabs and lobsters by 
a series of experiments which I have not yet published, and 
which would occupy too much space here to detail. I shall 
therefore merely say that they are situated in the pair of 
small antennules, the ends of which are curiously modified in 
order to perform the olfactory function. That is to say, the 

* Analogous facts are to be observed in the case of the Eje among 
Vermes, and also, as we shall presently see, among MoUusca. 
t Darwin, loo. cif., p. 30. 



88 MENTAL EVOLUTION IN ANIMALS. 

terminal joint works in a vertical plane, and supports the 
sensory apparatus, which is kept in a perpetual jerking motion 
up and down, so as to bring that apparatus into sudden con- 
tact with any minute odoriferous particles which may be sus- 
pended in the water — just on the same principle as we our- 
selves smell by taking a number of small and sudden sniffs 
of air. Any one visiting an aquarium can have no difficulty 
in observing these movements upon any crab or lobster in a 
healthy condition. 

The sense of taste certainly occurs at least among some 
species of the Articulata (as, e.g., among the honey-feeding 
insects), and the sense of touch is more or less elaborately 
provided for in all. 

Turning now to the MoUusca, we pass in a tolerably 
uniform series from the simple eye-spots of certain of the 
Lamellibranchiata, through the Pteropoda, to the more com- 
pletely organized eyes of the Gasteropoda and the Heteropoda. 
But when we arrive at the Cephalopoda, we encounter, as it 
were, a vast leap of development ; for the eye of an octopus, 
in point of organization, is equal to that of a fish, which it 
so closely resembles. And, while remembering that the 
resemblance, striking though it be, is only superficial, we must 
not fail to note that this enormous development in the organi- 
zation of the molluscous eye, which brings it so strangely to 
resemble the eye of a fish, is clearly correlated with the no 
less enormous development of the neuro-muscular system of 
the animal, in which respect it more resembles a fish than it 
does the other Mollusca. This case is therefore analogous to 
the similarly high development which has been attained by 
the eye of the swimming worm previously described. 

If we look to the Mollusca as a class, we meet with the 
same kind of variation in the position of the eye which we 
have already noticed with respect to the ear in the Articulata. 
Thus, while in the Cephalopoda and Gasteropoda the eyes 
are situated in the head, in some of the latter group there 
are siipplementary eyes upon the back, which greatly differ 
in structure from the eyes in the head. In the Lamelli- 
branchiata, again, the eyes occur in large numbers on the 
margin of the mantle. 

The sense of hearing is general to all the Mollusca, and 
the auditory organs exhibit a progressive elaboration as we 
ascend from the lower to the higher groups, which is analo- 



SENSATION. 89 

goiis to that already noticed with reference to the organs of 
sight. Thus, among the lower Mollusca the organs of hearing 
consist of a pair of small vesicles attached to auditory- 
nerves, and filled with fluid in which an otolith is suspended. 
In the Cephalopoda, however, while the same general plan of 
structure is adhered to, we find an approximation to the 
auditory apparatus of a fish ; for the vesicle or sac is now 
embedded in the cartilage of the head, is of larger size, and 
in general analogous to the organ of hearing of the Verte- 
brata. That at all events the majority of the Mollusca are 
able to smell, is proved by the readiness with which they find 
food, and the octopus is said to show a strong aversion to 
certain odours (Marshall). In the Cephalopoda the olfactory 
organs are probably two small cavities near the back of the 
eye, and in the other Mollusca they are surmised to be situated 
in the small tentacles near the mouth. Touch is provided 
for both by these and by the larger tentacles (as well as by 
the general soft exterior) ; but in the Cephalopoda by the long, 
snake-like arms, which I think must be regarded as giving 
these animals a greater power of receiving tactile impressions 
than is enjoyed by any other marine animal. 

Among Fish sight is well developed. A trout will dis- 
tinguish a worm suspended in muddy water ; a salmon can 
avoid obstacles when swimming with immense velocity ; and 
a Chelmon rostratus can take unerring aim with its little 
water projectile at a fly. The blind fish, which live habitually 
in the dark, have lost their eyes merely from disuse ; but in 
this connection it must be noted that we meet with a curious 
biological puzzle in the case of many of the deep sea fishes 
dredged by the Challenger. Tor although living at depths to 
which no light can be supposed to penetrate, some of these 
fish have large eyes. It may be suggested that the use of 
these eyes is that of seeing the many self-luminous forms of 
life which, as the Challenger dredgings also show, inhabit the 
deep sea. But if this is suggested, the question immediately 
arises as to why these forms have become luminous ; for if 
thus rendered conspicuous to the fish, their luminosity must so 
far be a disadvantage to them. In the case of the lumi- 
nous animals which themselves have eyes, we may suppose 
that this disadvantage is more than compensated for by the 
advantage of enabling the sexes to find each other ; but this 
explanation does not apply to the blind forms. 



90 MENTAL EVOLUTION IN ANIMALS. 

Fish, as we have already observed, are well provided with 
the organs both of hearing and of smell, Amphioxus being the 
only member of the class which is destitute of ears, and the 
olfactory lobes in the case of some sj)ecies {e.g., the Skate) 
being of enormous size in relation to the other parts of the 
brain. The sense of touch is provided for in many species 
by tentaculse in the neighbourhood of the mouth. The soft 
lips, and in some species the pectoral fins, are also tactile in 
function, and in certain gurnards there are digitate appendages 
connected with the latter which doubtless serve to increase 
their efficiency as organs of touch. It is doubtful whether 
taste, as distinct from smell, occurs in fish; but we must 
remember, as before observed, that in the case of an aquatic 
animal there is no true distinction to be drawn between these 
two senses. For as there is here no gaseous medium (like 
the air) in question, the only distinction that can be drawn is 
as to whether the nerve terminations, which are affected by 
the suspended particles in the water, happen to be dis- 
tributed over any part of the mouth where the food passes, 
or over any other part of the animal. I say over any other 
part of the animal (and not only in the nasal fossae), because 
in some species of fish there are embedded in the skin along 
the sides of the body a number of curiously-formed papillae, 
which on morphological grounds may reasonably be regarded 
as ministering to the sense of smell, or, as we may indifferently 
call it, of taste. Hseckel, however, speculates upon these 
organs, and is inclined to think that they minister to some 
unknown sense. 

The sense of sight in Amphibia and Eeptiles offers 
nothing specially worthy of remark, except that the crystal- 
line lens has not so high a refracting power as in Fish. The 
transition from an eye adapted to see under water and an eye 
adapted to see in air, appears to be curiously shown by one 
and the same eye in the case of the Surinam Sprat. This 
animal has its eyes placed on the top of its head, so that 
when it comes to the surface of the water part of the eyes 
come into the air, and "the pupil is partly divided, and 
the lens is also composed of two portions, so that it is 
supposed that one part of this curious eye is adapted for 
aerial, and the other for aquatic, vision."* The senses of 
hearing, smell, taste, and touch, although all present in the 

* Marsliall, Outlines of Physiology, voL i, p. 603. 



SENSATION. 91 

Amphibia and Eeptiles, are not much, if at all, in advance of 
these senses as they occur in Fish. 

Among Birds the sense of sight is proverbially keen, and 
in point of fact the animal kingdom has no parallel to the 
excellence of the organ of vision as it occurs in some species 
of this class. Whether we consider the eye of a Hawk, which 
is able to distinguish from a great height a protectively 
coloured animal from the surface of the ground which it so 
closely imitates ; or the eye of a Solen Goose, which is able 
from a height of a hundred feet in the air to see a fish at the 
depth of many fathoms in the water ; or the eye of a Swift, 
which is able so suddenly to form its adjustments ; we must 
alike conclude that the visual apparatus has attained to its 
highest perfection among birds. And in this connection it is 
of interest to note that protective colouring has attained its 
highest degree of perfection among animals which constitute 
the prey of birds. So surprising, indeed, is the perfection to 
which protective colouring has attained in some of these 
cases, that it has been adduced as a difficulty against the 
theory of evolution ; for it seems incredible that such perfec- 
tion should have been attained by slow stages through natural 
selection before the species exhibiting it had been extermi- 
nated by the birds. The answer to this difficulty is that 
the visual organs of the birds cannot be supposed to have 
been always so perfect as they are now, and therefore that a 
degree of protective colouring which might have afforded 
efficient protection at an earlier stage in the evolution of 
those organs would not supply such protection at the present 
day. In other words, the evolution of the eyes of birds and 
of the protective coloration of their prey must be supposed 
to have progressed pari passu, each stage in the one acting 
as a cause in the succeeding stage of the other. The crystal- 
line lens is flat in birds which are remarkable for long sight, 
such as the vulture ; rounder in owls, which are very near- 
sighted ; and becomes progressively more spherical in aquatic 
birds, according to their aquatic habits. 

All birds are able to hear, and it is in this class that we 
first meet with definite evidence of an ear capable of appre- 
ciating with delicacy differences of pitch. Among many 
species of birds the delicacy of such appreciation (as well as 
that of timbre) is so remarkable that it may be questioned 
whether even human ears are more efficient in this respect. 



92 MENTAL EVOLUTION IN ANIMALS. 

The anatomical difficulty of accounting for this fact I need 
not wait to consider. I am myself inclined to think that the 
sense of hearing in birds (at all events of some species) is 
likewise highly delicate with reference to the intensity of 
sound. My reason for so thinking is that I have observed 
Curlews dig their long bills up to the base into smooth 
unbroken surfaces of sea-sand left bare by the tide, in order 
to draw up the concealed worms. Under such circumstances 
no indication can be given by the worm of its position to any 
other sense of the curlew than that of hearing. Similarly, I 
suspect that the common Thrush is guided to the worm buried 
beneath the turf by the sense of hearing, and my suspicion is 
founded on the peculiar habits of feeding shown by the bird, 
which I have described elsewhere.* 

The sense of smell in Birds is in advance of that of 
Eep tiles, but not to be compared with its excellency in 
Mammals ; for the old hypothesis that vultures find their 
prey by the aid of this sense has been abundantly disproved.! 
The sense of taste in Birds is likewise very obtuse as com- 
pared with this sense in Mammals ; and as compared with 
the same class they are also defective in their organs of 
touch. Indeed, the parrot tribe is the only one in which 
this sense is well or specially provided for, except the ducks, 
snipes, and other mud-feeding species, in which the bill is 
specially modified for this purpose. 

If we regard Mammals as a class we must say that, with 
the exception of the sense of vision which readies its 
greatest supremacy in Birds, all the special senses are more 
highly developed than in any other class. This is more 
particularly the case with the senses of smell, taste, and 
touch. 

The sense of smell reaches its highest perfection among 
the Carnivora and the Euminants, and, on the other hand, is 
totally absent in some of the Cetacea. Any one accustomed 
to deer-stalking must often have been astonished at the pre- 
cautions which it is needful to take in order to prevent the 
game from getting the " wind "of the sportsman ; indeed to 
a novice such precautions are apt to be regarded as implying 
a superstitious exaggeration of the possibilities of the olfac- 

* Nature, vol. xv, pp. 177 and 292, where also see in more detail my 
observations on the feeding habits of the curlew. 
t See Animal Intelligence, pp. 28G-7. 



SENSATION. 93 

tory sense ; and it is not until he has himself seen the deer 
scent him at some almost incredible distance that he lends 
himself without disguised contempt to the discretion of the 
keeper. But among the Carnivora the sense of smell is even 
more extraordinary in its development on account, no doubt, 
of its being here of so much service in tracking prey, I 
once tried an experiment with a terrier of my own which 
shows, better than anything that I have ever read, the almost 
supernatural capabilities of smell in Dogs. On a Bank 
holiday, when the broad walk in Eegent's Park was swarm- 
ing with people of all kinds, walking in all directions, I took 
my terrier (which I knew had a splendid nose, and could 
track me for miles) along the walk, and, when his attention 
was diverted by a strange dog, I suddenly made a number of 
zig-zags across the broad walk, then stood on a seat, and 
watched the terrier. Finding I had not continued in the 
direction I was going when he left me, he went to the place 
where he had last seen me, and there, picking up my scent, 
tracked my footsteps over all the zig-zags I had made until 
he found me. Now in order to do this he had to distinguish 
my trail from at least a hundred others quite as fresh, and 
many thousands of others not so fresh, crossing it at all angles. 

Such being the astonishing perfection of smell in dogs, it 
has been well observed that the external world must be to 
these animals quite different from what it is to us ; the 
whole fabric of their ideas concerning it being so largely 
founded on what is virtually a new sense. But in this con- 
nection I may point out that speculation on such a subject is 
shown to be useless by the fact that the sense of smell in 
dogs does not appear to be merely our own sense of smell 
greatly magnified. For if this were the case it seems incredible 
that highly bred sporting-dogs, which have the finest noses, 
should be those which take the keenest pleasure in rolling in 
filth which literally stinks in our nostrils to the degTee of 
being physically painful. 

The sense of hearing is acute in Mammals as a class, and 
it is worthy of remark that this is the only class provided 
with movable ears. As Paley observes, in beasts of prey the 
external ear is habitually directed forwards, while in species 
which they prey upon the ear admits of being directed back- 
wards. With the exception of the singing monkey {Hylobates 
agilis), there is no evidence of any mammal other than man 
5 



94 MENTAL EVOLUTION IN ANIMALS. 

having any delicate perception of pitch. I have, however, 
heard a terrier, which used to accompany a song by howling, 
follow the prolonged notes of the human voice with some 
approximation to unison ; and Dr. Huggins, who has a good 
ear, tells me that his large mastift" " Kepler " used to do the 
same to prolonged notes sounded from an organ. 

The sense of taste is much more highly developed in the 
Mammalia than in any other class, and the same general 
statement applies to the sense of touch. Looking to the 
class as a whole, the principal organs of the latter are the 
snout, lips, and tongue ; the modified hairs, or " whiskers," 
are also very generally present. Among the Rodents, some of 
the Mustelidse and all the Primates, the principal organs of 
touch are the hands. And it would appear that the extreme 
modification which these members have undergone in the 
Cheiroptera has been attended with an extraordinary exalta- 
tion of their power of tactile sensation. For in the celebrated 
experiment of Spallanzani (since repeated and confirmed by 
several other observers), it was found that when a Bat is 
deprived of its eyes, and has its ears stopped up witli cotton- 
wool, it is stni able to fly about without apparent inconveni- 
ence, seeing that it avoids all obstacles in its flight, even 
though these be but slender strings stretched through the 
room in which the animal is allowed to fly. The only expla- 
nation of this surprising fact is that the membranous 
expanse of the wing, which is richly supplied with nerves, 
has developed a sensibility to touch, to temperature, or to 
both, so extreme as to inform the bat of the proximity of a 
solid body even before contact — either through the increase 
in the air-pressure as the wing rapidly approaches the solid 
body, or through the difference in the exchange of heat 
between the wing and the solid as compared with such ex- 
change between the wing and the air. When groping our way 
through a dark room we are ourselves able to feel a large 
solid body (such as a wall) before we actually touch it, 
especially, I have observed, with the skin of the face. Pro- 
bably, therefore, it is a great exaltation of this power which 
enables these night-flying animals to avoid so slender a solid 
body as a stretched string. But when we remember the 
rapidity and accuracy with which the sensation must here be 
aroused, we may well consider it to equal, if not to surpass, 
in the domain of touch, the evolutionary development of 



SENSATION. 95 

sense-organs as it occurs in the sight of the vulture or the 
smell of the dog. Indeed, Heeckel and others have specu- 
lated whether the facts in this case do not call for the suppo- 
sition of some additional and unknown sense, different in 
kind from any that we ourselves possess. But I think it is 
safer not to run into any such obscure hypothesis unless 
actually driven to do so, and therefore I shall not here enter- 
tain it. For this reason, also, I shall not follow Hseckel in 
his view that the " homing " faculty of certain animals is due 
to some additional and inexplicable sense, and therefore I 
shall reserve my treatment of this topic for my chapters on 
Instinct. 

After this rapid survey of the powers of Special Sense as 
they severally occur in different classes of the animal king- 
dom, I shall conclude the present chapter by briefly consider- 
ing certain general principles connected with Sensation. 

The muscular sense, the sense of hunger, thirst, satiety, 
and others of the like general kind need not detain us ; for 
although their causation is somewhat obscure, we know at 
least that they are dependent upon nervous adjustments, 
and, being of so much importance to animals, we infer that 
they have been developed under the general principles of 
neuro-muscular evolution already considered in previous 
chapters. My object here is rather to consider the mecha- 
nisms of certain more special senses from the point of view 
of those general principles. 

First as to the sense of Temperature, there is good evi- 
dence that in ourselves and at least in all the higher animals, 
thermal sensations can only be received by the nerve-endings 
in the skin and adjacent parts of the mucous membranes ; if 
the nerve-fibres immediately above their terminations in 
these localities (as in the raw surface of a wound) be stimu- 
lated by heat or cold, the sensation produced is merely one 
of pain. There is strong evidence that not only the nerve- 
endings, but even the whole of the nerve-tracts of which 
they are the endings, are specialized for the purpose of re- 
ceiving thermal impressions. These impressions, when 
received, are not absolute, but relative to the temperature of 
the part receiving them — the greater the difference of tem- 
perature between the part and the object touching it, the 
greater being the impression. Moreover, the greater the 



96 MENTAL EVOLUTION IN ANIMALS. 

extent of the receiving surface, the greater is the impression ; 
so that if the whole hand be immersed in water at 102°, the 
temperature of the water will be erroneously judged to be 
higher than that of another body of water at 104° the tem- 
perature of which is simultaneously estimated by a single 
finger of the other hand ; and, similarly, smaller differences 
of temperature can be appreciated by the whole hand 
than by a single finger. According to Weber, the left hand 
is considerably more sensitive to temperature than the right ; 
and it is certain that different parts of the body differ greatly 
in this respect. The more sudden the change of temperature, 
the greater is the sensory effect. We have no means of 
testing the truth of any of these statements with reference 
to any of the Invertebrata, or even with reference to the 
cold-blooded Vertebrata ; but we can scarcely doubt that 
they apply in a general way to all the warm-blooded. The 
facts certainly show an elaborate provision for appreciating 
local changes of temperature occurring upon this and that 
part of the external surface (the general comfort or discom- 
fort arising from the body being kept at a normal tempera- 
ture or not is another matter, and one with which the special 
mechanism we are considering is not concerned) ; and there- 
fore we have to contemplate the probable cause of its origin 
and development. 

At first sight we appear to encounter a difficulty which I 
wonder never to have seen adduced by opponents of evolu- 
tion. For in nature the only differences of temperature 
which normally occur in objects with which animals have 
any opportunity of coming into contact, are those between 
ice and objects heated by a tropical sun ; and no one animal 
ever has the opportunity of experiencing changes of tem- 
perature extending through anything like so great a range ; 
for in the arctic regions there is no tropical sun, in the 
tropics there is no ice, and in the temperate zones the solar 
heat is moderate. Of course since the introduction of fire by 
man, the sense of temperature has become of much use to 
sundry species of animals for the examination of food, &c., and 
in this connection is of almost indispensable service to man 
himself; but, looking to the antecedents of these animals 
and also to the antecedents of man, it may at first sight 
seem remarkable that such an elaborate provision should 
have been developed, and, as I have said, I wonder that no 



SENSATION. 97 

opponent of evolution has pointed to the fact. For it might 
be argued that here we have a complicated piece of special 
organic machinery constructed in obvious anticipation of the 
advent of cookery and warm baths. But I think the matter 
may be explained on evolutionary principles, if we remember 
that the only use of a sense of temperature is not that of 
examining food. We know that differences of temperature 
on the surface of the body (whether local or general) greatly 
modify the conditions of the circulation in the part or parts 
affected, and therefore it must always have been of use for 
animals to be provided with a sensory apparatus upon the 
surface of their bodies to give them immediate information 
of such differences. Its development along special lines (so 
that some parts of the body should be more sensitive to 
changes of temperature than other parts) is easily to be 
explained by the effects of habit or use. Thus, for example, 
the fact that the lips of man, although provided with a skin 
so delicate and so sensitive to tactile impressions, are never- 
theless able to endure a sudden rise of temperature which 
would be painful to the skin of the face, must be taken to 
mean that habit has adapted the nerves in the lips to with- 
stand a sudden rise of temperature — and this certainly within 
the period since the invention of cookery. 

Mr. Grant Allen takes a more general view of this sub- 
ject, and says : " To an animal, cold is death, and warmth is 
life. Hence it is not ar.tonishing that animals should very 
early have developed a sense which informed them of 
changes of temperature taking place in their vicinity ; and 
that this sense should have been equally diffused over the 

whole organism As soon as moving creatures 

began to feel at all, they probably began to feel heat and 
cold."* The truth of such a general statement of this must 
be obvious, and the step between a sense of temperature 
equally diffused over the whole organism, and the specializa- 
tion of superficial nerve-endings to minister to this sense 
alone, is not a large step. Moreover, the step between this 
and the development of a rudimentary visual organ is like- 
wise not a large one. For the deposition of dark-coloured 
pigment in particularly exposed parts of the skin must have 
been of benefit to animals by enabling (in virtue of the 
increased absorption of heat thus secured) the nerve-endings 

* Colour Sense, p, 13. 



98 MENTAL EVOLUTION IN ANIMALS. 

in those parts to be more sensitive to changes of temperature. 
But the deposition of pigment in such localities constitutes a 
favouring condition to the origination of an eye, or of an 
organ whose sense of temperature becomes sufficiently 
developed to enable it to begin to distinguish between light 
and darkness. Thus, as Professor H?eckel eloquently re- 
marks : " The ordinary nerves of the skin which pass to these 
dark pigment-cells of the integument, have already trodden 
the first steps of that magnificent march, at the end of which 
they have attained to the highest development of the nerves 
of sensation — the optic nerves." 

Turning next to the sense of Colour, it appears from the 
experiments of Engelmann already alluded to, that colour- 
sense of a kind occurs as low down in the zoological scale as 
the protoplasmic and unicellular organisms, inasmuch as 
particular species showed particular preferences for certain 
rays of the spectrum. But as in these organisms there are 
no organs of special sense, and probably no beginnings of 
consciousness, I do not think that any true analogy can be 
drawn between these cases and those in which there is a true 
sensation of colour. Nor have we any e%ddence of such a 
true sensation till we arrive at the Crustacea. Here we 
have proof, furnished by the direct experiments of Sir John 
Lubbock, that Daphnia pulex prefers certain rays of the 
spectrum to others,* and the Chameleon Shrimp (Mysis chcu- 
rneleo) is known to change its colour in imitation of the 
surface on which it reposes, provided that it is not blinded 
or otherwise prevented from seeing that surface. Precisely 
analogous facts occur among the Cephalopoda {e.g., octopus), 
Batrachia {e.g.. Common Frog), Eeptilia {e.g., Cameleon), and 
Pisces {e.g., Flounder) ; in all these cases, if the animals are 
blinded, the effects no longer occur. Moreover, Pouchet 
found that in the Pleuronectidae the mechanism whereby 
these imitative changes of colour are produced is bilaterally 
disposed, so that if only one eye of the animal is stimulated 
by coloured light, only one side of the animal changes colour. 
jM. Fredericq afterwards found the same thing to be true of 
the Octopus, and in conjunction with Professors Burdon- 

• Journ. Linn. Soc, 1881. These observations have been adversely criti- 
cized by Mereikowsky (Comptes Rendus, xciii, pp. 160-1), but his criticisms 
have been fully met by further experiments recently published by Sir John 
{■Tourn. Linn. Soc, 1883). 



SENSATION. 99 

Sanderson, Cossar Ewart, and Mr. W. D. Scott, I have 
corroborated M. Fredericq's observations by a number of 
experiments ; stimulation of one eye alone by means of light 
produces immediate unilateral flushing of the whole of the 
same side of body, but no change of colour beyond the median 
line. 

As fm'ther proof that a well-developed sense of colour 
occurs in some of the Articulata, I may allude to the experi- 
ments of Sir John Lubbock on the Hymenoptera; but as 
these have been already twice published in the International 
Scientific Series,* I need not here wait to recapitulate them, 
and shall therefore only remark that it is without any rea- 
sonable question to the presence of this sense in insects that 
we owe the beauty both of floral and of insect coloration. 
Again, as further proof that a well-developed sense of colour 
occurs in Fish, I may remark that the elaborate care with 
which anglers dress their flies, and select this and that com- 
bination of tints for this and that locality, time of day, &c., 
shows that those who are practically acquainted with the 
habits of trout, salmon, and other fresh-water fish, regard the 
presence of a colour-sense in them as axiomatic. And, with 
reference to the sea-water fish in general, we have the highly 
competent opinion of Professor H. N. Moseley to the efiect 
that the great majority of the colours of marine animals 
have been acquired either for the protection or the allure- 
ment of prey, and that they refer particularly to the eyes of 
Fish, and also to those of Crustacea.! 

The fact that a sense of colour occurs in Birds is unques- 
tionable, and meets with its most general proof in the more 
or less conspicuous coloration of the fruits on which they 
feed ; for as in the analogous case of conspicuously coloured 
flowers depending on insects for their fertilization, so con- 
spicuously coloured fruits depend for the dissemination of 
their seeds upon being eaten by birds or mammals. Again, 
I have already mentioned the fact that nowhere in the 
animal kingdom does the protective and imitative colouring 
of animals attein to such nicety as it does where the eyes 
of birds are concerned. Lastly, the elaborate coloration of 
birds themselves, and the pleasure which some species take 
in the decoration of their nests, constitute supplementary 

* Viz., in Anfs, Bees, and Wasps, and in Animal Intelligence. 

t Quarterli/ Journ, Micro. Science, New Series, vol. xtU, pp. 19-22. 



100 MENTAL EVOLUTION IN ANIMALS. 

proof of the high development to which the colour-sense has 
attained in this class. 

All the remarks just made with reference to Birds, apply 
likewise, though not perhaps in quite so high a degree, to 
Mammals, considered as a class. And here it becomes need- 
ful to consider the speculation of Dr, Magnus and Mr. Glad- 
stone, that the colour-sense of man has undergone a great 
improvement within the last two thousand years, inasmuch 
as before that time mankind are supposed by this specula- 
tion to have perceived only the lower colours of the spec- 
trum, or red, orange, and yellow, and to have been colour- 
blind to the higher, or green, blue, and violet. Professor Hseckel 
lends his support to this speculation ; but to me it seems a 
highly improbable one, and this for the following reasons. 

In the first place the speculation is based merely on 
etymological grounds, which in a matter of this kind are 
exceedingly unsafe. For the absence in a language of words 
denoting particular colours is, at best, but negative evidence 
that the men who spoke the language were blind to those 
colours ; the absence of such words may quite as well be due 
to the imperfection of language as to the imperfection of the 
visual sense. Thus, for instance, Professor Blackie tells us that 
the Highlanders call both sky and grass "gorm," and are 
nevertheless quite able to discriminate between the colours 
blue and green. In the next place, it is antecedently im- 
probable, upon the general principles of evolution, that a 
considerable change in the visual apparatus of man should 
have taken place within so short a period as the speculation 
in question assigns — especially in view of the fact that other 
Mammals, Birds, and even some of the Invertebrata un- 
questionably distinguish the higher as well as the lower 
colours of the spectrum. Lastly, Mr. Grant Allen has taken 
the trouble to enqui;re, by means of a table of questions 
addressed to educated Europeans in all parts of the world, 
whether any of the savage races of mankind now living 
display any inability to distinguish between the colours of 
the spectrum, and the answers which he has received have 
been uniformly in the negative.* I think, therefore, we may 
safely dismiss the speculation of Dr. Magnus and Mr. Glad- 
stone as opposed to all the evidence which is at once trust- 
worthy and available. But in saying this I do not intend to 

• Coluu7--sense, Chapter X. 



SENSATION. 101 

dispute tlie probability, which indeed amounts almost to a 
certainty, that as civilization advances and the fine arts 
become developed, the colour-sense undergoes a progressive 
improvement in its power of distinguishing between fine 
shades, and also in its power of ministering to a more and 
more evolved condition of aesthetic feeling. And this, I 
believe, is the true explanation of the class of facts alluded to 
by Professor Hseckel as proof of the speculation which I have 
now discarded — the fact, namely, that " nowadays we see in 
the surviving savage races a crudity as to their sense of 
colour .... Our little ones, also, like the savages, 
love assemblages of glaring hues which grate upon us, and 
susceptibility to the harmony of delicate shades of colour is 
the latest product of aesthetic education." 

Professor Preyer has published within the last year or two 
a very interesting theory touching the origin and development 
of the colour sense, and as it has not, to my knowledge, been 
noticed in any English publication, I shall here state the main 
points. The theory is that the colour-sense is a special and 
highly-exalted development of the sense of temperature. To 
sustain this theory, Professor Preyer first compares the sensi- 
bility of the skin to temperature with that of the retina to 
light, and points out that the analogy has already been 
recognized by artists, who speak of colours as " warm " and 
" cold." " The warm colours arouse sensations of a character 
antagonistic to those which are aroused by the cold colours, 
in just the same M^ay as the hot and cold sensations of skin- 
temperature are antagonistic ; and the more this analogy is 
pursued, the closer is the agreement found to be." Therefore 
the suggestion arises, " that the sense of colour has been 
developed out of the sense of temperature," bespeaking a 
high refinement of functional activity which has its struc- 
tural correlative in the extremely differentiated and delicately 
organized expansion of nerve-endings which we find in the 
retina. 

A further analogy is that of contrasts. A finger that has 
been warmed or cooled retains its change of temperature for 
seme time after it has ceased to be warmed or cooled ; and 
this is taken to correspond with the phenomena of positive 
after-images in sensations of colour. Moreover, while the 
after-effect of warming or cooling a portion of the skin 
remains, the temperature-sense of that portion is altered in 



102 MENTAL EVOLUTION IN ANIMALS. 

sucli wise that, if it has been cooled, it over-estimates the 
temperature of any object it may touch, and vice versd. This 
is taken to be analogous to the appearance of warm colours 
in the eyes when closed immediately after having been 
exposed to intense cold coloars, and vice versd. So, too, it is 
with simultaneous contrasts. It is well known that if a 
small colourless surface is enclosed between two surfaces of 
cold or warm colours, the small surface will appear inversely 
coloured warm or cold, as the case may be ; and Professor 
Preyer has found by experiment, that if a small portion of the 
skin be enclosed by cold or warm surfaces on either side, the 
small enclosed area will feel cool if the neighbouring parts 
are heated, and vice versd. 

After showing that in his view illumination is to the 
sense of colour what contact is to the sense of temperature, 
and pointing out several subordinate analogies which I have 
no space to mention, Professor Preyer goes on to remark an 
important fact in relation to his theory, viz., that different 
parts of the skin manifest in their estimations of tempera- 
ture great differences in their estimates of what he calls the 
" neutral point," i.e., the point at which it cannot be said that 
a body is felt to be either hot or cold. The retina, then, being 
supposed to be merely a nerve-expansion having a much 
higher " neutral point " in the appreciation of temperature 
(ethereal vibrations) than has any nerve-expansion of the 
skin, colour-blindness is explained by supposing that the 
retina of the individual so affected has a neutral point either 
above or below the normal. " An over- warm eye must be 
blind to yellow and blue ; an over cool one must be blind to 
red and green." Total colour-blindness, which is a physio- 
logical characteristic among certain nocturnal animals, has its 
parallel in the pathological condition sometimes met with in 
man, of a total absence of the sense of temperature without 
impairment in the sense of touch. 

Lastly, it is observed that the first condition to the 
validity of any physiological hypothesis is that it should 
accord with morphological fact. But this is not the case with 
the theory of Young and Helmholtz, which ascribes the 
colour-sense to the functions of three retinal elements ; for it 
has been proved that the number of fibres in the optic nerve 
immediately before it enters the retina is much smaller than 
the number of rods and cones in the retina. 



SENSATION. 103 

In my opinion this theory, in its main outlines, seems a 
probable, as it certainly is a plausible one. I do not, indeed, 
quite understand why, in accordance with the theory, the 
" neutral point " of the colour-blind should not merely be 
found to be shifted to another part of the spectrum, nor am I 
quite clear about the explanation of the fact that the warm 
colours are those having the lowest and not the highest order 
of vibrations, as analogy would lead us to expect. But the 
theory has the merit of being antecedently probable, when we " 
remember that in all likelihood the visual sense arose by the 
progressive elaboration of nerve-endings in particular parts of 
the skin, which before their special elaboration presumably 
ministered to the senses of touch and temperature. 

And this remark leads me to the last topic that I have to 
dwell upon in the present chapter. I refer to the body of 
morphological evidence which we now possess, showing that 
all the organs of special sense have had their origin in special 
elaborations of these nerves of the integument. For- the 
uniform result of histological and embryological investigation 
is to show that all organs of special sense, wherever they 
occur and whatever degree of elaboration they present in the 
adult animal, are fundamentally alike in that their receptive 
surfaces are composed of more or less modified epithelium 
cells which originally constituted part of the external layer 
of the animal. Thus, the origin of the olfactory membrane 
in the embryo of the Vertebrata is found to consist in a pitting 
of the skin of the fore part of the head — the pits, therefore, 
being lined by the general layer of epidermic cells. The 
subsequent growth of the surrounding parts of the face 
eventually brings this lining to occupy the position which it 
does in the hollow parts of the nose. Similarly, the organs 
of hearing first begin as a pair of pits on the side parts of the 
head, situated somewhat far back, and likewise lined by the 
cells of the general integument. These pits rapidly deepen, 
so that their lining is pinched off or separated from the 
general integument of which it originally formed a part. The 
deep pit then becomes a closed sac, and the adjacent tissues 
becoming first cartilaginous and then osseous, this sac is 
enclosed well within the skull by bony walls. While its 
structure is undergoing further anatomical and histological 
changes, the drum, the chain of ear-bones, and the external 
ear are being formed, and thus eventually the auditory organ 



104 MENTAL EVOLUTION IN ANIMALS. 

is completed. In the case of the eye, again, the earliest sign 
of commencement consists in a similar pitting of the general 
integument, but the lining of this pit is not destined, as in 
the previous cases, to become the receptive surface of the 
sensory impressions. For, after it has deepened considerably 
it undergoes sundry changes which result in its forming the 
cornea, aqueous humour, and crystalline lens; while the 
retina arises as an offshoot from the brain in the form of a 
sac growing, as it were, upon a slender stalk towards the 
crystalline lens. At first the anterior surface of this sac is 
convex, but the posterior part afterwards becomes pushed 
into the cavity of the sac ; so that the anterior surface 
eventually becomes strongly concave. Therefore the sac is 
now, as Professor Huxley graphically describes it, "like a 
double night-cap, ready for the head, but the place which the 
head would occupy is taken by the vitreous humour, while 
the layer of night-cap next it becomes the retina." Thus the 
rods and cones of the retina are not developed immediately 
out of the epidermic cells of the integument ; but inasmuch as 
the brain is itself begun as an infolding of the epidermic layer, 
the rods and cones of the retina are ultimately derived from 
those epidermic cells. Or, again to quote Professor Huxley, 
"the rods and cones of the vertebrate eye are modified 
epidermal cells, as much as the crystalline cones of the insect 
or crustacean eye are."* Therefore, in the words of Professor 
Hseckel, " the general conclusion has been reached that in 
man, and in all other animals, the sense-organs as a whole 
arise in essentially the same way, viz., as parts of the external 
integument or epidermis. The external integument is the 
original general sense-organ. Gradually the higher sense- 
organs detach themselves from this their primal condition, 
whilst they withdraw more or less completely into the pro- 
tecting parts of the body. Nevertheless in many [inverte- 
brate] animals, even at the present hour, they lie in the 
integument, as e.g., in the Vermes." 

I have entered thus fully into this general fact, because 
it is of importance, not only to the theory of evolution, but 
also to the philosophy of sensation, to know from such direct 
historical sources that all the special senses are differentiations 
of the general sense of touch. 

• Science and CuUure, &c., p. 271. 



PLEASURES AND PAINS. 105 



CHAPTER VIII. 

Pleasures and Pains, Memory, and Association of Ideas. 

In the diagram I have represented Pleasures and Pains as 
occupying in their first origin a level not far removed from 
that at which Sensation takes its . rise. I have also repre- 
sented a short interval between Sensation and the origin of 
Perception, which is filled up in the lateral column -by 
Memory and Primary Instincts. Therefore, before we pass 
on to consider the rise of Perception out of Sensation, I shall 
devote a chapter to a consideration of Pleasures and Pains, 
Memory, and Association of Ideas. 

Pleasures and Pains. 

On this topic I have little to add to the treatment which 
it has received at the hands of Mr. Herbert Spencer, and of 
his disciple, Mr. Grant Allen.* Pains, as Mr. Spencer points 
out, may be due to the want of action (" craving "), or to an 
excess of action. These two classes correspond largely, 
though not entirely, with the division of pains into massive 
and acute, which is formulated by Professor Bain. It also 
indicates the doctrine of Sir W. Hamilton and others, that 
Pain is due to excessive stimulation. But it is important to 
observe that the statement of Mr. Spencer, while " recognizing 
at one extreme the positive pain of excessive actions," recog- 
nizes also " at the other extreme the negative pains of in- 
actions ; the implication is that Pleasures accompany actions 
lying between these extremes." 

Mr. Grant Allen in the course of his able exposition of 
this subject, shows by many examples that "the Acute 
Pains, as a class, arise from the action of surrounding 

* See Principles of Pnychology and Physiological Esthetics, in both 
cases the chapter on " Pleasures and Pains." 



106 MENTAL EVOLUTION IN ANIMALS. 

destructive agencies; the Massive Pains, as a class, from 
excessive function or insufficient nutriment:" also that 
" Massive Pains, when pushed to an extreme, merge into the 
Acute Class," so that " the two classes are rather indefinite in 
their limits, being simply a convenient working distinction, 
not a natural division." Hence it follows that Pains of both 
classes " are the subjective concomitants of an actual disrup- 
tion or disruptive tendency in some one (or more) of the 
bodily tissues, provided the tissue be supplied with afferent 
cerebrO'Spinal nerves in unbroken connexion with the brain." 
Eeferring the reader to Mr. Allen's own essay for all matters 
of detail and criticism, I shall merely say that in my opinion 
he has successfully established this formula as applicable to 
all cases of Pain. His view concerning the physiology of 
Pleasure is substantially the same as that of Mr. Spencer 
already quoted ; but it is somewhat more extended and pre- 
cise. This view is that Pleasure is " the concomitant of a 
normal amount of activity in any portion or the whole of the 
organism," supplemented with the important addendum that 
" the strongest Pleasures result from the stimulation of the 
largest nervous organs, where activities are most intermittent ;" 
so that the amount of Pleasure is "in the direct ratio of the 
number of nerve-fibres involved, and in the inverse ratio of 
the natural frequency of excitation." Hence " we see wherein 
the feeling of Pleasure fails to be exactly antithetical to the 
feeling of Pain, just as their objective antecedents similarly 
fail. Massive Pleasure can seldom or never attain the inten- 
sity 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 extremely 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." 
Now towards what conclusion do these generalizations 
point ? They clearly point to the conclusion, which I do not 
think is open to any one valid exception, that Pains are the 
subjective concomitants of such organic changes as are harm- 
ful to the organism, while Pleasures are the subjective con- 
comitants of such organic changes as are beneficial to the 
organism — or, we must add, to the species. The more this 



PLEASURES AND PAINS. 107 

doctrine is pursued in detail, the more unquestionable does 
its truth become. Thus there is to be perceived, not merely 
a general qualitative, but also a roughly quantitative relation 
between the amount of pain and the degree of hurtftdness, as 
well as between the amount of pleasure and tlie degree of 
wJiolesomeness.* As Mr. Allen observes, *•' nothing can more 
thoroughly mihtate against the efficiency of the mechanism 
than the loss of one of its component parts : and we find 
accordingly that to deprive the body of any one of its mem- 
bers is painful in a degree roughly proportionate to the 
general value of such member to the organism as a whole. 
Take, for example, the relative painfulness of severing from 
the body a leg, an arm, an eye, a finger-nail, a hair, or a piece 
of skin." Similarly with Pleasures, the least pleasurable are 
those attending activities of the organism which are least 
important for its welfare (or for that of its species), while 
the most pleasurable are those which attend the satisfaction 
of hunger, thirst, and sexual desire — especially if, in terms of 
Mr. Allen's formula, the needs to which these cravinos 
minister have been long unsatisfied, so that the organism is 
either in danger of enfeeblement and death, or in the most 
fit condition for propagating its kind. Pleasures of the intel- 
lectual kind, although subservient to the same general laws 
of nutrition and exhaustion, have reference to such complex 
nervous states, involving mental prevision of future contin- 
gencies, &c., that for the purposes of clear analysis they had 
best be here disregarded. 

The superficial or apparent objection to the doctrine we 
are considering which arises from the fact that feelings of 
Pleasure and Pain are not infallible indices of what is respec- 
tively beneficial or injurious to the organism, is easily met by 
the consideration that in all such exceptional cases it is not 
the doctrine but its application which is at fault. Thus, 
again to quote Mr, Allen, who in my opinion has given in 
brief compass the best analysis of the philosophy of Pleasure 
and Pain that has hitherto appeared, " every act, so long as 
it is pleasurable, is in so far a healthy and useful one ; and 
conversely, so long as it is painful, a morbid and destructive 
one. The fallacy lies in the proleptic employment of the 
words ' deleterious ' and ' useful.' To put it in a simple form, 

* I use these antithetical words because their etjmology alone suggests 
forcibly the doctrine in question. 



108 MENTAL EVOLUTION IN ANIMALS. 

the nervous system is not 'prophetic. It informs us of what 
is its actual state at the moment, not what the after-effects of 
that state will be. If we take sugar of lead, we receive at 
first a pleasant sensation of sweetness, because the immediate 
effect upon the nerves of tas^te is that of a healthy stimu- 
lation. Later on, when the poison begins to work, we are 
conscious of a painful sensation of griping, because the nerves 
of the intestines are then being actually disintegrated by the 
direct or indirect action of the irritant." 

Now if the doctrine before us is found to apply generally 
to all cases of Pleasure and of Pain, the implication is suffi- 
ciently apparent ; Pleasures and Pains must have been 
evolved as the subjective accompaniment of processes which 
are respectively beneficial or injurious to the organism, and 
so evolved for the purpose or to the end that the organism 
should seek the one and shun the other. Or, to quote 
Mr. Spencer, " if we substitute for the word Pleasure the 
equivalent phrase — a feeling which we seek to bring into 
consciousness and retain there, and if we substitute for the 
word Pain the equivalent phrase — a feeling which we seek to 
get out of consciousness and to keep out; we see at once 
that, if the states of consciousness which a creature endeavours 
to maintain are tlie correlatives of injurious actions, and if 
the states of consciousness which it endeavours to expel are 
the correlatives of beneficial actions, it must quickly disappear 
through persistence in the injurious and avoidance of the 
beneficial. In other words, those races of beings only can 
have survived in which, on the average, agreeable or desired 
feelings went along with activities conducive to the mainten- 
ance of life, while disagreeable and habitually-avoided feelings 
went along with activities directly or indirectly destructive of 
life, and there must ever have been, otlier things equal, the 
most numerous and long-continued survivals among races in 
which these adjustments of feelings to actions were the best, 
tending ever to bring about perfect adjustments. 

" If we except the human race and some of the highest 
allied races, in which foresight of distant consequences intro- 
duces a complicating element, it is undeniable that every 
animal habitually persists in each act which gives pleasure, 
so long as it does so, and desists from each act which gives 
pain. It is manifest that, for creatures of low intelligence, 
there can be no other "uidance." 



PLEASURES AND PAINS. 109 

Thus, then, we see that the affixing of painful or disagree- 
able states of consciousness to deleterious changes of the 
organism, and the reverse states to reverse changes, has been 
a necessary function of the survival of the fittest. We may 
further see that in bringing about this adjustment or corre- 
spondence, the zoological principle of the survival of the 
fittest must have been largely assisted by the physiological 
principle that Pleasure tends to accompany the normal 
activity of an organ and Pain to accompany its abnormal. 
For as organs are invariably of use to the organism, their 
normal activity must always be beneficial to it ; while, con- 
versely, their abnormal activity, tending to cause or being 
caused by their own disintegration, must always be harmful 
to the organism. Survival of the fittest is thus provided 
with a ready-formed condition or tendency of psycho-physio- 
logy on which to work — a tendency which survival of the 
fittest may itself in earlier times have been instrumental 
in producing ; but which, in any case, when once established 
must greatly assist survival of the fittest in apportioning the 
appropriate state of consciousness to any particular organic 
process. 

Another principle of pyscho-physiology must likewise 
have greatly assisted natural selection in its execution of 
this work. This principle is that which obtains in so-called 
acquired tastes and distastes. Thus, as Mr. Spencer observes, 
" Pleasures and Pains may be acquired — may be, as it were, 
superimposed on certain feelings which did not originally 
yield them. Smokers, snuff-takers, and those who chew 
tobacco, furnish familiar instances of the way in which long 
persistence in a sensation not originally pleasurable, makes it 
pleasurable — the sensation itself remaining unchanged. The 
like happens with various foods and drinks, which, at first 
distasteful, are afterwards relished if frequently taken. 
Common sayings about the effects of habit imply recognition 
of this truth as holding with feelings of other orders. That 
acute pain can be superinduced on feelings originally agree- 
able or indifferent, we have no proof. But we have proof 
that the state of consciousness called disgust may be made 
inseparable from a feeling that once was pleasurable:" so 
that even in the life-time of the individual the states of 
consciousness as pleasurable or painful may reverse their 
character with reference to the same organic changes or sen- 



110 MENTAL EVOLUTION IN ANIMALS. 

sations, and if this is tlie case it becomes evident with what 
plastic material natural selection has had to deal in moulding 
through numberless generations the form of consciousness 
which best fits, with reference to the welfare of the organism, 
the circumstances of stimulation. 

Thus we may well believe that survival of the fittest, 
acting always in co-operation with these principles of psycho- 
physiology, must have been successful in accomplishing the 
adjustments here assigned to its agency — the adjustments, 
that is, between states of consciousness as agreeable or dis- 
agreeable and circumstances of stimulation as beneficial or 
deleterious. And thus it is that in the process of evolution 
organisms " have gone on establishing a consensus between 
the various organs of the body, so that at last, for the most 
part, whatever will prove deleterious to any organ proves 
deleterious also to the first nerves of the organism which it 
affects," and therefore disagreeable to consciousness, although 
of course, as we should from these principles expect, this is 
only the case "when the deleterious object is found suffi- 
ciently often in the environment to give an additional point 
of advantage to any species which is so adapted as to 
discriminate and reject it."* 

Thus then, it seems to me, we have as full a rationaU of 
Pleasures and Pains as we can expect or need desire. The 
only difficulty is to understand the connection between the 
objective fact of injuriousness or the reverse, and the corre- 
sponding subjective state of consciousness ; how is it that 
injuriousness or the reverse comes to be, as it were, translated 
into the language of Pleasure and Pain. But this is only the 
old difficulty of understanding the connection of Mind with 
Body, and has no reference to historical psychology, which 
takes the fact of this connection as granted. Possibly, how- 
ever — and as a mere matter of speculation, the possibility is 
worth stating — in whatever way the inconceivable connection 
between Body and Mind came to be established, the primary 
cause of its establishment, or of the dawn of subjectivity, 

* Grant Allen, loc. cit., p. 27. Tlie latter consideration disarms any criti- 
cism which might be advanced against our doctrine on account of the agree- 
able taste of certain poisons, both to ourselves and to the lower animals. But 
it is astonishing even here how rapidly the appropriate distaste arises after 
experience of the injurious effects : witness the dislike of wine which may fre- 
quently be caused, even in those who are addicted to excess, by surreptitiously 
mixing it with nux-vomica. 



MEMORY AND ASSOCIATION OF IDEAS. Ill 

may have been this very need of inducing organisms to avoid 
the deleterious, and to seek the beneficial ; the raison d'etre 
of Consciousness may have been that of supplying the con- 
dition to the feeling of Pleasure and Pain. Be this as it may, 
however, it seems certain, as a matter of observable fact, that 
the association of Pleasure and Pain with organic states and 
processes which are respectively beneficial and deleterious to 
the organism, is the most important function of Conscious- 
ness in the scheme of Evolution. And for this reason I have 
placed the origin of Pleasures and Pains very low down in 
the scale of conscious life. Indeed, if we contemplate the 
subject, we shall find it difficult or impossible to imagine a 
form of consciousness, however dim, which does not present, 
in a correspondingly undeveloped condition, the capacity of 
preferring some of its states to others — that is, of feeling a 
distinction between quiescence and vague discomfort, which, 
with a larger accession of the mind-element, grows into the 
vivid contrast between a Pleasure and a Pain. I think, 
therefore, it is needless to say more in justification of the 
level on the diasrram at which I have written these words. 



Memory and Association of Ideas. 

It is obvious that Memory must be, and is, a faculty which 
appears very early in the development of Mind. A priori, 
this must be so, because consciousness without memory would 
be useless to the animal possessing it, and a posteriori we 
find that this is so whether we contemplate the scale of 
mental evolution in the animal kingdom or in the growing 
child. I have therefore assigned the rise of Memory to the 
level immediately succeeding that which is occupied by the 
rise of Pleasures and Pains. 

In a previous chapter* I have endeavoured to show that, 
even before the dawn of Consciousness, nervous actions of 
adjustment when frequently repeated present conclusive 
evidence that the nervous machinery concerned in them 
becomes more or less organically adapted to perform them, 
and so exhibits the objective aspect of memory. This objec- 
tive aspect I spoke of as the memory of a ganglion. Since 
that chapter was written, M. Kibot has published his excel- 

* On "the Physical Basis of Mind." 



112 MENTAL EVOLUTION IN ANIMALS. 

lent work on the " Diseases of Memory," which has now 
been translated, and forms a member of the International 
Scientific Series. In this work M. Eibot deals fnlly with the 
complete analogy that obtains on the objective side between 
ganglionic memory — or, as he calls it, organic memory — and 
the physical changes in the cerebral hemispheres which are 
concerned in true or conscious memory. I sliould like to 
express my satisfaction at finding so singularly close a corre- 
spondence between the views of M, Eibot and myself upon 
these matters, which extends into so many details that I have 
left my chapter already referred to verbatim as it was origi- 
nally written ; for it speaks in favour of the truth of one's 
results when they have been independently arrived at by 
another worker in the same field.* 

And here I may observe that I also agree with M. Eibot 
in his view that the phenomena of memory, whether 
*' organic " or " psychological," present no point of true 
analogy with any such purely physical phenomena as the 
permanent effects upon a photographic plate of a short 
exposure to light, or any other phenomena where living 
organisms are not concerned. I further agree with him in 
his view that the earliest analogy we can find to memory is 
to be sought in living tissues other than nervous, and that it 
occurs in protoplasm. Thus he quotes Hering to the effect that 
muscular fibre " becomes stronger in proportion to its use." 
To this it may, I think, be objected that there is no evidence 
of individual muscular fibres thus gaining in strength by 
use. I think a better, because a more unexceptionable, parallel 
is afforded by the fact that when a constant galvanic current 
is allowed to pass for a short time through a bundle of mus- 
cular fibres, in the direction of their length, and is then opened, 
a change is found to have been produced in the excitability 
of the fibres such that they are less excitable than before to 
a stimulus supplied by again passing the current in the 
same direction, and more excitable to the stimulus sup- 
plied by passing the current in the opposite direction. This 
memory of a muscle touching the direction in which a gal- 
vanic stimulus has passed endures for a minute or two after 
the current has ceased to pass (Frog). I have found this 

* Any one who cares to trace the correspondence may do so by comparing 
xnj chapter above alluded to with the first chapter of M. Eibot'a work. 



MEMORY AND ASSOCIATION OF IDEAS. 113 

curious fact to hold in the case of muscular tissues of various 
animals, from the Medusae upM'ards.* 

Ap;ain, I concur with M. liibot in his opinion that the 
physical basis of memory consists partly in a more or less 
permanent molecular change or " impress " produced upon 
the nervous element affected by the stimulus which is re- 
membered, and partly upon " the establishment of stable 
connections between different groups of nervous elements." 
I do not think that the view can be too strongly reprobated 
which crudely supposes that the first of these physical con- 
ditions is alone sufficient to explain all the facts of memory, 
and therefore that a given remembrance is, as it were, stored 
up in a particular cell, as a particular " impression " upon 
the substance of that cell. On the contrary, as M. Eibot 
shows, " Each of these supposed unities (memories) is com- 
posed of numberless and heterogeneous elements ; it is an 
association, a group, a fusion, a complexus, a multiplicity; 
. . . . Memory supposes not only a modification of 
nervous elements, but the formation among them of deter7ni- 
nate associations for each ^particular act. We must not, how- 
ever, forget that this is pure hypothesis — the best available 
one, no doubt, but still not to be taken as implying that we 
really know anything definitely concerning the physical sub- 
stratum of memory." 

Profound, how^ever, as our ignorance unquestionably is 
concerning the physical substratum of memory, I think we 
are at least justified in regarding this substratum as the same 
both in ganglionic or organic, and in conscious or psycholo- 
gical memory — seeing that the analogies between the two are 
so numerous and precise. Consciousness is but an adjunct 
which arises when the physical processes — owing to infre- 
quency of repetition, complexity of operation, or other causes — 
involve what I have before called ganglionic friction. And 
this view is confirmed by the large and general fact noted in 

* See " Concluding Obserrations on the Locomotor System of Medusse," 
Thil. Trans., Pt. I, 1880; and on "Modification of Excitability," &e., 
Froc. Hoy. Soc, Nos. 171 and 211. Also, Journal of Anatomy and Physio- 
logy, vol. X. Another equally good instance of what may be termed proto- 
plasmic memoi-y is to be found in the facts of the so-called " summation of 
stimuli," -which occur more or less in all excitable tissues, i.e., wherever 
living protoplasm is concerned. These facts are that if a succession of 
stimuli are applied to the excitable tissue, the latter becomes progressively 
more and more quick, as well as more and more energetic, in its response ; 
each stimulus leaves behind it an organic memory of its occiuTence. 



114 MENTAL EVOLUTION IN ANIMALS. 

our chapter on the Physical Basis of Mind, that conscious 
memory may become degraded into unconscious memory by 
repetition; associations originally mental lapsing into asso- 
ciations that are automatic. 

Thus much being premised touching the physical basis of 
memory, we may next pass on to consider the evolution of 
memory on its psychological side. 

The earliest stage of true or conscious memory may, I 
think, be regarded as consisting in the after-efi'ect produced 
upon a sensory nerve by a stimulus, which after-effect, so 
long as it endures, is continuously carried up to the sensorium. 
Such, for instance, is the case with after-images on the retina, 
the after-pain of a blow, &c.* 

The next stage of memory that it appears to me possible 
to distinguish by any definite interval from the first-named, 
is that of feeling a present sensation to be like a past sensa- 
tion. In order to do this there may be no memory of the 
sensation between the two successive occasions of its occur- 
rence, and neither need there be any association of ideas. 
Only this takes place ; when the sensation recurs the second, 
third, or fourth time, &c., it is recognized as like the sensa- 
tion when it occurred the first time — as like a sensation 
which is not unfamiliar. Thus, for example, according to 
Sigismund, who has devoted much careful attention to the 
psychogenesis of infants, it appears that the sweet taste of 
milk being remembered by newly-born infants, causes them 
to prefer sweet tastes in general to tastes of any other kind. 
This preference of course endures long after the time of 
weaning is past, and generally continues through childhood ; 
but tlie interesting point in the present connection is that it 
occurs too early in the life of the child to admit of our sup- 
posing that any association of ideas can take part in the 
process. For Sigismund says that the memory of the taste of 
milk becomes attached to the perception " immediately," 
and Preyer states, from independent observations of his own, 
that the preference shown for sweet tastes over tastes of all 
other kinds may be clearly seen as early as the first day. 

The next distinguishable stage of memory is reached 
when, still without any association of ideas, a present sensa- 
tion is perceived as unlike a past one. Thus, again turning 
to the observations of Sigismund and Preyer, it appears from 
* Compare Wundt, Qrundzlicje der philosophiseJien Fsycliologie, p. 791. 



MEMORY AND ASSOCIATION OF IDEAS. 115 

them that after the accustomed taste of milk has become well 
fastened in the memory by several successive acts of sucking, 
the child when a few days old is able to distinguish a change 
of milk. Similarly, I find among Mr. Darwin's MSS the 
following note : — 

" It is asserted (by Sir B. Brodie) that if a calf or infant 
has never been suckled by its mother, it is very much easier 
to bring it up by hand than if it has sucked only once. So 
again, Kirby and Spence state (from E^aumur, ' Entomology,' 
vol. i, p. 391) that larvae after having ' fed for a time on one 
plant will die rather than eat another, which would have 
been perfectly acceptable to them if accustomed to it from 
the first.' " 

It will be observed that in dealing with these stages of 
memory in very young infants, where as yet no association of 
ideas can either be supposed to be present or is needed to 
explain the facts, we at once encounter the question whether 
the memory is to be considered as really due to individual 
experience, or as an hereditary endowment, i.e., an instinct. 
And here it becomes apposite to refer to the old and highly 
interesting experiment of Galen, which definitely answers 
this question with reference to animals. For soon after its 
birth, and before it had ever sucked, Galen took a kid and 
placed before it a row of similar basins, filled respectively 
with milk, wine, oil, honey, and flour. The kid, after examin- 
ing the basins by smell, selected the one which was fiUed 
with milk. This unquestionably proves the fact of hereditary 
memory, or instinct, in the case of the kid ; and therefore, it 
is probable that the same, at all events in part, applies to the 
case of the child. In proof of which I may allude to the 
experiments of Professor Kuszmaul, who found that even 
prior to individual experience derived from sucking milk, 
newly-born children show a preference for sweet tastes over 
all others. For, on their tongues being wetted with sugar or 
salt solutions, vinegar, quinine, &c., the new-born infants 
made all manner of grimaces, being pleased with the sugar 
solution, but with the others showing displeasure by a " sour 
face," a " bitter face," and so on. 

But although we freely admit that the memory of milk is, 
at all events in large part, hereditary, it is none the less 
memory of a kind, and occurs without the association of ideas. 
In other words, hereditary memory, or instinct, belongs to 



116 MENTAL EVOLUTION IN ANIMALS. 

what I have marked off as the second and third stages of 
conscious memory in the largest acceptation of the term — the 
stages, that is, where, without any association of ideas, a pre- 
sent sensation is perceived as like or unlike a past one. It 
makes no essential difference whether the past sensation was 
actually experienced by the individual itself, or bequeathed 
to it, so to speak, by its ancestors. For it makes no essential 
difference whether the nervous changes which constitute the 
obverse aspect of the perceptive aptitude were occasioned 
during the life-time of the individual, or during that of the 
species and afterwards impressed by heredity on the indi- 
vidual. In either case the psychological as well as the 
physiological result is the same ; a present sensation is alike 
perceived by the individual as like or unlike a past sensation. 
It is not easy at first to grasp the truth of this statement ; 
but the source of the difficulty is in not clearly distinguish- 
ing between memory and the association of ideas. Memory 
in its lower stages which we are now considering has, in my 
opinion, nothing to do with the association of ideas. It only 
has to do with perceiving a present sensation as like or unlike 
a past sensation, which never can have formed the object of 
an idea between times, and which does not even arise as an 
ideal remembrance when the sensation again occurs. In 
other words, there is no act of conscious comparison between 
the two sensations ; there is not even any act of ideation ; 
but the past sensation has left its record in the nervous tissues 
of the animal in such wise that when it again occurs it 
emerges into consciousness as a feeling that is familiar — or if 
another unlike sensation talces its place, this emerges into 
consciousness as a feeling that is not familiar. And whether 
such feelings of familiarity or unfamiliarity arise in the 
exj^erience of the individual or in that of the species, makes, 
as I have said, no essential difference either in the pliysiolo- 
gical or in the psychological aspect of the case. 

As showing how close is tlie connection between here- 
ditary memory, or instinct, andmeniory individually acquired, 
I sliall briefly state some very interesting experiments which 
were made by Professor Preyer on newly-hatched cliickens. 
He laid before a newly-liatched chicken some cooked white 
of egg, some cooked yolk of egg, and some millet seed. The 
chick pecked at all three, but no more frequently at the two 
latter than it did at pieces of egg-shell, grains of sand, or the 



MEMORY AND ASSOCIATION OF IDEAS. 117 

spots and cracks of a wooden floor on which it was placed. 
But at the yellow yolk it pecked often and earnestly. He 
then removed all three substances, and after the lapse of an 
hour replaced them. The chick instantly recognized them all, 
as proved by its immediately beginning to devour them while 
showing a complete disregard of all other and inedible objects. 
Yet in the first experiment the chick only once tasted the 
white of egg, and only took a single millet seed. The experi- 
ment therefore shows how apt a young chicken is to learn by 
its own individual experience, while in the opinion of Pro- 
fessor Preyer the original preference shown to the yolk of 
egg proves an inherited faculty of taste-discrimination. 

These experiments serve to introduce us to the stage of 
Memory at which the Association of Ideas is first concerned — 
a principle which throughout all subsequent stages consti- 
tutes what may be termed the vital principle of Memory — 
for the chickens which first pecked at inedible objects in the 
presence of edible ones, and an hour later were able to dis- 
tinguish between the two classes of objects, must have 
established a definite association of ideas between each of the 
particular objects of its former experience with reference to 
their edible or inedible character. But it is noteworthy that, 
as these definite associations were established so quickly and 
as the result of only a single individual experience in each 
case, we can scarcely avoid concluding that heredity must 
have had a large, if not the largest, part in the process — ^just 
as in the case of distinguishing from the first the boiled yolk 
of egg, we must suppose that heredity had the exclusive 
part.* And this shows how closely the phenomena of here- 
ditary memory are related to those of individual memory ; 
at this stage in the evolution of mnemonics, where the simple 
association of ideas first occurs in very young animals, it is 
practically impossible to disentangle the effects of hereditary 
memory from those of individual. 

Association of Ideas. 
I shall reserve for my chapter on Imagination a full 

* It seems to me doubtful, however, whether heredity here had reference 
to taste-discrimination, as Preyer supposes, seeing that in nature a young 
chicken can never have had an opportunity of tasting boiled yolk of egg. 
Probably the bright yellow colour had something to do with the selection, as 
many seeds are more or less yellow in tint. 
6 



118 MENTAL EVOLUTION IN ANIMALS. 

analysis of Ideation. But in connection with Memory it is 
necessary to touch upon the Association of Ideas, and there- 
fore I shall do so now, notwithstanding the disadvantage 
which arises from considering the property that ideas pre- 
sent of becoming associated before we consider the ideas 
themselves. The truth is that here as elsewhere one labours 
under a difliculty in dealing with the faculties of Mind in the 
probable order of their evolution, from the fact that these 
faculties require to be treated separately, although they have 
not arisen separately, or in historical sequence. Therefore 
one has to meet the difficulty by occasionally forestalling in 
earlier chapters general and well-known principles, the de- 
tailed consideration of which forms the subject-matter of 
later chapters. Such a difficulty arises now, and necessitates 
a somewhat premature treatment of what I may call the 
elements of ideation. 

Throughout the present work I shall use the word Idea 
in its widest sense. As few terms have been used with a 
greater variety of meanings, I think it is better to state here 
at the outset what I take to be its most general meaning, 
and therefore the one which, as I have said, I sliall always 
attach to it. 

If after looking at a tree I close my eyes and then arouse 
a mental picture of what I have just seen, I may say indif- 
ferently that I remember or imagine the tree, or that I have 
an idea of it. The idea in this case would be simple or con- 
crete — the mere memory of a previous sensuous perception. 
Now between this and the highest product of ideation there 
is all the interval between the lowest and the highest develop- 
ment of Mind. The range of meaning over which the term 
Idea thus extends has seemed to many writers inconveniently 
large, and they have therefore imposed upon it various limi- 
tations. But as all such limitations are of a purely artificial 
kind, I shall nowhere limit the term in itself, but whenever I 
have occasion to specify one or other class of ideas, I shall do 
so by employing the convenientadjectives. Concrete, Abstract, 
and General, in the senses which I shall have to explain 
further on. Meanwhile it is enough to say that whenever 
I employ the term Idea alone, I mean it to be a generic 
term. 

We have already seen, while treating of the obverse or 
physiological side of ideation (in the chapter on the Physical 



ASSOCIATION OF IDEAS. 119 

Basis of Mind) that ideas have a strong tendency to cohere 
together in groups, so as to constitute one compound idea 
out of many simpler or more elementary ideas ; and also 
that they show no less strong a tendency to cohere together 
in concatenated series, such that the arousing of the first 
member determines the successive arousing of the other 
members. On its physiological side, as we saw, this is pre- 
cisely analogous on the one hand to the co-ordination of 
muscular movements in space (i.e., the grouping of such 
movements to form a simultaneous act, such as striking), and 
on the other hand to the co-ordination of muscular movements 
in time {i.e., the grouping of such movements to perform a 
serial act, such as vomiting). Now it is found by observa- 
tion that this cohesion of ideas is determined either by con- 
tiguity or by similarity. This fact is too well and generally 
known to call for more than a bare statement. 

Association by contiguity is more primitive than associa- 
tion by the similarity, for in order that there should be asso- 
ciation by similarity, the similarity must be perceived ; and 
this implies a higher level of mental evolution than is 
required to establish an association by contiguity — which, as 
we have seen, may be established even in non-mental nervous 
processes, while there is nothing truly analogous to associa- 
tion by similarity observable in such processes.* 

But it will be observed that even association of ideas by 
contiguity of the simplest possible kind, implies a higher 
development of the powers of memory than any of the three 
stages of memory which I have already indicated. For now 
there is not merely the memory of a past sensation (which is 
dormant till aroused by another like or unlike sensation) ; 
but there is the memory of at least two things, and also the 
memory of a previous relation of sequence between them. 

* The nearest approach to such an analogy is perhaps to he found in the 
curious fact, which I find to hold true in most persons, that if a pencil is 
taken in each hand, and while the habitual signature is heing written with 
the right hand, moving from left to right, the movements are imitated by the 
left hand moving in the opposite direction, the signature will be found to 
have been written backwards by the left hand, and even the hand-writing can 
be recognized on holding the paper before a mirror. As the left hand may 
never have performed this feat before, an,d cannot perform it unless the right 
hand is working simultaneously, the case looks Uke one of association by 
similarity. But I think it is really due to association by contiguity ; and 
the same applies to the extreme difficulty of moving the two hands simul- 
taneously as if carding wool in opposite directions. 



120 MENTAL EVOLUTION IN ANIMALS. 

This, therefore, we may mark off as another distinct stage in 
the evolution of mnemonics. 

After this stage has advanced to a considerable extent, so 
that numerous concrete and compound ideas are associated in 
a great many chains of more or less length or number of 
links, a sufficient body of psychological data has been fur- 
nished to admit of the next stage of memory being reached, 
or that of association by similarity. Professor Bain remarks : 
" The force of contiguity strings together in the mind words 
that have been uttered together ; the force of similarity brings 
forward recollections from different times and circumstances 
and connexions, and makes a new train out of many old 
ones."* And as in these higher planes of human memory, so 
in the lower ones of animal memory ; association by similarity 
implies a better development of ideation than does associa- 
tion by contiguity. 

The next and final stage of Memory is attained when 
reflection enables the mind to localize in the past the time 
when an event remembered took place. This is the stage of 
memory which is called EecoUection, and occurs in all cases 
where the mind knows that some particular association of 
ideas has previously been formed, and is therefore able deli- 
berately to search the memory until the particular association 
required is brought into the light of consciousness. 

I have now given a sketch of the successive stages in the 
evolution of Memory, drawing a line to mark off a stage 
wherever I have been able to distinguish a place where a 
line could be drawn. It is needless to say that here, as in all 
similar cases, I deem these lines to be of a purely arbitrary 
character, and introduce them only to give a general idea of 
the upward growth of a continuously developing faculty. I 
shall now conclude this chapter by briefly glancing at the 
animal kingdom and the growing child with reference to the 
evolution of Memory. 

Taking first the case of the child, I have assigned the 
seventh week as the appropriate age at which to mark the 
first evidence of memory in the association of ideas. I do so 
because I have observed that this is the age at which hand- 
fed children first recognize the feeding-bottle, i.e., an artificial 
object without smell or other quality that can arouse any 
ancestral instincts, and one which young infants always 

* Senses and InteJlect, p. 469. 



ASSOCIATION OF IDEAS. 121 

appear to recognize earlier than any other object. Locke, 
indeed, mentions recognition of the feeding-bottle as con- 
temporaneous with that of the rod; but as our ideas on 
matters of education have undergone some improvement 
since his time, this statement would now be difficult to 
verify. In my own child I observed that the power of asso- 
ciating ideas extended in the ninth week from the feeding- 
bottle to the bib, which was always and only put on before 
feeding; for as soon as this was put on the child used to 
cease to cry for the bottle. At this age, also, I observed 
that when I put her woollen shoe upon her hand she gazed 
at it intently, as if perceiving that some curious change had 
come over the habitual appearance of the hand. At ten weeks 
she knew her bottle so well that she would place the nipple 
of it in her own mouth, and, when allowed to do so, would 
hold the bottle herself while sucking. Generally, however, 
she would fail in her attempts at introducing the nipple into 
her mouth, clearly from a lack of co-ordinating power in her 
muscles — the nipple striking various parts of her face. She 
would then cry for the nurse to help. Preyer says* that at 
eight months old his child was able to classify all glass bottles 
as resembling, or belonging to the same order of objects, as a 
feeding-bottle. I may add that at seven weeks old my child 
used to cry when left alone in a silent room for a few minutes 
— a fact which also seems to show a rudimentary power of 
associating ideas, with the consequent perception of a change 
in the habitual environment. 

Turning now to the animal kingdom, the first evidence of 
memory that I have found in the psychological scale is in the 
Gasteropoda, and consists in the Limpet returning to its 
groove in the rock after having been crawling about upon a 
browsing excursion.f This fact, I think, clearly proves the 
power of remembering locality, and as such a grade of memory 
can scarcely be regarded as the earliest, we may reasonably 
suppose that the faculty really occurs still lower in the psycho- 
logical scale of animals, although we have not as yet any 
observations to prove the fact. Moreover, as Oysters learn by 
individual experience, acquired in the " Oyster-schools," to 
keep their shells closed for a much longer time than is natural 
to uneducated individuals,]: we must conclude that a dim power 

* Loc. cit., p. 42. 

t Animal IntelUgence, pp. 28-9. J Ibid., p. 25. 



122 MENTAL EVOLUTION IN ANIMALS. 

of memory is also present iu the division of the MoUusca. 
The Razor-fish, likewise, shows memory, and this in a high 
degree, inasmuch as if only once alarmed upon coming to the 
surface of its burrow, it cannot be again induced to approach 
the surface for a long time, even by the application of irri- 
tants.* Still more remarkable is the level of development to 
which memory has attained in the Snail, if the observation of 
Mr. Lonsdale is to be accepted of the Helix pomatia, which, 
after leaving its sickly mate and crawling over a garden wall, 
returned next day to the place where it had left its mate.f 
But the highest level to which the development of memory 
attains in the MoUusca is unquestionably in the Cephalopoda, 
for according to Hollmann an Octopus remembered its en- 
counter with a lobster in a remarkable manner,t while 
according to Schneider these animals learn to know their 
keepers.^ 

Seeing that memory in various stages of development thus 
unquestionably occurs among the MoUusca, I thought it worth 
while to try some experiments in this connection with the 
Echinodermata, but they all yielded negative results. It has, 
however, been alleged that if a star-fish be removed from its 
eggs, it will crawl back again to the place where they were ; 
and if this statement were confirmed, it would of course 
prove memory in the Echinodermata. Hitherto I have myself 
had no opportunity of testing it, and therefore my expe- 
riments were confined to endeavouring to teach star-fish a 
few simple lessons, which, as I have already implied, they 
would not learn. I am more surprised with my failure in 
this respect with the higher Crustacea ; for although I have 
tried similar experiments with them, I have never been able 
to teach them the simplest things. Thus, for instance, I have 
taken a hermit crab, put it into a tank filled with water, and 
when he had protruded his head from the sheU of the whelk 
in which he was residing, I gently moved towards him a pair 
of open scissors, and gave him plenty of time to see the 
glistening object. Then, slowly including the tip of one of 
his tentacles between the open blades, I suddenly cut off the 
tip. Of course the animal immediately drew back into the 
shell, and remained there for a considerable time. When he 
again came out I repeated the operation as before, and so on 

• Animal Intelligence, p. 26. f Hjid., p. 27. J Ibid., p. 30. 



ASSOCIATION OF IDEAS. 123 

for a great number of times, till all the tentacles had been 
progressively cut away little by little. Yet the animal never 
learnt to associate the appearance of the scissors with the 
effect which always followed it, and so never drew in until 
the snip had been given. ISTevertheless, that memory does 
occur among the higher Crustacea is proved by an observation 
quoted in "Animal Intelligence" (p. 233), concerning a 
lobster mounting guard upon a heap of shingle beneath which 
it had previously hidden some food. 

In another class of the Articulata, however, the faculty of 
memory has been developed to an extraordinary degree, and 
far surpasses that which has been attained by any other class 
of Invertebrata. The class of the Articulata to which I allude 
are the Insects, and, more particularly, the Hymenoptera. 
Without quoting in extenso the evidence on this head which 
has already been given in my previous work, it is enough to 
say in general terms that ants and bees are unquestionably 
able to remember the places where many months before they 
have obtained honey or sugar, &c. ; and will also, when 
occasion requires, return to nests and hives which they have 
deserted the year before. Many interesting observations have 
also been made on the rate of acquisition and the length or 
duration of particular memories in these animals, which, 
however, it is needless for me again to quote.* Perhaps the 
most interesting of these are the observations of Sir John 
Lubbock on bees gradually learning to know the difference 
between an open and a closed window, and the observations 
of Messrs. Bates and Belt on the sand- wasps carefully teach- 
ing themselves (by taking mental notes of landmarks) the 
localities to which they intend to return in order to secure 
the prey which they have temporarily concealed. Incidental 
evidence of memory in other orders of Insects will also be 
found on referring to my previous work — viz., for Beetles, 
pp. 227 — 9, for Earwigs, p. 229, and for the common House- 
fly, p. 230. 

Turning now to the Vertebrata, we find that in Fish 
memory is certainly present, although it never reaches more 
than such a degree of development as is implied by remem- 
bering in successive years the locality for spawning, learning 
to avoid baits, removing young from a nest which has been 

* For a full account of all these observations, see Animal Intelligence, 
under the heading " Memorj," of Chap. Ill and IV. 



124 MENTAL EVOLUTION IN ANIMALS. 

disturbed, and associating the sound of a bell with the arrival 
of food.* 

Batrachians and Reptiles are able to remember localities, 
and also to identify persons.f The annual migration of 
Turtles further proves the duration of memory for at least a 
year. 

In Birds the power of memory has advanced considerably 
beyond that of remembering, as in the case of the swallow, 
the precise locality of their nests from season to season, and 
even beyond that of identifying persons from year to year.J 
For the facts which I have previously detailed at length 
touching the acquisition by talking birds of tones, words, and 
phrases, show not only an exceedingly high development of 
the powers of special association, but even the power of 
genuine recollection to the extent of knowing that there is a 
missing link in the train of a previously formed association, 
and of purposely endeavouring to recover it. Quotations 
from Dr. Wilks, Mr. Venn, and Mr. Walter Pollock were also 
given, in order to show from direct and careful observation 
that the process of forming special associations is in such 
cases identical with that which occurs in man.§ 

Among Mammals the highest development of memory is 
presented by the Horse, Dog, and Elephant. Thus there is 
unexceptionable evidence of a horse remembering a road and 
a stable after an interval of eight years ;|| of a dog remem- 
bering the sound of his master's voice after an interval of five 
years,1[ and the sound of a clinking collar after an interval of 
three years ;ir and of an elephant remembering his keeper 
after having run wild for an interval of fifteen years.** It is 
probable, also, that if observations were made, the memory of 
Monkeys would be found to be very retentive, as it certainly 
is most minute, and largely assisted by the intentional efforts 
of the animals themselves. ft 

* See Animal Intelligence, pp. 248-51. t Hid-, pp. 254-C2. 

X Ibid., p. 266. § For all these facts, see ibid., pp. 266-70. 

II Ibid., p. 330. % Ibid., p. 438. ** Ibid., p. 387. 

+t Ibid., pp. 485-98. 



PERCEPTION. 125 



CHAPTER IX. 

Perception. 

At the level marked 18 I represent tlie rise from Sensa- 
tion to Perception. By this term I mean, in accordance 
with general usage, the faculty of cognition. " The contrast 
between Sensation and Perception is the contrast between 
the sensitive and the cognitive, intellectual, or knowledge- 
giving functions." (Bain.) " Perception is an establishment 
of specific relations among states of consciousness ; and this 
is distincfuished from the establishment of these states of 
consciousness themselves, ' which constitutes Sensation. 
(Spencer.) " In Perception the material of Sensation is 
acted on by the mind, which embodies in its present attitude 
all the results of its past growth." (Sully.) 

Sensation, then, does not involve any of the powers of 
the intellect as distinguished from consciousness, but Percep- 
tion implies the necessary occurrence of an intellectual or 
cognitive process, even though it be a process of the simplest 
possible kind. The term Perception, therefore, may be 
applied to all cases where a process of cognition occurs, 
whether such process arises directly or indirectly out of sen- 
sation ; thus it is equally correct to say that we perceive the 
colour or the scent of a rose, and that we perceive the truth 
or the probability of a proposition. 

Otherwise phrased we may state the distinction between 
Sensation and Perception thus. A sensation is an elementary 
or uii decomposable state of consciousness, but a perception 
involves a process of mentally interpreting the sensation in 
terms of past experience. For instance, there is a closed book 
lying on the table before me ; my eyes have been resting on 
its cover for a considerable time while I have been thinking 
how I should arrange the material of the present chapter. 
AU that time I have been receiving a visual sensation of a 



126 MENTAL EVOLUTION IN ANIMALS. 

particular kind ; but, as I did not attend to it, tlie sensation 
did not involve any element of cognition, and therefore did 
not minister to any act of perception. All at once, however, 
I became conscious that I was looking at a book, and in 
cognizing that the particular object of sensation was a book, 
I performed an act of perception. In other words, I men- 
tally interpreted the sensation in terms of past experience ; I 
made a mental synthesis of the qualities of the object, and 
assigned it to the class of objects which had previously 
produced a like sensation, 

Perception, then, is a mental classifying of sensations in 
terms of past experience, whether ancestral or individual ; it 
is sensation j;7/2ts the mental ingredient of interpretation. 
Now, as a condition to the possibility of this ingredient, it is 
clearly essential that there should be present the power of 
memory ; for only by a memory of past experience can the 
process be conducted of identifying present sensations or 
experiences as resembling past ones. Therefore in the 
diagram I have placed the dawn of Memory on the level, 
just below that at which the faculty of Perception takes its 
rise. Both Sensation and Perception are represented as 
attaining a considerable vertical elevation from base to 
apex, i.e., from their first origin to their completed evolution. 
That this ought to be so represented is evident if we reflect 
on the difference in the sensuous faculties of a medusa and 
an eagle, or between the perceptive faculties of a limpet and 
a man. It may, indeed, be thought that in my representative 
diagram I have not allowed enough for such differences, and 
therefore have made the vertical elevation of these branches 
too low. But here we must remember that in the case of Sen- 
sation, as already shown, the advance of the faculty from its 
earliest to its latest stages consists essentially, on its morpho- 
logical aspect, of a greater and greater degree of specializa- 
tion of end-organs of nerves ; and I think that the degree of 
such advance is sufficiently expressed by the vertical elevation 
which I have given to the branch in question, seeing how 
much more intricate must be the morphological development 
of the nerve-tissues which are concerned in ministering to 
the next and to all succeeding faculties. And, as regards 
Perception, we must remember that in its more highly 
elaborated phases this faculty shades off into the higher 
representative branches marked " Imagination," &c. ; so that 



PERCEPTION. 127 

the branch marked " Perception " is not intended to include 
all that might possibly be included by the term if we did not 
separately name the higher faculties to which I allude. 

Now concerning the development of Perception, I may 
here make a general remark, which is first applicable at this 
stage of mental evolution, and which continues to be appli- 
cable to the development of all the faculties which we have 
subsequently to consider. This remark is that we have ceased 
to possess any data of a morpliological kind — such as we had 
in the case of Sensation and the pre-mental faculties of 
adjustment — to guide us in our estimate of the degree of 
elaboration to which the faculty has attained. That morpho- 
logical evolution has here, as in the coarser instance of Sen- 
sation, always gone hand in hand with psychical evolution, is 
amply proved in a general way by the advancing complexity 
of the central nerve-organs ; but just because this complexity 
is so great, and the steps in morphological evolution which it 
represents so refined, we are totally at a loss to follow the 
process on its morphological side ; we are unable even dimly 
to understand the mechanisms which we see. Therefore, in 
order to estimate the ascending grades of excellence which 
these mechanisms present, we require to look to what we may 
most conveniently regard as the products of their operation ; 
we have to use the mental equivalents as indices of the mor- 
phological facts. 

We have seen that Perception is essentially a process of 
mentally interpreting Sensation in terms of past experience, 
ancestral or individual. The successive steps in the elabora- 
tion which this process undergoes in the course of its 
evolution must now be considered. 

The first stage of Perception consists merely in perceiving 
an external object as an external object, whether by the sense 
of touch, taste, smell, hearing, or sight. But confining our- 
selves, for the sake of brevity, to the sense of sight, in this 
stage Perception simply amounts to a cognition of an object 
in space, having certain space relations with other objects of 
perception, and especially with the percipient organism. 

The next stage of Perception is reached when the simplest 
qualities of an object are re-cognized as like or unlike the 
qualities presented by such an object in past experience. The 
most universal of such qualities in objects pertain to size 
form, colour, light, shade, rest, and motion ; less universally 



123 MENTAL EVOLUTION IN ANIMALS. 

sucli qualities pertain to temperature, hardness, softness, 
roughness, smoothness, and other qualities appealing to the 
sense of touch, as well as qualities appealing to the senses of 
smell, taste, and hearing. In the case of these more universal 
qualities, the part which the mind takes in the process of 
cognizing them as belonging to the objects is immediate and 
automatic, and, as Mr, Sully observes, " may be supposed to 
answer to the most constant and therefore the most deeply 
organized connections of experience." 

The third step in the advance of Perception consists in 
the mental grouping of objects with reference to their quali- 
ties, as when we associate the coolness, taste, &c., of a 
particular fruit with its size, form, and colour. Here the 
more frequently a certain class of qualities has been con- 
joined with another class in past experience, the more readily 
or automatically is the perceptive association established ; but 
in cases where the conjunction of qualities has not been so 
frequently or so constantly met with in past experience, we 
are able by reflection to recognize the perceptive association 
"as a kind of intellectual working up of the materials 
supplied us by the past." 

A further development of the perceptive faculty is re- 
quired to meet cases in which the qualities of objects have 
become too numerous or complex to be all perceived simulta- 
neously. In meeting such cases the faculty in question, 
while perceiving some of the qualities through sensation, 
supplements the immediate information so derived with 
information derived from previously formed knowledge ; the 
qualities which are not recognized immediately through sen- 
sation are inferred. Thus, in my perception of a closed book 
I have no doubt that the covers are tilled with a number of 
printed pages, although none of these pages are actually 
objects of present sensation. Or, if I hear a savage growl, I 
immediately infer the presence of an object presenting so 
complex a group of unseen qualities as are collectively com- 
prised in a dangerous dog. In a later chapter I shall have to 
dwell more minutely on tliis, which I may term the inferential 
stage of perception, and I shall therefore not deal more with 
it at present. 

It will be evident that the various stages which I have 
named in the development of Perception shade into one 
another, so as not really to be distinguishable as separate 



PEKCEPTION. 129 

stages ; they constitute rather one uniform growth on which, 
as in the case of Memory, I have arbitrarily marked these 
several grades of evolution. Moreover, it will be evident 
that the term " Perception " is really a very wide one, and 
may be said to cover the whole area of psychology, from the 
confines of an almost unfelt sensation up to the recognition 
of an obscure truth in science or philosophy. On this 
account the term has been condemned by some psychologists 
as too extensive in its application to be distinctive of any 
particular faculty; but nevertheless it is clearly impossible to 
do without it, and if we are careful to remember the sense in 
which we employ it — whether with reference to the lower or 
to the higher faculties of mind — no harm can arise from its use. 
I have just said that in the highest stage of its develop- 
ment Perception involves Inference ; and I have previously 
said that in its lowest stages it involves Memory. I must 
now point out more particularly that in its ascending stages 
Perception involves Memory of ascending stages. Thus the 
perception shown by a new-born infant of sweet tastes as 
distinguished from sour tastes and the rest, implies the 
presence of that lowest stage of memory which we have seen 
to consist in cognizing a present sensation as like a past sen- 
sation. Again, the power of discerning a change of milk 
impKes the power of cognizing a present sensation as unlike 
a past sensation. Next, when memory advances to the stage 
of associating ideas by contiguity, perception also advances 
to the stage of re- cognizing objects with their qualities and 
relations of coexistence and sequence. This in turn leads to 
the power of recognizing objects, qualities, and relations by 
similarity — the power on which we have seen the next phase 
of memory to depend. And, lastly, from tliis point onwards 
perception throughout depends exclusively upon the associa- 
tion of ideas, no matter how elaborate or refined such 
association may become. 

The fact that perception is thus everywhere and indis- 
solubly bound up with memory, is an important fact to be 
clear about ; for when memory becomes so habitual as to be 
virtually automatic or unconscious, we are apt to lose sight of 
the connection between it and perception. Thus, as Mr. 
Spencer observes, we do not speak of remembering tliat the 
sun shines ; yet we speak of perceiving that the sun shines. 
As a matter of fact, however, we do remember that the sun 



130 MENTAL EVOLUTION IN ANIMALS. 

shines, and in all the habitual phenomena of experience such 
memoiies as this become so blended with our perceptions of 
the phenomena that the memories may be said to form 
integral parts of the perceptions. Suppose, for instance, we 
see a man whose face we know, but cannot remember who 
the man is. Here the perception that the object which we 
see is a man, and not any other of the innumerable objects in 
Nature, is so intimately bound up with a well organized 
association of ideas, that we do not think of the perception 
thus far as really depending on memory. It is only when we 
turn to the incompletely organized association of ideas 
between the particular face and the particular individual, 
that we recognize the incompleteness of this part of the 
perception to depend upon the incompleteness of memory. 

Now these considerations, obvious though they appear, 
constitute the first stage in a disagreement on an important 
matter of principle, which will become more pronounced when 
I have to deal with the higher faculties of mind, and which, I 
regret to say, has reference to the writings of Mr. Spencer. In 
his chapter on Memory Mr. Spencer takes the view that, so long 
as " psychical changes are completely automatic, memory, as 
we understand it, cannot exist — there cannot exist these 
irregular psychical changes seen in the association of ideas." 
Now, I have already given my reasons for not restricting the 
term Memory to the association of ideas ; but, passing over 
this point, I cannot agree that if psychical changes (as dis- 
tinguished from physiological changes) are completely auto- 
matic, they are on this account precluded from being regarded 
as mnemonic. Because I have so often seen the sun shine, 
that my memory of it, as shining, has become automatic, I 
see no reason why my memory of this fact, simply on account 
of its perfection, should be called no-memory. And similarly 
with all those well-organized memories which constitute 
integral parts of perceptions. In so far as they involve true 
" psychological changes," and therefore imply the presence of 
conscious recocjnition as distinguished from rejlex action, so far, 
I think, no line of demarcation should be drawn between 
them and any less perfect memories. I shall recur to this 
point when I come to consider Mr. Spencer's views on 
Instinct and Eeason. ' 

Another point which we have here to consider is the part 
wliich heredity has played in forming the perceptive faculty 



PERCEPTION. 131 

of the individual prior to its own experience. We have 
already seen that heredity plays an important part in forming 
memory of ancestral experiences, and thus it is that many 
animals come into the world with their powers of perception 
already largely developed. This is shown not only by such 
cases as those of Galen's kid, and Preyer's chickens before 
mentioned, but by all the host of instincts displayed by 
newly-born or newly-hatched animals, both Vertebrate and 
Invertebrate. This subject will be fully considered when I 
come to treat of Instinct, and then it will be found that the 
wealth of ready-formed information, and therefore of ready- 
made powers of perception, with which many newly-born or 
newly-hatched animals are provided, is so great and so 
precise, that it scarcely requires to be supplemented by the 
subsequent experience of the individual. In different classes 
of animals these hereditary endowments vary much both in 
kind and in degree. Thus, with mammals as a class, heredi- 
tary perception has reference in its earliest stages to the senses 
of smell and of taste ; for while many mammals are born 
blind, some probably deaf, and all certainly very deficient in 
powers of locomotion, they invariably show more or less 
perceptive powers of taste, and very frequently well-advanced 
perceptive powers of smell. This we have already seen in 
the case of Galen's kid, and in the case of the dog (whose 
ancestors have depended so largely upon the perfection of 
smell) the same thing occurs in so high a degree, that so 
special an olfactory impression as is produced by the odour of 
a cat will cause a litter of newly-born puppies to " putt' and 
spit."* 

Birds come into the world with better endowments of 
perception than animals of any other class. For they are in 
fuU possession of every sense almost immediately after they 
are hatched, and, as we shall see later on, they are then able 
to use their senses nearly as well as they are ever able to 
use them. 

Reptiles are likewise hatched with their powers of percep- 
tion almost as highly developed as they are ever destined to 
become,t and the same as a rule is true of invertebrated 
animals. 

I must now say a few words on the physiology of Percep- 

* See p. 164. f See Animal Intelligence, pp. 256-7. 



132 MENTAL EVOLUTION IN ANIMALS 

tion — or, more correctly, on what is known touching the 
physiological processes which accompany Perception. 

In earlier chapters I have already stated that the only 
distinction which is known on the physiological side between 
a nervous activity which is accompanied by consciousness, 
and a nervous activity which is not so accompanied, consists 
in a difference of time. I shall now give the experimental 
data on which the statement rests. 

Professor Exner has determined the time which is occu- 
pied by a nerve-centre of man in executing its part in the 
performance of a reflex action. That is to say, the rate of 
transmission of a stimulus along a nerve being known, and 
the length both of the afferent and efferent nerves concerned 
in a particular reflex act being known, as also is the 
" period of latency " of a muscle ; the time occupied by the 
nerve-centre in conducting its operations was determined by 
subtracting the time occupied by the passage of the stimulus 
along the afferent and efferent nerves, plus the period of 
latency of a muscle, from the total time between the fall of 
the stimulus and the occurrence of the muscular contraction. 
This time was found in the case of the reflex closure of the 
eye-lid to vary between 0-0471 and 0'0555 of a second 
according to the strength of the stimulus.* By a similar 
process Exner has estimated the time required for the central 
nervous operations which are together comprised in having a 
simple sensation, perceiving the sensation, and the volitional 
act of signalhng the perception. That is to say, an electrical 
shock being administered to one hand, and as quicldy as 
possible signalled by the other, the time occupied by the 
nerve-centre in performing its part of the process was esti- 
mated as in the previous case. This time in the case of this 
experiment was found to be 0-0828", which is nearly twice as 
long as that which, as we have just seen, is required for a 
nerve-centre to perform its part in a reflex action.-|- 

Acts of perception in which different senses are concerned 
occupy different times. This interesting topic has been 
investigated by a number of physiologists.;!: According to 
Bonders the total "reaction-time" {i.e., between stimulus 
and response) is, roughly speaking, for touch -f, for hearing ^, 

* Arch.f. d. ffex. Physiol., xliii, 526 (1874). 

t Ibid., vii, p. 610. " 

X Sco Herumn, Eandb. d. rhjsioL, Bd. II, Th. 3, 8. 264. 



PERCEPTION. 133 

and for sight -I- of a second,* The observations of Von Wit- 
tichf, Vintschgau, and Honig-Schnied;!: show that the reaction- 
time for taste varies between 0'1598''' to 0"2351" according 
to the kind of taste ; being least for salt, more for sugar, and 
most for quinine. A constant electrical current applied to 
the tongue gives a reaction-time for the resulting gustatory 
impression of 0"167'^ I am not aware that any experiments 
have been made with regard to smell. Exner has more 
minutely determined on himself the reaction-time for touch, 
sound, and sight, with the results which are embodied in the 
following table. The signal was in all cases given by the 
right hand depressing an electrical key : — 



Direct electrical stimulation of retina 

Electrical shock on left hand 

Sudden sound 

Electric shock on forehead. . 

Electric shock on right hand 

Visual impression from electric spark 

Electric shock on toe of left foot . . 



01139" 

01276 

01360 

0-1370 

01390 

01506 

01749§ 



It is thus noticeable that although the sensation of light pro- 
duced by vision of an electric spark is much greater than 
that produced by electrical stimulation of the optic nerve, 
the interval between the stimulation and the perception is 
much longer in the former case. Seeing that the optic nerve 
is so short, this difference cannot be attributed to the time 
lost in transmission along the nerve, and must therefore be 
supposed due to the time required for the nerve-endings in 
the retina to complete all the changes (whatever they may 
be) in which their response to luminous stimulation consists. 
Thus in the case of hearing, as the above table shows, some- 
what less time is consumed in the whole act of perception 
than is consumed in the case of sight by the peripheral 
changes taking place in the retina. 

According to Helmholtz and Baxt, the more complex an 
object of visual perception is, the greater must be the dura- 
tion of its image upon the retina, in order that the perception 
may be made ; while, within certain limits, the intensity of 
the image does not affect the time required to make the per- 

* Arch.f. Anat. und Physiol., 1868, p. 657. 
t Qt. Ret. Med. (3), xxxi, p. 113. 
X Arch.f. Anat. und Phi/siol., x, p. 1. 
§ PJliiger's Archiv., Bd.VII, p. 620. 



134 MENTAL EVOLUTION IN ANIMALS. 

ception.* The last-named author found that an exposure of 
^ second is required for the perception of a row of six or 
seven letters. 

Other experiments prove that the more complex an act of 
perception, the more time is required for its performance. 
Thus Donders has shown that when an experiment in re- 
action-time is made to consist, not merely in signalling a 
perception, but in signalling one of two or more perceptions, 
the reaction-time is lengthened, owing to the greater time 
required for performing the more complex psychical process 
of distinguishing which of the expected stimuli is perceived, 
and in determining to make or to withhold the response 
accordingly. The state of matters thus presented to the mind 
is called by Donders a " Dilemma," and the following is his 
table of results : — 

Dilemma between two spots of the skin, right or left foot 
stimulated by an electric shock ; signal to be made in one 
case only 0-066" 

Dilemma of visual perceptions between two colours, sud- 
denly exhibited^ signal to be made on seeing the one but 
not on seeing the other .. .. .. .. ., 0'184 

Dilemma between two letters ; signal to be made on seeing 

one only . . . . . . . . . . . . . . 0'166 

Dilemma between five letters ; signal as before . . . . 0'170 

Dilemma of hearing ; two vowels suddenly called ; signal to 

be made on hearing one only .. .. ,. ,. 0'056 

Dilemma between five vowels ; signal as before . . . . 0'088 

The above table gives, in each case, not the whole period 
between the occurrence of the stimulus and the occurrence 
of the response, but the difference between the time required 
for this whole period when a single stimulus has to be 
answered, and when only one of two or more possible stimuli 
has to be answered. It will thus be seen that the time 
required for the act of meeting a dilemma is from ^ to J^- of 
a second longer than that which is required to signal a 
simpler perception.! 

This " Dilemma-time " has also been estimated where the 
other senses are concerned by Kries and Auerbach, with the 
following results : — $ 

* Archiv. f. d. ges. Physiol., Bd. IV, p. 329 ; Monaf.sher. d. Ber. Acad., 
June, 1871. 

t For Donders' investigations, see Archiv. f. Anat. und Fhysiol., 1868, 
pp. 657-81. 

I Archiv. f. d. ges. Physiol., 1877, pp. 293-380. 



PERCEPTION. 



13i 



Localization by sight . . . . . . 

Distinguishing colour . . 
Localization by hearing (least interval) 
Distingmshing pitch (high notes) 
Localization by touch , . 
Distinguishing pitch (low notes) 
Localization by hearing (greatest intei-val) 



0011" 

0-012 

0-015 

0019 

0-021 

0-034 

0-062 



If a greater number of alternatives are allowed by the 
preconcerted arrangement, a still longer interval is required 
for the response. 

The time required for perception in the case of all the 
senses varies with different persons, and, under the name of 
"personal equation," has to be carefully determined by 
astronomers. It is increased by old age, sundry kinds of 
sickness, and sundry kinds of drugs. But it is not neces- 
sarily less in young people full of vitality than it is in young 
people of less vigorous or lively temperaments. According 
to Exner, persons who are accustomed to allow their ideas to 
run slipshod are relatively slow in forming their perceptions, or, 
at least, have a long reaction-time between receiving and re- 
sponding to a stimulus. He gives the following table to 
show the difference in the reaction-time of seven indi- 
viduals : — * 



Age. 


Reaction-time. 


Eemarks. 


26 
23 

76 
24 
20 
22 
35 


-1337 
-3311 

0-9952 
-1751 
-2562 
1295 
0-1381 


Rough, lively labouring-man. 

Lively in movements, but rather slow^ in apprehen- 
sion. 
Infirm and not intelligent. 
Slow and deliberate in movements. 
Slow and somewhat uncertain in movements. 
Slow and very precise in movements. 
Accustomed to manual work. 



Concerning the effects of drugs it is enough to say that 
Exner found two bottles of Ehine-wine increased his reaction- 
time from 0-1904" to 0-2269" ;t and I have myself observed 
while shootiDg that an amount of alcohol not sufficient 
to produce any consciously psychical effects, is apt to make 
one shoot behind one's birds. And here, with reference 
to the personal equation, I may briefly allude to some 

• Loc. cit., p. 612. t Lot; cit., p. 628. 



136 MENTAL EVOLUTION IN ANIMALS. 

hitherto unpublished observations of my own, which has 
served to display a positively astonishing difference between 
different individuals with respect to the rate at which they 
are able to read. Of course reading implies enormously 
intricate processes of perception both of tlie sensuous and of 
the intellectual order ; but if we choose for these observa- 
tions persons who have been accustomed to read much, we 
may consider that they are all very much on a par with 
respect to the amount of practice which they have had, so 
that the differences in their rates of reading may fairly be 
attributed to real differences in their rates of forming com- 
plex perceptions in rapid succession, and not to any merely 
accidental differences arising from greater or less facility 
acquired by special practice. 

My experiments consisted in marking a brief printed 
paragraph in a book which had never been read by any of 
the persons to whom it was to be presented. The paragraph, 
which contained simple statements of simple facts, was 
marked on the margin with pencil. The book was then 
placed before the reader open, the page however being covered 
with a sheet of paper. Having pointed out to the reader 
upon this slieet of paper what part of the underlying page 
the marked paragraph occupied, I suddenly removed the 
sh6et of paper with one hand, while I started a chronograph 
with the other. Twenty seconds being allowed for reading 
the paragraph (ten lines octavo), as soon as the time was up I 
again suddenly placed the sheet of paper over the printed 
page, passed the book on to the next reader, and repeated the 
experiment as before. Meanwhile the first reader, the 
moment after the book had been removed, wrote down aU 
that he or she could remember having read. And so on with 
all the other readers. 

Now the results of a number of experiments conducted on 
this method were to show, as I have said, astonishing differ- 
ences in the maximum rate of reading which is possible to 
different individuals, all of whom have been accustomed to 
extensive reading. That is to say, the difference may amount 
to 4 to 1 ; or, otherwise stated, in a given time one indi- 
vidual may be able to read four times as much as another. 
Moreover, it appeared that there was no relationship between 
slowness of reading and power of assimilation ; on the con- 
trary, when all the efforts are directed to assimilating as 



PERCEPTION. 137 

much as possible in a given time, tlie rapid readers (as shown 
by their written notes) usually give a better account of the 
portions of the paragraph which has been compassed by the 
slow readers than the latter are able to give ; and the most 
rapid reader whom I have found is also the best at assimi- 
lating. I should further say that there is no relationship 
between rapidity of perception as thus tested and intellectual 
activity as tested by the general results of intellectual work ; 
for I have tried the experiment with several highly dis- 
tinguished men in science and literature, most of whom I 
found to be slow readers. Lastly, it is worth observing that 
every one who tries this experiment finds that it is impossi- 
ble, with any amount of effort at recollection, to remember, 
immediately after reading the paragraph, all the ideas which 
have been communicated to the mind by the paragraph. But 
as soon as the paragraph is read a second time, the forgotten 
ideas are instantly recognized as having been present to the 
mind while reading. This shows that the memory of a full 
perception may, as it were, be immediately crowded out by 
rapidly succeeding perceptions, to the extent of being 
rendered latent, although it may be instantly recalled by the 
recurrence of the same perception. 

So much, then, to show that the personal equation in 
different individuals varies the more the greater the number 
and the higher the intricacy of the perceptions which are to 
be made in a given time. I must now say a few words to 
show that the personal equation in the same individual 
admits of being greatly reduced by practice in making par- 
ticular perceptions. This is well known to astronomers so 
far as simple acts of perception are concerned, and in all the 
researches above mentioned touching the time-measurements 
of simple perceptions, the experimenters found that practice 
had the effect of reducing the reaction-time. The degree of 
reduction which might thus be produced was itself made the 
subject of experiment by Exner, who chose the old man 
already mentioned in one of tlie above quoted tables as having 
the unusually long reaction-time of 0"9952''''. After a little 
more than six months' practice at the rapid signalling of an 
electric shock, the old man's reaction-time was reduced to 
0-1866". 

This universal fact of repetition serving greatly to reduce 
the physiological time required for the performance of phy- 



138 MENTAL EVOLUTION IN ANIMALS. 

sical processes even of the simplest kind, is a fact of great 
significance. And, that the same applies to perceptions of 
the most multitudinous and complex kind, is proved in 
every-day life by the acquired rapidity with which bankers' 
clerks are able to add up figures, musicians to read a compli- 
cated score at sight, &c. But perhaps one of the best cases 
to quote in this connection is the celebrated one of the result 
of a systematic course of training to which the conjuror 
Houdin submitted his son. The training consisted in making 
the boy walk rapidly before a shop window, and perceive as 
many objects in the window as possible. After several 
months the boy was able to devour so many objects at a 
glance, that his father advertised him as " gifted with a mar- 
vellous second sight ; after his eyes have been covered with a 
thick bandage he will designate every object presented to 
him by the audience."* That is to say, the boy, before his 
eyes were bandaged, was able to perceive all the objects in 
the room which were likely to be presented to him. It is of 
interest to note that Houdin, who thus paid special attention 
to the development of rapidity of perception, observes that 
women as a rule have a greater rapidity than men, and says 
that he has known ladies who were able while seeing another 
lady " pass at full speed in a carriage, have time to analyze 
her toilette from her bonnet to her shoes, and be able to 
describe not only the fashion and quality of the stuffs, but 
also say if the lace were real or only machine made."t I 
mention this opinion of Houdin because in my own obser- 
vations on rapid reading I have been struck with the fact 
that ladies nearly always carry off the palm. 

Dr. G. Buccola has shown in a recently published essay 
that the reaction- time is, as a general rule, less among edu- 
cated than it is among uneducated persons, and greatest 
among idiots.| I may also direct attention to an interesting 
paper published a few months ago by Mr. G. Stanley Hall,§ 
" On the lengthening of the Eeaction-time under the Influence 
of Hypnotism :" the lengthening is not so considerable as 
might have been anticipated. 

I have dwelt thus at length on all the main facts which 

* Memories of Robert Houdin, vol. ii, p. 9. Professor Preyer has also 
published some observations on this snliject. f Ibid., p. 7. 

X La durata del disceraimento e dcUa detenninazione volition, Rivisti di 
Fdus. iScientlf., I, p. 2. § Mind, No. XXX. 



PERCErXION. 139 

are at present known concerning the time-relations observ- 
able in Perception, because with reference to the theory of 
the rise of consciousness, and also of the physiological side 
of mental evolution in general, these facts are of the highest 
importance. They prove by actual measurement that the 
simplest psychical actions are slow as compared with reflex 
actions, that they can be rendered more rapid by practice, 
but that they can never be brought to be so rapid as reflex 
actions. We have a further exemplification of the effects of 
practice in thus quickening the act of perception in the 
higher stages of the process. For universally the effect of 
previous acts of perception is that of placing the mind in 
readiness, as it were, for performing acts of the same kind. 
The mental attitude as regards these particular acts of per- 
ception is then the attitude of what Lewes appropriately 
called pre-perception.* When the pre-perceptive stage is 
well established, the memory, or the memory and inference 
as the case may be, arise in or together with the act of per- 
ception, so forming an integral part of the act. It is owing 
to the want of special experiences that young children are so 
slow in forming perceptions of more than the lowest degree of 
complexity ; as Mr. Spencer observes, they take a long time 
to " integrate " a strange face or other unfamiliar object ; and 
this, otherwise stated, means that their mental attitude of 
pre-perception has not yet been fully attained for such and 
such classes of objects ; the processes of memory, classifica- 
tion, and inference do not occur immediately in the act of 
perception, and therefore the full mental interpretation of the 
object perceived is only arrived at by degrees. Similarly, in 
adult life the powers of perception may be trained to a mar- 
vellous extent in special lines by practice, as we have already 
seen in the example of Houdin's son, and as we may also see 
in the fact that an " artist sees details where to other eyes 
there is a vague or confused mass." The influence of per- 
sistent attention is the most important of all influences in 
developing the rapidity and accuracy of the perceptive 
powers in which their highest excellence consists. 

We have now to consider the important question whether 

* Problems of Life and Mind, 3rd ser., p. 107. See also Dr. J. Hugh- 
lings Jackson in Brain, Nos. Ill and IV j and Mr. Sully, in Illusions, pp. 
27-30. 



140 MENTAL EVOLUTION IN ANIMALS. 

Perception arises out of Eeflex Action, Keflex Action out of 
Perception, or whether there is any genetic continuity be- 
tween the two at all. This is a most difficult question, and 
one which I do not think we are as yet entitled to answer 
with any kind of scientific confidence. 

According to Mr, Spencer the perceptive faculties arise 
out of the reflex when these attain a certain level of intricacy 
in their structure, or a certain degree of rarity in their occur- 
rence. Thus he says, " When, as a consequence of advancing 
complexity and decreasing frequency in the groups of external 
relations responded to, there arise groups of internal relations 
which are imperfectly organized and fall short of automatic 
regularity ; then, what we call Memory, becomes nascent."* 
But as a matter of fact it seems, I think, very questionable 
whether the only factors which lead to the differentiating of 
psychical nervous processes from reflex nervous processes 
are thus complexity of operation combined with infrequency 
of occurrence. For it is obvious that in ourselves certain 
truly reflex actions are of immense intricacy and of exceed- 
ingly rare occurrence — such, for example, as vomiting and 
parturition. The truth is that, so far as definite knowledge 
entitles us to say anything, the only constant physiological 
difference between a nervous process accompanied by con- 
sciousness and a nervous process not so accompanied, is that 
of time. In very many cases, no doubt, this difference may 
be caused by the intricacy or by the novelty of the nervous 
process which is accompanied by consciousness ; but, for the 
reason which I have given, I do not think we are justified in 
concluding that these are the only factors, although I have 
no doubt that they are highly important factors. For all 
that we know to the contrary, natural selection or other 
causes may have determined the physiological conditions 
necessary to the rise of consciousness (and so to the perception 
of pleasure and pain), without any question as to intricacy 
or infrequency being concerned ; in which case the time- 
relations needed to meet these conditions would have become 
evolved together with them. And I think it speaks in favour 
of some such view as this that the structure of the cerebral 
hemispheres is in some respects strikingly unlike the structure 
of the reflex centres. 

Be the factors what they may, however, it is a great 

* Pnnciplcs of Pisjcholocjy, vol. i, p. 416. 



PERCEPTION. 141 

matter to have the sure ground of experiment on which to 
rest the fact that universally psychical processes represent 
comparative delay of ganglionic action. For from this fact 
the obvious deduction is, as stated in a previous chapter, 
that psychical processes constitute the subjective expression 
of objective turmoil among molecular forces ; reflex action 
may be regarded as the rapid movement of a well-oiled 
machine, consciousness is the heat evolved by the internal 
friction of some other machine, and psychical processes as the 
light which is given out when such heat rises to redness. 
Presumably, therefore, psychical processes arise with a vivid- 
ness and intricacy proportional to the amount of ganglionic 
friction — as, indeed, appears to be experimentally proved by 
the observations of Donders before described. Now it is 
certain that by frequency of repetition, — i.e., by practice in the 
performance of any particular psychical act— the amount of 
this ganglionic friction admits of being lessened (as shown 
by the time required for the ganglionic action being reduced), 
and that concurrently with this change on the objective side 
of matters, a change takes place on the subjective, in that the 
action which was previously conscious tends to become 
automatic. 

Now from these considerations I think the inference 
would appear to be, that reflex action and perception probably 
advance together — each stage in the development of the one 
serving as the groundwork for the next stage in the develop- 
ment of the other. And in corroboration of this view is the 
general fact, that throughout the animal kingdom there is a 
pretty constant correspondence between the complexity of 
the reflex actions presented by an organism and the level of 
its psychical development. 



142 MENTAL EVOLUTION IN ANIMALS. 



CHAPTEE X. 

Imagination. 

We have already considered the psychology of Ideation to 
the extent of defining the sense in which I employ the word 
" Idea" or " Image," and also to the extent of tracing, both on 
the side of physiology and on that of psychology, the prin- 
ciple of the association of ideas.* We have now to analyze 
the psychology of Ideation somewhat more in detail. 

The simplest case of an idea is the memory of a sensa- 
tion. That a sensation may be remembered even when there 
has been no perception is proved, not only by the fact before 
mentioned that an infant only a day or two old can distin- 
guish a change of milk, but also by the fact, which must be 
familiar to all, that several minutes after an unperceived 
sensation is past, we are able by reflection to remember that 
we have had the sensation. For example, a man reading a 
book may hear a clock strike from one to five strokes (or 
perhaps more) without perceiving the sound, yet a minute or 
two afterwards he can recall the past sensation and tell the 
number of strokes which have occurred. And in simpler 
instances the memory of a sensation may extend over a much 
longer time. 

The simplest case of an idea, then, being the memory of a 
past sensation (as distinguished from the memory of a past 
perception), it follows that the earliest stages of ideation 
must be held to correspond with those earlier stages of 
memory wliich we have already described, wherein as yet 
there is no association of ideas, but merely a perception of 
a present sensation as like or unlike a past one. Hence 
in its most elementary form an idea may be said to consist 
in the faint revival of a sensation. This view has already 
been advanced with much clearness by Mr. Spencer, Professor 

* See Chap'ucx's II and III. 



IMAGINATION. 143 

Bain, and others, wno also maintain, with considerable pro- 
bability, that the cerebral change accompanying the idea of a 
past sensation is the same in kind and place, though not in 
degree of intensity, as was the cerebral change which accom- 
panied the original seasation,* 

In its next stage of development Ideation may be re- 
garded as the memory of a simple perception, and imme- 
diately after this the principle of association by contiguity 
comes in. Later on there arises association by similarity, 
and from this point onwards Ideation advances by abstrac- 
tion, generalization, and symboKc construction, in ways and 
degrees which will constitute one of the topics to be con- 
sidered in my next work. 

From this brief sketch, then, it will be seen that we have 
already considered the lowest stages of Ideation while treating 
of Memory and the Association of Ideas. Eesuming, there- 
fore, the analysis at the point where we there left it, I shall 
devote this chapter to a consideration of those higher phases 
of the idea-forming powers which we may conveniently in- 
clude under the general term Imagination. 

Kow, under this general term we include a variety of 
mental states, which although all bearing kinship to one 
another, are so diverse in the degree of mental development 
which they betoken that we must begin by analyzing them. 

As used in popular phraseology, the word Imagination is 

* Thus, Mr. Spencer says, " Tlie idea is an imperfect and feeble repetition 
of the original impression . . . There is first a presented manifestation of the 
vivid order, and then, afterwards, there may come a represented manifestation 
that is like it except in being much less distinct." (First Principles, p. 145.) 
And Professor Bain says, " What is the manner of occupation of the brain with. 
a resuscitated feeling of resistance, a smell, or a sound ? There is only one 
answer that seems admissible. The renewed feeling occupies the very same 
parts, and in the same manner, as the original feeling, and no other parts, 
nor in any other assignable manner." {Senses and Intellect, p. 338.) While 
quite assenting to this view of ideation, so far as the psychology of the sub- 
ject is concerned, I think we are much too ignorant of the physiology of 
cerebration to indulge in any such confident assertions respecting the precise 
seat and manner of the formation of ideas. Again, with reference to Mr. 
Spencer's views, it is needless to repeat the point in which I disagree with 
him touching the earliest stages of memory — or those before the advent of 
the association of ideas. Only I may point out that as the simplest possible 
idea is held to consist in a faint revival of a sensation (as distinguished from 
a perception), it follows that the occurrence of the simplest possible idea 
precedes the occurrence of its association with any other idea ; and if so, 
the memory of the sensation, or the faint revival of the sensation in which 
the idea is held to consist, must also precede any association with other faint 
revivals of the same kind, .. - - 



143: MENTAL EVOLUTION IN ANIMALS. 

taken to mean the highest development of the faculty in the 
intentional imaging of past impressions. In this sense we 
speak of the imaginations of the poet, imaginations of the 
heart, scientific use of the imagination, and so on ; in all of 
which cases we presuppose the powers of high abstraction as 
■well as those of intentional ideal combinations of former 
actual impressions. It is needless to say that even in man, 
long before the faculty in question attains to this degree of 
development, it occurs in lower degrees. Indeed, this 
highest degree may be said to bear the same relation to the 
lower degrees that recollection bears to memory ; it implies 
the introspective searching of the mind with the conscious 
purpose of forming an ideal structure. But just as recollec- 
tion is preceded by memory, or the power of intentional 
association by that of sensuous association, so is imagination 
of the intentional kind preceded by imagination of the 
sensuous. 

After considering the subject I think we may, for the 
purposes of analysis, conveniently divide the grades of 
Imagination into four classes : — 

1. On seeing any object, such as an orange, we are at 
once re-minded of the taste of an orange — have an imagina- 
tion of that taste ; and this is called up by the force of mere 
sensuous association. This is the lowest stage of mental 
imagery. 

2. Next we have the stage in which we form a mental 
picture of an absent object suggested to us by some other 
object, as when water may suggest to us the idea of wine. 

3. At a still higher stage we may form an idea indepen- 
dently of any obvious suggestion from without, as when a 
lover thinks of his mistress even in spite of external dis- 
tractions ; the course of ideation is here self -sustained, and 
no longer dependent for its mind-pictures (ideas) upon the 
suggestions of immediate sense-perceptions. At this stage 
we have dreaming in sleep, where the course of ideation run§ 
on in a continuous stream when all the channels of sense are 
closed. 

4. Lastly we have the stage of intentionally forming 
mind-pictures with the set purpose of obtaining new ideal 
combinations. 

Such being the great differences in the degrees to which 
the faculty of Imagination may attain, I have made the 



IMAGINATION. 145 

branch in the diagram which represents the faculty a very- 
long one, reaching from level 19 to level 38. The top of the 
branch therefore reaches as high as the top of Abstraction, 
about as high as two-thirds of Generalization, and beyond 
the origin of Eeflection. Of course these comparative esti- 
mates are intended here, as elsewhere, to indicate merely 
with some rough approximation to the probable truth the 
relative amount of elaboration presented by each of the 
mental species which we denominate faculties. I consider 
indeed, as I have said before, that these species are them- 
selves of an artificial or conventional character — that what 
we call faculties are abstractions of our own making rather 
than objective or independent actualities, and therefore that 
the classification of these faculties by psychologists only 
deserves in some remote sense to be regarded as a natural 
one. Still it is the best classification available for the 
purpose of comparing one grade of mental evolution witli 
another, and there can be no harm in adopting it if we 
remember, what I desire always to be remembered, that my 
representative tree is designed only to show the general 
relation between the faculties of mind as these have been 
formulated by psychologists. 

But even on this rough and general plan it may seem to 
require explanation why I represent the apex of Imagina- 
tion as attaining to the same level as the apex of Abstraction, 
for psychologists might naturally infer from my doing so 
that I am inadvertently endorsing the doctrine of Eealism. 
Such, however, is not the case. For, although it is true 
that, if we were able to imagine every abstraction, Eealism 
would become the only rational theory, I do not intend the 
diagram to favour any so absurd a notion. In my next work, 
when I shall have occasion to explain the higher branches 
of the representative tree, it will become apparent that, as I 
do not intend Abstraction to include Generalization or 
Eeflection, I am careful to keep well within the lines of 
Nominalism. 

Turning now to the lateral columns, it wiU be seen that 
1 place upon a level with the rise of imagination the classes 
MoUusca, Insecta, Arachnida, Crustacea, Cephalopoda, and 
the cold-blooded Yertebrata. My justification for assigning 
to these animals the first manifestation of tliis faculty wiU 
be found, as in other cases, in " Animal Intelligence." Thus 



146 MENTAL EVOLUTION m ANIMALS. 

the octopus which followed a lobster with which it had been 
fighting into an adjacent tank, by laboriously climbing np 
the perpendicular partition between the two tanks, must 
have been actuated "by an abiding mental image, or memory, 
of its antagonist ; the spiders which attach stones to their 
webs to hold them steady during gales must similarly be 
actuated by a faculty of Imagination ; and the same is no 
less true of the crab which, when a stone was rolled into its 
burrow, removed other stones near its margin lest they 
should roll in likewise. The limpet which returns to its 
home after a browsing excursion, must have some dim 
memory or mental image of the place. 

So much, then, for proof of Imagination of the first 
degree. Imagination of the second degree — or that wherein 
one object or set of circumstances suggests another and 
similar object or set of circumstances, occurs first, so far as 
my evidence goes, among the Hymenoptera. But here the 
cases of an association of ideas leading to the establishment 
of a mental imagery more or less remote from the immediate 
circumstances of perception are much too numerous to 
quote. I shall therefore merely refer to the headings 
" General IntelKgence " in the chapters on Ants, Bees, and 
Wasps.* Among the higher animals imagination of this 
grade is of frequent occurrence and strong force. Thus, to 
supply only one example, Thompson, in his " Passions of 
Animals " (p. 59), gives the case of a dog " which refused 
dry bread, and was in the habit of receiving from his master 
little morsels dipped in gravy of the meat remaining in the 
plate, snapped eagerly after dry bread if he saw it rubbed 
round the plate, and as, by way of experiment, this was re- 
peatedly done till its hunger was satisfied, it is evident that 
the imagination of the animal conquered for the time its 
faculties of smell and taste." 

To this order of imagination also belongs the wariness of 
wild animals. Thus Leroy, who in his capacity of Eanger 
had a large experience, says, " In the first hours of the night, 
when the countenance of darkness is in itself a fertile source 
of hope to the fox, the distant yelping of a dog will check 
him in the midst of his career. All the dangers which he 
has on various occasions passed through rise before him ; but 
at dawn this extreme timidity is overborne by the calls of 

* Animal IniclUgence, pp. 122 dO, and 181-19. 



IMAGINATION. 147 

appetite ; the animal then becomes bold by necessity. He 
even runs to meet danger, knowing [i.e., forecasting by 
imagination] that it will be redoubled by return of light." 
And again, speaking of the wolf where rendered timid by 
the hostility of man, he says that it " becomes subject to 
illusions and to false judgments, which are the fruit of the 
imagination ; and if these false judgments become extended 
to a suificient number of objects, he becomes the sport of an 
illusory system, which may lead him into infinite mistakes 
although perfectly consistent with the principles which have 
taken root in his mind. He will see snares where there are 
none; his imagination, distorted by fear, will invert the 
order of his various sensations, and thus produce deceptive 
shapes, to which he will attach an abstract notion of 
danger," &c.* 

I shall only give one other fact to prove the existence 
of Imagination of the second order in animals, but I think 
it is a good one, because showing that this faculty exists in 
this degree in an animal not having a very high grade of 
intelligence — I mean the wild rabbit. Every one who has 
ferreted wild rabbits must have noticed that if the warren has 
been ferreted before, the rabbits are very unwilling to " bolt," 
allowing themselves to be seriously injured by the ferrets 
rather than face the dangers awaiting them outside. This 
shows that the rabbits associate (owing to past experience) 
the presence of a ferret in their burrows with the presence 
of a sportsman outside them (for it does not signify how 
careful the sportsman may be to keep silent), and so vivid is 

* Intelligence of Animals, pp. 24, 120-1 (Englisli translation). The 
■well-known cunning of the fox and wolf in eluding the hounds is also evi- 
dence of a vivid imagination. In addition to the cases of this given in 
Animal Intelligence (pp. 426-30), I may now publish the following, which 
has recently been communicated to me by Dr. C M. Fenn, of San Diego : — 
" Near the south coast of San Fi-ancisco a farmer had been much annoyed by 
the loss of his chickens. His hounds had svxcceeded in capturing several of the 
marauding coyotes (a kind of small wolf), but one of the number constantly 
eluded the pursuers by making for the coast or beach, where all traces of 
him would be lost. On one occasion, therefore, the farmer divided his pack 
of hounds, and with two or three of the dogs took a position near the shore. 
The wolf soon approached the ocean with the other detachment of hounds in 
close pursuit. It was observed that as the waves receded from the shore he 
would follow them as closely as possible, and in no instance made foot-prints 
in the sand that were not quickly obUterated by the swell. When, finally, 
he had gone far enough, as he supposed, to destroy the scent, he turned 
inland." 



148 MENTAL EVOLUTION IN ANIMALS. 

the mental picture of this outside enemy, that the animal 
will for a long time suffer the immediate pain and terror at 
the teeth and claws of the ferret before venturing to expose 
itself to the more remote but still more deadly pain which it 
fears at the hands of the man. 

Coming now to Imagination of the third degree, or that 
wliich implies the power of forming ideas independently of 
any obvious suggestions from without, we have first to con- 
sider how this kind of imagination, even if present in animals, 
could be expressed. Now, apart from articulate expression 
or intelligent gesture, it is evident that the objective indices 
of imagination in this degree are so limited in number as to 
be well-nigh absent. Even, therefore, if we assume such 
imagination as present in any given animal, we might find it 
difficult to suggest the kind of action to which it might give 
rise, and which might be taken as unequivocal proof of such 
faculty. What we require, it will be observed, is some class 
or classes of actions which must be due to imagination of 
this degree and can be due to nothing else. I only know of 
three such classes, which, however, are conclusive as establish- 
ing the fact of such imagination being present in the animals 
which display them. It is almost needless to add that 
imagination, even of this level of development, may well 
be present among animals lower in the scale, which yet is not 
apparent on account of being developed in lines which do 
not express themselves in either of the three classes of 
actions on which I rely in the case of the higher animals. 

The first of these actions is Dreaming. This, wherever it 
is found to occur, constitutes certain proof of imagination 
belonging to what I have called the third degree. 

The fact that Dogs dream is proverbial, and was long ago 
remarked by Seneca and Lucretius. According to Dr. Lauder 
Lindsay the Horse also dreams, as shown by its " shuddering, 
shivering, quivering, quaking, or trembling. These phe- 
nomena are concomitants or results in the waking state of 
excitement, fear, ardour, impetuosity, or impatience. Hence 
it is quite legitimately inferred by Montaigne and others that 
the same feelings or mental conditions are developed during 
sleep and dreaming, and are likely to be associated in the 
racehorse with imaginary races, as in the sporting dog with 
imaginary coursing."* 

• Mind in the Loiver Animals, vol. ii, pp. 95-6. 



IMAGINATION. 149 

The authorities which I have been able to find who 
assert that dreaming occurs in Birds are Cuvier, Jerdon, 
Houzeau, Bechstein, Bennet, Thompson, Lindsay, and Dar- 
win.* Tliompson also says that Crocodiles dream, but as he 
gives no references to substantiate the statement, I have 
ignored it, and in the diagram placed dreaming on a level 
with Birds, as the lowest animals which I feel there is 
adequate evidence to accredit with this faculty. According 
to the writer last named, who is generally accurate, " Among 
Birds the stork, the canary, the eagle, and the parrot ; and 
among the Mammalia the elephant, the horse, and the dog, 
are incited in their dreams." Bennet noticed that water- 
birds moved their legs in their sleep, as if in the act of 
swimming ; and Hennabe heard the hyrax utter a faint cry. 
Bechstein has described dreaming in a bullfinch, and the 
dreams appeared to be of the character of nightmares, for 
" the terror begotten during sleep was such that it required 
its mistress's interference to prevent bad effects. It fre- 
quently fell from its perch, but became immediately tranquil- 
lised and reassured by the voice of its mistress." Lastly, 
Houzeau asserts that parrots sometimes talk in their sleep. "■{• 

The second class of facts on which I rely as proof of 
Imagination of the third degree in animals is that of Delu- 
sions. 

Dr. Lauder Lindsay writes with truth: — "Delusions of 
sight in animals take the form, as in man, of phantoms or 
phantasms. ... of imaginary persons, animals, or things. 
And, moreover, it would appear to be the same kind of 
spectral images that occur in other animals as in man, in 
canine rabies, for instance, as in human hydrophobia. "J On 
this subject Fleming writes : — " It (i.e., a rabid dog) appeared 
as if it was haunted by some horrid phantoms. ... At 
times it would seem to be watching the movements of some- 
thing on the floor, and would dart suddenly forward and bite 

* See, for original passages or references, Birds of India, vol. i, p. xxi ; 
Facultes-Mentales des Animaux, Sfc., tome ii, p. 183 ; Mind in the Lotcer 
Animals, vol. ii, p. 96; JPassions of Animals, p. 60; and Descent of Man, 
p. 74. 

t According to Pierguin, Guar, Elam, and Lindsay, dreaming in animals 
may be so vivid as to kad to somnambulism (see Lindsay, loc. cit., p. 97, 
et seq.). Thus Gruer asserts that "the somnambulistic watch-dog prowls in 
search of imaginary strangers or foes, and exhibits towards them a whole 
series of pantomimic actions," including barking. 

X Loc. cit., p. 103. 



150 MENTAL EVOLUTION IN ANIMALS. 

at the vacant air, as if pursuing something against which it 
had an enmity." And, indeed, this peculiarity of being 
liable to optical delusions is so usual and well marked a 
feature in rabid dogs, that it generally constitutes the earliest 
and most certain symptom of disease.* My friend Mr. Walter 
Pollock sends me the following account of a Scotch terrier 
bitch which he possessed : — " She had a curious hatred or 
horror of anything abnormal — for instance, it was long before 
she could tolerate the striking of a spring bell, which when 
I first knew her was a new experience to her. She expressed 
her dislike and seeming fear by a series of growls and barks, 
accompanied by setting her hair up on end. She used from 
time to time to go through exactly the same performance 
after gazing fixedly into what seemed to be vacancy. This 
attracted my attention, and I used to be on the look out for 
it, but carefully avoided in any way tempting her to make 
any display of this peculiarity. I simply watched her when- 
ever I was alone with her. The constant repetition in these 
circumstances of her seeming to see some enemy or portent 
unseen by me, and giving vent to her feelings in the way 
already described, led me to the conclusion that at these 
times she was the victim of optical illusion of some kind. I 
could, as I have already hinted, produce the same effect upon 
her by doing some unexpected and irrational thing, until she 
had become accustomed to this kind of experiment. But 
after this the seeing, as it seemed to be, of some sort of 
phantom remained unabated. I had no opportunity of dis- 
cerning whether the phenomena occurred at any regular 
intervals, or whether they were more frequent after sleep 
than at other times." 

Pierquin describes a female ape which had a sun-stroke, 
and afterwards use to become terror-struck by delusions of 
some kind. She also used to snap at imaginary objects, and 
" acted as if slie had been watching and catching at insects 
on the wing."t 

It seems needless for our present purpose to give more 
evidence on the fact of animals being subject to delusions, 
and so I shall pass on to the third class of facts on which I 
rely as evidence that onimals present Imagination of what I 
have called the third order. This class of facts consists of 

* See Youat, On the Dog, under Rabies. 

t Traite de la Folic des Aiiimaux, difc, tome i, y. 93, 



IMAGINATION". 151 

animals showing by their actions that they have in their 
" mind's eye " a picture or representation of absent objects. 

Every one must have observed, for instance, the greater 
spirit with which jaded horses return on their homeward 
journey, as compared w^ith the sluggishness and lack of 
energy on their out-going journey. This can only be ex- 
plained by supposing that the animals have a mental picture 
of their stables, with its ideal accompaniments of food and 
repose. Again, the desire which many animals show to 
return to their habitual haunts when removed from them can 
only be explained by supposing them to retain a mental 
picture, or imagination, of their previously happy experience. 
The promptings of this imagination are frequently so strong 
as to induce the animals to brave the dangers and fatigues of 
hundreds of miles of travel for the sole purpose of returning 
to the scenes which occupy their imaginations. " Pigeons, 
dogs, cats, and horses, when removed from their former 
homes, give repeated and daily instances of the fact. It 
crushes and overwhelms the faculties of the mind, and pros- 
trates the energies of the body. Thus many birds, when 
encaged, become so utterly spirit-broken, that they refuse all 
nourishment, pine for a few days, and die. This is particu- 
larly the case with song-birds. ... If the Howling 
Monkey is caught when full-grown, it become melancholy, 
refuses all food, and dies in a few weeks ; it is also the same 
with the Puma; and Burdach states that death sometimes 
ensues so immediately, that it can only arise from a sudden 
and violent pressure on the mind."* 

Although it may be objected to this interpretation of 
pining under confinement that the fact may be due to the 
mere absence of liberty or changed condition of life, without 
any mental and contrasted picture of previous experience, I 
think that this objection is precluded in other and analogous 
cases to which I shall next refer, and which serve in larger if 
not in full measure to disarm this criticism as applied to such 
cases as the above. I allude to all those cases so frequently 
observed among domestic animals where similar pining occurs 
without there being any change in the conditions of life, 
except the sudden withdrawal of a master or companion to 
w^hich the animal is strongly attached. I have myself 
known a case in which a terrier of my own household, on the 

* Thompson, Passions of Animals, pp. 6i-5. 



152 MENTAL EVOLUTION IN ANIMALS, 

sudden removal of his mistress, refused all food for a number 
of days, so that it was thought he must certainly die, and his 
life was only saved by forcing him to eat raw eggs. Yet all 
his surroundings remained unchanged, and every one was as 
kind to him as they always had been. And that the cause 
of his pining was wholly due to the absence of his beloved 
mistress, was proved by the fact that he remained perma- 
nently outside her bedroom door (although he knew she was 
not inside), and could only be induced to go to sleep by 
giving him a dress of hers to lie upon. No one could have 
seen this dog without being persuaded that he had a constant 
mental picture of his mistress in his imagination, and suffered 
the keenest mental anguish from her continued absence. 
Similarly there are numberless anecdotes on record, most of 
which are probably true, of dogs actually dying under such 
circumstances. 

All these facts, then, taken together — viz., dreaming, de- 
lusions, " home sickness," and pining for friends — clearly 
prove the presence among higher animals of Imagination in 
what I have called the third order. A question may here 
arise as to whether I have not in the diagram placed the rise 
of Imagination too low. I place the first origin of this 
faculty on level 19, which corresponds with that of the 
Mollusca and an infant seven weeks old. This question, like 
all others of line-drawing among the psychological faculties, 
is confessedly a difficult one ; but the reasons why I have 
placed the dawn of Imagination so low in the psychological 
scale are as follows : — 

It will be remembered that the kind of Imagination 
which we have recently been considering belongs to what I 
consider a high level of development. That is to say, I con- 
sider the power of dreaming to occupy a place about one 
third of the distance between the first dawn of the imagina- 
tive faculty and its maximum development in a Shakespeare 
or a Faraday. I so consider it because I believe that to pass 
through what I have called the first three stages, so as to 
ari'ive at the power of forming mental pictures independently 
of sensuous suggestions from without, the imaginative faculty 
has made so enormous a progress from its earliest begin- 
nings, that the rest of its development along the same 
lines is really nothing more than a function of the faculty 
of Abstraction. Superimpose upon the psychology of a 



IMAGINATION. 153 

terrier which pines for its absent mistress an elaborate 
structure of abstract ideation, and the terrier's imaginative 
faculty would begin to rival that of man. Of course it will 
be said that abstraction presupposes imagination, and so 
undoubtedly it does ; still the two are not identical, as is 
proved by the fact that for the building up of abstraction to 
any exalted height, language, or mental symbolism of some 
kind, is indispensable ; and mental symbols are so many 
artifices for the saving of imagination. 

Now if at first sight it seems absurd to accredit a moUusk 
with imagination, we must remember exactly what we mean 
by imagination in the lowest possible phase of its develop- 
ment. We mean merely the power of forming a definite 
mental picture, or of retaining a memory, no matter of how 
rudimentary a kind ; provided that the memory implies some 
dim idea of an absent object or experience, and not, as in the 
case of an infant disliking the taste of strange milk, merely 
an immediate perception of contrast between an liabitual and 
a present sensation. And that we find such a level of 
mental development as low down in the zoological scale as 
the Gasteropoda, would seem to be proved by the fact already 
alluded to of limpets returning to their homes in the rocks 
after feeding. Of course the mental image which a limpet 
forms of its home in a rock cannot be supposed to be com- 
parable in point of vividness or complexity with the mental 
image that a horse retains of its stall, or a dog of its kennel ; 
still, such as it is, it is a mental image, and therefore betokens 
imagination. More vivid, and therefore more definite, is the 
mental image that a spider forms of her lair, who when dis- 
lodged and carried away to a short distance again returns to 
her old home. (Level 20.) With a still further advance in 
the power of mental imagery (level 21) we find supplied the 
psychological conditions for the ideation of cold-blooded Ver- 
tebrata, such as the determination displayed by migratory 
Fishes (notably the salmon) to visit particular localities in 
the spawning season. On the next level (22) we reach the 
higher Crustacea, which, as we have already seen, are able to 
imagine in a high degree. Next we come to Eeptiles, con- 
cerning which I may quote the following anecdote from 
Lord Monboddo : " I am well informed of a tame serpent in 
the East Indies, which belonged to the late Dr. Vigot, once 
kept by him in the suburbs of Madras. This serpent was 



154 MENTAL EVOLUTION IN ANIMALS. 

taken by the French, when they invested Madras, in the late 
war, and was carried to Pondicherry in a close carriage. But 
from thence he found his way back again to his old quarters, 
though Madras is over one hundred miles distant from 
Pondicherry." If we substitute yards for miles, similar cases 
are on record with regard to frogs and toads — which from being 
so numerous can scarcely all be false. And that some reptiles 
have an imagination passing into what I have called the third 
stage is proved by the case of the python mentioned in "Animal 
Intelligence," which, when sent to the Zoological Gardens, 
pined for its previous master and mistress. The Cephalopoda 
and Hymenoptera have already been alluded to. Lastly, on 
the next level (25) we attain in Birds to imagination proved 
to be unquestionably of the third degree by the phenomenon 
of dreaming. . Above this level it is not of so much interest to 
trace the improvement of the faculty. Such improvement 
throughout the subsequent levels till man, probably consists 
only in a progressive advance through imagination of the 
thu-d degree — it being I think higlily improbable, and cer- 
tainly not betokened by any evidence, that imagination in 
any animal attains to what I have called the fourth degree, 
which I therefore consider distinctive of man. 

" For know that in the soul 
Are many lesser faculties that serve 
Reason as chief. Among these, Fancy next 
Her office holds. Of all external things, 
Which the five watchful senses represent, 
He forms imaginations, airy shapes ; 
Which Reason joining or disjoining, forms 
All that we affirm, or what deny, 
And call our knowledge." — Milton. 

Before taking leave of Imagination there are two branches 
of the subject which I should like briefly to consider. One 
is the opinion held by Comte that the higher animals present 
ideas of Fetishism. On this topic I cannot more briefly 
convey the material which I have to render than by quoting 
a previous publication of my own from " Nature."* " Mr, 
Herbert Spencer in his recently published work on the ' Prin- 
ciples of Sociology ' treats of the above subject. He says, 
* I believe M. Comte expressed the opinion that fetichistic 
conceptions are formed by the higher animals. Holding, as I 

* Vol. xvii, p. 168, el scq. 



IMAGINATION. 155 

have given reasons for doing, that fetichism is not original 
but derived, I cannot, of course, coincide in this view. 
Nevertheless I think the behaviour of intelligent animals 
elucidates the genesis of it. I have myself witnessed in 
dogs two illustrative cases.' One of these consisted in a 
large dog, which, while playing with a stick accidentally 
thrust one end of it against his palate, when ' giving a yelp, 
he dropped the stick, rushed to a distance from it, and 
betrayed a consternation which was particularly laughable 
m so ferocious-looking a creature. Only after cautious ap- 
proaches and much hesitation was he induced again to lay hold 
of the stick. This behaviour showed very clearly the fact that 
the stick, while displaying none but the properties he was 
familiar with, was not regarded by him as an active agent ; 
but that when it suddenly inflicted a pain in a way never 
before experienced from an inanimate object, he was led for 
a moment to class it with animate objects, and to regard it 
as capable of again doing him injury. Similarly, in the mind 
of the primitive man, knowing scarcely more of natural 
causation than a dog, the anomalous behaviour of an object 
previously classed as inanimate suggests animation. The 
idea of voluntary action is made nascent ; and there arises a 
tendency to regard the object with alarm, lest it should 
act in some other unexpected and perhaps mischievous way. 
The vague notion of animation thus aroused will obviously 
become a more definite notion, as fast as the development of 
the ghost-theory furnishes a special agency to which the 
anomalous behaviour can be ascribed.' 

" The other case observed by Mr. Spencer was that of an 
intelligent retriever. Being by her duties as a retriever led 
to associate the fetching of game with the pleasure of the 
person to whom she brought it, this had become in her mind 
an act of propitiation ; and so, ' after wagging her tail and 
grinning, she would perform this act of propitiation as nearly 
as practicable in the absence of a dead bird. Seeking about, 
she would pick up a dead leaf or other small object, and 
would bring it with renewed manifestations of friendliness. 
Some kindred state of mind it is which, I believe, prompts 
the savage to certain fetichistic observances of an anomalous 
kind.' 

" These observations remind me of several experiments I 
made some years ago on this subject, and which are perhaps 



156 MENTAL EVOLUTION IN ANIMALS. 

worth publishing. I was led to make the experiments by 
reading the instance given by Mr. Darwin in the ' Descent of 
Man' of the large dog which he observed to bark at a parasol 
as it was moved along a lawn by the wind, so presenting the 
appearance of animation. The dog on which I experimented 
was a Skye terrier — a remarkably intelligent animal, whose 
psychological faculties have already formed the subject of 
several communications to this and other periodicals. As all 
my experiments yielded the same results, I will only mention 
one. The terrier in question, like many other dogs, used to 
play with dry bones, by tossing them in the air, throwing 
them to a distance, and generally giving them the appearance 
of animation in order to give himself the ideal pleasure of 
worrying them. On one occasion, therefore, I tied a long and 
fine thread to a dry bone, and gave him the latter to play 
with. After he had tossed it about for a short time, I took 
the opportunity, when it had fallen at a distance from him 
and while he was following it up, of gently drawing it away 
from him by means of the long invisible thread. Instantly 
his whole demeanour changed. The bone which he had pre- 
viously pretended to be alive now began to look as if it 
were really alive, and his astonishment knew no bounds. He 
first approached it with nervous caution, as Mr. Spencer 
describes ; but as the slow receding motion continued, and 
he became quite certain that the movement could not be 
accounted for by any residuum of the force which he had 
himself communicated, his astonishment developed into dread, 
and he ran to conceal himself under some articles of fur- 
niture, there to behold at a distance the ' uncanny' spectacle 
of a dry bone coming to life. 

" Now in this and all my other experiments I have no 
doubt that the behaviour of the terrier arose from his seiise of 
the mysterious, for he was of a highly pugnacious disposition, 
and never hesitated to fight any animal of any size or fero- 
city ; but apparent symptoms of spontaneity in an inanimate 
object which he knew so well, gave rise to feelings of awe 
and horror, which quite enervated him. And that there was 
nothing fetichistic in these feelings may safely be concluded 
if we reflect, with Mr. Spencer, that the dog's knowledge of 
causation for all immediate purposes being quite as correct 
and no less stereotyped than is that of 'primitive man,' 
when an object of a class which he knew from uniform past 
experience to be inanimate suddenly began to move, he must 



IMAGINATION. 157 

have felt the same oppressive and alarming sense of the 
mysterious which uncultured persons feel under similar cir- 
cumstances. But further, in the case of this terrier, we are 
not left with a priori inferences alone to settle this point, for 
another experiment proved that the sense of the mysterious 
in this animal was sufficiently strong in itself to account for 
his behaviour. Taking him into a carpeted room, I blew a 
soap-bubble, and by means of a fitful draught made it inter- 
mittently glide along the floor. He became at once intensely 
interested, but seemed unable to decide whether or not the 
fitful object w^as alive. At first he was very cautious, and 
followed it only at a distance ; but as I encouraged him to 
examine the bubble more closely, he approached it with ears 
erect and tail down, evidently with much misgiving, and the 
moment it happened to move he again retreated. After a 
time, however, during which I always kept at least one bubble 
on the carpet, he began to gain more courage, and the scientific 
spirit overcoming his sense of the mysterious, he eventually 
became bold enough slowly to approach one of the bubbles, 
and nervously to touch it with his paw. The bubble, of 
course, immediately burst, and I certainly never saw astonish- 
ment more strongly depicted. On then blowing another 
bubble, I could not persuade him to approach it for a good 
while ; but at last he came, and carefully extended his paw 
as before, with the same result. But after this second trial 
nothing would induce him again to approach a bubble, and 
on pressing him he ran out of the room, which no coaxing 
would persuade him to re-enter. 

" One other example will suffice to show how strongly 
developed was the sense of the mysterious in this animal. 
When alone with him in a room I once purposely tried the 
effect on him of making a series of hideous grimaces. At 
first he thought I was only making fun ; but as I persistently 
disregarded his caresses and whining while I continued unna- 
turally to disturb my features, he became alarmed; slunk 
away under some furniture, shivering like a frightened child. 
He remained in this condition till some other member of the 
family happened to enter the room, when he emerged from 
his hiding place in great joy at seeing me again in my right 
mind. In this experiment, of course, I refrained from making 
any sounds or gesticulations, that might lead him to think I 
was angry. His actions therefore can only be explained by 
his horrified surprise at any apparently irrational behaviour. 



158 MENTAL EVOLUTION IN ANIMALS. 

i.e., by tlie violation of his ideas of uniformity in matters 
psychological. It must be added, however, that I have tried 
the same experiment on less intelligent and less sensitive 
terriers with no other effect than causing them to bark at me, 
I will only add that I believe the sense of the mysterious to 
be the cause of the dread which many animals show of 
thunder. I am led to think this, because I once had a setter 
which never heard thunder till he was eighteen months old, 
and on then hearing it I thought he was about to die of 
fright, as I have seen other animals do under various circum- 
stances. And so strong was the impression which his extreme 
terror left behind, that whenever afterwards he heard the 
boom of distant artillery practice, mistaking it for thunder, 
he became a pitiable object to look at, and, if out shooting, 
would endeavour to bury himself or bolt home. After having 
heard real thunder on two or three subsequent occasions, his 
dread of the distant cannon became greater than ever; so 
that eventually, though he keenly enjoyed sport, nothing 
would induce him to leave his kennel, lest the practice might 
begin when he was at a distance from home. But the keeper, 
Vv'ho had a large experience in the training of dogs, assured 
me if I allowed this one to be taken to tlie battery in order 
that he might learn the true cause of the thunder-like noise, 
he would again become serviceable in the field. The animal, 
however, died before the experiment was made."* 

Thus I think we may safely set down the sense of the 
mysterious as thus undoubtedly displayed by intelligent dogs 
— and also, I may add, by many horses when going along a 
dark road, hearing strange sounds, or seeing unaccustomed 
sights — to the effects of imagination in suggesting vague pos- 
sibilities in circumstances perceived to be unusual; just as 
with children under similar circumstances th^e undefined 
imagination of possible harm springing out of such circum- 
stances in some unthought-of manner, engenders that feeling 
of unreasonable dread which we may in both cases call a 
sense of the mysterious. 

* That such would have been the case, however, I have little doubt, for 
on one occasion when a number of apples were being shot out of bags upon 
th ! wooden floor of an apple-room, the sound in the house as each bag was 
shot closely resembled that of distant thxmder. The setter, therefore, became 
terribly alarmed ; but when I took him to the apple-room and showed him 
the real cause of the noise, his dread entirely left liim, and on again returniag 
to the house be listened to the riunbling with all cheerfulness. 



INSTINCT. 1C9 



CHAPTEE XL 

Instinct. 

Definition. 

1 SHALL begin this important and extensive part of my 
subject by repeating the definition of Instinct which I laid 
down in my former work. It will be remembered that for 
the sake of precision I there limited the term Instinct as 
follows : — 

" Instinct is reflex action into which there is imported 
the element of consciousness. The term is therefore a 
generic one, comprising all those faculties of mind which are 
concerned in conscious and adaptive action, antecedent to in- 
dividual experience, without necessary knowledge of the 
relation between means employed and ends attained, but 
similarly performed under similar and frequently recurring 
circumstaDces by all the individuals of the same species." 

Eeferring the reader to the context for my justification of 
this definition,* I shall here only further make this general 
statement. It follows from the above definition of Instinct, 
that a stimulus which evokes a reflex action is, at most, a 
sensation ;t but a stimulus which evokes an instinctive 
action is a perception. After what I have already said in 
Chapter IX concerning the distinction between a sensation 
and a perception, my meaning now will be clearly under- 
stood. For if a perception differs from a sensation in that it 
presents a mental element, and if an instinctive action differs 
from a reflex action in that it presents a mental element, it 
is easy to see that a stimulus supplied by a sensation is to 
a reflex action what a stimulus supplied by a perception is to 
an instinctive action ; because if a sensation could act as a 

* Animal Intelligence, pp. 10-17. 

t I say "at most," because such a stimulus may be less than a sensation, 
in that it may never cross the field of consciousness. 



160 MENTAL EVOLUTION IN ANIMALS. 

stimulus to an action apparently instinctive, ex hypotliesi tlie 
action could not be (according to my definition) really 
instinctive ; and conversely, if a perception could act as a 
stimulus to an action apparently reflex, the action could not 
be (according to my definition) a true reflex. Therefore, if 
we agree to limit the term Instinct to nervous processes 
involving a mental element, it follows that this element is 
perception, and that it is always involved in every stimulus 
leading to instinctive action. 

"With reference to general principles of classification it is 
only needful for me further to quote the following extract 
from my previous work : — 

" The most important point to observe in the first instance 
is that instinct involves mental operations; for this is the 
only point that serves to distinguish instinctive from reflex 
action. Eefiex action, as already explained, is non-mental 
neuro-muscular adaptation to appropriate stimuli; but in- 
stinctive action is this and something more ; there is in it 
the element of mind. No doubt it is often difficult, or even 
impossible, to decide whether or not a given action implies 
the presence of the mind-element — i.e., conscious as distin- 
guished from unconscious adaptation; but this is altogether 
a separate matter, and has nothing to do with the question 
of defining instinct in a manner which shall be formally 
exclusive, on the one hand of reflex action, and on the other 
of reason. As Virchow truly observes, ' it is difficult or 
impossible to draw the line between instinctive and reflex 
action ;' but at least the difficulty may be narrowed down to 
deciding in particular cases whether or not an action falls 
into this or that category of definition ; there is no reason 
why the difficulty should arise on account of any ambiguity 
of the definitions themselves. Therefore I endeavour to 
draw as sharply as possible the line which in theory should 
be taken to separate instinctive from reflex action ; and this 
line, as I have already said, is constituted by the boundary 
of non-mental or unconscious adjustment, with adjustment in 
which there is concerned consciousness or mind." 

I shall now proceed to show, by a few selected examples, 
what has been called the Perfection of Instinct; next I 
shall similarly illustrate the Imperfection of Instinct ; and 
lastly, I shall discuss the important question of the Origin 
and Development of Instinct. 



PERFECTION OF INSTINCT. IGl 

Perfection of Instinct. 

An instinct may be said to be perfect when it is perfectly 
adapted to meet those circumstances in the life of an animal 
for the meeting of which the instinct exists ; and if it is an 
instinct this perfection must be exhibited as independent of 
the animal's individual experience. We may therefore best 
illustrate the perfection of instinct by considering the won- 
derful accuracy of many among the highly refined and com- 
plex adjustments which are manifested by the newly-born 
young of the higher animals. 

The late Mr. Douglas Spalding in his brilliant researches 
on this subject has not only placed beyond question the 
falsity of the view " that all the supposed examples of instinct 
may be nothing more than cases of rapid learning, imitation, 
or instruction,"* but also proved that a young bird or mammal 
comes into the world with an amount and a nicety of 
ancestral knowledge that is highly astonishing. Thus, speak- 
ing of chickens which he liberated from the egg and hooded 
before their eyes had been able to perform any act of vision, 
he says that on removing the hood after a period varying 
from one to three days, " almost invariably they seemed a 
little stunned by the light, remained motionless for several 
minutes, and continued for some time less active than before 
they were unhooded. Their behaviour, however, was in every 
case conclusive against the theory that the perceptions of 
distance and direction by the eye are the result of experience, 
or of associations formed in the history of each individual life. 
Often at the end of two minutes they followed with their 
eyes the movements of crawling insects, turning their heads 
with all the precision of an old fowl. In from two to fifteen 
minutes they pecked at some speck or insect, showing not 
merely an instinctive perception of distance, but an original 
ability to judge, to measure distance, with something like in- 
fallible accuracy. They did not attempt to seize things 
beyond their reach, as babies are said to giasp at the moon ; 
and they may be said to have invariably hit the objects at 

* Quoted from his article in Macmillan's Magazine, February, 1873, 
from wMeh likewise all the subsequent quotations are made. We are now- 
adays so ready to assimilate scientific truth, that in reading this article — not 
yet ten years old — it seems difficult to realize that so recently there was such 
a considerable clinging of competent opinion to the non-evolutionary view of 
instinct as the quotations in the article show. 



162 MENTAL EVOLUTION IN ANIMALS. 

which they struck — they never missed by more than a hair's 
breadth, and that, too, when the specks at which they aimed 
were no bigger, and less visible, than the smallest dot of an i. 
To seize between the points of the mandibles at the very 
instant of striking seemed a more difficult operation. I have 
seen a chicken seize and swallow an insect at the first 
attempt ; most frequently, however, they struck five or six 
times, lifting once or twice before they succeeded in swallow- 
ing their first food. The unacquired power of following by 
sight was very plainly exemplified in the case of a chicken 
that, after being unhooded, sat complaining and motionless 
for six minutes, when I placed my hand on it for a few 
seconds. On removing my hand the chicken immediately 
followed it by sight backward and forward, and all round the 
table. To take, by way of example, the observations in a 
single case a little in detail : — A chicken that had been made 
the subject of experiments on hearing, was unhooded when 
nearly three days old. For six minutes it sat chirping and 
looking about it ; at the end of that time it followed with its 
head and eyes the movements of a fly twelve inches distant ; 
at ten minutes it made a peck at its own toes, and the next 
instant it made a vigorous dart at the fly, which had come 
within reach of its neck, and seized and swallowed it at the 
first stroke ; for seven minutes more it sat calling and looking 
about it, when a hive-bee coming sufficiently near was seized 
at a dart and thrown some distance, much disabled. For 
twenty minutes it sat on the spot where its eyes had been 
unveiled without attempting to walk a step. It was then 
placed on rough ground within sight and call of a hen with a 
brood of its own age. After standing chirping for about a 
minute, it started off towards the hen, displaying as keen a 
perception 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 a straight line as the nature of the ground would per- 
mit. This, let it be remembered, was the first time it had 
ever walked by sight." 

Further, " When twelve days old one of my little proteges, 
while running about beside me, gave the peculiar chirr 
whereby they announce the approach of danger. I looked 



PERFECTION OF INSTINCT. 163 

Up, and behold a sparrow-hawk was hovering at a great 
height over head. Equally striking was the effect of the 
hawk's voice when heard for the first time. 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, remained for ten minutes. Several 
times during the course of that day it again heard these 
alarming sounds, and in every instance with similar mani- 
festations of fear." 

Again referring to young chickens, Mr. Spalding con- 
tinues, — "Scores of times I have seen them attempt to 
dress their wings when only a few hours old — indeed as soon 
as they could hold up their heads, and even when denied the 
use of their eyes. The art of scraping in search of food, 
which, if anything, might be acquired by imitation — for a hen 
with chickens spends the half of her time in scratching for 
them — is nevertheless another indisputable case of instinct. 
Without any opportunities of imitation, when kept quite 
isolated from their kind, chickens began to scrape when from 
two to six days old. Generally, the condition of the ground 
was suggestive; but I have several times seen the first 
attempt, which consists of a sort of nervous dance, made on 
a smooth table." 

In this connection I may here insert an interesting obser- 
vation which has been communicated to me by Dr. Allen 
Thomson, F.R.S. He hatched out some chickens on a carpet, 
where he kept them for several days. They showed no 
inclination to scrape, because the stimulus supplied by the 
carpet to the soles of their feet was of too novel a character 
to call into action the hereditary instinct; but when 
Dr. Thomson sprinkled a little gravel on the carpet, and so 
supplied the appropriate or customary stimulus, the chickens 
immediately began their scraping movements. 

But to return to Mr. Spalding's experiments, he says : — 

"As an example of unacquired dexteiity, I may mention 
that on placing four ducklings a day old in the open air for 



164 MENTAL EVOLUTION IN ANIMALS. 

the first time, one of tliem almost immediately snapped at 
and caught a fly on the wing. More interesting, however, is 
the deliberate art of catching flies practised by the turkey. 
When not a day and a half old I observed the young turkey 
already spoken of slowly pointing its beak at flies and other 
small insects without actually pecking at tliem. In doing 
this, its head could be seen to shake like a hand that is 
attempted to be held steady by a visible effort. This I ob- 
served and recorded when I did not understand its meaning. 
For it was not until after, that I found it to be the invariable 
habit of the turkey, when it sees a fly settled on any object, 
to steal on the unwary insect with slow and measured step 
until sufficiently near, when it advances its head very slowly 
and steadily till within an inch or so of its prey, which is 
then seized by a sudden dart." 

Mr. Spalding subsequently tried similar experiments, with 
similar results, on newly born mammals. He found, for 
instance, that new-born pigs seek to suck almost immediately 
after birth. If removed twenty feet from the mother, they 
wriggle straight back to her guided apparently by her grunt- 
ing. He put a pig into a bag immediately it was born, and 
kept it in the dark till seven hours old, and then placed it 
outside the sty ten feet from its mother. It went straight to 
her, although it had to struggle for five minutes to squeeze 
under a bar. A pig blindfolded at birth went about freely, 
though tumbling against things. It had the blinder taken 
off next day, and then " went round and round as if it had 
had sight, and had suddenly lost it. In ten minutes it was 
scarcely distinguisliable from one that had had sight all 
along. When placed on a chair, it knew the height to require 
considering, went down on its knees, and leaped down. . . 
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."* 

Here I may quote an observation of my own from the 
succeeding issue of " Nature." 

" Apropos to what Mr. Spalding says about the early age 
at which the instinctive antipathy of the cat to the dog 
becomes apparent, I may state that some months ago I tried 
an experiment with rabbits and ferrets somewhat similar to 
that which he describes with cats and dogs. Into an out- 

* Nature, vol. xi, p. 507. 



PERFECTION OF INSTINCT. 165 

house wliich contained a doe rabbit with a very young family, 
I turned loose a ferret. The doe rabbit left her young ones, 
and the latter, as soon as they smelled the ferret, began to 
crawl about in so energetic a manner as to leave no doubt 
that the cause of the commotion was fear, and not merely 
the discomfort arising from the temporary absence of the 
mother."* 

With reference to the instinctive endowments of this 
kind in kittens, I may also quote the following, which I find 
among Mr. Darwin's MS S : — 

"The many cases of inborn fear or ferocity in young 
animals directed towards particular objects, as well as the 
loss of these individualized passions, seems to me extremely 
curious. Let any one who doubts their existence give a 
mouse to a kitten taken early from its mother, and which has 
never before seen one, and observe how soon the kitten 
growls with hair erect, in a manner wholly different from 
when at play or when fed with ordinary food. We cannot 
suppose that the kitten has an inborn picture of a mouse 
graven in its mind. But, as when an old hunter snorts with 
eagerness at the very first sound of the horn, we must sup- 
pose the old associations excite him almost as instantly as 
when a sudden noise makes him start, so I imagine, with the 
difference that the imagination has become hereditary instead 
of being only fixed by habit, the kitten without any definite 
anticipation trembles with excitement at the smell of the 
mouse." 

The only other observations made by Mr. Spalding which 
it is desirable to quote are those by which he proved experi- 
mentally that young birds do not require, as was ordinarily 
supposed, to be taught to fly, but fly instinctively. This fact 
was proved by keeping young swallows caged until they were 
fledged, and then allowing them to escape. When we con- 
sider the complicated muscular co-ordination required for flight, 
the fact that young birds when fledged should be able to fly 
at the first attempt constitutes another remarkable instance 
of the perfection of instinct. Of course it is true that under 
ordinary circumstances the parent birds encourage their 
progeny to fly, but the experiments in question show that 
such encouragement, or tuition, is not necessary to enable the 
young birds to practise the art. 

But it is among insects that we meet with the most re- 

* Nature, vol. xi, p. 554. 



166 MENTAL EVOLUTION IN ANIMALS. 

markable cases. Thus, to give only a few. Keaumur and 
Swanderdam assert that a young Bee, as soon as its wings are 
dry, will collect honey and construct a cell as efficiently as 
the oldest inhabitant of the hive.* Numberless insects, also, 
can never have seen their parents, and yet they perform 
instinctive actions perfectly, though it may be only once in 
their life-times — such, for instance, as the Ichneumon, which 
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.f 

A kind of insect called the Bembex conveys food to its 
young which are shut up in a cell, and it has recently been 
made the subject of some interesting experiments by M. 
Fabre. Of these the following is an epitome : — 

" The insect brings from time to time fresh food to her 
young, and it is remarkable how the Bembex remembers the 
entrance to her cell, covered as it is with sand, exactly to our 
eyes like that all round. Yet she never makes a mistake or 
loses her way. On the other hand M. Fabre found that if he 
removed the surface of the earth and the passage, thus ex- 
posing the cell and the larva, the Bembex was quite at a loss, 
and did not even recognize her own offspring. It seems as if 
she knew the doors, nursery, and the passage, but not her 
child. Another ingenious experiment of M, Fabre's was 
made with Chalicodoma. This genus is enclosed in an earthen 
cell, through which at maturity the young insect eats its way. 
M. Fabre found that if he pasted a piece of paper round the 
cell the insect had no difficulty in eating through it, but if he 
enclosed the cell in a paper case, so that there was a space 
even of only a few lines between the cell and the paper, in 
that case the paper formed an effectual prison. The instinct 
of the insect taught it to bite through one enclosure, but it 
had not wit enough to do so a second time." J 

But I think that perhaps the most remarkable instance 
of all that can be quoted from the insect world to show the 
extraordinary perfection of early-formed instincts, is one 
which is apt to be overlooked — and indeed, so far as I know, 
has been overlooked — on account of its frequency. I refer to 
the enormous body of instincts, all having reference to a 
totally different environment and habits of life, which those 
insects that undergo a complete metamorphosis present fully- 

* Kirby and Spencc, loc. cit., vol. ii, p. 470. t Ihid., i, p. 357. 

J Sir J. Lubbock, Address to Entomol. Soc, 1882. 



IMPEEFECTION OF INSTINCT. 167 

formed and ready for complete action as soon as the imago 
escapes from its pupa stage. The difference between its pre- 
vious life as a larva and its new life as an imago, is as great 
as the difference between the lives of two animals belong- 
ing to two different sub-kingdoms ; and the complete adapta- 
tion which all the new class of instincts exhibit to the 
requirements of this new life, is quite as remarkable as is the 
adaptation of the new structures to the same requirements. 

Imperfection of Instinct. 

I shall first give a few cases to show that instinct is not 
an infallible guide to action, and for tliis purpose shall choose 
aberrations of those instincts which we should expect to be 
most fixed, because of most importance to the well-being of 
the animals or their progeny — I mean the instincts of pro- 
pagation and the procuring of food. 

The flesh-fly {Musca carnaria) deposits its eggs in the 
flowers of the " carrion plant " {Stapclia hirsuta), the smell 
of wdiich resembles that of putrid meat, and so deceives the 
fly.* Similarly, the house-fly has been observed to deposit 
eggs in snufi'.f 

Again, the Eev. Mr. Bevan and Miss C. Shuttleworth, 
write me independently that they have seen wasps and bees 
visiting representations of flowers upon the wall-paper of 
rooms ; and Trevellian saw the same mistake made by the 
sphinx-moth.^ Swainson in his " Zoological Illustrations," 
gives an analogous case in a vertebrated animal ; an Austra- 
lian parrot, whose food is taken from the flowers of the 
Eucalyptus, was observed endeavouring to feed on the repre- 
sentation of flowers on a cotton-print dress. Likewise, 
Professor Moseley, E.E.S., informs me that he has noticed 
honey-seeking insects mistake for flowers the bright coloured 
salmon flies stuck in his hat while fishing ; and Mr. F. M. 
Burton, writing to " Nature " (xvii, p. 162), says that he has 
observed the humming bird hawk-moth {Macroglossa stella- 
tarum) mistake artificial flowers in a lady's bonnet for real 
ones. Still more curiously, the naturalist Couch observed a 

* E. Darwin, Zoonomia, i, § 16, art. 11. Also Kirby and Spence, loc. cit., 
ii, 469, who state the fact on the authoi-ity of Dr. Zinken. 

t Zinken, in Germar. Mag. der Ento., Bd. I, abth. 4, § 189. 
X See Houzeau, loc. cit., I, 210. 



168 MENTAL EVOLUTION IN ANIMALS. 

bee mistake a sea-anemone {Tealia crassicornis), w^iicli was 
" covered merely by a rim of M'ater," for a flower— darting 
into the centre of the disk, " and though it struggled a good 
deal to get free, was retained till it was drowned, and was 
then swallowed.* The fact, alluded to by Mr. Darwin in the 
Appendix, that the workers of the humble-bee attempt to 
devour the eggs laid by their own queen, appears to constitute 
a remarkable case of imperfect instinct. Again, Huber saw a 
bee begin a cell in a wrong direction, and other bees tear it 
to pieces. Bees have also been observed to collect rye-flower 
when damp instead of pollen.f " Pollen-getting, according to 
Gebien, is the weak point in the character of bees ; " for this 
author observes (p. 74) that they " lay up useless hoards of it, 
which they go on augmenting every year, and this is the only 
point on which they can be accused of want of prudence." 

Mr. Darwin's MS notes contain a brief record of a 
number of observations on ants {F. rufa) carrying pupa 
skins, with a great and apparently useless expenditure of 
labour, far away from the nest, and even up trees. He tried 
taking away the skins from some of the carriers, and replacing 
them near the nest ; the first ants that happened to fall in 
with them again carried them off. This, as the notes 
observe, appears to be a case of " blundering instinct ; " and 
the same epithet may be applied to mistakes made by the 
harvesting ants observed by Mr. Moggridge, which carefully 
stored in their granaries the gall- apples of a small species of 
Cynips, clearly imagining that they were nuts; and also, 
under a similar delusion, stored small beads which Mog- 
gridge, in order to test their instinct, scattered in their 
harvesting fields.^ 

Among Birds we find mistaken instinct exhibited by the 
cuckoo when it lays two eggs in the same nest, with the 
inevitable result that one of the young birds will afterwards 
eject the other. In the same category we may place the 
promiscuous dropping of her eggs on the part of the rhea ; 
small birds frequently mistaking a larger and unfamiliar bird 
for a hawk, as shown by their mobbing it ; and numberless 
special cases could be given of mistaken instinct iu the 
matter of nest-building — in the selection of unsuitable sites, 
unsuitable materials, and so on. 

* Critic, March 24, 1860. t Cottage Gardener, April, 1860, p. 48. 
X Rarvesting Ants and Trap-door Spiders, p. 37, et seq. 



IMPERFECTION OF INSTINCT. 169 

Among Mammals it must be deemed a mistaken instinct 
■which leads the Norwegian lemming to swim out to sea in its 
migrations, and perish by millions in consequence. Under 
existing circumstances it is an imperfect instinct which leads 
the quadrupeds in South Africa, mentioned by Mr. Darwin in 
the Appendix, to migrate, seeing that by so doing they expose 
themselves to persecution. The shrewmouse, also mentioned 
by Mr. Darwin in the Appendix, which " continually betrays 
itself by screaming out when approached," is another, and 
perhaps a better instance. The instincts of rabbits with 
regard to the attacks of weasels appear to me to be imperfect, 
or not completely formed. For, as I observe in "Animal 
Intelligence " (p. 359), I have witnessed the mode of capture 
practised by weasels in the open field, and it consists merely 
in the rabbit " toddling along, with the weasel toddling 
behind, until tamely allowing itself to be overtaken . . . 
There seems to have been here a remarkable failure of natural 
selection in doing duty to the instincts of these swift-footed 
animals " — a failure, however, which time would doubtless 
remedy, if weasels were sufficiently numerous in relation to 
the breeding power of the rabbit to give natural selection the 
opportunity of perfecting the instinct of escaiDe from this 
particular enemy. 

Many other instances of the imperfection of instinct 
might be quoted, but enough have now been given to render 
unquestionable the only point with which we are concerned, 
viz., that although well established instincts are, as a rule, 
adjusted with astonishing nicety to certain definite and 
frequently recurring circumstances, the adjustment is made 
only with reference to these, so that a very small variation in 
them is sufficient to lead the instinct astray. It is also of 
interest here to note what seems to be a complementary truth, 
viz., that small variations taking place in the organism itself 
when not in normal converse with its environment, are suffi- 
cient to throw the delicate mechanism of instinct out of gear 
when this is afterwards brought into such converse. This fact, 
for instance, is familiar enough in the case of tamed animals 
(which when agaiu " turned down " in their native haunts 
are not at first at home in them), but is brought out in a much 
more striking manner by the experiments of Mr. Spalding. 
Thus he says : — 

"Before passing to the theory of instinct, it may be 



170 MENTAL EVOLUTION IN ANIMALS. 

worthy of remark that, unlooked for, I met with in the 
course of experiments some very suggestive, hut not yet 
sufficiently observed, phenomena ; which, however, have led 
me to the opinion that not only do the animals learn, but they 
can also forget — and very soon — that which they never 
practised. Further, it would seem that any early interference 
with the established course of their lives may completely 
derange their mental constitution, and give rise to an order of 
manifestations, perhaps totally and unaccountably different 
from what would have appeared under normal conditions. 
Hence I am inclined to think that students of animal 
psychology should endeavour to observe the unfolding of the 
powers of their subjects in as nearly as possible the ordinary 
circumstances of their lives. And perhaps it may be because 
they have not all been sufficiently on their guard in this 
matter, that some experiments have seemed to tell against the 
reality of instinct. Without attempting to prove the above 
propositions, one or two facts may be mentioned. Untaught, 
the new-born babe can suck — a reflex action ; and Mr. Her- 
bert Spencer describes all instinct as 'compound reflex 
action ; ' but it seems to be well known that if spoon-fed, and 
not put to the breast, it soon loses the power of drawing milk. 
Similarly, a chicken that has not heard the call of the mother 
until eight or ten days old then hears it as if it heard it not. 
I regret to find that on this point my notes are not so full as 
I could wish, or as they might have been. There is, however, 
an account of one chicken that could not be returned to the 
mother when (? until) ten days old. The hen followed it, and 
tried to entice it in every way ; still it continually left her and 
ran to the house or to any person of whom it caught sight. 
This it persisted in doing, though beaten back with a small 
branch dozens of times, and indeed cruelly maltreated. It was 
also placed under the mother at night, but it again left her in 
the morning. Something more curious, and of a different 
kind, came to light in the case of three chickens that I kept 
hooded until nearly four days old — a longer time than any I 
have yet spoken of Each of these on being unhooded 
evinced the greatest terror of me, dashing off in the opposite 
direction whenever I sought to approach it. The table on 
which they were unhooded stood before a window, and each 
in its turn beat against the glass like a wild bird. One of 
them darted behind some books, and, squeezing itself into a 



IMPEKFECTION OF INSTINCT. 171 

corner, remained cowering for a length of time. We might 
guess at the meaning of this strange and exceptional wild- 
ness; but the odd fact is enough for my present purpose. 
Whatever might have been the meaning of this marked change 
in their mental constitution — had they been unhooded on the 
previous day they would have run to me instead of from me 
— it could not have been the effect of experience ; it must 
have resulted wholly from changes in their own organiza- 
tion." 

Subsequently Mr. Spalding tried the experiment of 
keeping young ducklings away from the water for several 
days after they were hatched ; on then bringing them to a 
pond they showed as much dislike to the water as young 
chickens would have done. (See Lewes, article Instinct, 
" Problems of Life and Mind.") 

The change produced in the instincts of male animals by 
castration may also be mentioned in the present connection, 
and particularly the tendency which is thus induced among 
cock birds to adopt the incubating and other habits of the 
hen. I quote the following from a recently published article 
by Dr. J. W. Stroud of Port Elizabeth, who has devoted a 
good deal of attention to the subject of caponizing : — 

" Aristotle, more than two thousand years ago, tells us of 
a cock that performed all the duties of a hen. (' Hist. An. 
Lib.' ix, 42.) Pliny, too, speaks of the motherly care bestowed 
by a cock on chickens. * He did everything for them,' says 
he, ' like to the very hen that hatched them, and ceased to 
crow.' (' Pliny Trans.' i, 299.) Albertus Magnus witnessed 
the same thing ; and iElian (' Hist.' iv, 29) mentions a cock 
which on the death of the hen while hatching, took to the 
eggs, sat on them, and brought out chicks.' Says Willoughby 
(in ' Pay's Willoughby 's Natural History '), ' We have beheld 
more than once, not without pleasure and admiration, a Capon 
bringing up a brood of chickens, like a hen clucking over them, 
feeding them, and brooding them under his wings with as 
much care and tenderness as their dams are wont to do.' 
* Once accustomed to this ofl&ce,' says Baptista Rosa (' Magi a 
Naturalis' iv, 26), 'a Capon will never abandon it, but when 
one brood is grown up another batch of newly hatched 
chickens may be put to him and he will be as kind to them 
and take as much care of them as of the first, and so in 
succession.' Keaumur (' Art de Paire Eclore.' torn, ii, p. 8) 



172 MENTAL EVOLUTION IN ANIMALS. 

bears testimony to similar facts and also to the propensity 
of Capons to sit. (See also ' Cottage Gardener/ 1860, 
p. 379."*) 

In this connection I may also quote the following in- 
stance, which I find recorded among Mr. Darwin's MS 
notes : — 

" April, 1862. We had a kitten which sucked its mother, 

and, when a month old, taken to and sucked another 

cat ; then to and sucked two other cats, and then its 

instinct was confounded, and became mixed with reason or 
experience : for it tried repeatedly to suck three or four other 
Idttens of its own age, which no one, as far as I am aware, 
ever saw any other kitten do. Thus born instinct may be 
modified by experience." 

In his " Naturgeschichte der Saugethiere von Paraguay," 
p. 201, Dr. Eeugger gives the following curious instance of 
interference with natural instincts brought about by changed 
conditions of individual life. Speaking of a kind of Cat, 
native in Paraguay, he says that there is no instance on 
record of the animal breeding when in captivity, and that on 
one occasion a female having been pregnant when captured 
and kept in confinement by Herr Nozeda, brought forth her 
young, but immediately afterwards devoured them. This, 
which took place in her own country, shows that even so 
well rooted an instinct as the maternal may be greatly 
altered in the individual by even a few months of change in 
the conditions of life. Similar facts in the case of the 
domestic Sow, pet Mice, and other animals exposed to the 
influence of domestication are, of course, very common. 

It is needless, I think, to give further instances to prove 
the general principle that derangement of instinctive organi- 
zation is apt to arise when an animal ceases to be in normal 
converse with its environment. But I may here adduce a 
curious instance of the derangement of the instinctive 
organization in an animal which was apparently in all 
respects in normal converse with its environment, and this to 
such an extent that it may properly be regarded as a case of 
insanity. But although perhaps pathological in nature, it is 
none the less available as showing the imperfection of in- 
stinct — the only difference between it and the cases previously 

* Ostronization, or the Caponizing of the OHrich ''S. Breutnall, Port 
Elizabeth, 1883). 



IMPERFECTION OF INSTINCT. 173 

cited consisting in the changing causes being internal instead 
of external. The case was communicated to me by a lady, 
who, from its peculiar nature, desires me to withhold her 
name ; but I quote the account in her own words : — 

" A white fantail pigeon lived with his family in a pigeon- 
house in our stable-yard. He and his wife had been brought 
originally from Sussex, and had lived, respected and admired, 
to see their children of the third generation, when he sud- 
denly became the victim of the infatuation I am about to 
describe. 

" No eccentricity whatever was remarked in his conduct 
until one day I chanced to pick up somewhere in the garden 
a ginger-beer bottle of the ordinary brown stone description. 
I flung it into the yard, where it fell immediately below the 
pigeon-house. That instant down flew paterfamilias, and to 
my no small astonishment commenced a series of genuflexions, 
evidently doing homage to the bottle. He strutted round and 
round it, bowing and scraping and cooing and performing the 
most ludicrous antics I ever beheld on the part of an ena- 
moured pigeon. . . . Nor did he cease these perform- 
ances until we removed the bottle ; and, which proved that this 
singular aberration of instinct had become a fixed delusion, 
whenever the bottle was thrown or placed in the yard — no 
matter whether it lay horizontally or was placed upright — 
the same ridiculous scene was enacted ; at that moment the 
pigeon came flying down v/ith quite as great alacrity as when 
his peas were thrown out for his dinner, to continue his 
antics as long as the bottle remained there. Sometimes this 
would go on for hours, the other members of his family treat- 
ing his movements with the most contemptuous indifference, 
and taking no notice whatever of the bottle. At last it 
became the regular amusement with which we entertained 
our visitors to see this erratic pigeon making love to the 
interesting object of his affections, and it was an entertain- 
ment which never failed, throughout that summer at least. 
Before next summer came round he was no more." 

It is thus evident that the pigeon was affected with some 
strong and persistent monomania with regard to this particular 
object. Although it is well known that insanity is not an 
uncommon thing among animals, this is the only case I have 
met with of a conspicuous derangement of the instinctive 
as distinguished from the rational faculties — unless, indeed, 



174 MENTAL EVOLUTION IN ANIMALS. 

•we so regard the exhibitions of erotomania, infanticidal mania, 
&c., which occur in animals perhaps more frequently than 
they do in man. 

But with reference to the imperfection of instinct, we 
have now some more important matters to consider than the 
mere enumeration of cases in which instinct may have been 
observed at fault. Let it first be observed that under the 
general heading " Imperfection of Instinct," we may include 
two very different classes of phenomena ; for instincts may 
be imperfect because they have not yet been completely 
developed, or they may appear to be imperfect because not 
completely answering to some change in those circumstances 
of life with reference to which they have been fully developed, 
Now, if instincts have been developed at all, it is obvious 
that they must have passed through various stages of imper- 
fection before they attained to perfection, and therefore we 
might expect to meet with some cases of instinct not yet per- 
fected — cases, be it observed, which differ from those already 
mentioned, in that their faultiness arises, not from a novelty 
of experience with reference to which the instinct has not 
been developed, but from the fact of the instinct not being 
yet fully formed ; and this ought more especially to be the 
case with instincts the perfection of which is not of vital 
importance to the species ; for such instincts would not have 
been so rigorously trained or perfected by natural selection. 
A good illustration on this head seems to be afforded by the 
instinct of destroying the drones as exhibited by the hive-bee. 
Thus, to quote from " Animal Intelligence " :— " Evidently 
the object of this massacre is that of getting rid of useless 
mouths ; but there is the more difficult question as to why 
these useless mouths ever came into existence. It has been 
suggested that the enormous disproportion between the pre- 
sent number of males and the single fertile female, refers to 
a time before the social instincts became so complex or con- 
solidated, and when, therefore, bees lived in lesser communi- 
ties. Probably this is the explanation, although I think we 
might still have expected that before this period in their 
evolution had arrived bees might have developed a compen- 
sating instinct, either not to allow the queen to lay so many 
drone eggs, or else to massacre the drones while still in the 
larval state. We must remember, also, that among the wasps 



IMPERFECTION OF INSTINCT. 175 

the males do work (chiefly domestic work, for which they are 
fed by their foraging sisters) ; so it is possible that in the 
hive-bee the drones were originally useful members of the 
community, and that they have lost their primitively useful 
instincts. But whatever the explanation, it is very curious 
that here, among the animals which are justly regarded as 
exhibiting the highest perfection of instinct, we meet with 
perhaps the most flagrant instance in the animal kingdom of 
instinct unperfected. It is the more remarkable that the 
drone-killing instinct should not have been better developed 
in the direction of killing the drones at the most profitable 
time — namely, in their larval or oval state — from the fact 
that in many respects it seems to have been developed to a 
high degree of discriminative refinement." 

And, to take only one other illustration, Mr. Spalding 
writes : — 

" Another suggestive class of phenomena that fell under 
my notice may be described as imperfect instincts. When a 
week old my turkey came on a bee right in its path — the 
first, I believe, it had ever seen. It gave the danger chirr, 
stood for a few seconds with outstretched neck and marked 
expression of fear, then turned off in another direction. On 
this hint I made a vast number of experiments with chickens 
and bees. In the great majority of instances the chickens 
gave evidence of instinctive fear of these sting-bearing insects ; 
but the results were not uniform, and perhaps the most 
accurate general statement I can give is, that they were un- 
certain, shy, and suspicious. Of course to be stung once was 
enough to confirm their misgivings for ever. Pretty much in 
the same way did they avoid ants, especially when swarming 
in great numbers." 

Similarly, and during the life-time of the individual, 
Mr. Spalding found an instinct in the course of development 
in the case already quoted of the turkeys catching flies. And 
precisely analogous facts may be noticed in the developing 
instincts of the child. Thus, for instance, the balancing of 
the head in an upright position may be said in man to be 
instinctive, for the power of doing so is first acquired about 
the tenth week, by constantly recurring eflbrts, and eventually 
becomes independent of intentional thought. Preyer describes 
the stages by which the latter, or completed, stage is reached 
through numberless gradations, the passage of which occupies 



176 MENTAL EVOLUTION IN ANIMALS. 

about six weeks.* He sa5''s that the child first accidentally 
finds the comfort of the attitude, and so adopts it more and 
more constantly until through habit it becomes instinctive. 
He also gives exactly parallel facts in the case of learning to ■ 
creep, sit, stand, walk, &c.t 

Among animals in a state of nature we may, I think, 
regard all instincts which, so far as we can see, are trivial or 
useless, as instincts which are imperfect, in that they do not 
answer to any apparent needs in the animals' present condi- 
tions of life. Such instincts are not very numerous, and, as 
Mr. Darwin observes in the Appendix, they may be quoted 
as objections to his theory of the development of instinct by 
natural selection. I shall subsequently consider this diffi- 
culty, but here I have only to note the fact that instincts of 
this apparently purposeless kind occur, and that, qud pur- 
poseless, they are imperfect. Such, for instance, is the 
instinct of a hen cackling when she has laid an egg, the cock- 
pheasant crowing when going to roost, cattle and elephants 
goring their sick or wounded companions, sundry instincts 
connected with excrements — such as burying them in earth, 
always depositing them in the same place, &c. — and other 
cases mentioned by Mr. Darwin in the Appendix. 

But the most important class of considerations for us is 
one to which the foregoing may be said to lead up. We 
have seen that if instincts have been developed by evolution, 
we should expect to find cases in which they are in process 
of evolution, or not yet perfect ; and we have also seen that 
this expectation is realized. Now in so far as instinct requires 
to be mixed with intelligence in order to be effective, it is as an 
instinct imperfect ; it is as an instinct in course of formation, 
or at any rate not perfectly adapted to the possible circum- 
stances of life. Therefore all cases of the education of 
instinct by intelligence — whether in the individual or the 
race — fall to be considered in the present connection. The 
consideration of this subject, however, lands us directly in 
a larger and deeper topic as to the origin and development of 
instinct in general. To this topic, therefore, we shall next 
address ourselves. 

* Die Seele clcs Kmdes, Leipzig, 1882, pp. 166-7. 
t ^f^^<^-> I'P- 107-75. 



OKIGIN AND DEVELOPMENT OF INSTINCTS. 177 



CHAPTER XII. 

Instinct (contimced). 

Origin and Development of Instincts. 

Instincts probably owe their origin and development to one 
or other of two principles. 

I. The first mode of origin " consists in natural selection, 
or survival of the fittest, continuously preserving actions 
which, although never intelligent, yet happen to have been of 
benefit to the animals which first chanced to perform them. 
Thus, for instance, take the instinct of incubation. It is 
quite impossible that any animal can ever have kept its eggs 
warm with the intelligent purpose of hatching out their con- 
tents, so we can only suppose that the incubating instinct 
began by warm-blooded animals showing that kind of atten- 
tion to their eggs which we find to be frequently shown by 
cold-blooded animals. Thus crabs and spiders carry about 
their eggs for the purpose of protecting them; and if, as 
animals gradually became warm-blooded, some species, for 
this or foT any other purpose, adopted a similar habit, the 
imparting of heat would have become incidental to the car- 
rying about of the eggs. Consequently, as the imparting of 
heat promoted the process of hatching, those individuals 
which most constantly 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."* 

II. The second mode of origin is as follows : — By the 
effects of habit in successive generations, actions which were 
originally intelligent become, as it were, stereotyped into per- 

* Quoted from my own article ou "Instinct," in tlie Encyclopaedia Bri- 

tannica. 



178 MENTAL EVOLUTION IN ANIMALS. 

manent instincts. Just as in the life-time of the individual 
adjustive actions which were originally intelligent may by 
frequent repetition become automatic, so in the life-time of 
the species actions originally intelligent may, by frequent 
repetition and heredity, so write their effects on the nervous 
sj'^stem that the latter is prepared, even before individual 
experience, to perform adjustive actions mechanically which 
in previous generations were performed intelligently. This 
mode of origin of instincts has been appropriately called the 
" lapsing of intelligence."* 

For the sake of subsequent reference, I shall allude to 
instincts which arise by way of natural selection, without the 
intervention of intelligence, as Primary Instincts, and to 
those which are formed by the lapsing of intelligence as 
Secondary Instincts. 

Let us now consider the reasons which cb priori lead us to 
assign the probable origin of instincts to these principles. 
Taking first the case of primary instincts, these reasons may 
be briefly rendered thus : — 

(1.) Many instinctive actions are performed by animals 
too low in the scale to admit of our supposing that the adjust- 
ments which are now instinctive can ever have been intel- 
ligent. (2.) Among the higher animals instinctive actions 
are performed at an age before intelligence, or power of 
learning by individual experience, has begun to assert itself. 
(3.) Considering the great importance of instincts to species, 
we are prepared to expect that they must be in large part 
subject to the influence of natural selection. As Mr. Darwin 
observes, " it will be universally admitted that instincts are 
as important as corporeal structures for the welfare of each 
species under its present conditions of life. Under changed 
conditions of life it is at least possible that slight modifica- 
tions of instinct might be profitable to a species ; and if it 
can be shown that instincts do vary ever so little, tlien I can 
see no difficulty in natural selection preserving and con- 
tinually accumulating variations of instinct to any extent 
that was profitable." 

That instincts may arise by way of lapsed intelligence is 
rendered probable a priori by all the facts which show the 
resemblance between instincts and intelligent habits. To 
take only a few of these facts for the present purpose, I 

* By Lewes, see Problems of Life and Mind. 



ORIGIN AND DEVELOPMENT OF INSTINCTS. 179 

cannot do better than confine myself to making a quotation 
from Mr. Darwin's MSS ; for this will show how deep-seated 
and detailed is the resemblance between habit and instinct. 

" In repeating anything by heart, or in playing a time, 
every one feels that, if interrupted, it is easy to back a little, 
but very difficult suddenly to resume the thread of thought 
or action a few steps in advance. Now P. Huber has described 
a caterpillar which makes by a succession of processes a very 
complicated hammock for its metamorphosis; and he found 
that if he took a caterpillar which had completed its ham- 
mock up to, say the sixth stage of construction, and put it 
into a hammock completed up only to the third stage, the 
caterpillar did not seem puzzled, but repeated the fourth, 
fifth, and sixth stages of construction. If, however, a cater- 
pillar was taken out of a hammock made up, for instance, to 
the third stage, and put into one finished to the ninth stage, 
so that much of its work was done for it, far from feeling 
the benefit of this, it was much embarrassed, and even 
forced to go over the already finished work, starting from the 
third stage which it had left off before it could complete its 
hammock. So, again, the hive-bee in the construction of its 
comb seems compelled to follow an invariable order of work. 
M. Fabre gives another curious instance how one instinctive 
action invariably follows another. A Sphex makes a burrow, 
flies away and seeks for prey, which it brings, paralyzed by 
having been stung, to the mouth of its burrow ; but always 
enters to see that all is right within before dragging in its 
prey; whilst the Sphex was within its burrow, M. Fabre 
removed the prey to a short distance ; when the Sphex came 
out it soon found the prey and brought it again to the mouth 
of the burrow ; but then came the instinctive necessity of 
reconnoitering the just reconnoitered burrow ; and as often 
as M. Fabre removed the prey, so often was all this gone 
over again, so that the unfortunate Sphex reconnoitered its 
burrow forty times successively ! When M. Fabre altogether 
removed the prey, the Sphex, instead of searching for fresh 
prey and then making use of its completed burrow, felt itself 
under the necessity of following the rhythm of its instinct, 
and before making a new burrow, completely closed up the 
old one as if it were all right, although in fact utterly useless 
as containing no prey for its larva.* 

* Anns, des Sci. Nat, 4 ser., tome vi, p. 148. With respect to Bees, see 



180 MENTAL EVOLUTIOX IN ANIMALS. 

" In another way we perhaps see tlie relation of habit and 
instinct, namely in the latter acquiring great force if practised 
only once or twice for a short time ; thus it is asserted that 
if a calf or infant has never sucked its mother, it is very much 
easier to bring it up by hand than if it has sucked only 
once.* So again Kirbyf states that larva, after having ' fed 
for a time on one plant, will die rather than eat another, 
which would have been perfectly acceptable to them if ac- 
customed to it from the first.' " 

Such, then, are some of the a priori reasons for believing 
that instincts must have arisen from one or other of these 
two sources — natural selection or lapsing intelligence ; it now 
remains to prove, a posteriori, that they have so arisen. I 
may first give a brief sketch of how this proof ought to 
proceed. 

The proof, then, that instincts have had a primary mode 
of origin requires to show : — 

I. That non-intelligent habits of a non-adaptive character 

occur in individuals. 

II. That such habits may be inherited. 

III. That such habits may vary. 

IV. That when they vary the variations may be inherited. 

V. That if such variations are inherited, we are justified 
in assuming, in view of all that we know concerning 
the analogous case of structures, that they may be fixed 
and intensified in beneficial lines by natural selection. 

The proof that instincts have had a secondary mode of 
origin requires to show : — 

VI. That intelligent adjustments when frequently per- 
formed by the individual become automatic, either to 
the extent of not requiring conscious thought at all, 
or, as consciously adjustive habits, not requiring the 
same degree of conscious effort as at first. 

VII. That automatic actions and conscious habits may 
be inherited. 

Primary Instincts. 

Proceeding, then, to consider these sundry heads of proof, 
it is easy to establish Proposition I, inasmuch as the fact 

Kirby and Spence, Entomology, toI. i, p. 497. For tlio hammock caterpillar, 
Bee Mem. Hoc. Pliys. de Oenbve, tome vii, p. 154. 

* Zoonomia, p. 140. t Intro, to Entomol., vol. i, p. 391. 



ORIGIN AND DEVELOPMENT OF INSTINCTS. 181 

which it states is a matter of daily observation. " Tricks of 
manner," indeed, are of such frequent occurrence in the 
nursery and schoolroom, that it usually entails no small 
labour on the part of elders to eradicate them, and when not 
eradicated in childhood they are apt to continue through 
life, imless afterwards conquered by the efforts of the indi- 
vidual himself. But in cases where the trick of manner is 
not obnoxious, or sufficiently unusual to call for checking, it 
is allowed to persist, and thus it is that almost every one 
presents certain slight peculiarities of movement which we 
recognize as characteristic* 

Such peculiarities of movement as we meet with them in 
ordinary life are slightly marked ; but their significance in 
relation to instinct has been obtruded on my notice by 
observing them in the much more striking form in which 
they are presented by idiots. This is a class of persons 
which, as we shall find in my next work, is of peculiar 
interest in relation to mental evolution, because in them we 
have a human mind arrested in its development as well as 
deflected in its growth — therefore in many cases supplying to 
the comparative psychologist very suggestive material for 
study. Now one of the things which must most strike any 
one on first visiting an idiot asylum, is the extraordinary 
character and variety of the meaningless tricks of manner 
which are everywhere being displayed around him. These 
tricks, often ludicrous, sometimes painful, but usually 
meaningless, are always individual and v,^onderfully per- 
sistent. Generally speaking, the lower the idiot in the scale 
of idiotcy, the more pronounced is this peculiarity ; so that if 
one sees a patient moving to and fro continually, or otherwise 
exhibiting " rliythmical movements," one may be pretty sure 
that the case is a bad one. But even among the higher idiots 
and " feeble-minded," strange and habitual movements of the 
hands, limbs, or features are exceedingly common. 

Among animals similar facts are to be noticed. Scarcely 
any two sporting dogs " point " in exactly the same manner, 

* Dr. Carpenter says {Menial Physiology, p. 373), " Wliat particular 
' trick ' each individual may learn, depends very much upon accident. Thus, 
in the old times of dependent watch-chains and massive bunches of seals, 
these were the readiest playthings," &c. In view of the relation which such 
"tricks" bear to the formation of primary instincts, this remark has some 
importance ; it shows that even aimless movements may be determined and 
rendered habitual by the conditions of the environment. 



182 MENTAL EVOLUTION IN ANIMALS. 

altliougli every dog adheres to his particular attitude through 
life. Nearly all domestic animals exhibit slight but indi- 
vidually constant differences of movement w^hen caressed, 
when they are threatened, when at play, &c. But perhaps a 
more striking view of this subject may be obtained by con- 
sidering the sum of the neuro-muscular conditions, leading to 
individual peculiarities of movement, which we comprise 
under the term " disposition," or, if more prominent, " idiosyn- 
cracy." Thus many dogs develop the meaningless habit — 
which has all the strength of an incipient instinct, and in 
the case of the collie breed, as we shall subsequently see, 
inherited or innate — of barking round a carriage. Some cats 
take to " mousing " with avidity, while others can never be 
taught to care about the sport. All who keep pet birds — 
and indeed domestic animals of any kind — must have 
noticed the diversity of their dispositions in respect of play, 
boldness, amiability, &c. ; and Mr. W. Kidd, who had a very 
large experience, is sure that the diversity of disposition in 
larks and canaries is displayed by nestlings reared from the 
nest.* 

Almost innumerable instances might be given of indi- 
vidual variations in the instincts of nest-building.f Even as 

* See Gardener' s Chronicle, 1851, p. 181, whicli is referred to in this 
connection in Mr. Darwin's MSS. 

+ For example, the Nut-hate li usually builds in the hollow branch of a tree, 
plastering up the opening with clay ; but Mr. Hewetson found a pair which 
for many years occupied a hole in a wall {YarreVs Birds), and Mr. Bond 
desci'ibes another nest placed in the side of a hay-stack, built up with a mass 
of clay weighing no less than eleven pounds, and the nest measuring thirteen 
inches in height {Zoologist, 2nd ser., p. 2850). The golden-crested Wren, also, 
frequently exhibits variations in the structure and situation of its nest {Hist. 
Brit. Birds, 4th ed., vol. i, p. 450). The Golden Eagle builds in precipitous 
crags of rock ; but Mr. D. E. Knox {Antumns on the Spey, 1872, pp. 141-3), 
describes a nest which he himself examined on a fir-tree, not above twenty 
feet from the ground. Couch says that " more than one pair of birds will 
Bometimes unite in occupying one nest, and either rear their broods in com- 
mon, or one of them will surrender the future care of them to the other {Illus- 
trations of Instinct, p. 233). Mr. S. Stone, writing of the Missel-thrush says, 
" From what has been written, it appears plain that some individuals use clay or 
plaster in the construction of the nest, while others contrive to do without it, 
which agrees with my own observation, for although I have found nests 
wliich did not contain plaster, the greater part of those which have fallen in 
my way — and they have been not a few — certainly have had a plastering of 
some kind between the twigs and lichens outside and the fine grasses which 
invariably constitute the lining ; this lias been more especially the case when 
th 6 bird has select-ed as a site the horizontal branches of a tree {Field, Jan. 8, 
1861. This is a clipping which I find among Mr. Darwin's MS notes). As 



OEIGIN AND DEVELOPMENT OF INSTINCTS. 183 

low down in the psychological scale as the insects, we are not 
without evidence of individual variations of instinct. Thus, 
for instance, Forel observed great diversities of building 
among the F. truncicola — the nests being sometimes domed, 
sometimes made under stones, and sometimes excavated in 
the wood of old trees. Likewise, Eiichner observes, " one 
ant will let herself be killed rather than let go the pupa 
which she holds, while another will let them fall and run 
away like a coward," and similar statements are made by 
Moggridge. 

But as showing strongly marked individual differences of 
disposition in animals, and also that such differences may 
lead to useless or capricious actions having all the strength 
of incipient instincts, I think a good class of cases to select 
are those in which one animal conceives a strong though 
senseless attachment to another animal of a different species. 
Thus, for instance, I once found a wounded widgeon on the 
shore, and took it home to my poultry yard. After a time 
its wounds healed, and I then cut its wings to keep it as a 
pet. The bird soon became perfectly tame, and then con- 
ceived a strong, persistent, and unremitting attachment to a 
peacock which also belonged to the establishment. Wherever 
the peacock went the widgeon followed like a shadow, so 
that during the day time the one bird was never seen without 
the other being in close attendance. If a separation were 
forcibly effected, the distress of the v/idgeon was very great, 
and she would whistle incessantly till restored to her old 
place waddling behind the tail of the peacock. This devoted 
attachment was the more remarkable from the fact that it 
was not in the smallest degree reciprocated by the peacock. 
He never paid the slightest heed to his constant companion, 
nor, indeed, did he seem to notice that she was always just 
behind him. At night he used to roost upon the gable of a 
cottage. The poor widgeon could not fly to accompany him, 
and even if she could would probably not have been able to 
sit upon the gable ; but she always kept as near him as cir- 
cumstances would permit, for as soon as he flew up to his 
gable she would squat herself down upon the ground just 

observed in the text, sucli instaneea might be multiplied indefinitely ; but as 
a considerable number of additional and well selected cases are given in 
Mr. Darwin's essay at the end of this book, it is needless for me to adduce 
any further illustrations. 



184 MENTAL EVOLUTION IN ANIMALS. 

"below it — a devotion which eventually cost her her life, as 
she thus fell a prey to a prowling cat. Now here we have a 
curious case of a bird that had been wild, taking a violent 
fancy for the wholly useless companionship of another and 
very dissimilar bird ; for it should be added that she chose 
the peacock as the object of her persistent regard out of a 
large number of other kinds of domestic birds which lived 
about the place. 

Similarly, cats often like to associate with horses, and in 
some cases with dogs, birds, rats, and other unlikely creatures. 
Dogs not unfrequently make friendships with a variety of 
animals, and in a case recorded by F. Cuvier a terrier found 
so much delight in the companionship of a caged lion, that 
when the lion died the dog pined away and died also. 
Thompson gives cases in which horses have become " ex- 
tremely attached to dogs and to cats, and seemed pleased to 
have them placed on their backs in their stalls."* Eengger 
mentions a monkey which was so fond of a dog that it cried 
with grief during the absence of its friend, caressed it on its 
return, and assisted it in all its quarrels with other dogs. 
" A peccari in the menagerie at Paris formed a strong attach- 
ment with one of the keeper's dogs, and a seal in the same 
place allowed a little water-dog to play with it and to take 
fish from its mouth, which it always resented if this were 
attempted by the other seals in the same tank. Dogs have 
lived on terms of friendship with gulls and ravens .... 
and a rat has been known to accompany his master in his 
walks," &c., &c.t 

Colonel Montagu, in the Supplement to his "Ornitho- 
logical Dictionary," p. 165, relates the following singular 
instance of an attachment which took place between a 
Chinese goose and a pointer, " The dog had killed the male 
bird, and had been most severely punished for the mis- 
demeanour, and finally the dead body of his victim was tied 
to his neck. The solitary goose became extremely distressed 
for the loss of her partner and only companion ; and probably 
having been attracted to the dog's kennel by the sight of her 
dead mate, she seemed determined to persecute the dog by 
her constant attendance and continual vociferations ; but 
after a little time a strict friendship took place between these 
incongruous animals. They fed out of the same trough, lived 

* Thompson, Passions of Animals, pp. 360-1, f H'*-^' 



ORIGIN AND DEVELOPMENT OF INSTINCTS. 185 

tinder the same roof, and in the same straw bed kept each 
other warm ; and when the dog was taken to the field, the 
lamentations of the goose were incessant." 

The same author gives cases of attachment between a 
pigeon and a fowl, a terrier and a hedgehog, a horse and a 
pig, a horse and a hen, a cat and a mouse, a fox and harriers, 
an alligator and a cat, &c., all as having fallen under his own 
observation. {Ibid., p. 162.) 

It is not impossible that the so-called " domestic pets " 
which are kept by many species of ants* may really be use- 
less adjuncts to the hive, capricious love of association having 
perhaps in these ants become by inherited habit truly 
instinctive. This, at any rate, must be the explanation of the 
fact that birds of different species will, even in a state of 
nature, occasionally associate, as is the case with Guinea- 
fowls and partridges, and, according to Yarrell, with par- 
tridges and landrails. Such unusual cases among birds in a 
state of nature are of special interest, because they may then 
properly be regarded as the beginnings of such a firmly set 
and truly instinctive association as that which obtains 
between rooks and starlings, &c.t 

Enough lias now been said in support of Proposition I, 
viz., that non-intelligent habits of a non-adaptive character 
occur in individuals. We shall next proceed to Proposition II, 
viz., that such habits may be inherited. 

That this is the case with tricks of manner in man is a 
matter to be observed in almost every family, and was long 
ago pointed out by John Hunter, Mr. Darwin in his MSS 
gives a case which he himself observed, " and can vouch for 
its perfect accuracy." " A child who as early as between her 
fourth and fifth year, when her imagination was pleasantly 
excited, and at no other time, had a most peculiar trick of 
rapidly moving her fingers laterally with her hands placed 
on the side of her face; and her father had precisely the 

* See Animal Intelligence, pp. 83-4. 

t Prof. Newton, F.R.S., informs me tliat " bands of tlie Grolden-crested 
Wren may frequently be observed in winter consorting with bands of the 
Coal-Titmouse, and in a less degree with those of the Long-tailed Titmouse ; 
"while parties of Redpoles and Siskins will for a time join their company, or vice 
versa. The flocking together of Rooks and Daws is, of course, an everyday 
occurrence, as is also for some months the association of Starlings with them, 
and in many cases the combination of all with Lapwings. 



186 MENTAL EVOLUTION IN ANIMALS. 

same trick under the same frame of mind, and which was 
not quite conquered even in old age : in this instance there 
could not possibly have been any imitation."* 

That the more frequent and more pronounced tricks of 
manner which are manifested by idiots are likewise inherited 
is highly probable ; but I have no evidence on this point, as 
idiots in civilized countries are not allowed to propagate. 

In the case of animals, however, the evidence is abun- 
dant. Thus, again to quote from Mr. Darwin's MSS, " the 
Piev. W. Darwin Fox tells me that he had a Skye terrier 
bitch which when begging rapidly moved her paws in a way 
very different from that of any other dog which he had ever 
seen ; her puppy, which never could have seen her mother 
beg, now when full grown performs the same peculiar move- 
ment exactly in the same way."t 

As regards the inheritance of disposition, we have only 
to look to the sundry breeds of dogs to see how marked 
differences of this kind may become signally distinctive of 
different breeds. It will be remembered that at present we 
are only concerned with the inheritance of useless, unintelli- 
gent, or non-adaptive habits, and therefore have here nothing 
to do with the useful and intelligent habits which are bred 
into our various races of dogs by means of artificial selection 
combined with training. But even in the case of purely 
meaningless traits of character, which are of no use either to 
the animals themselves or to man, we find the influences of 
heredity at work. Thus, for instance, the useless and even 
annoying habit of barking round a carriage, which occurs 
among sundry breeds of dogs, is particularly pronounced in 
the collie, and is truly innate or not dependent on imitation. 
This is shown by the fact that collies which from puppyhood 
have never seen other dogs bark at horses, will nevertheless 
spontaneously begin to do so.:j: Several other useless traits 
of character or disposition peculiar to different breeds might be 
mentioned ; but I shall pass on to the most remarkable instance 

* This case is stated in different words in Variation of Animals and 
Flanls, &c., vol. i, pp. 450-1. 

t Here, however, I may remark that I have noticed several Syke terriers 
perforin these movements while begging, so that the action seems to be due 
to some race-distinction of a psycliological kind, and not merely to an indi- 
vidual peculiarity. It therefore leads on to the class of cases next considered 
in the text. 

X See Nature, vol. xix, p. 234. 



ORIGIN AND DEVELOPMENT OF INSTINCTS, 187 

I have met with in dogs of the inheritance of a thoroughly sense- 
less psychological peculiarity. I refer to the instance "which 
was communicated some years ago to Mr. Darwin by Dr. 
Huggins, r.R.S., and which I shall quote in his own words. 

" I wish to communicate to you a curious case of an 
inherited mental peculiarity, I possess an English mastiff, 
by name Kepler, a son of the celebrated Turk out of Venus. 
I brought the dog, when six weeks old, from the stable in 
which he was born. The first time I took him out he started 
back in alarm at the first butcher's shop he had ever seen. 
I soon found he had a violent antipathy to butchers and 
butchers' shops. "When six months old a servant took him 
with her on an errand. At a short distance before coming to 
the house she had to pass a butcher's shop ; the dog threw 
himself down (being led with a string), neither coaxing or 
threats would make him pass the shop. The dog was too 
heavy to be carried, and as a crowd collected, the servant had 
to return with the dog more than a mile, and then go without 
him. This occurred about two years ago. The antipathy 
still continues, but the dog will pass nearer to a shop than 
he formerly would. About two months ago, in a little book 
on dogs, published by Dean, I discovered that the same 
strange antipathy is shown by the father, Turk. I then 
wrote to Mr. NichoUs, the former owner of Turk, to ask him 
for any information he might have on the point. He replied, 
' I can say that the same antipathy exists in King, the sire 
of Turk, in Turk, in Punch (son of Turk out of Meg), and in 
Paris (son of Turk out of Juno). Paris has the greatest 
antipathy, as he would hardly go into a street where a 
butcher's shop is, and would run away after passing it. 
When a cart with a butcher's man came into the place where 
the dogs were kept, although they could not see him, they 
all were ready to break their chains. A master-butcher, 
dressed privately, called one evening on Paris' master to see 
the dog. He had hardly entered the house before the dog 
(though shut in) was so much excited that he had to be put 
into a shed, and the butcher was forced to leave without 
seeing the dog. The same dog at Hastings made a spring at 
a gentleman who came into the hotel. The owner caught the 
dog and apologised, and said he never knew him to do so 
before, except when a butcher came to his house. The 
gentleman at once said that was his business.' " 



188 MENTAL EVOLUTION IN ANIMALS. 

We see, then, that non-intelligent habits of non-adaptive 
or useless character may be strongly inherited by domestic 
animals. As showing that the same is true of breeds or strains 
in wholly wild animals, I may quote Humboldt, who says,* 
that the Indians who catch monkeys to sell them " knew very 
well that they can easily succeed in taming those which 
inhabit certain islands ; while monkeys of the same species, 
caught in the neighbouring continent, die of terror or rage 
when they find themselves in the power of man :" and in his 
MSS I find that Mr. Darwin has a note saying, " divers 
dispositions seem to run in families of crocodiles." But one 
of the most curious instances that I have met with of the 
commencement of a racial and useless deviation from a 
strong ancestral instinct, is one which is communicated to 
Mr. Darwin in a letter from Mr. Thwaits, who writes from 
Ceylon under the date 1860, and whose letter I find among 
Mr. Darwin's MSS. Mr. Thwaits here says that his 
domestic ducks quite lost their natural instincts with regard 
to water, which they never enter unless driven. The young 
birds, when forcibly placed in a tub of water are " quite 
alarmed," and have to be quickly taken out again " or they 
would drown in their struggling." Mr. Thwaits adds that 
this peculiarity does not extend to all the ducks in the 
island, but only occurs in one particular breed or strain. 

In Mr. Darwin's MSS I also find the following remarks : 
" So many independent authors have stated that horses in 
different parts of the world inherit artificial paces, that I 
think the fact cannot be doubted. Dureau de la Malle 
asserts that these different paces have been acquired since 
the time of the Roman classics, and that from his own 
observation they are inherited.! .... Tumbler pigeons 
offer an excellent instance of an instinctive action, acquired 
under domestication, which could not have been taught, but 
must have appeared naturally, though probably afterwards 
vastly improved by the continued selection of those birds 
which showed the strongest propensity — more especially in 

* Personal Narrative, vol. iii, p. 383. 

t After giving numerous references on this point in a footnote, 
Mr. Darwin concludes the latter thus : — " I may add that I was formerly 
struck by no horse on the grassy plains of La Plata havinfj the natural high 
action of some P2nglish horses." For a number of other instances of here- 
ditary transmission of qualities in the case of the Horse, see Variation of 
Animals and Plants. Sec. vol. i, pp. 454-6. 



ORIGIN AND DEVELOPMENT OF INSTINCTS. 189 

ancient times in the East, when flying pigeons was much 
esteemed. Tumblers have the habit of flying in a close 
flock to a great height, and as they rise tumbling head over 
tail. I have bred and flown young birds, which could not 
possibly have ever seen a tumbler; after a fev/ attempts 
even they tumbled in the air. Imitation, however, aids the 
instinct, for all fanciers are agreed that it is highly desirable 
to fly young birds with first-rate old ones. Still more 
remarkable are the habits of the Indian sub-breed of tumblers, 
on which I have given details in a former chapter, showing 
that during at least the last 250 years these birds have been 
known to tumble on the ground, after being slightly shaken, 
and to continue tumbling until taken up and blown upon. 
As this breed has gone on so long, the habit can hardly be 
called a disease. I need scarcely remark that it would be as 
impossible to teach one kind of pigeon to tumble as to teach 
another kind to inflate its crop to the enormous size which 
the pouter pigeon habitually does."* 

This case of the tumblers and pouters is singularly 
interesting and very apposite to the proposition before us, for 
not only are the actions utterly useless to the animals them- 
selves, but they have now become so ingrained into their 
psychology as to have become severally distinctive of different 
breeds, and so not distinguish a.ble from true instincts. This 
extension of an hereditary and useless habit into a distinction 
of race or type is most important in the present connection. 
If these cases stood alone they would be enough to show that 
useless habits may become hereditary, and this to an extent 
which renders them indistinguishable from true instincts.f 

In the Appendix several instructive cases of the same 
kind will be found, such as that of the Abyssinian pigeon, 
which, when fired at, " plunges down so as almost to touch 
the sportsman, and then mounts to an immoderate height fX 
the biscacha, which " almost invariably collects all sorts of 

* For further particulars on the instinct of tumbling, see Variation of 
Animals and Plants, vol. i, p. 219, and 230. 

I Some years ago the Eatels which were confined in one cage at the 
Zoological Gardens acquired the apparently useless habit of perpetually 
tumbling head over heels. If their progeny were to be exposed for a number 
of generations to similar conditions of life, they would pi-obably develope a 
true instinct of turning somersaults analogous to that of the tumbler- 
pigeon. 

X I have frequently no'dL'ed a siiiiilar propensity in the Lapwing. 



190 MENTAL EVOLUTION IN ANIMALS. 

rubbish, bones, stones, dry dung, &c., near its burrow ; " the 
guanacoes which " have the habit of returning (like flies) to 
the same spot to drop their excrement ; " horses, dogs, and 
the hyrax, showing a somewhat similar and equally useless 
propensity ; hens cackling over their eggs, &c., &c. So that 
I think the evidence is abundant in support of the proposi- 
tion that senseless or useless habits may be inherited, and 
thus become racial characteristics, or purposeless instincts. 

Passing on, then, to Propositions III and IV, — viz., that 
such habits may vary, and that vjhen they vary the variations 
may be inherited — the truth of these facts has already been 
made apparent. The paces of the horse in different parts of 
the world are so many race-characteristics of the animals ; the 
ground-tumblers display an inherited variation as compared 
with the air-tumblers, and if tumblers are not allowed to 
exercise their art, it undergoes the variation of becoming 
obliterated — just as we shall presently see is the case with 
many true instincts. The different dispositions of the same 
species of monkeys on different islands, prove that the 
ancestral disposition must have varied in the progeny, and 
have then continued to be inherited in its varied states along 
the several lines of descendants. 

From the exclusive nature of the requirement, it is not 
easy to find many examples of inherited varieties of useless 
habits, nor is it important that I should give a number of 
illustrations on this head. There is abundant evidence that 
non-intelligent and purposeless habits are inherited, and this 
is the main point ; for that such habits, when inherited, should 
vary, is a matter of certainty, seeing, as we presently shall, 
that such is the case even with intelligent and useful habits. 
If the latter are liable to vary in their course of inheritance, 
a fortiori the former must be similarly liable, inasmuch as 
they arise in a manner analogous to fortuitous " sports " of 
structure (which are always eminently variable), and after- 
wards have no check imposed on their variability either by 
intelligence or by selection. 

Similarly Proposition V requires very little to be said in 
the way of proof. If among a number of meaningless habits, 
all more or less hereditary and more or less varial^le, any one 
should happen from the first to be, or afterwards to vary so 



ORIGIN AND DEVELOPMENT OF INSTINCTS. 191 

as to become accidentally beneficial to the animal, then we 
are bound to believe that natural selection would fix this 
habit, or its beneficial variations. And the proof that such 
a process has taken place is given by the fact of their being 
many instincts — such as the incubating instinct before 
alluded to — which cannot conceivably have been developed 
in any other way. Whether or not this instinct began in 
habits adapted to the protection of the eggs, it is certain that 
it cannot have begun with any intelligent reference to hatch- 
ing them ; and it is no less certain that before the instinct 
attained its present degree of perfection, it must have passed 
through many stages of variation, few if any of which can 
have been due to intelligent purpose on the part of the birds. 
And further proof is rendered, as I have also previously 
observed, by the fact that many instincts are displayed by 
animals too low in the zoological scale to admit of our sup- 
posing that they can ever have been due to intelligence. To 
give only one illustration, the larva of the caddice fly lives in 
water and constructs for itself a tubular case made of various 
particles glued together. If during its construction this case 
is found to be getting too heavy — i.e., its specific gravity 
greater than that of the water — a piece of leaf or straw is 
selected from the bottom of the stream to be added to the 
structure ; and conversely, if the latter is found to be getting 
too light, so as to show a tendency to float, a small stone is 
morticed in to serve as ballast.* In such a case as this it 
seems impossible that an animal so low in the zoological 
scale can ever have consciously reasoned — even in the most 
concrete way — that some particles have a higher specific 
gravity than others, and that by adding a particle of this or 
that substance, the specific gravity of the whole structure 
may be adjusted to that of the water. Yet the actions 
involved are no less clearly something more than reflex ; they 
are instinctive, and can only have been evolved by natural 
selection. Similarly, Professor Duncan suggests, in a lecture 
before the British Association, 1872, that the instinct of the 
Odynerus — which forms a tubular ante-chamber and provision- 
chamber filled with stung grubs for the future use of offspring 
which it never saw — probably arose in this way. M. Tabre 
has observed that Bembex inclica lays an egg in a chamber, 

* A Movographic Revision and Si/nopsis of the Trichoj^tera of the 
European Fauna, 1881, by Eobert M'Lachlan, F.E.S. 



192 MENTAL EVOLUTION IN ANIMALS. 

and that the egg hatches very shortly. The insect then visits 
its living offspring every day, bringing it small larvae stung 
to keep them quiet. Now this instinct may have been 
altered in Odynerus by a delay arising in the time of hatch- 
ing, and a series of victims having been therefore placed in 
the provision-chamber in obedience to the primitive instinct, 
which has thus become modified into a new one. 

Numerous other instincts will be found mentioned in the 
Appendix, the origin of which can only be attributed to the 
uncompounded influence of natural selection. I feel, there- 
fore, that it is needless for me to adduce further illustrations, 
and so shall here conclude my observations on instincts of 
the primary class. 

Secondary Instincts. 

Coming now to the second series of proj)ositions, we shall 
find that their proof casts a good deal of reflected light upon 
those which we have just considered — light which tends still 
further to demonstrate the latter. 

First, then, we have to show that " intelligent adjustments, 
vjhen frequently performed hy the individual, become automatic, 
either to the extent of not requiring conscious thought at all, or, 
as consciously adjustive habits, not requiring the same degree of 
conscious effort as at first. 

The latter part of this proposition has already been 
proved in an earlier chapter of this book. That " practice 
makes perfect" is a matter, as I have previously said, of 
daily observation. Whether we regard a juggler, a pianist, 
or a billiard player, a child learning his lesson, or an actor his 
part by frequently repeating it, or any one of a thousand other 
illustrations of the same process, we see at once that there is 
truth in the cynical definition of a man as " a bundle of 
habits." And the same, of course, is true of animals. 
" Training " an animal is essentially the same process as 
educating a child, and, as we shall presently have occasion to 
show, animals in a state of nature develop special habits in 
relation to local needs. 

The extent to which habit or repetition may thus serve 
to supersede conscious effort is a favourite theme among 
psychologists ; and one or two instances have already been 
given in the chapter on the Physical Basis of Mind. To 
this point, therefore, I need not recur. 



ORIGIN AND DEVELOPMENT OF INSTINCTS. 193 

It remains to mention another class of acquired mental 
habits, and one which is still more suggestive in relation to 
instinct, inasmuch as the habits are purely mental, and not 
associated with mechanically distinctive movements. Thus, 
as Professor Alison remarks,* the sense of modesty in man is 
not a true instinct, because it is neither innate nor is it ex- 
hibited by all the members of the species — being, in fact, 
only displayed by the civilized races. Yet, although merely 
a taught habit of mind, among morally cultured persons it is 
in strength and precision indistinguishable from a true 
instinct. Similarly, though in a lesser degree, the influences 
of refinement and good taste, operating upon the individual 
from childhood, produce such a powerful and unremitting 
influence, that the extreme nicety, spontaneity, and readiness 
of adjustment to highly complex conditions which result are 
recognized even in ordinary conversation as akin to the 
promptings of instinct; for we commonly say that a man 
has "the instincts of a gentleman," or that so and so is 
"underbred" This latter term, however, introduces us to 
the division of our subject which we have to consider under 
the next heading — namely, the extent to which habits of 
mind, intentionally or intelligently acquired by the individual, 
may be transmitted to progeny. To this branch of our dis- 
cussion, therefore, we shall now pass.f 

Accepting, then. Proposition VI as beyoncl dispute, we 
have here to substantiate Proposition VII, viz., That automatic 
actions and conscious habits may he inherited, 

Now we have already seen that this is certainly the case 

* Article "Instinct," Todd's Cyclo. of Anat., vol. iii, 1839. 

t Mr. Darwin's MS points out that persons of weak intellect are very apt 
to fall into habitual or automatic actions, ai^d these, from not being performed 
under the mandates of the will, are more nearly allied to reflex actions than 
are properly voluntary or deliberate movements. This correlation is also to be 
observed in animals, and the MS gives a case which Mr. Darwin observed of 
an idiotic dog, whose instinct of turning round before lying down (a remnant, 
probably, of the instinct of forming a bed in long grass) was so strongly 
developed, or so little checked by intelligence, "that he has been counted to 
turn round twenty times before lying down." 

This action of turning round may certainly be regarded as the survival 
of a secondary instinct. Now secondary instincts are formed by a descent 
from intelligent action, through habitual action, towards reflex action ; there- 
fore it is interesting that when, as in such a case as this, they are fully formed 
as instincts, they are found to resemble automatic habits in showiug most 
unrestricted play when intelligence is enfeebled or idiotic. 



194 MENTAL EVOLUTION IN ANIMALS. 

with automatic actions which have arisen accidentally, or 
without intelligent purpose ; and it would be anomalous were 
the fact otherwise with automatic actions wliich have been 
acquired consciously. The evidence that the fact is not 
otherwise is considerable. 

First we may take the case of man. " On what a curious 
combination of corporeal structure, mental character, and 
training," says Mr. Darwin, "must hand- writing depend! 
Yet every one must have noted the occasional close similarity 
of the hand- writing in father and son, although the father 
had not taught the son .... Hofacker, in Germany, 
remarks on the inheritance of hand -writing ; and it has been 
even asserted that English boj's, when taught to write in 
France, naturally cling to their English manner of writing." 
Dr. Carpenter says he is " assured by Miss Cobbe that in her 
family a very characteristic type of hand- writing is traceable 
through five generations;" and in his own family there 
occurred a curious case of a gentleman who inherited a 
" constitutional " character of hand-writing, and lost his right 
arm by an accident; "in the course of a few months he 
learnt to write with his left hand, and before long the hand- 
writing of the letters thus written came to be indistinguish- 
able from that of his former letters." This case reminds me 
of a fact which I have frequently observed — and which has 
doubtless been observed by others — viz., that if I write in any 
unusual direction (as, for instance, on the perpendicular face 
of a recording cylinder), the hand-writing is unaltered in 
character, although both the hand and the eye are working in 
a most unusual manner ; so strong is the mental element in 
hand-writing. Similarly, as observed in a previous chapter, 
if one takes a pencil in each hand and writes the same word 
with both hands simultaneously — the left hand writing from 
right to left — on holding the backward written word before 
a mirror, the hand-writing may at once be recognized. 

Many other instances might be given of the force of 
inheritance in the mental acquisitions of man.* But turning 

* See Carpenter, Mental Physiology, pp. 393-4, where he discusses and 
gives eases of hereditary aptitude for music and painting. Also Galton's 
ITerediiary Genivs, for high mental qualities running in families, either in 
the same or in analogous Uncs of activity ; and Spencer (Psychology, i, p. 422) 
for race-characteristics of psychology in man. The effects of " good breeding " 
or " blood" in bequeathing hcredit&ry disposition and refinement have already 



OEIGIN AND DEVELOPMENT OF INSTINCTS. 195 

now to the more important case of animals, I shall give only 
a few examples among almost any number that I could 
quote. Thus, in Norway, the ponies are used without 
bridles, and are trained to obey the voice ; as a consequence 
a race-peculiarity has been established, for Andrew Knight 
says " the horse breakers complain, and certainly with very 
good reason, that it is impossible to give them what is called 
a mouth; they are nevertheless exceedingly docile, and more 
than ordinarily obedient, when they understand the commands 
of their masters."* Again, Mr. Lawson Tait tells me that he 
had a cat which was taught to beg for food like a terrier, so 
that she developed the habit of assuming this posture — so 
very unusual in a cat — whenever she desired to be fed. All 
her kittens adopted the same habit under circumstances which 
precluded the possibility of imitation ; for they were given 
away to friends very early in life, and greatly surprised their 
new owners when, several weeks afterwards, they began 
spontaneously to beg.f 

In order to show that the same principles apply to 
animals in a state of nature, it will be enough to adduce the 
one instance of hereditary wildness and tameness, for this 
instance affords evidence of the most conclusive kind. Wild- 
ness or tameness simply means a certain group of ideas or 
disposition, having the character of an instinct, so that we 
may properly speak of a wild animal as " instinctively afraid " 
of man or other enemy, and of a tame one as instinctively 
the reverse. Indeed, one of the most typical and remarkable 
illustrations of instinct that could be given is that of the in- 
born dread of enemies, as exhibited, for instance, by chickens 
at the sight of a hawk, by horses at the smell of a wolf, by 
monkeys at the appearance of a snake, &c, Now, fortunately, 
there is material for amply proving both that these instincts 
may be lost by disuse, and, conversely, that they may be 
acquired as instincts by the hereditary transmission of 
ancestral experience. 

been alluded to, and I think observation will show that the same applies to 
the sense of modesty. 

* Phil. Trans., 1839, p. 369. 

+ Inasmuch as the action of " begging " is so unusual in the Cat, the 
above case of its hereditary transmission is more remarkable than the similar 
cases which occur in the Dog ; see Lewes, Problems of Life and Mijid. vol. i, 
p. 229, and Fiske, Cosmic Philosophy, vol. ii, p. 150, and more especially a 
case recorded by Mr. L. Hurt, in Nature (Aug. 1, 1872) of a Skye terrier 



196 MENTAL EVOLUTION IN ANIMALS. 

The proof that instinctive wildness natural to a species 
may be lost by disuse is strikingly rendered by the case of 
rabbits. As Mr, Darwin remarks, "hardly any animal is 
more difficult to tame than the young of the wild rabbit ; 
scarcely any animal is tamer than the young of the tame 
rabbit ; but I can hardly suppose that domestic rabbits have 
often been selected for tameness alone ; so we must attribute 
at least the greater part of the inherited change from extreme 
wildness to extreme tameness, to habit and long-continued 
close confinement;* and in his MSS he adds, "Captain 
Sulivau, R.N., took some young rabbits from the Falkland 
Islands, where this animal has been wild {i.e., feral) for 
several generations, and he is convinced that they are more 
easily tamed than really wild rabbits in England. The 
facility of breaking in the feral horses in La Plata can, I 
think, be accounted for on the same principle of some little 
of the effects of domestication being long inherent in the 
breed." Similarly Mr, Darwin points out in his MSS that 
there is a great contrast between the natural tameness of the 
tame duck and the natural wildness of the wild,t The still 
more remarkable contrasts which are presented between our 
domestic dogs, cats, and cattle I shall consider later on ; for 
in them it is probable that the principle of selection has 

belonging to him which had great difficulty in acquiring by tuition the 
accomplishment of begging, but afterwards habitually practised it as a general 
expression of desire. Mr. Hurt then adds, " One of his daughters, who haa 
never seen her father, is in the constant habit of sitting up, although she has 
never been taught to do so, and has not seen otliers sit up," 

* Origin of Species, p. 211. 

t With reference to these points I may here appropriately quote the fol- 
lowing note, which occurs among Mr. Darwin's MSS. 

" ' The wild rabbit,' says Sir J. Sebright {On Instincts, 1836, p. 10) ' is by 
far the most untameable animal that I know, and I have had most of the 
IBritish Mammalia in my possession. I have taken the young ones from the 
nest, and endeavoured to tame them, but could never succeed. The domestic 
rabbit, on the contrary, is perhaps more easily tamed than any other animal, 
excepting the dog.' We have an exactly parallel case in the young of the 
wild and tame Duck." 

I may also quote the following interesting corroboration of the above 
statement with reference to ducks, from a letter recently published in Nature, 
by Dr. Eae, F.K.S. (July 19, 1883) :— " If 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.' " 



OKIGIN AND DEVELOPMENT OF INSTINCTS. 197 

played an important part, and at present we are confining 
our attention to the evidence concerning the formation of 
secondary instincts, or the mere lapsing of intelligence into 
instinct without the aid of selection. 

We see, then, that the instinct of wildness may be eradi- 
cated by mere disuse, without any assistance from the 
principle of selection, and further, that this effect persists, or 
becomes but gradually obliterated, through successive genera- 
tions of the animals when feral, or restored to their abori- 
ginal conditions of life. Conversely, it has now to be shown 
that instincts of wildness may be acquired by the hereditary 
transmission of novel experiences, also without the aid of 
selection. This is shown conclusively by the original tame- 
ness of animals in islands unfrequented by man, gradually 
passing into an hereditary instinct of wildness as the special 
experiences of man's proclivities accumulate ; for although 
selection may here play a subordinate part, it must be a very 
subordinate one. Pages might be filled with facts on this 
head from the writings of travellers, but to economize space 
I cannot do better than refer to Mr. Darwin's remarks, with 
their appended references in his chapter at the end of this 
volume. To these remarks, however, I may add that the 
development of fire-arms, together with the growth of sporting 
interests, has given game of all kinds an instinctive know- 
ledge of what constitutes " safe distance," as every sportsman 
can testify; and that such instinctive adaptation to newly 
developing conditions may take place without much aid 
from selection is shown by the short time, or the small 
number of generations, which is sufficient to allow for the 
change — witness, for instance, the following, which I quote 
from the paper on "Hereditary Instinct" by the careful 
observer, Andrew Knight : — " I have witnessed, within the 
period above mentioned, of nearly sixty years, a very great 
change in the habits of the Woodcock. In the first part of 
that time, when it had recently arrived in the autumn, it was 
very tame ; it usually chuckled when disturbed, and took 
only a very short flight. It is now, and has been during 
many years, comparatively a very wild bird, which generally 
rises in silence, and takes a comparatively long flight, excited, 
I conceive, by increased hereditary fear of man."* 

» Phil Tram., 1837, p. 369. 



198 MENTAL EVOLUTION IN ANIMALS. 

But the force or influence of heredity in the domain of 
instinct (whether of the primary or secondary class) is per- 
haps most strongly manifested in the effects of crossing. It 
is not, indeed, easy to obtain this class of evidence in the 
case of wild species, because hybrid forms in a state of nature 
are rare. But when a wild species is crossed with a tame 
one, it usually happens that the hybrid or mongrel progeny 
present a blended psychology. And still more cogent is the 
evidence of such blending when two different breeds of 
domesticated animals are crossed, having diverse hereditary 
habits, or as Mr. Darwin calls them, " domestic instincts." 
Thus a cross-breed between a setter and a pointer will blend 
the movements and habits of working peculiar to these two 
breeds; Lord Alford's celebrated strain of greyhounds ac- 
quired much courage from a single cross with a bull-dog ; * 
and a cross with a beagle " generations back will give to a 
spaniel a tendency to hunt hares."t 

Again, Knight says : — " In one instance I saw a very 
young dog, a mixture of the Springing Spaniel and Setter, 
wdiich dropped upon crossing the track of a Partridge, as its 
male parent would have done, and sprang the bird in silence ; 
but the same dog, having a couple of hours afterwards found 
a Woodcock, gave tongue very freely, and just as its female 
parent would have done. Such cross-bred animals are, how- 
ever, usually worthless, and the experiments and observations 
I have made upon them have not been very numerous or 
interesting." 

On this point Mr. Darwin writes : — " These domestic 
instincts, when thus tested by crossing, resemble natural 
instincts, which in like manner become curiously blended 
together, and for a long time exhibit traces of the instincts of 
either parent ; for example, Le Eoy describes a dog, whose 
gxeat-grandfather was a wolf, and this dog showed a trace of 
its wild parentage only in one way, by not coming in a 
straight line to his master when called."J Some further 
remarks on this subject will be found in Mr. Darwin's 
appended essay on instinct ; and here I may fitly conclude 
the present chapter by quoting the following paragraph 
which occurs in another part of his MSS. 

* Youatt on Dog, p. 311. 

f Blaine, Rural Sports, p. 8G3, quoted by Darwin. 

X Ori<jin of Species, p. 210. 



ORIGIN AND DEVELOPMENT OF INSTINCTS. .199 

" In Chapter VII I have given some facts showing that 
when races or species are crossed there is a tendency in the 
crossed offspring, from quite unknown causes, to revert to 
ancestral characters. A suspicion has crossed me that a 
slight tendency to primeval wildness sometimes thus appears 
in crossed animals. ,Mr. Garnett in a letter to me states that 
his hybrids from the musk and common duck 'evinced a 
singular tendency to wildness.' Waterton (' Essays on 
Natural History,' p. 197) says that in his duck, a cross 
between the wild and the tame, 'their wariness was quite 
remarkable.' Mr. Hewitt, who has bred more hybrids 
between pheasants and fowls than any other man, in letters 
to me speaks in the strongest terms of their wild, bad, and 
troublesome dispositions ; and this was the case with some 
which I have seen. Captain Hutton made nearly the same 
remark to me in regard to the crossed offspring from a tame 
goat and a wild species from the western Himalaya. Lord 
Powis' agent, without my having asked him the question, 
remarked to me that the crossed animals from the domestic 
Indian Bull and common cow ' were more wild than the 
thorough-bred breed.' I do not suppose that this increased 
wildness is invariable; it does not seem to be the case, 
according to Mr. Eyton, with the crossed offspring from the 
common and Chinese geese; nor, according to Mr. Brent, 
with crossed breeds from the Canary." 



200 . MENTAL EVOLUTION IN ANIMALS. 



CHAPTER XIII. 

Instinct (continued). 

Blended Okigin, or Plasticity of Instinct. 

Feom the foregoing discussion it may, I think, be taken as 
established : — 

1st. That propensities or habitual actions may originate 
and be inherited without education from parents or other- 
M'ise, as in the case of " tricks of manner," peculiar disposi- 
tions, tumbling of tumbler pigeons, &c. ; in such cases there 
need be no intelligence concerned in the propensity or action, 
but if such propensities or actions occur in nature (and, as we 
have seen, there can be no doubt that they do), those which 
happen to be of benefit to the animals performing them, will 
be fixed and improved by natural selection ; when thus fixed 
and improved they constitute what I have called instincts of 
the primary class. 

2nd. That adjustments originally intelligent may by 
frequent repetition become automatic, both in the individual 
and in the race ; as instances of such " lapsed intelligence " 
in the individual I have given the highly co-ordinated and 
laboriously acquired actions of walking, speaking, and 
others ; as instances of the same thing in the race I have 
dwelt on the hereditary character of handwriting, artistic 
talent, &c., and in the case of animals, on peculiar habits — 
such as grinning in dogs, begging in cats — being transmitted 
to progeny, as well as the more instructive facts with regard 
to the loss of wildness by certain domesticated animals, and 
the gradual acquisition of this instinct by animals inhabiting 
islands previously unfrequented by man. All these and 
other such cases have been chosen as illustrations, because in 
none of them can the principle of selection have operated in 
any considerable degree. 



BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 201 

Although for the sake of clearness I have so far kept 
separate these two factors in the formation of instinct, it has 
now to be shown that instincts are not necessarily confined 
to one or other of these two modes of origin exclusively ; but, 
on the contrary, that instincts may have, as it were, a double 
root— the principle of selection combining with that of 
lapsing intelligence to the formation of a joint result. Thus, 
hereditary proclivities or habitual actions, which were never 
intelligent but, being useful, were originally fixed by natural 
selection, may come to furnish material for further improve- 
ment, or be put to improved uses, by intelligence ; and, con- 
versely, adjustments originally due to lapsed intelligence 
may come to be greatly improved, or put to improved uses, 
by natural selection. 

As an example of the first of these complementary cases 
— or that of a primary instinct modified and improved by 
intelligence — let us regard the case of the caterpillar which, 
before changing into a crysalis, crosses a small space with a 
web of silk (to which the crysalis can be firmly suspended), 
but which when placed in a box covered with a muslin lid 
perceives that this preparatory web is unnecessary, and 
therefore attaches its crysalis to the already woven surface 
supplied by the muslin ;* or let us regard the case of the 
bird described by Knight, which observed that, having placed 
her nest upon a forcing house, she did not require to visit it 
during the day when the heat of the house was sufficient to 
incubate the eggs, but always returned to sit upon the eggs 
at night when the temperature of the house fell.t In 
both these cases of primary instincts modified by intelligent 
adaptation to particular circumstances — and hundreds of 
others might be added — it is evident that if the particular 
circumstances were to become general, the adaptation to them, 
becoming likewise general, would in time become instinctive 
by lapsed intelligence: if muslin and forcing houses 
were to become normal additions to the environment of 
the caterpillar or the bird, the former would now cease to 
build its web, and the latter cease to incubate her eggs by 

* See Kirby and Spence, Entomology, vol. ii, p. 476. It is evident that 
the weaving of a web by a caterpillar adapted to tbe needs of its futui'e con- 
dition as a crysalis, must be due to instinct of the primary kind, inasmuch as 
no individual caterpillar prior to the formation of such a structure can have 
known^y experience what it is to be a crysalis. 

t Loc. cit. 



202 MENTAL EVOLUTION IN ANIMALS. 

day ; in eacli case a secondary instinct would become blended 
with a previously existing primary one, so producing a new 
instinct with a double root or origin. 

Conversely, as an example of a primary instinct becoming 
similarly blended with a previously existing secondary, let 
us take the following : — 

The grouse of North America display the curious instinct 
of burrowing a tunnel just below the surface of the snow. In 
the end of this tunnel they sleep securely ; for, when any 
four-footed enemy approaches the moiith of the tunnel, the 
bird, in order to escape, has only to fly up through the thin 
covering of snow. Now in this case the grouse probably 
began to burrow for the sake of protection, or concealment, 
or both ; and, if so, thus far the burrowing was probably an 
act of intelligence. But the longer the tunnel the better 
would it have served the purposes of escape, and therefore 
natural selection would almost certainly have tended to 
preserve the birds which made the longest tunnels, until the 
utmost benefit that length of tunnel could give had been 
attained.* 

Thus then we see that in the formation of instincts there 
are two great principles in action, which may operate either 
singly or in combination ; these two principles being the 
lapsing of intelligence and the agency of natural selection. 
In the previous chapter we were engaged in considering 
instincts which are due to either one or other of these prin- 
ciples alone ; in the present chapter we shall consider 
instincts which are due to the joint operation of both prin- 
ciples. 

Now it is clear at a glance that if even in fully formed 
instincts we often find, as in the above examples, a "little 
dose of judgment," it becomes difficult to estimate the im- 
portance, either of this little dose of judgment becoming 
habitual by repetition, and so improving the previous instinct, 
or of its becoming mixed with the influence of natural selec- 
tion. For, taking the latter case alone, if, as we have seen, 
intelligent actions may by repetition become automatic 
(secondary instincts), and if they may then vary and have 
their variations fixed in beneficial lines by natural selection, 
how much more scope may be given to natural selection in 

• The facts of this case have been told me by Dr. Kae, F.R.S. 



BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 203 

this further development of an instinct, if the variations of 
the instinct are not wholly fortuitous, but arise as intelligent 
adaptations of ancestral experience to the perceived require- 
ments of individual experience. 

Trusting then it is sufficiently clear that the two princi- 
ples which may operate either singly or together in forming 
instincts, may operate together whichever of the two may 
happen to have, in any particular case, the historical priority, 
I may in future neglect to entertain the question of such 
priority ; without considering whether in this and that case 
selection was prior to lapsing of intelligence, or lapsing of 
intelligence was prior to selection, it will be enough to prove 
that the two principles are conjoined. 

To prove this we have to show, much more copiously 
than has been done in the above two or three illustrations, 
not only, as was proved in the previous chapter, that fully 
formed instincts may vary, but further that their variation 
may be determined by intelligence. 

Plasticity of Instinct. 

In former publications I have used this term to express 
the modifiability of instinct binder the influence of intelligence. 
I shall now give some chosen instances of such modifiability, 
and then proceed to indicate the causes which most fre- 
quently lead to intelligence thus acting upon instinct. It is 
of importance that I should begin by rendering the fact of 
the plasticity of instinct beyond question, not only because 
it is still too much the prevalent notion that instincts are un- 
alterably fixed, or rigidly opposed to intelligent alteration 
under changed conditions of life ; but also because it is this 
principle of plasticity that largely supplies to natural selec- 
tion those variations of instinct in beneficial lines, which are 
necessary to the formation of new instincts of a primo- 
secondary kind. 

Huber observes : " How ductile is the instinct of bees, 
and how readily it adapts itself to the place, the circum- 
stances, and the needs of the community." 

If this may be said of the animals in which instinct has 
attained its highest perfection and complexity, even without 
evidence we might be prepared to expect that instinct is 
everywhere ductile. Moreover the bees constitute a good 



204 MENTAL EVOLUTION IN ANIMALS. 

class to clioose for our present purpose, because, as I have 
shown in " Animal Intelligence," their wonderful instinct of 
making hexagonal cells can only be regarded as an instinct 
of the primary kind ; yet, as we shall see, though so well 
fixed an instinct of the primary kind, it may be greatly 
modified by an intelligent appreciation of novel circum- 
stances. 

Kirby and Spence, detailing the observations of Huber, 
write as follows : — 

" A comb, not having been originally well fastened to the 
top of his glass hive, fell down during the winter amongst 
the other combs, preserving, however, its parallelism with 
them. The bees could not fill up the space between its upper 
edge and the top of the hive, because they never construct 
combs of old wax, and they had not then an opportunity of 
procuring new ; at a more favourable season they would not 
have hesitated to build a new comb upon the old one ; but it 
being inexpedient at that period to expend their provision of 
honey in the elaboration of wax, they provided for the 
stability of the fallen comb by another process. They 
furnished themselves with wax from the other combs by 
gnawing away the rims of the cells more elongated than the 
rest, and then betook themselves in crowds, some upon the 
edges of the fallen comb, others between its sides and those 
of the adjoining combs, and there securely fixed it by con- 
structing several ties of different shapes between it and the 
glass of the hive ; some were pillars, some buttresses, and 
others beams artfully disposed and adapted to the localities 
of the surfaces joined. Nor did they content themselves 
with repairing the accidents which their masonry had ex- 
perienced ; they provided against those which might happen, 
and appeared to profit by the warning given by the fall of one 
of the combs to consolidate the others and prevent a second 
accident of the same nature. 

" These last had not been displaced, and appeared solidly 
attached by their base : whence Huber was not a little sur- 
prised to see the bees strengthen their principal points of 
connexion by making them much thicker than before with 
old wax, and forming numerous ties and braces to unite them 
more closely to each other and to the walls of their habita- 
tion. What was still more extraordinary, all this happened 
in the middle of January, at a period when the bees ordinarily 



BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 205 

cluster at the top of the hive, and do not engage in labours of 
this kind 

" Having placed in front of a comb which the bees were 
constructing a slip of glass, they seemed immediately aware 
that it would be very difficult to attach it to so slippery a 
surface, and, instead of continuing the comb in a straight 
line, they bent it at a right angle, so as to extend beyond the 
slip of glass, and ultimately fixed it to an adjoining part of 
the woodwork of the hive which the glass did not cover. 
This deviation, if the comb had been a mere simple and 
uniform mass of wax, would have evinced no small ingenuity ; 
but you will bear in mind that a comb consists on each side 
or face of cells having between them bottoms in common 
and if you take a comb, and, having softened the wax by 
heat, endeavour to bend it in any part at a right angle, you 
will then comprehend the difficulties which our little archi- 
tects had to encounter. The resources of their instinct, 
however, were adequate to the emergency. They made the 
cells on the convex side of the bent part of the comb much 
larger, and those on the concave much smaller than usual ; 
the former having three or four times the diameter of the 
latter. But this w^as not all. As the bottom of the small 
and large cells were as usual common to both, the cells were 
not regular prisms, but the smaller ones considerably wider at 
the bottom than at the top, and conversely in the larger 
ones ! What conception can we form of so wonderful a 
flexibility of instinct ? How, as Huber asks, can we com- 
prehend the mode in which such a crowd of labourers, 
occupied at the same time on the edge of a comb, could agree 
to give it the same curvature from one extremity to the other ; 
or how they could arrange together to construct on one face 
cells so small, while on the other they imparted to them 
such enlarged dimensions ? And how can we feel adequate 
astonishment that they should have the art of making cells 
of such different sizes correspond ? " * 

Other observations of Huber show that even under ordi- 
nary circumstances bees are frequently in the habit of 
altering the construction of their cells. Thus, for instance, 
the cells which are destined to receive drones requiring to be 
considerably larger than those which are destined to receive 
neuters, and the rows of all the cells being continuous, where 

* Kirby and Spence, loc. cif., pp. 485-405. 



206 MENTAL EVOLUTION IN ANIMALS. 

a transition takes place from one class of cell to the other, a 
complex geometrical problem arises how to unite hexagonal 
cells of a small with others of a large diameter, without 
leaving any void spaces or interfering with the regularity of 
the comb. Without occupying space with what would 
necessarily be a rather lengthy exposition of the manner in 
which the bees solve the problem, it is enough to say that 
in passing from one form of cell to the other, they require to 
construct a great many rows of intermediate cells which 
differ in form, not only from the ordinary cells, but from each 
other. When the bees arrive at any stage in this process of 
transition, they might stop at that stage and continue to build 
the whole of their comb upon this pattern. But they inva- 
riably proceed from one stage to another until the transition 
from small hexagons to large hexagons, or vice versd, is 
effected. On this subject Kirby and Spence remark : 
" Eeaum«r, Bonnet, and other naturalists cite these irregu- 
larities as so many examples of imperfections. What would 
have been their astonishment if they had been aware that 
part of these anomalies had been calculated (? adaptive) ; 
that there exists as it were a moveable harmony in the 
mechanism by which the cells are composed ! ... It is 
far more astonishing that they know how to quit their 
ordinary routine when circumstances require that they should 
build male cells : that they should be instructed to vary the 
dimensions and the shape of each piece so as to return to a 
regular order; and that, after having constructed thirty or 
forty ranges of male celJs, they again leave the regular order 
in which they were formed, and arrive by successive diminu- 
tions at the point from which they set out .... Here 
again, as observed in a former instance, the wonder would be 
less if every comb contained a certain number of transition 
and of male cells, constantly situated in one and the same 
part of it ; but this is far from being the case. The event 
which alone, at whatever period it may happen, seems to 
determine the bees to construct male cells, is the oviposition 
of the queen. So long as she continues to lay the eggs of 
workers, not a male cell is provided ; but as soon as she is 
about to lay male eggs, the workers seem aware of it, and 
you then see them form their cells irregularly." 

Here, then, we have concerted variation in the mode of 
constructing the cells of a normal and definite kind, and we 



BLENDED OrJGIN, OK PLASTICITY OF INSTINCT. 207 

find that in this case the variation is determined by an event 
(the oviposition of male eggs) which we may suppose all the 
bees simultaneously to perceive. But in the present connec- 
tion the important thing to note is that during even the 
ordinary work of bees occasion frequently arises to modify 
the construction of their cells, so that the instincts of the 
animal are not, as it were, rigidly set to the undeviating 
formation of the ordinary cell ; there is a " moving harmony " 
in the operation of the instinct which secures plasticity in 
the formation of the comb, so that when occasion arises the 
" moving harmony " as it were, changes its key ; and it does 
so in obedience to an intelligent perception of the exigencies 
of the occasion. 

The same thing is shown in a higher degree by some other 
experiments of Huber, which consisted in making the bees 
deviate from their normal mode of building their combs from 
above downwards, to building them from below upwards, and 
also horizontally. Without describing these experiments in. 
detail, it is enough to say that his contrivances were such 
that the bees had either to build in these abnormal directions 
or not to build at all ; and the fact that under such circum- 
stances they built in directions which none of their ancestors 
or none of themselves had ever built before, is good evidence 
of a primary instinct being greatly modified by intelligence — 
better evidence, be it observed, of modification than that 
which is furnished by the previously cited cases, inasmuch as 
bees often require in a state of nature to change the shape of 
their cells, but cannot ever have required to reverse the 
direction of building them. 

The same remarks apply to the following observations, 
which are also due to Huber. A very irregular piece of 
comb, when placed on a smooth table, tottered so much that 
the humble bees could not work on so unsteady a basis. To 
prevent the tottering, two or three bees held the comb by 
fixing their front feet on the table, and their hind feet on the 
comb. This they continued to do, relieving guard, for three 
days, until they had built supporting pillars of wax. " Now," 
as Mr. Darwin observes in his MSS, " such an accident aa 
this could hardly have occurred in nature." 

Some other humble bees when shut up, and so prevented 
from getting moss wherewith to cover their nests, tore threads 
from a piece of cloth, and " carded them with their feet into 



208 MENTAL EVOLUTION IN ANIMALS. 

a fretted mass," wliicli they used as moss. Again, Andrew 
Knight observed that his bees availed themselves of a kind 
of cement made of wax and turpentine, with which he had 
covered decorticated trees — using this material instead of 
their own propolis, the manufacture of which they discon- 
tinued ;* and more recently it has been observed that bees, 
" instead of searching for pollen, will gladly avail themselves 
of a very different substance, namely, oatmeal." f 

Again, Osmia aurulenta and 0. hicolor are species of bees 
which construct tunnels in hard banks of earth or clay, in 
which they afterwards deposit their eggs — one in each parti- 
tioned cell. But when they find tunnels ready-made (as in 
the straws of a thatched roof) they save themselves the 
trouble of employing their instincts in the way of tunnel- 
making — merely building transverse partitions in the tube to 
form a series of separate cells. It is specially remarkable 
that when they thus utilize the whorl of an empty snail-shell, 
the number of cells which they partition off is regulated by 
the size of the shell, or the length of the whorl. Moreover, 
if the whorl proves too wide near the orifice of the shell for 
its walls to constitute the boundaries of a single cell, the bee 
will build a partition at right angles to the plane of the 
others, so forming a double cell, or two cells side by side.} 

Now, in all these cases it is evident that if, from any 
change of environment, such accidental conditions were to 
occur ordinarily in a state of nature, the bees would be ready 

* Phil. Trans., loc. cit. 

t Origin of Species, p. 228. It is interesting in connection with these 
facts to note how singularly well they happen to meet a criticism of Kirby 
and Spence, which was advanced before they had been observed, with the 
object of discrediting the view of instinct being modified by intelUgence. 
These authors ask {loc. cit., vol. ii, p. 497), why, if such were the case, should 
not bees sometimes be found to use mud or mortar instead of precious wax or 
propolis : " Show us," they say, " but one instance of their having substituted 
mud for propolis .... and there could be no doubt of their having 
been guided by reason." It is curious that this demand should so soon have 
been met by so apposite an observation. Doubtless mud is not so good a 
material for the purposes required as propolis, but as soon as the bees are 
furnished with a substance that is as good, they are ready enough to prove 
their " reason," even to the satisfaction of what was supposed, a priori, a 
crucial test. This ease should serve as a warning against the use of the ques- 
tion-begging argument, which whore any degree of evidence is pi-esented of 
intelligence compounded with instinct, forthwith raises the standard and says 
— Show us an animal doing this or that, which woidd be still more remark- 
able, and then we shall be satisfied. 

X See F. Smith, Catol. Brit. Hymenoptera, pp. 159-60. 



BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 209 

to meet them by intelligent adjustment, wliich, if continued 
sufficiently long and aided by selection, would pass into true 
instincts of building combs in new directions, of support- 
ing combs during their construction, of carding threads of 
cloth, of substituting cement for propolis, or oatmeal for 
pollen. 

Were it necessary, other instances of the plasticity of 
instinct could be drawn from bees and likewise from ants,* 
but quitting now the Hymenoptera, I shall pass to other 
animals. 

Dr. Leech gives,t on the authority of Sir J. Banks, a case 
of a web-spinning spider which had lost five of its legs, and, 
as a consequence, could only spin very imperfectly. It was 
observed to adopt the habits of the hunting spider, which 
does not build a web, but catches its prey by stalking. This 
change of habit, however, was only temporary, as the spider 
recovered its legs after moulting. But it seems evident from 
this case that, so far as the plasticity of instinct is concerned, 
the web-spinning spider would be ready at any time to adopt 
the habit of hunting, if for any reason it should not be able 
to build a web — and this even by way of sudden transition 
in the life-time of an individual. 

Coming now to vertebrated animals, we may easily find 
that the same principles obtain in them. And here, for the 
sake of brevity, I shall confine myself to instances drawn 
from the oldest, most constant, and, therefore, presumably the 
most fixed of the instincts which vertebrated animals display, 
viz., the maternal. 

With regard to Birds, I showed in the preceding chapter 
that individual variations of nest-building are not uncommon. 
We have now to remark that such variations, or deviations 
from the ancestral modes, are not always the result of mere 
caprice, but sometimes of intelligent purpose. In order to 

* See Animal Intelligence, from which. I may specially quote the follow- 
ing, in order to show briefly that ants quite as much as. or more than bees, 
present a " moving harmony " in the construction of their architecture : — 
" The characteristic trait of the building of ants," says Forel, "is the almost 
complete absence of an unchangeable model peculiar to each species, such as 
is found in wasps, bees, and others. The ants know how to suit their indeed 
little perfect work to circumstances, and to take advantage of each situation. 
Besides, each works for itself on a given plan, and is only occasionally aided 
hy others when they understand its plan" (p. 129). 

t Transactions Linn. Soc, vol. xi, p. 393. This case is briefly alluded to 
by Mr. Darwin in the Appendix, 



210 MENTAL EVOLUTION IN ANIMALS. 

show this, it will be sufficient to state the following in- 
stances. 

Thread and worsted are now habitually used by sundry 
species of birds in building their nests, instead of wool and 
horsehair, which in turn were no doubt originally substitutes 
for vegetable fibres and grasses ; this is specially noticeable 
in the case of the tailor-bird and Baltimore oriole, and 
Wilson believes that the latter improves in nest-building by 
practice — the older birds making the better nests. The com- 
mon house-sparrow furnishes another instance of intelligent 
adaptation of nest-building to circumstances ; for in trees it 
builds a domed nest (presumably, therefore, the ancestral 
type), but in towns avails itself by preference of sheltered 
holes in buildings, where it can afford to save time and 
trouble by constructing a loosely formed nest. A similar 
case is furnished by the gold-crested warbler, which builds 
an open cup-shaped nest where foliage is thick, but makes a 
more elaborate domed nest with a side entrance, where the 
site chosen is more exposed. Moreover, the chimney and 
house-swallows have taken to building in chimneys and 
under the roofs of houses by way of an intelligent or plastic 
change of instinct, and in America this change has taken 
place within the last three centuries or less. Indeed, accord- 
ing to Captain Elliott Coues, all the species of swallow on 
the American continent (with one possible exception) have 
modified the structure of their nests in accordance with the 
novel facilities afforded by the settlement of the country ; for 
he writes : — 

" Various species, indeed, now regularly accept the arti- 
ficial nesting-places man provides, whether by design or 
otherwise. Such is notably the case with several kinds of 
Wrens, with at least one kind of Owl, with one Bluebird, the 
Pewit Flycatcher, and especially the House-sparrow. Various 
other birds occasionally avail themselves of like privileges, 
still retaining in the main their original habits. But in no 
other case than that of the Swallows is the modification of 
habit so profound, or so nearly without exception throughout 
the entire family. . . . All of our Swallows have been 
modified by human agency, excepting the Bank Swallow. 
. . . . Some of them, like the Purple Martin and the 
Violet-green Swallow, are still surviving their apprenticeship 
imder the new regime, which the settlement of the country 



BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 211 

has brought about. . . . Those whose acquired habits 
have become thoroughly ingrained are now pretty constant in 
their adherence to a single plan of architecture ; but the 
Violet-green Swallow, for instance, at present nests in a very 
loose fashion, according to circumstances." * 

The statement made in 1870 by the distinguished 
naturalist Pouchet to the effect that within the same interval 
of half a century the house-swallow had materially altered its 
mode of nest-building at Eouen,t was subsequently shown by 
M. Noulet to be erroneous ;| but this passage which I have 
quoted from Captain Elliott Coues is sufficient to show that 
facts analogous to those stated by M. Pouchet have occurred 
among many species of the swallow tribe. 

In " Animal Intelligence " I gave some cases of the 
remarkable intelligence which is displayed by certain birds 
when they remove their eggs or their young from places 
where they have been disturbed (pp. 288-9), and I added the 
remark that it is easy to see that if any particular bird is in- 
telligent enough, as in the cases quoted, to perform this 
adjustive action of conveying young — whether to feeding- 
grounds, as in the case of the hen, or from sources of danger, 
as in the case of partridges, blackbirds, and goat-suckers — 
inheritance and natural selection might develop the originally 
intelligent adjustment into an instinct common to the species. 
And it so happens that this has actually occurred in at least 
two species of birds — viz., the woodcock and wild duck, both 
of which have been repeatedly observed to fly with their 
young to and from their feeding-ground. 

Since writing the above, I have found among Mr. Darwin's 
MSS a letter from Mr. Haust, dated 'New Zealand, December 
9th, 1862, and stating that the " Paradise Duck," which 
naturally or usually builds its nest along the rivers on the 
ground, has been observed by him on the east of the island, 
when disturbed in their nests upon the ground, to build '' new 
ones on the tops of high trees, afterwards bringing their young- 
ones down on their backs to the water," and exactly the 
same thing has been observed of the wild ducks of Guiana. § 
Now, if intelligent adjustment to peculiar circumstances is 

* Birds of Colorado Valley, pp. 292-4. ■[• Comptes Sendzis, Ixx, p. 492. 
X Ibid., Ixxi, p. 78. In the first edition of Animal Intelligence I quote-! 
this statement of Pouchet without knowing that it had been questioned. 
§ See Geol. Journ., toI. iv, p. 325. 



212 MENTAL EVOLUTION IN ANIMALS. / 

thus adequate, not only to make a bird transport her young 
upon her back, or, as in the case of the woodcock, between 
her legs, but even to make a web-footed water-fowl build 
her nest on a high tree, I think we can have no doubt that, 
if the need of such adjustment were of sufficiently long 
continuance, the intelligence which leads to it would eventu- 
ally produce a remarkable modification in the ancestral 
instinct of nest-building. 

Lastly, " a curious example of a recent change of habits 
has occurred in Jamaica. Previous to 1854, the palm swift 
(Tachornis phmnicobea) inhabited exclusively the palm trees 
in a few districts of the island. A colony then established 
themselves in two cocoa-nut palms in Spanish Town, and 
remained there till 1857, when one tree was blown down, and 
the other stripped of its foliage. Instead of now seeking out 
other palm trees, the swifts drove out the swallows who built 
in the piazza of the House of Assembly, and took possession 
of it, building their nests on the tops of the end walls and at 
the angles formed by the beams and joists, a place which 
they continue to occupy in considerable numbers. It is re- 
marked that here they form their nests with much less 
elaboration than when built in the palms, probably from being- 
less exposed."* 

Turnincr now from the instinct of nidification to that of 
incubation, I shall give the results of some observations and 
experiments which I made several years ago and published in 
" Nature," from which I quote the account. In these cases 
the plasticity of the maternal instinct was shown by the fact 
that the instinct was directed in all its force to the young of 
other animals, although there is ample evidence to prove that 
the foster-mothers perceived the unnatural character of their 
brood. Indeed, it is just because of this evidence that I 
quote these cases in the present connection, for otherwise they 
might rather be taken to exemplify non-intelligent variations 
of instinct with which we were concerned in the last chapter. 
But inasmuch as the intelligence of the animals was displayed 
by the manner in which they adapted their ancestral instincts 
to the requirements of their adopted progeny, the cases become 
available rather as proof of the intelligent variation of instinct.f 

* Wallace, Natural Selection, Chapter VI, where see for some of the pre- 
ceding and also for other instances. 

•f The yearning for progeny which arises from the parental instinct being 



BLENDED ORIGIN, OK PLASTICITY OF INSTINCT. 213 

" Spanish hens, as is notorious, scarcely ever sit at all ; but 
I have one purely bred one just now that sat on dummies for 
three days, after which time her patience became exhausted. 
However, she seemed to think that the self-sacrifice she had 
undergone during those three days merited some reward, for 
on leaving the nest, she turned foster-mother to all the 
Spanish chickens in the yard. They were sixteen in number, 
of all ages, from that at which their own mothers had just 
left them up to full-grown chickens. It is remarkable, too, 
that although there were Brahma and Hamburg chickens in 
the yard, the Spanish hen only adopted those of her own 
breed. It is now four weeks since this adoption took place, 
but the mother as yet shows no signs of wishing to cast off 
her heterogeneous brood, notwithstanding that some of her 
adopted chickens have grown nearly as large as herself. 

" The following, however, is a better example of what may 
be called plast^icity of instinct. Three years ago I gave a pea- 
fowl's egg to a Brahma hen to hatch. The hen was an old one, 
and had previously reared many broods of ordinary chickens 
with unusual success even for one of her breed. In order to 
hatch the pea-chick she had to sit one week longer than is 
requisite to hatch an ordinary chick, but in this there is nothing 
very unusual, f^r, as Mr. Spalding observes, the same thing 
happens with every hen that hatches out a brood of ducklings.* 
The object with which I made this experiment, however, was 
that of ascertaining whether the period of maternal care sub- 
sequent to incubation admits, under peculiar conditions, of 

unsatisfied, induces even sucli an intelligent animal as man to adopt progeny ; 
and the proverbial passion of old maids for keeping cats, dogs, and otlier 
domestic animals, is probably analogous to the cases given in the text of 
female animals adopting the young of other species. 

In this connection I may quote the following account which I have 
received from a friend, whom I know to be an accurate and conscientious 
observer ; for it shows that even among birds in a state of nature the yearn- 
ing for progeny may induce them to adopt the young of other species, just as 
in the cases of bu'ds in a state of domestication which are about to be given 
in the text : — 

" In July, 1878, I found a wren's nest with young birds, which were being 
fed by a wren and a sparrow. I made sure that the young birds were wrens, 
and I noticed that the sparrow continued to feed them after they had left the 
nest. The behaviour of the two birds was very dissimilar, the wren being 
bold and its visits to the nest incessant, whereas the sparrow was very shy and 
its visits much less frequent." 

* The greatest prolongation of the incubatory period I have ever known 
was in the case of a pea-hen, which sat very steadily on addled eggs for a 
period of fom' months, and had then to be forced off in order to save her life 
10 



214 MENTAL EVOLUTION IN ANIMALS. 

being prolonged ; for a pea-chick requires such care for a 
very much longer time than does an ordinary chick. As the 
separation between a hen and her chickens always appears to 
be due to the former driving away the latter when they are 
old enough to shift for themselves, I scarcely expected the 
hen in this case to prolong her period of maternal care, and 
indeed only tried the experiment because I thought that if 
she did so, the fact would be the best one imaginable to show 
in what a high degree hereditary instinct may be modified by 
peculiar individual experiences. The result was very sur- 
prising. For the enormous period of eighteen months this 
old Brahma hen remained with her ever-growing chicken, 
and throughout the whole of that time she continued to pay 
it unremitting attention. She never laid any eggs during 
this lengthened period of maternal supervision, and if at any 
time she became accidentally separated from her charge, the 
distress of both mother and chicken was very great. Even- 
tually the separation seemed to take place on the side of the 
peacock ; but it is remarkable that although the mother and 
chicken eventually separated, they never afterwards forgot 
each other, as usually appears to be the case with hens and 
their chickens. So long as they remained together, the 
abnormal degree of pride which the mother showed in her 
wonderful chicken was most ludicrous ; but I have no space 
to enter into details. It may be stated, however, that both 
before and after the separation the mother was in the habit 
of frequently combing out the top-knot of her son — she 
standing on a seat or other eminence of suitable height, and 
he bending his head forward with evident satisfaction. This 
fact is peculiarly noteworthy, because the practice of combing 
out the top-knot of their chickens is customary among pea- 
hens. In conclusion, I may observe that the peacock reared 
by this Brahma hen turned out a finer bird in every way than 
did any of his brothers of the same brood which were reared 
by their own mother, but that on repeating the experiment 
next year with another Brahma hen and several pea-chickens, 
the result was different, for the hen deserted her family at 
the time when it is natural for ordinary hens to do so, and in 
consequence all the pea-chickens miserably perished."* 

I allude to the following instructive case from Jesse's 
" Gleanings,"! because it has been independently and uncon- 
• Nature, Oct. 28, 1875. f VoL i, p. 98. 



BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 215 

sciously corroborated in every detail by a correspondent, 
Mrs. L. MacFarlane, of Glasgow. Indeed, the similarity is so 
precise, that I think the two descriptions must refer to the same 
incident ; but as to this I cannot be sure, because upon my 
writing to Mrs. MacFarlane to enquire, she answers that she 
is not able to inform me. However, this point is immaterial, 
for my correspondent had the story at first hand from the 
lady to whom the birds belonged (and with whom she was 
intimately acquainted), so that if the case is not the same as 
the one narrated by Jesse, its repetition is so exact that the 
same description applies to both the cases. 

" A hen, who had reared three broods of ducks in three 
successive years, became habituated to their taking to the 
water, and would fly to a large stone in the middle of the 
pond, and quietly and contentedly watch her brood as they 
swam about it. The fourth year she hatched her own eggs, 
and finding that her chickens did not take to the water as 
the ducklings had done, she flew to the stone in the pond, and 
called them to her with the utmost eagerness. This recollec- 
tion of the habits of her former charge is not a little curious." 

My correspondent, Mrs. MacFarlane, also gives me another 
closely similar but even more remarkable case, which was 
observed by her sister. Miss MackiUar, of Tarbert, Cantyre. 
In this case a hen had also reared three successive broods of 
ducklings in successive years, and then hatched out a brood of 
nine chickens. The season being late, she was confined for 
some weeks till the chickens became strong enough to face 
the cold weather. Then, in the words of my correspondent, 
" the first day she was let out she disappeared, and after a 
long search my sister found her beside a little stream which 
her successive broods of ducklings had been in the habit of 
frequenting. She had got four of her chickens into the 
stream, which was fortunately very shallow at the time. The 
other five were standing on its margin, and she was endea- 
vouring by all sorts of coaxing hen-language, and by pushing 
each chicken in turn with her bill, to get them into the water 
also." 

From these cases it is evident that in a portion of the 
lifetime of an individual hen there may be laid, by intelli- 
gent observation and memory, the basis of a new instinct, 
adapted to an immense and sudden change in the habits of 
progeny : and that in all the foregoing cases the foster-mother 



216 MENTAL EVOLUTION IN ANIMALS. 

was not blind to the unnatural character of her brood, is proved 
by the fact of her having adapted her actions to their pecu- 
liar requirements. But to test the degree to which such 
adaptation might go, I tried the experiment of selecting the 
two most diverse kinds of animals I could think of, and giving 
the young of the one to be reared as foster-children by the 
other. The animals which I selected for this purpose were a 
ferret and a hen. The following was the result of the experi- 
ment as published at the time in " Nature."* 

" A bitch ferret strangled herself by trying to squeeze 
through too narrow an opening. She left a very young 
family of three orphans. These I gave, in the middle of the 
day, to a Brahma hen, which had been sitting on dummies 
for about a month. She took to them almost immediately, 
and remained with them for rather more than a fortnight, at 
the end of which time I had to cause a separation, in conse- 
quence of the hen having suffocated one of the ferrets by 
standing on its neck. During the whole of the time that the 
ferrets were left ivith the hen, the latter had to sit upon the nest ; 
for the young ferrets, of course, were not able to follow the 
hen about as young chickens would have done, in accordance 
with the strong instinct of following with which Mr. Spalding 
has shown young chickens to be endowed. The hen, as 
might be expected, was very much puzzled at the lethargy of 
her offspring. Two or three times a day she used to fly off 
the nest, calling upon her brood to follow ; but, on hearing 
their cries of distress from cold, she always returned imme- 
diately and sat with patience for six or seven hours more. It 
only took the hen one day to learn the meaning of these 
cries of distress ; for after the first day she would always run 
in an agitated manner to any place where I concealed the 
ferrets, provided that this place was not too far away from 
the nest to prevent her from hearing the cries of distress. 
Yet I do not think it would be possible to conceive of a 
greater contrast than that between the shrill piping note of a 
young chicken and the hoarse growling noise of a young 
ferret. On the other hand, I cannot say that the young 
ferrets ever seemed to learn the meaning of the hen's cluck- 
ing. During the whole of the time that the hen was allowed 
to sit upon the ferrets she used to comb out their hair with 
her bill, in the same way as hens in general comb out the 

* Vol. xi, p. 553. 



BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 217 

feathers of their chicksns. While engaged in this process, 
however, she used frequently to stop and look with one eye 
at the wriggling nest- full with an enquiring gaze expressive of 
astonishment. At other times, also, her family gave her good 
reason to be surprised ; for she used often to fly off the nest 
suddenly with a loud scream, an action which was doubtless 
due to the unaccustomed sensation of being nipped by the 
young ferrets in their search for the teats. It is further 
worth while to remark that the hen showed so much uneasi- 
ness of mind when the ferrets were taken from her to be fed, 
that at one time I thought she was going to desert them 
altogether. After this, therefore, the ferrets were always fed 
in the nest, and with this arrangement the hen was perfectly 
satisfied — apparently because she thought that she had some 
share in the feeding process. At any rate she used to cluck 
when she saw the milk coming, and surveyed the feeding 
with evident satisfaction. 

" Altogether I consider this a very remarkable case of the 
plasticity of instinct. The hen, it should be said, was a 
young one, and had never reared a brood of chickens. A 
few months before she reared the young ferrets, she had been 
attacked and nearly killed by an old ferret which had escaped 
from its hutch. The young ferrets were taken from her 
several days before their eyes were open, 

" In conclusion, I may add that a few weeks before trying 
this experiment with the hen,- 1 tried a similar one with a 
rabbit which had littered six days before .... Unlike 
the hen, however, the doe perceived the imposture at once, 
and attacked the young ferret so savagely that she broke two 
of its legs before I could remove it. To have made the ex- 
periment parallel with the other, however, the two mammalian 
mothers should have littered on the same day." 

Lastly, turning to the Mammalia, a friend of the Eev. 
Mr. White, of Selborne, gave him an account of a leveret 
which he saw reared by a cat.* Prichard gives an account 
of a cat that reared a puppy ,t and from among many analogous 
instances that might be rendered, I shall only quote the 
following, as it is remarkable on account of displaying 
voluntary adoption by a cat of the young of animals which 
her other instincts and constant practice had taught her to 
regard as prey. 

* Bingley, Animal Biography, i, 269, f N^at- Sisf. of Mankind, i, 102. 



218 MENTAL EVOLUTION IN ANIMALS. 

" Some years ago the late Hon. Marmaduke Maxwell of 
Terregles took me to his stable to show me a cat which was 
at the time bringing up a family of young rats. The cat some 
weeks previously had had a litter of five kittens ; three were 
taken away and destroyed shortly after their birth ; next day 
it was found that the cat had replaced her lost kittens by 
three young rats, which she nursed with the two remaining 
kittens. A few days afterwards the two kittens were taken 
away, and the cat very shortly replaced them by two more 
young rats, and at the time I saw them the young rats 
— which were confined in an empty stall — were running about 
quite briskly, and about one-third grown. The cat happened 
to be out when we went into the stable, but came in before 
we left ; she immediately jumped over the board into the 
stall and lay down : her strange foster-family at once ran 
under her, and commenced sucking. What renders the cir- 
cumstance more extraordinary is, that the cat was kept in 
the stable as a particularly good ratter."* 

* Mr. p. Dudgeon, Nature, \o\. xi, p. 77. 



VARIATION OF INSTINCT IN DEFINITE LINES. 219 



CHAPTEE XIV. 

Instinct (continued). 

Modes in which Intelligence determines the Variation 
OF Instinct in Definite Lines. 

"We have now seen that instincts may have what I term a 
blended origin — or, in other words, that intelligent adjust- 
ment by going hand in hand with natural selection, must 
greatly assist the latter principle in the work of forming 
instincts, inasmuch as it supplies to natural selection varia- 
tions which are not merely fortuitous, hut from the first 
adaptive, I shall next show what I conceive to be the chief 
modes in which intelligence thus operates, or co-operates 
with selection, in the formation of instincts. 

Of course in general terms it is easy to see that the mode 
in which intelligence thus co-operates is by enabling an 
animal to perceive that, owing probably to some change in 
its environment, it may best adapt itself to the existing con- 
ditions of its life by deviating in some degree from its 
ancestral instincts (as when the tailor-bird seeks for threads 
of cotton instead of fibres of grass wherewith to sew its nest), 
or by intelligent observation giving rise to adjustive actions, 
which by repetition lead to an instinct de novo (as in the 
case of the honey -guide, which has acquired the remarkable 
instinct of attracting the attention of man, and leading him 
to the nests of bees).* But with animals, as with men, 
original ideas are not always forthcoming at the time they 
are wanted, and therefore it is often easier to imitate than 
to invent. Thus, the first mode which I shall consider 
whereby intelligence may change or deflect an instinct, is 
that of imitation. For although it is true that the initial 
stage of such deflection occurs in the " original ideas," nothing 

* See Animal Intelligence, p. 315. 



220 MENTAL EVOLUTION IN ANIMALS. 

further remains to be said of these. If they occur similarly 
and simultaneously in a large number of individuals, as may 
be the case where the new adjustment is simple and obvious, 
there may be no need of imitation to assist in changing the 
instinct. But in other cases I am inclined to think that 
imitation may play an important part in this matter. I must 
confess, however, that in searching for evidence of one species 
of animal imitating the beneficial habits of another, I have 
been surprised at the rarity of its occurrence, although, as I 
shall presently show, there is abundant evidence of one 
individual imitating the habits of another individual — whether 
of its own or of other species, and whether the action imitated 
is beneficial or useless. This difference, I think, is probably 
to be explained by the reflection that in all cases where such 
imitation between species and species may have obtained in 
the past, we should now only see an instinct common to the 
two species, and therefore should have no evidence that it 
was not always common. Consequently, it is only in cases 
where the imitation by one species of the habits of another 
is in its earlier phases that we can find evidence of the fact. 
The following are the only cases of such imitation that I 
have been able to meet with ; but to them I add a number 
of cases of individual imitation, because this must evidently 
form the groundwork of imitation among species. 
I quote the following from Mr. Darwin's MSS :- 
" From some experiments which I was making, I had 
occasion very closely to watch some rows of the tall kidney- 
bean, and I daily saw innumerable hive-bees alighting as 
usual on the left wing-petel, and sucking at the mouth of the 
flower. One morning, for the first time, I saw several 
humble-bees (which had been extraordinarily rare all summer) 
visiting these flowers, and I saw them in the act of cutting 
with their mandibles holes through the under side of the 
calyx, and thus sucking the nectar: all the flowers in the 
course of the day became perforated, and the humble-bees in 
tlieir repeated visits to the flowers were thus saved much 
trouble in sucking. The very next day I found all the hive- 
bees, without exception, sucking through the holes which 
had been made by the humble-bees. How did the hive-bees 
find out that all the flowers were bored, and how did they so 
suddenly acquire the habit of using the holes ? I never saw, 
though I have long attended to the subject, or heard of hive- 



VAKIATION OF INSTINCT IN DEFINITE LINES. 221 

"bees themselves boring holes. The minute holes made by 
the humble-bees were not visible from the mouth of the 
flower, where the hive-bees had hitherto invariably alighted : 
nor do I believe, from some experiments which I have made, 
tliat they were gxiided by the scent of the nectar escaping 
through these orifices more readily than through the mouth 
of the flower. The kidney-bean is also an exotic. I must 
think that the hive-bees either saw the humble-bees cutting 
the holes, and understood what they were doing, and imme- 
diately profited by their labour ; or that they merely imitated 
the humble-bees after they had cut the holes, and when 
sucking at them. Yet I feel sure that if anyone who had 
not known this previous history had seen every single hive- 
bee, without a moment's hesitation, flying with the utmost 
celerity and precision from the under side of one flower to 
another, and then rapidly sucking the nectar, he would have 
declared that it was a beautiful case of instinct." 

Mr. Darwin in his MSS has also the following observa- 
tions concerning the subject of imitation :-— " It is difficult to 
determine how much dogs learn by experience and imitation. 
I apprehend there can be little doubt that the manner of 
attack of the English Bull-dog is instinctive (Eollin, ' Mem., 
&c.,' tom. iv, p. 339). I believe that certain dogs in South 
America without education rush at the belly of the stag 
which they hunt, and that certain other dogs when first 
taken out run round the heads of Peccaris. We are led to 
believe that these actions are imitative when we hear from 
Sir J. Mitchell (' Australia,' vol. i, p. 292), that his dogs did 
not learn how safely to seize the Emu by the neck, until the 
close of his second expedition. On the other hand Mr. Couch 
('Illustrations of Instinct,' p. 191) gives the case of a dog 
who learned, after a single battle with a Badger, the spot 
where it would inflict a fatal bite, and it never forgot the 
lesson. In the Falkland Islands it seems that the dogs 
learned from each other the best way of attacking the wild 
cattle (Sir J. Eoss, ' Voyage,' vol. ii, p. 246)." 

Again, Mr. Darwin points out that many species of wild 
animals certainly learn to understand and to profit by the 
danger cries and signals employed by other species, and this 
is a kind of imitation.* He also adduces a good deal of 

* Thus, for instance, he says that "the inhabitants of the United States 
like to have martins build on their houses, as their ciy when a hawk 



222 MENTAL EVOLUTION IN ANIMALS. 

evidence to show that birds of different species, whether in a 
state of nature or domestication, frequently imitate one 
another's song; and singing is certainly instinctive, for 
Couch says that he knew a gold-iinch, which had never 
heard the song of its own species, nevertheless singing tliis 
song, though tentatively and imperfectly.* 

Yarrell tells of a hawfinch that learnt the song of a 
blackbird, though afterwards it quite forgot this song, 
which could not have happened with its natural music,t a 
fact which shows that although imitation is able largely to 
modify instinct, its effects are not so deeply engrained as 
those which are stamped by heredity. Even the sparrow, 
which naturally can scarcely be said to have a song, will 
learn the song of a linnet,! and Dureau de la Malle gives the 
case of wild blackbirds in his garden learning a tune from a 
caged bird ;§ similarly, he taught a starling the Marseillaise, 
and from this bird all the other starlings in a canton to which 
he took it learned the air. In this way, too, many biids 
acquire the song of their foster-parents of other species.{| 
Lastly, a number of observations on wild birds in America 
imitating each other's music have lately been published by 
Mr. E. E. rish.f 

It is certain, however, that some birds have a much 
greater aptitude than others, both for learning and retaining 
the songs of different species. Thus a blackbird [starling ?] 
has been known so well to imitate the crowing of a cock as 
to deceive the cocks themselves,** while Yarrell says the same 
thing of a starling's power of imitating the cackling of a hen.tt 
Of course such facts are notorious as regards the Mocking- 
bird {Turdus jpolyglotttis), and also, at least when in a state 

appears serves to alarm the chickens, though the latter are not aborigines 
of the country." And many similar instances might be given, 

* Illustrations of Instinct, p. 113. See also Bechstein, Stuhenvogel, 
4th ed., p. 7. 

t Brit. Birds, vol. i, p. 486. t Descent of Man, p. 370. 

§ Anns, des Sc. Nat., 3rd series. 2 vol. Tome x, p. 118. 

II Barrington, Phil. Trans., 1773, p. 264. 

IT Bulletin of the Buffalo Society of Nat. Sc. 1881, pp. 23-6. 
** Loundoun's Mag. Nat. Hist., vol. iv, p. 433. 

ft Loc. cit., vol. i, p. 204 ; also in 4th ed., vol. ii, pp. 229-30, where it is 
said on the authority of sundry observers, that starlings in a state of nature 
also imitate the kestrel, wryneck, partridge, moorhen, coot, oyster- catcher, 
golden plover, redshank, curlew, whimbrcl, hcrring-guU, quail, and corn- 
crake, while Professor Newton tells me that at Cambridge he has heard the 
starlings vciy perfectly imitating the quacking of ducks. 



VAPJATION OF INSTINCT IN DEFINITE LINES. 223 

of confinement, of parrots, jays, jackdaws, and starlings ; and 
these facts are rendered more remarkable from the additional 
fact til at none of these birds have any proper song of their 
own, and might therefore be supposed not to have a developed 
ear for bird-music. Still more remarkable, however, is the 
fact that these birds are able correctly to imitate songs having 
a proper musical notation, and that they both learn such songs 
more readily and retain them better than even those singing- 
birds which are most apt at learning tunes. For Bechstein 
saj's that even the Bullfinch requires nine months of regular 
and continued instruction to become firm in its performance, 
and that very frequently all instruction is forgotten in moult- 
ing. Couch, indeed, says that with all such birds " it is 
with them as with the human race ; those which are quick 
at attaining are also rapid in losing their acquirements," and 
conversely; but clearly this statement is no more true of 
birds than it is of " the human race." For of any of the 
songless birds above named it would be a sign of unusual 
dulness to require nine months of continuous instruction in 
a single tune, and, on the other hand, they do not so readily 
forget what they learn. But the most remarkable extension 
of the power of vocal imitation which these birds display is 
unquestionably that of uttering articulate words. This 
subject will require to be considered more fully in my next 
work. Meanwhile it is enough merely to mention it with 
reference to the wonderful power and precision of the imita- 
tion which is betokened in thus modifying the instinct of 
uttering a caw or scream, into the singing of a definite tune 
or the speaking of articulate words. 

The habit displayed by cats, and even young kittens, of 
washing their faces might well be deemed instinctive, and so, 
most probably, it is ; but that it may also be acquired by 
imitation is proved by the fact that puppies when brought up 
by a cat perform the same movements. This was first 
observed by Audouin,* and has since been independently 
corroborated by several observers, of whom I may mention 
the following : — 

Dureau de la Malle gives the case of a terrier which 
belonged to himself, and which from the time of its birth 
was brought up with a kitten six months its senior. For two 
years the terrier had no association with other dogs. Soon 

* Anns, des So. Naf., torn, xxii, p. 397. 



224 MENTAL EVOLUTION IN ANIMALS. 

the terrier began to bound like a cat, and to roll a mouse or 
a ball with his fore-paws ; he also licked his paAvs and 
rubbed them over his ears. Yet if a strange cat came into 
the garden he chased it away.* Prichard gives another case 
of a dog reared by a cat learning to lick its paws and wash 
its face,t and a precisely similar case is communicated to me 
by Mrs. M. A. Baines. Another precisely similar case I find 
recorded in Mr. Darwin's MSS as communicated to him by 
Professor Hoffmann of Giessen. Again, the late Dr. Routh, 
President of Magdalen College, Oxford, observed that his 
King Charles terrier (which had been suckled and reared by 
a cat from the age of three days) was as afraid of rain as was 
the foster-mother ; that he would never, if he could possibly 
avoid it, set his paw in a wet place ; that he licked his feet 
two or three times a day for the purpose of washing his face, 
which process he performed " in the true cattish position, 
sitting upon his tail ;" that " he used to watch a mouse-hole 
for hours together ;" and had " in short all the ways, manners, 
and dispositions of his wet-nurse."| Lastly, another case is 
recorded in " Nature "§ of a dog belonging to Mr. C. H. Jeens, 
which, having been reared by a cat from the age of one 
month, used to catch mice, and when it caught one to treat 
it " after the well-known manner of cats, allowing it to run a 
distance, then pouncing upon it, and so on for many minutes." 
Conversely Dr. E. Darwin records the case of a cat learning 
from a dog the medicinal use of the herb Agrostis canina. I 
think it is probable that the following facts, which I quote 
from Mr. Darwin's MSS, are also, in part at least, to be 
attributed to imitation, though here the imitation is within 
the limits of the same species. 

" It has been stated that lambs turned out without their 
mothers are very liable to eat poisonous herbs ; and it seems to 
be certain that cattle, when first introduced into a country, are 
killed by eating poisonous herbs which the cattle already 
naturalized there have learnt to avoid."(| 

It seems needless to give further instances of imitation 

* Anns, des Sc. Nat., torn, xxii, p. 388. 

t Naf. Hist, of Mankind, 3rd ed., voL i, p. 102. 

X Miss Mitford's Life and Letters, vol. ii, p. 277. 

§ Nature, vol. viii, p. 79. 

II See Annls. and Maq. of Nat. Hist. 2nd ser., vol. ji, p. 364; and 
SiillinrjJleeVs Tracts, p. 350. In regard to Lambs, see Yotiatt on Sheep, 
p. 404. 



VARIATION OF INSTINCT IN DEFINITE LINES. 225 

among animals, but it may be said in general that, as the 
feculty of imitation depends on observation, it is found in 
greatest force, as we should expect, among the higher or more 
intelligent animals — reaching its maximum in the monkeys, 
where, as is well known, it passes into ludicrous extremes. 
And in this connection it is interesting to observe that 
a child begins to imitate very early in life, and that the 
faculty goes on developing during the first year or eighteen 
months, after which it remains stationary for a time, and is 
then of much service in developing language.* "With growing 
intelligence, this faculty subsequently declines, and in after 
life may be said to stand in an inverse relation to originality 
or the higher powers of the mind. Therefore among idiots 
below a certain grade (though of course not too low), it is 
usually very strong and retains its supremacy through life, 
while even among idiots of a higher grade, or the " feeble- 
minded," a tendency to undue imitation is a very constant 
peculiarity. The same thing is conspicuously observable in 
the case of many savages ; so that in view of all these facts 
we must conclude that the faculty of imitation is one very 
characteristic of a certain area of mental evolution, and there- 
fore that within the limits of this area it must conduce in no 
small degree to the formation of instinct.f 

* See Prejer, loc. cit., pp. 176-182, where a number of detailed obser- 
vations on this head are given. He says that the first imitative movement begins 
as early as the fifteenth week in protruding the lips when anyone performs 
this action before the child. [This action seems to come naturally to young 
children, and may I think probably have some hereditary connection with the 
same movement as so strongly pronounced in the orang outang. For a picture 
of such protrusion in this animal, see Darwin, Expression of Emotions, p. 141.] 
Towards the end of the first year imitative movements become more numerous 
and more quickly learnt, and the child takes active pleasure in their perform- 
ance. At twelve months Preyer observed his child repeating in its dreams 
imitative movements which had made a strong impression on it while awake, 
— e.g., blowing with the mouth. Later still, complicated imitative movements 
are performed for mere amusement, as is apparently the case with monkeys. 

t With reference to imitation in connection with instinct, I think it is 
desirable here again to express my opinion already given in Animal Intelli- 
gence, on the theory published by Mr. Wallace, in his Natural Selection, 
that the nidification of birds is due to the young birds consciously imitating 
the structure of the nests in which they have themselves been reared — the 
characteristic nidification of each species of bird being thus maintained. I 
have advanced in Animal Intelligence sundry general considerations, which I 
thought sufficient to negative this theory on a priori grounds ; but since then 
I have found among Mr. Darwin's MSS a letter which describes the results 
of the test experiment which Mr. Wallace himself suggests. This experiment 
is to rear young birds from the egg in an artificial nest or incubator unlike 



226 MENTAL EVOLUTION IN ANIMALS. 

But the influence of this faculty in the formation of 
instinct proceeds further than we have yet noted. For 
among the more intelligent animals it is played upon for this 
very purpose by the animals themselves ; the parents of each 
successive generation intentionally educate their young in, 
the performance of quasi-instinctive actions. Thus, for 
instance, old hawks purposely educate the instinctive facul- 
ties of their young, so as more quickly to bring these instincts 
into a state of perfection. For the manner in which hawks 
swoop upon their prey must certainly be regarded as instinc- 
tive ; yet La Malle observed,* and the observation was after- 
wards corroborated by Brehm,t that the old birds perfected 
the natural instincts of their young ones in teaching them 
"dexterity, as well as judgment of distances, by first dropping 
through the air dead mice and sparrows, which the young 
generally failed to catch, and then bringing them live birds 
and letting them loose."| 

And analogous facts are to be observed in the case of old 
birds teaching the young ones to fly. We have already seen 
that Mr. Spalding proved such teaching to be unnecessary in 
the sense of not being required to develop the power of flight. 
This is instinctive, so that the young bird, whether or not 
instructed by its parents, would fly. Yet the instruction 
must be of some use, as in some species^ at any rate, it is 

the natural nest, and then observe whether when adult these birds will 
instinctively build the nest characteristic of their species. Now I find 
among Mr. Darwin's MSS a letter to him from Mr. Weir, which seems to set 
any such question at rest. Writing under the date May, 1868, Mr. Weir 
says as the result of a large experience of birds kept by him in aviaries : — 
" The more I reflect on Mr. Wallace's theory that birds learn to make their 
nests because they have been themselves reared in one, the less incUned do I 
feel to agree with him." He gives the following fact, which seems to be con- 
clusive against this theory : — " It is usual with many 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, removing the other, and this 
is done to avoid acari. But I never knew that canaries so reared failed to 
make a nest when the breeding time arrived. I have on the other hand 
marvelled to see how like a wild bird their nests are constructed. It is cus- 
tomaiy 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 sufEcieut for the purpose. I feel convinced nest building is a true 
instinct." 

* Anns, de Sc. Nat., torn', xxii, p. 406, 

t Mag. Nat. Hint., vol. ii, pi 402. 

j Descent of Man, p. 73. 



VARIATION OF INSTINCT IN DEFINITE LINES. 227 

laboriously given ; * and the only use it can be is that of 
developing the powers of flight more rapidly than they 
would develop if not thus assisted. 

Similarly, the singing of birds is certainly instinctive ; 
yet it is improved by imitation and practice — the young 
birds listening to the old and profiting by their instruction, 
as is proved by the cases previously cited of birds which had 
never heard the songs of their own species yet singing their 
songs, but doing so " tentatively and imperfectly." 

Again, although terriers take to hunting rabbits instinc- 
tively, it is usual, as I have myself observed, for their 
parents to teach them, or lead on their natural instincts by 
imitation, whereby the hereditary aptitude develops more 
quickly than it would if left to itself. 

The Duke of Argyllf give a curious case, which he "knows 
to be authentic," of a golden eagle in the possession of Mr. 
W. Pike, Glendarry, Co. Mayo, which in the spring of 1877 
laid three eggs. These Mr. Pike took away, and substituted 
for them two goose eggs. The eagle hatched out the two 
eggs. One of the goslings died, and was torn up by the 
eagle to feed the survivor, " who, to the great tribulation of 
its foster-parent, refused to touch it. . . . Tlie eagle, 
however, in the course of time, taught the goose to eat flesh, 
and (the goose having free exit and ingress to the eagle's 
cage) always called it by a sharp bark whenever flesh is 
given to it, when the goose hastens to the cage, and greedily 
swallows all the flesh, &c., which the eagle gives it." 

Again, there is evidence to show that the knowledge 
which animals display of poisonous herbs is of the nature of 
a mixed instinct, due to intelligent observation, imitation, 
natural selection, and transmission ; for, as Mr. Darwin points 
out in the Appendix, "lambs turned out without their 
mothers are very liable to eat poisonous herbs ; and it seems 
to be certain that cattle, when first introduced into a country, 
are killed by eating poisonous herbs, which the cattle already 
introduced have learnt to avoid."^ 

In this case there is indeed no evidence of the young 

* Sir H, Davy gives an account of such laborious instruction as witnessed 
by himself in the case of the golden eagle. See Animal Intelligence, p. 290. 

t Nature, vol. xix, p. 554. 

X Yoiiatt on, Shee^, p. 404 ; and Anns, and Mag. Nat. Hist., 2nd ser., 
vol. ii, p. 364, &c. 



228 MENTAL EVOLUTION IN ANIMALS. 

being intentionally instructed by the old, but they are in- 
structed by themselves, i.e., by their individual experience. 
And this is, after all, the most important point, or the point 
to which the intentional education by parents is subsidiary. 
I shall therefore give a few more instances to show that 
many instincts (usually those of obviously secondary origin) 
are first manifested by young animals in an imperfect, or not 
fully evolved condition, and afterwards become perfected in 
the school of individual experience. Such cases stand in 
marked antithesis to those of the congenitally perfect 
instincts already alluded to, which have been so well investi- 
gated by Mr. Spalding. 

It is unquestionably a true instinct that leads a ferret to 
thrust its long canines through the medulla oblongata of its 
victim ; but Professor Buchanan states* that young ferrets, 
" instead of having for their single object to put themselves 
into a position to inflict the death wound, engage in conflict 
with rats ;" yet they had the proper instinct, though not in 
complete working order, for they attacked properly the 
medulla oblongata of dead rats. Similarly I myself observed 
with the ferrets which I reared under a hen, that when half- 
grown and put to a rabbit for the first time, they clearly 
knew that their attack should be directed against one end of 
the rabbit, but were not quite certain which ; for after some 
time of indecision they in the first instance attacked the 
rump, and only after finding this of no use tried the proper 
place. But of more interest still in this connection was the 
behaviour of these ferrets when half-grown towards a fowl. 
They had been taken away from their foster-mother, the 
hen, some weeks previously, but still no doubt retained a 
recollection of her. Therefore, when presented with another 
hen, their hereditary instincts prompted attack, while their 
individual associations inhibited the prompting. There was 
therefore a manifest conflict of feelings, which had its ex- 
pression in a prolonged period of indecision. And although 
eventually the hereditary instincts prevailed over the asso- 
ciations formed by individual experience, the prolonged 
hesitation proved that the latter exerted a strong modifying 
force. 

Mr. Darwin says in his MSS that in 1840 he saw some 
chickens which had been hatched without a mother, and 

* Anns, and Mag. Nat. Hist., vol. xviii, p. 378. 



VARIATION OF INSTINCT IN DEFINITE LINES. 229 

"when exactly four hours old they ran, jumped, chirped, 
scratched the ground, and cuddled together as if under the 
hen ; all actions beautifully instinctive." After giving this 
as an instance of what I have called pure instinct, he pro- 
ceeds by way of comparison to say, " It might have been 
thought that the manner in which fowls drink, by filling 
their beaks, lifting up their heads, and allowing the water to 
run down by its gTavity, would have been specially taught 
by instinct ; but this is not so, for I was most positively 
assured that the chickens of a brood reared by themselves 
generally required their beaks to be pressed into a trough, 
but if there were older chickens present, who had learnt to 
drink, the younger ones imitated their movements, and thus 
acquired the art." 

Upon the whole, then, with reference to the modes 
whereby intelligence operates in modifying instinct, we may 
say that in all cases when it does so, there must first be 
intelligent perception of the desirability of the modification 
on the part of certain individuals, who modify their actions 
accordingly. In some cases the principle of imitation pro- 
bably assists in changing the instinct by inducing other indi- 
viduals of the same species, and living in the same area, to 
follow the example of their more intelligent companions ; or 
the principle of imitation may come in at an earlier stage, 
the habits of one species suggesting to the members of another 
species the modification of an instinct. Lastly, intelligence 
may operate by the intentional tuition of young by their 
parents. 

But perhaps the best evidence of the extreme modification 
which instinct may be made to undergo by the eiFects of 
individual experience, or of changed conditions of life, is that 
which is afforded by the enormous mass of facts to which we 
are naturally led on by some of the cases just given ; I mean 
the facts connected with the domestication of animals. For 
the effects of domestication in modifying instincts are quite 
as strongly shown as are its effects in modifying structures, 
as was long ago observed by Dr. E. Darwin. So important 
and extensive a class of facts, however, require to be con- 
sidered by themselves. I shall therefore now proceed to do 
this without any further special reference to the effects of 
imitation or of education operating upon instinct during the 
lifetime of the individual. 



230 MENTAL EVOLUTION IN ANIMALS. 



CHAPTER XV. 

Instinct (continued). 
Domestication. 

!Feom tlie nature of the case it is not to be expected that we 
should obtain a great variety of instances among wild 
animals of new instincts acquired under human observation, 
seeing that the conditions of their life as a rule remain 
pretty uniform for any periods over which human observa- 
tion can extend. But fortunately, from a time anterior to the 
beginning of history, mankind, in the practice of domestica- 
ting animals, has been engaged on making what we may 
consider a gigantic experiment on this subject. Seeing that 
the animals chosen for this purpose have been bred and 
reared under human care for a series of innumerable genera- 
tions, and that in some cases the members of certain 
" breeds " are persistently selected and trained to perform 
certain kinds of work, we should expect, if instincts arise by 
secondary means in conjunction with primary, to find 
evidence, not only of the dwindling of natural instincts, but 
also of the formation of new and special instincts. For it 
is evident that artificial education and artificial selection by 
man are influences the same in kind, though not in degree, as 
those of natural education and natural selection, to the com- 
bined operation of which our theory ascribes the formation of 
instincts. We might therefore, as I have said, expect to find 
among our domestic animals some evidence of the formation 
of what we may call artificial, or in Mr. Darwin's phraseology, 
domestic instincts. And such evidence we do find. 

Taking first the case of tlie impairment or loss of natural 
instincts, I have already alluded to the striking example 
supplied by the hereditary tameness of domesticated animals. 
]\Iore, however, now remains to be said on this point, for it 



DOMESTICATION. 231 

will be remembered that previously our attention was con- 
fined to cases in which this loss is to be attributed to changed 
experience alone, without the aid of selection, or to primary 
means unassisted by secondary. In this connection I ad- 
duced the cases of the Eabbit and the Duck ; I shall now 
adduce the cases in which artificial selection has probably 
assisted mere disuse in obliterating natural wildness. 

The most remarkable of these instances is perhaps that 
supplied by the Cat, inasmuch as the nearest congener of 
this animal — the wild cat — is the most obstinately untame- 
able of all animals. The case of the Dog, however, is in this 
connection scarcely less remarkable, seeing that fierceness 
and distrust are such constant features in the psychology of 
all the wild races. Probably, too, if there were such an 
animal now in existence as the truly wild Horse, we should 
find its disposition to resemble that of the Zebra, Quagga, or 
Wild Ass, the latter of which, though not so untractable as 
either of the former, is nevertheless a very different animal 
in this respect from our proverbially patient donkey. Simi- 
larly, as Handcock observes, " In the wild state kine possess 
acuteness of sight and smell, and a spirit of fierceness in 
defending their young, which disappear when, by domestica- 
tion, we have reduced them to a condition in which the 
former of these qualities would be of no value, and the latter 
dangerous to them'selves and others." This consideration 
led Handcock to add the shrewd remark, " Upon the whole 
it seems to be established as a principle that, where there 
is no room for the exercise of pure instinct, either by man's 
interposition or otherwise, it will languish, like all the 
natural senses."* 

So much, then, to prove that instinctive wildness is 
eradicated from all species which have been suf&ciently long 
exposed to the influences of domestication. I shall now give 
a few facts to show that the power of domestication thus to 
reduce or destroy the innate tendencies of wild animals 
extends to still more special lines of psychological forma- 
tion. 

Mr. Darwin saysf " All wolves, foxes, jackals, and species 
of the cat genus, when kept tame, are most eager to attack 
poultry, sheep, and pigs ; and this tendency has been found 
incurable in dogs which have been brought home as puppies 

* Zoological Journal, p. 320. f Origin of Species, p. 211. 



232 MENTAL EVOLUTION IN ANIMALS. 

from such countries as Tierra del Fuego and Australia, where 
the savages do not keep these domestic animals.* How 
rarely, on the other hand, do our civilized dogs, even when 
quite young, require to be taught not to attack poultry, sheep, 
and pigs. No doubt they occasionally do make an attack, 
and are then beaten ; and, if not cured, are destroyed ; so 
that habit and some degree of selection have probably con- 
curred in civilizing by inheritance our dogs. On the other 
hand, young chickens have lost, wholly by habit, that fear of 
the dog and cat which no doubt was originally instinctive in 
them ; for I am informed by Captain Hutton that the young 
chickens of the parent stock, the Gallus hankiva, when 
reared in India under a hen, are at first excessively wild. So 
it is with young pheasants reared in England under a hen. 
It is not that chickens have lost all fear, but fear only of dogs 
and cats ; for if the hen gives the danger-chuckle, they will 
run (more especially young turkeys) from under her, and 
conceal themselves in the surrounding thickets." The MS 
adds, " Pigeons are not as constantly kept as poultry, and 
every fancier knows how difficult it is to keep his favourites 
safe from their incorrigible enemy — the cat." 

As additional evidence that instincts may be lost, or as 
Handcock says, " languish " under domestication, it is enough 
to point to the instinct of incubation having become aborted 
in the Spanish hen ; and to the maternal instincts having 
similarly dwindled in cattle in certain parts of Germany, 
where for hundreds of generations it has been the custom to 
remove the calves from the mothers immediately after birth.f 
The same authority says that sheep will allow strange lambs 
to suck them in countries where it has long been the custom 
to change lambs, which is not the case with other sheep, 

* In the MSS detailed evidence on tliis point is given, from which I quote 
the following : — 

" This was the case with a native dog from Australia, whelped on board 
ship, which Sir J. Sebright tried for a year to tame, but which ' if led near 
sheep or poultrv became quite furious.' So again Captain FitzRoy says that 
not one of the many dogs procured from the natives of Tierra del Fuego and 
Patagonia which were brought to England could easily be prevented from 
indulgence in tlie most indiscriminate attack on poultry, young pigs, &c.' 
(Colonel H. Smith, on Doffs, 1810, p. 214; and Sir J. Sebright, on Instinct, 
p. 12. Also Waterton's JSssai/ on Nat. Hist., p. 197, for extreme wildness of 
young pheasants at sight of a dog.)" And the MSS also contain a letter from 
Sir James Wilson, giving Mr. Darwin an account of a tamed Dingo, which 
obstinately persistefl in killing poultry and ducks whenever he got loose. 

t Stuorii, Ueber Racen, &c., 8. 82. 



DOMESTICATION. 233 

Lastly, according to Mr. J. Shaw, " where the dog is valued 
solely for food, as in the Polynesian Islands and China, it is 
described as an extremely stupid animal,"* and White says, 
in his " Natural History of Selborne,"t that these dogs have 
lost some of what we must regard as their strongest instincts, 
for " though they are so strictly carnivorous animals, from 
having been for so many generations fed on vegetable food 
they have lost their instinctive taste for flesh." 

Thus much, then, for what we may call the negative in- 
fluence of domestication, or its power of destroying natural 
instincts. We shall now turn to the still more striking and 
suggestive side of the subject, viz., the positive influence of 
domestication in developing new instincts not natural to the 
species, but artificially produced by accumulative instruction 
through successive generations, combined with selection. And 
here I shall confine myself to the species of domestic animal 
in which these effects have been most conspicuous, viz., the 
Dog. Doubtless the reason why these effects are most con- 
spicuous in the case of this animal is because his utility to 
man has always depended mainly upon his intelligence, so 
that man has here persistently directed the influences of 
domestication towards an artificial shaping of that intelli- 
gence. For it is in this connection of interest to observe 
that the only features in the primitive psychology of the dog 
which have certainly remained unaffected by contact with 
man, are those features which, being neither useful nor harm- 
ful to man, have never been either cultivated or repressed. 
Such is the case, for example, with the instincts of covering 
excrement, rolling in filth, turning round and round to make 
a bed, hiding food, &c.t 

As evidence of the positive influences of domestication on 
the psychology of the dog, I may first draw attention to what 
occurs to me as a very suggestive case. One of the most dis- 

* This sentence occurs as a quotation in a letter by Mr. Shaw to 
Mr. Darwin, but the reference is not supplied. 

t Letter 57. 

X La Malle says that it is not until dogs are ten or twelve months old 
that they begin to bury superfluous food. This, if true, would point to the 
conclusion that the instinct was one lately acquired in the history of the 
wild species, and therefore presumably is not so firmly fixed as the instincts 
of wildness, fierceness, attacking poultry, and so on, which have been so 
completely eradicated by human agency. 



234 MENTAL EVOLUTION IN ANIMALS. 

tinctive peculiarities of the psychology of the dog is the high 
degree in which there are developed the ideas of ownership 
and property — ideas which have of course been bred into 
canine intelligence by man. Most carnivorous animals in 
their wild state have an idea of property as belonging to 
captors, and the manner in which certain predacious Carnivora 
take possession of more or less definite areas as their hunting- 
grounds implies an incipient notion of the same thing. From 
the germ thus supplied by nature the art of man has operated 
in the case of the dog, tiU now the idea of defending his 
master's property has become in this animal truly instinctive. 
Without any training, and even sometimes against training, 
many dogs will bark and fly at strangers passing the gates or 
doors which bound their master's premises. Instances with- 
out number might be multiplied to show the careful vigilance 
of dogs over property entrusted to their charge ; but, as the 
fact is so well known, space need not here be occupied with 
its proof. I shall, however, give one or two observations 
which I myself made in this connection on a terrier which I 
reared from puppyhood, because I am perfectly certain that in 
this case the idea of protecting property was innate or in- 
stinctive, and not due to individual instruction. I have seen 
this dog escort a donkey which had baskets on its back filled 
with apples. Although the dog did not know that he was 
being observed, he accompanied the donkey all the way up a 
long hill for the express purpose of guarding the apples. For 
every time that the donkey turned back his head to take an 
apple out of the baskets, the terrier sprang up and snapped at 
his nose ; and such was the vigilance of the dog that, although 
his companion was keenly desirous of tasting some of the 
fruit, he never allowed him to get a single apple during the 
half hour that they were left together. I have also seen this 
terrier protecting meat from other terriers, which lived in the 
same house with him, and with which he was on the best of 
terms. More curious still, I have seen him seize my wrist- 
bands while they were being worn by a friend to whom I had 
temporarily lent them — no doubt recognizing them as mine 
by his sense of smell, which was exceedingly good. 

Akin to this inborn idea of protecting the property of his 
master, is the idea which the dog has of himself as constitut- 
ing a part of that property — i.e., the idea of ownership as 
extended to himself. That this idea is likewise inborn I have 



DOMESTICATION. 235 

observed in the case of a very young Newfoundland puppy 
which was given to me when scarcely able to toddle, but 
which nevertheless at once followed me through tolerably 
crowded streets. Yet this puppy can scarcely have known 
me from any of the other persons he met, and therefore he 
can only have followed me from his instinctive idea of 
ownership, and his consequent fear of getting lost. This 
abstract idea of ownership is well developed in many, if not 
in most dogs ; so that, for instance, it is not at all an unusual 
thing to find that if a master consigns his dog to the care of 
a friend previously unknown to the animal, the latter will 
feel quite safe under the charge of one whom he has seen to 
be his master's friend. For the time being the allegiance of 
the animal is transferred, and he feels to his master's friend, 
not as to a stranger, but as to a deputed owner. It is not, I 
think, improbable that what appears to be the acquired in- 
stinct of barking is, as it were, an offshoot from this acquired 
instinct of property, and of protecting self as property, by 
drawing the attention of a master to the approach of strangers 
or enemies. 

Mr. Darwin has made a strong point of other and still 
more special " domestic instincts " of the dog, which are 
perhaps even more interesting than those above mentioned, 
from the fact of their having been intentionally bred into the 
animals by continued training with selection ; I allude to the 
instincts of the sheep-dog, retriever, and pointer. He briefly 
alludes to these cases in the " Origin of Species " (p. 209), 
but dwells more fully upon them in his uncondensed MSS, 
from which therefore I shall quote. 

" Look at the several breeds of Dogs, and see what dif- 
ferent tendencies are inherited, many of which caimot, from 
being utterly useless to the animal, have been inherited from 
their one or several wild prototypes. I have talked with 
several intelligent Scotch shepherds, and they were unanimous 
in saying that occasionally a young sheep dog without any 
instruction will naturally take to run round the flock, and 
that all thorough-bred dogs can be easily taught to do this ; 
and although they intensely enjoy the exercise of their innate 
pugnacity, yet they do not worry the sheep, as any wild 
canine animal of the same size would do. Look again at the 
Eetriever, which so naturally takes to bringing back any 
object to his master. The Eev. W. D. Fox informs me that 



236 MENTAL EVOLUTION IN ANIMALS. 

he taught in a single morning a Retriever six months old to 
fetch and carry well, and in a second morning to return on 
the path to search for an object left purposely behind and not 
seen by the dog. Yet I know from experience how difficult 
it is to teach the habit at least to terriers. 

" Let us consider one other case, though so often quoted, 
that of the Pointer. I have myself gone out with a young 
dog for the first time, and his innate tendency was shown in 
a ludicrous manner, for he pointed fixedly not only at the 
scent of game, but at sheep and large white stones ; and 
when he found a lark's nest, we were actually compelled to 
carry him along; he backed the other dogs. . . . The 
silence of Pointers, also, is the more remarkable, as all who 
have studied these dogs agree in classing them as a sub-breed 
of Hound, which gives tongue so freely. But the tendency 
in the young Pointer to back other dogs, or to point without 
perceiving any scent of game when they see other dogs 
point, is perhaps the most singular part of his inborn pro- 
pensities.* 

" Now if we were to see one kind of wolf, in a state of 
nature, running round a herd of deer, and skilfully driving 
them whither he liked, and another species of wolf, instead 
of chasmg its prey, standing silent and motionless on the 
scent for more than half an hour with the other wolves of the 
pack all assuming the same statue-like attitude and cautiously 
approaching, we should surely call these actions instinctive. 
The chief characteristics of instinct seem to be fulfilled in the 
pointer. A young dog cannot be supposed to know why he 
points, any more than a butterfly why it lays its eggs on a 

cabbage It seems to me to make no essential 

difference that pointing is of no use to the dog, only to man ; 
for the habit has been acquired through artificial selection 
and training for the good of man, whereas ordinary instincts 
are acquired through natural selection and training exclu- 
sively for the animal's own good. The young pointer often 
points without any instruction, imitation, or experience ; 
though, no doubt, as we have also seen sometimes to be the 

* " With respect to the inherited tendency to back, see St. John's 
Wild Sport of the Highlands, 1816, p. 116 ; Colonel Hutchinson on Dog 
Sreaking, 1850, p. 14t; and Blaine, Eacij.of Rural Sports, p. 791. — Besides 
the tendency to point, pointers inherit a peculiar manner of quartering their 
ground." 



DOMESTICATION. 237 

case with true instincts, he often profits by these aids. More- 
over, each breed of dogs delights in following his inborn 
propensity. 

" The most important distinction between pointing, &c., 
and a true instinct, is that the former is less strictly inherited, 
and varies greatly in the degree of its inborn perfection : 
this, however, is just what one might have expected; for 
both mental and corporeal characters are less true in domestic 
animals than in those in a state of nature, inasmuch as their 
conditions of life are less constant and man's selection and 
training far less uniform, and have been continued for an 
incomparably shorter period, than is the case in nature's pro- 
ductions." 

Although the familiar fact of young pointers pointing 
instinctively does not need further corroboration, I shall quote 
a brief passage from the paper of Mr. Andrew Knight on 
" Hereditary Instincts,"* because it shows, as in the case of 
" backing," to what extreme nicety of detail the hereditary 
knowledge may in some cases extend. 

" It is well known that very young pointers, of slow and 
indolent breeds, will point partridges without any previous 
instruction or practice. I took one of them to a spot where 
I had just seen a covey of small partridges alight in August, 
and amongst them I threw a piece of bread to induce the dog 
to move from my heels, which it had very little disposition 
to do at any time, except in search of something to eat. On 
getting among the partridges, and perceiving the scent of 
them, its eyes became suddenly fixed, and its muscles rigid, 
and it stood trembling with anxiety for several minutes. I 
then caused the birds to take wing, at sight of which it 
exhibited strong symptoms of fear and none of pleasure. A 
young Springing Spaniel, under the same circumstances, 
would have displayed much joy and exultation, and I do not 
doubt but that the young pointer would have done so too, if 
none of its ancestry had ever been beaten for springing 
partridges improperly." 

From this same paper I must quote the following and 
more or less analogous cases : — 

" A young Terrier whose parents had been much employed 
in destroying Polecats, and a young Springing Spaniel whose 

* Phil. Trans., 1837, p. 367, 
11 



238 MENTAL EVOLUTION IN ANIMALS. 

ancestry through many generations had been employed in 
finding Woodcocks were reared together as companions, the 
Terrier not having been permitted to see a Polecat or any 
other animal of similar character, and the Spaniel having 
been prevented seeing a Woodcock or other kind of game. 
The Terrier evinced, as soon as it perceived the scent of 
the Polecat, very violent anger ; and as soon as it saw the 
Polecat attacked it with the same degree of fury as its 
parents would have done. The young Spaniel, on the con- 
trary, looked on with indifference, but it pursued the first 
Woodcock it ever saw with joy and exultation, of which its 
companion, the Terrier, did not in any degree partake. . . 
In several instances young and wholly inexperienced dogs 
appeared very nearly as expert in finding Woodcocks as their 
experienced parents. 

"Woodcocks are driven in frosty weather, as is well 
known, to seek their food in springs and rills of unfrozen 
water, and I found that my old dogs knew about as well as I 
did the degree of frost which would drive the woodcocks to 
such places ; and this knowledge proved very troublesome to 
me, for I could not sufficiently restrain them. I therefore left 
the old experienced dogs at home, and took only the wholly 
inexperienced young dogs ; but to my astonishment some of 
them, in several instances, confined themselves as closely to 
the unfrozen grounds as their parents would have done. 
When I first observed this I suspected that woodcocks might 
have been upon the unfrozen ground during the preceding 
night, but I could not discover (as I think I should have 
done had this been the case) any traces of their having been 
there ; and as I could not do so, I was led to conclude that 
the young dogs were guided by feelings and propensities 
similar to those of their parents." 

Elsewhere in his essay this author remarks, " It may, I 
think, be reasonably doubted whether any dog having the 
habits and propensities of the Springing Spaniel would ever 
have been known, if the art of shooting birds on the wing 
had not been acquired." 

Lastly, with reference to those artificial instincts of the 
dog, which are of this highly specialized nature — amounting, 
in fact, to hereditary memory of a most minute kind — I 
may allude to a remark made by Professor Hermann, that 
sporting dogs appear, when first taken out to hunt, and there- 



DOMESTICATION. 239 

fore previous to any individual experience, to anticipate the 
effects of a gun in bringing down a bird.* 

Suggestive, however, as is the formation Ivy man of such 
special canine instincts as we have now considered, we have 
in them only, as it were, small details of the modification 
which human agency has produced in the psychology of the 
dog. It is, indeed, not more true that man has in a sense 
created the remarkable structure of the greyhound or the 
bulldog, than that he has implanted the no less remarkable 
instincts of the pointer or the retriever ; but we should gain 
a very inadequate conception of the profound influence which 
he has exercised in moulding the mind of this animal were 
we to confine our attention to such special cases as these. 

If we contrast the psychology of " the friend of man " 
with that of any of the wild breeds, we see at once, not only 
that the animal has had many of its natural instincts sup- 
pressed and many artificial instincts imposed, but also that it 
has acquired, as Sir J. Sebright has observed, "an instinctive 
love of man." But the general affection, faithfulness, and 
docility of the dog, are too proverbial to need special exposi- 
tion. We have merely to observe that these qualities, so unlike 
anything with which we meet in wolves, foxes, jackals, and 
wild dogs generally, can only be attributed to prolonged 
contact with, and selection by, his human masters ; so that 
as the domestic dog is at present constituted these artificially 
imposed qualities usually lead the animal to entertain higher 
affection and faithfulness towards man than towards its own 
kind. It may not be superfluous in this connection again to 
point out that among wild animals we do not unfrequently 
find a disposition to associate with members of other species, 
even when no actual benefit arises from the association ; and 
in this accidental or useless proclivity we may distinguish 
the germ which in the case of the dog has been cultured into 
what we see — amply justifying the remark of the old writer 
quoted by Darwin, " A dog is the only thing on this earth 
that luvs you more than he luvs himself." 

Not only affection, faithfulness, and docility, but likewise 
all other emotional qualities of the dog which are useful to 
man have been developed by man to the extraordinary 
degree which we observe. It would be superfluous to cite, 

• Eandtuuh der rhysiologie, Bel. II, Theil II, pp. 282-3. 



240 MENTAL EVOLUTION IN ANIMALS. 

or even to give references to cases illustrating the exalted 
level to which sympathy has attained. This, together with 
the intelligent affection from which it springs, gives rise to a 
love of approbation and dread of blame, which as far as they 
go are in no way distinguisliable from the same feelings as 
they occur in man himself. To this subject I shall have to 
return when in my next work we come to treat of the genesis 
of Conscience. 

Again, as Mr. Grant Allen has pointed out, the sense of 
dependence, which a dog shows is very instructive. " The 
original dog, who was a wolf or something very like it, could 
not have had any such artificial feeling. He was an inde- 
pendent, self-reliant animal. . . . But at least as early 
as the days of the Danish shell-mounds, perhaps thousands 
of years earlier, man had learned to tame the dog." There- 
fore, as a result of continuous education, selection, and breed- 
ing, although " among a few dogs, like those of Constanti- 
nople, the instinct may have died out by disuse, .... 
when a dog is brought up from puppyhood under a master, 
the instinct is fully and freely developed, and the masterless 
condition is thenceforth for him a thwarting and disappoint- 
ing of all his natural feehngs and affections."* 

Indeed, so strong are the combined effects of long-con- 
tinued breeding and individual education, that they may 
overcome the strongest of natural instincts and desires — 
witness a dog which will starve rather than steal, and also 
the recorded cases in which even the maternal instinct has 
been overborne by the desire of serving a master. To give 
only one example of this surprising fact, I shall quote from 
the " Shepherd's Calendar " of the poet Hogg : — 

A coUie belonged to a man named Steele, who was in 
the habit of consigning sheep to her charge without super- 
vision. On one occasion, says Hogg, "whether Steele 
remained behind or took another road, I know not, but, on 
arriving home late in the evening, he was astonished to hear 
that his faithful animal had never made her appearance with 
the drove. He and his son, or servant, instantly prepared to 
set out by different paths in search of her, but on their going 
out into the streets, there was she coming with the drove, not 
one missing, and, marvellous to relate, she was carrying a 
young pup in her mouth. She had been taken in travail on 

* Evolutionist Ahmad, p. 183, et seq. 



DOMESTICATION. 241 

the hills, and how the poor beast had contrived to manage 
her drove in her state of suffering is beyond human calcula- 
tion, for her road lay through sheep the whole way. Her 
master's heart smote him when he saw what she had suffered 
and effected; but she was nothing daunted, and, having 
deposited her young one in a place of safety, she again set 
out full speed to the hills and brought another and another, 
till she brought her whole litter, one by one ; but the last one 
was dead." 

There is still one respect — and this a most suggestive one 
— in which artificial instincts resemble natural instincts, over 
and above that of obliteration by disuse or acquirement by 
training and selection. In order to show this it will be suffi- 
cient to quote the following passage from Mr. Darwin's MSS, 
part of which has already been published in the " Variation 
of Animals and Plants under Domestication " (vol. i, 

" It is well known that when two distinct species are 
crossed, the instincts are curiously blended, and vary in the 
successive generations, just like corporeal structures. To 
give an example : a dog kept by Jenner (Hunter's " Animal 
Economy," p. 325), which was grandchild, or had a quarter- 
blood of the jackal in it, was easily startled, was inattentive 
to the whistle, and would steal into fields and catch mice in 
a peculiar manner. Now I could give numerous examples of 
crosses between breeds of dogs, both having artificial instincts, 
in which these instincts have been most curiously blended, 
as between the Scotch and English sheep-dog, pointer and 
setter : the effect, moreover, of such crosses can sometimes be 
traced for very many generations, as in the courage acquired 
by Lord Orford's famous greyhounds from a single cross with 
the bull-dog (" Youatt on the Dog," p. 31). On the other 
hand, a dash of the greyhound will give a family of sheep- 
dogs a tendency to hunt hares, as I was assured by an intel- 
ligent shepherd." 

Our d 'posteriori proof of Proposition YII is now concluded, 
and with its proof our considerations on the origin and 
development of instinct are drawing to a close. Eor we have 
now seen that instincts may arise under the influence of 
natural selection alone, under that of lapsing intelligence 
alone, or under both these influences combmed. And in 



242 MENTAL EVOLUTION IN ANIMALS. 

proving that habits intelligently acquired may, like habits 
acquired without intelligence, be inherited, we have also 
proved, as in the analogous case of primary instincts, that 
these habits in the course of generations may vary, that their 
variations may be inherited, and that the favourable variations 
may be fixed and further intensified by natural or artificial 
selection. Tor it is only by granting all these statements 
that we can possibly explain many of the foregoing facts. 
Clearly man could never have produced the artificial instincts 
of the dog, unless he had practically recognized the facts of 
variabihty and inheritance— a recognition which is forcibly 
expressed in the immense difference between the market 
value of a pointer or setter of important pedigree, and a 
pointer or setter whose parentage is unknown. As Thompson 
well says : — " It would be necessary to recommence the busi- 
ness of training with each successive generation, if the bodily 
and mental changes which the animals have undergone in the 
continued process of domestication had not become so en- 
grafted as to be propagated with them. These acquired 
characteristics have gathered fresh strength in each succeed- 
ing generation, till at length they have assumed a permanent 
stamp." And if artificial selection is of such high importance 
in the formation of domestic instincts, much more must 
natural selection be of importance in tlie formation of natural 
instincts. 



LOCAL AND SPECIFIC VARIETIES OF INSTINCT. 243 



CHAPTEE XVI. 

Instinct (continued). 

Local and Specific Varieties of Instinct. 

I HAVE now shown that instincts may arise through the 
influence of natural selection, or of lapsing intelligence, or of 
both these principles combined ; and that even fuUy formed 
instincts are liable to change when changing circumstances 
require. The most striking evidence on this head, or that of 
the mutability of fully formed instincts, is perhaps the 
evidence given in the last chapter, showing the influence of 
domestication both in obliterating the strongest of natural 
and in creating the most fantastic of artificial instincts. But 
inasmuch as we have previously seen that any considerable 
change in the circumstances to which an instinct is appro- 
priate, is apt to throw the machinery of that instinct out of 
gear, the evidence of the mutability of instinct drawn from 
the effects of domestication may be open to the criticism that 
the changes produced are of an unnatural character, or due to 
an impairment of the normal apparatus of instinct. I do not 
myself think that if this criticism were raised it would be 
one of any force, seeing that domestication not only has the 
negative effect of impairing or destroying natural instincts, 
but also, as I have said, the positive effect of creating artifi- 
cial instincts. Still it is desirable to supplement the evidence 
drawn from the facts of domestication with further evidence 
draAvn from the field of nature; for here, at least, no criticism 
of the kind which I have suggested can be advanced. I pro- 
pose, therefore, in this chapter to consider all the facts which 
I have been able to collect, tending to show that among 
animals in a state of nature instincts undergo transformations 
which are precisely analogous to those that they undergo 



244 MENTAL EVOLUTION IN ANIMALS. 

among animals in a state of domestication. The kind of 
evidence on which I rely to show this is two-fold — 1st the 
occurrence among wild animals of local varieties of instinct, 
and 2nd the similar occurrence of specific varieties. 

Zocal Varieties of Instinct. 

Under the first of these two divisions I shall seek to show 
that the mutability of instinct finds a most marked and sug- 
gestive expression in certain cases where wild animals of the 
same species living in different parts of the world (and there- 
fore exposed to different environments), present differences in 
their instinctive endowments of a marked and constant kind. 
One class of such cases has already been given with reference 
to the acquisition of an instinctive fear of man by those 
animals in a state of nature which inhabit localities frequented 
by man : but as the subject appears to me an important one 
— seeing that a definite local variety is on its way to becom- 
ing a new instinct — I shall now give all the best instances 
which I have been able to collect. 

Beginning with insects, Kirby and Spence state on the 
authority of Sturm that the dung-beetle, which rolls up 
pellets or little balls of dung, saves itself the trouble of 
making the pellets when it happens to live on sheep- 
pastures; for it then "avails itself of the pellet-shaped balls 
ready made to its hands which the excrement of the sheep 
supplies." Here we have intelligent adaptation to peculiar 
conditions, and so the case might have been quoted as one of 
the plasticity of instinct ; but as sheep-pastures are definite 
local areas, I have quoted it as a case of the local variation of 
instinct. All cases of such local variation must have some 
determining cause, and doubtless most frequently this cause 
is intelligent adaptation to peculiar local conditions. There- 
fore I have chosen this case to lead off with just because it 
might equally well be quoted in this or in the previous 
cliHpter. 

Again it is stated by Lonbierc, in his history of Siam, 
'• 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." And Forel 
states a closely similar fact with reference to a species of 
European ant, Zasius accrhorum, which on the plains is never 



LOCAL AND SPECIFIC VAEIETIES OF INSTINCT. 245 

found to build under stones, while in tlie Alps it frequently 
builds under the same stones as the Myrmica. 

With regard to Bees, it appears that both in Australia 
and California, the hive-bees when introduced " retain their 
industrious habits only for the first two or three years. After 
that time they gradually cease to collect honey till they 
become wholly idle."* Again, Mr. Packard, jun., records 
some observationsf which were made by the Eev. L. Thomp- 
son, whom he designates " a careful observer," of bees {Apis 
7)idlifica) eating moths which were entrapped in certain 
iiowers. On the fact being communicated to Mr. Darwin, he 
wrote, that he " had never heard of bees being in any way 
carnivorous, and the fact is to me incredible. Is it possible 
that the bees opened the bodies of the Flusia to suck the 
nectar contained in their bodies ? Such a degree of reason 
would require confirmation, and would be very wonderful." 
But whatever the object of the bees may have been, their 
actions, which are described as "suddenly darting" and 
" furious," certainly display some marked variation of instinct 
under the guidance of intelligence. Moreover, the explana- 
tion entertained by Messrs. Thompson and Packard — viz., 
that the bees were partly carnivorous, is perhaps not so 
" incredible " as it appeared to Mr. Darwin, if we remember 
that wasps are unquestionably apt to develop carnivorous 
tastes.l 

Turning now to local variations of instinct in Birds, I 
may first allude to the following instances in the Appendix, 
which although not adduced in this connection by Mr. 
Darwin, are no less apposite to it. 

" It is notorious that the same species of bird has slightly 
different vocal powers in different districts ; and an excellent 
observer remarks, ' an Irish covey of partridges springs with- 
out uttering a call, whilst on the opposite coast the Scotch 
covey shrieks with all its might when sprung.'§ Bechstein 
says that from many years' experience he is certain that in 

* Animal IntelUgenee, p. 188, wliere see for references to Dr. E. Darwin, 
Kirby and Spence, and later writers on this matter. 

t American Naturalist, Jan. 1880. 

t See, e.g., Nature, vol. xxi, pp. 417, 494, 538, and 563, detailing obser- 
vations of the fact by Sir D. Wedderburn, Messrs. Newall, F.K..S., Lewis 
Bod, and W. G. Smith. 

§ W. Thompson, in Nat. Sist. Ireland, vol. ii, p. 65, says he has observed 
this, and that it is well known to sportsmen. 



246 MENTAL EVOLUTION IN ANIMALS, 

the Nightingale a tendency to sing in the middle of the 
night or in the day runs in families and is strictly in- 
herited."* 

Professor Newton informs me that the Eing-plover on 
the extensive sand-dunes of Norfolk and Suffolk habitually 
displays a very curious and instructive case. These birds 
naturally build on the sea-shore, depositing their eggs in a 
hollow which they scoop out in the shingle. The sea has 
retreated for miles from the extensive sand-dunes in question, 
which have become covered with grass. Apparently the 
Eing-plovers have gone on breeding for numberless genera- 
tions on the site which was at one time the sea-coast, the 
distance between them and the sea having therefore gradually 
increased more and more.f Hence the birds are now living 
on wide grassy surfaces instead of on shingle, but their 
instinct of laying their eggs on stones remains ; so that after 
having scooped out a hollow in the ground, they collect small 
stones from all quarters and deposit them in the hollow. This 
has the effect of rendering their nests very conspicuous, and 
the fact shows in a striking way how a fixed ancestral instinct 
may, while in the main persisting under changed conditions 
of life, nevertheless so vary in reference to these changed 
conditions as to constitute the beginning of a new instinct. 

For further instances of local variation in the instincts of 
nest-building, I may in this connection again refer to the 
highly instructive cases previously mentioned in illus- 
tration of the plasticity of instinct under the moulding 
influence of intelligence.^ I allude to the fact that on the 
American Continent various species of birds — notably a kind 
of Owl, a Blue-bird, the Pewit Flycatcher, several species 
of Wren, and nearly all the species of Swallow — have 
adapted the structure of their nests to the artificial nesting- 
places provided by man, in just the same way (though more 
gradually and on a much larger scale) as did the colony of 
Palm-swifts in Jamaica. But with still more special refer- 

* Stuben- Vogel, 1840, s. 3i!3 ; see on different powers of singing in dif- 
ferent places, 8. 205 and 265. 

t That this is the explanation is not merely probable oi, priori, but 
receives additional corroboration from the fact that these same sand-dunes 
are now the habitat of a species of lepidopterous insect which elsewhere is 
found upon the coast. 

X See above, p. 210. Compare also many of the cases given in the 
Appendix. 



LOCAL AND SPECIFIC VARIETIES OF INSTINCT. 247 

ence to the local variation of instinct, I may here quote a 
further statement from Captain Coues' work previously- 
cited; for it shows that even on different parts of the 
American Continent the same species of birds exhibit these 
differences in their mode of nest- building. He says : — " There 
is no question of the fact that some of the Swallows which in 
the East now invariably avail themselves of the accommo- 
dation man furnishes, in the West live still in holes in 
trees, rocks, or the ground ; " and he proceeds to give several 
special instances.* Lastly, the fact has already been noted 
that House-sparrows exhibit a similar local variation of 
instinct wherever they come into contact with the dwellings 
of man.t 

Passing on now to other animals, we find several instruc- 
tive cases of the local variation of instinct among the Mam- 
malia. Thus the curious habit has been observed among 
cattle inhabiting certain districts of sucking bones. Arch- 
bishop Whately made this the subject of a communication 
to the Dublin Natural History Society many years ago. 
Eecently it has been observed by Mr. Donovan of cattle in 
Natal,$ and by Mr. Le Conte, of cattle in the United States. § 
Probably this habit is induced by the absence of some con- 
stituent of food in the grass which is supplied by the bones, 
and therefore if the habit happened to prove beneficial to the 
cattle (instead of deleterious as Whately asserts), it is easy 
to see that cattle in a state of nature might become trans- 
muted from herbivorous to omnivorous, or even purely car- 
nivorous. Probably the ancestors of the Pig have passed 
through the former of these stages. On the other hand, the 
Bear seems to be in process of becoming omnivorous from 
the contrary direction — being carnivorous in its affinities, but 
not infrequently adopting the habit of eating grass and herbs. 

And in this connection I may refer to an interesting case 
of transition from herbivorous to carnivorous habits which 
was published at the Academy of Natural Science of Phila- 

* Op. cit., p. 394. This fact, I think, tends to confirm the statement of 
Mr. Edward {Zool., p. 6842) that on the coast of Eanffshire the house- 
swallow presents a local instinct of building in caves and on projecting rocks. 

t When house-sparrows build in trees — wliich they occasionally do and 
which must be regarded as reversion to primitive instinct — " the structure is 
very large, more than a yard in circumference, and covered with a dome." 
{YarreVs British Birds, 4th Ed., Pt. X, p. 90.) 

X Nature, vol, xx, p. 457. § Ibid. 



248 MENTAL EVOLUTION IN ANIMALS. 

delphia on February IStli, 1873, by Mr. W. K. G. Gentry. A 
rodent popularly known as the Chickaree (Scinus huclsonius), 
which like most of its kind is normally herbivorous, has 
adopted in the neighbourhood of Mount Airy a habit 
common among the Mustelidce, of climbing trees for the pur- 
pose of catching birds and sucking their blood. Mr. Gentry 
suggests that this transition from herbivorous to carnivorous 
habits may have arisen from the propensity shown by some 
squirrels of sucking the eggs of birds — the passage from this 
habit to that of sucking the blood of birds being but small. 
Lastly, in this connection I may adduce a precisely analogous 
case of a marked local variation of instinct taking place in a 
species of bird. 

Mr. I. H. Potts, writing from Ohinitahi to " Nature" (Feb- 
ruary 1st, 1872), says that the mountain parrot {Nestor 
notabilis) was then exhibiting a "progressive development of 
change in habits from the simple tastes of a honey-eater to 
the savageness of a tearer of flesh." For " the birds come in 
flocks, single out a sheep at random, and each alighting on 
its back in turn, tears out the wool, and makes the sheep 
bleed, till the animal runs away from the rest of the sheep. 
The birds then pursue it, and force it to run about till it 
becomes stupid and exhausted. If in that state it throws 
itself down, and lies as much as possible on its back to keep 
the birds from picking the part attacked, they then pick a 
fresh hole in its side, and the sheep, when so set upon, in some 
instances dies. . . . Here we have an indigenous species 
making use of a recently imported aid for subsistence, at the 
cost of a vast change in its natural habits." Since this 
account was written the change of habits in question has 
grown to become a very serious matter to the sheep-farmers. 
It appears that the birds prefer the fat parts of their victims, 
and have learnt to bore into the abdominal cavity straight 
down upon the fat of the kidneys, thus of course kilhng the 
sheep. 

Another case of local variation of instinct is furnished by 
the statement of Adamson, that in the island of Sor rabbits 
do not burrow. This statement, however, although accepted 
by Dr. E. Darwin, has not, so far as I know, been either con- 
firmed or refuted. But with reference to variations in the 
instinct of burrowing, I may allude with more confidence to 
the case given by Mr. Darwin in the Appendix on the 



LOCAL AND SPECIFIC VARIETIES OF INSTINCT. 249 

authority of Dr. Andrew Smith, viz., " that in the uninhabited 
parts of South Africa the hy?enas do not live in burrows, 
whilst in the inhabited and disturbed parts they do. Several 
mammals and birds usually inhabit burrows made by other 
species, but when such do not exist they excavate their own 
habitations." 

In " Animal Intelligence " I stated, under the authority 
of Dr. Newbury's Keport on the Zoology of Oregon and 
California, that the beavers in those districts exhibit the 
peculiarity of never constructing dams, and seeing that the 
building of these structures may be regarded as one of the 
strongest instincts manifested by the species, I supposed 
the failure of the Oregon and Californian beavers in mani- 
festing this instinct to constitute a remarkable case of the 
local variation of instinct. Professor Moseley, however, who 
has travelled in Oregon, now writes me that this absence of 
beaver dams is in his opinion due simply to the severity with 
which the animals are trapped. "What few beavers that 
remain are too constantly liable to interruption to be able to 
construct dams, or for this to be worth their while. They thus 
live a more or less vagrant life about the streams." It will be 
observed, however, that Professor Moseley speaks of " the 
few beavers that remain," whereas Dr. Newbury says of the 
same districts : — " We found the beavers in numbers of which, 
when applied to beavers, I had no conception." Therefore 
I infer that since the time when Dr. Newbury's Eeport was 
published, the number of the beavers must have been greatly 
reduced by trapping. But if so, at the time when the Eeport 
was published. Professor Moseley's explanation of the absence 
of dams can scarcely have applied to the facts of the case. 
Hence, I am still disposed to think that we have in this case 
an instance of the local variation of instinct — seeing that the 
variation of habit was remarkable even before the introduc- 
tion of the disturbing elements to which Professor Moseley 
now alludes. Be this as it may, however, it is certain that 
the solitary beavers of Europe present a striking local varia- 
tion of instinct, not only in having lost their social habits, 
but also in having ceased to build either lodges or dams. 

The last instance of the local variation of instinct which 

I have to adduce is one which has already attracted a good 

deal of attention ; I refer to the barking of dogs.* The habit 

* A somewhat analogous instance seems to be supplied by the "cat-a- 



250 MENTAL EVOLUTION IN ANIMALS. 

of barking, although perhaps acquired as a result of domesti- 
cation, is so innate and general among most of the breeds, 
that it deserves to be regarded as an instinct. Yet Ulloa 
noticed that in Juan Fernandez the dogs did not attempt to 
bark till taught to do so by the importation of some dogs 
from Europe — their first attempts being strange and un- 
natural. Linnaeus records that tlie dogs of South America 
did not bark at strangers. Hancock says that European 
dogs when conveyed to Guinea " in three or four generations 
cease to bark, and only howl like the dogs natives of that 
coast." Lastly, it is now well known that the dogs of 
Labrador are silent as to barking. So that the habit of bark- 
ing, which is so general among domestic dogs as to be of the 
nature of an instinct, is nevertheless seen to vary with 
geographical position. 

Specific Variations of Instinct. 

To the above instances of the local variations of instinct, 
I shall now add a few cases of what we may call specific 
variations of instinct — that is to say, instincts which occur in 
a species of a character strikingly different from the instincts 
which occur in the rest of the genus. After what has been 
said on the local A^ariations of instinct, the attesting value of 
the cases which we are about to consider must be evident. 
For we should expect that if the conditions which determine 
a local variation of instinct are constant over a sufficient 
length of time, the variation should become fixed by here- 
dity, and so give rise to a change of instinct in the species 
affected — which change ought to become observable in the 
contrast exhibited by the instincts of this species and those 
of the rest of its allies. This head of evidence becomes of 
special value when we remember that it is the nearest 
approach we can hope to obtain of anything resembling a 
palaeontology of instincts. Instincts, unlike structures, do 
not occur in a fossil state, and therefore in the course of their 
modification they do not leave behind them any permanent 
record, or tangible evidence, of their transformations. But 
we obtain evidence of transformation almost as conclusive in 
the cases to which I now allude; for if a living species 

wallings" of cats; for, accoi'ding to Roulin (quoted by Dr. Carpenter in 
Contemp. Rev., voL xxi, p. 311), the domeatic cata in South America do not 
make tliese sounds. 



LOCAL AND SPECIFIC VARIETIES OF INSTINCT, 251 

inhabiting a certain restricted area exhibits a marked depar- 
ture from the instincts elsewhere characteristic of its genus, 
we can scarcely question that the departure is indeed a 
departure — i.e., that originally the instincts were the same 
as those occurring in the rest of the genus, but that owing to 
peculiar local conditions, local variations of instinct arose 
and were continued till they became hereditary, and so led 
to a parting aivay of the instincts of this species from those 
of its allies,* 

For the sake of brevity I shall here confine my instances 
to those which may be drawn from Birds. 

The following concise statement of facts relating to the 
strong instinct of parasitism in the only two genera of birds 
where it is known to occur, is quoted from an Editorial note 
in "Land and Water" (Sep. 7, 1867), and displays very 
remarkable and instructive cross-relations as regards the 
existence and absence of this instinct in the sundry species 
composing these two genera, 

" The only non-cuculine genus of birds known up to the 
present time, which has the habit of entrusting its egg to the 
charge of strangers, is that of the cow-buntings {Molothrus), 
and the parasitic habit of M. pecoris of North America has 
been amply described by the ornithologists cited by our 
correspondent. There are several other species of this genus, 
and the same parasitic habit was observed in another of them 
by Mr. Darwin. The Molothri are birds belonging to the 
great American family of Cassicidce, which corresponds to 
that of Stiirnidm in the Old World; and they are nearly 
akin to the troopials (Agelaius). It is remarkable that not 
any of the various American Cucididoe are parasitic ; whereas 
several genera of this family inhabiting the major continent 
and its islands, with Australia, are now well known to be so. 

* From the above remarks it will appear tliat I do not agree witli 
Mr. Darwin in his view, expressed in the Api^endix, that cases of specific 
variation of instinct are difficulties in the way of his theory of the gi-adual 
development or evolution of instincts. On the contrary, for the reasons 
given above, I regard such cases as corroborations of this theory. The 
source of this difference of opinion is, that while Mr. Darwin is above all 
things anxious to find evidence of connecting links in the formation of an 
instinct, I feel that to expect such evidence in every case of instinct would 
be unreasonable, if not inconsistent with the theory that innumerable in- 
stincts owe their present existence to the destruction through natural selec- 
tion of the animals which presented them in a lesser degree of perfection. I 
(shall recur to this point in a future chapter. 



252 MENTAL EVOLUTION IN ANIMALS, 

First, there are the very numerous species of true Cuculus, 
with its immediate sub-divisions, inhabitants chiefly of 
Southern Asia, Africa, and Australia. Secondly, the crested 
cuckoos (Coccystes), exemplified by C. glandarius, which is 
common enough in Spain, and has been known to stray into 
this country. This bird deposits its eggs in the nests of mag- 
pies and crows. Another species (C. melanoleiicus), which is 
very common in India, selects for this purpose the nests of a 
particularly noisy and familiar group of birds in that part of 
the world, dften called * dirt-birds ' {Malacocercus) ; and as 
the latter lay a spotless blue egg, similar in colour to that of 
the hedge-chanter {Accentor modularis) of Europe, the egg of 
the particular cuckoo which seeks their nests is of a nearly 
similar spotless greenish-blue colour. Another very common 
Indian bird of this family is the koel {Eudynamis orientalis), 
the male of which is coal-black, with a ruby eye, and the 
female beautifully speckled. A pair, in fine condition, may 
now be seen in one of the aviaries in the Zoological Gardens. 
The Indian koel invariably deposits its egg in a crow's nest, 
and the egg is not unlike that of a crow in its colouring and 
markings. Several other species of koel inhabit the Asiatic 
islands, and there is one in Australia ; and as the koels are 
not migratory birds, it follows that the parasitic habit is in- 
dependent of any migratory necessity. That extraordinary 
cuculine bird, the Australian channel-bill {Scythrops novce- 
hollandice), is known to be parasitic, for the young have been 
repeatedly seen tended and fed by birds of other species ; and 
therefore it is a lapsus pennce on the part of Mr. Gould, in 
his ' Handbook of the Birds of Australia,' describing a speci- 
men of it as having been an ' incubating female ! " But the 
coucals {Centropus), very common and conspicuous Dirds in 
Southern Asia, Africa, and Australia, are not parasitic ; 
neither, we have reason to believe, are the extensive malkoha 
series {Phcenicophaus and kindred genera), which inhabit the 
same geographical area. Among the American Cucididce, the 
species of Coccyzus are nearly akin to the crested cuckoos 
{Coccystes) of the major continent; and these, like the para- 
sitic Cucididce, produce their eggs at considerable intervals, 
so that eggs and young of different ages are found in the 
same nest ; while more advanced young, that had quitted the 
nest, are still fed by their parents while keeping to the 
immediate vicinity of the nest ; as may likewise be observed 



LOCAL AND SPECIFIC VARIETIES OF INSTINCT. 253 

of the screech-owls (Strix, as now limited). In the ani 
{Crotophaga) , which have much in common with the coucals 
of the major continent, while in other respects their habits 
are very peculiar for birds of this family, ' an immense nest 
of basket-work ' is formed by the united labours of a flock of 
them, usually on a high tree, where 'many parents bring 
forth and educate a common family.' Mr. llichard Hill, 
whose statements in Jamaican ornithology are worthy of 
unlimited confidence, writes Mr. Gosse, observes : ' Some 
half-dozen of them together build but one nest, which is large 
and capacious enough for them to resort to in common, and 
to rear their young ones together.' All of these diversified 
facts must be borne in mind by naturalists who would try to 
assign a reason for the parasitic habits of various Cuculidce, as 
also those of the ' cow-buntings,' which have no other trait in 
common with the parasitic genera of Cuculidce." 

The Upland Goose of South America furnishes an admir- 
able case of a fixed specific variation of instinct. These birds 
are true geese with well webbed feet ; yet they never enter 
the water except perhaps for a short time after hatching their 
eggs, when they do so for the protection of their young. 
Similarly, Mr. Darwin's MS says of the Upland Geese of 
Australia, which also have well webbed feet, that " they are 
long-legged, run like gallinaceous birds, and seldom or never 
enter the water : Mr. Gould informs me that he believes they 
are perfectly terrestrial, and I am told that at the Zoological 
Gardens these birds and the Sandwich Islands Goose seem 
quite awkward in the water." The MS also points out that 
"the long-legged Flamingo likewise has webbed feet, yet 
lives on marshes, and is said seldom even to wade except in 
very shallow water. The Frigate bird with its extremely 
short legs never alights on the water, but picks up its prey 
from the surface with wondrous skill ; yet its four toes are all 
united by a web ; the web, however, is considerably hollowed 
out between the toes, and so tends to be rudimentary. 

" On the other hand, there does not exist a more thoroughly 
aquatic bird than the Grebe, but its toes are only widely 
bordered by membrane. The water-hen may be constantly 
seen swimming about and diving with perfect ease ; yet its 
long toes are bordered by the merest fringe of membrane. 
Other closely allied birds belonging to the genera Crex, Fassa, 
&c., can swim well, and yet have scarcely any traces of web; 



254 MENTAL EVOLUTION IN ANIMALS. 

moreover their extremely long toes seem admirably adapted 
to walk over the softest swamps and floating plants ; yet the 
common corncrake belongs to one of these very genera, and 
having the same structure of feet, haunts meadows, and is 
scarcely more aquatic than a quail or partridge." 

The MS goes on to detail other and analogous cases, such 
as that of the Ground-woodpecker, Ground-paiTots, and 
Tree-frogs, which have abandoned their arboreal habits ; in 
all which cases the generic structures specially adapted to 
arboreal habits remain. Similarly the swallow-tailed Hawk 
is mentioned as catching flies on the wing like a swallow ; 
a Petrel — " those more aerial of birds " — which has assumed 
the habits of an Auk; the Water-ouzel, a member of the 
Thrush family, which runs along the bottom of streams 
using its wings for diving and its feet for grasping stones 
under the water, " and yet the keenest observer could never 
have foretold this singular manner of life from the most 
careful examination of its structure." 

All the above cases are given by Mr. Darwin, not in re- 
lation to Instinct, but to enforce his argument on adaptive 
structures being developed by natural selection instead of 
designed in special creation. But I have used them in 
relation to the development of Instinct, because, if we aheady 
believe in the natural evolution of organic structures, such 
cases as these afford the best possible evidence of the varia- 
tion of instinct. As evolutionists we could have no stronger 
testimony to the previous though now obsolete instincts of a 
species, than that which is supplied by the presence of pecu- 
liar though useless structures which in allied species are 
correlated with particular instincts. For we must always re- 
member, as previously observed, that instincts are never, like 
structures, fossilized, and therefore that we can never obtain 
direct historical evidence of their transmutation. But the 
best substitute for this evidence is, I think, such testimony 
as I have adduced of persisting structures pointing to obsolete 
instincts. Similar evidence in kind, though not quite so 
strong in degree, is furnished by cases in wliich one species 
of a genus, or one genus in a family, exhibits an instinct 
peculiar to that species or genus — i.e., cases in which the 
instinct does not occur in allied species and genera ; for this 
shows, if we already accept the doctrine of the transmutation 
of species, that the peculiar instinct must have arisen in the 



LOCAL AND SPECIFIC VARIETIES OF INSTINCT. 255 

particular species or genus in question, after that species or 
genus had branched off from the more ancestral type. Now 
such cases of specific instinct are by no means rare — cases, 
I mean, like that of the Californian Woodpecker {Melanerpes 
formicivorus), which displays the curiously distinctive instinct 
of storing acorns in the crevices of the bark of the yellow 
pine {Pinus ponderosa) for future food, while no other species 
of woodpecker shows any tendency to such a habit.* But 
such cases of instinct peculiar to one species or genus are so 
common that I feel it would be needless to enumerate them, 
in view of the more conclusive cases just given — cases more 
conclusive because the obsolete instincts happen to have been 
of a kind requiring special corporeal structures for their 
operation, which now survive their ancestral uses.f Lastly, 
we must not forget the important fact that we are far from 
being wholly without evidence of the transmutation of instinct 
taking place under actual observation — as in the case of the 
ducks in Ceylon having quite lost their natural instincts 
with regard to water (in this resembling the upland geese), 
sparrows and swallows building on houses instead of on trees, 
insects, birds and mammals which normally feed on vegetable 
substances suddenly becoming carnivorous, &c., &c. ; for all 
these cases of local varieties of instinct are really so many 
cases of racial varieties, and the step between this and specific 
varieties is clearly not a large one. 

* According to Mr. C. J. Jackson {Proc. Boston Nat. Hist. Sac, vol. x, 
p. 227) the acorns selected for storing are only tliose which are infested with 
maggots, which serve as food for the young in the following spring ; and the 
acorns are driven into holes specially prepared for them, and which fit so 
well that the maggots when they come to maturity are unable to escape — 
being therefore imprisoned in a larder until they are required for the use of 
the young birds. See also J. K. Lord's Naturalist in Vancouver's Island, 
vol. i, pp. 289-92, and The Ibis, 1868. 

t The most suggestive of this class of cases are those in which the species 
which exhibits the instinct peculiar to itself happens to have become dis- 
persed over wide geographical areas since the instinct arose, and being there- 
fore now found in different parts of the world, living under different 
conditions of life, and yet retaining the same peculiar instinct. Thus, for 
instance, " in all quarters of the globe species of trap-door spiders are found 
occurring in more or less localized areas," and the liarvesting ants of Europe 
and America belong to the same genus. The South American Thrush lines 
its nest with mud in the same way as does our own Thrush, the HornbiUs of 
Africa and of India in their nidification show the same peculiar instinct of 
ijnprisoning their hens in holes of trees with plaster, &c., &c. 



256 MENTAL EVOLUTION IN ANIMALS. 



CHAPTER XVII. 

Instinct (continued). 

Examination of the Theories of other Writers on the 
Evolution of Instinct, with a General Summary of 
the Theory here Set Forth. 

Mill, from ignoring the broad facts of heredity in the 
region of psychology, may be said to deserve no hearing on 
the subject of instinct ; and the same, though in a lesser 
degree, is to be remarked of Bain. Herbert Spencer, and his 
expositor Fiske, express with strong insistence the view that 
natural selection has been of very subordinate importance as 
an evolving source of instinct. Lewes virtually ignores 
natural selection altogether, but nevertheless is not in agree- 
ment with Spencer, inasmuch as Spencer regards instinct as 
*' compound reflex action," and the precursor of intelligence, 
while, as we have already seen, Lewes regards it as " lapsed 
intelligence," and therefore necessarily the successor of in- 
telligence. Thus, while Lewes maintains that all instincts 
must originally have been intelligent, Spencer maintains 
that no instinct need ever have been intelligent.* The 
deliverance of Darwin upon this subject I shall render 
bye-and-by. 

The position of Mr. Spencer is severely logical, and this 
renders easy the definition of the points wherein I here dis- 
agree with him. His argument is that instinctive actions 
grow out of reflex, and in turn pass into intelligent actions, 
so that in his terminology an instinctive action need never 
have been intelligent, and an intelligent action need never 
become instinctive. He is express in saying that although 
" in its higher forms. Instinct is probably accompanied by a 

* I.e., no true instinctive action occurring in all individuals of a species j 
lie recognizes the principle of lapsing iutelligeaco in individuals. 



EXAMINATION OF THE THEORIES OF OTHER WRITERS. 207 

rudimentary consciousness," nevertheless this consciousness 
is not essential to the formation of the instinct ; but, on the 
contrary, is an effect of the growing complexity of the in- 
stinct — "the quick succession of changes in a ganglion, 
implying as it does perpetual experiences of differences and 
likenesses, constitutes the raw material of consciousness; 
the implication is that as fast as instinct is developed, some 
kind of consciousness becomes nascent." 

Now, although we have seen in a previous chapter that 
this view contains much truth — and truth that is of special 
value in relation to the development of Consciousness — it 
appears to me impossible to obtain by it a complete explana- 
tion of the phenomena of instinct. Multitudes of facts of 
the kind which I have given may be rendered to prove that 
many of the higher instincts can only have arisen by way of 
" lapsed intelligence ;" so that if I were called upon to adopt 
either the extreme view of Spencer, which abolishes intelli- 
gence and even consciousness as a factor in the formation of 
instinct, or the extreme antithetical view of Lewes, which 
ignores reflex action with natural selection as other factors in 
the process ; I should feel less difficulty in choosing the latter 
than the former. Not only do many of the higher instincts 
bear internal evidence of having been at some period of their 
history determined by intelligence, and not only do many of 
these higher instincts now show themselves to be plastic 
under an admixture with " a little dose of judgment," but the 
examples of instinct which are chosen by Mr. Spencer are 
not, strictly speaking, examples of instinct at all. They are 
chosen as illustrations because they are the simplest cases of 
what is ordinarily called instinct, and so lie nearest to reflex 
action ; if, however, we pause to examine any of them, we 
find that they are not true instincts, but cases of more or less 
elaborate neuro-muscular adjustment, or, in his own words, 
of " compound reflex action." And the fact that he defines 
or " describes " instinct as compound reflex action does not 
carry any proof that his doctrine is correct. To call a spade 
a club, and then argue that because it is a club it cannot be a 
spade, is futile ; the question consists in the validity of the 
definition. Now it is just because we cannot draw a line 
between simple reflex action and " compound reflex action," 
so as to say that the one is mechanical and the other instinc- 
tive, that I have drawn the line at consciousness, and 



258 MENTAL EVOLUTION IN ANIMALS. 

denominate all actions which occur below this line (liowsoever 
compound) reflex, while reserving the term instinctive for 
habitual actions (howsoever simple) into which there enters 
this element of consciousness. And in doing this I feel 
certain that I am not merely imparting clearness to our 
classification, but also following the dimly intended meaning 
of the term instinct as ordinarily used. No one thinks of 
sneezing, or of the convulsions produced by tickling, as 
examples of instinctive actions ; yet they are " compound 
reflex actions " to a degree of compounding not easily 
paralleled, and certainly much more so than any of the non- 
psychical adjustments which are given by Mr. Spencer as 
illustrations of instinct. 

These illustrations have reference to polyps and creatures 
with rudimentary eyes, wherein the reactions to stimuli 
described appear to me, as I have said, in no way to deserve 
to be called instinctive. For instance, he shows how it is 
possible that without survival of the fittest and without 
intelligent adjustment, " psychical states being habitually 
connected, must, by repetition in countless generations, 
become so coherent that the special visual impression will 
directly call forth the muscular actions by which prey is 
seized. Eventually, the sight of a small object in front will 
cause the various motions requisite for the capture of prey." 
But even in this, the most extreme case supposed, if there is 
not and never has been any consciousness concerned, the 
complex adjustment is in no way distinguishable from a 
reflex action. When I observed jelly-fish crowding into the 
path of a sunbeam shining through a darkened tank, and saw 
that they did so in order to follow the crustaceans on which 
they feed and which always seek the light, I described the case 
as one of reflex action, the development of which had no doubt 
been largely assisted by natural selection ; and I should still 
regard it as a misnomer to call it a case of instinct. For, on 
the one hand, such cases are not nearly so complex in the 
neuro-muscular machinery which they betoken as are many 
or most of the reflex actions exhibited by the higher animals, 
and, on the other hand, if we were to call them instincts, so 
also sliould we require to call every other case of reflex action. 
It is, indeed, impossible, as I said at the commencement of 
these chapters on Instinct, always in particular cases to draw 
the line between instinct and reflex action ; but, as I like- 



EXAMINATION OP THE THEORIES OF OTHER WRITERS. 259 

wise said, "this is altogether a separate matter" and has 
nothing to do with defining what instinct is. And certainly, 
as I there showed, instinct is something more than reflex 
action ; " there is in it the element of mind." 

Moreover, if we were to classify these and all other cases 
of still more compound reflex action under the designation of 
instinct, there would be no category left in which to place all 
cases of true instinct, i.e., cases where consciousness is necessary 
to the performance of an action which but for the occurrence of 
consciousness would be properly classified as a reflex action. 
Of course if we choose we may altogether ignore the distinc- 
tion which the occurrence of consciousness in an action 
imposes, and so classify all reflex actions and all instinctive 
actions under one denomination ; but this is not what 
Mr. Spencer professes to do. He draws a distinction between 
reflex action and instinct ; but he does not draw it at con- 
sciousness ; and the result is that while no real distinction is 
drawn between the two (for compound reflex action is still 
nothing more than a mechanical advance upon simple reflex 
action), the great distinction which actually exists is ignored. 
Let us take an illustration. The giving of suck to young by 
mammals must be regarded as a truly instinctive act. Why ? 
I answer, for one reason, because the animal which performs 
the action is conscious of performing it. If, on the other 
hand, the young animal which is taking the suck is too young 
(as in the case of the Kangaroo) to be reasonably supposed 
conscious of performing its part in the process, I should say 
that the action of the young animal is to be regarded as reflex. 
But Mr. Spencer would classify both these actions under the 
common designation of instinctive. Suppose, then, that this 
is done, and what should we say to this case from among the 
polyps ? McCready describes a species of Medusa which 
carries its larvae on the inner side of its bell-like body. The 
mouth and stomach of the Medusa hang down like the 
tongue of a bell, and contain the nutrient fluids. McCready 
observed this depending organ to be moved first to one side 
and then to the other side of the bell, in order to give suck 
to the larvae on the sides of the bell — the larvae dipping their 
long noses into the nutrient fluids which that organ of the 
parent's body contained. Now if this case occurred in any 
of the higher animals, where we might suppose intelligent 
consciousness of its occurrence to be present it would pro- 



260 MENTAL EVOLUTION IN ANIMALS. 

perly be regarded as a case of instinct. But as it occurs in 
an animal so low in the scale as a jelly-fish, we are not 
warranted in assuming the presence of an intelligent percep- 
tion of the process, and therefore in my view we must classify 
the case, not as one of instinct, but as one of reflex action, 
which, like all other cases of complex reflex action, has 
probably been developed by natural selection. But it would 
follow from Mr. Spencer's view that the case must be classified 
as one of instinct, and therefore as presenting no point of 
psychological distinction from that of giving suck in the case 
of a mammal. Surely it is a more pliilosophical mode of 
constructing a psychological classification, to acknowledge the 
great distinction which the presence of a psychical element 
makes between two such cases as these ; and, if so, the dis- 
tinction stated in its simplest terms is the one which I have 
already stated — viz., that while the stimulus to a reflex action 
is at most a sensation, the stimulus to an instinctive action 
can only be a perception. 

In my opinion, then, Mr. Spencer's theory of the forma- 
tion of instincts is seriously at fault in that it fails to distin- 
guish the most essential feature of instinct ; moreover it does 
not recognize the important principle of the lapsing of intelli- 
gence, and thus fails to account for the very existence of that 
whole class of instincts which I have called secondary. Next 
I have to show that this theory is further defective in that it 
fails to recognize sufficiently the other and no less important 
principle of natural selection, and so in large measure fails 
to account for the existence of that whole class of instincts 
which I have called primary. Thus, he says expressly with 
reference to instinct, " while holding survival of the fittest to 
be always a co-operating cause, I believe that in cases like 
these it is not the chief cause."* Now it so happens that the 
" cases " of which he is speaking are those of the artificial 
instincts of pointers, retrievers, and other domestic animals ; 
hence by " survival of the fittest," we must understand 
artificial selection (which is here the analogue of natural 
selection among wild animals), and therefore the remark 
happens to be particularly unfortunate in the connection in 
which it occurs, seeing it is perfectly certain that but for the 
most careful and continued selection by man, our pointers 
and retrievers would never have come into existence. But 

• Principles of Fsi/cJioIoai/, i, p. i23. 



EXAMINATIOX OF THE THEORIES OF OTHER WRITERS. 261 

even as regards the instincts of wild animals the judgment in 
question appears to me no less objectionable. How, for 
instance, are we to account by any process of " direct equili- 
bration " for the incubating instinct, cell-making instinct, the 
instinct of cocoon-spinning, not to mention all the other 
primary instincts which I have considered, nor again to repeat 
all the proof of the variability and heredity of acquired 
habits ? 

Still, having thus shown as clearly as I can that in my 
opinion Mr, Spencer certainly attributes much too little to 
the iniluence of natural selection in the formation of instincts, 
and also that I think he has committed a still graver over- 
sight by altogether ignoring the influence of lapsing intelli- 
gence, I shall next show that his argument is of use in dis- 
covering another consideration which, for the sake of avoiding 
confusion, I have hitherto suppressed. His argument briefly 
stated is that instincts may arise independently both of 
natural selection and of lapsing intelligence, by " direct 
equilibration " alone ; he supposes them to arise immediately 
out of reflex action. Now, although we have seen that if 
such is the case they ought not to be called instincts, unless 
they present a mental constituent, still they must be called 
instincts if, as he further supposes, the growing complexity of 
the reflex process culminates in evolving such an element. 
We have already seen, while treating of the dawn of con- 
sciousness, that this most probably is the way in which the 
mind-element arose, and, if so, Mr. Spencer's argument does 
present a possible third mode in which many of the simpler 
instincts — or instincts of the lowest animals — may have 
taken origin. This third mode, it will be observed, is the 
converse or opposite of that which we have called the 
lapsing of intelligence ; it is a mode which leads up to or 
culminates in consciousness (when for the first time the action 
ceases to be reflex and becomes instinctive), instead of de- 
scending or becoming degraded into unconsciousness. Now, 
that such a process may take place, is, I think, on a priori 
grounds very probable, although from the nature of the case 
it is not possible to find proof of its occurrence ; for if it does 
occur, it can only do so among the lowest animals, where we 
are not able to obtain evidence of consciousness even if in- 
cipiently present. Therefore, as the process can only refer to 
the genesis of actions which occupy the doubtful border-land 
12 



262 MENTAL EVOLUTION IN ANIMALS. 

between the reflex and the instinctive, this possible thiird 
mode in which rudimentary instincts may arise need not claim 
consideration with reference to the origin of instincts in 
general, although the subject is, as we have seen, of much 
importance in relation to the origin of consciousness. 

It only remains to point out that if instincts ever do 
arise by way of this third mode, the implication would appear 
to be, as Mr. Spencer admits, that " survival of tlie iittest 
must always be a co-operating cause." I should, however, 
even here be inclined to go further, and to say that survival 
of the fittest must in this co-operation be of more than the 
subordinate importance which Mr. Spencer attributes to it. 
For instance, taking again the case of the Medusae seeking 
the light, and supposing the action to have become dimly 
conscious and so incipiently instinctive ; when the tendency 
to seek the light first began to manifest itself, and the indi- 
viduals which sought the light were thereby enabled to pro- 
cure more food than those which did not, natural selection 
would at once begin to develop the reflex association between 
luminous stimulation and movement towards light. Here, in 
fact, the intervention of any other cause of a directly equili- 
brating kind seems out of the question, inasmuch as, apart 
from high intelligence, which ex hypothesi is ab&ent, there 
could be no bond of union between the stimulus supplied by 
light and the obtaining of food in the light. Only by natural 
selection could such a bond have here been established ; and 
the same considerations apply to many or most of the quasi- 
instinctive actions exhibited by low animals. 

So much then for the view which would regard all in- 
stincts as outgrowths of reflex action. But scarcely less 
objectionable is the other extreme view which would regard 
all instincts as outgrowths of intelligence. This, as I have 
said, is the view expressed by Lewes, and also, I may add, by 
the Duke of Argyll, who seems never to have read Mr. 
Darwin's doctrine of the development of instincts by natural 
selection.* But be individual o])inion what it may, surely it 
is sufficiently evident, as pointed out at the commencement 
of our discussion, that to assign all instincts to an intelligent 

* See Contemporary Review, November, 1880, wliere the Duke argues 
tliat the origin of many instincts is hopelessly obscure, because they cannot be 
explained by the unaided principle of lapsing]; intelligence — without once 
alluding to the immense field of possibilities which is opened up by the intro- 
duction of the principle of natural selection. 



EXAMINATION OF THE THEOEIES OF OTHER WRITERS. 263 

origin is a hopeless attempt at making a valid explanation of 
one thing a satisfactory explanation of another, 

Eecognizing, then, in the light of all the foregoing facts, 
both the principles which are concerned in the development 
of instincts, I shall now pass on to state the opinion of Mr. 
Darwin. 

In the " Origin of Species " he writes (pp. 206-7), " It 
■{ve suppose any habitual action to become inherited — and it 
can be shown that this does sometimes happen — then the 
resemblance between what originally was a habit and an 
instinct becomes so close as not to be distinguished. If 
Mozart, instead of playing the pianoforte at three years old 
with wonderfully little practice, had played a tune with no 
practice at all, he might truly be said to have done so instinc- 
tively.* But it would be a serious error to suppose that the 
greater number of instincts have been acquired by habit in 
one generation, and then transmitted by inheritance to suc- 
ceeding generations. It can be clearly shown that the most 
wonderful instincts with which we are acquainted, namely, 
those of the hive-bee and of many ants, could not possibly 
have been acquired by habit. 

" It will be universally admitted that instincts are as 
important as corporeal structures for the welfare of each 
species, under its present conditions of life. Under changed 
conditions of life, it is at least possible that slight modifica- 
tions of instinct might be profitable to a species ; and if it 
can be shown that instincts do vary ever so little, then I can 
see no difficulty in natural selection preserving and continu- 
ally accumulating variations of instinct to any extent that 
was profitable. It is thus, I believe, that all the more com- 
plex and wonderful instincts have originated. As modifica- 
tions of corporeal structures arise from, and are increased by, 
use or habit, and are diminished or lost by disuse, so I do 
not doubt it has been with instincts. But I believe that the 
effects of habit are in many cases of subordinate importance 
to the effects of natural selection of what may be called 
spontaneous variations of instincts ; — that is of variations 

* From this it will be observed that by tlie phrases " inherited habit," 
" habitual actions becoming inherited," &c., Mr. Darwin means to allude to 
the principle of lapsing intelligence. This must be borne in mind while 
reading these quotations, where " habit " is always used in the sense of intelli- 
gent adjustment which has become partly automatic iu the individual. 



264 MENTAL EVOLUTION IN ANIMALS. 

produced by the same unknown causes which produce slight 
deviation of bodily structure." 

Again, in the " Descent of Man," he repeats substantially 
the same judgment (pp. 67-8) ; and among his MSS I find 
the following passage, which I shall quote because it serves to 
convey his opinion in a still more clear and emphatic manner. 

" Although, as I have attempted to show, there is a strik- 
ing and close parallelism between habits and instincts ; and 
although habitual actions and states of mind do become here- 
ditary, and may then, as far as I can see, most properly be 
called instinctive ; yet it would be, I believe, the greatest 
error to look at the great majority of instincts as acquired 
through habit and become hereditary. I believe that most 
instincts are the accumulated result, through natural selec- 
tion, of slight and profitable modifications of other instincts ; 
which modifications I look at as due to the same causes 
which produce variations in corporeal structure. Indeed, I 
suppose that it will hardly be doubted, when an instinctive 
action is transmitted by inheritance in some slightly modified 
form, that this must be caused by some slight change in the 
organization of the brain. (Sir B. Brodie, 'Psychological 
Enquiries,' 1854, p. 199.) But in the case of the many 
instincts which, as I believe, have not at all originated in 
hereditary habit, I do not doubt that they have been 
strengthened and perfected by habit ; just in the same 
manner as we may select corporeal structures conducing to 
fleetness of pace, but likewise improve this quality by train- 
ing in each generation." 

From these quotations it is evident that Mr. Darwin 
clearly recognized both the lapsing of intelligence and natural 
selection as operating causes in the formation of instinct; 
but that he regarded natural selection as the more important 
of the two. Although, however, he does not expressly say 
so, I cannot doubt — in fact I know — that he fully recognized 
the importance of intelligence in supplying adaptive as dis- 
tinguished from fortuitous variations to be seized upon by 
natural selection. Viewed in this relation, natural selection 
may be deemed a promoting cause of the lapsing of intelli- 
gence into instinct, and the two principles working in con- 
j unction must, I think, be more potent than either working 
alone. But if I were asked which of the two I deem more 
important, I should say that natural selection must be held to 




n t: r L ex 



A r T I n . 



I f,' T EL L I a C f,<T ACTION 



EXAMINATION OF THE THEORIES OF OTHER WRITERS. 265 

have the pre-eminence, inasmuch as the principle of lapsing 
intelligence can demonstrably have had no part at all in the 
formation of the " most complex and wonderful instincts " 
with which we are acquainted — viz., those of the social 
Hymenoptera.* And this, as we have seen, is the judgment 
of Mr. Darwin, which therefore appears to me, in considera- 
tion of all the reasons which I have now stated, to be the 
truest judgment — and this without reference to the unap- 
proachable authority upon the subject with which he must be 
held to speak. 

General Summary on Instinct. 

For the sake of rendering clear the relations which the 
sundry principles that are concerned in the formation of 
instinct bear to one another, I append a diagram which is 
designed to show these relations in a graphic form. After 
what has now been said it is only needful, for the purpose of 
explaining the diagram, to observe the following points. The 
little twigs which are represented as growing out of the large 
branches or principles, are intended to represent instincts, 
and I have inserted theui in order to mark the only principles 
from which instincts (in accordance with my definition of 
instincts) are able to spring. Here and there I. have repre- 
sented the branching structure of these instincts as inarching 
with one another — a device which is intended to display 
what I take to be an important additional principle, viz., 
that fully-formed instincts may occasionally blend, so giving 
rise to new instincts ; this may be due either to novel 
circumstances leading to an intentionally adaptive blending 

* It is demonstrable that lapsing intelligence can have played no part in 
the formation of these instincts, because the " workers," both among bees and 
ants, are sterile. Lewes can never have had this particular case presented to 
his mind, for it proves bis theory of lapsing intelligence alone insufficient. 
It is likewise incompatible with Spencer's theory. Thus, for instance, he 
■writes : — " The automatic actions of a bee building one of its wax cells, 
answer to outer relations so constantly experienced that they are, as it were, 
organically remembered " (Principles of Psychology, i, p. 445). But he forgets, 
as Lewes also forgot, that the insect which perforins these automatic actions 
has not thus " constantly experienced " the " outer relations," for it begins by 
performing these actions before it has itself had any individual experience of 
cell-making, and without its parents ever having had any ancestral experience. 
In the whole range of instincts no more unfortunate illustration coidd have 
been chosen by Mr. Spencer. How the difficulty is met by Mr. Darwin's 
theory I shall consider at the beginning of the next chapter. 



266 MENTAL EVOLUTION IN ANIMALS. 

of instinctive habits, or to an originally conscious imitation 
by one species of the instinctive habits of another. Lastly, 
I have joined the two tree-like growths at their summits in 
order to represent the fact that intelHgent and non-intelligent 
adaptation, or primary and secondary instincts, may fuse 
together and then possess a common sap or principle of 
further growth. I have also represented such union between 
the two sides of the diagram, primary and secondary, to take 
place at one other point — viz., between the branch Primary 
Instinct and the branch IntelHgent Variation of Secondary 
Instinct. I do this to bring out into stronger prominence the 
fact that when once a non-intelligent or primary instinct has 
been formed, it is most ready to join with and become fertilised 
by the principle of intelligence at any point where this 
principle is, as it were, mobile, or not yet fixed and frozen 
into secondary instinct. But the most important thing to 
remember is that whether instincts have had an intelligent or 
a non-intelligent mode of origin, they may at any time after 
their full formation come into contact with intelligence at any 
point; so that the two sides of our diagram (being the 
embodiment of all the foregoing evidence upon the subject) 
illustrate at once the truth and the falsity of the common 
opinion which has been so neatly rendered by Pope, when 
he says of instinct and reason that they are things " for ever 
separate, yet for ever near," 

I shall now proceed to give a general summary of all the 
preceding chapters on Instinct. 

After defining the sense in which alone I use the word 
Instinct, I proceeded to give a few illustrations of the perfec- 
tion of instinct as exhibited by very young animals, or by 
animals without individual experience of the circumstances 
to which their instinctive actions are adapted. Next I gave 
a few complementary illustrations of the imperfection of in- 
stinct, and pointed out that such imperfection might arise, 
either from a change in the conditions of the environment to 
which the ancestral instinct was adapted, or from the fact that 
the instinct is not yet completely formed. I also showed that 
imperfection of instinct might arise from internal or psycho- 
logical changes throwing out of gear the delicate mechanism 
on which the perfect disx)lay of instinct depends. In this 
connection I gave instances to prove that such derangement 



EXAMINATION OF THE TIIEOEIES OF OTHER WKITERS. 267 

of instinct is particularly apt to arise when the normal 
history of an animal's converse with its environment is 
interrupted for a time and again renewed. I also gave one 
case of such derangement where there had been no such 
interruption, and which, therefore, may most properly be 
regarded as a case of insanity. 

If instincts are slowly evolved, we should expect to meet 
with some cases in which they are not yet fully evolved, and, 
as just observed, for this reason imperfect. Such cases we 
do find — as, for example, young turkeys pointing at flies, 
young chickens being half afraid of bees, rabbits only toddling 
instead of running away from weasels, &c., &c. We may 
also see instincts in course of development among young 
children learning to balance the head, to w^alk, to speak, &c. 
Moreover all cases of the education or improvement of in- 
stinct, whether in the individual or in the race, are so many 
cases of the original imperfection of instinct. But this 
brought us directly into the question as to the origin of 
instincts. 

I have endeavoured to prove that the origin of instincts 
may be what I have called either primary or secondary. 
That is to say, I believe there is ample evidence to show that 
instincts may arise either by natural selection fixing on pur- 
poseless habits which chance to be profitable, so converting 
these habits into instincts without intelligence beinsr ever 
concerned in the process ; or by habits, originally intelligent, 
becoming by repetition automatic. As an example of a 
primary instinct I gave incubation; and as examples of 
secondary instincts I gave sundry cases of " practice making 
perfect." On a priori grounds we saw that instincts must 
arise by the processes thus explained, and then we proceeded 
to render a 'posteriori proof that they have. This proof under- 
took to show that purposeless habits occur in individuals, are 
inherited, vary, have their variations inherited, and then 
developed in beneficial lines by natural selection ; also that 
habits originally intelligent by repetition become automatic, 
and, having lapsed from intelligence, are then inherited as 
instincts, which may then vary, have their variations inherited 
and developed in beneficial lines by natural selection, as in 
the previous and analogous case. These sundry proposi- 
tions were substantiated by showing, first, that tricks of 
manner are displayed more or less by every one, and especially 



268 MENTAL EVOLUTION IN ANIMALS 

by idiots; also by animals, as in dogs barking round a 
carriage, differences of individual disposition and idiosyn- 
cracies, forming strange companionships, &c. Next, that 
automatic and useless or fortuitous habits are inherited, was 
amply proved by cases in which this has been observed of the 
tricks of manner displayed by men and animals ; in disposi- 
tion, as among the island races of monkeys described by 
Humboldt ; in the paces of the horse in different parts of the 
world ; in the remarkable and wholly useless habits of the 
tumbler and pouter pigeons, &c. Further, that such inherited, 
non-intelligent, or purposeless habits should vary, is a matter 
of certainty ; seeing that, as was subsequently shown, useful 
habits may do so, and that even fully formed instincts are 
plastic ; much more, then, must these fortuitous sports of 
habit be variable. Lastly, that when they vary in profitable 
directions the variations will be seized upon and fixed by 
natural selection is no less a matter of certainty, and will not 
be questioned by any one who believes in natural selection 
as a principle concerned in the evolution of organic structures. 
Thus only can we explain the instincts of many low animals 
(such as the caddis-worm), and certain instincts of the higher 
(such as that of incubation). Coming next to secondary 
instincts, it was first shown that intelligent adjustments when 
frequently performed become automatic in the individual, 
and next that they are inherited till they become automatic 
habits in the race. The former fact is familiar to every one ; 
the latter was proved by such cases as those of hereditary 
handwriting, family aptitudes for particular pursuits, race 
characteristics of psychology in man, good breeding, and 
sense of modesty. In animals the same principle is seen in 
an hereditary tendency to " beg " in dogs, and even in cats ; 
ponies from Norway not having " mouths ;" Dr. Huggins's 
dog presenting an inherited antipathy to butchers ; wild 
animals showing an instinctive fear of their particular 
enemies, such fear being lost as regards man in domesticated 
animals (notably in the rabbit and duck, where selection is 
not likely to have had any part in obliterating natural wild- 
ness) ; animals living on oceanic islands showing no fear of 
man for several generations after his first advent among 
them, then acquiring instinctive dread of him, and even 
learning what constitutes safe distance from lire-arms ; 



EXAMINATION OF THE THEOEIES OF OTHER WRITERS. 269 

changed instincts of the woodcock ; and the effects of blend- 
ing instincts by crossing. 

It having been fully shown by these selected examples 
that instincts may arise by natural selection alone, or by 
lapsing intelligence alone, the discussion went on to show 
that instincts in general are not necessarily confined to one 
or other of these two modes of origin ; but, on the contrary, 
that these principles when working in cooperation have 
greater influence in evolving instincts than either of them 
can have when working singly. For, on the one hand, 
hereditary proclivities or habitual actions which, being useful 
though never intelligent, were originally fixed by natural 
selection, may come to furnish material for further improve- 
ment, or be put to better uses, by intelligence ; and, con- 
versely, adjustments originally due to lapsed intelligence may 
come to be greatly improved, or put to better uses, by natural 
selection. For, taking the latter case alone, if, as we have 
seen, intelligent actions may by repetition become automatic 
as secondary instincts, and if they may then vary and have 
their variations fixed in beneficial lines by natural selection, 
how much more scope may be given to natural selection in 
this further development of an instinct, if the variations of 
this instinct are not wholly fortuitous, but arise as intelligent 
adaptations of ancestral experience to the perceived require- 
ments of individual experience. Clearly, natural selection 
must in such a case be working at a much greater advantage 
than it does when working alone in the formation of primary 
instincts, where it is supplied only with fortuitous variations, 
instead of with variations which, being determined by intelli- 
gence, are from the first adaptive. And no less clearly, the 
principle of lapsing intelligence must be working at a nmch 
greater advantage when thus in association with natural selec- 
tion, than it is when working alone in the formation of 
secondary instincts ; for natural selection in this case must 
always tend to favour the best of the intelhgent adjustments, 
and by concentrating the power of heredity into them must 
tend the more speedily to render them automatic or in- 
stinctive. 

It is of no moment, as regards instincts of blended origin, 
to determine in particular cases which of the two principles 
— natural selection or lapsing intelligence — has had the 



270 MENTAL EVOLUTION IN ANIMALS. 

historic priority, even if from the first these two principles 
have not been in combination ; the important fact to be 
shown is that even a fully formed instinct may prove itself, 
^^nde^ the influence of intelligence, variable or plastic. I 
therefore demonstrated the plasticity of many existing 
instincts, dwelling especially upon the cell-making instinct 
of bees, and the incubating and maternal instinct of warm- 
blooded animals — choosing these instincts for special con- 
sideration because they must be of so ancient an origin, and 
are so strongly inherited. 

Intelligence may operate in the modification of instinct, 
either by perceiving the need of a change in the dictates of 
heredity, by intelligent imitation of the habits of other 
animals, or by parents intentionally teaching their young. 
Copious facts on all these points were therefore given. But 
the best evidence of the extreme modification which instincts 
may be made to undergo by the combined effects of intelli- 
gence and selection, is that which is afforded by the facts of 
Domestication. These facts were therefore detailed at length, 
and they showed that domestication has not merely a nega- 
tive influence in eradicating natural instincts (witness the 
loss of wildness in dogs, cats, horses, and cattle ; dogs not 
attacking sheep, pigs, or poultry ; the latter having lost their 
instinctive fear of dogs, so differing from pheasants ; the 
incubating instinct being lost in the Spanish hen, and the 
maternal instinct in cows and sheep where the young have 
for generations been habitually removed from their mothers 
at birth ; Polynesian dogs having lost their natural intelli- 
gence, together with their natural taste for flesh) ; but also a 
positive influence in developing new instincts. In the case 
of the Dog these new or " artificial " instincts were shown to 
be strikingly exhibited in the sheep-dog, pointer, and re- 
triever ; but perhaps still more remarkably in the instinctive 
love of man shown by nearly all the breeds ; faithfulness to 
and sense of dependence upon man ; inborn idea of protect- 
ing his master's property and of himself as constituting a 
part of that property ; barking being an acquired instinct, 
and probably arising from this idea of protecting his master's 
property. Indeed so fundamental has been this psychological 
transformation in the dog, that the artificial instincts have 
frequently become stronger than even the strongest of the 
natural instincts, viz., the maternal — as is proved by cases in 



EXAMINATION OF THE THEORIES OF OTHER WRITERS. 271 

which the latter has given way when in conflict with the 
former. Lastly, I devoted a chapter to the consideration of 
local and specific variations of instinct, showing how these 
constituted a kind of palseontological evidence of the trans- 
mutation of instinct. 

Such then is the a posteriori proof of the two ways which, 
either singly or in combination, must be regarded as those by 
which all properly so-called instincts have been developed. 
A diagram was given to show graphically how the sundry 
principles concerned are related and inter-related with one 
another. Here it was shown that when an instinct, whether 
of single or blended origin, was perfected, it might vary or 
ramify into modified forms, and even blend, or, as it were, 
inarch with other instincts to produce a new growth. It is 
difficult, or rather impossible, to trace the history of actual 
instincts in this respect, from the fact that instincts are not 
fossilized, and therefore leave no record of their transi- 
tional states. But from all the evidence together — and 
especially from what we may almost denominate the historical 
evidence supplied by the facts of domestication — there can be 
no reasonable doubt that instincts may not only have a double 
root — one in the principle of selection, and the other in that 
of lapsing intelligence — but also a more or less branching 
stem, which (or the branches of which) may in' some cases 
become grafted with the stem or branches of other instincts. 

In estimating the comparative importance of the two 
great factors in the formation of instinct, we had occasion to 
differ on the one hand from Mr. Spencer, who attributes the 
origin of all instincts to reflex action with little or no aid 
from natural selection, and on the other hand with Mr. Lewes, 
who goes to the opposite extreme of regarding all instincts 
as cases of lapsed intelligence. It was shown, however, that 
Mr. Spencer's view might be held to explain the rise of 
doubtfully instinctive actions displayed by very low animals, 
and that it is of much importance as an explanation of the 
origin of Consciousness. The view, however, which I adopt 
to explain the origin of instincts is substantially the same as 
that which has been propounded by Mr. Darv^'in, and which, 
while recognizing both the factors which I have now so 
repeatedly named — i.e., natural selection and lapsing intelli- 
gence — whether singly or in combination, attributes most 
importance to the former, especially if it be remembered that 



272 MENTAL EVOLUTION IN ANIMALS. 

in its work of organizing instincts, intelligent adjustment is 
always under the direction and control of natural selection, 
so that its chief function in the formative process is probably 
that of supplying to natural selection variations of ancestral 
instincts which are not merely fortuitous, but intentionally 
adapted to the conditions of the environment. 



SlanLAR INSTINCTS IN UNALLIED ANIMALS. 27^ 



CHAPTER XVIII. 

Instinct (continued). 

Cases of Special Difficulty with Eegard to the Fore- 
going Theory of the Origin and Development of 
Instincts. 

We must not take leave of Instinct without looking into all 
the known cases of its exhibition which admit of being 
reasonably cited against the views here expressed on the rise 
and development of instincts generally. I shall therefore 
consider seriatim all such cases which I have met with in the 
writings of others, or which occur to me as admitting of being 
possibly cited in this connection. 

Similar Instincts in Unallied Animals. 

Mr. Darwin observes in the Appendix, " We occasional! 
meet with the same peculiar instinct in animals widely 
remote in the scale of nature, and which consequently cannot 
have derived the peculiarity from community of descent.'' 
The difficulty, of course, is to account for the parallelism, and 
the instances given by Mr. Darwin are those of the Molothrus 
having the same instinct of parasitism as the Cuckoo, the 
Termites having much the same instincts as the Ants, and a 
neuropterous and a dipterous larva having the same instinct 
of digging a pitfall for prey. He shows satisfactorily that 
the last-mentioned is the only case that offers any real diffi- 
culty ; but even here, it seems to me, the difficulty is not one 
of any magnitude. For the instinct in question is not one 
of such complexity, or of such remote probability as to its 
formation where a larva habitually lives in sand, that we 
may not readily believe a similarity of environment should 
have determined its development independently in two Hnes 



274 MENTAL EVOLUTION IN ANIMALS. 

of descent — just as for the same reason wings, for example, 
have been developed independently in at least four lines of 
descent. 

Dissimilar Instincts in Allied Animals. 

Mr. Darwin in the Appendix also alludes to this snlTJect, 
and the few remarks which he makes upon it seem to me 
fully to dispose of the difficulty — which, indeed, with his 
characteristic candour, I cannot but think that he unduly 
magnifies. As I have observed in my chapter on Local and 
Specific Variations of Instinct, the theory of the formation of 
instincts by natural selection really leads us to anticipate 
the not infrequent occurrence of what we may term isolated 
instincts ; for only if we were to suppose that all considerable 
variations of instinct (local or otherwise) are permanent, 
could we anticipate — in the absence of any palaeontology of 
instinct — a graduated series of instincts in all cases, with the 
consequent absence of isolated instincts in every case. But 
to suppose this would be to run counter to the first principles 
of our theory. Of course if specific instincts were of very 
general occurrence, it might reasonably be objected that this 
theory would require to suppose too great a slaughter of 
intermediate species to be accepted as credible ; but as 
matters actually stand I have felt that the occasional appear- 
ance of isolated instincts in about the proportion of cases 
that the theory would lead us to anticipate, really constitutes 
a corroboration of, rather than an objection to, the theory. 

Trivial and Useless Instincts. 

Mr. Darwin in the Appendix also refers to trivial and 
useless instincts, and says: — "I have not rarely felt that 
small and trifling instincts were a greater difficulty on our 
theory, than those which have so justly excited the wonder 
of mankind ; for an instinct, if really of no considerable 
importance in the struggle for life, could not be modified 
or formed through natural selection." 

This is no doubt an important point, and must be care- 
fully considered. First of all it ought to be observed that if 
any such difficulty can be sliown to stand against the theory 
of the formation of instinct by natural causes, much more 
must the difficulty stand against the older theory of the 



TEIVIAL AND USELESS INSTINCTS. 275 

implanting of instincts by a supernatural cause. Next, we 
must be perfectly sure, in any given case, that the instinct 
which appears to be trivial or useless is really such. This 
point is mentioned by Mr. Darwin, and he cites some very 
good cases to show how the important utility, or even abso- 
lute necessity, of an instinct may readily escape observation. 
But even after due allowance is made on this score, some few 
instincts certainly do remain which it seems impossible to 
suppose of the smallest utility. How, then, are these to be 
explained ? 

I believe they admit of being satisfactorily explained by 
two considerations. The first of these is that our theory 
does not suppose natural selection to be the only influence at 
work in the formation of instincts. We have repeatedly 
insisted that the lapsing of intelligence is another influence 
of scarcely less importance ; and we have also seen abundant 
evidence to show that non-adaptive habits occur in indi- 
viduals and may be inherited in the race. Therefore, if from 
play, affection, curiosity, or even mere caprice, the intelligence 
of the animal should lead the animal to perform any useless 
kind of action habitually (as, for instance, in the case of the 
ratels tumbling head-over-heels),* and if this habit were to 
become hereditary in the similarly constituted progeny, we 
should have a trivial or useless instinct. The only condition, 
so far as I can see, that would require to be satisfied would 
be that the trivial or useless habit should not be actuall}'' 
detrimental to the species exhibiting it, so that its growth 
into an instinct should not be prevented by natural selec- 
tion. 

The other consideration to which I have alluded as 
mitigating or dispelling the difficulty in question is this. In 
the analogous case of structures, as is well known, we meet 
with innumerable cases of useless organs ; but here, so far 
from the fact being deemed a difficulty in the way of the 
theory of evolution by natural selection, it is justly deemed 
one of its strongest supports; and the reason is that in 
all such cases we have evidence of the useless and perhaps 
rudimentary organs being of use in other and allied animals. 
Now I see no reason to doubt that the same may be true of 
instincts, and therefore that what we now find to be ap- 
parently trivial and certainly useless exhibitions of hereditary 

* See p. 189. 



276 MENTAL EVOLUTION IN ANIMALS. 

habit may, at an earlier period in the history of the species 
or of its allies, have been of real utility. We may, for 
example, readily imagine that the instinct displayed by many 
herbivorous animals of goring sick or wounded companions, 
is really of use in countries where the presence of weak 
members in a herd is a source of danger to the herd from the 
prevalence of wild beasts ; and Mr. Darwin in the Appendix 
gives evidence that such is actually the case. Or, to take a 
more fanciful illustration, we may suppose the Megapodidse 
mentioned in the Appendix, which incubate their eggs by 
placing them in a large heap of fermenting vegetable matter 
which they collect for this purpose, were to find, from a 
change of their habitat or of the Australian climate, that it 
was difficult to collect a sufficient quantity of vegetable 
matter, or that it would not ferment sufficiently for the pur- 
pose of incubation. The birds might then gradually revert 
to the usual mode of incubation, but might still retain a 
marked propensity to make tvimuli of vegetable matter as 
nests. If so, the labour expended in making such tumuli 
would be obviously useless, and there being no analogy 
among the incubating habits of other birds to give us a clue 
as to the origin of such an instinct, we should be quite at a 
loss to account for it. 



Instincts apparently Detrimental to the Species which 
exhibit them. 

It constitutes no difficulty or objection to our general 
theory of instinct-formation to point to cases in which in- 
stincts are obviously detrimental to the individuals which 
manifest them ; for it is of the essence of the theory of 
natural selection to suppose that the interests of the indi- 
vidual are, in the process of selection, subordinated to those 
of the species. It is, for example, manifestly to the detri- 
ment of an individual fly to procreate its kind, inasmuch as its 
own death is speedily induced by the act ; but seeing that the 
act is essential to the continuance of the species, we perceive 
how natural selection must here have developed an instinct 
which virtually amounts to that of suicide. And the same 
remark applies to all similar cases, such as that alluded to in 
"Animal Intelligence" of soldier ants and termites sacrificing 
themselves for the benefit of the community — i.e., the species. 



INSTINCTS APPARENTLY DETRIMENTAL TO THE SPECIES. 277 

But of course the case is entirely altered where we appear to 
meet with an instinct the operation of which is detrimental 
to the individual, without being attended with any com- 
pensating benefit to the species ; for in such a case the 
detriment to the individual would also become a detriment 
to the species. Such apparent cases, in fact, are precisely 
analogous to those in which certain structures appear to be 
detrimental to their possessors, without seeming to confer 
any compensating benefit upon their species;* and, as Mr. 
Darwin observes, such an apparent case, if it could be shown 
to be a real one, would be incompatible with the theory of 
natural selection, inasmuch as '' natural selection acts solely 
by and for the good of each." Further, as Mr. Darwin 
adds, " if it could be proved that any part of the structure of 
any one species had been formed for the exclusive good of 
another, it would annihilate my theory ; " and it is obvious 
that the same remark would equally apply to the case of 
instincts. 

It is therefore of the utmost importance to take a survey 
of all kno^vn instincts, in order to see whether there is any 
one case, either of an instinct which is detrimental to the 
species exhibiting it, or of one wdiich has exclusive reference 
to the benefit of other species. For, on the one hand, if 
there is any one such case of an indisputable kind, we should 
clearly have to modify our whole theory in order to meet it ; 
while, on the other hand, if there is no such case, the fact of 
all the innumerable multitude of animal instincts being of 
obvious use to the species which manifest them, and never 
of exclusive use to other species, must be taken as the 
strongest possible evidence of the theory that ascribes all 
instincts to the causes which we have assigned. 

I may as well say at once that there is only one apparent 
case of an instinct in one species having exclusive reference 
to the benefit of another, although there are cases of instincts 
beneficial to the species presenting them being also beneficial 
to other species. With the latter cases we are not, of course, 
concerned. The former is the case of aphides yielding up 
their secretion to ants, and has already been considered by 
Mr. Darwin. His explanation is that, " as the excretion is 
extremely viscid, it is no doubt a convenience to the aphides 

* See Origin of Species, 162-4, where the case of the rattle of the rattle- 
enake, &c., is considered. 



278 MENTAL EVOLUTION IN ANIMALS. 

to have it removed ; therefore probably they do not excrete 
solely for the good of the ants."* 

Coming now to the other branch of the subject, after due 
reflection I can only think of two or three instincts which 
could possibly be cited as presenting the appearance of being 
detrimental to the species which manifest them. I shall 
therefore consider these cases separately. 

1. Suicide of Scorpion. — The state of the evidence on this 
subject will be found in my other work.f It will there be 
seen that two or three independent witnesses — including a 
friend of Dr. Allen Thomson on whose accuracy he says he 
can rely — bear testimony to the truth of the popular saying 
that when a scorpion is surrounded by fire, or otherwise 
exposed to undue heat, it will commit suicide by stinging 
itself to death. It will be seen, however, by referring to the 
correspondence in question, that the alleged facts are disputed 
by other observers, and also, as I have already indicated, that 
they were not observed by Dr. Thomson himself. 

The effect of republishing this correspondence and of 
pointing out the desirability of obtaining further evidence 
upon the matter, has been to induce two very competent 
naturalists to make some observations upon the subject. One 
of these naturalists is Professor Lankester, vdio published his 
observations in the "Journal of the Linnean Society " (1882), 
and the other is Professor Lloyd Morgan, who published his 
results in " Nature " (vol. xxvii, p. 313). Both these observers 
agree that the scorpions never commit suicide, and as Mr. 
Morgan exposed the animals to a variety of dreadful toitures 
with a uniformly negative result, I think the question may 
now be considered as closed. Moreover Mr. G. Bidie, who 
started the previous correspondence in "ISTature," has recently 
addressed another letter to that Journal^ in which he makes 
the not improbable suggestion that, as in his experiments he 
applied heat by condensing the rays of the sun with a lens 
upon a small point of the scorpion's back, the animal in 
stinging itself " may have merely been trying to get rid of an 
imaginary enemy." 

2. Insects jlyinrj through Flame. — The determination shown 
by many kinds of insects to fly towards and through a flame 
is unquestionably due to instinct, and as such might be ad- 

* Onjiii of Species, p. 208. + Animal Intelligence, pp. 222-5. 

I July 12; ]8S;i. 



INSTINCTS APPARENTLY DETRIMENTAL TO THE SPECIES. 279 

duced as evidence of an instinct detrimental alike to the 
individual and to tlie species. But before this conclusion 
could be reached, several possibilities require to be attended 
to. In the first place, flame in Nature is an exceedingly rare 
phenomenon, so that we coTild scarcely expect that any 
instinct should have been developed for the express purpose 
of its avoidance. Therefore, if the general economy of night- 
flying insects is such that it is of advantage to approach and 
examine shining objects, there would be nothiug anomalous 
in their failing to distinguish between flame and other 
shining objects — such as white flowers or, in the case of 
moths, pale coloured members of tlie opposite sex. But as 
the instinct of flying into flame is of such general occurrence 
among many species of insects, I think we certainly cannot 
attribute all the cases of it to a mistaking of flame for some 
other shining object ; to meet all the cases some still more 
general explanation is required, and this, I think, is afforded 
by considering other and analogous cases. Thus many 
species of birds display an exactly similar propensity, as is 
proved by the experience of lighthouse keepers ; and, accord- 
ing to Professor A. Newton, some species of birds are more 
readily attracted by light than others.* Here there can be 
no question about a possible mistaking of flame for white 
flowers, &c., and therefore the habit must be set down to 
mere curiosity, or desire to examine a new and striking 
object ; and that the same explanation may be given in the 
case of insects seems not improbable, seeing that it must 
certainly be resorted to in the case of flsh, which, as I pointed 
out in " Animal Intelligence," are likewise attracted by the 
light of lanterns, &c. ; and the psychology of a fish is not 
much, if at all, in advance of that of many insects. 

Thus, in any case, it seems certain that we have no reason 
to regard the propensity in question as an expression of any 
instinct specially formed with reference to flame, and this is 
really the only point with which we are directly concerned. 
But, as the subject is in itself an interesting one, I shall here 
add a few remarks with reference to other aspects of it. 

Among Mr. Darwin's MSS I find the following note, 
which, however, is not in his hand-writing. 

" Query. Why do moths and certain gnats fly into candles, 
and why are they not all on their way to the moon — at least 

* YarreWs Brit. Birds, 4tli ed., II, 235 



280 MENTAL EVOLUTION IN ANIMALS. 

when the moon is in the horizon ? I formerly observed that 
they fly very much less at candles on a moon-light night. 
Let a cloud pass over, and they are again attracted to the 
candle." 

I do not know to whom this observation is due ; but I 
quote it for the sake of the query. The answer, I think, 
must be, that as the moon is a familiar object, the insects 
regard it as a matter of course, and so have no desire to 
examine it. I have little doubt that if moonlight were con- 
centrated to a point in a dark room, the moths and gnats 
would approach it. 

In " Nature " (vol. xxv, p. 436), Mr. J. S. Gardener 
writes : — 

" Whilst watching the great horse-shoe falls of the Skjal- 
fandafljot near Sjosavan in Iceland, I saw moth after moth 
fly deliberately into the falling water and disappear. Some 
which I noticed arriving from a distance, fluttered at first 
deviously, but as they neared the water flew straight in. The 
gleaming falls seemed at least as attractive as artificial 
light." And doubtless the same explanation applies, inas- 
much as a gleaming waterfall is not a sufficiently common 
object in Nature, either to fail in arresting the curiosity of 
the moths, or to ensure that a special instinct should be 
developed to warn the insects from approaching it. 

o. Mr. Darwin in the Appendix points out two or three 
cases of instinct which are apparently at first sight detri- 
mental to the species exhibiting them. Thus, the crowing of 
the cock-pheasant on goiug to roost reveals his presence to 
the poacher, the cackling of a hen after having laid an egg 
informs the natives of India where the nest is concealed, 
certain birds place their nests in very conspicuous situations, 
and a kind of Shrew-mouse betrays itself by screaming when 
approached. Now it seems to me that in all these cases — 
and many similar or analogous ones might be given — the 
diificulty is, if I may use the term, fictitious ; for it only arises 
when we shut our eyes to some of the most important prin- 
ciples which in the previous chapters I have been endeavour- 
ing to explain. These principles do not imply that an instinct 
should ever be formed or modified with reference to a prospec- 
tive change of environment, while thiey do imply that when 
such a change has taken place, time must be allowed for 
the compensating modification of the instinct — even suppos- 



INSTINCTS APPARENTLY DETEIMENTAL TO THE SPECIES. 281 

ing that any such modification is urgently required. Now it 
can scarcely be held probable on these principles that tlie 
instinct of crowing on the part of the pheasant should have 
been modified by natural selection during tlie short time that 
his ancestors have been naturalized in this country, and in 
consequence of one in a hundred having thus fallen a victim 
to poachers. The case of a wild hen cackling over its eggs 
may seem a stronger one ; but here again the whole question 
really consists in the actual percentage of eggs thus discovered 
by the natives, and I should think this must be exceedingly 
small. Birds building in exposed situations only become an 
argument against the modificability of instinct by natural selec- 
tion, when it is shown that the exposure has led to tlie destruc- 
tion of nests by man or other animals for a great number of 
generations ; and this has never been shown. Even in the 
most remarkable case — that of the Furnarius of La Plata — 
Mr. Darwin merely says that this bird " in a thickly peopled 
country, with mischievous boys, loould soon he exterminated." 
And similarly it would require to be shown that the habit of 
the Shrew-mouse at the Mauritius has long led to the 
destruction of many individuals of each generation by man. 

In all such cases we must remember how very insignifi- 
cant the influence of man — and especially of savage man — 
usually is, as compared with the sum of other influences, 
organic and inorganic ; we must remember the time which 
in any case is required for the modification of an instinct ; 
and we must have proof that the instinct Avhich is now in- 
jurious in some percentage of cases, has long been highly 
injurious in a large percentage of cases. I am not aware of 
any instance where all these conditions have been fulfilled, 
and where the species has not either been exterminated by 
man, or the required modification of instinct has not actually 
taken place. 

4. Mr. Darwin in the Appendix also alludes to the in- 
jurious effects which frequently attend the exercise of the 
instinct of migration in certain animals. Thus, he says, the 
congregating of quadrupeds in Africa, and of the Passenger 
Pigeons iji America is detrimental to the animals, in conse- 
quence of their being thus readily followed by beasts of prey 
as well as by man. But when we remember the enormous 
numbers of both kinds of animals which thus congregate, I 
cannot see that any difficulty remains ; for not only is the 



282 MENTAL EVOLUTION IN ANIMALS. 

percentage of individuals destroyed in itself small, but I 
doubt whether it is mucli larger than would be the case if 
these multitudes of animals were segregated over a very much 
wider area. A stronger case, I think, is afforded by that of 
the Norwegian Lemming, and therefore I shall consider it at 
greater length. 

Since Mr. Darwin wrote his remarks on this subject 
which are presented in the Appendix, further statements with 
reference to it have been published. These, therefore, I shall 
quote. 

Mr. Crotch, who has had the opportunity of observing the 
phenomena for a number of years, thus briefly gives his 
account of the facts, so far as they concern us. 

" The Lemmings (which are little rodents) certainly do 
not visit my part of Norway at any recurring period of 
years ; but every third or fourth year they may be expected 
with tolerable regularity, though in variable numbers. Thus 
it is quite probable that some migrations may have so far 
escaped notice as to give rise to the old idea that they took 
place every tenth year. 

" They are, hoAvever, always directed westwards ; and 
thus the theory that they are caused by deficiency of food 
fails so far, that these migrations do not take place in a 
southerly direction by which a larger supply might be ob- 
tained. M. Guyne {loc. cit.) suggested that the course fol- 
lowed was merely that of the watershed. However, this runs 
east as well as west, and follows valleys which often run 
north and south for hundreds of miles, whereas the route 
pursued by the Lemming is due west. At all events this is 
the case in Norway, where they traverse the broadest lakes 
filled with water at an extremely low temperature, and cross 
aKke the most rapid torrents and the deepest valleys. 

" With no guiding pillar of fire, they pass on through a 
wilderness by night ; they rear their families on their journey, 
and the three or four generations of a brief subarctic summer 
serve to swell the pilgrim caravan. They winter beneath 
more than six feet of snow during seven or eight weary 
months ; and with the first days of summer (for in those 
regions there is no spring) the migration is renewed. At 
length the harassed crowd, thinned by the increasing attacks 
of the wolf, the fox, and even the reindeer, pursued by 
eagle, hawk and owl, and never spared by man himself, yet 



INSTINCTS APPARENTLY DETRIMENTAL TO THE SPECIES. 283 

still a vast multitude, plunges into the Atlantic Ocean on 
the first calm clay and perishes with its front still pointing- 
westward. No faint heart lingers on the way, and no sur- 
vivor returns to the mountains. Mr. R. CoUett, a Norwegian 
naturalist, writes that in November, 1868 (quoted by Fille- 
burg, infra), a ship sailed for fifteen hours through a swarm of 
Lemmings, which extended as far over the Trondhjemsfiord as 
the eye could reach."* 

Such, according to Mr. Crotch, are the facts, and the follow- 
ing are the hypotheses which have been propounded to ex- 
plain them. Mr. Wallace suggests! that natural selection has 
played an important part in causing migration, by giving an 
advantage to those animals which enlarge their breeding area 
by travel. To this view, as applied to the lemming, Mr. 
Crotch objects that the animal, " it is true, always breeds 
during migration ; but if none return or survive, it is difficult 
to say what becomes of the fittest." His own theory is a 
remarkable one. " There is," he says, " a solution of this 
difficulty, involving a subject of the deepest interest, and 
which led me to spend two years in the Canaries and adjacent 
islands. I allude to the island or continent of Atlantis. . . 
It is evident that land did exist in the North Atlantic Ocean 
at no very distant date. . . . 1 3 it not then conceivable, 
and even probable, that when a great part of Europe was 
submerged and dry land connected Norway with Greenland, 
the lemmings acquired the habit of migrating westward for 
the same reasons which govern more familiar migrations ? 
. . . It appears to me quite as likely that the impetus 
of migration towards this continent should be retained as 
that a dog should turn round before lying down on a rug, 
merely because his ancestors found it necessary thus to 
hollow out a couch in the lorug grass." 

In a later paperj he combats by the aid of charts the 
popular theory " that these migrations follow the natural 
declivities of the country," and then proceeds to add, " It is 
very remarkable that the average depth from Norway to Ice- 
land does not exceed 250 fathoms, with the exception of a 
deep and narrow channel of 682 fathoms at 14° W. This 
probably represented the old Gulf Stream; and if this were 
so, the lemmings did wisely to migrate westwards in search 

* Linn. Soc. Jour., toI. xiii, p. 30, et seq. t Mature, toI. x, p. 459. 
X Linn. Soc. Jour., vol. xiii, p. 157, et ,seq. 



234 MENTAL EVOLUTION IN ANIMALS 

of its genial influence. As little by little the ocean encroached 
on the land, the same advantages would remain, as in fact 
they do to this day." 

To this ingenious theory dissent is expressed by another 
gentleman who has had a very large experience in observing 
these migrations, namely Mr. Robert Collett, of the University 
Museum, Christiania.* His view is that in years when re- 
production is excessive, multitudes of individuals are led by 
hunger, as well as by " the natural desire to wander possessed 
by tliis species," to overflow the limits of their plateaux 
home, and spread out " over an area that is considerably 
larger than obtains in any other of the species under similar 
circumstances." As breeding continues throughout the 
wandering, in cases where in two or three succeeding years 
the production of young has been excessive, " the masses 
are incessantly pushed towards the sides of the fells ; and 
the migration becomes an overrunning of the lower and far 
remote portions of the country, as the individuals gradually 
penetrate further in search of localities suitable to their 
habits (and which are capable of giving them a permanent 
subsistence), until they are stopped by the sea or destroyed 
in some other manner." 

Looking to Mr. Collett's large experience on the subject, 
as well as to the intrinsically probable nature of his views, I 
think we may most safely lend countenance to the latter. 
The most important point of difference between Mr. Crotch 
and Mr. Collett has reference to a question of fact. For 
while Mr. Crotch states that the migrations are made west- 
wards without reference to the declivities of the country, 
Mr. Collett is emphatic in saying that " the wanderings take 
place in the direction of the valleys, and therefore can branch 
out from the plateaux in any direction." If this is so, there 
is an end of Mr. Crotch's theory, and the only difficulty left 
to explain would be why, when the lemmings reach the sea, 
they still continue on their onward course to perish in their 
multitudes by drowning. The answer to this, however, is 
not far to seek. For their ordinary habits are such that when 
in their wanderings they come upon a stream or lake, they 
swim across it ; and therefore when they come upon the coast 
line it is not surprising that they should behave in a similar 
manner, and, mistaking the sea for a large lake, swim per- 

* Linn. Soc. Jour., vol. xiii, p. 327, ei seq. 



MIGRATION. 235 

sistently away from land with tlie view to reaching the 
opposite shore, till they succumb to fatigue and the waves. 
Therefore, pending further observations on the question of 
fact above alluded to, I cannot feel that the migration of the 
lemming furnishes any difficulty to the theory of evolution 
over and above that which is furnished by the larger and 
more important case of migration in general, to the considera- 
tion of which I shall now proceed. 

Migration, 

Taking the animal kingdom from below upwards, the first 
animals that can properly be said to present the instincts of 
migration are to be found in the group Articulata. I think it 
is sufficient to refer to " Animal Intelligence " for the facts 
concerning the migrations of Crabs (pp. 231-2)* and Cater- 
pillars (238-40), though as regards the latter I may add the 
following remarkable account, which I quote from the 
" Colonies and India." 

" To say that a train had been stopped by caterpillars 
would sound like a Yankee yarn, yet such a thing (according 
to the " Eangitikei Advocate ") actually took place on the 
local railway a few days ago. In the neighbourhood of Tura- 
kina. New Zealand, an army of caterpillars, hundreds of 
thousands strong, was marching across the line, bound for a 
new field of oats, when the train came along. Thousands of 
the creeping vermin were crushed by the wheels of the 
engine, and suddenly the train came to a dead stop. On 
examination it was found that the wheels of the engine had 
become so greasy that they kept on revolving without ad- 
vancing — they could not grip the rails. The guard and the 
engine-driver procured sand and strewed it on the rails, and 
the train made a fresh start, but it was found that during the 
stoppage caterpillars in thousands had crawled aU over the 
engine, and over all the carriages inside and out." 

With regard to Butterflies many instances of large migra- 
tions are on record. Thus, Madame de Meuron Wolff describes 
an immense swarm of the Painted Lady butterfly passing 
over Grandson, Canton de Vaud, flying closely together from 
south to north. The column, which was from ten to fifteen 
feet broad, flew low and equally, and took two hours to pass. 

* See also Professor Moseley, A Naturalist on the Challenger, p. 561. 
13 



286 MENTAL EVOLUTION IN ANIMA.LS. 

The caterpillar of this species is not gregarious. Professor 
Bonelli also describes a migration similar in all respects, 
including locality, except that it lasted longer — the insects 
covering the flowers at night and proceeding on the journey 
by day. 

Immense swarms of migratory Dragon-flies have been at 
times observed, the most remarkable case being one that 
occurred in May, 1839, and which seems to have extended 
over a great part of Europe. The insects flew at a height of 
100 to 150 feet, and seemed to follow the direction of the 
rivers.* 

Many species of Fish are known to migrate regularly for 
purposes of spawning, such as the herring, salmon, &c., and 
also to find water ; f while among Eeptiles the most remark- 
able instance seems to be that which is furnished by the 
Turtles which visit Ascension Island to deposit their eggs. 
How the animals can find this comparatively small speck of 
land in the midst of a vast ocean is very unaccountable. I 
have recently written to Professor Moseley upon the subject, 
and in reply he says, " No man without proper modern 
means of finding latitude and longitude could reach either 
Tristan or Ascension ; and it is especially difficult for 
animals whose eyes cannot be raised above the sea-level, and 
to whom, therefore, the islands are visible for a comparatively 
small radius only. Merchant skippers have several times 
been unable to find Bermuda, and on return baflled have 
reported the island gone down." But, as Professor Moseley 
adds, " It is just possible that the animals do not retire far 
from the land after all, but hang about unobserved," I think 
it is undesirable to enter into any discussion where the facts 
are still of an uncertain character. 

Among Mammals, from whales to mice, we meet with 
many migratory species, but it is among Birds that the 
propensity is most prevalent. Indeed, a very competent 
authority on all matters pertaining to ornithology has said in 
the new " Encyclopaedia Britannica : " " Every bird of the 
northern hemisphere is to a greater or less degree migratory 
in some pai't of its range. Such a conclusion brings us to a 
still more general inference — viz., that Migration, instead of 

* For a full account see Weissenborne, Loundonti's Mag. Nat, HiU.y 
N.S., vol. iii. 

t tSco Animal Intelligence, 218-50. 



MIGRATION. 287 

"being the exceptional characteristic it used formerly to be 
thought, may really be almost universal."* 

I have neither the occasion nor the space to discuss the 
large question of migration in general ; and having now 
indicated the animals in which the instinct is most pro- 
nounced, I shall pass on to consider the theory of its forma- 
tion. First I may allude to Mr. Darwin's remarks on 
Migration at the beginning of the Appendix. It will be 
seen from them that among others he establishes the follow- 
ing points : — 

1. There is " in different breeds of birds a perfect series 
from those which occasionally or regularly shift their quarters 
within the same country, to those which periodically pass to 
far distant countries." 

2. " The same species often migrates in one country and 
is stationary in another ; or different individuals of the same 
species in the same country are migratory or stationary." 

3. " The migratory instinct is made up of two very distinct 
factors — viz., an impulse to travel periodically, and a faculty 
of knowing the direction in which to travel." 

4. " Savage man shows a sense of direction which may be 
analogous to that shown by migratory animals." 

5. " Certain cases are on record of breeds of domesticated 
animals having truly migratory instincts." 

Such being the data, the problem is to account for the 
origin of the instinct. Mr. Darwin's theory is that the 
ancestors of migratory animals were annually driven, by cold 
or want of food, slowly to travel southwards ; " and in time 
we may well believe that this compulsory travelling would 
become an instinctive passion," as is the case with domesti- 
cated sheep in Spain. In the case of birds, the wings would 
be used, and if in the course of many successive generations 
the land over which they flew in their annual journeys were 
to become slowly submerged, the line of flight would remain 
unaltered, and thus we should have the state of things which 
we now perceive — viz., migratory birds flying over wide 
stretches of ocean. 

Before I proceed to consider this theory, I should like to 
call prominent attention to the fact that it has been inde- 

* Professor Newton, F.R.S., Art. Birds, where see for a good rtiume of 
the main facts of migration aa regards birds. 



288 MENTAL EVOLUTION IN ANIMALS. 

pendently arrived at by Mr. Wallace. It is only now that 
Mr. Darwin's views upon this subject are published, although 
they were committed to writing as they appear in the 
Appendix between twenty and thirty years ago. Mr. Wallace 
however enunciated substantially the same views in a letter 
to "Nature" in 1874 (Oct. 8),* from which I shall quote in 
extenso, not only for the purpose of showing the coincidence 
to which I have alluded, but also because I think that the 
additional element which Mr. Wallace mentions — i.e., the 
separation of breeding and subsistence areas — is a most im- 
portant one. 

" Let us suppose that in any species of migratory bird, 
breeding can as a rule be only safely accomplished in a given 
area ; and further, that during a great part of the rest of the 
year sufficient food cannot be obtained in that area. It will 
follow that these birds which do not leave the breeding area 
at the proper season will suffer, and ultimately become 
extinct ; which will also be the fate of those which do not 
leave the feeding area at the proper time. JSTow if we sup- 
pose that the two areas were (for some remote ancestor of the 
existing species) coincident, but by geological and climatic 
changes gradually diverged from each other, we can easily 
understand how the habit of incipient and partial migration 
at the proper season would at last become hereditary, and 
so fixed as to be what we term an instinct. It will probably 
be found that every gradation still exists in various parts of 
the world, from a complete coincidence to a complete separa- 
tion of the breeding and subsistence areas ; and when the 
natural history of a sufficient number of species in all parts 
of the world is thoroughly worked out, we may find every 
link between sj)ecies which never leave a restricted area in 
which they breed and live the whole year round, to those 
other cases in which the two areas are absolutely separated. 
The actual causes that determine the exact time, year by 
year, at which certain species migrate, will of course be diffi- 
cult to ascertain. I would suggest, however, that they will 
be found to de]iend on those climatic changes which most 
affect the particular species. The change of colour, or the 
fall of certain leaves; the change to the pupa state of 
certain insects ; prevalent winds or rains ; or even the 

* Captain Hutton also foreshadowed tliese views in 1872; see Trane. 
New Zealand Inst., p. 235. 



MIGRATION. 289 

decreased temperature of the earth and water, may all have 
their inHuence." 

It will be observed that this theory, besides being intrin- 
sically probable, derives a good deal of support from the 
enquiries made by Mr. Darwin, which have shown that there 
is a general relationship between oceanic islands which there 
is independent reason to conclude have never been joined to 
the mainland, and an absence of migratory birds.* 

It will also be observed this theory makes two important 
assumptions — first, that the birds have a very accurate sense 
of direction, and second, that a no less accurate knowledge of 
the particular direction to be pursued is inherited ; for it is 
certain that the young Cuckoo (which leaves England after 
its parents) cannot be guided on its first journey by any other 
means, and it is asserted that the same is true of the young 
of many other species.f Taking then these assumptions 
separately, the first is no more than a statement of fact, un- 
accountal)le though the fact may be. That is to say, a very 
accurate sense of direction migratory birds unquestionably 
possess, and it is probably the same in kind as the so-called 
" homing " faculty which is shown by many domesticated 
animals, and also, as Mr, Darwin points out, by savage man. 
I could fill pages with letters which I have received from 
all parts of the world describing more or less remarkable 
cases of the display of this faculty by dogs, cats, horses.J 

* To be quite fair, however, I must here allude to the only fact I hare 
met with which seems to me opposed to this theory. Mr. Uurdis in his 
work entitled The Naturalist in £ermi<da, observes that the migratory golden 
plover {Charadriits marmoratus) passes over the islands in countless multi- 
tudes (but without ever alighting) on the journey south, while they are never 
seen passing over the islands on their return journey north. Now, if it is a 
fact that the two journeys are taken by difierent routes, a difficulty would be 
encountered by the above theory ; but as Mr. Hurdis says that the bii'ds fly 
at an enormous height while passing over the islands on their southern 
journey, it is not, I think, impossible that they may take the same route on 
theu" northern journey, although at a still higher elevation, and thus escape 
notice. 

t See Temminck, Man. cfOrn., ed. 2, iii, Introd., p. xliii, and Seebohm, 
Siberia in Europe. On the other hand Leroy says that in the case of swallows 
" those who have had no instruction do not migrate, and the young birds 
are seen to be led by those whose age and experience give them knowledge 
and authority ;" and adds that if a brood are hatched out too late to accom- 
pany the old birds in their migration, " it is in vain that they reach maturity 
. . . . they perish the victims of their ignorance, and of the tardy bii-th 
which made them unable to follow their parents " {loc. cit., pp. 183-4). 

J I have one instance of a cat returning in four days from London to 



290 MENTAL EVOLUTION IN ANIMALS. 

asses, cows, sheep, goats, and pigs ; but as so many similar 
cases are already on record, I feel it is needless to add to the 
number. The remarkable fact is that the animals are able 
to find their way back over immense distances, even though 
the outgoing journey has been made at night, or in a closed 
box ; so that it is truly upon some sense of direction, and 
not merely upon a memory of landmarks, that they must 
rely. Moreover, it is certain that in many cases, if not as a 
general rule, the animals on their return journey do not 
traverse the exact route which they had taken in the out- 
going journey, bat take the " bee-line ";* so that, for instance, 
if the out-going journey has been made over two sides of 
a triangle, the return journey will most probably be made 
over the third side. One instance, the account of which I 
have received from a correspondent in Australia, is of suffi- 
cient interest in this connection to quote. " A pair of horses 
were sent many hundred miles round the Australian coast by 
ship ; as they did not like their new quarters, they started 
back by land ; but after returning 230 miles they were pulled 
up by a peninsula on the coast, where they were eventually 
recovered. They did not attempt to retrace their steps to 
clear this difficulty ."t 

HuddersfJeld, a distance of two hundred miles. A still more remarkable case, 
however, was published by Mr. J. B. Andrews in Nature several years ago 
(vol. viii, p. 6). The Archduchess Marie Regnier passed the winter of 1871-2 
at the Hotel Victoria, in Mentone, and while there took a fancy to a spaniel 
belonging to the landlord, M. Milandri. In the spring of 1872 she brought 
the dog with her by rail to Vienna. Not long afterwards it reappeared at the 
hotel in Mentone, having thus run a distance of nearly a thousand miles. On 
arriving it died of fatigue and was buried in the hotel gardens, where a 
monument now commemorates the performance. Mr. A. W. Howitt writing 
to Nature from Victoria at about the same time (vol. viii, p. 322) gives a 
number of cases of horses and cattle finding their way home over greater or 
less distances, and I specially allude to his communication because he saya 
that in some of the cases the return journey was made after a considerable 
lapse of time — months and even years. 

* This is an American term which I employ becaxise in itself showing 
the observed regularity of the fact as regards bees — it being the custom to 
find wild hives of honey by catching several bees, and letting them go again 
from different places. Tlie insects under these circumstances make straight 
for their hive, so that by observing the point whei'e several " bee-lines " 
intersect, the honey seekers are able to find the hive. 

t I may here also quote an observation by Mr. Darwin to the same effect : — 
" I sent a riding-horse by railway from Kent via Yarmouth, to Freshwater Bay, 
in tlio Isle of Wight. On the first day that I rode eastward, my horse, when 
I turned to go home, was very unwilling to return towards his stable, and he 
several times turned round. This led me to make repeated trials, and every 



MIGRATION. 291 

N"ow it is evident that this fact alone — i.e., of animals not 
requiring to return by the same route — is sufficient to dis- 
pose of the hypothesis advanced by Mr. Wallace* to the effect 
that the return journey is due to a memory of the odours 
perceived during the out-going journey, these odours thus 
serving as land- marks. Therefore it seems to me there are 
only two hypotheses open to us whereby to meet the facts. 
First, it has been thought possible that animals may be 
endowed with a special sense enabling them to perceive the 
magnetic currents of the earth, and so to guide themselves as 
by a compass. There is no inherent impossibility attaching 
to this hypothesis, but as it is wholly destitute of evidence, 
we may disregard it. The only other hypothesis is that 
animals are able to keep an unconscious register of the turns 
and curves taken in the outgoing journey, and so to retain a 
general impression of their bearings. This hypothesis is 
substantiated by the fact that, as Mr. Darwin observes, 
savage man is certainly endowed with some such faculty; 
and a friend of my own (Mr. Henry Forde quoted below), 
who has spent many years in the forests and prairies of 
America, informs me that even civilized man when long 
accustomed to such primitive habits of life, acquires this 
faculty in a degree of perfection quite comparable with that of 
savages. He also informs me that, occasionally, without any 
assignable reason, the sense of direction becomes confused, 
leading to a distressed sensation of bewilderment. He has 
seen a hunter thus reduced to a lamentable condition of 
nervousness, and when at last he abandoned himself to the 
leadership of his companions (who relied entirely on their 
own sense of direction), he felt persuaded that they were 
going the wrong way. But on approaching his dwelling- 
place he recognized one of the trees, and declared that a 
particular notch upon it had passed round to the other side 
of the trunk. Eventually he said that the whole world 

time tliat I slackened tlie reins, tie turned sliarply round and began to trot to 
tlie eastward by a little north, •wbicli was nearly in the direction of his home 
in Kent. I had ridden this horse daily for several years, and he had never 
before behaved in this manner. My impression was that he somehow knew 
the direction whence he had been brought. I should state that the last stage 
from Yarmouth to Freshwater is almost due south, and along this road he 
had been ridden by my groom ; but he never once showed any wish to return 
in this direction " {Nature, vol. vii, p. 360). See also Nature, viii, p. 322. 
* Nature, loc. cit. 



292 MENTAL EVOLUTION IN ANIMALS. 

seemed to have turned round him as a centre. In this con- 
nection I may quote the following passage from a letter 
pubhshed some years ago by Mr. Darwin in " Nature " 
(vol. vii) : — 

" The manner in which the sense of direction is sometimes 
suddenly disarranged in very old and feeble persons, and the 
feeling of strong distress which, as I know, has been experi- 
enced by persons when they have suddenly found out that 
they have been proceeding in a wholly unexpected and wrong 
direction, leads to the suspicion that some part of the brain" 
is specialized for the function of direction. Whether animals 
may not possess the faculty of keeping a dead-reckoning of 
their course in a much more perfect degree than man ; or 
whether this faculty may not come into play on the com- 
mencement of a journey, when an animal is shut up in a 
basket, I will not attempt to discuss, as I have not sufficient 
data." He also alludes to the case of Audubon's pinioned 
wild goose, which showed a very determined impulse to 
migrate at the proper season, but mistook the direction and 
went due north instead of south. 

Lastly, I may quote the following from Dr. Bastian's 
work on the Brain.* 

" On this subject, G. C. Merrill, writing from Kansas, 
says : — 

' I have learned from the hunters and guides who spend 
their lives on the plains and mountains west of us, that no 
matter how far, or with what turns, they may have been led, 
in chasing the bison or other game, they, on their return to 
camp, always take a straight line. In explanation, they say 
that, unconsciously to themselves, they have kept all the 
turns in their mind.' 

" Eeferring to his travels in the State of Western Virginia, 
Mr. Henry Forde (' Nature,' April 17, 1873, p. 463) writes 
as follows : — ' It is said that even the most experienced hun- 
ters of the forest-covered mountains in that unsettled region 
are liable to a kind of seizure — that they ' lose their heads ' 
all at once, and become convinced that they are going in 
quite the contrary direction to what they had intended, and 
that no reasoning nor pointing out of land-marks by their 
companions, nor observations of the position of the sun, can 

* Brain as an Organ of Mind, p. 215, where see also for cases of way- 
fiudin" in animals. 



MIGRATION, 293 

overcome their feeling ; it is accompanied by great nervous- 
ness and a general sense of dismay and ' upset.' The nervous- 
ness comes after tbe seizure, and is not the cause of it. This 
is spoken of by the natives as ' getting turned round.' The 
feeling sometimes ceases suddenly, or it may wear away 
gradually. Colonel Lodge, in his ' Hunting Grounds of the 
Far West,' 1876, speaks of the same kind of feeKugs seizing 
upon, and occasionally demoralizing, old and experienced 
prairie travellers. Indian chiefs all concurred in assuring 
G. Catlin (' Life amongst the Indians,' p. 96) that 'whenever 
a man is lost on the prairies, he travels in a circle, and also 
that he invariably turns to the left ; of which singular fact,' 
the author adds, * I have become doubly convinced by subse- 
quent proofs.' " 

But it is evident that definite experiments on this homing 
faculty, both in men and in animals, are required before we 
can be in a position to say anything more with regard to it 
than admitting it as a matter of fact. The only experiments 
which have been made, so far as I am aware, are those of Sir 
John Lubbock, on the sense of direction in the Hymenoptera 
(to which I shall allude presently), and those which have 
more recently been published by M. Fabre,* who also ex- 
perimented upon the Hymenoptera. As the last-named 
author believes that he has established a very definite conclu- 
sion by means of his experiments, it is necessary that I 
should make a few remarks upon them. 

At the suggestion of Mr. Darwin, he placed some marked 
mason-bees in a closed paper box, carried them thus im- 
prisoned for some distance in one direction, then rotated the 
box and carried them a much greater distance in the opposite 
direction, after which he released the insects. He found 
that when the distance to which the bees were taken was as 
much as three kilometres, and even when the rotation was 
very considerable (the box being placed in a sling and 
rotated in various planes at several points in the route) a 
certain percentage of the bees returned home. It made no 
difference whether the bees were released in an open space or 
in a thick wood ; neither did it make any difference whether 
the outgoing journey were performed in a straight line or in 
a circuitous curve. From these experiments M. Fabre con- 

* N'oKveaj.x Souvenirs Entomologiques, 18S2, pp. 09-123. 



294 MENTAL EVOLUTION IN ANIMALS. 

eludes that the sense of direction cannot depend upon any- 
process of dead-reckoning. At the suggestion of Mr. Darwin 
he also tried the effect of attaching a magnetized needle to 
the thorax of a hee ; but the bee having succeeded in getting 
rid of the encumbrance, he did not repeat the experiment. 

Now, although the observations with the rotating box are 
no doubt very interesting, they do not appear to me to sustain 
the definite conclusion that the sense of direction is not due 
to a process of dead-reckoning. It is of course impossible 
to suppose that the bees could retain a register of all the 
turns to which they were submitted in the sling, and, there- 
fore, if it were certain that they found their way home by 
means of their sense of direction, I should agree with 
M. Fabre in concluding, once for aU, against the theory of 
dead-reckoning. But there is no evidence to show that the 
bees which found their way home did so by means of their 
sense of direction. It is quite possible that they found their 
way home simply from their knowledge of land-marks ; for 
the distance to which they were taken was only three kilo- 
metres, and it is known that the hive-bee will go three times 
that distance in its ordinary foraging excursions.* Moreover, 
the fact that only a comparatively small number of the bees 
succeeded in returning (about 22 per cent.), is suggestive of 
the explanation that these were the only ones which, during 
the random flight of the whole number in sundry directions, 
happened to encounter land-marks with which they were 
familiar. I am therefore inclined to feel that any sense of 
direction which existed in these insects may very well have 
been rendered useless by these experiments, and yet that the 
results of the experiments might have been exactly those 
which M. Fabre describes. 

Eeturning, however, to the case of migration, I think it is 
not very improbable that the sense of direction may be greatly 
assisted by observing the direction of the sun with reference 
to the appropriate line of flight. It is true that many migra- 
tory birds fly at night ; but in this case, even if the moon is 
not available to steer by instead of the sun, during much of 
the night the directions of sun-set and sun-rise are clearly 
indicated by the light of the sky ; and it appears that on 
very dark and cloudy nights migratory birds are apt to become 

* Sec Animal Intelligence, p. 150. 



MIGRATION. 295 

confused.* The possibility thus suggested receives, I think, 
some countenance from the following fact. In "Animal 
Intelligence " I recorded a number of observations which had 
been made by Sir John Lubbock on the sense of direction as 
exhibited by ants. These experiments yielded results of a 
most definite nature, and thus led Sir John to conclude that 
ants are endowed with the sense of direction in a singular 
degree. Subsequently, however, he has found (accidentally 
in the first instance) that in all these experiments the ants 
found their way by observing the direction in which the light 
was falling; so that, as long as the source of light was 
stationary, no matter how many times he turns them round 
upon a rotating table, when the rotation ceased they knew 
their road to and from the hive as well as they did before the 
rotation; whereas, if the source of light were shifted, the 
insects at once became confused as to their bearings, even 
though not rotated at all.f Now if ants thus habitually 
guide themselves by observing the direction in which the 
light is falling (i.e., the position of the sun), I do not see why 
migratory birds should not be assisted by similar means. 

This, however, I only put forward as a conjecture. The 
fact that migratory birds, like many other animals, are in 
some way able to hold a true course in order to reach a par- 
ticular locality, is a fact which confessedly we are not able to 
explain. But — and this is the most important point for us — 
our inability to explain this fact in the present state of our 
information, is no objection to the theory of instinct on which 
we are engaged. We cannot doubt that the fact admits of 
some explanation, and when we certainly know what this 
explanation is, we shall first be able to ascertain whether the 
faculty of way-finding is or is not compatible with the 
foregoing theory of the evolution of instinct. 

Let us turn now to the second of the two assumptions 
above alluded to as necessary in order to embrace the facts of 
migration under the theory — viz., the assumption that some 
at least among migratory birds must possess, by inheritance 
alone, a very precise knowledge of the particular direction to 

* See Professor Newton in Nature, vol. xi, p. 6, vrho says, " Dark cloudy 
nights seem to disconcert the travellers. On such nights the attention of 
others besides myself has often been directed to the cries of a mixed multitude 
of bu'ds hovering over this (Cambridge) and other towns, apparently at a 
loss whither to proceed, and attracted by the light of the street lamps." 

t See Journ. Linn. Soo., 1883. 



296 MENTAL EVOLUTION IN ANIMALS. 

be pursued. It is, without question, an astonishing fact that 
a young cuckoo should be prompted to leave its foster-parents 
at a particular season of the year, and without any guide to 
show the course previously taken by its own parents ; but 
this is a fact which must be met by any theory of instinct 
which aims at being complete. Now upon our own theory it 
can only be met by taking it to be due to inherited memory. I 
confess to me it seems incredible that many hundred miles of 
landscape scenery should constitute an object of inherited 
memory,* to say nothing of long stretches of ocean ; but the 
case is not quite so hopeless as to require so extreme a 
liypothesis. When we say that upon our theory the young 
cuckoo must be supposed to find its way on its first journey 
by inherited memory, we need not necessarily affirm that this 
is the memory of a landscape. As I have said in the pre- 
vious paragraphs, we do not yet know what it is that guides 
the course of migratory birds in general ; but whatever this 
may be, it can scarcely be the appearance of the country over 
which they pass, seeing not only that the distances are so 
great and that two hundred or three hundred miles of ocean 
may separate one piece of country over which they travel 
from another, but also that the journeys may be taken by 
night. Of what, then, is the inherited memory on which the 
young cuckoo (if not also other migratory birds) depends ? 
We can only answer, Of the same (whatever this may be) as 
that upon which the old birds depend. When we certainly 
know what this is, we shall first be able to ascertain whether 
it is incompatible with the theory of evolution to suppose 
that it can be an object of hereditary memory. Thus, for the 
sake of example, let us suppose that the old birds in their 
outgoing journey guide their way by flying towards the south 
wind (as has been suggested to me by Mr. William Black, 
who believes that swallows always start against the south 
wind) ; heredity would in this case have an easy task in 
associating the warm moist breath of this wind with a desire 
to fly against it. Of course I only adduce this suggestion in 
order to show how simple the mere question of heredity 
might become, if once we knew the means whereby migratory 
birds in general find their way. The only difference between 
the faculty of homing and the instinct of migration, so far as 

* This theory was first advanced by Canon Kingsley (Nature, Jan. 18, 
1867), and has since been independently suggested by several writers. 



INSTINCTS OF NEUTER INSECTS. 297 

the matter of way-finding is concerned, seems to me to be 
this — that in the case of the young cuckoo, and perhaps also 
in that of certain other migratory birds, the animals know 
their way instinctively, or without even one lesson. But if 
we could ascertain upon what it is that the faculty of homing 
depends (which, be it observed, is not an instinct, seeing that 
its occurrence is the exception and not the rule, even in the 
species which exhibit it), we might very probably get a clue 
to explain the manner in which heredity has been able to 
work up this faculty into the instinct of migration. 

No doubt this discussion is most unsatisfactory, and the 
reason is that we are so much in the dark about the facts. 
All, therefore, that I have attempted to do is to show that, in 
the present state of our information, the migratory instinct 
cannot fairly be quoted as a difficulty in the way of our 
theory of the formation of instincts in general. And, in 
order to give emphasis to this statement, I may allude to the 
general facts already mentioned — viz., that the migratory 
instinct is both variable and graduated, that it is occasionally 
exhibited by domesticated animals, and that the sense of 
direction on which it depends is a very general one among 
animals, if not also in savage man ; for all these facts tend to 
show that whatever the causation of the migratory instinct 
may be, it has probably been proceeding upon the lines of 
evolution in general. 



tj"^ 



Instincts of Neuter Insects. 

Mr. Darwin has pointed out a serious difficulty lying 
against his theory of the origin of instincts by natural selection, 
and one which, as he justly remarks, it is surprising that no 
one should have previously advanced against the well-known 
doctrine of inherited habit, as taught by Lamarck. The 
difficulty is that among various species of social insects, such 
as bees and ants, there occur " neuter," or asexual individuals, 
which manifest entirely different instincts from the other 
or sexual individuals, and, as the neuters cannot breed, it is 
difficult to understand how their peculiar and distinctive 
instincts can be formed by natural selection, which, as we 
have seen, requires for its operation the transmission of 
mental faculties by heredity. The difficulty is increased by 
the fact that among the termites and many species of ants 



298 MENTAL EVOLUTION IN ANIMALS. 

several varieties or " castes " of neuters occur in the same nest, 
which differ widely from one another both in structure and 
in instincts. The only possible way in which this dif&culty 
can be met is the way in which it has been met by Mr. Darwin, 
viz., by supposing "that selection may be applied to the 
family as to the individual." " 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 its kind ;" 
and similarly, of course, with regard to the instincts of 
neuters. Otherwise stated, we may regard the nest or hive 
as itself an organism of which the sexual insects and the 
several castes of neuters constitute the organs ; and we may 
then suppose natural relation to operate upon this organism 
as a whole, somewhat in the same way as we habitually 
suppose it to operate upon the " social organisms " or com- 
munities of mankind. No doubt, when carefully considered, 
the analogy between a hive and an organism, or even between 
a hive and a social community, is not a close analogy so far 
as the modus operandi of natural selection is concerned ; for in 
the one case the analogue of organs is a variety of separate 
individuals, while in the other case there is no such great 
contrast between different classes of a human community as 
that which obtains among the different castes of an insect 
community. The root of the question really consists in 
whether or not it is possible to suppose that natural selection 
may operate upon specific types as distinguished from indivi- 
dual members of species. During his life-time I had the 
advantage of discussing this question with Mr. Darwin, and 
I ascertained from him that it had greatly occupied his 
thoughts while writing the " Origin of Species ;" but that, 
finding it to be a question of so much intricacy, he deemed it 
unadvisable to enter upon its exposition. It would occupy 
too much space were I to attempt such an exposition here, 
and I have alluded to the subject only because I desire to 
show that it is really this general question which is involved 
in the case of the special difficulty with which we are now 
concerned. On some future occasion I intend to argue this 
general question, and then I shall hope to mitigate the force 
of this special difficulty. I may, however, point to one fact 



INSTINCTS OF THE SPHEX. 299 

wliicli Mr. Darwin has observed, and wliicli is of much 
importance as indicating that the different castes of neuters 
have arisen by degrees, and therefore presumably under the 
influence of natural selection. This fact is that, when care- 
fully searched for, neuters presenting more or less well- 
marked gradations of structure between one caste and another 
may be occasionally found in the same nest.* On the whole, 
therefore, I conclude, with regard to this particular case of 
difficulty, that it is not so formidable as to exclude the 
explanation furnished by the hypothesis of natural selection, 
supposing that we have already accepted this hypothesis as 
explanatory of other and less difficult cases. 

Instincts of the Spliex. 

Several species of this division of the Hymenoptera dis- 
play what I think may be justly deemed the most remarkable 
instincts in the world. These consist in stinging spiders, 
insects, and caterpillars in their chief nerve-centres, in con- 
sequence of which the victims are not killed outright, but 
rendered motionless ; they are then conveyed to a burrow 
previously formed by the Sphex, and, continuing to live in 
their paralyzed condition for several weeks, are at last avail- 
able as food for the larvee when these are hatched. Of course 
the extraordinary fact which stands to be explained is that 
of the precise anatomical, not to say also physiological know- 
ledge which appears to be displayed by the insect in stinging 
only the nerve-centres of its prey. The following, so far as 
is at present known, are the main features of this very sur- 
prising case. 

The same species of Sphex always preys upon the same 
species of victim. When the victim is a spider, the instinct 
of its assailant dictates that a single sting shall be given in 
the large ganglion where, in the case of the spider, most of 
the central nervous matter is aggTegated. When the victim 
is a beetle, the Sphex which preys upon it — there are eight 
species which prey upon two genera — first throws the insect 
upon its back, then embraces it and plunges the sting through 
the membranes between the first and the second pairs of legs ; 
the sting thus strikes the main nerve-centre, which is unusually 
agglomerated in beetles of this genus. When the prey is a 

* See Orirjin of Species, 231-2. 



300 MENTAL EVOLUTION OF ANIMALS. 

cricket, the insect is thrown, as in the previous case, npon its 
back, and while holding it down with her mandibles firmly 
fastened upon the last segment of its abdomen, her feet on 
the sides holding down the body of the cricket — the anterior 
feet holding down the long posterior legs of the prey, and the 
hind feet holding back the mandibles, so as to prevent these 
from biting, and at the same time making tense the mem- 
branous junction of the head with the body — the Sphex darts 
her sting successively into three nerve-centres ; first into the 
one below the neck which she has stretched back for the pur- 
pose, next into the one behind the prothorax, and lastly into 
the one lower down. A cricket thus paralyzed will live for 
six weeks or more. When the prey is a caterpillar, a series 
of six to nine stings are given, one between each of the seg- 
ments of the body beginning from the anterior end ; the 
brain is then partially crushed by a bite with the man- 
dibles.* 

Now so far as the spider and the beetle are concerned, I 
do not see much difficulty presented by the facts to our 
theory of the formation of instincts. For as both the large 
nerve-centres of the Spider and the sting of the Sphex occur 
upon the median line of their respective possessors, if the 
stinging of the ganglion were in the first instance accidentally 
favoured by this coincidence — which appears to me not im- 
probable, seeing that the nerve-centre is thus the most likely 
place for the sting to strike, — it is evident that natural selec- 
tion would have had excellent material on which to work for 
the purpose of developing such an instinct as we now observe. 
Again, in the case of the beetle, M. Fabre expressly notices 
that the only vulnerable point in the hard casing of the 
animal is in the articulation where the Sphex thrusts her 
sting ; so that there is nothing very remarkable in natural 
selection having developed an instinct to sting at the only 
place in the body of the prey where stinging is mechanically 
possible. 

But the case is certainly very different w^ith the cricket 
and the caterpillar ; for here — or at least in the latter case — 
we encounter the extraordinary and unavoidable fact of an 
insect, Mdthout any accidental guiding or mechanically 

* All tlie above facts are taken from the works of M. J. H. Fabre 
(Souvenirs Entomologigues, 1879 and 1883), who was the fii'st to observe and 
describe them. 



INSTINCTS OF THE SPHEX. 301 

imposed necessity, instinctively choosing a number of minute 
points in the uniformly soft body of its prey, with an appa- 
rently very precise knowledge that it is only at these par- 
ticular points that the peculiar paralyzing influence of its 
sting can be exercised. After duly considering this case, I 
must candidly say that I feel it to be the most perplexing 
which has yet been brought to light, and the one which is 
most difficult of explanation upon the principles of the fore- 
going theory. It is, however, most desirable that the facts 
should be more thoroughly investigated, for it might then 
appear that some clue would be given as to the origin and 
development of this instinct. So far as our information at 
present extends, I can only suggest that this origin must have 
been of a purely secondary kind, although its siibsequent 
development may probably have been assisted by natural 
selection. In other words, so far as we have any means of 
judging, I can see no alternative but to conclude that these 
wasp-like animals owe their present instincts to the high 
intelligence of their ancestors, who found from experience 
the effects of stinging caterpillars between the segments of 
their bodies, and consequently practised the art of so stinging 
them till it became an instinct. 

During the last year of his life I had some conversation 
with Mr. Darwin upon this matter, and, after deliberating 
upon it for some time, he eventually came to the conclusion 
which I have just stated — as will be at once apparent from 
the following letter which he wrote to me, and which will 
serve in a few words to indicate what appears, I think, to be 
the most probable steps by which these singular instincts were 
acquired. 

" I have been thinking about Pompilius and its allies. — 
Please take the trouble to read on perforation of the corolla 
by Bees, p. 425 of my " Cross-fertilization," to end of chapter. 
Bees show so much intelligence in their acts, that it seems not 
improbable to me that the progenitors of Pompilius originally 
stung caterpillars and spiders, &c., in any part of their bodies, 
and then observed by their intelligence that if they stung 
them in one particular place, as between certain segments on 
the lower side, their prey was at once paralyzed. It does not 
seem to me at all incredible that this action should then 
become instinctive, i.e., memory transmitted from one genera- 
tion to another. It does not seem necessary to suppose that 



302 MENTAL EVOLUTION IN ANIMALS. 

when Pompilius stung its prey in the ganglion it intended or 
knew that their prey would keep long alive. The development 
of the larvae may have been subsequently modified in relation 
to their half -dead, instead of wholly dead prey ; supposing 
that the prey was at first quite killed, which would have 
required much stinging. Turn this over in your mind," &c. 

Now in Chapter XIV I have already given a short epitome 
of the facts concerning the boring by humble-bees of holes in 
corollas, and the subsequent utilization of the holes by hive- 
bees. It will be remembered that the connection in which I 
there alluded to the facts was that of the power of imitation 
by one species of the habits of another — the hive-bees observ- 
ing that the humble-bees were saving time by sucking through 
the holes instead of entering the flowers. But the point 
which is of importance in the present connection is the intelli- 
gence displayed by the humble-bees in originating the idea, 
so to speak, of boring the holes. For close observation shows 
that they bore the holes with as precise an appreciation of 
the morphology of the flowers, as is shown by the Sphex of 
the morphology of spiders, insects, or caterpillars. Thus in 
the case of leguminous flowers they bite only through the 
standard petal, and always on the left side just over the 
passage to the nectar, which is larger than the corresponding 
passage on the right side. Therefore, as Mr. Francis Darwin 
observes, "it is difficult to say how the bees could have 
acquired this habit. Whether they discovered the inequality 
in the size of the nectar-holes in sucking the flowers in the 
proper way, and then utilized this knowledge in determining 
where to gnaw the hole ; or whether they found out the best 
situation by biting through the standard at various points, 
and afterwards remembered its situation in visiting other 
flowers. But in either case they show a remarkable power of 
making use of what they have learnt by experience."* 

Seeing, then, that Hymenopterous insects are certainly 
proved by these observations to be capable of marvellously in- 
telligent appreciation of morphological structure, I think with 
Mr. Darwin that these observations are most apposite to the 
case of the Sphex. There is not, after all, so very much more 
of this kind of appreciation required to observe the effects of 
stinging a caterpillar between its segments, than to hit upon 
the idea of going outside a flower and biting a hole on the 
* Nature, Jan. 8, 1874, p. 189, 



FEIGNING DEATH 303 

left side of a particular petal, just over the spot where the 
larger passage to the nectar is to be found. But, as I have 
said, I feel that further observation — especially in the way of 
experiment — of the facts is required before we should be 
justified in giving a very definite opinion upon the theoretical 
interpretation of them. All I can say is that, in the present 
state of our information upon the subject, Mr. Darwin's view, 
as above stated, appears to be the most probable one that 
can be taken. We are not much surprised at the instinct of 
a Ferret in attacking the medulla oblongata of a rabbit, or at 
that of a Pole-cat in paralyzing frogs and toads by injuring 
the cerebral hemispheres ;* and in both these cases — so 
analogous to that which we are now considering — the instinct 
must have originated by intelligent observation of the effects 
of biting these particular parts of the prey. But neither a 
. ferret nor a pole-cat is a particularly intelligent animal, so 
that we are perhaps too ready to feel surprise at the pos- 
sibly similar degree of intelligence displayed by insects 
which belong to the most intelligent group of invertebrated 
animals. 

Feigning Death. 

It is a matter of common knowledge and wonder that 
sundry species of animals belonging to different orders and 
even classes, manifest the instinct, when in danger, of feign- 
ing death. As it is clearly impossible to attribute this fact 
to any idea of death and of its conscious simulation on the 
part of the animals, the subject becomes one of importance 
for us to consider. I shall first give all the facts that I have 
been able to collect with regard to it, and then proceed to 
discuss their explanation. 

The most familiar example of the instinct in question is 
furnished by sundry species of insects and spiders, many of 
which allow themselves to be slowly dismembered, or 
gradually roasted to death, without betraying the slightest 
movement, "Among fish, the captured sturgeon remains 
quiet and passive in the net, while the perch feigns death 
and floats on its back."i- According to Wrangle,;]: the wild 
geese of Siberia, if alarmed during the moulting season when 

* See Animal Intelligence, p. 347. 

+ Coucli, Illustrations of Instinct, p. 199, et seq. 

X Travels in Siberia, p. 312, Eng. Transl, 



304 MENTAL EVOLUTION IN ANIMALS. 

tliey are unable to fly, stretch themselves at length upon the 
ground with their heads concealed, so as to feign death and 
deceive the sportsman. According to Couch, the habit is 
common to the landrail, the skylark, and other birds.* 
Among mammals, the same author says, " The opossum of 
North America is so famous for feigning death, that its name 
has become proverbial as an expression of this deceit ;"* and 
he narrates instances of the same fact with regard to mice, 
squirrels, and weasles. The testimony on the subject with 
regard to wolves and foxes is so abundant that I do not think 
there can be any reasonable question concerning its accuracy. 
Thus Captain Lyon, in the account of his Polar Expeditioii, 
says that a wolf caught in a trap which was set by Mr. Griffiths, 
was apparently killed and then dragged on board. " The eyes, 
however, as it lay on deck, were observed to wink, whenever 
any object was placed near them; some precautions were 
therefore considered necessary ; and the legs being tied, the 
animal was hoisted up with his head downwards. He then, 
to our surprise, made a vigorous spring at those near him ; 
and afterwards repeatedly turned himself upwards, so as to 
reach the rope by which he was suspended, endeavouring to 
gnaw it asunder," &c. 

The testimony is abundant on the subject of foxes 
shamming dead. As Mr. Blyth observes,! " a fox has been 
known to personate a defunct carcase, when surprised in a 
hen-house, and it has even suffered itself to be carried out 
by the brush and thrown out on a dungheap, whereupon it 
instantly rose and took to its heels, to the astounding dismay 
of its human dupe. In like manner this animal has submitted 
to be carried for more than a mile, swinging over the shoulder 
with its head hanging downwards, till at length it has very 
speedily effected its release by biting." 

Similarly Couch, who gives a number of instances of the 
fact, summarizes them thus : — " When suddenly surprised by 
man, he has been known to assume the appearance of being 
dead, and has suffered himself to be handled, and even ill- 
treated, without betraying any signs of sensibility. This high 
degree of simulation and dissimulation has been ascribed to 
consummate wisdom, whicli, when a better means of escape 
did not offer itself, prompted him to the stratagem of feigning 

• Loc. cit. t Loundoun's Mag. Nat. Hist., N.S., vol. i. p. 5. 



FEIGNING DEATH. 305 

to be incapable of defence or flight until he had disarmed 
suspicion, and so escaped hostility.* 

According to Jesse, " Snakes, too, will pretend to be dead, 
and lie motionless, as long as they think they are observed, 
and in danger, but, when they believe that all foes have with- 
drawn, and they are out of peril, they will glide away with 
the greatest speed into the nearest hole or covert. 

" Among birds, the corncrake has been most remarked for 
this species of art. The author of ' The Natural History of 
the Corncrake ' relates that one of these birds was brought to 
a gentleman by his dog, to all appearance quite dead. The 
gentleman turned it over with his foot, as it lay upon the 
ground, and was convinced there was no more life in it. But 
after a while he saw it open one eye ; and he then took it up 
again, w^hen its head fell, its legs hung loose, and it once more 
appeared to be certainly dead. He next put it into his 
pocket, and before long felt it struggling to escape ; he took it 
out, and it seemed lifeless as before. He then laid it on the 
ground and retired to a little distance to watch it, and saw it 
in about five minutes raise its head warily, look round, and 
decamp at full speed." 

Bingley observes, "This stratagem is also said to be prac- 
tised by the common crab, which, when it apprehends danger, 
will lie as if dead, waiting for an opportunity to sink itself 
into the sand, keeping only its eyes above it." 

Hence, it appears that from insects upwards, the instinct 

* Illustrations of Instinct, p. 197. Sir E. Tennent, in liis Ifatural Sis- 
tory of Ceylon, gives tlie case of a wild elephant apparently feigning death ; 
but as under the circumstances mentioned elephants very often actually 
do die (see Animal Intelligence, p. 396), this case is probably not to be attri- 
buted to intentional deception on the part of the animal. The case is as 
follows I — "Mr. Cripps has related to me an instance in which a recently 
captured elephant was either rendered senseless from fear, or, as the native 
attendants &sseTteA., feigned death in order to regain its freedom. It was led 
from the corral as usual between two tame ones, and had already proceeded 
far towards its destination ; when night closing in, and the torches being 
lighted, it refused to go on, and finally sank to the groiond, apparently life- 
less. Mr. Cripps ordered the fastenings to be removed from its legs, and 
when attempts to raise it had failed, so convinced was he that it was dead, 
that he ordered the ropes to be taken off and the carcase abandoned. While 
this was being done he and a gentleman by whom he was accompanied leaned 
against the body to rest. They had scarcely taken their departure and pro- 
ceeded a few yards, when, to their astonishment, the elephant rose with the 
utmost alacrity, and fled towards the jungle, screaming at the top of its voice, 
its cries being audible long after it had disappeared in the shades of the 
forest." • 



306 MENTAL EVOLUTION IN ANIMALS. 

of sliamming dead occurs in most if not all the classes of 
the animal kingdom. The subject therefore demands from 
us serious attention, because on the one hand, as previously 
remarked, it is obvious that the idea of death and of its 
conscious simulation would involve abstraction of a higher 
order than we could readily ascribe to any animal, and on the 
other hand it is not very easy otherwise to explain the 
facts. 

I shall first of all quote what Couch says upon the sub- 
ject, as he is the first author, so far as I am aware, who did 
not at once take it for granted that animals consciously feign 
death, and who also supplied a reasonable hypothesis to 
account for the facts. He says : — 

" But a more probable explanation is, that the suddenness 
of the encounter, at a time when the creature thought of no 
such thing, had the effect of stupefying his senses, so that an 
effort of escape was out of his power, and the appearance of 
death was not the fictitious contrivance of cunning, but the 
consequence of terror. And that this explanation is the true 
one appears, among other proofs, from the conduct of a bolder 
and more ferocious animal, the Wolf, under similar circum- 
stances. If taken in a pitfall it is said that it is so subdued 
by surprise, that a man may safely descend and bind and 
lead it away or knock it on the head ; and it is also said that 
when it has wandered into a country to which it is a stranger, 
it loses much of its courage and may be assailed almost with 
impunity."* 

" A similar action to that of the Fox has been observed 
in a little animal to which it is not common to ascribe more 
than an ordinary degree of cunning or confidence in its own 
resources. In a bookcase of wainscot, impervious to light, 
certain articles were kept more agreeable to the taste of 
mice than books, and, at midday, when the doors were suddenly 
opened, a mouse was seen on one of the shelves ; and so 
rivetted was the little creature to the spot that it showed all 
the signs of death, not even moving a limb when taken into 
the hand. On another occasion, on opening a parlour-door, in 
broad daylight, a mouse was seen fixed and motionless in the 
middle of the room ; and, on advancing towards it, its appear- 
ance in no way differed from that of a dead animal, excepting 
that it had not fallen over on its side. Neither of these 

* Ma(j. Nat. Hist., New Ser., voL ii, p. 121. 



FEIGNING DEATH. 307 

creatures made an effort to escape, and were taken np at 
leisure ; nor had they received any hurt or injury, for they 
soon displayed every mark of being alive and well. 

*' It would be as easy to catch a Weasel asleep as off its 
guard ; but it seems still more unlikely that, in the disguise 
of death it should suffer itself to be cuffed, pawed, and 
handled with impunity by a cat : yet it so happened that, 
while Puss was reclining at ease, seemingly inattentive to all 
the world around her, a Weasel came unexpectedly up, was 
seized in a moment, and dangling from her teeth as if dead, 
was thus carried to the house at no great distance. The door 
being shut, Puss, deceived by its apparent lifelessness, laid 
her victim on the step, while she gave her usual mewing cry 
as for admittance. But by this time the active little creature 
had recovered its recollection, and in a moment struck its 
teeth into its enemy's nose. It is probable that, besides the 
sudden surprise of the capture, the firm grasp which the cat 
had of it round the body had prevented any earlier effort at 
resistance from the Weasel ; for in this manner our smaller 
quadrupeds which bite so fiercely may be held without 
injury ; but the Weasel can hardly be supposed to have been 
practising a deception all the while it was in the Cat's 
mouth."* 

This hypothesis would require to be substantiated by 
special experiments before it would merit unreserved accept- 
ance. These experiments would consist in allowing an animal, 
immediately that it is observed shamming dead, to regain its 
liberty, and to watch it without the animal knowing that it is 
being observed. If it were then to continue for any consider- 
able time motionless, the fact would tend to prove Couch's 
hypothesis, whereas if it were quickly to recover, the inference 
would lie in the direction of supposing the passiveness in the 
presence of danger due to conscious purpose. I once thought 
that I had myself the opportunity of trying this experiment ; 
for having caught a wild squirrel in a cloth I observed that the 
animal immediately became motionless. Turning it out upon 
the ground and concealing myself from its view, I waited a 
long time for it to recover ; but as it did not do so I went up to 
examine it, and found it was not shamming, but really dead. 
This incident I mention here, because it has an important 
bearing on Couch's hypothesis ; it shows that the terror of a 

* JUvstrations of Instinct, p. 125. 



308 MENTAL EVOLUTION IN ANIMALS. 

wild animal on being captured may be sufficient to cause 
actual death, and the researches of Professor Preyer on the 
hypnotism of animals (conducted long after Couch's book was 
published and having no special reference to the present 
question), showed that fright is a strong predisposing cause 
of " Kataplexy," or mesmeric sleep in animals. 

Tliis allusion to Professor Preyer's researches leads me 
next to remark that he ascribes the shamming dead of insects 
to the exclusive influence of kataplexy. Having observed 
the potency of this influence in producing analogous condi- 
tions in the neuro-muscular systems of higher animals — even 
as far down the series as the cray-fish, which were made to 
stand upon their heads while in the hypnotic state — it was 
perfectly logical in him to attribute the shamming dead of 
insects to the same cause. And his reasoning might have 
been greatly strengthened had he been aware of the import- 
ant facts which had been observed by Mr. Darwin, and 
which are now given in the Appendix. These facts, it will 
be noted, are, that there is no species of spider or insect of 
which it can be said that the attitude assumed when sham- 
ming death at all closely resembles the one which the animal 
assumes when really dead ; that in many cases this attitude 
is very dissimilar ; and therefore that all " shamming dead " 
amounts to in these animals is an instinct to remain motion- 
less, and thus inconspicuous, in the presence of enemies. 
And it is easy to see that this instinct may have been de- 
veloped by natural selection without ever having been of an 
intelligent nature — those individuals which were least in- 
clined to run away from enemies being preserved rather 
than those which rendered themselves conspicuous by move- 
ment. 

That is to say, it is easy to see how the instinct may have 
become developed by primary means ; for if it were of more 
advantage to an animal when in danger to become motionless, 
and therefore inconspicuous or unattractive to enemies, than 
it would be to seek safety in flight, of course it is obvious 
that in such cases natural selection would always have 
operated in the direction of producing quiescence, no less 
than in other cases it would have operated in the direction of 
producing activity. Now, I think it is not at all improbable 
that " kataplexy " may have been of miich assistance in 
originating, and possibly also in developing, tliis instinct. 



FEIGNING DEATH. 309 

For if this peculiar physiological condition is apt to occur 
among insects and spiders — as it certainly occurs in an 
animal belonging to the same class, the cray-fish — there 
would be supjjlied to natural selection the material, as it 
were, out of which to form this instinct. And if such were 
the origin of the instinct, we may presume that its develop- 
ment to its present state of perfection would most likely be 
continued along the same lines — natural selection always 
improving the kataplectic susceptibility, so as to make the 
state occur with great suddenness under the influence of a 
certain class of stimuli, and to prevent it from lasting for an 
unnecessary time after such stimuli had ceased to operate. 
Thus we might arrive at the existing state of things, in such 
an animal as a wood-louse or death-watch, which fall into a 
kataplectic state immediately on being alarmed (when, on the 
present hypothesis, they are quite insensitive to pain), but 
quickly recover as soon as the source of alarming stimula- 
tion is removed.* 

We have here, then, a rather interesting speculation of a 
not improbable kind as to the strange, and, so to speak, far-off 
peculiarities of organization on which natural selection may 
seize for the developing of a beneficial instinct. But I desire 
it to be particularly not.3d that I only adduce this specula- 
tion, as it were, parenthetically. I think with Preyer that 
the shamming dead of insects is a phenomenon in which the 
principles of hypnotism are probably concerned. But if so, 
I regard these principles only as furnishing the materials out 
of which natural selection has constructed this particular 
instinct. Therefore, whether or not these principles are really 
concerned in the phenomenon, is only a side question ; the im- 
portant consideration for us is, that the instinct, whether or 
not developed from materials supplied by kataplexy, must 
certainly have been developed by natural selection. Mr. 
Darwin's observations place this conclusion beyond the reach 

* An objection to this view may here be disposed of : Duncan, " On 
Instinct," after observing that spiders while shamming dead, "will suffer 
themselves to be pierced with pins and torn to pieces without discovering the 
smallest signs of terror," adds that if the cause were, as often supposed, " a 
kind of stupor occasioned by terror," the animal ought not so soon to recover 
when the object of terror is removed. But as a matter of fact the " stupor " 
does not pass off immediately upon the cessation of the stimulus ; it lasts as 
long as the kataplectic state does in certain birds, such as the owl when held 
on its back. 

14 



310 MENTAL EVOLUTION IN ANIMALS. 

of doubt, and even if the phenomena of kataplexy were not 
available for natural selection to seize upon for the purpose 
in question, there can be no doubt that other materials 
might have been so ; for, a priori, there seems to be at least 
not more difficulty in developing an iustinct to remain 
motionless under certain circumstances, than in developing 
one to run away ; and as a matter of fact, all animals which 
are protectively coloured have, either as cause or consequence, 
developed their instincts in the former direction. Therefore 
we must suppose that an animal which was not sufficiently 
locomotive to find safety in flight, would be most closely 
attended to by natural selection in the direction of encourag- 
ing quiescence — and this whether or not natural selection 
were provided with kataplectic susceptibilities on which to 
operate ; kataplexy alone could not form the instinct. 

So far, then, the subject is sufficiently clear. But now, 
we have obviously some important distinctions to draw. For 
the shamming dead of a highly intelligent animal like a fox 
is a widely different matter, psychologically considered, from 
the shamming dead of insects ; so that an explanation which 
might be held fully adequate to account for the latter might 
not be so to account for the former. Thus while I have no 
hesitation in regarding the fact in insects as due to a non- 
intelligent instinct developed by natural selection in the way 
just explained, I cannot see how this could well be the case 
in vertebrated animals. A fox would never have so good a 
chance of escape from an enemy by remaining motionless as 
it would by the use of its legs, which it requires a fox-hound 
to overtake. Moreover the shamming dead is here far from 
invariable, and so is not, as in the case of insects, instinctive. 
Therefore, although I did not fully agree with Preyer in 
assigning the universal (instinctive) quiescence of certain 
insects when alarmed to the unassisted influence of kata- 
plexy, I think that the occasional (accidental) display of 
quiescence by wild vertebrated animals under similar circum- 
stances tends much more unequivocally in favour of his view. 
Tor here the action is not universal, or even usual ; and when 
it does take place it must, as a rule, be rather detrimental to 
the animal than otherwise — seeing that the whole economy of 
the animal is here adapted to rapid movement. Therefore 1 
think that in the case of Birds and Mammals the hypothesis 
of Couch already quoted is the most reasonable — especially 



FEIGNING DEATH. 311 

if we supplement it with our knowledge concerning the 
recently discovered facts of kataplexy.* 

On the other hand, not to shirk a difficulty, I have some re- 
markable evidence which tends to show that certain monkeys 
sham dead with the deliberate purpose, not of escaping from 
enemies, but of deceiving intended victims. Here, of course 
there can be no terror and no kataplexy, so that if we accept 
the evidence of the fact we must seek for some other expla- 
nation. 

Thompson gives in his " Passions of Animals " (pp. 455- 
7), the case of a captive monkey which was tied to a long 
upright pole of bamboo in the jungles of Tillicherry. The 
ring at the end of its chain fitting loosely to the slippery 
pole, the animal was able to ascend and descend the latter at 
pleasure. He was in the habit of sitting on the top of the 
pole, and the crows taking advantage of his elevated position, 
used to steal his food which was placed every morning and 
evening at the foot of the pole. " To this he had vainly 
expressed his dislike by chattering, and other indications of 
his displeasure equally ineffectual ; but they continued their 
periodical depredations. Finding that he was perfectly un- 
heeded, he adopted a plan of retribution as effectual as it was 
ingenious. One morning when his tormenters had been par- 
ticularly troublesome, he appeared as if seriously indisposed ; 
he closed his eyes, dropped his head and exhibited various 
other symptoms of severe suffering. No sooner were his 
ordinary rations placed at the foot of the bamboo, than the 
crows watching their opportunity, descended in great num- 
bers, and according to their usual custom, began to demolish 
his provisions. The monkey began now to descend the j^ole 
by slow degrees as if the effort were painful to him, and as if 
so overcome by indisposition that his remaining strength was 
scarcely equal to such an exertion. Wlien he reached the 
ground he rolled about for some time, seeming in great agony, 
until he found himself close to the vessel employed to con- 
tain his food which the crows had by this time well nigh 
devoured. There was still, however, some remaining, which 
a solitary bird, emboldened by the apparent indisposition of 
the monkey, advanced to seize. The wily creature was at 
this time lying in a state of apparent insensibility at the 

* The mnking of the wolf's eye, mentioned hj Captaia Lyon, would be 
quite compatible with a certain phase of the hypnotic state. ■ 



312 MENTAL EVOLUTION IN ANIMALS. 

foot of the pole and close by the pan. The moment the crow 
stretched out his head, and ere it could secure a mouthful of 
the interdicted food, the watchful avenger seized the depre- 
dator by the neck with the rapidity of thought and secured it 
from doing further mischief. He now began to chatter and 
grin with every expression of gTatified triumph, while the 
crows Hew round, cawing, as if deprecating the chastisement 
about to be inflicted on their captive companion. The 
monkey continued for a while to chatter and grin in triumph ; 
he then deliberately placed the crow between his knees and 
began to pluck it with the most humorous gravity. When 
he had completely stripped it, except of the large feathers in 
the pinions and tail, he flung it into the air as high as his 
strength would permit, and after flapping its wings for a few 
seconds, it fell to the ground with a stunning shock. The 
other crows, which had been fortunate enough to escape a 
similar castigation, now surrounded it and immediately pecked 
it to death. The animal then ascended its pole, and the next 
time his food was brought, not a single crow approached it." 

I have quoted this case although it sounds well nigh in- 
credible, not merely because Thompson is a good authority, 
but because in all its essential details it has been uncon- 
sciously corroborated by the observations of a friend of my 
own, viz., the late Dr. W. Bryden, C.B. This gentleman, 
without beinsf cognizant of the above anecdote, told me that 
he had himself repeatedly witnessed a tame monkey (I forget 
the species) in India lying on its back perfectly motionless 
for long periods of time, till the crows in the neighbourhood, 
supposing him to be dead, approached within grasping dis- 
tance, when he used to make a sudden spring at one of them, 
and proceed slowly to pluck it alive, apparently for the mere 
love of gratifying his passion of cruelty — although, however, 
he used to suck the juicy ends of the larger feathers. As I can 
quite rely on Dr. Bryden's veracity and cannot imagine how 
in such a case there can have been any room for malobserva- 
tion, I am inclined to lend a credence to the above anecdote 
which I should otherwise have regarded with distrust. 

Now if, as I can scarcely doubt from Dr. Bryden's account, 
some monkeys display the remarkable trick of really and of 
set purpose shamming death, the only possible explanation of 
the fact is that, having observed crows to congregate round 
motionless carcasses, they infer that by remaining motion- 



FEIGNING DEATH. 31 o 

less they may induce these animals to come within grasping 
distance. No doubt this displays an astonishing amount of 
deliberative inference ; but it is to be observed that the fact, 
if it is a fact, does not imply any abstract idea of death ; it 
implies only the idea of imitating a previously observed 
quiescence with the purpose of bringing about the same 
result — approach of birds — which that quiescence had pre- 
viously been observed to produce. Seeing that monkeys are 
higlily imitative as well as highly observant animals, this 
interpretation is not so antecedently incredible as at first 
sight it no doubt appears. 

But now it follows that if monkeys are able consciously 
and with deliberate intent to remain motionless for the purpose 
of gaining a particular object, other and almost as intelligent 
animals may do the same. Thus, notwithstanding the proba- 
bility previously pointed out that the shamming dead of 
w^olves and foxes may be due to kataplexy, there here arises 
a possibility of its being due to intelligent purpose. As 
bearing on this possibility, I will quote two cases which 
appear to have been sufficiently well observed. 

The first is one which has been recently published by 
Brigade Surgeon G. Bidie in " Nature " (vol. xviii, p. 244). 
He says : — 

" Some years ago, while living in "Western Mysore, I 
occupied a house surrounded by several acres of fine pasture 
land. The superior grass in this preserve was a great tempta- 
tion to tlie village cattle, and whenever the gates were open 
trespass was common. My servants did their best to drive 
off intruders, but one day they came to me rather troubled, 
stating that a Brahmin-bull which they had beaten had 
fallen down dead. It may be remarked that these bulls are 
sacred and privileged animals — being allowed to roam at 
large and eat whatever they may fancy in the open shops of 
the bazaar-men. On hearing that the trespasser was dead, I 
immediately went to view the body, and there sure enough it 
was lying exactly as if life were extinct. Being rather vexed 
about the occurrence in case of getting into trouble with the 
natives, I did not stay to make any minute examination, but 
at once returned to the house with the view of reporting the 
affair to the district authorities. I had only just gone for a 
short time when a man, with joy in his face, came running 
to tell me that the bull was on his legs again and quietly 



314 MENTAL EVOLUTION IN ANIMALS. 

grazing. Suffice it to say that the brute had acquired the 
trick of feigning death which practically rendered its expul- 
sion impossible, when it found itself in a desirable situation 
which it did not wish to quit. The ruse was practised fre- 
quently with the object of enjoying my excellent grass, and 
although for a time amusing, it at length became troublesome, 
and resolving to get rid of it the sooner, I one day, when he 
had fallen down, sent to the kitchen for a supply of hot 
cinders, which we placed on his rump. At first he did not 
seem to mind this much, but as the application waxed hot, 
he gradually raised his head, took a steady look at the site 
of the cinders, and finally getting on his legs went off at a 
racing pace and cleared the fence like a deer. This was the 
last occasion on which we w^ere favoured with a visit from 
our friend." 

Now here we have a case of apparent simulation of death 
frequently repeated with an intelligent purpose, and as the 
narrator is a medical man, we must suppose that the simula- 
tion was well done. Nevertheless, the idea which the 
animal had may only have been that of remaining inert, and 
trusting to his weight in preventing his removal. The case, 
however, is unquestionably a remarkable one, and the inter- 
pretation which I have suggested becomes perhaps less pro- 
bable in view of the other case to which I have alluded, and 
which I shall now proceed to give. This case is published in 
the late Mr. Morgan's book on the Beaver (p. 269), and he 
says it " was communicated to the author by Mr. Coral C. 
White of Aurora, New York, who carried out the fox. His 
veracity is unimpeachable." 

" A fox one night entered the hen-house of a farmer, and 
after destroying a large number of fowls, gorged himself to 
such repletion that he could not pass out through the small 
aperture by which he had entered. The proprietor found 
him in the morning sprawled out upon the floor, apparently 
dead from surfeit ; and taking him up by the legs carried him 
out unsuspectingly, and for some distance to the side of his 
house, where he dropped him upon the grass. No sooner did 
lieynard find himself free than he sprang to his feet and 
made his escape. He seemed to know that it was only as a 
dead fox that he would be allowed to leave the scene of his 
spoliations ; and yet to devise this plan of escape required 
no ordinary effort of intelligence," &c. 



FEIGNING DEATH. 315 

If the facts are here correctly i-ecorded (and in all the 
points upon which I am about to dwell they agree closely 
with some of the cases given by Couch), one would scarcely 
suppose that the mere approach of a man in opening the 
door of the hen-house could have caused either the kind or 
degree of alarm which is known to produce kataplexy ; while 
it is somewhat doubtful whether the stimulus occasioned by 
dropping the fox upon the grass would have been sufficient 
suddenly to dispel the kataplectic state. Therefore, in such a 
case as this it seems to me that the probability rather inclines 
to the shamming dead having been due to an intelligent pur- 
pose, even although we may not suppose the animal to have 
had any idea either of death as such, or of its conscious 
simulation. Thus the case with respect to the higher animals 
— if we have due regard to all the evidence which has now 
been presented — seems to me one of no small difficulty. The 
truth simply is that there is a lack of sufficient observation, 
by experimental means, to determine whether wolves, and 
more especially foxes, simulate death — i.e., remain motion- 
less in certain circumstances of danger with the conscious 
purpose of furthering their escape; or, perhaps almost as 
probably, whether the motionless condition of these animals 
under such circumstances is due to the occurrence of the 
hypnotic state. With regard to these animals, therefore, as 
with regard to the Brahmin-bull, I have thought it best not 
to express a definite opinion either way ; but rather to pre- 
sent all the evidence on both sides with the view of stimu- 
lating experimental enquiry of the kind that I have sug- 
gested by any one who may have the opportunity of con- 
ducting it.* Such an enquiry having been conducted by 
Mr. Darwin in the case of insects and spiders has closed the 
question as far as they are concerned, by leaving no room to 
suppose that their behaviour is due to conscious purpose. 
The evidence with regard to the higher Mammalia, on the 
other hand, points to a different conclusion, for the full 
establishment of which further and corroborative evidence is 
doubtless necessary. 

Be it observed, however, that in these cases the difficulty 

* If Mr. C C White, after having read the above and so having under- 
stood the nature of the question, had laid down his fox upon the grass with 
extreme gentleness, and immediately concealed himself, he might greatly have 
furthered the solution of the question. 



316 MENTAL EVOLUTION IN ANIMALS. 

has no reference to any question of instinct — for, unlike the 
case of insects, the habit is much too exceptional to be 
regarded as instinctive — but to determining whether the 
facts are due to intelligent purpose or to some purely physio- 
logical effects of fear. In the more remarkable of the above- 
quoted cases, no doubt, the latter hypothesis is not available; 
but it may be so in some of the others, and even where this 
hypothesis is not available, it becomes most desirable to 
understand the class of ideas which induce the animal to 
behave in a manner so closely simulating death. Here, how- 
ever, I am only concerned with showing that the difficulty of 
arriving at such an understanding has nothing to do with the 
present theory as to the formation of instinct. 

Feigning Injury. 

In the " Contemporary Eeview " (July 1875) the Duke 
of Argyll, in an article on " Animal Instinct," argues that the 
female duck could hardly have consciously learnt to imitate 
the movements of a wounded bird ; and that the young merg- 
ansers, which squat on the mud when alarmed and are thus 
made inconspicuous while the old ones fly away, are in the 
same case. Mr. Darwin, in some MS notes on this article, 
observes that he agrees with the Duke in not ascribing the 
deceptive movements of the female duck, &c., to conscious 
imitation of wounded birds ; but thinks that a female bird 
which, from solicitude for her nestlings, would endeavour to 
fight a threatening quadruped as a hen does a dog, might, 
by alternately attacking and retreating, inadvertently draw 
the enemy away from the nest. Natural selection, acting on 
this primitive habit, might then develop the running away 
from the nest as an instinct ; and if, as is probable, carni- 
vorous quadrupeds would be more likely to follow birds 
apparently unable to fly than birds apparently well, the 
action of drooping the wing, &c., might have been slowly 
developed. 

The instinct of squatting shown by young birds, which 
are thus rendered inconspicuous, was no doubt acquired in 
the same way and for the same reason as the instinct of 
shamming dead in insects. The instinct, however, in the 
case of young birds may have originally been acquired by 
older animals (due in the first instance to being partly 



FEIGNING INJURY. 317 

paralyzed by fright), and then, in accordance with the general 
principles of heredity, being inherited at an earlier age by the 
progeny. 

It will thus be seen that Mr. Darwin was disposed to 
attribute the instinct, both of the mother and young, to an 
exclusively primary origin ; but I confess that the case does 
appear to my mind one of difficulty, and I am rather inclined 
to think that the instinct of the mother in the case of the 
duck, peeweet, partridge, and all birds which present it, 
must have originally been assisted by intelligence. It 
must be admitted, from what we know of hens, that the 
maternal feelings may be so strong as to lead to a readi- 
ness to incur danger or death rather than that the brood 
should do so. Therefore, when in the presence of a four- 
footed enemy the mother bird begins alternately attack- 
ing and retreating in the manner alluded to by Mr. Darwin, 
if she were intelligent enough to observe that on retreating 
without taking wing she was followed up, there can be no 
doubt that she might with intentional purpose thus lure 
away the enemy from her young. If so, those parents which 
had sense enough to adopt this device would no doubt be 
able to rear a greater number of broods than could the less 
observant parents ; and the young broods of such intelligent 
parents would inherit a tendency to adopt this device when 
they themselves became mothers. Thus the originally intel- 
ligent device would slowly become organized into an instinct, 
and so be now performed with mechanical promptitude by 
every individual partridge, plover, and duck. The greatest 
difficulty is to account for the drooping of the wing, and this, 
I think, can only be done by regarding it, with Mr. Darwin, 
as of an unblended primary origin. The case, however, is 
unquestionably very remarkable. 

Such are the only instincts which have occurred to me as 
likely to present any special difficulty to the foregoing theory 
of the origin and development of instincts in general. Mr. 
Darwin in his chapter on Instinct in the " Origin of Species," 
has fully discussed several other instincts in this connection 
(viz., the parasitic instinct of the cuckoo, the cell-making 
instinct of bees, and the slave-making instinct of ants) ; but 
as these do not present any real difficulty, I shall not wait 
to go over the ground already so thoroughly traversed by 
him. 



318 MENTAL EVOLUTION IN ANIMALS. 



CHAPTEE XIX. 

PtEASON. 

I SHALL begin this chapter by quoting from " Animal Intel- 
ligence " my definition of the word " Eeason," in order that 
my use of the word may be clearly understood. 

" Eeason is the faculty which is concerned in the inten- 
tional adaptation 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 
circumstances 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 relations. 
This latter is the only use of the word that is strictly legiti- 
mate, and it is thus that I shall use it throughout the present 
treatise. This faculty, however, of balancing relations, draw- 
ing inferences, and so of forecasting probabilities, admits of 
numberless degrees." 

The object of the present chapter will be that of tracing 
the probable genesis of this faculty, and, in order to give 
clearness to the discussion, I desire it to be remembered that 
I reserve the terms Eeason and Eatiocination to designate 
the faculty above defined. I shall use the term Inference to 
designate the less highly developed mental antecedents out 
of which, as I shall show, I conceive Eeason to have been 
evolved. No doubt every act of reason is also an act of in- 
ference, but we shall find that it is absolutely necessary to 
have some word to signify indifferently the lowest and the 
highest stages of that whole class of mental processes which 
culminates in symbolic calculation. The word Inference is 



EEASON. '319 

the best that I can find, and therefore it will be understood 
that in my usage, while all acts of reason are likewise acts of 
inference, all acts of inference need not be acts of reason. 

Thus much as to terminology being premised, I may pass 
to the subject of the present chapter. I have already, in 
earlier chapters, endeavoured to show how it is probable that 
consciousness arises out of reflex action (or that the mind- 
element becomes attached to nervous processes of adjustment), 
when the latter arrives at such a degree of complexity, or has 
reference to external circumstances having such a degree of 
inconstancy, that the nerve-centre becomes a seat of com- 
parative turmoil among molecular forces. Whenever this 
stage is reached, and a nerve-centre begins to become con- 
scious of its own working, we pass, according to my classifi- 
cation, from the domain of reflex action into that of instinct 
■ — instinct being, in my terminology, reflex action into which 
there is imported the element of consciousness. But now, as 
during the course of evolution the lower forms of life are 
required progressively to adjust their actions to circum- 
stances of growing complexity and inconstancy, or to occasions 
of growing infrequency, it follows that the organized instincts 
with which they are endowed must at some point begin to 
become inadequate; a greater flexibility in the power of 
adjustive response is needed, and if any such flexibility is 
possible under the conditions of ganglionic action, those 
individuals which best attain to it will survive, and so the 
improvement will become general to the species. Now we 
know that such an increase of flexibility is possible under 
the conditions of ganglionic action, and this increase of 
flexibility on its subjective side we know as the faculty of 
reason. It is here needful to consider in what this faculty 
consists. 

Wliile treating of the genesis of Perception I pointed out 
that the faculty admits of numberless degrees of elaboration. 
These we found to depend largely, or even chiefly, upon the 
degree of complexity presented by the objects or relations 
perceived. Now when a perception reaches a certain degree 
of elaboration, so that it is able to take cognizance of the 
relation between relations, it begins to pass into reason, or 
ratiocination. Contrariwise, in its highest stages of develop- 
ment, ratiocination is merely a highly complex process of 
perception — i.e., a perception of the equivalency of perceived 



320 ■ MENTAL EVOLUTION IN ANIMALS. 

ratios, which are themselves more or less elaborated percepts 
formed out of simpler percepts, or percepts lying nearer to the 
immediate data of sensation. Thus, universally ratiocination 
may be considered as the higher development of perception ; 
for at no point can we draw the line and say that the two are 
distinct. In other words, a perception is always in its essen- 
tial nature what logicians term a conclusion, whether it has 
reference to the simplest memory of a past sensation or to the 
highest product of abstract thought. For when the highest 
product of abstract thought is analyzed, the ultimate elements 
must always be found to consist in material given directly by 
the senses ; and every stage in the symbolic construction of 
ideas in which the process of abstraction consists, depends 
upon acts of perception taking place in the lower stages. 
True it is that these acts of perception here have reference to 
the symbols of ideas, which may themselves be far removed 
from the simple and immediate memories of past sensations ; 
but as we can nowhere draw the line between perception of 
the one order and perception of the other, we ought to recog- 
nize that in the case of this faculty there is nowhere any 
difference in kind, although everywhere a difference in degree : 
or, otherwise stated, intellectual processes which culminate in 
symbolic reasoning are everywhere processes of cognition, 
and of these processes the term perception is a generic name. 

But having thus shown that in my opinion there is no 
real break between cognition of the lowest and of the highest 
order, I must next show at what places I think it is conve- 
nient, for the sake of historical description, to mark off what 
I may term conventioual stages in the development of cog- 
nition. This I have already done for the lower stages of such 
development in my chapter on Perception, where it was 
shown that the first stage consists in merely perceiving an 
external object as an external object, the next stage in recog- 
nizing the simplest qualities of an object, the third stage in 
mentally grouping objects with reference to their perceived 
qualities or relations, and the fourth stage in inferring un- 
perceived qualities or relations from perceived ones — as when 
on hearing a growl I immediately inter the presence of a 
dangerous dog. 

Now from this it is apparent that the process of Inference, 
with which we are in this chapter concerned, is never in its 
earlier or least developed, stages a process of conscious com- 



EEASON. 321 

parisoii. The inference is formed out of the perception, as it 
were, immediately, and does not require to pass through any- 
such process of reflection as the term ratiocination is apt, and 
indeed ought, to imply ; the ratios at this stage are perceived, 
compared, and the inference from them drawn, without the 
need of deliberate thought. For instance, I am hurrying to 
catch a train, and meet a man in the street hurrying in the 
opposite direction ; we both begin rapidly to dance from side 
to side in our endeavour to pass one another, and each time 
we do so it is evident that we have each inferred that the 
other will pass on the opposite side : yet these successive acts 
of inference are made with such rapidity, that not only has 
there been no deliberate thought in the matter, but it is only 
by such thought that I can afterwards find that I must have 
performed so many separate acts of inference. 

Clearly, then, it is in these lower stages of perception 
that we have to look for the first germ of reason : for this 
purpose, let us first interrogate our own perceptions. The 
large measure in which inference enters into the very struc- 
ture even of our most habitual perceptions is easily shown. 
Sir David Brewster has noticed the fact, which must have 
been observed by every one, that when looking through a 
window on the pane of which there is a fly or a gnat, if the 
eyes are adjusted for a greater distance, so that the gnat is 
not clearly focussed, the mind at once infers that it is a bird, 
or some other much larger object seen at a greater distance.* 
Now this shows that in the case of all our visual perceptions 
mental inference is perpetually at work, compensating for the 
effects of distance in diminishing apparent size. No less 
constant must be the work of mental inference in compen- 
sating for the effects of the " blind spot " upon the retina. 
For if the vision be directed to a coloured surface, the part of 
the surface which, on account of the blind spot, is not really 
seen, yet appears to be seen ; and not only so, but it appears 
to be coloured the same tint as the rest of the surface, what- 
ever this may happen to be : unconscious inference supplies 
the colour. Mr. Sully has devoted a large part of his work 
on " Illusions" to a survey and classification of " The Illusions 
of Perception ;" and in most of the instances which he gives 
it is apparent, as he observes, that the illusion arises through 
the mental " application of a rule, valid for the majority of 

* Letters on Natural Magic, VII. 



322 MENTAL EVOLUTION IN ANIMALS. 

cases, to an exceptional case" — i.e., the illusion arises from an 
erroneous inference. It therefore seems needless for me to 
occupy space with an enumeration of instances. 

The first or earliest stage of inference, then, is that in 
which the inference arises in or together with the perception, 
as when we infer that a gnat is a bird, or that the portion of 
a surface corresponding to the blind spot of the retina is 
coloured like the surrounding portions of the surfa.ce ; infe- 
rence may here be said to be a constituent part of perception.* 
In other words, we do not in such cases really sensate all that 
we perceive, and the residue of the perception is supplied by 
inference which is unconscious only because it is so instan- 
taneous. The reason why in such cases it is so instantaneous, 
is because the part furnished by inference has been so 
habitually associated with the part furnished by sensation, 
that the instant the sensation is perceived the mental addition 
is supplied. That this is the true explanation of the matter 
is rendered evident, not only from the deductive considera- 
tions just stated, but also from the inductive verification 
which they receive from the facts that arise when a man who 
has been born blind is suddenly made to see. A good case of 
this kind is the celebrated one of the youth (about twelve years 
of age) whom Mr. Cheselden couched for removing congenital 
cataracts from both eyes. I shall therefore quote a few pas- 
sages from Mr. Cheselden's account of the case. 

" When he first saw he was so far from making any judg- 
ment about distances, that he thought all objects whatever 
touched his eyes (as he expressed) as what he felt touched 
his skin, and thought no objects so agreeable as those which 
were smooth and regular, though he could form no judgment 
of their shape, or guess what it was in any object that was 
pleasing to him. He knew not the shape of anything, nor 
any one tiling from another, however different in shape and 
magnitude ; but upon being told what things were, whose 
form he before knew from feeling, he would carefully observe, 
that he might know them again; but having too many 
objects to learn at once, he forgot many of them ; and (as he 
said) at first learnt to know, and again forgot a thousand 
things in a day. One particular only (though it may appear 
trifling) I will relate. Having often forgotten which was the 

* Just in the same way aa wo found perception to form an integral patfc 
of Memory and of the Association of Ideas. 



EEASON. 323 

cat and which was the dog, he was ashamed to ask; but 
catching the cat (whicli he knew by feeling) he was observed 
to look at her steadfastly, and then setting her down said, 
* So 'puss ! I shall know you another time.' . . . We thought 
he soon knew what pictures were which were showed to him, 
but we found afterwards we were mistaken ; for about two 
months after he was couched, he discovered at once they 
represented solid bodies, when to that time he considered 
them as only party-coloured planes, or surfaces diversified 
with variety of paints ; but even then he was no less sur- 
prised, expecting the pictures would feel like the things they 
represented ; and was amazed when he found those parts, 
which by their light and shadow appeared round and uneven, 
felt only flat like the rest ; and asked which was the lying 
sense, feeling or seeing." 

Dr. W. B. Carpenter gives a somewhat similar case which 
fell within his own observation;* but taking the above as 
sufficient for our purposes, it is evident that the youtli, upon 
being first able to see, was not able to supply any of those 
mental inferences from his visual perceptions which alone 
could make these sensations of any practical use as guides or 
stimuli to action : that is to say, in the absence of these 
inferences, these perceptions were imperfect. But he imme- 
diately set about establishing consciously, or with deliberate 
intention, those numberless associations between sight and 
touch which are usually acquired in early infancy, and which 
are required to constitute the data of the mental inferences 
which we are considering. The number of such special asso- 
ciations required being so great and varied, we may wonder 
that even within the space of three months he should have 
been able to have made so much progress as to feel his visual 
perception deceived by the arts of shading and perspective ; 
but on this point I shall have more to say presently. Mean- 
while it is enough to remember that the case proves tha 
utility of all our visual perceptions to depend upon the ingre- 
dient of mental inference which is supplied by habitual 
association ; and, of course, we cannot doubt that the same is 
true of perceptions yielded by the other senses.f 

* Human Physiology, 1th. ed., p. 103, and in more detail, Contemp. Sev., 
Tol. xxi, pp. 781 -2. 

t As Adam Smith observes, in his comments upon tliis case, " Wlien tlie 
young gentleman said that objects which he saw touched his eyes, he cer- 



324 MENTAL EVOLUTION IN ANIMALS. 

Such, then, I conceive to be the first or most rudimentary 
stage of inference, where, in virtue of constant association, 
the act is organically bound up with a sensuoiis perception, 
so as in fact to constitute an integral part of such perception, 
and therefore to be precluded from ever emerging into con- 
sciousness as a separate act of mind. The next stage in the 
process of inference I take to be the one which Mr. Spencer 
regards as the earliest stage. This, in his words, is "that 
reasoning through which the great mass of surrounding co- 
existences and sequences are known."* That is to say, when 
habitually co-existing groups of external objects, attributes, 
and relations recognized become too numerous and too com- 
plex to be all recognized simultaneously, or when the first in 
a series of habitually successive groups occurs, the unper- 
ceived objects, attributes, or relations are inferred. For 
instance, if a sportsman while shooting woodcock in cover 
sees a bird about the size and colour of a woodcock get up 
and fly through the foliage, not having time to see more than 
that it is a bird of such a size and colour, he immediately 
supplies by inference the other qualities of a woodcock, and 
is afterwards disgusted to find that he has shot a thrush. I 
have done so myself, and could hardly believe that the thrush 
was the bird I had fired at, so complete was my mental sup- 
plement to my visual perception. And, without waiting to 
give illustrations, it is evident that the same principles apply 
to the case of habitual sequences. 

The second stage of inference, then, is reached when, 
owing to a constant association of objects, qualities, or rela- 
tions in the environment, a correspondingly constant associa- 
tion of ideas is produced in the mind, such that when some 
members of the external group are perceived, the other 
members of it are inferred. Inference at this stage resembles 
inference at the earlier stage which we have considered in 
one respect, and differs from it in another. The resemblance 
consists in the act of inference being too rajDid to admit of its 

iainly could not mean that they pressed upon or resisted his eyes .... 
He could mean no more tlian tliat they were close ujjon his eyes, or to speak 
more properly, perhaps, that tlicy were in his eyes. A deaf man, who was 
made all at once to hear, might in the same manner naturally enough say, 
that the sounds which he heard touched his ears, meaning that he felt them 
as close upon his ears, or, to speak perhaps more properly, as in his ear3." 
{Eisai/ on External Senses.) 

* Principles of Psijchologx/, vol. i, p. 458. 



REASON. 325 

"being consciously recognized as an act of mind separate or 
distinct from the perception. The difference consists in sub- 
sequent reflection being able to show that the act of inference 
was distinct from the act of perception, and must have been 
separated from it by a short interval of time ; the inference 
did not, as in the previous cases, constitute an integral part 
of the perception. 

The next stage which we are able to distinguish in the 
faculty of inference is, I think, that of the conscious com- 
parison of objects, qualities, or relations. Here we arrive at 
ratiocination strictly so called ; but still not necessarily at 
self-conscious thought. At this stage we make what Mr. 
Mivart calls " practical inferences ;" that is to say, we com- 
pare one group of ratios with another, but without thinking 
of them as ratios. Thus, for instance, if I meet a cut-throat 
looking man upon a lonely road in Ireland, I may begin con- 
sciously to determine the probabilities whether he is one of a 
" brotherhood," and if so whether he is waiting for me ; hut 
I cast the matter over in my mind while we are approaching 
one another, without waiting to think about my thoughts. If 
I do wait to think aboiit them, I know that I have been 
carrying on a process of reasoning ; but I have equally carried 
on that process whether or not I ever think about it after- 
wards as a process. 

The last or highest stage of reasoning is attained when 
the process admits of being consciously recognized as a pro- 
cess, or itself becomes an object of knowledge. This is the 
stage at which it first becomes possible intentionally to 
abstract qualities or relations for the purposes of inference. 
Here, therefore, it first becomes possible to use symbols of 
ideas instead of the actual ideas themselves, and so it is here 
that the " Logic of Signs " first emerges from the " Logic of 
Feelings." In my next work I shall have a great deal to say 
touching this final stage ; but as it only occurs in Man, I have 
nothing more to say about it at present. 

Turning now to animals, it is evident that they must 
present the first, or, as we may call it, the perceptive stage of 
inference ; for otherwise their whole mechanism of perception 
would need to be supposed different from our own. But there 
is only one respect in which this mechanism can be shown 
to be different, and this consists in the fact already mentioned 
in former chapters — viz., that newly-hatched birds and 



326 MENTAL EVOLUTION OF ANIMALS. 

newly-born mammals are able, without such individual ex- 
perience as is required in the case of man, immediately and 
correctly to supply all the mental inferences which are 
needed to complete their sensuous perceptions. Of course 
the explanation of this must be that heredity in these cases 
has already done the work, so that the young animal comes 
into the world with its mental endowments of perceptive 
inference as fully elaborated and as completely efficient as its 
bodily endowments of perceptive sensations. But the ques- 
tion arises, Why is not this also the case with Man ? That 
it is not the case is sufficiently proved by the results of 
couching for cataract previously quoted ; but why it should 
not be the case is not quite so clear, and hitherto has not been 
sufficiently considered ; for it is only since the experiments of 
Mr. Spalding that the facts with regard to animals have 
become known.* I think the answer to this question is 
as follows. 

First of all, there is no evidence to show that even in the 
case of man heredity has not played a very important part 
(though not so important as with animals) in supplying the 
machinery of perceptive inference. Indeed I think we have 
some evidence to show that it has ; for only by supposing 
this are we able to explain why the youth whose case was so 
well described by Mr. Cheselden was able, after so short an 
interval as three months, to perceive the illusory effects of 
shading and perspective in a picture. But, even if it be 
allowed that heredity here played an important part, there is 
still, no doubt, a great discrepancy to be explained in the 
degree of its influence as compared with its absolute per- 
fection in the case of the lower animals. But I think 
there are two considerations which, taken together, are suffi- 
cient to explain the discrepancy. In the first place we have 
already seen, when treating of the hereditary instinctive 
endowments of animals, that the machinery of these endow- 
ments is apt to be thrown out of gear if they are not allowed 
full play at the time of life when they ought normally to 
have firsc come into operation. Therefore in the case of this 
youth it seems highly probable that during the twelve years 

* Or ratlier, I should say, so well known. Houzeau had pointed out 
that while young infants are unable to localize a pain or other sensation, 
newly-born calves are able to do so with precision (see Fac. Mem. des 
Animaitx, torn, i, p. 52). 



REASON. 327 

of liis congenital blindness, whatever hereditary endowments 
he may have had in the way of forming perceptive inferences 
relating to sight, were largely aborted by disuse, if not also 
thrown out of gear. The other consideration is that, during 
these twelve years his faculties of perceptive inference were 
not lying idle, but were thrown with all the greater strength 
into his perceptions arising from touch and hearing. It is 
therefore abundantly probable that, even upon this lowest 
plane of inference, the strong organization which had been 
formed between this faculty and the perceptions of touch 
and hearing, made it all the more difficult for this faculty to 
form a new organization with the perceptions of sight. 
Further than this, I think it is not improbable that the 
human mind, in being so habitually concerned with processes 
of inference on higher planes, would not be so ready to build 
up by unconscious association a mechanism of perceptive or 
automatic inference, as would the less highly elaborated mind 
of an animal similarly situated. Still, notwithstanding these 
considerations, I feel that it would be well worth while to try 
the experiment of keeping an animal blindfolded from the 
time of its birth till it is a year or two old, and then to see, 
when the blindfolding was removed, whether or not its facul- 
ties of perceptive inference resemble those of a similar 
animal soon after its birth. 

That inference of what I have called the second stage also 
occurs in animals no one will dispute, although, of course, 
some psychologists may object to my calling this particular 
case of the association of ideas by the name of inference. I 
have already said in the chapter which deals with Memory 
and the Association of Ideas, that it is impossible to say 
which are really the lowest animals that possess these 
faculties ; and therefore it is still more impossible to say 
where in the animal kingdom inference of the first or of the 
second stage begins : we can only say that wherever there is 
visual or other sensuous perception which, as a perception, 
requires to form an estimate of distance or other simple rela- 
tion not immediately given by sensation, but mentally 
deduced from sensation — there we must suppose that in- 
ference of the first stage obtains ; and that wherever there is 
an association of ideas, such that the occurrence of one 
perception arouses an inferred knowledge of a complement of 
that perception, or an inferred anticipation of a future event 



328 MENTAL EVOLUTION OF ANIMALS. 

— there we must suppose that inference of the second stage 
obtains. And, although we are not able to draw the lines 
with precision, we know that both these conditions occur low 
down among the Invertebrata. 

The next stage of inference is the highest that obtains 
among animals. This is the stage in which objects, qualities, 
and relations are deliberately compared with the intention of 
perceiving likenesses and unlikenesses (analogies) ; the action 
which follows is therefore undertaken with a knowledge, or 
perception, of the relation between the means employed and 
the ends attained. This, as I have before said, is the stage of 
the process of inference at which the term Eeason or Eatio- 
cination first becomes appropriate, and therefore it is with 
reference to this stage that I first use the word. That this 
stage of the process of inference is reached by nearly all the 
warm-blooded animals, and even by some of the Invertebrata, 
no one, I think, can possibly question. If, however, any one 
should do so, I must refer him to my previous work ; for the 
instances there given are so numerous that it would be tedious 
here to reproduce even the more striking among them.* To 
my mind the most remarkable of these instances are those 
which have reference to the Hymenoptera ; for although the 
faculty does not attain to so high a level of development 
among them as it does among some of the warm-blooded 
Yertebrata, it certainly has attained to much more than a 

* For tlie sate at once of giving a striking example of reason in an 
animal most nearly approaching man, and of supplementing a deficiency in 
my former treatise, I shall here quote a passage from Dr. Bastian's work on 
The Brain as an Organ of Mind (p. 329). " In regard to the high degree of 
Intelligence of the Orang, we have the following, on the best of testimony, 
from Leuret, who says {Anat. Comp. du Si/st. Nerv., torn, i, p. 540) : — 

"' One of the Orangs, which recently died at the Menagerie of the Musce, 
■was accustomed, when the dinner-hour had come, to open the door of the 
room where he took his meals in company with several persons. As he was 
not sufficeintly tall to reach as far as the key of the door, he hung on to a 
rope, balanced himself, and after a few oscillations very quickly reached the 
key. His keeper, who was rather worried by so much exactitude, one day 
took occasion to make three knots in the rope, which, having thus been made 
too short, no longer permitted the Orang-outang to seize the key. The 
animal, after an ineffectual attempt, recognizing the nature of the ohxtacle 
which opposed his desire, climbed up the rope, placed himself above the knots, 
and untied all three, in the presence of M. Geoif'roy Saint-Ililaire, who related 
the fact to me. The same ape wishing to open a door, his keeper gave him a 
bunch of fifteen keys ; the ape tried them in turn till he had found the one 
which he wanted. Another time a bar of iron was put into his hands, and he 
made use of it as a level'." ' 



REASON. 829 

proportional development in them ; and tliis whether we 
consider their position in the zoological scale, or the general 
structure of their psychology as compared with that of other 
animals — so that if the whole structure of their psychology 
were correspondingly advanced, these insects would deserve 
to be placed on a psychological level with Birds, if not with 
some of the more intelligent of the Mammalia. But looking 
to their psychology as a whole, I think that its status may 
most fairly be assigned to the level on which I have placed it 
in the diagram. However, I do not conceal that the peculiar 
nature of ant and bee intelligence makes it most difficult to 
compare with the intelligence of higher animals. 

Another special difficulty with reference to reason in 
animals meets us in the case of the Beaver. For, as remarked 
in " Animal Intelligence," " on the one hand it seems in- 
credible that the beaver should attain to such a level of 
abstract thought as would be implied by his forming his 
various structures with the calculated purpose of achieving 
the ends which they undoubtedly subserve. On the other 
hand, as we have seen, it seems little less than impossible 
that the formation of these structures can be due to instinct." 
The structures specially alluded to in this connection were 
the beaver canals, and my information concerning them was 
derived exclusively from the work of the late Mr. Lewis H. 
Morgan. Since the publication of " Animal Intelligence,'* 
however, I am informed from private sources that the intelli- 
gence of the beaver has been greatly over-estimated. My 
correspondents have undoubtedly seen much of the habits of 
American beavers ; but as I place confidence in the observa- 
tions of Mr. Morgan, I do not feet entitled to allow the 
counter-statements of my correspondents to nullify them. 
Still, I must allow such counter-statements to carry a con- 
siderable degree of weight, and therefore I feel that at present 
it is most judicious to say that, pending further and trust- 
worthy observations, I am not really in a position to discuss 
the quality of reason as it occurs in this animal. On this 
account I should not here have referred to the subject at all, 
were it not that in my previous work I promised to discuss it 
in the present one. Finding, however, since then, that the 
facts do not appear to be so certain as I supposed, I prefer, 
with this explanation, to allow the matter drop. 



330 MENTAL EVOLUTION IN ANIMALS. 

Eecurring now to my views on the origin and develop- 
ment of Eeason, it will have been noticed that they differ 
materially from those of Mr. Herbert Spencer, and, therefore, 
looking to the influence which he justly exerts upon all 
matters relating to psychological analysis, I feel that it is 
desirable to enter at some length into an explanation of the 
ground on which I have been here reluctantly compelled to 
disagree with him. Possibly the divergence between us may 
not be so important as at present I am led to suppose ; but if 
it should hereafter admit of being shown that such is not the 
case, I need scarcely say that the fact would be a matter of 
sincere gi-atification to me. 

According to Mr. Spencer, Eeason arises out of " com- 
pound reflex action " or " Instinct," when this reaches a 
certain level of compounding or complexity.* Now I have 
already given the considerations which induce me to differ 
from Mr. Spencer in regarding Instinct as compound reflex 
action, and therefore it is only in a general way that I am 
able to agree with him in his theory of the origin and de- 
velopment of Eeason. Nevertheless, in a general way I am 
able to agree with him, and therefore I shall begin by stating 
the points in which I do so. 

Eirst he says : — " The impossibility of establishing any 
line of demarkation between the two [Instinct and Eeason] 
may be clearly demonstrated. If every instinctive action is 
an adjustment of inner to outer relations, and if every 
rational action is also an adjustment of inner relations to 
outer relations ; then, any alleged distinction can have no 
other basis than some difference in the characters of the 
relations to which the adjustments are made. It must be 
that while, in Instinct, the correspondence is between inner 
and outer relations that are very simple or general ; in Eeason, 
the correspondence is between inner and outer relations that 
are complex, or special, or abstract, or infrequent. But the 
complexity, speciality, abstractness, and infrequency of rela- 
tions, are entirely matters of degree. . . . How then 
can any particular phase of complexity or infrequency be 
fixed upon as that at which Instinct ends and Eeason 
begins ? "f 

With this statement I quite agree, provided I am allowed 

* See Principles of Psychology, i, pp. 253-71. 
•f Loc. cd., pp. 453-4. 



EEASON. 331 

to make the important addition that it must be strictly 
limited to the objective aspect, as distinguished both from the 
subjective and ejcctive aspects of the phenomena. In other 
words, if we have regard only to the physical aspect of the 
phenomena (i.e., the physiology of ganglionic processes as 
expressed in the adjustive movements of organisms), this 
statement of the case is unexceptionable. But if we pass 
from physiology to psychology, the statement ceases to be 
adequate ; for both in the region of subjective and of ejective 
psychology it would fail to express the important distinction 
between two very different acts of mind — viz., one in which 
there is no knowledge of the relation between means em- 
ployed and ends attained, and one in which there is such 
knowledge.* 

But, passing over this point, we arrive at a lucid state- 
ment of the view that " when the correspondence has advanced 
to those environing objects and acts which present groups of 
attributes and relations of considerable complexity, and which 
occur with comparative infrequency — when, consequently, the 
repetition of experiences has been insufficient to make the 
sensory changes produced by such groups cohere perfectly 
with the adaptive motor changes — when such motor changes 
and the impressions that accompany them simply become 
nascent : then, by implication, there result ideas of such 
motor changes and impressions, or, as already explained, 
Tnemories of the motor changes before performed under like 
circumstances, and of the concomitant impressions." Siill 
there is not yet any manifestation of rationality. But now, 
" when the confusion of a complex impression with some 
allied one causes a confusion among the nascent motor exci- 
tations, there is entailed a certain hesitation, and .... 
ultimately some one set of motor excitations will prevail over 
the rest." The strongest set will eventually pass into action, 
and as this set will usually have reference to the circumstances 
which have recurred most frequently in experience, " the 
action will, on the average of cases, be the one best adapted 
to the circumstances. But an action thus produced is nothing 

* It -will be observed tbat if we adopt Mr. Spencer's definition of Instinct, 
tbe breacb. on the mental side is still further widened — the distinction 
between Instinct and Season being then equivalent to the distinction between 
nervous actions having no mental counterparts at all, and nervous actions 
which on their subjective side are intentionally adaptive. 



oo2 MENTAL EVOLUTION IN ANIMALS. 

else than a rational one This, however, is just 

the process which we saw must arise whenever, from increas- 
ing complexity and decreasing frequency, the automatic adjust- 
ment of inner to outer relations becomes uncertain and 
hesitating. Hence it is clear that the actions we call instinc- 
tive pass gradually into the actions we call rational." 

Now in an earlier part of this treatise I have stated my 
belief that consciousness arises when a nerve-centre is sub- 
jected to a comparative turmoil of molecular forces, which 
finds its physiological expression in delay of response, or, as 
Mr. Spencer says, in "hesitation." But I do not believe that 
in all such cases Eeason, as distinguished from Consciousness, 
must arise. Therefore I should say that, although there 
cannot be Eeason without such ganglionic friction, there 
may be such ganglionic friction without Eeason. There may, 
for example, be a large, and even a distressing amount of 
such friction produced in the case of a conflict of instincts ; 
there may in such cases be prolonged delay ending in " the 
strongest group of antagonistic tendencies at length passing 
into action ;" and yet no act of reason need arise. 

In what respect, then, do I differ from Mr. Spencer touch- 
ing the genesis of Eeason ? I differ from him, firstly, in not 
deeming an act of reason as such a constant or invariable 
index of ganglionic disturbance greater than that which may 
arise under other circumstances of psychical activity (and 
therefore in not deeming that reason must necessarily arise out 
of such disturbance) ; and, secondly, in not deeming that 
Eeason can only arise out of Instinct. 

Taking these two points of difference separately, it will be 
enough to say of the first that it has reference only to the 
earliest origin of Eeason, or to acts of reason of the simplest 
kind ; in the case of more elaborate processes of reasoning 
I have no doubt that the ganglionic disturbance must be 
great, and that without such disturbance these more elaborate 
processes would not be possible. But this, of course, is a 
widely different matter from concluding that wherever gan- 
glionic disturbance reaches a certain degree of complexity, 
leading to a consequent delay of response, there Eeason (as 
distinguished from vividness of consciousness) must neces- 
sarily arise. On the contrary, I hold that in the lower stages 
of what I have defined as Eeason (and, a fortiori, in all the 
stages of what I have defined as Inference), there may not be 



REASON. 333 

more, and there may not be even so much ganglionic dis- 
turbance or consequent delay of response, as there may be 
where no act of rationality is concerned — as, e.g., in a conflict 
of instincts. 

Turning now to my second point of difference with 
Mr, Spencer, I can see no adequate ground for concluding 
with him that Eeason can only arise out of Instinct. On the 
contrary, holding, as I have explained, that Eeason has its 
antecedents in the habitual inferences of sensuous perception, 
that Instinct (as distinguished from Eeflex Action) likewise 
has its antecedents in sensuous perception, and that neither 
Eeason nor Instinct can advance beyond this first origin 
without an always corresponding advance in the powers of 
perception ; holding these views, I am forced to conclude that 
Perception is the common stem out of which Instinct and 
Eeason arise as independent branches. In so far as Percep- 
tion involves Inference, Instinct involves Perception, and 
Eeason involves Inference, there arises, of course, a genetic 
connection between Instinct and Eeason ; but this connection 
is clearly not of the kind which Mr. Spencer indicates : it is 
organic, and not historic. 

This important divergence in my views from those of 
Mr. Spencer I take to be due to his manner of regarding the 
relations that subsist between nervous changes which are 
accompanied by Consciousness, and nervous changes which 
are not so accompanied. Thus the divergence between our 
views on this matter began so far back as in our respective 
analyses of Memory, where I observed, " I cannot agree that if 
psychical changes (as distinguished from physiological changes) 
are completely automatic, they are on this account to be 

precluded from being regarded as mnemonic In 

so far as they involve the presence of conscious recognition, as 
distinguished from reflex action, so far, I think, no line of 
demarcation should be drawn between them and any less 
perfect memories."* Again, the divergence was manifested 
when I came to treat of Perception, and I there gave m^ 
reasons for regarding it as " very questionable whether the only 
factors which lead to the differentiating of psychical processes 
from reflex nervous processes are (as Mr. Spencer alleges) 
complexity of operation combined with infrequency of occur- 
rence."t And the divergence in question became still more 

* See p. 130. t See p. 140. 

15 



334 MENTAL EVOLUTION IN ANIMALS. 

pronounced when I arrived at my analysis of Instinct ; for 
hy identifying Instinct with compound reflex action, we found 
it to be evident that Mr. Spencer wholly disregards what I 
take to be the essentially distinguishing feature of Instinct, 
viz., the presence of Perception as distinguished from Sensa- 
tion. Thus, lastly, when we now come to the province of 
Eeason, the same divergence recurs. Whether for the special 
purpose in hand I accept Mr. Spencer's definition of Instinct 
as compound reflex action, or adhere to my own definition of 
it as reflex action into which there is imported the element 
of consciousness, I alike find it impossible to agree with 
him that Eeason necessarily and only arises out of Instinct. 

For, taking first Mr. Spencer's definition of Instinct, I 
cannot agree that Eeason necessarily and only arises out of 
compound reflex action, because I see it to be a fact that in 
the higher organisms we meet with numerous cases of 
enormously compound reflex actions which present no indi- 
cations of rationality. And some of these cases, it may be 
parenthetically observed, can never at any period of their 
developmental history have been rational, and afterwards 
have become automatic by frequency of repetition. Such, for 
example, cannot have been the case with the compound reflex 
actions which are concerned in parturition, nor with those 
more obscure reflex actions which now bafile our rationality 
to comprehend — I mean the changes set up by an impreg- 
nated ovum in the walls of the uterus. These are instances 
of immensely compound reflex actions which must always 
have occurred with great rarity in the life-history of indi- 
viduals, and can never at any time have been either the cause 
or the effect of rationality. 

Again, taking my own definition of Instinct, I cannot 
agree that Eeason necessarily and only arises out of reflex 
action into which there is imported the element of conscious- 
ness. For this element is merely the element of Perception, 
and I do not know of any evidence to justify the conclusion 
that Perception can only arise out of the growing complexity 
and infrequency of reflex actions. As I said in my chapter 
on Perception, •' the truth is that, so far as definite knowledge 
entitles us to say anything, the only constant physiological 
difference between a nervous process accompanied by con- 
sciousness and a nervous process not so accompanied, is that 
of time. In very many cases no doubt this difference may 



EEASON. 835 

be caused by the intricacy or tlie novelty of tlie nervous pro- 
cess which is accompanied by consciousness;"* but seeing that 
in ourselves, as just observed, highly intricate and very infre- 
quent nervous processes may take place mechanically, I do 
not think we are justified in concluding that complexity and 
infrequency of ganglionic action are the only factors in deter- 
mining the rise of consciousness. But even supposing, for 
the sake of argument, that they are, still it would not follow 
that the only road to Eeason lies through Instinct. Percep- 
tion being the element common both to Instinct and to 
Eeason, it may very well happen (and indeed I think 
actually does happen) that Eeason arises directly out of those 
automatic inferences which, as we have seen, are given in 
Perception, and which, as we have also seen, furnish the con- 
ditions to the origin of Instinct. 

From this statement, however, I hope it will be manifest 
that I do not dispute that Eeason may, and probably does in 
many cases arise out of Instinct, in that the perceptive basis 
of Instinct is so apt to yield material for the higher percep- 
tions of Eeason. I merely object to the doctrine that Eeason 
can arise in no other way. And, as further showing the 
untruth of this doctrine, I may in conclusion point to the 
numberless instances given in my chapters on Instinct of the 
reciprocal action between Instinct and Eeason — the develop- 
ment of the former sometimes leading to the higher develop- 
ment of the latter, and sometimes, as in all cases of the 
formation of Instinct by lapsing intelligence, the development 
of the latter leading to the higher development of the former. 
Such reciprocal action could not take place were it true that 
Instinct is always and necessarily the precursor of Eeason. 

I must not take leave of this discussion on Eeason with- 
out briefly alluding to the very prevalent view— with which of 
course I do not agree — that the faculty in question is the 
special prerogative of Man. As the most enlightened and 
best informed writer who of late years has espoused this 
doctrine is Mr. Mivart, I shall take him as its exponent, and 
in examining his arguments on the subject I shall consider 
that I am examining the best arguments which can be 
adduced in support of the view in question. 

Mr. Darwin, in his " Descent of Man," gives the foUow- 
* See p. 110. 



336 MENTAL EVOLUTION IN ANIMALS. 

ing account of tlie exhibition of Eeason on the part of a 
Crab : — " Mr. Gardner, whilst watching a shore crab (gelasi- 
mus) making its burrow, threw some shells towards the hole. 
One rolled in, and three other shells remained within a few 
inches of the mouth. In about five minutes the crab brought 
out the shell which had fallen in, and carried it away to the 
distance of a foot ; it then saw the three other shells lying 
near, and evidently thinking that they might likewise roll in, 
carried them to the spot where it had laid the first. It 
would, I think, be difficult to distinguish this act from one 
performed by man by the aid of reason."* 

Mr. Mivart, after quoting the above, calls the concluding 
sentence an " astonishing remark."t I shaU, therefore, pro- 
ceed to consider the very prevalent opinion to which such a 
commentary introduces us, and which consists, as I have said, 
in regarding the faculty of Eeason as the special prerogative 
of Man. 

I must begin by again observing that the faculty of 
Eeason, in the sense of a " knowledge of the relation between 
means employed and ends attained, .... admits of 
numberless degrees ; " and I hold it to be a mistake, greater 
than any other that has been committed in psychological 
science, to suppose that there is any difference of hind 
whether this faculty is exercised with reference to the highest 
abstractions of introspective thought, or to the lowest pro- 
ducts of sensuous perception ; whether the ideas involved are 
g-eneral or special, complex or simple, wherever there is a 
process of inference from them which results in establishing 
a proportional conclusion among them, there we have some- 
thing more than the mere association of ideas ; and this 
something is Eeason. If I were to see a large stone falling 
through the roof of my conservatory, and on climbing to the 
wall above saw three or four other stones just upon the edge, 
I should infer that the stones which fell previously stood in 
a similar relation to my conservatory, and therefore that it 
would be desirable to remove the others from their threaten- 
ing position. This would not be an act of association, but an 
act of reason (though a simple one), and it is psychologically 
identical with the act which was performed by the crab. 

Further, according to J. S. Mill, " all inference is from 
particulars to particulars: General propositions are merely 

* Descent of Man, p. 270. t Leasuns from Nature, p. 213. 



REASON. 337 

registers of such inferences already made, and short formiilse 
for making more." Now although this doctrine is not 
universally accepted hy logicians — Whately, for instance, 
having maintained the exact converse, and many minor 
writers more or less agreeing with him, — I feel compelled to 
fall in with it on purely logical grounds, or without reference 
to any considerations drawn from the theory of evolution. 
For it appears to me that Mill is completely successful in 
showing that only hy this doctrine can the syllogism he 
shown to have any functions or any value. " It must he 
granted that in every syllogism, considered as an argument 
to prove the conclusion, there is a petitio principii. When 
we say. All men are mortal ; Socrates is a man ; therefore 
Socrates is mortal ; it is unanswerably urged by the adver- 
saries of the syllogistic theory that the proposition, Socrates 
is mortal, is presupposed in the more general assumption, All 
men are mortal." Therefore, " no reasoning from generals to 
particulars can, as such, prove anything : since from a general 
proposition we cannot infer any particulars, but those which 
the principle itself assumes as known." This is not a suit- 
able place in which to discuss such a question of logic at 
length, and therefore I shall merely refer to Mill's exposition 
of it.* But as I can see no escape from the view which he 
enforces that the major premiss of a syllogism is merely a 
generalized memorandum of past particular experiences, and 
therefore that all reasonmg is, in the last resort, an infer- 
ence from particulars to particulars ; I think that this con- 
clusion (arrived at without reference to the theory of 
evolution) is available to argue that there is no difference in 
kind between the act of reason performed by the crab and 
any act of reason performed by a man. 

It must be remembered that I am not now discussing the 
larger question as to whether there is any distinction in kind 
between the whole mental organization of an animal and the 
whole mental organization of a man. This larger question I 
shall fully discuss in my subsequent work. Here I am only 
endeavouring to show that so far as the particular faculty of 
mind is concerned which falls under my definition of reason, 
there is no such distinction. A process of conscious infer- 
ence, considered merely as a process of conscious inference, 

* Logic, vol. i, Chap. IlL 



S38 MENTAL EVOLUTION IN ANIMALS. 

is the same in kind wherever it occurs and whatever degree 
of elaboration it presents. 

But here I must meet an assertion which is often made, 
and wliich has been presented by Mr. Mivart with his 
accustomed adherence to logical form, and therefore with 
much apparent cogency. He says : — " Two faculties are 
distinct in kind if M^e may possess the one in perfection 
without thereby implying that we possess the other ; and 
still more so if the two faculties tend to increase in an 
inverse ratio, the perfection of the one being accompanied by 
a degradation of the other. Yet this is just the distinction 
between the instinctive and rational parts of man's nature. 
His instinctive actions are, as all admit, not rational ones ; 
his rational actions are not instinctive. Even more than this, 
we may say the more instinctive a man's actions the less 
are they rational, and vice versd ; and this amounts to a 
demonstration that reason has not, and by no possibility 
could have been, developed from instinct. In man we have 
this inverse ratio between sensation and perception, and in 
brutes it is just where the absence of reason is most generally 
admitted {e.g., in insects) that we have the very simimit and 
perfection of instinct made known to us by the ant and the 
bee. ... Sir William Hamilton long ago called atten- 
tion to this inverse relation ; but when two faculties tend to 
increase in an inverse ratio, it becomes unquestionable that 
the difference between them is one of kind."* 

Now I meet this argument by denying the alleged fact on 
which it reposes. It is simply not true that there is any con- 
stant inverse ratio of the kind stated. It is no doubt true in a 
general way (as the principles of evolution would lead us to 
anticipate), that as animals advance in the scale of mental 
development their powers of intelligent adjustment are apt 
to become added in larger measure to their less elaborate 
powers of instinctive adjustment; but that there is no inverse 
proportion between the two must be evident to any one who 
has directed his attention to the mental endowments of 
animals. Thus, so far is it from being the case that " the 
absence of reason is most generally admitted" among the 
ants and bees, that all the observers with whose writings I 
am acquainted are unanimous in their opinion that there are 
no animals among the Invertebrata which can be said to 

* Lessom from Nature, pp. 230-1, 



EEASON, 339 

equal the ants and bees in respect of drawing intelligent 
inferences. Furthermore, looking to the animal kingdom as 
a whole, I should say that while there is no very constant 
relationship between the powers of instinct and those of 
intelligent inference, such relationship as there is points 
rather to the view that the complexity of mental organization 
which finds expression in a high development of the instinc- 
tive faculties, is favourable to the development of the more 
intelligent faculties.* And that there should be such a 
general correspondence is no more than the theory of evolu- 
tion might lead us to expect ; for the progressive complica- 
tion of instincts tends to diminish, as Mr. Spencer observes, 
their purely automatic character. But, on the other hand, 
that this correspondence should be general and not constant 
might also be anticipated, seeing that instincts may arise 
either without the precedence of intelligence, or by means of 
the lapsing of intelligence. 

In the next place, as regards Man, I do not think that 
Mr. Mivart's argument is any more satisfactorily established 
by fact. It is no doubt true that " the more instinctive are a 
man's actions the less are they rational, and vice versd;" but 
this, again, is no more than we should expect, on the hypo- 
thesis of human instincts being due to hereditary experience, 
while processes of conscious inference are chiefly due to indi- 
vidual experience. It thus happens that the instinctive 
actions preponderate over the intelligent actions during 
infancy, and that the scale begins to turn during childhood. 
But in all this there is nothing to show that the two are 
distinct in kind ; and in subsequent life their generic identity 
is shown by the fact that the principle of lapsing intelligence 
may cause, even in the experience of the individual, actions 
which are at first consciously adaptive or rational to become 
by repetition automatic or instinctive. 

To what misconception, then, are we to ascribe the very 
prevalent doctrine that Eeason is the special prerogative of 
Man ? I think the misconception arises from an erroneous 
meaning which is attached to the word Eeason. Mr. Mivart, for 
instance, habitually follows the traditional usage and invests 
the word with the meaning that belongs to self-conscious 
Thought. Thus he expressly says that in denying Eeason to 

* Cf. Fouchet, " L^ Instinct chez les Insedes" in Eev. des Deux Mondes, 
Feb. 1870, p. 690. 



340 MENTAL EVOLUTION IN ANIMALS. 

brutes all he maintains is that " they have not the power of 
forming judgments ;"* that is, in his own definition of a 
judgment, the power of reflective or self-conscious Thought. 
In my subsequent work I shall have much to say upon the 
psychology of Judgment ; but here it is enough to observe 
that I hold the power of reflective thought, which the forma- 
tion of a judgment implies, to constitute no essential part of 
a process of reason as such, although when present it unques- 
tionably affords that process much new material with which to 
be concerned. As I have said, I regard reasoning to be a process 
of consciously inferring, and therefore conclude that it should 
make no difference to our classification of the rational faculty 
whether the subject matter on which it may happen to be 
exercised has reference to the sphere of feeling or to that of 
thought. And, as Mr. Mivart allows that animals perform 
" practical inferences," I further conclude that my difference 
with the school which he represents has reference, so far, only 
to a matter of terminology. There is, without question, some 
enormous distinction between the psychology of man and 
that of the lower animals, and hereafter I shall have to 
consider at much length what this distinction is. Here I 
am only concerned with showing that it does not consist in 
animals having no vestige of the faculty of Reason in the 
sense above defined. And, in order to show this, I feel, as I 
have already remarked, that it would be superfluous to render 
specific instances of the display of animal reason ; for they 
have already been given in such abundance in my former 
work. 

" Is not the earth 
"With various living creatures, and the air 
Eeplenished? .... know' st thou not 
Their langixage and their ways ? They also know 
And reason not contemptibly." — Milton. 



* Lessons from Nature, p. 217. 



EMOTIONS. 341 



CHAPTER XX. 

Animal Emotions, and Summary of Intellectual 
Faculties. 

It will be observed on turning to the diagram that I attribute 
to animals the following emotions, which I name in the 
probable order of their historical development: — Surprise, 
Fear, Sexual and Parental Affection, Social Feelings, Pug- 
nacity, Industry, Curiosity, Jealousy, Anger, Play, Affection, 
Sympathy, Emulation, Pride, Resentment, -Esthetic Love 
of Ornament, Terror, Grief, Hate, Cruelty, Benevolence, 
Revenge, Rage, Shame, Remorse, Deceit, Ludicrous. This list, 
which leaves many of the human emotions without men- 
tion, exhausts all the emotions of which I have found any 
evidence in the psychology of animals. Before presenting 
this evidence in detail, perhaps it will not be thought 
superfluous again to insist that in attributing this and 
that emotion to such and such an animal, we can depend 
only upon inference drawn from actions, and that this 
inference necessarily becomes of less and less validity as we 
pass through the animal kingdom to organisms less and less 
like our own ; so that, for instance, " when we get as low 
down as the insects, I think the most we can confidently 
assert is, that the known facts of human psychology furnish 
the best available pattern of the probable facts of insect 
psychology."* Still, as the known facts of human psychology 
do furnish the best available pattern, w^e must here, while 
treating of the emotional faculties, follow the same method 
which we have hitherto followed while treating of the intel- 
lectual faculties — viz., while having full regard to the pro- 
gressive weakening of the analogy from human to brute 
psychology as we recede through the animal kingdom down- 
wards from man, nevertheless using the analogy so far as it 
goes as the only instrument of analysis that we possess. 

* Animal Intelligence, pp. 9-10, where see for a more full discussion of 
tliis point. 



342 MENTAL EVOLUTION IN ANIMALS. 

I shall now proceed, as briefly as possible, to render the 
evidence which has induced me to ascribe each of the above- 
named emotions to animals, and remembering that I have in 
each case written the emotion upon the diagram at the level 
of mental evolution where I have found the earliest evidence 
of its occurrence, it follows that in the majority of cases the 
emotion is present in the higher levels of mental evolution 
in a more highly-developed form. 

It will be observed that in the diagram I represent the 
Emotions as a class to take their origin from the growing 
structure of mind at the same level as that at which the 
faculty of Perception takes its origin. I do this because I 
think that as soon as an animal or a young child is able to 
perceive its sensations, it must be able to perceive pleasures 
and pains ; hence, when the antecedents of a painful percep- 
tion recur in consciousness, the animal or child must anticipate 
the recurrence of that perception — must suffer an ideal 
representation of the pains, and such suffering is Fear. And 
that, as a matter of fact. Fear of this low or vague order is 
manifested at about the second or third week of infancy, is 
the general opinion of those who have most carefully 
observed the development of infant psychology.* To specify 
the class in the animal kingdom where a true emotion of 
Fear first arises is clearly a more difficult matter, and indeed 
it is impossible to do so in the absence of any definite know- 
ledge as to the class in which Perception first arises. But while, 
as previously explained, I am not able to say whether or not 
the Coelenterata, and still less the Echinodermata, are able to 
perceive their sensations, I think the evidence becomes very 
strong in the case of insect Larvse and Worms. And that both 
the one and the other manifest striking symptoms of alarm 
in the presence of danger may be easily shown. For instance, 
a few months ago I had an opportunity of observing the 
habits of the processional caterpillar mentioned in " Animal 
Intelligence."t Wishing to ascertain whether I could artifi- 

* See Prcyer, loc. cit. 

X Pp. 238-40. It will be seen on referring to this passage that De 
Villiers' account differs materially from that of Mr. Davis. For he says that, 
on removing one of the chain of caterpillars, the whole chain Btoppod imme- 
diately with one consent, like a single organism. Mr. Davis on the other 
hand said that the information was communicated from caterpillar to cater- 
pillar at the rate of somewhat less than a second per caterpillar. On repeat- 
ing this observation a great number of times, I could obtain no corroboration 
at all of De Villiers' statement, while I found that of Mr. Davis to be correct 



EMOTIONS. 64:6 

cially imitate the stimulus which the head of one caterpillar 
supplied to the tail of the next in the series (and which 
serves to let the latter known that the series is not inter- 
rupted), I removed the last member of the series. As always 
happens when this is done, the next member stopped, then 
the next, and the next, and so on, till the whole series were at 
a halt. If I had now replaced the last member with its head 
touching the tail of the penultimate member, the latter would 
again have begun to move, then the next, and the next, and 
so on, till the whole series would again have been in motion. 
Instead of doing this, however, I took a camel-hair brush and 
gently brushed the tail of the then last member. Imme- 
diately this member again began to move, and so set the 
whole train again upon the march. But in order that the 
march should continue, it was necessary that I should con- 
tinue brushing the tail of the last member. Now I found 
that if I brushed in the least degree too hard, so as not suffi- 
ciently well to imitate the stimulus supplied by the hairy 
head of a caterpillar, the animal became alarmed and threw 
itself upon its side in the form of a coiL I therefore tried 
the experiment of puzzling the animal, by first brushing its 
tail gently for a considerable time — so that it should have no 
reason to doubt, as it were, that I was a caterpillar — and 
then beginning by degrees to brush it more and more strongly. 
I could then see that a point came at which the animal was 
puzzled, so that it hesitated whether to go on or to throw 
itself upon its side. It appeared to me that at this point the 
animal began to become alarmed ; for the brushing was still 
exceedingly gentle, so that if the animal were actuated only 
by a pure reflex mechanism, I should not have expected so 
infinitesimally small a difference in the amount of stimula- 
tion to produce so great a difference in the nature of the 
response. 

in all particulars. I am likewise able to confirm all the other points in his 
account of the remarkable habits of these larvae. I may add that as soon as 
a member of a moving chain is removed, the next member in advance not 
only stops, but begins to wag its head in a peculiar manner from side to side. 
This perhaps may serve as a signal to the next member to stop ; but, however 
this may be, as soon as the next one does stop, it also begins to wag its head 
in the same manner, and so on till all the caterpillars in advance of the 
interruption are standing still and wagging their heads. And they all 
continue vrithout interruption thus to wag their heads rmtil the procession 
again begins to move. I have never seen this peculiar movement performed 
except imder these circumstances. 



344 MENTAL EVOLUTION IN ANIMALS. 

Again as regards Worms, Mr. Darwin has shown in his 
work on the Earth-worm that this animal is of a " timid " 
disposition, darting into its burrow "like a rabbit" when 
alarmed. Probably other kinds of worms, which are better 
provided with organs of special sense and consequently have 
more intelligence, may have more emotion. 

With reference to young children, Preyer is of the opinion 
that the earliest emotion is one of surprise or astonishment 
upon perceiving any change, or strikingly novel feature, in the 
environment. In deference to his opinion, therefore, I have 
placed Surprise upon the same level of emotional develop- 
ment as Fear ; but of course in both cases this level is so 
low that it is but the germs of such emotions that are here 
supposed to be present. 

This earliest stage of emotional development (18) I have 
made to correspond with " Emotions preservative of Self" 
The next stage (19) I make to coincide with the origin of 
" Emotions preservative of Species ; " and of these the first 
to appear are the Sexual. In the animal kingdom — or 
rather let us say in the psychological scale — these emotions 
are first unequivocally exhibited by the MoUusca,* which on 
this account, as well as for the reasons given while treating 
of the association of ideas, I have made to fill the corre- 
sponding level on the other side of the diagram. 

The next level (20) is occupied by Parental Affection, Social 
Feelings, Pugnacity, Emotions conducing to Sexual Selection, 
Industry, and Curiosity. The level, therefore, corresponds 
with the origin of the branch marked Social Emotions in tlie 
central psychological tree, and with the earliest Recognition 
of Offspring on the side of the intellectual faculties. The 
animals which first satisfy all these conditions are the Insects 
and Spiders.f For here, even if we exclude the Hymenoptera, 
we have evidence of parental affection in the care which 
spiders, earwigs, and sundry other insects take of their eggs 
and broods.f Again, numberless species of insects are highly 
social in their habits ; others are highly pugnacious ; some 
are conspicuously industrious ;| most flying insects (as we 
have already seen in Chapter XVIII) display curiosity ; and, 
according to Mr. Darwin's elaborate enquiries, it is also in 

* See Animal Intelligence, p. 26. 

t For remarkable instances of this see ibid., p. 205 and p. 229. 

X I hid., pp. 22ti-8. 



EMOTIONS. 345 

this class that we find the earliest evidence of sexual selec- 
tion. 

Coming now to level 21, I have assigned to it the first 
appearance of the emotions of Jealousy, Anger, and Play, 
which unquestionably occur in Fish.* On level 23 I have 
placed the dawn of Affection other than sexual, in view 
of the evidence of the emotional attachment of a python 
which was exhibited towards those who had kept it as a 
petf 

On level 24 I have placed the dawn of Sympathy, seeing 
that this emotion appears to be unquestionably, though very 
fitfully, displayed by the Hymenoptera,| which for other 
reasons I have felt obliged to assign to this comparatively 
high stage of psychological development. 

On the next level (25) 1 have given Emulation, Pride, 
Eesentment, Esthetic Love of Ornament, and Terror as dis- 
tinguished from Pear. All these emotions, so far as I have 
been able to ascertain, first occur in Birds ; and in this 
class some of the emotions which I have already named a,s 
occurring in lower classes, are much more highly developed. § 

Next we arrive at Grief, Hate, Cruelty, and Benevolence, 
as first displayed in some of the more intelligent of the Mam- 
malia. Grief is shown by pining, even to death, upon the 
removal of a favourite master or companion ; Hate by per- 
sisting resentment ; Cruelty by a cat's treatment of a mouse ;|| 
and Benevolence by the following instances which I have 
met with since the publication of " Animal Intelligence." 
Writing of a domestic oat, Mr. Oswald Pitch says that it 
" was observed to take out some fish-bones from the house to 
the garden, and, being followed, was seen to have placed them 
in front of a miserably thin and evidently hungry stranger 
cat, who was devouring them ; not satisfied with that, our cat 
returned, procured a fresh supply, and repeated its charitable 
offer, which was apparently as gratefully accepted. This act 
of benevolence over, our cat returned to its customary dining- 
place, the scullery, and ate its own dinner off the remainder 

* See Animal Intelligence, pp. 242-47. 
t Ibid., pp. 261-2. 

I Ibid., pp. 48-9 and p. 156. 

§ Ibid., pp. 270-82. Birds are tlie lowest animals wliicli I have myself 
seen, or have heard of others having seen, to die of fright. 

II For instances of all these facts in Mammals other than Elephants, 
Dogs or Monkeys, see Animal Intelligence. 



346 MENTAL EVOLUTION IN ANIMALS. 

of the bones."* An almost precisely similar case has been 
independently communicated to me by Dr. Allen Thomson, 
F.RS. The only difference was that Dr. Thomson's cat drew 
the attention of the cook to the famishing stranger outside by 
pulling her dress and leading her to the place. When the 
cook supplied the hungry cat with some food, the other one 
paraded round and round while the meal was being discussed, 
purring loudly. One further instance of the display of bene- 
volent feeling by a cat will suffice. Mr. H. A. Macpherson 
writes me that in 1876 he had an old male cat and a kitten 
aged a few months. The cat, who had long been a favourite, 
was jealous of the kitten and " showed considerable aversion 
to it." One day the floor of a room in the basement of the 
house was partly taken up in order to repair some pipes. The 
day after the boards had been replaced, the cat " entered the 
kitchen (he lived almost wholly on the drawing-room floor 
above), rubbed against the cook and mewed without ceasing 
until he had engaged her attention. He then, by running to 
and fro, drew her to the room in which the work had taken 
place. The servant was puzzled until she heard a faint mew 
from beneath her feet. On the boards being lifted the kitten 
emerged safe and sound, though half-starved. The cat watched 
the proceedings with the greatest interest until the kitten was 
released ; but on ascertaining that it was safe he at once left 
the room, without evincing any pleasure at its return. Nor 
did he subsequently become really friendly with it." 

On the next level I have placed Revenge as distinguished 
from Eesentment, and llage, as distinguished from Anger. 
In " Animal Intelligence " I give some cases of apparent 
vindictiveness occurring in birds ;t but as the exact nature of 
the emotions in these cases appears to me somewhat doubtful, 
I here disregard them, and place Revenge on the psycholo- 
gical level which is occupied by the Elephant and Monkeys, 
in which animals this passion is very conspicuous.! The 
same remarks apply to Rage, as distinguished from the less 
violent display of hostile feeling which is suitably expressed 
by the term Anger. 

Lastly, at level 28 we arrive at the highest products of 
emotional development which are manifested in animal 
jjsychology, and therefore at the highest of those products 

* Nature, AprH 19, 1883, p. 580. f Pp- 277-8. 

X Animal Intelliffence, pp. 387-8 and 478. 



EMOTIONS. 347 

with which the present treatise is concerned. These are 
Shame, Eemorse, Deceit, and the Emotion of the Ludicrous. 
Tor instances of the display of these emotions by Dogs and 
Apes, I need merely again refer to " Animal Intelligence."* 

In this brief sketch of the emotional faculties as they 
occur in the animal kingdom, my aim has been to give a 
generic rather than a specific representation. I have there- 
fore omitted all details of the emotional character of this and 
that particular animal, as well as the narration of particular 
instances of the display of emotions. Such details and par- 
ticular instances will be found in sufficient abundance in my 
previous work, and it seems undesirable, for the larger purpose 
now in hand, either to repeat what I have said before, or to 
burden the discussion with additional facts serving only to 
corroborate the general assignment of levels which I have 
now given. 

Before concluding the present chapter, and with it the 
present work, I shall give a similar outline sketch of the 
assignment of levels on the other and corresponding side of 
the diagram, which serves to show the probable history of 
mental evolution so far as the faculties of intellect are con- 
cerned. This, of course, has already been done throughout 
the course of all the preceding pages ; but I think it desirable 
to terminate our analysis of the psychology of animals, by 
briefly stating in a serial form the reasons which have induced 
me to assign the various classes of animals to the levels of 
psychological development in which I have respectively 
placed them. It is only needful to premise that in consider- 
ing this side of the diagram I shall not at present wait to 
treat of the column which has to do with the psycho- 
genesis of the child, for this will require to be treated ab 
initio in my work on Mental Evolution in Man. I may 
further observe that the sundry psychological faculties which 
I have written on one of the vertical colunms are intended as 
so many indices of mental evolution, and not as exhausting 
all the distinctions between one level of such evolution and 
another. Indeed, looking to the fact that our classification of 
faculties is conventional rather than natural, we cannot expect 
that any diagrammatic representation of the order in which 
they have been developed should admit of being made very 
* Pp. 438-45, and 471-78 ; also 484-98. 



348 MENTAL EVOLUTION IN ANIMALS. 

precise ; for in some existing animals certain faculties are 
more highly developed than they are in other existing 
animals, which nevertheless with regard to their general 
psychology occupy a higher level of mental evolution. There- 
fore the faculties which I have named in the vertical column 
have been chosen only because they serve as convenient 
indices to mark the general upward progress of mental evolu- 
tion in the animal kingdom. 

I have already sufficiently expressed my doubt as to the 
levels at which all animals below the Articulata should be 
placed, and I have explained that this doubt arises from the 
difficulty, or rather the impossibility of ascertaining at what 
grade of psychological evolution consciousness first occurs. 
The positions, therefore, which I have assigned to the Coelen- 
terata and Echinodermata are confessedly arbitrary, and have 
been determined only because I have not been able to observe 
that these animals give any unmistakable evidence of percep- 
tion as distinguished from sensation. This remark applies 
especially to the Ccelenterata, which in my opinion present 
no semblance of evidence that any of their responsive move- 
ments are of a perceptive, or even of a conscious nature. My 
judgment with respect to the Echinodermata is less confident, 
for although I am sure that I am right in placing them on a 
higher level of sensuous capability than the Ccelenterata, I 
am not at all sure that I ought not to have placed them one 
stage higher (i.e., on 18 instead of 17), so as to have 
brought them within the first rise of perception. Eor the 
" acrobatic " and " righting " movements which are per- 
formed by these animals, and which I have described elsewhere, 
are, to say the least, strongly suggestive of true powers of 
perception. It is, therefore, on the principle of preferring to 
err on the side of safety that I have placed the Echinoder- 
mata on level 17 and not on level 18. That I am justified 
in attributing to these animals faint powers of memory (as 
distinguished from the association of ideas) may, I think, be 
shown by the fact that when a star-fish is crawling along the 
perpendicular wall of a tank at the level of the surface of the 
water, it every now and then throws back its rays to feel for 
other surfaces of attachment, and if it does not succeed in 
finding such a surface, it again applies its rays to crawling 
along the side of the tank in the same direction as before, in 
order that it may again and again repeat the manoeuvre in 



EMOTIONS. 349 

different localities. Now, as this manoeuvre requires a long 
time to execute, I think the fact that after it has been 
executed the animal continues its advance in the same direc- 
tion as that in which it was crawling before the manoeuvre 
began, constitutes tolerable evidence in favour of an abiding^ 
impression upon the nerve-centres concerned, and one wliich 
assuredly is not due to any organically imposed conditions, 
seeing that on no two occasions is the manoeuvre performed 
in exactly the same way, or even at the same intervals of 
time. 

On the next level I have placed Larvse of Insects and 
Annelida. My reason for doing so is that both these classes 
of organisms unquestionably exhibit instincts of the primary 
kind,* the origin of which is also assigned to this level. In 
both cases, however, we meet with certain facts which may 
justly lead us to question whether in these animals intelli- 
gence of a higher order may not be present ;t but here again 
I think it is better to err on the safer side. 

It is in the MoUusca that we first undoubtedly meet with 
a demonstrable power of learning by individual experience,^ 
and therefore I have placed this class of animals upon the 
next level, which is occupied by the first appearance of the 
power of association by contiguity. Of course, if the account 
given by Mr. Lonsdale to Mr. Darwin of the pair of land- 
snails§ were ever to be corroborated by further observations, 
the Gasteropoda would require to be separated from the 
other MoUusca and placed on a higher level in the diagram, 
as I have done in the case of the Cephalopoda. 

Next we come to Insects and Spiders on a level with the 
first Eecognition of Offspring and the rise of Secondary 
Instincts. The evidence that both these faculties occur in 
both these divisions of the Articulata is unquestionable — 
and this even when the Hymenoptera are removed for 
separate psychological classification.!! 

Fish and Batrachia are assigned to the next level which 
corresponds with the rise of Association by Similarity, which 
I think we are justified in first ascribing to these animals.T^ 

On level 22 I have written the higher Crustacea. I 

* See Animal Intelligence, 234-40, and 24. 

+ Ibid., and Mr. Darwin's work on Worms. 

J Ibid., pp. 25-y. § Ibid., p. 27. 

j) Ibid., pp. 207-222, and 226-31. il Ibid., pp. 250-1, and 253. 



350 MENTAL EVOLUTION IN ANIMALS. 

have done so because this is the stage where, from inde- 
pendent considerations already explained, I have assigned 
the dawn of Eeason (as distinguished from Inference), and 
the lowest animal psychologically considered in which I 
have found any evidence of this faculty is the crab.* 

Next we come to level 23 where I have placed the 
Eeptiles and Cephalopoda; My reason for so doing is that 
this is the level where I have represented psychological 
development to have advanced sufficiently far to admit of 
the recognition of persons, and this degree of advance has 
undoubtedly been attained by the Eeptiles and the Cephalo- 
poda.! It will be observed that I have bracketed this and 
the two preceding levels together. My reason for doing so 
is that the animals and the faculties named upon these levels 
in some degree overlap. Thus the Batrachia are able to 
recognize persons,t and it is possible that Fish may be able 
to reason,§ while, on the other hand, the Eeptiles and Cepha- 
lopoda are not in their general psychology so far above 
the Batrachia and Fish as would be implied without the 
bracket ; yet I should not be justified in placing them all 
upon the same level, because I have no such definite evidence 
that Batrachia and Fish are able to reason as I have in the 
case of Crustacea, Cephalopoda, and Eeptiles. On the whole, 
therefore, I think that the fairest mode of expressing these 
various cross relations is the one which I have adopted. It 
is not to be expected that our essentially artificial mode of 
distinguishing between psychological faculties should so far 
agree with nature, that when applied to the animal kingdom 
our classification of faculties should always be found exactly 
to fit with our classification of organisms, so that every 
branch in our psychological tree should precisely correspond 
with some branch in our zoological tree. Some amount of 
overlapping must be expected, and in thus comparing the one 
classification with the other my only surprise has been how, 
in a general way, the two so closely coincide. 

On level 24 I have placed the Hymenoptera, together 
with the distinction which I think most sharply marks off" this 
stage of mental evolution, i.e., the power of communicating 
ideas — a power which ants and bees undoubtedly possess.|| 

* Soe Animal Intelligence, p. 233. J Ibid., p 255. 

+ Ibid., pp. 259, 2G0-1, and 30. § Ibid., pp. 250-1. 

II Ibid., pp. 49-57, and 156-00. 



EMOTIONS. 351 

Next we arrive at Birds with the psychological distinc- 
tion of recognizing pictorial representations, understanding 
words, and dreaming.* If any of these faculties occur in 
any of the lower vertebrata, I have not found evidence of 
the fact. 

To the next level I have assigned the Eodents and Carni- 
vora, with the exception of the dog. The most marked 
psychological distinction which I take to mark this level is 
the understanding of mechanisms. For, although I have 
found one instance of such understanding to occur in Birds,! 
and although it likewise unquestionably occurs in Eumi- 
nants,t in neither case does the understanding appear to 
extend further than to the simplest order of mechanisms, and 
therefore is only comparable in kind with the much greater 
aptitude in this respect which is shown by rats,§ foxes.|| 
cats,ir and the wolverine.** 

* Animal Intelligence, pp. 311-12. f Ihid., p. 316. J Ihid., pp. 338-9. 

§ Ibid., p. 361. II Ibid., pp. 428-31. % Ibid., pp. 420-22. 

** Ibid., pp. 348-50. — Sir James Paget has told me of a parrot which, by 
attentive study learned how to open a lock ; but although such cases may 
occasionally occur in birds, they are so comparatively rare that I have thought 
it best to place the faculty of appreciating simple mechanical appliances on 
the next level, for it is here only that we may first be sure that the actions 
are not due to mere association. A cat which jumps at a thumb-latch, and 
while holding on to the curved handle beneath with one fore-leg, depresses the 
thumb-piece with the other and pushes the door-posts with the hind-leg, 
clearly shows that she has an intelligent appreciation of the facts that the 
latch fastens the door, that when it is depressed the door will be liberated, 
and that when then pushed the door will open. And if it can still be sup- 
posed that all this knowledge can be obtained by simple association, there 
is the yet more remarkable case of the monkey described in Animal Intelli- 
gence, which by patient investigation discovered for himself, and without ever 
having observed any one perform a similar action, the mechanical principle 
of the screw, not to say also of the lever. 

It is remarkable, as I observed in Animal Intelligence, that this faculty 
of appreciating simple mechanical appliances does not seem always to stand 
in any very precise or quantitative relation to the general mental develop- 
ment of the species which exhibit it. Thus the dog is, as to his general in- 
telligence, unquestionably superior to the cat, and yet his ability in the 
particular we are considering is certainly not so high ; while bovine animals 
and horses seem to show more cleverness in this respect than in any other. 
Probably the explanation of this apparent disproportion in the development 
of the psychical faculties is to be found in the corporeal members which 
minister to them ; the monkey, which shows the highest power of appreciating 
mechanical appliances, is the animal which is best endowed with the organs 
of tactual examination ; the fore -paws of a cat are better instruments in this 
respect than those of the dog ; while the trunk of the elephant, the lips of 
the horse, and horns of ruminants give them in the same respects an advantage 
over most other mammals of a comparable grade of intelligence. 



352 MENTAL EVOLUTION IN ANIMALS. 

Next we arrive at Monkeys and the Elephant, which, with 
the exception of the Anthropoid Apes, are the only animals 
that, so far as I have been able to ascertain, make use of 
tools.* 

Lastly on level 28 we arrive at the highest development 
of the psychical powers which are to be met with in existing 
animals, and to this level I have assigned the Anthropoid 
Apes and Dogs. The meaning of the term " Indefinite 
Morality," which I give as distinctive of this grade of 
mental evolution, I shall explain in my next work, when I 
shall have to discuss the question touching the probable 
genesis of the moral sense. It is, I think, undesirable to 
divide this discussion, and therefore I prefer to postpone the 
consideration of this which I take to be the earliest phase in 
the development of the faculty of Conscience. And for the 
same reason I shall postpone my analysis of the lower stages 
of Abstraction and Volition, both of which are crossed by 
the level which we have now reached, where our enquiry 
into the Mental Evolution of Animals comes to an end. 

• Animal Intelligence, pp. 408-9 and 480-94i. 



THE END 



APPENDIX. 



A POSTHUMOUS ESSAY ON INSTINCT, 



BT 



CHARLES DAEWIN", M.A., LL.D., F.RS. 



APPENDIX. 



[Tlie full text of a part of Mr. Darwin's chapter on 
Instinct written for the " Origin of Species," but afterwards 
suppressed for the sake of condensation.] 



Migration. — The migration of young birds across broad 
tracts of the sea, and the migration of young salmon from 
fresh into salt water, and the return of both to their birth- 
places, have often been justly advanced as surprising in- 
stincts. With respect to the two main points which concern 
us, we have, firstly, in different breeds of birds a perfect 
series from those which occasionally or regularly shift their 
quarters within the same country to those which periodically 
pass to far distant countries, traversing, often by night, the 
open sea over spaces of from 240 to 300 miles, as from the 
north-eastern shores of Britain to Southern Scandinavia. 
Secondly, in regard to the variability of the migratory 
instinct, the very same species often migrates in one country 
and is stationary in another ; or different individuals of the 
same species in the same country are migratory or stationary, 
and these can sometimes be distinguished from one another 
by slight differences.* Dr. Andrew Smith has often re- 
marked to me how inveterate is the instinct of migration in 
some quadrupeds of S. Africa, notwithstanding the persecu- 
tion to which they are in consequence subjected : in N. 
America, however, persecution has driven the Buffalo within 



* Mr. Grould has observed this fact in Maltq,, and in Tasmania in the 
southern hemisphere. Bechstein {Stubenvogel, 1840, s. 293) says that in 
Germany the migratory and non-migratory Thrushes can be distinguished by 
the yellow tinge of the soles of their feet. The Quail is migratory in 
S. Africa, but stationary in Robin Island, only two leagues from the con' 
tinent {Le Vaillant's Travels, tOI. i, p. 105) : Dr. Andrew Smith confirms 
this. In Ireland the Quail has lately taken to remain in numbers to breed 
there (W, Thompson, Nat. Sist. of Ireland, vide " Birds," vol. ii, p. 70). 



356 MENTAL EVOLUTION IN ANIMALS. 

a late period* to cross in its migrations the Eocky Moun- 
tains ; and those " great highways, continuous for a hundred 
miles, always several inches, sometimes several feet in 
depth," worn by migrating buffaloes on the eastern plains, 
are never found westward of the Eocky Mountains. In the 
United States, swallows and other birds have largely ex- 
tended, within quite a late period, the range of their migra- 
tions.! 

The migratory instinct in Birds is occasionally lost ; as 
in the case of the "Woodcock, some of which have totally, 
without any assignable cause, taken to breed and become 
stationary in Scotland.} In Madeira the first arrival of the 
Woodcock is known,§ and it is not there migratory ; nor is 
our common Swift, though belonging to a group of birds 
almost emblematical of migration. A Brent Goose, which 
had been wounded, lived for nineteen years in confinement ; 
and for about the first twelve years, every spring at the 
migratory period it became uneasy, and would, like other 
confined individuals of the species, wander as far northwards 
as possible ; but after this period " it ceased to exhibit any 
particular feeling at this season. "|| So that we have seen 
the migratory impulse at last worn out. 

In the migration of animals, the instinct which impels 
them to proceed in a certain direction ought, I think, to be 
distinguished from the unknown means by which they can 
tell one direction from another, and by which, after starting, 
they are enabled to keep their course in a dark night over 
the open sea ; and likewise from the means — whether some 
instinctive association with changing temperature, or with 
want of food, &c. — which leads them to start at the proper 
period. In this., and other cases, the several parts of the 

* Col. Fremont, Ueport of Exploring Uxpedition, 1845, p. 144. 

+ See Dr. Baehman's excellent memoir on this subject in Sillimati's 
Philosopk. Journ., toI. 30, p. 81. 

t Mr. W. Thompson has given an excellent and full account of this 
■whole subject (see Nat. Hist, of Ireland, "Birds," vol. ii, pp. 247-57), where 
he discusses the cause. There seems reason to believe (p. 254) that the 
migratory and non-migratory individuals can be distinguished. For Scotland 
see St. John's Wild Sports of the Highlands, 1846, p. 220. 

§ Dr. Heincken in Zoological Journal, vol. v, p. 75. See also Mr. E. V. 
Harcourt's Sketch of Madeira, 1851, p. 120. 

II W. Thompson, loc. cit., vol. iii, p. 63. In Dr. Baehman's paper just 
referred to cases of Canada geese in confinement periodically trying to escape 
northward are given. 



AprENDix, 357 

problem have often been confused together under the word 
instinct.* "With respect to the period of starting, it cannot 
of course be memory in the young cuckoos' start for the first 
time two months after their parents have departed : yet it 
deserves notice that animals somehow acquire a surprisingly 
accurate idea of time. A. d'Orbigny shows that a lame 
hawk in S. America knew the period of three weeks, and 
used at this interval to visit monasteries when food was dis- 
tributed to the poor. Difficult though it may be to conceive 
how animals either intelligently or instinctively come to 
know a given period, yet we shall immediately see that in 
some cases our domestic animals have acquired an annual 
recurring impulse to travel, extremely like, if not identical 
with, a true migratory instinct, and which can hardly be due 
to mere memory. 

It is a true instinct which leads the Brent Goose to try to 
escape northwards ; but how the bird distinguishes north and 
south we know not. Nor do we know how a bird which 
starts in the night, as many do, to traverse the ocean, keeps 
its course as if provided with a compass. But we should be 
very cautious in attributing to migratory animals any 
capacity in this respect which we do not ourselves possess ;t 
though certainly in them carried to a wonderful perfection. 
To give one instance, the experienced navigator Wrangelf 
expatiates with astonishment on the " unerring instinct " of 
the natives of IST. Siberia, by which they guided him through 
an intricate labyrinth of hummocks of ice with incessant 
changes of direction ; while Wrangel " was watching the 
different turns compass in hand and trying to reason the 
true route, the native had always a perfect knowledge of it 
instinctively." Moreover, the power in migratory animals of 
keeping their course is not unerring, as may be inferred from 

* See E. P. Thompson on the Passions of Animals, 1851, p. 9; and 
Alison's remarks on this head in the Cyclopcedia of Anatomy and Physiology., 
article " Instinct," p. 23. 

t [I cannot refrain from drawing attention to the superiority of scientific 
method and philosophical caution here displayed as contrasted with Profe?sor 
Hseckel's views on the same subject, which in presence of this difficulty at once 
conclude in favour of some mysterious additional sense (see p. 95). — Gr. J. R.] 

X WrangeVs Travels, Eng. trans., p. 146. See also Sir Gr. Grey's Expe- 
dition to Australia, vol. ii, p. 72, for interesting account of the powers of 
the Australians in this same respect. The old French missionaries used to 
believe that the N. American Indians were actually guided by instinct in 
finding their way. 
16 



358 MENTAL EVOLUTION IN ANIMALS. 

the numbers of lost swallows often met with by ships in the 
Atlantic : the migratory salmon, also, often fails in returning 
to its own river, " many Tweed salmon being found in the 
Forth." But how a small and tender bird coming from 
Africa or Spain, after traversing the sea, finds the very same 
hedge-row in the middle of England, where it made its 
nest last season, is truly marvellous.* 

Let us now turn to our domesticated animals. Many 
cases are on record of animals finding their way home in a 
mysterious manner, and it is asserted that Highland slieep 
have actually swum over the Frith of Forth to their home a 
hundred miles distant ;t when bred for three or four genera- 
tions in the lowlands, they retain their restless disposition. I 
know of no reason to doubt the minute account given by 
Hogg of a family of sheep which had a hereditary 'propensity 
to return at the breeding season to a place ten miles off, 
whence the first of the lot had been brought ; and, after their 
lambs were old enough, they returned by themselves to the 
place where they usually lived ; so troublesome was this in- 
herited propensity, associated with the period of parturitionj 
that the owner was compelled to sell the lot.J Still more 
interesting is the account given by several authors of certain 
sheep in Spain, which from ancient times have annually 
migrated during May from one "narfc of the country to another 
distant four hundred miles : ai. the authors § agree that " as 
soon as April comes the sheep express, by curious uneasy 
motions, a strong desire to return to their summer habita- 



* The niimher of birds which by chance visit the Azores (Consul C. Hunt, 
in Journ. Geograph. Soc, toL xv, Pt. 2, p. 282), so distant from Europe, is 
probably in part due to lost directions during migi-ation : W. Thompson 
{Nat. Hist, of Ireland, " Birds," vol. ii, p. 172) shows that N. American birds, 
■which occasionally wander to Ireland, generally arrive at tlie period wlien 
they are migrating in N. America. In regard to Salmon, see Scope's Days 
of Salmon Fishing, p. 47. 

t Gardener's Chronicle, 1852, p. 798 : other cases are given by Youatt on 
Shsep, p. 377. 

X Quoted by Youatt in Veterinary Journal, vol. v, p. 282. 

§ Bourgoanne's Travels in Sjiain (Eng. trans.), 1789, vol. i, pp. 38-54. 
In Mills' Treatise on Cattle, 1776, p. 342, there is an extract of a letter from 
a gentleman in Spain from which I have made extract. Youatt on the Sheep, 
p. 153, givCs references to three other ^publications with similar accounts. I 
may add that von Tschudi {Sketches of Nature in the Alps, Eng. trans., 
185G, p. 160) states that annually in the spring the cattle are greatly excited, 
■when they hear the great bell which is carried with them ; well knowing that 
this is the signal for their " approaching migration " to the higher Alps. 



APPENDIX. 359 

tions." " The imquietude," says another author, " which they 
manifest might in case of need serve as an almanack." " The 
shepherds must then exert all their vigilance to prevent them 
escaping," " for it is a known truth that they would go to the 
very place where they had been born." Many cases have 
occurred of three or four sheep having started and performed 
the journey by themselves, though generally these wanderers 
are destroyed by the wolves. It is very doubtful whether 
these migratory sheep are aborigines of the country ; and it 
is certain that within a comparatively recent period their 
migrations have been widely extended : this being the case, I 
think there can hardly be a doubt that this " natural instinct," 
as one author calls it, to migrate at one particular season in 
one direction has been acquired during domestication, based 
no doubt on that passionate desire to return to their birth- 
place which, as we have seen, is common to many breeds of 
sheep. The whole case seems to me strictly parallel to the 
migrations of wild animals. 

Let us now consider how the more remarkable migrations 
could possibly have originated. Take the case of a bird being 
driven each year, by cold or want of food, slowly to travel 
northward, as is the case with some birds ; and in time we 
may well believe that this compulsory travelling would 
become an instinctive passion, as with the sheep in Spain. 
Now during the long course of ages, let valleys become con- 
verted into estuaries, and then into wider and wider arms of 
the sea ; and still I can well believe that the impulse which 
leads the pinioned goose to scramble northward would lead 
our bird over the trackless waters ; and that, by the aid of 
the unknown power by which many animals (and savage 
men) can retain a true course, it would safely cross the 
sea now covering the submerged path of its ancient land 
journey.* 

* I do not. suppose tliat the line of migration of birds always marts tlie 
line of formerly continuous land. It is possible that a bird accidentally 
blown to a distant land or island, after staying some time and breeding there, 
might be induced by its innate instinct to fly away, and again to return there 
in the breeding season. But I know of no facts to countenance the idea ; 
and I have been much struck in the case of oceanic islands, lying at no ex- 
cessive distance from the mainland, but which from reasons to be given in a 
future chapter I do not believe have ever been joined to the mainland, with 
the fact that they seem most rarely to have any migratory birds. Mr. E. V. 
Harcoiirt, who has written on the birds of Madeira, informs me that there 
are none in that island ; so, I am informed by Mr. Carew Hunt, it is in the 



360 MENTAL EVOLUTION IN ANIMALS. 

[I will give one case of migration which seemed to me at 
first to offer especial difficulty. It is asserted that in the 
extreme north of America, Elk and Reindeer annually cross, as 
if they could smell the herbage at the distance of a hundred 
miles, a tract of absolute desert, to visit certain islands where 
there is a better (but still scanty) supply of food. How 
could their migration have been first established ? If the 
climate formerly had been a little more favourable, the desert 
a hundred miles in width might then have been clothed with 
vegetation sufficient to have just tempted the quadrupeds 
over it, and so to have found out the more fertile northern 
islet. But the intense Glacial preceded our present climate, 
and therefore the idea of a former better climate seemed quite 
untenable ; but if those American geologists are right who 
believe, from the range of recent shells, that subsequently to 
the Glacial period there was one slightly warmer than the 
present period, then perhaps we have a key to the migration 
across the desert of the Elk and Eeindeer.*] 

Instinctive Fear. — I have already discussed the hereditary 
tameness of our domestic animals ; from what follows I have 
no doubt that the fear of man has always first to be acquired 
in a state of nature, and that under domestication it is merely 
lost. In all the few archipelagoes and islands inhabited by 
man, of which I have been able to find an early account, the 
native animals were entirely void of fear of man : I have 
ascertained this in six cases in the most distant parts of the 
world, and with birds and mammals of the most different 
kinds.f At the Galapagos Islands I pushed a hawk off a 

Azores, tlaougli lie thinks tliat perhaps the Quail, which migi-ates from 
island to island, may leave the Archipelago. [In pencil it is added " Canaries 
none." — G. J. K.] 

In the Falkland Islands, so far as I can find, no land-lird is migratory. 
From enquiries which I have made, I find there is no migratory bird in 
Mauritius or Bourbon. Colenso asserts (Tasmanian Journal, vol. ii, p. 227) 
that a cuckoo, C. hicidus, is migratory, remaining only three or four months 
in New Zealand; but New Zealand is so large an island that it may very 
easily migrate to the south and remain there quite unknown to the natives of 
the north. Faroe, situated about 180 miles from the north of Scotland, have 
6everal migratory birds (Graber, Tafjehuch, 183'), s. 205); Iceland seems to 
be tlie strongest exception to the general rule, but it lies only miles 

from the line of 100 fatlioms. [The last ten words are added 

in pencil with the blanks left for subsequent filling in. — Gr. J. R.] 

* [The paragraph which I have enclosed in square brackets is faintly 
struck out in pencil. — Gr. J. R.]. 

t I have given in my Journal of Researches (1845), p. 378, details on tha 
Falkland and Galap.igos. Mr. Cada Mosto (Kerr's Collection of Voyages, 



APPENDIX. 361 

tree with the muzzle of my gun, and the little hirds drank 
water out of a vessel which I held in my hand. But I have 
in my "Journal" given details on this subject, and I will 
here only remark that tlie tameness is not general, but special 
to\\'ards man ; for at the Falklands the geese build on the 
outlying islands on account of the foxes. These wolf-like 
foxes were here as fearless of man as were the birds, and the 
sailors in Byron's voyage, mistaking their curiosity for fierce- 
ness, ran into the water to avoid them. In all old civilized 
countries the wariness and fear of even young foxes and 
wolves are M^ell known.* At the Galapagos Islands the great 
land lizards (AmUyrhyncJius) were extremely tame, so that I 
could pull them by the tail; whereas in other parts of the 
world large lizards are wary enough. The aquatic lizard of 
the same genus lives on the coast, is adapted to swim and 
dive perfectly, and feeds on submerged algse : no doubt it 
must be exposed to danger from the sharks, and consequently, 
though quite tame on the land, I could not drive them into 
the water, and when I threw them in they always swam 
directly back to the shore. See what a contrast with all 
amphibious animals in Europe, which when disturbed by the 
most dangerous animal, man, instinctively and instantly take 
to the water. 

The tameness of the birds at the Falklands is particularly 
interesting, because most of the very same species, more espe- 
cially the larger birds, are excessively wild in Tierra del 
Fuego, where for generations they have been persecuted by 
the savages. Both at these islands and at the Galapagos it 
is particularly noteworthy, as I have shown in my " Journal" 
by the comparison of the several accounts up to the time 
when we visited these islands, that the birds are gradually 
getting less and less tame ; and it is surprising, considering 
the degree of persecution which they have occasionally suf- 

Tol. ii, p. 216) says that at the C. de Yerde Islands the pigeons Tvere so tame 
as readily to be caught. These, then, are the only large groups of islands, 
with the exception of the oceanic (of which I can find no early account) 
which were uninhabited when discovered. Thos. Herbert in 1626 in his 
Travels (p. 349) describes the tameness of the birds at Mauritius, and Du 
Bois in 1669 72 enters into details on this head with respect to all the birds 
at Bourbon. Capt. Moresby lent me a MS account of his survey of St. Pierre 
and Providence Islands, north of Madagascar, in which he describes the 
extreme tameness of the pigeons. Capt. Carmichael has described the tame- 
ness of the birds at Tristan d'Acunha. 
* Le Eoy, Lettres Fhilosojjh., p. 86. 



362 MENTAL EVOLUTION IN ANIMALS. 

fered during the last one or two centuries, that they have not 
become wilder; it shows that the fear of man is not soon 
acquired. 

In old inhabited countries, where the animals have 
acquired much general and instinctive suspicion and fear, 
they seem very soon to learn from each other, and perhaps 
even from other species, caution directed towards any par- 
ticular object. It is notorious that rats and mice cannot long 
be caught by the same sort of trap,* however tempting the 
bait may be ; yet, as it is rare that one which has actually 
been caught escapes, the others must have learnt the danger 
from seeing their companions suffer. Even the most terrific 
object, if never causing danger, and if not instinctively 
dreaded, is immediately viewed with indifference, as we see in 
our railway trains. What bird is so difficult to approach as 
the heron, and how many generations would it not require to 
make herons fearless of man ? Yet Mr. Thompson saysf that 
these birds, after a few days' experience, would fearlessly 
allow a train to pass within half gun-shot distance, j Altliough 
it cannot be doubted that the fear of man in old inhabited 
countries is partly acquired, yet it also certainly is instinc- 
tive ; for nesting birds are generally terrified at the first sight 
of mqn, and certainly far more so than most of the old birds 
at the Falklands and Galapagos Archipelago after years of 
persecution. 

We have in England excellent evidence of the fear of 
man being acquired and inherited in proportion to the danger 
incurred ; for, as was long ago remarked by the Hon. Daines 
Barrington,§ all our large, birds, young and old, are extremely 
wild. Yet there can be no relation between size and fear ; 

* E. P. Thompson, Passions of Animals, p. 29. 

t Nat. Hist, of Ireland, " Birds," vol. ii, p. 133. 

J [I may here refer to the corroboration which this statement has 
recently received in a correspondence between Dr. Eae and Mr. Goodsir 
(Nature, July 3rd, 12th, and 19th, 1883). The former says that the wild 
duck, teal, &c., which frequent certain districts through which the Pacific 
Railway has been carried in Canada, became quite fearless of the trains the 
first few days after traffic was opened, and the latter gives similar testimony 
concerning the wild fowl of Australia, adding, " The constant roar of a 
great passing traffic, as well as the unceasing turmoil and unearthly noises of 
a large railway station within a stone's throw of their haunts, is now quite 
unnoticed by these usually most watchful and wary of all birds, [i.e., wild 
ducks.] But for fear of trespassing on your space, I could give many more 
illustrations of the truth of Dr. Rae's remarks." — Or. J. R.j 

§ Fhil. Trans., 1773, p. 264. 



APPENDIX. 363 

for on unfrequented islands, when first visited, the large 
birds were as tame as the small. How exceedingly wary is 
our magpie ; yet it fears not horses or cows, and sometimes 
alights on their backs, just like the doves at the Galapagos 
did in 1684 on Cowley. In Norway, where the magpie is 
not persecuted, it picks up food " close about the doors, 
sometimes walking inside the houses."* The hooded crow 
(C comix), again, is one of our wildest birds ; yet in Egyptf 
is perfectly tame. Every single young magpie and crow 
cannot have been frightened in England, and yet all are 
fearful of man in the extreme: on the other hand, in the 
Falkland and Galapagos Islands many old birds, and their 
parents before them, must have been frightened and seen 
others killed ; yet they have not acquired a salutary dread of 
the most destructive animal, man.J 

Animals feigning, as it is said. Death — an unknown state 
to each living creature — seemed to me a remarkable instinct. 
I agree with those authors§ who think that there has been ' 
much exaggeration on this subject : I do not doubt that 
fainting (I have had a Eobin faint in my hands) and the 
paralyzing effects of excessive fear have sometimes been mis- 
taken for the simulation of death.(| Insects are most notori- 

* Mr. C. Hewitson in Magazine of Zoology and Botany, vol. ii, p. 311. 

t Geofiry St. Hilaire, Anns, des Mus., tome ix, p. 471. 

j [I have already pointed otit the refined degree to which such instinctive 
dread of man is developed -when it is able accurately to discriminate what 
constitutes safe distance from fire-arms. Since writing the passage to which 
I allude (see p. 197), I have met with the following observation in the letters 
recently published by Dr. Eae in Nature, which is of interest as showing how 
rapidly such refinement of discrimination is attained: — " I may perhaps be 
permitted to give one of many instances known to me of the quickness of 
birds in acquiring a knowledge of danger. Golden plover, when coming from 
their breeding-places in high latitudes, visit the islands north of Scotland in 
large numbers, and keep together in great packs. At first they are easily 
approached, but after a very few shots being fired at them, they become not 
only much more shy, but seem to measure with great acciiracy the distance 
at which they are safe from harm." — G. J. K..] 

§ Couch, Illustrations of Instinct, p. 201. 

II The most curious case of apparently true simulation of death is that 
given by Wrangel {Travels in Siberia, p. 312, Eng. trans.) of the geese which 
niigrate to the Tundras to moult, and are then quite incapable of flight. He 
says they feigned death so well " with their legs and necks stretched out 
quite stiff, that I passed them by, thinking they were dead." But the natives 
were not thus taken in. This simulation would not save them from foxes or 
wolves, &c., which I presume inhabit the Tundras : would it save them from 
hawks ? The case seems a strange one. A lizard in Patagonia {Journal of 
Researches, p. 97), which lives on the sand near the coast, and is speckled 
like it, when frightened feigned death with outstretched legs, depressed body, 



36^ MENTAL EVOLUTION IN ANIMALS. 

Oils in this respect. We have amongst them a most perfect 
series, even within the same genus (as I have observed in 
Curculio and Clnysomela), from species which feign only for 
a second and sometimes imperfectly, still moving their 
antennse (as with some Histers), and which will not feign a 
second time however much irritated, to other species which, 
according to De Geer, may be cruelly roasted at a slow fire, 
without the slightest movement — to others, again, which will 
long remain motionless as much as twenty-three minutes, as I 
find with Chrysomela spartii. Some individuals of the same 
species of Ptinus assumed a different position from that of 
others. Now it will not be disputed that the manner and dura- 
tion of the feint is useful to each species, according to the kind 
of danger which it has to escape ; therefore there is no more 
real difficulty in its acquirement, through natural selection, 
of this hereditary attitude than of any other. Nevertheless, 
it struck me as a strange coincidence that the insects should 
thus have come to exactly simulate the state which they took 
when dead. Hence I carefully noted the simulated positions 
of seventeen different kinds of insects (including an lulus. 
Spider, and Oniscus) belonging to the most distinct genera, 
both poor and first-rate shammers ; afterwards I procured 
naturally dead specimens of some of these insects, others I 
killed with camphor by an easy slow death ; the result was 
that in no one instance was the attitude exactly the same, 
and in several instances the attitude of the feigners and of 
the really dead were as unlike as they possibly could be. 

Nidification and Habitation. — We come now to more 
complex instincts. The nests of Birds have been carefully 
attended to, at least in Europe and the United States ; so 
that we have a good and rare opportunity of seeing whether 
there is any variation in an important instinct, and we shall 
find that this is the case. We shall further find that favour- 
able opportunities and intelligence sometimes slightly modify 
the constructive instinct. In the nests of birds, also, we 
have an unusually perfect series, from those which build 
none, but lay on the bare ground, to others which make a 
most imperfect and simple nest, to others more perfect, and 

and closed eyes ; if further disturbed, it buried itself quickly in the sand. If 
the Hare had been a small insignificant animal, and if she had closed her eyes 
when on her form, should we not perhaps have said that she was feigning 
death? In regard to Insects, see Kirby and Spence, Introduction to Ento- 
molof/y, vol. ii, p. 234. 



APPENDIX. 3G5 

SO on, till we arrive at marvellous structures, rivalling the 
weavers' art. 

Even in so singular a nest as that of the Hirundo {Col- 
localia esculcnfa), eaten by the Chinese, we can, I think, trace 
the stages by which the necessary instinct has been acquired. 
The nest is composed of a brittle white translucent substance, 
very like pure gum arable, or even glass, lined with adherent 
feather-down. The nest of an allied species in the British 
Museum consists of irregularly reticulated fibres, some as 
fine as * of the same substance ; in another species 

bits of sea-weed are agglutinated together with a similar 
substance. This dry mucilaginous matter soon absorbs 
water and softens : examined under the microscope it 
exhibits no structure, except traces of lamination, and very 
generally pear-shaped bubbles of various sizes ; these, indeed, 
are very conspicuous in small dry fragments, and some bits 
looked almost like vesicular lava. A small pure piece put 
into flame crackles, swells, does not readily burn, and smells 
strongly of animal matter. The genus CoUocalia, according 
to Mr. G. E. Gray, to whom I am much obliged for allowing 
me to examine all the specimens in the British Museum, 
ranks in the same sub-family with our common Swift. The 
latter bird generally seizes on the nest of a sparrow, but Mr. 
Macgillivray has carefully described two nests in which 
the confusedly fitted materials were agglutinated together 
by extremely thin shreds of a substance which crackles 
but does not readily burn when put into a flame. In 
]^. Americaf another species of Swift causes its nest to 
adhere against the vertical wall of a chimney, and builds it 
of small sticks placed parallel and agglutinated together 

* [In the MS a blank is liere intentionally left for tlie subsequent filling 
in of an appropriate word. — G. J. K.] 

t For Cypselus murarius see Macgillivray, British Birds, vol. iii, 1840, 
p. 625. For C. pelasgiiis, see Mr. Peabody's excellent paper on the Birds or 
Massachussetts in the Boston Journal of Nat. Sist., vol. iii, p. 187. M. E. 
Bobert {Comptes Rendus, quoted in Anns, and Mag. of Nat. Hist., vol. viii, 
18 J 2, p. 476) found that the nests of the Hirundo riparia, made in the 
gravelly banks of the Volga, had their upper surfaces plastered with a yellow 
animal substance, which he imagined to be fishes' spavra. Could he have 
mistaken the species, for there is no reason to suppose our bank-martin has 
any such habit? This would be a very remarkable variation of instinct, if it 
could be proved ; and the more remarkable that this bird belongs to a dif- 
ferent sub-family from the Swifts and CoUocalia. Yet I am inclined to 
believe it, for it has been affirmed with apparent truth that the House-martin 
moistens the mud, with which it builds its nest, with adhesive saliva. 



366 MENTAL EVOLUTION IN ANIMALS. 

with cakes of a brittle mucilage which, like that of the 
esculent swallow, swells and softens in water ; in flame it 
crackles, swells, does not readily burn, and emits a strong 
animal odour : it differs only in being yellowish-brown, in not 
having so many large air-bubbles, in being more plainly 
laminated, and in having even a striated appearance, caused 
by innumerable elliptical excessively minute points, which I 
believe to be drawn-out minute air-bubbles. 

Most authors believe that the nest of the esculent swallow 
is formed of either a Fucus or of the roe of a fish ; others, I 
believe, have suspected that it is formed of a secretion from 
the salivary glands of the bird. The latter view I cannot 
doubt, from the preceding observations, is the correct one. 
The inland habits of the Swifts and the manner in which the 
substance behaves in flame almost disposes of the supposition 
of Fucus. Nor can I believe, after having examined the 
dried roe of fishes, that we should find no trace of cellular 
matter in the nests, had they been thus formed. How could 
our Swifts, the habits of which are so well known, obtain roe 
without being detected? Mr. Macgillivray has shown that 
the salivary crypts of the Swifts are largely developed, and 
he believes that the substance with which the materials of its 
nest are fitted together, is secreted by their glands. I cannot 
doubt that this is the origin of the similar and more copious 
substance in the nest of the North American Swift, and in 
those of the Collocalia esculenfa. We can thus understand 
its vesicular and laminated structure, and the curious reti- 
culated structure of the Philippian Island species. The only 
change required in the instinct of these several birds is that 
less and less foreign materials should be used. Hence I con- 
clude that the Chinese make soup of dried saliva.* 

In looking for a perfect series in the less common forms 
of birds' nests, we should never forget that all existing birds 
must be almost infinitely few compared with those which 
have existed since footprints were impressed on the beach of 
the New Red Sandstone formation of North America. 

If it be admitted that the nest of each bird, wherever 
placed and however constructed, be good for that species 

* [Ifc is almost needless to observe tliat we must remember the date at 
which this was written; but it may be remarked that as early as 1817 it was 
pointed out by Homo {Phil. Trans., p. 332) tliat the proventriculus of Collo- 
calia is a peculiar glandular structure probably suited to secrete the substance 
of which the nest consists. — G. J. R.] 



APPENDIX. 367 

under its own conditions of life ; and if the nesting-instinct 
varies ever so little, when a bird is placed under new con- 
ditions, and the variations can be inherited, of which there 
can be little doubt — then natural selection in the course of 
ages might modify and perfect almost to any degree the nest 
of a bird in comparison with that of its progenitors in long 
past ages. Let me take one of the most extraordinary cases 
on record, and see how selection may possibly have acted ; I 
refer to Mr. Gould's observation* on the Australian Mega- 
podidfe. The Talegcdla lathami scrapes together a great 
pyramid, from two to four cart-loads in amount, of decaying 
vegetable matter ; and in the middle it deposit its eggs. The 
eggs are hatched by the fermenting mass, the heat of which 
was estimated at 90° F., and the young birds scratch their 
way out of the mound. The accumulation propensity is so 
strong that a single unmated cock confined in Sydney annually 
collected an immense mass of vegetable matter. The Leipoa 
ocellata makes a pile forty-five feet in circumference and four 
feet in height, of leaves thickly covered with sand, and in 
the same way leaves its eggs to be hatched by the heat of 
fermentation. The Megapodius tumulus in the northern 
parts of Australia makes even a much larger mound, but 
apparently including less vegetable matter ; and other species 
in the Malayan Archipelago are said to place their eggs in 
holes in the ground, where they are hatched by the heat of 
the sun alone. It is not so surprising that these birds should 
have lost the instinct of incubation, when the proper tem- 
perature is supplied either from fermentation or the sun, as 
that they should have been led to pile up beforehand a great 
heap of vegetable matter in order that it might ferment ; 
for, however the fact may be explained, it is known that 
other birds will leave their eggs when the heat is sufficient 
for incubation, as in the case of the Fly-catcher which built 
its nest in Mr. Knight's hot-house.t Even the snake takes 
advantage of a hot-bed in which to lay its eggs ; and what 
concerns us more, is that a common hen, according to Pro- 
fessor Fischer, " made use of the artificial heat of a hot-bed to 
hatch her eggs." J Again Eeaumur, as well as Bonnet, 

* Birds of Australia, and Introduction to the Birds of Australia, 1848, 
p. 82. 

t YarreVs British Birds, vol. i, p. 166. 

X Alison, article " Instinct " in Todd's Cyclop, of Anat, and Physiol., 
p. 21. 



368 MENTAL EVOLUTION IN ANIMALS. 

observed* that ants ceased their laborious task of daily- 
moving their eggs to and from the surface according to the 
heat of the sun, when they had built their nest between the 
two cases of a bee-hive, where a proper and equable tempe- 
rature was provided. 

Now let us suppose that the conditions of life favoured 
the extension of a bird of this family, whose eggs were 
hatched by the solar rays alone, into a cooler, damper, and 
more wooded country : then those individuals which chanced to 
have the accumulative propensity so far modified as to prefer 
more leaves and less sand, would be favoured in their exten- 
sion ; for they would accumulate more vegetable matter, and 
its fermentation would compensate for the loss of solar heat, 
and thus more young birds would be hatched which might as 
readily inherit the peculiar accumulative propensity of their 
parents as our breeds of dogs inherit a tendency to retrieve, 
another to point, and another to dash round its prey. And 
this process of natural selection might be continued, till the 
eggs came to be hatched exclusively by the heat of fermen- 
tation ; the bird, of course, being as ignorant of the cause of 
the heat as of that of its own body. 

In the case of corporeal structures, when two closely 
allied species, one for instance semi-aquatic and the other 
terrestrial, are modified for their different manners of life, 
their main and general agreement of structure is due, according 
to our theory, to descent from common parents ; and their 
slight differences to subsequent modification through natural 
selection. So when we hear that the thrush of South America 
{T. Falklandicus), like our European species, lines her nest in 
the same peculiar way with mud, though, from being sur- 
rounded by wholly different plants and animals, she must be 
placed under somewhat different conditions ; or when we 
hear that in North America the males of the kitty wrens,t 
like the male of our species, have the strange and anomalous 
habit of making " cock-nests," not lined Avith feathers, in 
which to shelter themselves ; — when we hear of such cases, 
and they are sufficiently numerous in all classes of animals, 
we must attribute the similarity of the instinct to inheritance 
from common progenitors, and the dissimilarity, either to 

* Kirby and Spenco, Inlroi. to ISiitomol., vol. ii, p. 519. 
t Pea-body in Boston Journ. Nat. Hist., vol. iii, p. 114. For our British, 
species sec Macgillivray, Brit. Birds, vol. iii, p. 26. 



APPENDIX. 3G9 

selected and profitable modification, or to acquired and 
inherited habit. In the same manner, as the northern and 
southern thrushes have largely inherited their instinctive 
modification from a common parent, so no doubt the thrush 
and blackbird have likewise inherited much from their 
coniTnon progenitor, but with somewhat more considerable 
modifications of instinct in one or both species, from that of 
their ancient and unknown ancestor. 

We will noTT consider the variability of the nesting-instinct. The cases, 
no doubt, would have been far more numerous, had the subject been attended 
to in other countries with the same care as in Great Britain and the United 
States. From the general imiformity of the nests of each species, we clearly 
see that even trifling details, such as the materials used and the situation 
chosen on a high or low branch, on a bank or on level ground, whether 
Bohtary or in communities, are not due to chance, or to intelligence, but to 
instinct. The Syhria stjlvicola, for instance, can be distinguished from two 
closely allied wrens more readily by its nest being lined with feathers than by 
almost any other character. (" Yarrell's British Birds.") 

Necessity or compulsion often leads birds to change the situation of their 
nests : numerous instances conld be given in various parts of the world of 
birds breeding in trees, but in treeless countries on the ground, or amoniisfc 
rocks. Audubon (quoted in *' Boston Journ. Nat. Hist.," vol. iv, p. 249) 
states that the Gulls on an islet off Labrador, " in consequence of the perse- 
cution which they have met with, now build in trees," instead of in the rocks. 
Mr. Couch (" Illustrations of Instinct," p. 218) states that three or four 
successive layings of the sparrow (F. domesticus) having been destroyed, 
" the whole colony, as if by mutual agreement, quitted the place and settled 
themselves amongst some trees at a distance — a situation which, though 
common in some districts, neither they nor their ancestors had ever before 
occupied here, where their nests became objects of cviriosity." The sparrow 
builds in holes in walls, on high branches, in ivy, under rooks' nests, in the 
holes made by the sand-martins, and often seizes on the nest made by the 
house-martin : " tlie nest also varies gi'eatly according to the place " (Mon- 
tagiie, "Ornitho. Diet.," p. 4&2). The Heron (Macgillivray, " Brit. Birds," 
vol. iv, p. 446 : W. Thompson, " Nat. Hist. Ireland," vol. ii, p. 146) builds 
in trees, on precipitous sea-cliffs, and amongst heath on the ground. In the 
United States the Ardea kerodias (Peabody in "Boston Journal Nat. Hist.," 
vol. iii, p. 209) likewise builds in tall or low trees, or on the ground ; and, 
which is more remarkable, sometimes in communities or heionries, and 
sometimes solitarily. 

Convenience comes into play : we have seen that the Taylor-bird in 
India uses artificial thread instead of weaving it. A wild Gold-finch 
(Bolton's Harmonia Ruralis, vol. i, p. 492) first took wool, then cotton, 
and then down, which was placed near its nest. The common Eobin 
will often build under sheds, four cases having been observed in one season 
at one place (W. Thompson, "Nat. Hist. Ireland," vol. i, p. 14). In Wales 
the Martin {H. urhica) builds against perpendicidar cliffs, but all over the 
lowlands of England against houses ; and this must have prodigiously in- 
creased its range and numbers. In Arctic America in 1325 Hlrundo liini- 
frons (Richardson, " Fauna Boreali-Amercani,"p. 331) for the first time built 
against houses ; and the nests, instead of being clustered and each having a 
tubular entrance, were built under the eaves in a single line and without the 



370 MENTAL EVOLUTION IN ANIMALS. 

tubular entrance, or witli a mere ledge. The date of a similar cliange in the 
habits of H.ftdva is also known. 

In all changes, whether from persecution or convenience, intelligence 
must come into play in some degree. The Kitty-wren (T. rtdgaris), which 
builds in various situations, usually mates its nest to match with surrounding 
ohjects ( Macgillivray, vol. iii, p 21) ; but this perhaps is instinct. Yet 
wlien we hear irom White (Letter ]4) that a Willow-wren (and I have known 
a similar case), having been disturbed by being watched, concealed the orifice 
of her nest, we might argue that tlie case was one of intelligence. Neither 
the Kitty-wren nor Water-ouzel (" Mag. of Zool.," vol. ii, 1838, p. 429) 
invariably build domes to their nests, when placed in sheltered situations. 
Jesse describes a Jackdaw which built its nest on an inclined surface in a 
turret, and reared up a perpendicular stack of sticks ten feet in height — a 
labour of seventeen days : families of this bii'd, I may add (White's " Sel- 
borne," Letter 21), have been known regulnrly to build in rabbit-burrows. 
Numerous analogous facts could be given. The Water-hen (G. chloropus) is 
said occasionally to cover her eggs when she leaves her nest, but in one pro- 
tected place W. Thompson (" Nat. Hist. Ireland," vol. ii, p. 328) says that 
this was never done. Water-hens and Swans, which build in or near the 
water, will instinctively raise their nest as soon as they perceive the water 
begin to rise (Couch " Illustrations of Instinct," p. 223-6). But the follow- 
ing seems a more curious case : — Mr. Yarrell showed me a sketch of the nest 
of a Black Australian Swan, which had been built directly under the drip of 
the eaves of a building ; and, to avoid this, male and female conjointly added 
semicircular * to the nest, until it extended close to the wall, 

within the line of drip ; and then they pushed tlie eggs into the newly added 
portion, so as to be quite dry. The Magpie {Corvus pica) under ordinary 
circumstances builds a remarkable, but very uniform nest ; in Norway they 
build in churches, or spouts under the eaves of houses, as well as in trees. 
In a treeless part of Scutland, a pair built for several years in a gooseberry 
bush, which they barricaded all round in an extraordinary manner with 
briars and thorns, so that " it would have cost a fox some days' labour to 
have got in." On the other hand, in a part of Ireland, Avhere a reward had 
been offered for each egg and the magpies had been much persecuted, a pair 
built at the bottom of a low thick hedge, "without any large collection of 
materials likely to attract notice." In Cornwall, Mr. Couch says he has 
seen near each other, two nests, one in a hedge not a yard from the ground 
and " unusually fenced in with a thick structure of thorns ;" the other " on 
the top of a very slender and solitary elm — the expectation clearly being 
that no creature would venture to climb so fragile a column." I have been 
struck by the slenderness of the trees sometimes chosen by the magpie ; but, 
intelligent as this bird is, I cannot believe that it foresees that boys could not 
climb such trees, but rather that, having chosen such a tree, it has found 
from experience that it is a safe place. f 

Altliough I do not doubt that intelligence and expei-ience often come 
into ]ilay in the nidification of Birds, yet both often fail : a Jackdaw has 
been seen trying in vain to get a stick through a turret window, and had 

* [A word is here accidentally omitted in the MS. — G-. J. K.] 

t l*'or Norway, see in Mag. of Zool. and Bot., 1838, vol. ii, p. 311. For 

Scotland, Kev. J. Hall, Trax^els in Scotland, see Art. " Instinct" in Cyclop. 

of Anat. and Physiol., p. 22. For Ireland, W. Thompson, Nat. Hist, of 

Ireland, vol. ii, p. 320. For Cornwall, see Couch, Illustrations of Instinct, 

p. 213, 



APPENDIX. 871 

not sense to draw it in lengthways : Wliite (Letter 6) describes some mar- 
tins wJiich year after year built their nests on an exposed wall, and year after 
year tbey were washed down. The Furnarius cunicularius in S. America 
makes a deep burrow in mud-banks for its nest ; and I saw (" Journal of 
Researches," p. 216) these little birds vainly burrowing numerous holes 
through mud-walls, over which they were constantly flitting, without thus 
perceiving that the walls were not nearly thick enough for tlieir nests. 

Many variations cannot in any way be accounted for : tlie Totanus macu- 
larius (Peabody, " Boston Journ. Nat. Hist.," vol. iii, p. 219) lays her eggs 
sometimes on the bare ground, sometimes in nests slightly made of grass. 
Mr. Blackwall has recorded the curious case of a yellow Bunting {Enibe- 
riza citrinella) given in " Yarrell's British Birds," which laid its eggs and 
hatched them on the bare gi-ound : this bird generally builds on or very close 
to the ground, but a case is recorded of its having built at a height of seven 
feet. A nest of a ChafTinch {FringiUa ccelebs ; " Annals and Mng, of Nat. 
History," vol. viii, 1842, p. 281) has been described, which was bound by a 
piece of whipcord passing once round a branch of a pine tree, and then 
firmly interwoven with the materials of the nest : the nest of the chaffinch 
can almost be recognized by the elegant manner with which it is coated 
with lichen ; but Mr. Hewitson (" British Oology," p. 7) has described one 
in which bits of paper were used for lichen. The Thrush {T. musicus) 
builds in bushes, but sometimes, when bushes abound, in holes of walls or 
under sheds ; and two cases are known of its having built actually on the 
ground in long grass and under turnip-leaves (W. Thompson, " Nat. Hist. 
of Ireland," vol. i, p. 136: Couch, "Illustrations of Instinct," p. 219). The 
Eev. W. D. Fox informs me that an " eccentric pair of blackbirds " 
{T. mervla) for three consecutive years built in ivy against a wall, and 
always lined their nest with black horse-hair, though there was nothing to 
tempt them to use this material : the eggs also were not spotted. The 
same excellent observer has described (in " Hewitson's British Oology ") the 
nests of two Redstarts, of which one alone was lined with a profusion of 
white feathers. The Golden-crested Wren (Mr. Sheppard in " Linn. Trans.," 
vol. XV, p. 14) usually builds an open nest attached to the under side of a 
fir-branch, but sometimes on the branch, and Mr. Sheppard has seen one 
" pendulous with a hole on one side." Of the wonderful nest of the Indian 
Weaver-bird {Ploceus PhiUppensis, " Proc. Zool. Soc," July 27, 1852), about 
one or two in every fifty have an upper chamber, in whicli the males nest, 
grooved by the widening of the stem of the nest with a pent-house added 
to it. I will conclude by adding two general remarks on this head by two 
good observers (Sheppard in " Linn. Trans.," vol. xv, p. 14, and Blackwall 
quoted by Yarrell, "British Birds," vol. i, .p. 444). "There are few birds 
which do not occasionally vary from the general form in building their 
nests." " It is evident," says Mr. Blackwall, " that birds of the same species 
possess the constructive powers in very different degrees of perfection, for the 
nests of some individuals are finished in a manner greatly superior to those 
of others." 

Some of the cases above given, such as the Totanus either making a nest 
or building on the bare ground, or that of the Water-ouzel making or not 
making a dome to its nest, ought, perhaps, to be called a double instinct 
rather than a variation. But the most curious case of a double instinct which 
I have met with, is that of the Si/hna cisticola given by Dr. P. Savi (" Anns, 
des Sc. Nat.," tome ii, p. 126). This bird in Pisa annually makes two nests ; 
the autumnal nest is formed by leaves being sewn together with spiders' webs 
and the down of plants, and is placed in marshes ; the vernal nest is placed 
in tufts of grass in corn-fields, and the leaves are not sewn together ; but the 



372 MENTAL EVOLUTION IN ANIMALS. 

sides are tliicker and xerj different materials are used. In sueli cases, as wag 
formerly remarked witii respect to corporeal structures, a great and apparently 
abrupt change might be effected in the instinct of a bird by one form alone 
of tlie nest behig retained. 

In some cases, -n-ben the same species ranges into a different climate, the 
nest differs ; the Artamtis sordidus in Tasmania builds a larger, more com- 
pact, and neater nest, than in Australia (Govild's "Birds of Australia"), 
The Sterna minuta, accoi'ding to Audubon (''Anns, of Nat. Hist.," toI. ii, 
1839, p. 462), in the southern and middle 'U. States merely scoops a slight 
hollow in the sand ; " but on the coast of Labrador it makes a very snug nest, 
formed of di'y moss, well matted together and nearly as large as that of the 
Turdus migratorius." Those individuals of Icterus Baltimore (Peabody in 
"Boston Journ. of Nat. Hist.," vol. iii, p. 97) "which buUd in the south 
make their nests of light moss, which allows the air to pass through, and 
complete it without lining ; while in the cool climate of New England they 
make their nests of soft substances closely woven with a warm lining." 

Habitations of Mammals. — On this head I shall make but 
few remarks, having said so much on the nests of Birds. 
The buildings erected by the Beaver have long been cele- 
brated ; but we see one step by which its wonderful instincts 
might have been perfected, in the simpler house of an allied 
animal, the Musk Eat {Fiber zibethicus) which, however, 
Hearne* says is something like that of the Beaver. The 
solitary Beavers of Europe do not practise, or have lost the 
greater part of their constructive instincts. Certain species 
of Eats now uniformly inhabit the roofs of houses,t but other 
species keep to hollow trees — a change analogous to that in 
swallows. Dr. Andrew Smith informs me that in the unin- 
habited parts of S. Africa the hysenas do not live in burrows, 
whilst in the inhabited and disturbed parts they do.| Several 
mammals and birds usually inhabit burrows made by other 
species, but when such do not exist, they excavate their own 
habitations. § 

In the genus Osmia, one of the Bee family, the several 
species not only offer the most remarkable differences, as 
described by Mr. F. Smith|| in their instincts ; but the indi- 
viduals of the same species vary to an unusual degree in this 
respect ; thus illustrating the rule, which certainly seems to 

* Hearne's Travels, p. 380. Hearne has given the best description (pp. 
227-236) ever published of the habits of the Beaver. 

t Rev. L. Jenyns in Linn. Trans., vol. xvi, p. 166. 

X A case sometimes quoted of Hai'cs having made burrows in an exposed 
situation {Anns, of Nat. Hist., vol. v, p. 362), seems to me to require verifica- 
tion : were not the old rabbit-burrows used ? 

§ Zoology of the Vogage of the Beagle, "Mammalia," p. 90, 

II Catalogue of British Uymenoptera, 1855, p. 158. 



APPENDIX. 373 

bold in corporeal structures, namely, that the parts which 
diifer most in allied species, are apt also to vary most in the 
same species. Another Bee, the Mcgachile maritima, as I am 
informed by Mr. Smith, near the sea makes its burrows in the 
sand-banks, whilst in wooded districts it bores holes in posts.* 

I have now discussed several of the most extraordinary 
classes of instincts ; but I have still a few miscellaneous 
remarks which seem to me worth making. First for a few 
cases of variation which have struck me : a spider which had 
been crippled and could not spin its web, changed its habits 
from compulsion into hunting — which is the regular habit of 
one large group of spiders.f Some insects have two very 
different instincts under different circumstances, or at different 
times of life ; and one of the two might through natural selec- 
tion be retained, and so cause an apparently abrupt difference 
in instinct in relation to the insects' nearest allies : thus the 
larva of a beetle (the Cionus scrophularicc), when bred on the 
scrophularia, exudes a viscid substance, which makes a trans- 
parent bladder, within which it undergoes its metamorphosis ; 
but the larva when naturally bred, or transported by man, on 
to a verbasciim, becomes a burrower, and undergoes its meta- 
morphosis within a leaf.;j: In the caterpillars of certain moths 
there are two great classes, those which burrow in the paren- 
chyma of leaves, and those which roll up leaves with consum- 
mate skill : some few caterpillars in their early age are 
burrowers, and then become leaf -rollers ; and this change was 
justly considered so great, that it was only lately discovered 
that the caterpillars belonged to the same species. § The 
Angoumois moth usually has two broods: the first are 
hatched in the spring from eggs laid in the autumn on grains 
of corn stored in granaries, and then immediately take flight 
to the fields and lay their eggs on the standing corn, instead 
of on the naked grains stored all round them : the moths of 
the second brood (produced from the eggs laid on the standing 
corn) are hatched in the granaries, and then do not leave the 
granaries, but deposit their eggs on the grains around them ; 
and from these eggs proceed the vernal brood which have the 

* [Here follows a section on the instincts of Parasitism, Slave-making, and 
Cell-making, which is published in the Origin of Species. — Gr. J. li.J 
+ Quoted on authority of Sir J. Banks in Journal Linn. Soc. 
% P. Huber in Mem. Soc, Fhi/s. de Geneve, tome x, p. 33. 
§ Westwood, in Gardeners' Chronicle, 1852, p. 261. 



374 MENTAL EVOLUTION IN ANIMALS. 

different instinct of laying on the standing corn.* Some hunt- 
ing spiders, when they have eggs and young, give up hunting 
and spin a web wherewith to catch prey : this is the case 
with a Salticus, which lays its eggs within snail-shells, and at 
that time spins a large vertical web.f The pupae of a species 
of Formica are somctimesX uncovered, or not enclosed within 
cocoons ; this certainly is a highly remarkable variation ; the 
same thing is said to occur with the common Pulex. Lord 
Brougham § gives us a remarkable case of instinct, namely, tho 
chicken within the shell pecking a hole and then " chipping 
with its bill-scale till it has cut off a segment from the shell. 
It always moves from right to left, and it always cuts off the 
segment from the big end," But the instinct is not quite so 
invariable, for I was assured at the Eccalobeion (May, 1840) 
that cases have occurred of chickens having commenced so 
close to the broad end, that they could not escape from the 
hole thus made, and had consequently to commence chipping 
again so as to remove another and larger rim of shell : more- 
over occasionally they have begun at the narrow end of the 
sliell. The fact of the occasional regurgitation of its food by 
the Kangaroo! ought, perhaps, to be considered as due to an 
intermediate or variable modification of structure, rather 
than of instinct; but it is worth notice. It is notorious 
that the same species of Bird has slightly different vocal 
powers in different districts ; and an excellent observer 
remarks that " an Irish covey of Partridges springs without 
uttering a call, whilst on the opposite coast the Scotch covey 
shrieks with all its might when sprung."ir Bechstein says 
that from many years' experience he is certain that in the 
nightingale a tendency to sing in the middle of the night or 
in the day runs in families and is strictly inherited.** It is 
remarkable that many birds have the capacity of piping long 
and difficult tunes, and others, as the Magpie, of imitating 



* Bonnet, quoted by Kirby and Spence, 'Entomology, vol. ii, p. 480. 

t l^uges in Anns, des Sci. Nat., 2nd series, tome vi, p. 196. 

X F. Smith in Trann. Eiit. Soc, vol. iii, N.S., Pt. iii, p. 97 j and De Greer, 
qixoted by Kirby and Spenee, Entomologii, vol. iii, p. 227. 

§ Dissertation on Natural Theologi/, vol. i, p. 117. 

II W. C. Martin in Mag. of Nat. Hist., N.S., vol. ii, p. 323. 

•\[ W. Thompson, in Nat. Hist. Ireland, vol. ii, p. t)5, says that he has 
observed this, and that it is well known to sportsmen. 

** Stuben-vogel, 1840, s. 323. See on different powers of singing in 
different places, s. 205 and 265. 



APPENDIX. S75 

all sorts of sounds, and yet that in a state of nature they 
never display these powers.* 

As there is often much difficulty in imagining how an 
instinct could first have arisen, it may be worth while to give 
a few, out of many cases, of occasional and curious habits, 
which cannot be considered as regular instincts, but which 
might, according to our views, give rise to such. Thus, 
several cases are on recordf of insects which naturally have 
very different habits having been hatched within the bodies 
of men — a most remarkable fact considering the temperature 
to which they have been exposed, and which may explain 
the origin of the instinct of the Gad-fly or OEstrus. We can 
see how the closest association might be developed in 
Swallows, for Lamarck:|: saw a dozen of these birds aiding a 
pair, whose nest had been taken, so effectually that it was 
completed on the second day ; and from the facts given by 
Macgillivray§ it is impossible to doubt that the ancient 
accounts are true of the Martins sometimes associating and 
entombing alive sparrows which have taken possession of one 
of their nests. It is well known that the Hive-bees which 
have been neglected " get a habit of pillaging from their more 
industrious neighbours," and are then called corsairs ; and 
Huber gives a far more remarkable case of some Hive-bees 
which took almost entire possession of the nest of a Humble- 
bee, and for three weeks the latter went on collecting honey 
and then regorged it at the solicitation, without any violence, 
of the Humble-bee. II We are thus reminded of those Gulls 
(Zestris) which exclusively live by pursuing other gulls and 
compelling them to disgorge their food.*lf 

In the Hive-bee actions are occasionally performed which 

* Blactwall's Itesearches in Zoology, 1834, p. 158. Curier long ago 
remai'ked that all the passeres have apparently a similar structure in their 
Tocal organs; and yet only a few, and these the males, sing; showing that 
fitting structure does not always give rise to corresponding habits. [Concern- 
ing birds which imitate sounds when in captivity not doing so in a state of 
nature, see p. 222, where there is evidence of certain wild bu'ds imitating the 
sounds of other species. — Gr. J. R.] 

t Rev. L. Jenyns, Observations in Nat. Hist., 1848, p. 280. 

J Quoted by Greoffry St. Hilaire in Anns, des Miis., tome ix, p. 471. 

§ British Birds, vol. iii, p. 591. 

II Kirby and Spence, Entomology, vol. ii, p. 207. The case given by 
Huber is at p. 119. 

% There is reason to suspect (MacgiUivi-ay, British Birds, vol. v, p. 500) 
that some of the species can only digest lood which has been partially 
digested by other bu-ds. 



376 MENTAL EVOLIJTION IN ANIMALS. 

we must rank amongst the most wonderful of instincts ; and 
yet these instincts must often have been dormant during 
many generations : I refer to the death of the queen, when 
several worker-larvee are necessarily destroyed, and being 
placed in large cells and reared on royal food, are thus 
rendered fertile : so again when a hive has its queen, the 
males are all infallibly killed by the workers in autumn ; but 
if the hive has no queen, not a single drone is ever de- 
stroyed.* Perhaps a ray of light is thrown by our theory on 
these mysterious but well ascertained facts, by considering 
that the analogy of other members of the Bee family would 
lead us to believe that the Hive-bee is descended from other 
Bees which regularly had many females inhabiting the same 
nest during the whole season, and which never destroyed 
their own males ; so that not to destroy the males and to 
give the normal food to additional larvas, perhaps is only a 
reversion to an ancestral instinct, and, as in the case of 
corporeal structures reverting, is apt to occur after many 
generations.! 

I will now refer to a few cases of special difficulty on our 
theory — most of them parallel to those which I adduced 
when discussing in Chapter VIII corporeal structures. Thus 
we occasionally meet with the same peculiar instinct in 
animals widely remote in the scale of nature, and which conse- 
quently cannot have derived the peculiarity from community 
of descent. The Molothrus (a bird something like a starling) 
of N". and S. America has precisely the same habits M'ith the 
Cuckoo ; but parasitism is so common throughout nature that 
this coincidence is not very surprising. The parallelism in 
instinct between the White Ants, belonging to the Neurop- 
tera, and ants belonging to the Hymenoptera, is a far more 
wonderful fact ; but the parallelism seems to be very far from 
close. Perhaps as remarkable a case as any on record of the 
same instinct having been independently acquired in two 
animals very remote from each other in relationship, is that 
of a Neuropterous and a Dipterous larva digging a conical 

* Ivirby and Spcnce, Entomolor/ti, toI. ii, pp. 510-13. 

t [Concerning the question why tlicre are so many drones as to require 
tilling, see Animal Intelligence, p. 16G, where I suggest that among the 
ancestors of the Hive-bee the mules may have been of use as workers. Bvit 
possibly the drones may even now be of use as nurses t-o the larva-, for I am 
told by an experienced bcc-kccper that he believes this to be the case. — 
G. J. ll] 



APPENDIX. 377 

pit-fall in loose sand, lying motionless at the bottom, and if 
the prey is about to escape, casting jets of sand all round.* 

It has been asserted that animals are endowed with 
instincts, not for their own individual good, or for that of 
their own social bodies, but for the good of other species, 
though leading to their own destruction : it has been said 
that fishes migrate that birds and other animals may prey on 
them : f this is impossible on our theory of natural selection 
of self-profitable modification of instinct. But I have met 
with no facts in support of this belief worthy of considera- 
tion. Mistakes of instinct, as we shall presently see, may in 
some cases do injury to a species and profit another; one 
species may be compelled, or even apparently induced by 
persuasion, to yield up its food or secretion to another species; 
but that any animal has been specially endowed with an 
instinct leading: to its own destruction or harm, I cannot 
believe without better evidence than has hitherto been 
adduced. 

An instinct performed only once during the life of an 
animal appears at first sight a great difficulty on our theory ; 
but if indispensable to the animal's existence, there is no 
valid reason why it should not have been acquired through 
natural selection, like corporeal structures used only on one 
occasion, like the hard tip to the chicken's beak, or like the 
temporary jaws of the pupa of the Caddis-fly or Phryganea, 
which are exclusively used for cutting open the silken doors 
of its curious case, and which are then thrown off for ever.| 
Nevertheless it is impossible not to feel unbounded astonish- 
ment, when one reads of such cases as that of a caterpillar 
first suspending itself by its tail to a little hillock of silk 
attached to some object, and then undergoing its meta- 
morphosis ; then after a time splitting open one side and 
exposing the pupa, destitute of limbs or organs of sense and 
lying loose within the lower part of the old bag-like split 
skin of the caterpillar : this skin serves as a ladder which the 
pupa ascends by seizing on portions between the creases of 
its abdominal segments, and then searching with its tail, 
which is provided with little hooks, thus attaches itself, and 

* Kirby and Spence, Entomology, vol. i, pp. 429-435. 
t Linn£eus in Amoenitates Academics, vol. ii; and Prof. Alison on 
" Instinct" in Todd's Cycl. of Anat. and Physiol., p. 15. 
X Kirby and Spence, Entomology, vol. iii, p. 287. 



378 MENTAL EVOLUTION IN ANIMALS. 

afterwards disengages and casts off the skin which had served 
it for a ladder.* I am tempted to give one other analogous 
case, that of the caterpillar of a Butterfly (TheMa), which 
feeds within the pomegranate, but when full fed gnaws its 
way out (thus making the exit of the butterfly possible before 
its wings are fully expanded), and then attaches with silk 
threads the point to the branch of the tree, that it may not 
fall before the metamorphosis is complete. Hence, as in so 
many other cases, the larva works on this occasion for the 
safety of the pupa and of the mature insect. Our astonish- 
ment at this manoeuvre is lessened in a very slight degree 
when we hear that several caterpillars attach more or less 
perfectly with silken threads leaves to the stems for their 
own safety ; and that another caterpillar, before changing 
into a pupa, bends the edges of a leaf together, coats one 
surface with a silk web, and attaches this web to the foot- 
stalk and branch of the tree; the leaf afterwards becomes 
brittle and separates, leaving the silken cocoon attached to 
the footstalk and branch ; in this case the process differs but 
little from the ordinary formation of a cocoon and its attach- 
ment to any object.f 

A really far greater difficulty is offered by those cases in 
which the instincts of a species differ greatly from those of 
its related forms. This is the case with the above mentioned 
Thekla of the pomegranate; and no doubt many instances 
could be collected. But we should never forget what a small 
proportion the living must bear to the extinct amongst 
insects, the several orders of which have so long existed on 
this earth. Moreover, just in the same way as with corporeal 
structures, I have been surprised how often when I thought 
I had got a case of a perfectly isolated instinct, I found on 
further enquiry at least some traces of a graduated series. 

I have not rarely felt that small and trifling instincts 
were a greater difficulty on our theory than those which 
have so justly excited the wonder of mankind ; for an 
instinct, if really of no considerable importance in the 
struggle for life, could not be modified or formed through 
natural selection. Perhaps as striking an instance as can be 
given is that of the worker of the Hive-bee arranged in files 
and ventilating, by a peculiar movement of their wings, the 

* Xirby and Spence, JSniomoIo^q^i/, vol. iii, pp. 208-11. 
t J. O. WesLwood in Trans. Enlomol. Soc, vol. ii, p. 1. 



APPENDIX. 879 

well-closed hive: this ventilation has been artificially imi- 
tated,* and as it is carried on even during winter, there can 
be no doubt that it is to bring in free air and displace the 
carbonic acid gas : therefore it is in truth indispensable, and 
we may imagine the stages — a few bees iirst going to the 
orifice to fan themselves — by which the instinct might have 
been arrived at. We admire the instinctive caution of the 
hen-pheasant which leads her, as Waterton remarked, to fly 
from her nest and so leave no track to be scented out by 
beasts of prey ; but this again may well be of high import- 
ance to the species. It is more surprising that instinct 
should lead small nesting birds to remove their broken eggs 
and the early mutings, whereas with partridges, the young of 
which immediately follow their parents, the broken eggs are 
left round the nest ; but when we hear that the nests of 
those birds (Halcyonidse) in which the mutings are not 
enclosed by a film, and so can hardly be removed by the 
parent, are thus "rendered very conspicuous;"! and when 
we remember how many nests are destroyed by cats, we 
cannot any longer consider them instincts of trifling import- 
ance. But some instincts one can hardly avoid looking at as 
mere tricks, or sometimes as play : an Abyssinian pigeon 
when fired at, planges down so as to almost touch the sports- 
man, and then mounts to an immoderate height :J the 
Bizcacha (Lagostomus) almost invariably collects all sorts of 
rubbish, bones, stones, dry dung, &c., near its burrow : 
Guanacoes have the habit of returning (like Flies) to the 
same spot to drop their excrement, and I saw one heap eight 
feet in diameter ; as this habit is common to all the species 
of the genus, it must be instinctive, but it is hard to believe 
that it can be of any use to the animal, though it is to the 
Peruvians, who use the dried dung for fuel.§ Many analogous 
facts could probably be collected. 

Wonderful and admirable as most instincts are, yet they 
cannot be considered as absolutely perfect : there is a con- 

* Eirby and Spence, Entomology, toI. ii, p 193. 

t Blytli in Mag. of Nat. Eist., iST.S., vol. ii, 

X Bruce' s Travels, vol. v, p. 187. 

§ See my Journal of Researches, p. 167 for tlie Guanaco; for tlie 
Bizcaclia, p. 145. Many odd instincts are connected with the excrement of 
animals, as with the wild Horse of S. America (see Azara's Travels, vol. i, 
p. 373), with the common House Fly and with Dogs; see on the urinary 
deposits of the Hyrax, Livingston's Missionary/ Travels, p. 22. 



380 MENTAL EVOLUTION IN ANIMALS. 

stant struggle going on throughout nature between the 
instinct of the one to escape its enemy and of the other to 
secure its prey. If the instinct of the Spider be admirable, 
that of the Fly which rushes into its toils is so far inferior. 
Kare and occasional sources of danger are not avoided : if 
death inevitably ensues, and creatures cannot have learnt by 
seeing others suffer, it seems that no guardian instinct is 
acquired : thus the ground within a solfortara in Java is 
strewed with the carcases of tigers, birds, and masses of 
insects killed by the noxious exhalations, with their flesh, 
hairs, and feathers preserved, but their bones entirely con- 
sumed.* Migratory instinct not rarely fails, and the animals, 
as we have seen, are lost. What ought we to think of the 
strong impulse which leads Lemmings, Squirrels, Ermines,t 
and many other animals which are not regularly migratory, 
occasionally to congregate and pursue a headlong course, 
across great rivers, lakes, and even into the sea, where vast 
numbers perish ; and ultimately it would appear that all 
perish ? The country being overstocked seems to cause the 
original impulse ; but it is doubtful whether in all cases 
scarcity actually prevails. The whole case is quite inex- 
plicable. Does the same feeling act on these animals which 
causes men to congregate under distress and fear ; and are 
these occasional migrations, or rather emigrations, a forlorn 
hope to find a new and better land ? The occasional emigra- 
tions of insects of many kinds associated together, which, as 
I have witnessed, must perish by countless myriads in the 
sea, are still more remarkable, as they belong to families none 
of which are naturally social or even migratory.! 

* Von Eiich, Descrift. Fhys. des lies Canaries, 1836, p. 423, on the 
excellent authority of M. ileinwardts, 

t L. Lloyd, Scandinavian Adventure, 1854, vol. ii, p. 77, gives an excellent 
account of the migration of Lemmings : when swimming across a lake, if 
they meet a boat, they crawl up one side and down the opposite side. Great 
migrations took place in 1789, 1807, 1808, 1813, 1823. Ultimately all seem 
to perish. See Hogstrom's account in Swedish Acts, vol. iv, 1763, of erminea 
migrating and entering the sea. See Bachman's account in Mag. of Nat. Hist., 
N.S., vol. iii, 1839, j). 229, of the migration of sqviirrels; they are bad 
swimmers and get across great rivers. 

I Mr. Spenee in his Anniversary address to the Entomological Society, 
1848, has some excellent remarks on the occasional migration of insects, and 
shows how inexplicable the case is. See also Kirby and Spenee, Untomology, 
vol. ii, p. 12; and Weissenborn in Mag. of Nat. Hist., N.S., 1834, vol. iii, 
p. 516, for interesting details on a great migration of LibcUulte, generally 
along the course of rivers. 



APPENDIX. 381 

The social instinct is indispensable to some animals, 
useful to still more for the ready notice of danger, and appa- 
rently only pleasant to some few animals. But one cannot 
avoid thinking that this instinct is carried in some cases to 
an injurious excess: the antelopes in S. Africa and the 
Passenger Pigeons in N. America are followed by hosts of 
carnivorous beasts and birds, which could hardly be supported 
in such numbers if their prey were scattered. The Bison of 
K America migrates in such vast bodies, that when they 
come to narrow passes in the river-cliffs, the foremost, accord- 
ing to Lewis and Clarke (?),* are often pushed over the 
precipice and dashed to pieces. Can we believe when a 
wounded herbivorous animal returns to its own herd and is 
then attacked and gored, that this cruel and very common 
instinct is of any service to the species ? It has been re- 
markedf that with Deer, only those which have been much 
chased with dogs are led by a sense of self-preservation to 
expel their pursued or wounded companion, who will bring 
danger on the herd. But the fearless wild elephants will 
" ungenerously attack one which has escaped into the jungles 
with the bandages still upon its legs."| And I have seen 
domestic pigeons attack and badly wound sick or young and 
fallen birds. 

The cock-pheasant crows loudly, as everyone may hear, 
when going to roost, and is thus betrayed to the poacher. § The 
wild Hen of India, as I am informed by Mr. Blyth, chuckles 
like her domesticated offspring, when she has laid an egg; 

* [The note of interrogation is in the MS. — G. J. E.] 

t W. Scrope, Art of Deer Stalking, p. 23. 

X Corse, in Asiatic Researches, vol. iii, p. 272. This fact is the more 
strange as an Elephant which had escaped from a pit was seen by many 
witnesses to stop and assist with his trunk his companion in getting out of 
the pit (AtheiKPum, 1840, p. 238). Capt. Sulivan, K..N., informs me that he 
watched for more than half an hour, at the Falkland Islands, a Logger- 
headed Duck defending a wounded Upland Goose from the repeated attacks 
of a Carrion Hawk. The upland goose first took to the water, and the duck 
swam close alongside her, always defending her with its strong beak ; when 
the goose crawled ashore, the duck followed, going round and round her, and 
when the goose again took to the sea the duck was still rigoroiisly defending 
her; yet at other times this duck never associates with this goose, for their 
food and place of habitation are utterly different. I rery much fear, from 
what we see of little birds chasing hawks, that it would be more philosophical 
to attribute this conduct in the duck to hatred of the cai*rion hawk rather 
than to benevolence for the goose. 

§ Eev. L. Jenyns, Observations in Natural Sistory, 1846, p. 100. 

17 



382 MENTAL EVOLUTION IN ANIMALS. 

and the natives thus discover her nest. In La Plata the 
Turnarius builds a large oven-like nest of mud in as con- 
spicuous a place as possible, on a bare rock, on the top of a 
post, or cactus-stem ; * and in a thickly peopled country, with 
mischievous boys, would soon be exterminated. The great 
Butcher-bird conceals its nest very badly, and the male 
during incubation, and the female after her eggs are hatched, 
betray the nest by their repeated harsh cries.t So again a 
kind of Shrew-mouse at the Mauritius continually betrays 
itself by screaming out as soon as approached. Nor ought 
we to say that these failures of instinct are unimportant, as 
principally concerning man alone ; for, as we see instinctive 
wildness directed towards man, there seems no reason why 
other instincts should not be related to him. 

The number of eggs of the American Ostrich scattered 
over the country, and so wasted, has already been noticed. 
The Cuckoo sometimes lays two eggs in the same nest, leading 
to the sure rejection of one of the two young birds. Elies, it 
has often been asserted, frequently make mistakes, and lay 
their eggs in substances not fitted for the nourishment of 
their larvae. A Spider| will eagerly seize a little ball of cotton 
when deprived of her eggs, embedded as they are in a silken 
envelope ; but if a choice be given her, she will prefer her own 
eggs, and will not always seize the ball of cotton a second 
time : so that we see sense or reason here correcting a first 
mistake. Little birds often gratify their hatred by pursuing 
a Hawk, and perhaps by so doing distract its attention ; but 
they often mistake and persecute (as I have seen) any inno- 
cent and foreign species. Eoxes and other carnivorous 
beasts often destroy far more prey than they can devour or 
carry away : the Bee Cuckoo kills a vast number more bees 
than she can eat, and " unwisely pursues without interruption 
this pastime all the day long."§ A queen Hive-bee confined 
by Huber, so that she could not lay her eggs in worker cells, 
would not deposit, but dropped them, upon which the 
workers devoured them. An unfertilized queen can lay only 
male eggs, but these she deposits in worker and royal cells — 
an aberration of instinct not surprising under the circum- 

* Journal of Researches, p. 95. 
t Knapp, Journal of a Naturalist, p. 188. 

t These facts are given by Dug^s in Anns, des So. Nat., 2nd series, 
tome vi, p. 196. 

§ JSruee's Travels in Aht/ssinia, voL v, p. 179. 



APPENDIX. 383 

stances ; tut " tlie workers themselves act as if they suffered 
in their instinct from the imperfect state of their queen, for 
they fed these male larvse with royal jelly and treat them 
as they would a real queen."* But what is more surprising, 
the workers of Humble-bees habitually endeavour to seize 
and devour the eggs of their own queens ; and the utmost 
activity of the mothers is " scarcely adequate to prevent this 
violence."t Can this strange instinctive habit be of any 
service to the Bee ? Seeing the innumerable and admirable 
instincts all directed to rear and multiply young, can we 
believe, with Kirby and Spence, that this strange aberrant 
instinct is given them " to keep the population within 
due bounds ?" Can the instinct which leads the female 
spider savagely to attack and devour the male after pairing 
with him| be of service to the species ? The carcase 
of her husband no doubt nourishes her ; and without some 
better explanation can be given, we are thus reduced to the 
grossest utiHtarianism, compatible, it must be confessed, with 
the theory of natural selection. I fear that to the foregoing 
cases a long catalogue could be added. 

Conclusion. — We have in this chapter chiefly considered 
the instincts of animals under the point of view whether it is 
possible that they could have been acquired through the 
means indicated on our theory, or whether, even if tlie simpler 
ones could have been thus acquired, others are so complex 
and wonderful that they must have been specially endowed, 
and thus overthrow the theory. Bearing in mind the facts 
given on the acquirement, through the selection of self-origi- 
nating tricks or modification of instinct, or through training 
and habit, aided in some slight degree by imitation, of here- 
ditary actions and dispositions in our domesticated animals ; 
and their parallelism (subject to having less time) to the 
instincts of animals in a state of nature : bearing in mind 
that in a state of nature instincts do certainly vary in some 
slight degree : bearing in mind how very generally we find in 
allied but distinct animals a gradation in the more complex 
instincts, which show that it is at least possible that a complex 
instinct might have be.en acquired by successive steps ; and 

* Kirby and Spence, Entomologi/, vol. ii, p. 161 (3rcl ed.). 
t Ihid., vol. i, p. 380. 

X Ibid., vol. i, p. 280. A long list of several insects which either in 
their larval or matui'e condition will devoxir each other is given. 



384 MENTAL EVOLUTION IN ANIMALS. 

which moreover generally indicate, according to our theory, 
the actual steps by which the instinct has been acquired, in 
as much as we suppose allied instincts to have branched off 
at different stages of descent from a common ancestor, and 
therefore to have retained, more or less unaltered, the 
instincts of the several lineal ancestral forms of any one 
species : bearing all this in mind, together with the certainty 
that instincts are as important to an animal as their generally 
correlated structures, and that in the struggle for life under 
changing conditions, slight modifications of instinct could 
hardly fail occasionally to be profitable to individuals, I can 
see no overwhelming difficulty on our theory. Even in the 
most marvellous instinct known, that of the cells of the 
Hive-bee, we have seen how a simple instinctive action may 
lead to results which fill the mind with astonishment. 

Moreover it seems to me that the very general fact of the 
gradation of complexity of instincts within the limits of the 
same group of animals ; and likewise the fact of two allied 
species, placed in two distant parts of the world and sur- 
rounded by wholly different conditions of life, still having 
very much in common in their instincts, supports our theory 
of descent ; for they are explained by it : whereas if we look 
at each instinct as specially endowed, we can only say that 
it is so. The imperfections and mistakes of instinct on our 
theory cease to be surprising : indeed it would be wonderful 
that far more numerous and flagrant cases could not be 
detected, if it were not that a species which has failed to 
become modified and so far perfected in its instincts that it 
could continue struggling with the co-inhabitants of the same 
region, would simply add one more to the myriads which 
have become extinct. 

It may not be logical, but to my imagination, it is far more 
satisfactory to look at the young cuckoo ejecting its foster- 
brothers, ants making slaves, the larvae of the Ichneumidie 
feeding within the live bodies of their prey, cats playing with 
mice, otters and cormorants with living fish, not as instincts 
specially given by the Creator, but as very small parts of one 
general law leading to the advancement of all organic bodies 
— Multiply, Vary, let the strongest Live and the weakest 
Die. 



INDEX TO MENTAL EVOLUTION IN ANIMALS. 



A. 

Abercrombie, Dr., a case of apoplexy described by, 35. 

Abstraction, 145, 152-3, 352. 

Actinia. See Anemone. 

.^lian, on instincts of capon, 171. 

Esthetic emotions in animals, 341, 315. 

Affection in animals, 345. 

Alcipidm, eyes of, 85-6. 

Alford, Lord, hounds of, 198, 241. 

Alison, Professor, on sense of modesty as instinctive, 193. 

Allen, Grant, on sense of temperature, 97 ; on sense of colour, 100 ; on 
Pleasures and Pains, 106-11 ; on sense of dependence shown by domesti- 
cated dogs, 240. 

Amoeba, power of discrimination in, 55. 

Amphibia, senses of sight, hearing, smell, taste, and touch in, 90 ; memory 
in, 124 ; grade of mental evolution of, 349-50. 

Amphioxus, destitute of auditory organs, 90. 

Anatomy, relation of comparative, to comparative psychology, 5. 

Andrews, J. B., on homing faculty of a dog, 290. 

Anemone sea-, observation upon discrimination of, 48-9 ; sense of smell in, 
83 ; mistaken by a bee for a flower, 168. 

Anger, in animals, 341, 345. 

Annelida, consciousness in, 77 ; special sensation of, 56, 86 ; emotions of, 
344 ; grade of mental evolution of, 344. 

Anthropoid apes. See Ape. 

Ants, brain of, 46 ; memory in, 146 ; individual variations of instincts of, 
183 ; local variations of instincts of, 244-5 ; pets of, 185 ; receiving 
secretion from aphides, 277-8 ; sense of direction in, 295 j slave- 
making instincts of, 317 ; grade of mental evolution of, 350. 

Ape, delusions of a sun-struck, 150 ; intelligence of an anthropoid, 328. 

Apes, anthropoid, using tools, 352 ; grade of mental evolution of, 352 

Aphides, yielding their secretion to ants, 277-8. 

Arachnida, special sensation in, 56. See Spider and Scorpion. 

Argyll, Duke of, on an eagle teaching a goose to eat flesh, 227 ; on origin of 
instincts, 262 ; on instinct of feigning injury, 316. 

Articulata, special senses of, 56, 84-8 ; memory in, 123 ; imagination in, 
145-6; instinct of in feigning death, 303, et seq.; emotions of, 344 j 
grade of mental evolution of, 349. 

Association of Ideas. See Ideas. 

Ataxy, analogous to lunacy, 44. 

Audouin, on puppies learning to imitate cats, 223. 



386 MENTAL EVOLUTION IN ANIMALS. 

Auerhach, on dilemma-time in perception, 134-5. 
Aurelia aurita, nervous system of, 69. 



B. 

Bain, Professor Alexander, on associated movements, 41, 43 ; on associa- 
tion of ideas, 120 ; on perception, 125 ; on ideas as faint revivals of 
perceptions, 142-3 ; on evolution of instinct, 256. 

Eaines, Mrs. M. A., on a puppy learning to imitate a cat, 224. 

Banks, Sir J., on modified instincts of a spider, 209. 

Barking, instinct of, round a carriage, 182, 186 ; instinct of an ofPshoot from 
acquired instinct of protecting master's property, 235 ; not practised by 
dogs in certain parts of the world, 250. 

Barrington, on birds acquiring songs of their foster parents, 222. 

Bastian, Dr., on sense of direction, 292-3 ; on intelligence of orang-outang, 
328. 

Bat, sensibility of blinded, 94. 

Bateman, Dr. Frederick, on relation of intelligence to mass of brain, 44. 

Bates, on memory of Hymenoptera, 123. 

JBatracMa. See Amphibia. 

Baxt, on reaction-time as increased by complexity of perception, 133. 

Bear, becoming omnivorous, 247. 

Beaver, local variation of instinct in, 249 ; relation of instinct to reason in, 
329. 

Beehstein, on Birds, 149, 222-3, 245. 

Bees, memory in, 146 ; instincts of, 166-8, 174-5, 179, 203-9 ; boring holes 
in corollas, 220-1 ; local variations of instincts of, 245 ; sense of direc- 
tion in, 290, 293-4 ; cell-making instinct of, 317 ; grade of mental 
evolution of, 350. 

Beetles, memory in, 123 ; instincts of dung, 244. 

Begging, hereditary transmission of, in dog and cat, 195-6. 

Belt, on memory of Hymenoptera, 123. 

Bembex, instincts of, 166, 191-2. 

Benevolence, in animals, 341, 345 ; in cats, 345-6. 

Bennet, on birds dreaming, 149. 

Bevan, the Rev. J., on mistaken instincts of bees and wasps, 167. 

Bidie, G., on alleged instinct of scorpion to commit suicide, 278 ; on a bull 
feigning death, 313-14. 

Binsley, on crabs feigning death, 305. 

Birds, special senses of, 57 ; sight, 91 ; hearing, 91-2 ; smell, taste, and 
touch, 92 ; colour-sense, 99-100 ; memory, 124 ; perception, 131 ; 
dreaming, 149 ; instincts of young, 161-5, 170-1 ; mistaken instincts 
of, 168; trivial and useless instincts of, 176; attachments between 
different species of, 185, and with other animals, 183-5 ; variations 
in ncst-building of, 209-12 ; valuations in incubating instincts of, 
212-17; instinctive singing of, 222; imitating songs of other birds, 
222-3 ; teaching their young, 226-7 ; local variations of instincts in, 
245-7 ; specific variations of instinct in, 251-5 ; flying towards light, 
279; migration of, 286-9, 2l:)5-7; feigning death, 303-5; feigning 
injury, 316-17 ; emotions of, 345 ; grade of mental evolution of, 351. 

Biscacha, instinct of, 190. 

Black, William, on migration of swallows, 246. 

Blackbird, conveying young, 211. 

Blackie, Professor, on colour-sense, 100. 



INDEX. 387 

Blaine, on Lord Alford's hounda, 198 ; on inherited tendency to bark in 

sporting dogs, 23fi. 
Blue-bird, local variation of instinct of, 210, 216. 
Blyth, ou a fox feigning death, 304. 
Bod, on carnivorous habits of wasp, 245. 
Bond, on variation in nest of nut-hatch, 182. 
Bonelli, Professor, on a migration of butterflies, 286. 
Brain, relation of intelligence to mass of, 44-6. 
Brehm, on old birds educating young, 22f>. 
Brent, on instincts of crossed canaries, 199. 
Brewster, Sir D., on unconscious inference in perception, 321. 
Brodie, Sir B., on infants remembering taste of particular milk, 115 ; on 

inheritance of instinct as due to cerebral organization, 264. 
Brunelli, on stridulation of grasshopper, 86. 
Bryden, Dr. W., on a monkey feigning death, 312-13, 
Buccola, Dr. Gr., on length of the reaction-time in perception among the 

uneducated and idiotic, 138. 
Buchanan, Professor, on imperfect instincts of young ferrets, 228. 
Biichner, on individual dispositions shown by ants, 183. 
Bull, wildness of cross between Indian and common cow, 199 ; Brahmin 

feigning death, 313-14. 
Burdach, on imagination in animals, 151. 
Burrowing, instinct of, 248-9. 

Burton, F. M ., on mistaken instinct of a moth, 167. 
Butterflies, littoral, continuing to frequent an area whence the sea has retired, 

246 J migration of, 285-6. 



c. 

Caddice-fly, instincts of the, 191. 

Calderwood, Professor, on the relation of intelligence to the mass of the brain. 
44. 

Callin, Gr., on sense of direction in man, 293. 

Cameleon, sense of colour in the, 98. 

Canary, diversity of individual disposition of the, 182 ; instincts of crossed 
breeds of the, 199 ; instinctive nidification of the, 226. 

Capon, instincts of the, 171. 

Carpenter, Dr. W. B., on discrimination shown by protoplasmic organisms ; 
on acquired habits, 181 ; on cats not howling in S. America, 250 ; on a 
case of couching for cataract, 322 ; on inheritance of handwriting, 194. 

Carter, H. J., on sensation in Rhizopoda, 80. 

Castration, changes produced by, on instinct, 171-2. 

Cat, idiosyncracies of the, as regards mousing, 182 ; associating with hares, 
&c., 184 ; hereditary disposition to beg in a family of the, 195 ; rearing 
progeny of other animals, 217-18 ; loss of instinctive wildness of the, 
under domestication, 231 ; not howling iu S. America, 249-50 ; sense of 
direction in the, 289 ; cruelty and benevolence in the, 345-6 ; under- 
standing of mechanism by the, 351. 

Caterpillar, instincts of the processional, 342-3. 

Caterpillars, migrations of, 285. 

Cattle, learning to avoid poisonous herbs, 224, 227 ; instincts of wild 
under domestication, 231 ; dwindling of natural instincts of in Ger- 
many, 232 ; sucking bones, 247 ; sense of direction in, 290. 

Causation, appreciated by animals, 155-8. 



388 MENTAL EVOLUTION IN ANIMALS. 

Cephalopoda, intelligence of related to organs of touch, 57 ; eyes of, 88 ; 

ears of, 89 ; tactile organs of, 89 ; colour-sense in, 98 ; memory in, 122 ; 

imagination in, 145 ; grade of mental evolution of, 349-50. 
Cerebrum, functions of the, 34-46. 
Chalicodoma, instincts of, 166. 
Character, individual. See Disposition. 
Chelmon rostratus, 89. 

Cheselden, on a case of couching for cataract, 322-3. 
Chickens. See Birds. 

Choice, as criterion of mind, 17-20 ; physiological aspect of, 47-55. 
Clifford, Professor, on ejects, 16. 
Cobb, Miss, on inheritance of handwriting, 194. 
Ccelenterata, consciousness in, 76, 348 ; special sense of, 83-4 ; emotions of, 

342 ; grade of mental evolution of, 348. 
CoUett, E.., on migration of the lemming, 283-5. 
Colour-sense, 98-104. 
Comparative Psychology in relation to comparative anatomy, 5 ; objects of, as 

a science, 6-7. 
Comte, on Fetishism in animals, 154. 
ConceptuaUsm, 145. 
Conductility, 68. 
Conscience, evolution of, 352. 
Consciousness as the distinctive character of mind, 17 ; evolution of, 70-77 ; 

definition of impossible, 72 ; degrees of, 72 ; time relations of, 73 ; 

possibly developed to supply conditions of feeling pleasure and pain. 111. 
Conte, Le, on cattle sucking bones, 247. 
Couch, on mistaken instinct of a bee, 167-8 ; on variations in the instinct of 

incubation, 182; on a dog learning how to attack a badger, 221; on a 

goldfinch singing instinctively, 222 ; on birds learning and forgetting the 

songs of other birds, 223 ; on tho instinct of feigning death, 303-8, 

315. 
Coues, Captain Elliot, on local variations of instinct in birds, 210, 246-7. 
Crab, olfactory organs of, 87-8 ; experiments in psycliology of the Hermit, 

122-3 ; migration of the Land, 146, 285 ; feigning death, 305 ; reason 

in the, 336, 350. 
Crayfish, kataplexy of the, 308. 
Crex, aquatic habits of the, 253. 
Cripps, on an elephant feigning death, 305. 
Crocodile, alleged dreaming in the, 149 ; divers dispositions in families of the, 

188. 
Crossing, effects of, in blending instincts, 198-9. 
Crotch, on migration of the lemming, 282-5. 
Cruelty in animals, 541, 345. 
Crustacea, special senses of, 84, 87 ; colour-sense of, 98-9 ; memory of, 122 

imagination of, 145-6; grade of mental evolution of, 349-50. 
Cuckoo, mistaken instincts of the, 168 ; parasitic and non-pai-asitic habits or 

the, 251-2 ; parallelism of instincts of the, with those of Molothrus, 

273-4 ; migration of the young, 289. 
CuciiliitcB. See Cuckoo. 
Curlew, sense of hearing in the, 92. 
Curiosity in animals, 279-80, 341, 344. 
Cuttle-fish. See Cephalopoda. 
Cuvier, on birds dreaming, 149. 
Cuvier, F., on attachment of a dog to a lion, 184. 



INDEX. 389 



D. 



Darwin, Charles, on the relation of intelligence of ants to the size of their brains, 
45 ; on movements of plants, 49-51 ; on intelligence of earthworms, 77 ; 
on special senses of earthworms, 86-7 ; on birds dreaming, 149 ; on mis- 
taken instincts of humble-bees, 168 ; on mistaken instincts of an African 
shrew-mouse, 169 ; on variability and natural selection of instincts, 178 ; 
on inherited tricks of manner, 185-6 ; on inherited paces of the horse, 
188 ; on tumbler and Abyssinian pigeons, 188-90 ; on instincts of 
biscacha, 189-90 ; on inheritance of handwriting, 194 ; on vdldness and 
tameness in rabbits, horses, and ducks, 196, and in wild animals, 197 ; on 
effects of crossing upon instincts, 198-9 ; on intelligent imitation by 
animals, 220-2 ; on protrusion of lips by orang-outang, 225 ; on sheep 
and cattle learning to avoid poisonous herbs, 227 ; on obliteration of 
wild instincts under domestication, 231-2 ; on acquisition of domestic 
instincts, 236-9 ; on bees eating moths, 215 ; on local variations of 
instinct in birds, 245-6 ; on the hysena not burrowing in South Africa, 
249 ; on specific variations of instinct as difficulties against the theory of 
natural selection, 251 ; on parasitic habits of Molothrus, 251 ; on adaptive 
structures developed by natural selection, 253-4; on evolution of 
instinct, 263-5 ; on similar instincts of unallied animals, 273 ; on dis- 
similar instincts of allied animals, 274 ; on trivial and useless instincts, 
274-6 ; on instincts apparently detrimental, 276-82 ; on migration of 
lemming, 282 ; on theory of migration, 287-97 ; on sense of direction, 
290-3 ; on instincts of neuter insects, 297-9 ; on instincts of sphex, 
299 and 303 ; on bees boring corollas of flowers, 220-1, 301-2 ; on instinct 
of feigning death, 308 ; on instinct of feigning injury, 316-17 ; on 
reason in a crab, 336 ; on emotions of earthworms, 344 ; on sexual 
selection, 344-5. 

[For all references to matter now published in the Posthumous 
Essay on Instinct, see Index to the Essay, The following are references 
to all the quotations from, and allusions to, the unpublished MSS of 
Mr. Darwin which occur in the pages of the present work.] 

On changes produced in instinct by abnormal individual expe- 
rience, 115 ; on instinctive fear and ferocity in young animals as. 
directed against particular enemies or kinds of prey, 165 ; on mistaken 
instincts of ants, 168 ; on instinct of a kitten modified by individual 
experience, 172 ; on analogies between instincts in species and acquired 
habits in individuals, 179-80; on diversity of disposition in birds, 182; 
on hereditary tricks of manner displayed by a child, 185-6, and by a 
terrier, 186 ; on peculiar dispositions and habits transmitted in croco- 
diles, ducks, horses, and pigeons, 188-9 ; on automatic actions displayed 
by idiots and by an idiotic dog, 193 ; on instinctive wildness and tame- 
ness respectively displayed by the progeny of wild and tame horses, 
rabbits, and ducks, 196 ; on effects upon instinct of crossing, 199 ; on 
intelligent modification of instinct in bees, 207 ; on wild ducks building 
in trees, 211 ; on hive-bees sucking through holes made in corollas by 
humble-bees, 220-1 ; on dogs learning modes of attack by experience 
and imitation, 221 ; on birds of one species learning danger cries of 
birds of another, 221-2 ; on a dog learning by imitation the habits of a 
cat, and lambs and cattle learning to avoid poisonous herbs, 224 ; on 
canaries reared in a felt nest afterwards constructing a normal nest, 226 ; 
on the non-instinctive character of the drinking movements of chickens, 
228-9 J on the incorrigibly wild instincts of sundry wild animals when 



390 MENTAL EVOLUTION IN ANIMALS. 

domesticated, 232 ; on the stupidity of Chinese dogs, 233 ; on the arti- 
ficially bred instincts of sheep-dogs, pointers, and retrievers, 235-7 ; on 
the effects upon artificially bred instincts of crossing, 241 ; on structures 
adapted to obsolete uses, 253-4 ; on the causes of the evolution of 
instinct, 2-64 ; on insects flying into flame, 278-80 ; on the instinct of 
feigning injury as exhibited by the duck, partridge, &c., 316-17. 

Darwin, Dr. E., on mistaken instinct of Musca carnaria, 167; on a cat 
imitating a dog, 224 ; on effects of domestication on instincts, 229 ; on 
bees ceasing to collect honey in California, 245 ; on rabbits not bur- 
rowing in Sor, 248. 

Darwin, Francis, on bees boring holes in corollas of flowers, 302. 

Daphnea pulex, colour-sense of, 98. 

Davis, on instincts of the processional caterpillar, 342-3. 

Davy, Sir H., on an eagle teaching young to fly, 227. 

Death, feigning of, by animals, 303-16. 

Death-watch, feigning death, 309. 

Deceit, in animals, 341, 347. 

Delusions, in animals, 149-50. 

Diagram, explanation of the, 63-9. 

Dilemma-time in perception, 134-5. 

DioncBa, discrimination shown by, 50-1. 

Direction, sense of, 289-94. 

Discrimination, in relation to clioice, 47-62 ; shown by vegetable tissues, 49- 
51 ; by protoplasmic organisms, 51. 

Disposition, individual, of men and animals, 182. 

Dog, sense of smell in the, 93 ; sense of musical pitch in the, 94 ; imagina- 
tion in the, 146 and 148-9 ; homesickness and pining of the, as proof of 
imagination, 151-2 ; appreciation of cause by the, 155-8 ; instinct of 
collie barking round a carriage, 182 ; attachment of the to other animals, 
184 ; inherited antipathy of a, to butchers, 187 ; useless instincts of the, 
176, 190 ; instinct of, in turning round to make a bed, 193 ; hereditary 
transmission of begging in breeds of the, 195-6 ; effects of crossing upon 
instincts of the, 198; learning by imitation, 221, 223-4; teaching 
young, 227 ; influence of domestication upon psychology of the, 231-42 ; 
barking of the, 249-55; sense of direction in the, 289-90; inability of 
the, to appreciate mechanism, 351 ; grade of mental evolution of the, 352. 

Domestication, effects of, upon instinct, 230-42. 

Donders, Professor, on reaction-times in perception, 132, 135. 

Donovan, on cattle sucking bones, 247. 

Dragon-flies, migrations of, 286. 

Dreaming, in animals, 148-9. 

Drosera, discrimination shown by tentacles of, 49-50. 

Duck, sense of touch in the, 92 ; instincts of the young, 171, 196 ; a breed of 
showing fear of water, 188 ; natural wilduess and tameness of the, 196 ; 
instincts of the, modified by crossing, 199 ; conveying young, 211 ; build- 
ing on trees, 211 ; instinct of the, in feigning injury, 316. 

Dudgeon, P., on a cat rearing rats, 218. 

Dujardin, on relation of intelligence of ants to size of peduncular bodies, 46. 

Duncan, on spiders feigning death, 309. 

Duncan, Professor P. M., on instinct of Odjjnerus, 191-2. 

E. 

Eagle, variation in nest-building of the, 182 ; teaching young to fly, 227 ; teach- 
ing a goose to eat flesh, 227. 



INDEX. 391 

Ear, See Hearing. 

Earthworms. See Worms. 

Earwig, memory in, 123 ; parental affection of, 344. 

Echinodermata, nervous system of, 28-30 ; consciousness in, 76, 348 ; special 
senses of, 56, 84 ; memory in, 122, 348-9 ; emotions of, 342 ; grade of 
mental evolution of, 348-9. 

Education of young animals by their parents, 226-9. 

Edward, on local variation of instinct in the swallow, 247. 

Eject, 16. 

Elam, on somnambulism in animals, 149. 

Elephant, intelligence of the, related to the trunk, 57; memory in the, 124; 
dreaming in the, 149 ; instinct of the, in goring wounded companions, 
176 ; feigning death, 305 ; emotions of the, 346 ; using tools, 352. 

Emotions, physiological aspect of, 53 ; which occur in animals, 341 ; origin 
of, 342 ; distinctive, of different animals, 342-7. 

Emulation, 341, 345. 

Engelmann, on protoplasmic and unicellular organisms being affected by 
light, 80; on one infusorium chasing another, 81; on colour sense of 
Englena viridis, 98. 

JEnglena viridis, as affected by light, 80 ; colour sense of, 98. 

Equation, personal, 135-7. 

Evolution, Organic, taken for granted, 7 ; Mental, a necessary corollary, 8 ; 
human, excluded from present work, 8-10 ; of nerves by use, 30-33 ; of 
discriminative and executive powers, 47-62; of mental faculties as 
shown in the diagram, 63-9 ; of consciousness, 70-7 ; of sense of tem- 
perature, 97-8 ; of visual sense, 97-8 ; of colour-sense, 98-103 ; of 
organs of special sense, 103-4 ; of pleasures and pains, 105-11 ; of 
memory, 111-17 : of association of ideas, 117-24 ; of perception, 127- 
9; of imagination, 144-54; of fetishism, 154-8; of instinct, 177-255; 
of reason, 318-35 ; of conscience, 352. 

Ewart, Professor, on Echinodermata, 84 ; on colour-sense of Octojpus, 99. 

Excitability, 68. 

Excrement, instinct of burying, 176. 

Exner, Professor, on physiology of perception, 132-7, 

Eye. See Sight. 

Eyton, on instincts of crossed Geese, 199. 



P. 

Fabre, J., on instincts of Bembex, 166, and of Sphex, 179, 2S9-303 ; on sense 

of direction in bees, 293-4. 
Fear in animals, 341 ; in young children and low animals, 342-3. 
Eeeling. See Sensation. 
Feelings, logic of, 325. 
Feigning death, 303-16 ; injury, 316-17. 
Fenn, Dr. C. M., on imagination in a wolf, 147. 
Ferrets, reared by a hen, 216-17 ; imperfect instincts of young, 228; analogy 

between instincts of, and those of Sphex, 303. 
Ferrier, on functions of the cerebrum, 35. 
Fish, sense of sight in, 89 ; blind, 89 ; luminous, 89 ; sense of hearing in, 90; 

of smell, taste, and touch, 90; of colour, 98-9; memory in, 123-4; 

imagination in, 153, 286 ; feigning death, 303 ; emotions of, 345 ; grade 

of mental evolution of, 349-50. 
Fish, E. E., on birds imitating each other's songs, 222 



392 MENTAL EVOLUTION IN ANIMALS. 

Fiske, on hereditary transmission of begging in dogs, 165 ; on the subordinate 
part played by natural selection in the development of instinct, 256. 

ritch, Oswald, on benevolence shown by a cat, 345-6. 

FitzRoy, Capt., on instincts of wild dogs under domestication, 232. 

Fleming, on delusions shown by rabid dogs, 149-50. 

Flesh-fly, mistaken instinct of the, 167. 

Flounder, sense of colour in the, 98. 

Ford, W., on sense of direction in man, 291, 292. 

Forel, on variations of instinct and individual disposition in ants, 183, 209, 
244-5. 

Fowl. See Hen. 

Fox, the, feigning death, 304, 314-15 ; understanding of mechanism by the, 
351. 

Fox, the Rev. W. D., on inherited tendency to beg in a terrier, 186 ; on in- 
stincts of a retriever, 236. 

Fredericq, on colour-sense of Cephalopoda, 98-9. 

Fritsch, on functions of the cerebrum, 35. 

Frog, colour-sense in the, 98 ; changed instincts of the tree, 254. 

Furnarius, imperfect instincts of the, 281. 

G. 

Galen, on instinct of a kid, 115. 

Oallus hankiva, wildness of chickens reared from wild stock of, 232. 

Galton, Francis, on hereditary genius, 194. 

Ganglia, structure and functions of, 26-33 ; Mr. Spencer's theory of genesis 
of, 32. 

Gardener, J. S., on moths flying into a waterfall, 280. 

Gardner, on intelligence of a crab, 336. 

Garnett, on instincts of crossed ducks, 199. 

Gasteropoda, eyes of, 88 ; memory in, 121. See Mollusca. 

Generalization, 145. 

Gentry, W. K. G., on carnivorous habits of herbivorous rodent, 248. 

Gladstone, W. E., on colour-sense, 100. 

Goatsucker, conveying young, 211. 

Gold-crested warbler, nidification of the, 210. 

Goltz, on functions of the cerebrum, 35. 

Goose, eye of the Solen, 91 ; instincts of crossed, 199 ; learning to eat flesh, 
227 ; instinct of upland, 253 ;■ Siberian, feigning death, 303-4 ; attach- 
ment of a, to a dog, 184-5. 

Goring, instinct of, 176, 379. 

Gosse, on gregarious habits in nidification, 253 

Gould, on instincts of terrestrial geese, 253. 

Grebe, aquatic instincts of the, 253. 

Grief, in animals, 341, 345. 

Grouse, instincts of North American, 201. 

Guanacoe, instincts of the, 190. 

Guer, on somnambulism in animals, 149. 

Guyne, on migration of the lemming, 282-5. 

H. 

Haeckel, Professor, on sense - organs, 81, 85-6 ; on supposed unknown 
sense pobsessed by Fish, 90 j on supposed unknown senses possessed 



INDEX. 393 

by Mammals, 95 ; on evolution of sense-organs, 98 104 ; on colour- 
sense, 100. 

Hall, G. Stanley, on hypnotism lengthening reaction-time in perception, 138. 

Hamilton, Sir W., on pleasures and pains, 105 ; on inverse relation between 
instinct and reason, 338. 

Hancock, on dogs not barking in Guinea, 250. 

Handcock, on obliteration of natural instincts under domestication, 231. 

Handwriting, inheritance of, 194. 

Hate, in animals, 341, 345. 

Haust, on ducks building in trees, 211. 

Hawfinch, learning the song of a blackbird, 222. 

Hawk, eye of, 91 ; old, teacLing young to capture prey, 226 ; changed in- 
stincts of Swallow-tailed, 254. 

Hearing, sense of, in Medusae, 82 ; in Articulata, 86-7 ; in MoUusca, 88-9 ; 
in Fish, 90 ; in Amphibia and Reptiles, 90 ; in Birds, 91-2 ; in Mam- 
mals, 93-4 ; reaction-time of, 132. 

Helix pomatia, memory in, 122. 

Helmholtz, Professor, on reaction-time as increased by complexity of percep- 
tion, 133. 

Hen, instinct of cackling in the, 176, 289 ; wildness of the, when crossed with 
a pheasant, 199; conveying young, 211; experiments and observations 
on the incvibating and natural instincts of the, 213-17 ; drinking move- 
ments of the, not instinctive, 229 ; loss of incubating instinct of tbe 
Spanish, 212. 

Hennabe, on the hyrax dreaming, 149. 

Heredity, in relation to reflex action, 17-18 ; influence of, on formation of 
nervous structures, 33 ; in association of ideas, 43 ; in reference to sensa- 
tion, 95-104 ; to pleasures and pains, 105-11 ; to memory and associa- 
tion of ideas, 111-24 ; to perception, 130-41 ; to instinct, 180, 185-92, 
200-3, 231-42 ; of handwriting and psychological character, 194-5 ; 
of begging in dogs and cats, 195-6 ; of wildness and tameness, 195-7 ; 
of artificial paces in horses, 188 ; with reference to migration, 289, 296-7. 

Hering, on muscle strengthening by use, 112. 

Herman, on reaction-times of different senses, 132 ; on inherited knowledge 
shown by sporting dogs, 239. 

Seteropoda, eyes of, 88. 

Hertwist, Professors O. and R., on nervous system of llediisce, 69. 

Hewetson, on variation in the nest of the nuthatch, 182. 

Hewett, on wildness of hybrids between fowls and pheasants, 199. 

Hill, Richard, on gregarious habits in nidification, 253. 

Hitzig, on functions of the cerebrum, 35. 

Hofaeker, on inheritance of handwriting, 194. 

HoflPmann, Professor, on a puppy learning to imitate a cat, 224. 

Hogg, on instincts of a sheep-dog, 240-1. 

Holiman, on memory in Cephalopoda, 122. 

Homing-faculty of animals, 95, 153-4. 

Home-sickness in animals, proof of imagination, 151-2. 

Honig-Schnied, on reaction-time for taste, 133. 

Hornbill, nidification of the, 255. 

Horse, memory in the, 124; inheritance by the, of artificial paces, 188; 
useless instincts of the, 190 ; natural tameness of the feral, 196 ; sense 
of direction in the, 289-91. 

Houdin, Robert, remembering his art of juggling with balls, 36 ; on rapidity 
of perception acquired by training, 138. 

House-fly, mistaken instinct of the, 167. 



394 MENTAL EVOLUTION IN ANIMALS. 

House-sparrow, nidification of the, 210. 

Houzeau, on stridulation, 86 ; on birds dreaming, 149 ; on mistaken in- 
stincts, 167 ; on inability of infants to localize pain, 326. 

Howitt, A. W., on homing faculty of horses and cattle, 290. 

Huber, on instincts of bees, 168, 203-9. 

Huber, P., on instincts of a caterpillar, 179. 

Huggins, Dr., on sense of musical pitch in a dog, 94; on inherited antipathy 
of a dog to butchers, 187. 

Humboldt, on individual disposition in monkeys, 188. 

Humming-bird hawk-moth, mistaken instinct of the, 167. 

Hunger, sense of, 95. 

Hunter, John, on tricks of manner being inherited, 185. 

Hurdis, on migration of the golden plover, 286. 

Hutchinson, Colonel, on inherited tendency to bark in sporting dogs, 236. 

Hutton, Captain, on wildness of the hybrid between the tame and wild goat, 
199 ; on wildness of chickens reared from wild Gallus bankiva, 232 ; on 
migration, 288. 

Huxley, Professor T. H., on evolution of sense-organs, 104. 

Hydrozoa, nerve-tissues in, 24. 

Hyaena, not burrowing in South Africa, 244. 

Sylohates agilis, its sense of musical pitch, 93, 

Symenoptera. See Ants and Bees. 

Hypnotism, reaction-time under influence of, 138 ; of animals, 308-11. 

Hyrax, dreaming ia the, 149. 



Ichneumon, instincts of the, 166. 

Ideas, association of, 37-8, 111-24; definition of, 118; composite, ana- 
logous to muscular coordinations, 42-4. 

Idiots, size of brain of, in relation to intelligence, 45; personal equation of, 
138 ; tricks of manner shown by, 181 ; automatic actions of, 193 ; imita- 
tive actions of, 225. 

Industry, 341. 

Imagination, 142-58 ; analysis of, 142-4 ; stages and evolution of, 144-5 ; 
stages of, as occurring in different animals, 145-54. 

Imitation, effects of, on formation of instinct, 220-9; by hive-bees of 
humble bees, 220-1 ; by dogs of other dogs, 221 ; by dogs of cats, 223- 
4 ; by birds of one another's songs, and of articulate speech, 222-3 ; by 
monkeys, children, savages, and idiots, 225 ; by young birds in nidifica- 
tion suggested by Mr. Wallace, 225-6 ; of parents by young of sundry 
animals, 226-9. 

Incubation, instinct of, 177. 

Infant, consciousness in the, 77; preferring sweet tastes, and remembering 
taste of milk, 114-16; earliest power of associating ideas, 120-1, and 
mental images, 152 ; when spoon-fed forgetting to suck, 170, 180 ; learn- 
ing to balance the head, &c., 175-6 ; imitative movements of the, 225 ; 
inability of the, to localize pain, 326 ; emotions of fear and surprise in 
the, 342. 

Inference. See Reason. 

Infusoria, See Protozoa, 

Injury, feigning of, by animals, 316-17. 

Insects, eyes of, 84-5; colour-sense of, 99; imagination of, 145-6; instincts 
of, 165-8, 179, 201-2, 203-9, 220-1, 246, 277-81, 285-6, 290, 293-5, 
297-309 ; emotions of, 344. 



INDEX. 395 

Instinct, physiological aspect of, 52 ; as hereditary memory, 115-17, 131 ; 
definition of, 159; involres a mental element, 160; perfection of, 
160-7 ; in youn^ birds and mammals, 161-5 ; in insects, 165-8, 179, 
201-2, 203-9, 220-1, 277-81, 285-6, 290-5, 297, 303-8 ; of flying, 165 ; 
imperfection of, 167-76; as affected by interruption of normal con- 
verse with environment, 169-72, by castration, 171-2, by insanity, 
173-4; trivial and useless, 176; origin and development of, 177-99; 
primary, 180-92 ; secondary, 192-9 ; effects of crossing upon, 198-9 ; 
blended origin or plasticity of, 200-218 ; of nidification, 210-12 ; of 
incubation, 177, 212-13 ; maternal, 212-18 ; as moulded by imita- 
tion, 219-25, by education, 226-9, and by domestication, 230-42 ; of 
singing in birds, 222-3 ; of attacking rabbits in ferrets, 228 ; of drinking 
in fowls, 229 ; local and specific varieties of, 243-55 ; not fossilized, 
250, 254-5 ; evidence of transformation yielded by specific varieties 
of, 250-5 ; views of other writers on evolution of, 256-72 ; general sum- 
mary on and diagram of development of, 265-72 ; cases of special difii- 
culty in display of, 273-317 ; similar in unallied animals, 273-4 ; dis- 
similar in allied animals, 274 ; trivial and useless, 274-6 ; apparently 
detrimental, 276-85 ; alleged, of scorpion in committing suicide, 278 ; of 
flying through flame, 278-80 ; of hen cackling, pheasant crowing, shrew- 
mouse screaming, &c., 280-1 ; of migration injurious, 281-5 ; of lemming, 
282-5 ; of migration, 285-97 ; of neuter insects, 265, 297-9 ; of sphex, 
299-303; of feigning death, 303-16 j of feigning injury, 316-17; in 
relation to reason, 338-9. 



Jackson, C. J., on instinct of the Californian woodpecker, 255. 

Jackson, Dr. J. Hughlings, on pre-perception, 139. 

Jealousy, 341, 345. 

Jeens, C. H., on a puppy learning to imitate a cat, 224. 

Jelly-fishes. See MeduscB. 

Jerdon, on birds dreaming, 149. 

Jesse, on changed instincts of a hen, 215 ; on snakes feigning death, 305. 



K. 

Kataplexy. See Hypnotism. 

Kidd, W., on diversity of disposition in larks and canaries, 182. 

Kingsley, Canon, on migration of birds, 296. 

Kirby, on modified instincts of larvae, 180. 

Kirby and Spence, on larvae remembering the taste of particular leaves, 115; 

on instincts of insects, 166, 167, 179-80, 201, 204-8, 244, 245. 
Kittens, instincts of, 164-5, 172. 
Knight, Andrew, on hereditary transmission of acquired mental endowments 

in animals, 195, 197, 198, 237, 238 ; on intelligence of a bird, 201, and 

of bees, 208. 
Knox, D, E., on a vai-iation in nest-building of the golden eagle, 182. 
Kries, on dilemma-time in perception, 134-5. 
Kuszmaul, Professor, on infants preferring sweet tastes, 115. 



396 MENTAL EVOLUTION IN ANBIALS. 



Lamarct, his tlieory of evolution of nerves by use, 33. 

Lamellibranchiata, eyes of, 88. 

Landrail, feigning death, 304-5. 

Language, as mental symbolism, 153. 

Lankester, Professor, on alleged instinct of scorpion to commit suicide, 278. 

Lapsing of intelligence, 178-80. 

Lapwing, habit of, in flying down to sportsman when fired at, 189 ; 
associating with rooks and starlings, 185 ; instinct of, in feigning death, 
317. 

Lasius acerhorum, local variation of instinct of, 244-5. 

Leech, Dr., on modified instincts of a spider, 209. 

Lemming, migratory instincts of the, 169, 282-5. 

Leptdoptera, sense of hearing in, 86. See Butterfly. 

Le Roy, on imagination of animals, 146-7. 

Leuret, on intelligence of an orang outang, 328. 

Leveret, reared by a cat, 217. 

Lewes, G-. H., case of sleeping waiter described by, 36 ; on sensations a8 
groups of components, 41 ; his definition of Sensation, 78 ; on pre- 
perception, 139 ; on instincts of duckUngs, 171 ; on hereditary trans- 
mission of begging in dogs, 195 ; ignores natural selection in development 
of instinct, 256. 

Lewis, on carnivorous habits of wasp, 245. 

Limpet, memory in the, 121. 

Lindsay, Dr. Lauder, on dreaming and delusions in animals, 148-9. 

Linnaeus, on dogs not barking in S. America, 250. 

Lodge, Colonel, on sense of direction in man, 293. 

Logic of feelings and signs, 325. 

Lonbiere, on local variations of instinct in ants, 244. 

Lonsdale, on memory in a snail, 122. 

Lord, J. K., on instinct of the Californian woodpecker, 255. 

Lubbock, Sir John, on deafness of ants, 86 ; on sense of smell in ants, 87 ; 
on colour-sense of Daphnea pulex and Hymenoptera, 98-9 ; on memory 
of bees, 123 ; on sense of direction in Hymenoptera, 293-5. 

Lucretius, on dreaming in dogs, 148. 

Ludicrous, emotion of, in animals, 341, 347. 

Lunacy, analogous to ataxy, 44. 

Lyon, Captain, on a wolf feigning death, 304. 



M. 

MacFarlane, Mrs. L., on changed instincts of fowls, 215. 

Mackillar, Miss, on changed instincts of a hen, 215. 

Macpherson, H. A., on benevolence shown by a cat, 346. 

Macroglos/sa stellatariim, mistaken instinct of, 167. 

Magnus, Albertus, on instincts of the capon, 171. 

Magnus, Dr., on colour-sense, 100. 

Malle, Dureau de la, on inheritance by horses of artificial paces, 188 ; on 
birds imitating the songs of other birds, 222 ; on a terrier imitating a 
cat, 233-4 ; on old birds educating young, 226 ; on instinct of burying 
Buporfluous food, 233. 



INDEX. 397 

Manimals, special senses of, 57 ; siglit, 92 ; hearing, 93-4 ; taste and touch, 
94 ; coloui', 99 ; memory of, 124 ; perception of young, 131 ; imagina- 
tion of, 146-54 ; instincts of young, 164-5 ; mistaken instincts of, 
169 ; trivial and useless instincts of, 176 ; attachment between dif- 
ferent species of, and with other animals, 184-5 ; imitation in, 223-5; 
teaching their young, 227; local variations of instinct in, 247-50; 
migrations of, 286 ; homing faculty of, 289-91 ; feigning death, 304-5 ; 
emotions of, 345-7. 

Man, mental evolution of, questioned by some evolutionists, 8-10 ; subjective 
and ejective evidence of mind in, 15, et seq. ; relation of size of brain of, 
to intelhgence, 45 ; substitution of machinery by, for muscular action, 
59 ; imagination in, 144, 152-4 ; sense of direction in, 291-3 ; imperfec- 
tion of hereditary endowments of, 326; reason alleged special pre- 
rogative of, 335-40. 

Mania, analogous to convulsion, 44. 

Marshall, Professor John, on sense of smell in Octopus, 89 ; on sense of sight 
in Surinam Sprat, 90. 

Martins, nidification of, 210-11 ; warning chickens against hawks, 221-2. 

McCready, on larvae of a Medusa sucking their parent, 259-60. 

MeduscB, larvae of, sucking parent, 259-60 ; following light not instinctive, 
258 ; nervous system of, 24, 28 ; special sensation in, 56, 81-83. 

Melanerpes formicivorus, peculiar instinct of, 255. 

Memory, of ganglia without consciousness, 35-6 ; analysis of, 111-17; of 
infant, 114-16, 120-1; in MoUusca, 121-2; in Echinodermata and 
Crustacea, 122 ; in Insects, 123 ; in Fish, 123 ; in other Vertebrata, 
124 ; as involved in perception, 129-30. 

Merejkowsky, on colour-ssnse of Daphnea pulex, 98. 

Merganser, instinct of the, in feigning injury, 316. 

Merrill, G. C, on sense of direction in man, 292. 

Mierzejewskis, Dr., on relation of intelligence to mass of brain, 44, 

Migration, 281-97. 

Mill, James, on composite ideas, 44. 

Mill, J. S., ignores heredity, 256 ; on reason, 336-7. 

Milton, on reason of animals, 340 ; on imagination, 154. 

Mind, Criterion of, 15-23 ; considered as subject, object, and eject, 15-16 ; 
activities indicative of, 16 ; physical basis of, 34-46 ; root-principles of, 
47-62. 

Missel-thrush, variation in nest -building of the, 182. 

Mitchell, Sir J., on dogs learning how to attack the Emu, 221. 

Mivart, St. G., on reason, 325, 335-40. 

M'Lachlan, R., on instincts of the Caddice-fly, 191. 

Mocking-bird, 222. 

Modesty, sense of, 193. 

Moggridge, on instincts of ants, 168, and on individual variations of the same, 
183. 

MoUusca, consciousness in, 77 : special senses of, 56, 88-9 ; memory in, 
121-2 ; imagination in, 145-6 ; emotions of, 344 ; grade of mental evolu- 
tion of, 349. 

Molothrus, parasitic instincts of, 251-2, 273-4. 

Monboddo, Lord, on homing faculty of a snake, 153-4. 

Monkeys, sense of musical pitch shown by, 93 ; imagination in, 151 ; dif- 
ferences in disposition of, 188 ; instinctive dread of snakes shown by, 
195 ; love of imitation shown by, 225 ; feigning death, 311-12 ; using 
tools, 252. 

Montagu, Col., on attachments between animals of different species, 184-5. 



398 MENTAL EVOLUTION IN ANIMALS. 

Montaigne on dreaming in animals, 148. 

Morality, indefinite, and evolution of, 352. 

Morgan, Lewis H., on intelligence of the beaver, 329. 

Morgan, Professor Lloyd, on alleged instinct of the scorpion to commit 
suicide, 278. 

Moseley, Professor H. N"., on colour-sense of marine animals, 99; on imper- 
fection of instinct in honey-sucking insects, 167 ; on beavers of Oregon 
not constructing dams, 249 ; on migration of turtles, 286. 

Mouse feigning death, 306-7. 

Musca carnaria, mistaken instinct of, 167. 

Muscles, coordination of, an index of nerve evolution, 38-4i4. 

Mysis, ear of, 87 ; colour-sense of, 98. 

Mysteriousness, sense of, in animals, 155-8. 



N. 

Natural selection. See Heredity. 

Nerve-tissue, structui'e and function of, 24-33. 

Neurility, 68. 

Newall, on carnivorous habits of wasps, 245. 

Newbury, Dr., on beavers not constructing dams, 249. 

Newton, Professor A., on attachments between birds of different species, 

185 ; on starlings imitating ducks, 222 ; on instincts of ring-plover, 246 ; 

on birds flying towards light, 279 ; on migration of birds, 286-7, 295. 
Nidification, variations in instinct of, 182 ; supposed to be due to imitation, 

225-6 ; associated, 253 ; of Thrush and HornbiUs, 255. 
Nightingale, midnight singing of, inlierited, 246. 
Noulet, on nidification of swallows, 211. 
Nuthatch, variation in nest-building of the, 182. 



o. 

Octopus, eye of, 88 ; olfactory sense in, 89 ; imagination in, 146 ; sense of 

colour in, 98-9. 
Odynerus, instinct of, 171-2. 
Offspring, recognition of, 349. 

Orang-outang, protrusion of lips by the, 225 ; intelligence of a, 328. 
Oriole, Baltimore, improvement of nest-building of the, 210. 
Orthoptera, ears of, 87. 
Osmia aurulenta, 208. 
Osmia bicolor, 208. 
Ostrich, caponizing of the, 172. 

Owl, local variation of instinct of the, 210, 246; nidification of the, 210. 
Oyster, memory in the, 121. 



Packard, on local variation of instinct in bees, 245. 
Paget, Sir James, on a parrot learning to open a lock, 351. 
Pains, 105-11. 
Paley on direction of the external ear 93. 



INDEX. 399 

Paralysis analogous to unconsciousness, 44. 
Parental affection in animals, 344. 

Parrot, intelligence of the, related to organs of touch, 57 ; sense of touch in 
the, 92; association of ideas in the, 124; dreaming and talking in sleep, 
149 ; mistaken instinct of the Australian, 167 ; imitating other birds, 
talking, and singing, 223 ; carnivorous tastes developed by the Mountain, 
248 ; changed instincts of the Ground, 254 ; learning to open a lock, 351. 
Partridge, conveying young, 211 ; not using voice when flushed in Ireland, 

245 ; instinct of the, in feigning injury, 317. 
Passu, aquatic habits of, 253. 
Pea-fowl, 213-14. 

Peccari, attachment of a, to a dog, 184. 

Perception, 125-41; definition of, 125-6; evolution of, 127-9; as cogni- 
tion, 127 ; as recognition, 127-8 ; as grouping of previous perceptions, 
128 ; as involving inference, 128, and memory, 129 ; as affected by 
heredity, 130-1 ; in Mammals, Birds, Reptiles, and Invertebrata, 131 ; 
physiology of, 132-41 ; time-relations of, 132-9 ; relation of, to reflex 
action, 139-41 ; as stimulus to instinctive action, 159-60 j illusions of, 
321-2 ; relation of, to reason, 319-26. 
Petrel, changed instincts of the, 254. 

Pewit. See Lapwing. Flycatcher, variation of instinct of the, 210, 246. 
Pheasant, crowing of the cock, 176, 280 ; wildness of hybrid between the, 

and fowl, 199. 
Pig, instincts of young, 164 ; becoming omnivorous, 247 ; homing faculty 

of the, 290. 
Pigeon, insane, 173-4 ; tumbler, 188-9 ; Abyssinian, 189 ; pouter, 189 ; in- 
stinctive fear of the, of cats, lost under domestication, 232 j migration of 
the passenger, 281. 
Pike, W., on an eagle teaching a goose to eat flesh, 227. 
Pining in animals, proof of imagination, 151-2. 
Pitch, musical, appi'cciated by birds, 91 ; by Si/looates agilis, 93 j and by 

dogs, 94. 
Play, 341, 345. 
Pleasures, 105-11. 

JPleuronectidce, sense of colour in, 98. 
Pliny on instincts of the capon, 171. 
Plover. See Ring-plover and Lapwing. 
Pointer. See Dog. 

Polecat, instinct of the, in paralyzing frogs, 303. 
Pollock, Walter, on sense of smell in actinitB, 83 ; on association of ideas in 

a parrot, 124 ; on delusions in a dog, 150. 
Pope on instinct and reason, 266. 

Potts, I. H., on carnivorous tastes developed by parrots, 248. 
Pouchet, on relation between instinct and reason, 339 ; on colour-sense of 

fish, 98 ; on nidification of swallows, 211. 
Pre-perception, state of, 139. 

Preyer, Professor, on evolution of colour-sense, 101-4 ; on infants preferring 
sweet tastes, 114, and remembering taste of milk, 115 ; on instinct of 
chickens, 116-17 ; on I'apidity of perception acquired by training, 138 ; 
on infant learning to balance the head, &c., 175-6 ; on imitative move- 
ments and dreaming shown by the infant, 225 ; on kataplexy of animals, 
308-11 ; on emotions of the infant, 342, 344. 
Prichard, on a puppy reared by a cat, 217, 224. 
Pride, 341, 345. 
Progeny, yearning for, 212-13. 



400 MENTAL EVOLUTION IN AMIMALS. 

Protista as affected by light, 80-1. 

Protozoa as affected by light, 80-1 ; chasing one another, 81. 
Pteropoda, eyes of, 88. 
Pugnacity, 341, 344. 

Pierguin on somnambulism in animals, 149 ; on delusions o£ an ape, 150. 
Psychology, relation of Comparative to Comparative Anatomy, 5 ; distinction 
between, and Philosophy, 11. 



R. 

Eabbit, imagination in the, 147-8 ; instinctive antipathy of the young to 
ferrets, 164-5 ; imperfect instinct of the, with regard to weasels, 169 ; 
natural -wildness and tameness of the, 196 ; not burrowing in Sor, 248. 

Kae, Dr. J., on instinct of ducks, 196; on instinct of grouse, 201. 

Eage, in animals, 346. 

Katel, habit of the, in turning somersaults, 189, 275. 

Kats, understanding of mechanisms by, 351. 

Eattle-snake, tail of the, 277. 

Eazor-fish, memory in the, 122. 

Reaction-time, in perception, 132-5. 

Reason, physiological aspect of, 63 ; supplementing muscular co-ordination 
by machinery, 59 ; definition of, 318 ; evolution of, 319-35 ; relation of, 
to perception, 319-26 ; grades of, 318-25 ; in animal kingdom, 325-9 ; 
Mr. Spencer's views on development of, 330-5; Mr. Mivart's views 
upon, 335-40 ; Mr. Mills' views upon, 336-7 ; in relation to instinct, 
330-40. 

Reaumur, on larvse remembering the taste of particular leaves, 115 ; on 
instincts of bees, 166 ; on instincts of the capon, 171-2. 

Recognition of offspring, 3 19. 

Recollection, 120. 

Reflection, 145, 

Reflex action, explanation of, and theory of its evolution, 26-33 ; arising 
from habit, 38 ; rise of consciousness from, 74-5 ; distinction between, 
and sensation, 78-9 ; in reference to memory and association of ideas, 
111-24 ; to perception, 139-41 ; to instinct, 159-60. 

Regret, in animals, 347. 

Rhea, mistaken instinct of the, 168. 

Remorse, in animals, 341. 

Rengger, on changed instincts of a wild cat in confinement, 172 ; on attach- 
ment of a monkey to a dog, 184. 

Reptiles, sense of sight in, 90; hearing, smell, taste, and touch of, 90; 
colour sense of, 98; memory in, 124; perception in, 131; imagination 
in, 149, 153-4 ; migrations of, 286 ; feigning death, 305 ; emotions of, 
345 ; grade of mental evolution of, 350. 

Resentment, 341, 345. 

Retriever. See Dog. 

Revenge, in animals, 341, 346. 

lihizopoda, powers of special sense in, 80. 

Ribot, on memory, 111-13. 

King-plovers, continuing to build where sea has retired, 246. 

Romanes, G-. J., observations on lledttseB, 31-2; on sea-anemones, 48, 83; 
on JEchinodermala, 8i, 342, 348-9; on sense of hearing in Lepi- 
doptera and Birds, 86, 92 ; on sense of smell in crabs, 87-8 ; on sense 
of musical pitch in a dog, 94; on coloui'-sense of Octopus, 98-9; oa 



INDEX, 401 

earliest age at wliicli an infant is able to associate ideas, 120-1 ; on 
inability of hermit-crab to associate simple ideas, 122-3 j on time-rela- 
tions iu perception, 136-7 ; on sense of mysterious in, and appreci ition 
of cause by dogs, 155-8; on instinctive antipathy of young rabbits to 
ferrets, 164-5 ; on handwriting, 194 ; on incubatory instincts, 213-14 ; 
on animals dying of terror, 307 -8 ; on instincts and emotions of the pro- 
cessional caterpillar, 342-3 

Rooks, associating with starlings, 185. 

Rosa, Baptista, on instincts of the capon, 171. 

Ross, Sir J., on dogs learning how to attack wild cattle, 221. 

Roulin, on cats not howling in South America, 250. 

Routh, Dr., on a puppy learning to imitate a cat, 224. 

Roy, Le, on imagination of wild animals, 146-7 ; on mental characters of a 
dog of wild parentage, 198 ; on the migration of birds, 289. 



s. 

Saint-Hilaire, GeofFroy, on intelligence of an orang-outang, 328. 

Salmon. See Fish. 

Satiety, sense of, 95. 

Savages, sense of direct.'on in, 289, 291 ; tendency to imitation shown by, 
225. 

Schafer, Professor E. A., on nervous system of Aurelia aurita, 69. 

Schneider, on sense of vision in Serpulte, 86. 

Scorpion, alleged instinct of the, to commit suicide, 278. 

Sebright, Sir J., on natural wildness and tameness of rabbits and ducks, 
196 ; on instincts of an Australian puppy, 232 j on love of man as in- 
stinctive in domestic dogs, 239. 

Seeboum, on migration of birds, 289. 

Scinus htidsonitts, change of instincts in, 248. 

Seneca, on dreaming in dogs, 148. 

Sensation, as compound, 40-1 ; physiological aspect of, 51-2 ; defined, 78 ; 
survey of, in animal kingdom, 80-95 ; of temperature, 95-8 ; of colour, 
98-103 ; as distinguished from perception, 125-6 ; as stimulus to reflex 
action, 159-60. 

Sense, muscular, 95 ; of hunger, thirst, and satiety, 95 ; of temperature, 96-8 ; 
of colour, 98-104. 

Serpent. See Reptiles. 

SerpulcE, sense of vision in, 86. 

Setter. See Dog. 

Sexual affection and selection, 341, 344. 

Shame, in animals, 341, 347. 

Shaw, J., on stupidity of dogs in China and Polynesian Islands, 233. 

Sheep, learning to avoid poisonous herbs, 224, 227 ; changed instincts of 
under domestication, 232 ; killed by parrots, 248 j sense of direction in, 
290. 

Sheep-dog. See Dog. 

Shrew-mouse of South Africa, injurious instinct of the, 169 and 280. 
Shuttleworth, Miss C, on mistaken instinct of bees and wasps, 167. 
Sight, sense of, in Protista, 81 ; in Medusse, 81-2 ; in Echinodermata, 84 ; of 
simple and compound eyes, 84-5; of Worms, 85-6; of Fish, 89; of 
Amphibia and Reptiles, 90-1 ; of Birds, 91 ; of Mammals, 92 j reaction- 
time of, 133 ; in young animals, 161-4. 
Sigismund, on infants remembering the taste of milk, 114 



402 MENTAL EVOLUTION IN ANIMALS. 

Signs, logic of, 325. 

Skate, olfactory organs of the, 90. 

Skylark, feigning death, 304. 

Smith, Adam, on a case of couching for cataract, 323-4. 

Smith, Dr. Andrew, on hyjenas not burrowing in South Africa, 249. 

Smith, F., on instinct of bees, 20S. 

Smith, Col. H., on instincts of wild dogs under domestication, 232. 

Smith, W. Gr., on carnivorous habits of wasps, 245. 

Snail, memory in the, 122. 

Snake, homing faculty of the, 153-4 ; feigning death, 305. 

Smell, sense of in Protista, 81 ; in sea-anemones, 83 ; in leeches, ants, and 
crabs, 87-8 ; in Mollusca, 89 ; in Fish, Amphibia, and Reptiles, 90 ; in 
Birds, 92 ; in Mammals, 92-3. 

Snipe, sense of touch in the, 92. 

Social feelings, in animals, 341, 344. 

Solen Groose, eye of the, 91. 

Spalding, Douglas, on instincts of young birds and mammals, 161-5, 170-1, 
175, 213, 216. 

Spallanzani, on sensibility of blinded bats, 94. 

Spaniel. See Dog. 

Speech, acquirement of, by volition, 41-2. 

Spence and Kirby. See Kirby and Spence. 

Spencer, Herbert, on evolution of nerves, 30-2; on consolidation of states 
of consciousness, 42-3 ; on evolution of consciousness, 74-6 ; on plea- 
sures and pains, 105-7; on perception, 125; on memory, 129-30; on 
pre-perception, 139 ; on perceptive faculties arising from reflex, 140 ; on 
ideas as faint revivals of perceptions, 142-3 ; on Fetishism in animals, 
154-5 ; on race characteristics in psychology of man, 194 ; on evolution 
of instinct, 256-62 ; on instincts of bees, 265. 

Sphex, instincts of the, 179, 299-303. 

Sphinx-moth, mistaken instinct of the, 167. 

Spider, using stones to balance web, 59 ; imagination in the, 146 ; modified 
instincts of a, 209 ; distribution of the trap-door, 255 ; feigning death, 
303. See Arachnida. 

Sprat, Surinam, eye of the, 90. 

Squirrel, a, dying of terror, 307. 

Star-fish. See Echinodermata. 

Starlings, associating with rooks, 185. 

Starling, imitating songs of other birds, 222-3. 

St. John, on inherited tendency to bark in sporting dogs, 236. 

Stone, S., on variation in nest-building of the missel- thrush, 182. 

Stroud, Dr. J. W., on change of instincts produced by castration, 171-2. 

Stuorn, on dwindling of maternal instincts of cattle, 232. 

Sturm, on instincts of the dung-beetle, 244. 

Sulivan, Capt., on natural tameness of feral rabbits, 196. 

Sully, J., on distinction between sensation and perception, 125 ; on percep- 
tion as automatic, 126 ; on pre-perception, 139 ; on illusions of percep- 
tion, 321-2. 

Surinam Sprat, eye of the, 90. 

Surprise, 341, 34 i. 

Swallow, plasticity and local variation of instincts of the, 210, 246-7; migra- 
tion of the, 296. 

Swallows, nidification of, 210-11. 

Svvainson, on mistaken instinct of the Australian parrot, 167. 

Svvandcrdam, on instincts of beeB, 166. 



INDEX. 403 

Swift, eye of the, 91. See Swallow. 
Sympathy, 341, 345. 

Sparrow, nidification of the, 210 ; changed instincts of a, 213 ; learning song 
of a linnet, 222 ; local yariations of instinct of the, 247. 



TacJiornis pTioenicohea, 21 2. 

Tailor-bird, modified instincts of the, 210. 

Tait, Lawson, on hereditary transmission of hogging in a cat, 195. 

Tameness. See Wildness. 

Taste, sense of, in Protista, 81 ; in Articnlata, 88 ; in Fish, 90 ; in Amphibia 
and Keptiles, 90 ; in Birds, 92 ; in Mammals, 94, 

Temmick, on migration of birds, 289. 

Tennent, Sir E., on elephants feigning death, 305. 

Temperature, sense of, 95-8. 

Terrier. See Dog. 

Terror, in animals, 345. 

Thirst, sense of, 95. 

Thompson, on imagination in dogs, 146, and other animals, 151 ; on crocodiles 
dreaming, 149 ; on horses becoming attached to dogs and cats, 184 ; on 
efTects of domestication in modifying instinct, 242 ; on a monkey feign- 
ing death, 311-12. 

Thompson, Eev. L., on bees eating moths, 245. 

Thomson, Allen, on instinct of young chickens, 163 ; on instinct of scorpion 
to commit suicide, 278 ; on benevolence shown by a cat, 346. 

Thrush, sense of hearing in the, 92. 

Thwaites, on a breed of ducks showing fear of water, 188. 

Tiaropsis indicans, sense of touch in, 83. 

Tiaropsis polydiademata, sense of sight in, 81-2. 

Tickling, caused only by gentle stimulation, 52. 

Touch, sense of, in plants, 49-51, and 55 ; in Medusoe, Echinodermata, 
MoUiisca, and Articulata, 56 ; in Vertebrata, 58 ; in Fish, Amphibia, 
and Reptiles, 90 ; in Birds, 92 ; in Mammals, 94 j as origin of all 
special senses, 103-4 ; reaction-time of, 132. 

Trevellian, on mistaken instinct of a sphinx moth, 167. 

Trichoptera, instincts of, 191. 

Tricks of manner inherited, 181, 185 6 ; displayed by individuals, 
181-2. 

Turkeys, instincts of young, 164, 175. 

Turtle, migration of the, 286. 



u. 

Ulloa, on dogs not barking in Juan Fernandez, 250, 



Venus' Fly-trap. See Dionaa. 

Venn, on association of ideas by talking birds, 124. 

Villiers, De, on instincts of the processional caterpillar, 312. 



404 MENTAL EVOLUTION IN ANIMALS. 

Vintschgau, on reaction-time for taste, 133. 

Virchow, Professor, on distinction between instinct and reason, 160. 

Volition, physiological aspect of, 53, 352. 

Vorticella, chased by another infusorium, 81. 

Vulture, sense of sight of the, 91 ; of smell, 92. 

w. 

Wallace, A. E., on evolution of Man, 9 ; on changed instincts of nidification, 

212 ; on nidification as due to imitation, 225-6 ; on migration of the 

lemming, 283 ; on migration, 288 ; on homing faculty, 291. 
Water-hen, aquatic instincts of the, 253. • 
Water-owzel, changed instincts of the, 254. 
Waterton, on instincts of young pheasants, 232; on instincts of crossed 

ducks, 199. 
Wasps. See Insects. 
Weasel, feigning death, 307. 
Weber, on sense of temperature, 96. 
Wedderburn, Sir D., on carnivorous habits of wasps, 245. 
Weir, on Wallace's theory of nidification as influenced by imitation, 226. 
Weissenborne, on a migration of dragon-flies, 286. 
Whately, Archbishop, on cattle sucking bones, 247; on the functions of the 

syllogism, 337. 
White, C. Coral, on a fox feigning death, 314-15. 
White, the Rev. G., on loss of taste for flesh shown by dogs of China, 233 ; 

on a leveret reared by a cat, 217. 
Widgeon, attachment of a, to a peacock, 183-4. 
Wildness, acquired instinct of, 195-7, 
Wilks, Dr., on association of ideas by talking birds, 124. 
Will. See Volition. 

Willoughby, on instincts of the capon, 171. 
Wilson, on improved nest-building by the Baltimore Oriel, 210. 
Wilson, Sir J., on instincts of a tamed dingo dog, 232. 
Wittich, von, on reaction-time for taste, 133. 
Wolf, feigning death, 304 ; imagination in the, 147. 
Wolfl", Madame de Meuron, on a migration of but) erflies, 285. 
Wolverine, understanding of mechanism by the, 351. 
Woodcock, wildness and tameness of the, 197 ; carrying young, 211. 
Wood-louse, feigning death, 309. 
Wood-pecker, changed instincts of the Ground, 254 ; peculiar instincts of the 

Californian in storing acorns, 255. 
Worms. See Annelida. 
Wrangle, on geese feigning death, 303-4. 
Wren, local variation of instinct of the, 210, 246; variation in nest-building 

of the golden-crested, 182. 
Wundt, on analogy between conscious and unconscious memory, 114. 



Yarrel, on Birds, 222, 247. 

Youatt, on the Dog, 150, 198, 211 ; on the Sheep, 224, 2L7. 

z. 

Zinken, Dr., on mistaken instinct of flies, 1G7. 



INDEX. 405 



INDEX TO Mr. DARWIN'S POSTHUMOUS ESSAY. 



A. 

Alison, on instinct, 357, 367, 370, 375. 

Amhlyrhynchus, tameness of, 361. 

Angoumois moth, double instincts of the, 373. 

Antelopes, migi-ations of, 381. 

Ants, ceasing to move eggs when heat is supplied to them, 368 ; instincts of 

white, 376. 
Artamus sordidus, variations in nest-building instincts of, 372. 
Audubon, on nidification of Gulls, 369, and of Sterna minuta, 372. 



B. 

Bachman, on migrations of the bison and Canada geese, 356 ; on migrations 

of squin-els, 380. 
Banks, Sir J., an changed instincts of a spider, 373. 
Barrington, Hon. Daines, on wildness of large birds, 362. 
Beaver, habitations of the, 372. 
Bechstein, on migratory and non-migratory thrushes, 355; on varialions in 

the singing of nightingales, 374. 
Bees, instincts of, in making queens, 376 ; in ventilatinsr hives, 378-9 ; mis- 
taken instincts of, 382-3 ; variation in instinct of, 372-3 ; pillaging each 

other, 375. 
Birds, migratory habits of, 355-9 ; tameness of, in islands unfrequented by 

man, 360-63 ; nidification of, 364-72 ; variation of instinct in, 374 j 

instincts of small in mobbing hawks, 382. 
Bison, migrations of the, 355, 381. 
Bizcacha, instincts of the, 379. 
Blackbirds, nidification of a pair of, 371. 
Blackwall, on nidification, 371 ; on magpies not imitating sounds when in a 

state of nature, 374-5 ; on nidification of a yellow bunting, 371. 
Blyth, on instincts of removing mutings, &c., fi'om nests, 379 ; on the wild hen 

cackling over her eggs, 381. 
Bonnet, on double instincts, 373-4; on instincts of ants, 368. 
Botton, on nidification, 369. 

Bourgoanne, on migratory instinct of sheep in Spain, 358. 
Brent goose, migratory impulse of a worn out, 356. 
Brougham, Lord, on instincts of chickens, 374. 
Bruce, on instincts of the Bee-cuckoo, 382 ; on instincts of the Abyssinian 

pigeon, 379. 
Buch, von, on animals dying in the Solfortara of Java, 380. 
Bufialo, migration of the, 355-6. 
Burrowing, instinct of, 372. 
Butcher-bird, nidification of the, 382. 

18 



406 MENTAL EVOLUTION IN ANIMALS. 

c. 

Carmichael, Capt., on tameness of birds at Tristan d'Acunlia, 361. 

Caterpillar. See Insects. 

Chaffinch, nldification of a, 371. 

Chickens, instincts of, 374. 

Chrysomela, feigning death, 364, 

Clarke, on migration of the bison, 381. 

Cluiscus, feigning death, 364. 

Colenso, on a migratory cuckoo in New Zealand, 360. 

Collocalia, nidification of, 365-6. 

Couch, on animals feigning death, 363 ; on nidification, 369, 370, 371. 

Corse, on elephants attacking companions escaped from captivity, 381. 

Crow, hooded, fearlessness of, in Egypt, 363. 

Cuckoo, mistaken instincts of the, 382 j instincts of the Bee, 382. 

Cu7'Chlis, feigning death, 364. 

Cuvier, on Tocal organs of Passeres, 375. 

D. 

B'Arbigny, on knowledge of time shown by a hawk, 357. 

[Darwin, Charles, on tameness of animals in islands unfrequented by man, 
360-62 ; on a lizard feigning death, 363-4 ; on nidification of Collo- 
calia, 365-6 ; on stupidity of Furnarius cunicularius, 371 ; on the in- 
stinct of burrowing, 872 ; on instincts of the Guanaco and Bizcacha, 
379 ; on the nidification of Furnarius, 382. 

Death, feigning of by animals, 363-4. 

Deer, expelling wounded companions from herd, 376. 

De Greer, on insects feigning death, 364. 

Direction, sense of, shown by animals and men, 357-9. 

Dog, instincts of, with regard to excrement, 379. 

Du Bois, on tameness of birds at Bourbon, 361. 

Duck, fearlessness shown by wild, of railway-trains, 362 ; a logger-headed, 
defending a goose from a hawk, 381. 

Duges, on double instincts of spiders, 374 ; on maternal instincts of spider, 
382. 

E. 

Elephants, attacking companions escaped from captivity, 381. 
Elk, migrations of the, 360. 

F. 

Eischcr, Professor, on a hen incubating her eggs in a hot-bed, 367. 

Ely -catcher, a, building nest upon a hot-house, 367. 

Fox, wariness and tameness of the, 361. 

Fox, the Eev. W. D., on the nidification of a pair of blackbirds, and a pair 

of redstarts, 371. 
Fremont, Col., on migrations of the bison, 356. 
Furnarius cunicularius, stupidity of, 371 ; nidification of, 381-2. 

G. 

Gad fly, instincts of the, 375. 



INDEX. 407 

Golden -plover, fearlessness shown by the, of fire-arms, 363. 

Gold-finch, nidification of the, 369. 

Goodsir, on fearlessness shown by wild ducks of railway trains, 362. 

Goose, migratory impulse of a Brent, worn out, 356 ; the Siberian feigning 

death, 363. 
Goring, instinct of, 381. 
Gould, on migration of birds, 355 ; on nidification of Megapodidm, 367 ; of 

Artamus sordidus, 372. 
Graber, on migratory birds of Faroe, 360. 

Grey, Sir G., on sense of direction shown by native Australians, 357. 
Gulls, nidification of, 369 ; parasitic instincts of, 373. 
Guanacoes, instincts of, 379. 

Harcourt, E, V., on non-migratory habits of woodcoct, 356 ; on absence of 

migratory birds in Madeira, 359. 
Hare, alleged burrows of the, 372. 
Hawk, knowledge of time shown by a, 357; tameness of a, at Galapagos 

Islands, 361. 
Hearne, on habitation of the beaver, 372. 
Heineken, Dr., on non-migratory habits of woodcock, 356. 
Hen, wild cackling over her eggs, 381. 
Herbert, Thos., on tameness of birds at Mauritius, 361. 
Heron, wildness of the, 362 ; nidification of the, 369. 
Hewitson, C, on tameness of magpies in Norway, 363 ; on nidification of a 

chaffinch, 371. 
Sirundo, migration of, 358 ; nidification of, 365-6, 369-70. 
Histers, feigning death, 364. 
Hogg, on migratory instinct of sheep, 358. 
Home, on structure of the proventriculus of Collocalia, 366. 
Homing faculty in animals, 358. 
Hogstrom, on migration of ermines, 380. 
Horse, instincts of the, with regard to excrement, 379. 
House-fly, instincts of the, with regard to excrement, 379. 
House-martin, nidification of the, 365. See Martin. 
Huber, on bees pillaging each other, 375 ; on mistaken instincts of bees, 

382-3. 
Huber, P., on double instincts of a beetle larva, 373. 
Hunt, Consul C, on birds visiting the Azores, 358, 359-60. 
Hull, the Rev. J., on nidification of the magpie, 370. 
Hyaenas, not burrowing in S. Africa, 372. ^ 

Hyrax, instincts of the, with regard to excrement, 379. 



Icterus haltimore, nidification of, 372. 

Insects, feigning death, 363-4 ; varied instincts of, 372-3 ; double instincts 
of, 373-4 ; hatched in human body, 375 ; instincts of, exliibited only 
once, 377 ; instincts of, with regard to excrement, 379 ; migrations of, 
378 ; mistaken instincts of, 382-3. 

Instinct, of migration, 355-60 ; of fear, 360-64 ; of nidification, 364-72 ; 
double in certain birds, 371-73, and in certain insects, 373-4 ; of mam- 
mals in forming habitations, 372-3; of beaver and musk rat, 372; of 



408 MENTAL EVOLUTION IN ANIMALS. 

buiTOwing, 372 ; variations in, of bees, 372-3 ; of chickens pecking fheir 
way out of eggs, 374 ; of gad-fly, 375; of parasitism, 375-6; of bees, 
375-6 ; of Molothrus and white ants, 376 ; of digging pitfalls, 376-7 ; 
alleged to be detrimental to the species exliibiting it, 377; only once 
exhibited, 377-8; differences of, in related forms, 378; small and 
trivial, 378-9 ; of removing broken eggs and mutings, 379 ; of Abys- 
sinian pigeon, Lagostomus, and Guanacoes, 379 ; with regard to excre- 
ment, 379 ; imperfect and mistaken, 380 ; social, 381 ; apparently 
detrimental, 381-83 ; of attacking wounded companions, 381 ; of cock 
pheasants crowing and wild hens cackling, 381 ; of shrew-mouse scream- 
ing, ostrich scattering eggs, 382 ; at fault in sundry animals, 182-3. 

Ireland, habits of animals in. See W. Thompson. 

Ischndi, on migratory instincts of Alpine cattle, 358. 

lulus, feigning death, 364. 

J. 

Jackdaw, nidification of a, 370 ; stupidity of a, 371. 

Jenyns, the Kev. L., on habitations of rats, 372 ; on insects hatched within 

the human body, 375 ; on crowing of the cock pheasant, 381. 
Jesse, on the nidification of a jackdaw, 370. 



Kangaroo, regm-gitation of food by the, 374. 

Kirby and Spence, on instincts of insects, 364, 368, 374, 375, 376, 377, 378, 

379, 383. 
Knapp, on nidification of the butcher-bird, 382. 



L. 

Lagostmmis, instincts of, 401. 

Lamarck, on co-operation of swallows, 375. 

Larvse. See Insects. 

Lloyd, L., on migration of the lemming, 380. 

Le Roy, on wariness of foxes and wolves, 361. 

Lewis, on migration of the bison, 381. 

Le Vaillant, on migratory and non-migratory habits of quail, 355. 

Linneus, on instinct, 377. 

Livingstone, on instincts of hyrax, 379. 

Lizards, wildness and tameness of, 356 ; feigning death, 363-4. 



M. 

Macgillivray, on nests of swifts, 365-6, of kitty-wrens, 368 and 370, of 

herons, 369 ; on cooperation in martins, 375 ; ou parasitism in gulls, 

375. 
Magpie, fearlessness of the, in Norway, 362 ; nidification of the, 370 ; powers 

of the, in imitating various sounds, 394-.'). 
Mammals, migrations of, 355-6, 358 -9 ; instinctive fear shown by, 361 j 

habitations of, 372-3. 



INDEX. 409 

Martin, nidificat-on of the, 364, 3fi9, 370. 

Martins, cooperation shown bj, 375. 

Martin, W. C, on regurgitation of food by the Kangaroo, 374. 

Megapodidm, nidification of, 367-8. 

Mice, wariness of, 362. 

Migration, 355-60; of young birds, 355; of quail, 355; of buffalo, 355 fi; 
theory of, 359 ; of elk and reindeer, 360 ; of lemming, squirrel, and 
ermine, 380 ; of insects, 380 ; of pigeons, antelopes, and bisons, 381. 

Molothrus, instincts of, S76. 

Montague, on nidification of sparrows, 369. 

Moresby, Capt., on tameness of birds at Providence Islands, 361. 

Mosto, Cada, on tameness of C. de Verde Island pigeons, 361. 

Musk-rat, habitation of, 372. 

N. 

Nidification, 364-72 ; of swallows, 365-6 ; of MegapodidcB, 367-8 j varia- 
tions in instinct of, 369-73 ; double instinct of, 371-72. 
"Nightingale, variations in singing of the, 374. / 



o. 



Osmia, variation in instincts of, 372-3. 
Ostrich, scattering her eggs, 382. 



P. 

Partridge, variation in instincts of the, 373. 

Peabody, on nidification of Cypelus pelasgius, 365 ; of kitty-wrens, 368 ; of 
herons, 369 ; of Totanus macularius, 371 ; of Icterus baltimore, 372. 

Pheasant, maternal instincts of the hen, 379; crowing instincts of cock, 381. 

Pigeon, fearlessness of the, at C. de Verde Islands, 361, and at Galapagos, 
363 ; instincts of the Abyssinian, 379 ; migration of the Passenger, 381 j 
instinct of the, in attacking wounded companions, 380. 

Ptinus, feigning death, 364. 

Pulex, variations of pupa of, 374. 



Q. 



Q.uail, migration of the, 355. 



R. 

Eae, Dr. J., on feai'lessness shown by birds of railway trains, 362 j and of 

firearms, 363. 
Eat, musk, habitation of the, 372. 
Eat, wariness of the, 362. 
Eeaumur, on instincts of ants, 368. 
Eedstarts, nidification of a pair of, 371. 
Eeindeer, migrations of the, 360. 



410 MENTAL EVOLUTION IN ANIMALS. 

Reinwardts, on animals dying in the Solfortara of Java, 3S0. 
Eichardson, on nidification of American swallows, 369-80. 
Eoberts, M. E., on nidification of Sirundo riparia, 365. 
Kobin, fainting from fright, 363 ; nidification of the, 369. 

s. 

Salmon, migrations of the, 355, 358. 

Savi, Dr, P., on the double instinct of nidification shown by Sylvia cisticola-, 

371. 
Scope, on migration of salmon, 358. 

Scrope, W., on deer expelling wounded companions from herd, 381. 
Sheep, homing faculty of Highland, 358 ; migratory instinct of Spanish, 

358-9. 
Sheppard, on the nidiGcation of a golden-crested wren, 371. 
Shrew-mouse, instinct of a, in screaming when approached, 382. 
Smith, Dr. Andrew, on migrations of quail, 355 j on hysenas not burrowing 

in S. Africa, 372. 
Smith, F., on variations in instincts of bees, 372-3. 
Snake, incubating eggs in a hot-bed, 367. 
Sparrow, nidification of the, 369. 
Spence, on migration of insects, 380. 
Spider, feigning death, 364 ; changed instincts of a, 373 ; double instincts of 

the hunting, 374 ; maternal instincts of the, mistaken, 382 ; instinct of 

the female to devour male, 383. 
Sterna minuta, variations in nest-building instincts of, 372. 
St. Hilaire, Geoffry, on tameness of hooded crows in Egypt, 363. 
St. John, on non-migratory habits of woodcock, 356. 
Sullivan, Captain, on a duck defending a goose from a hawk, 381. 
Swallows, migration of, 358 ; nidification of, 365-6, 369-80 ; cooperation of, 

375. 
Swans, nidification of, 370. 

Swift, non-migratory habits of the, 356 ; nidification of the, 365-6. 
Sylvia cisticola, double instinct of nidification shown by, 371. 

T. 

Taylor-bird, nidification of the, 369. 

Thompson, E. P., on instinct, 357 ; on wariness of rats and mice, 362. 

Tliompson, W., on non-migratory habits of quail in Ireland, 355, and of 
woodcock in Scotland, 356; on a Brent goose losing its migratory 
instinct, 356 ; on N. American birds visiting Ireland, 358 ; on fearless- 
ness shown by birds of railway trains, 362 ; on nidification of heron, 
369 ; of robins, 369 ; of water-hens, 370 ; of magpies, 370 ; of thrushes, 
371 ; on variations in instinct of partridges, 374. 

Thrush, migr