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■

MENTAL EVOLUTION m ANIMALS.

BIT

GEORGE JOHN ROMANES, M.A., LL.D., F.R.S.,

ZOOLOGICAL SECEETAET OF THE LINNEAN SOCIETY.
WITH A

POSTHUMOUS ESSAY ON INSTINCT.

CHAELES DAEWIN, M.A., LL.D., F.E.S.

LONDON:
KEOAX PAUL, TEENCH, & CO., 1, PATERNOSTER SQUARE.

1883.

nABRISON AND SONS,
IKINTERS IN OBDINARY TO HER MAJESTY.

ST. martin's lane.

{The ri(jhts of trans] aiion and of reproduction are reserved.)

PRE FAC E.

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 writino-s 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
liitherto unpublished material from the MSS of the late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availed myself of such of this unpublished material as came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 liimself 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 published at the Linnean Society, and w^ith the
consent of ]\Ir. Darwin's family, as much of this material as

2 PREFACE.

could be published 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, COEXWALL TeEEACE,

Regent's Paek, London, N.W.,
November, 1883.

CONTENTS.

Peeface
Inteodtjctiox
Chaptee I.

II.
III.

IV.

YI.

Til.

VIII.

IX.

XI.

XII.

The Criteeion of Mind

The Steuctuee and Ftjxctioxs of Neeye-Tisstje

The Physical Basis of Mind

The Eoot-peixciples of Mind

Explanation of the Diageam:

Consciousness

Sensation

Meiioey, aed Association

Pleasuees and
of Ideas

Peeception

Imagination

Instinct . .

Pains

Instinct {continued).

Origin and Development of Instincts

XIII. Instinct {continued).

Blended Origin, or Plasticity of Instinct. .

XIV. Instinct {continued).

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

XV. Instinct {contiyiued).
Domestication

XVI. Instinct {continued).

Local and Specific Varieties of Instinct . .

XVII. Instinct {continued).

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

A 2

PAGE

5
15

24
34
47
63
70
78

105
125
142
159

177

200

219
230
243

256

4 CONTENTS.

PAGE

Chapter XVIII. Instinct {continued).

Cases of Special Difficulty with Regard to the
Foregoing Theory of the Origiu aud Develop-
ment of instincts

XIX. Reason

Ai'pen:

273

318

XX. Animal Emotions, and Summary of Intel-
lectual Faculties '^'^'■

353

INTRODUCTION.

In the family of the 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 com2Jarison in each case begins with the facts that
are first found to be com^arcihU, 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 INTRODUCTIOX.

in its pursuit many and varied points of interest, which are
quite distinct from any interest that 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 tlie 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, tliere 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

INTRODUCTION. 7

been to present a book, if not of inconvenient bnlk, 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 du^ect obser-
vation within which my former work was confined ; and it is
chiefiy 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 ted 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 the
manner and history of IMental 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 IMental Evolution, at all events as
far as tlie brute creation is concerned. For throughout the
brute creation, from wholly unintelligent animals to the most
liigldy intelligent, we can trace one continuous gradation ;' so
tliat if \\Q already believe that all specific forms of animal
life have had a derivative origin, w^e 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 evidence 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 j\Iental 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 wiU 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.
Eor it is notorious that from the hour when Mr. Darwin and
Mr. Wallace simultaneously propounded the theory wdiich
has exerted so enormous an infiuence on tlie thought of the

INTRODUCTION". 9

present century, the difference between the 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 7iatural
genesis, the followers of Mr. Wallace maintain that a distinct
exception must be made to this general statement 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 slowdy evolved from lower types of psychical exist-
ence, and according to the other the mind of man, not having
been thus evolved, stands apart, sui 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. ISTow 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 IXTRODUCTIOX.

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
difference 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 wauld 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 publish 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,

INTRODUCTION. 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 philosopliical 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, 1882.

12 INTRODUCTIOX.

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 sliall 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 do 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

IXTEODUCTIOX. 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.

ERRATUM.

Page 145, for Conceptualism read Realism.

MENTAL EVOLUTION IN ANIMALS

CHAPTER I.

The Ceiteeion 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. For if I contemplate my own mind, I have an imme-
diate cognizance of a certain flow of thoughts and feelings,
wdiich 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 which 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 my 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 CRITERION OF MIND. 17

cumstances : 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 tlie 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 ;
whereveE 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. Keflex actions, under the influence
of their appropriate stimuli, may be compared to the actions

\Ci

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 (orL'
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 complex 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 ; w^e 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 wliich
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 witli
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

B 2

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, tliere 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 inherited machinery of the nervous system
does not furnish data for our prevision of what the adaptive
action must necessarily be — it is onl}^ 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 CRITERION 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 tJiat 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 memory, 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 application, 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 sufticiently 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 docs learn by its own individual

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
1 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

I 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
i'act — 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 CKITERION OF MIND. 23

mind other than that of the individual objector. 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."

2'4 MENTAL EVOLUTION IN ANIMALS.

CHAPTEE 11.

The Stkucture and Functions 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 wliich 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 STRUCTURE AND FUNCTIONS OF NERVE-TISSUE. 25

¥iG. 1. — Motor Nerve Cells connected by
intercellular processes (h, h), 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 ; h,
branobed processes, magnified 150 dia-
meters. (Deiters.)

connect the 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 tlierefrom
(mechanical stimuli), sudden elevations of temperature (ther-
mal stimuli), molecular changes in the nerve-substance pro-

MENTAL EVOLUTION IN ANIMALS.

duced by irritants (chemical stimuli), eflfects 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
Cells. Magnified about 400 diameters. (Lejdig.)

])rocess, which is termed Keflex 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 the
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 oan^flia, 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
wdiich 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 onl}^ 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 stimulus or molecular disturb-
ance ; the ganglion 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 tlie 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 developed neuro-
muscular system — the ganglia are arranged in a ring round

* For a full account of reflex action in Medusae, see Phil. Trans., Croonian
Lecture, 1875 ; also Fhil. 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, tlirows 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 u.nmutilated 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 ; vre 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 nowliere 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
stimulation 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 undifferentiated proto-
plasm, Mr. Spencer starts from the fact that every portion of
the colloidal mass is equally excitable and equally contrac-

* For a full account of tliese experiments, see Croonian Lecture, Phil.
Trans., 1883.

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. Wlien
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 has 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 a 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 tlirough 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 tliis, I may refer to a lecture pubHshed in the Proceedings of the
Boyal Institution for 1877, on " Evolution of Nerves." The principal facts
are that when physiological continuity of a sheet of neuro-muscular tissue is
interrupted by overlapping or spiral sections, so that the passage both of
visible or muscular waves of contraction and invisible or molecular waves of
Btimvilation 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 neitlier the waves of contraction nor those of stimulation are
any lonf^er hindered. Whether in such a case a definite nerve-fibre is de-
veioped%r only a " line of discharge," I cannot say ; but most probably the
passage is effected through 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 dilferentiation of a particular kind of already dif-
ferentiated tissue, where this is exposed to particular kinds of stimulation.

THE STRUCTURE AND FUXCTI0X3 OF XERVE-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 nmscles 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 sliould still more completely adapt the
anatomical plan of ganglia, with tlieir 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 nei'vous
machinery may at last come to be differentiated into specially
distributed anatomical structures, wdiich, 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 of
Keflex Action.

* Mr. Darwin called my attention to the following passage in the writings
of Lamarck (Phil. Zool., tom. ii, pp. 318-19) : — " Dans toute action, le
fluicle des nerfs qui la proToque, subit un mouvement 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 uue route, qui lui
derient alors d'autant plus facile a parcourir, qu'il I'a effectivenient plus
souvant francliie, et qu'il n'ait lui-meme une aptitude plus grand a suirre
cette route frayee que celles qui le sout 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 centralizing 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,
i^ow 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 hemisjoheres 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 researclies of
Hitzig, Fritsch, Ferrier, Goltz, and others ; but we must pass
on to consider that function of these great nerve-centres witli
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 qud 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 rememhers the pre-
vious occurrence of its own discharges ; these discharges have
left behind them an impress ujdou 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 interAal is allowed to elapse

c 2

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
w^onclerfully well. Again, Lewxs 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; 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 hnd.

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 wliich 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. For 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 eflect 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 rec\n in the same order as that in wliich thev

38 MENTAL EVOLUTION IN ANIMALS.

have previously occurred, is merely a psychological expres-
sion of the physiological 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 long course of ganglionic instruction, cease to be
conscious actions, and thei^efore become in no way distin-
guishable from reflex actions.*

But the proof of .the fundamental correlation between
ganglionic 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, wdiich
is precisely the same in kind as that which on the lower
plane (that of muscular movement) has led to the advancing
developmeut 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
syi^tem, 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
ftheir 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 differencse of organized habit — the habit
in each case haying 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. Whetlier 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 w^e 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 distmction 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 w^e
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 1 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

liiglily 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 furtlier 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 tlie 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 brieHy 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 wliich
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 tw^o,
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,

* Prollems, ^^c, p. 260.

42 MEXTAL EVOLUTIOX IX AXIMALS.

are, after a time, cemented with all the firmness of the
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
minister 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. Tlius 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 ditficulty. 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 simaltanaous
blending of simple ideas into one complex idea, but also
with reference to the sicccessive 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 lirmly 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. i
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 alluding to a difliculty which may
occur to some minds, and which has been well stated by
Professor Calderwood in his recently published work.* The
difliculty 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.

THE PHYSICAL BASIS OF MIND. 45

kind, it is not a constant relation. Even within the limits of
the human 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. Frederick 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, w^e 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 w^e 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 wiiich
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 intellioent
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

L 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 7:'/?is 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
riiultum in paTvo, 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 ROOT-PRIXCIPLES OF MIND.

CHAPTER IV.

The Eoot-principles of Mind.

Although tlie phenomena of Mind, and so of Choice, are
both complex, and as to their causation obscure, I think we
liave now seen that we are justified in behevino- 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 wdiicli w^e 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 w^e are agreed that every psychical change of which we
have any experience is invariably associated with a definite
physical change, wdiatever w^e 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 indiiferently call it, a
physiological side, I shall endeavour to point out wdiat I con-
ceive to be the most ultimate principle of physiology which
analysis show^s to be common to them all. On the mental
side, as w^e have already seen, we have no difficulty in dis-
tinguishing this ultimate principle, or common characteristic,
as that which we designate by the terra 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-
loo-ical development than in tlie functions of the human
brain. For not only do the lower animals manifest, in a
lono- descending scale, powers of choice which gradually fade
away into greater and greater simplicity ; but we should be
led a 2^riori 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 d ]3riori 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 upon one side of the tank near the surface of the
water, and if a jet of sea water is r^ade to play continuously
and forcibly upon tlie 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 that it will expand its tentacles
in search of 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-PPJNCIPLES 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
with 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 tlie most carefully observed
facts with regard to this interesting subject are those which
we owe to the later researches of llr. 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 the
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
only -j^] 40 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 whether 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 spring-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 pressure
that is so delicately perceived, while the stimulus supplied
by wijMct 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 wdioUy
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 tlie 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 which 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 the 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
viscid secretion, and the slight, though prolonged pressure

THE ROOT-PRIXCIPLES 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 these 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 of the most artificial construction . . .
From the same sandy bottom, 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-sprain 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 tlie 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

* Contemporari/ Review, April, 1873.

D 2

52 MENTAL EVOLUTION IN ANIMALS.

responses are appropriate. In order to see this, let us take
the principal faculties of mind in their ascending order, and
consider what 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.

J Again, many of the nervous mechanisms which minister to
various Keflex 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 caU
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 KOOT-PRINCIPLES OF MIND. 53

physiologically considered, the emotions are the activities of
highly wrought nervous mechanisms, and these activities are
only excited by tlie 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 the ,
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 wdiich 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 w^hich, 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 w^e 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 different kinds of stimuli, irrespective of their
degrees of mechanical intensity. But, before giving a brief

54" MENTAL EVOLUTION IN ANL^L1LS.

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 w^ait 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 Avith 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 ehoosing 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 they refer to things which are the product of a
gradual evolution — things which came from other things 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 ROOT-PEINCIPLES OF MIND. 55

Feeling 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 wliich 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
wliich 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 between
light and darkness, and to adapt their movements to seek tlie
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
different kinds of contact ; and, in correspondence with this
advance in receptive power, we observe a commensurate

56' MENTAL EVOLUTION IN ANIMALS.

advance in the 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 are able to distinguish quicldy and accurately between
moving and not moving objects coming upon them from
various sides, as well 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,
swinmiing 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
wdiich 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 numerous 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 antennae and highly perfected organs
of special sense, is also greater. And the same principles
hold throughout the Yertebrated series. It has already been

THE EOOT-PEIXCIPLES 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 Elepliant 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 correhited 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, lips, and jaws, as well as to some extent in the
paws. I think the superior intelligence of the Octopus, among mollusks, is
to be attributed to the excepfional advantages which are rendered bj its large
and flexible, sensitive and powerful arms.

58 MENTAL EVOLUTION IN ANIMALS.

tlie 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

I to study the effects of these finer mechanisms.

I I 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-PPJXCIPLES OF MIND. 59

Thus the two faculties are, as it were, necessarily bound
together. But here another consideration arises. They are i
thus bound together only up to the point at which the adap- j
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 inaugurated. 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 betwxen 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 A
compared with the co-ordinated movements of a spinning- I
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 1
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 powders of adjustive
movement have been emancipated from their necessary
alliance with his powers of muscular co-ordination.

I say, from his powers of 7iiuscular co-ordination, because
it is evident that our powers of adjustive movement, and so
of adaptation in general, have never been, and can never be,
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 ofcX
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
yp' 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 prol3able 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

>f 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
understand 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-PRIXCIPLES OF MIXD. 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 witli 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. Alore 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 EVOLUTIOX 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-sighted of actions, adapted to meet the most
remote contingencies of stimulation, 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 DIAGRAM. 63

CHAPTEE 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 ]\Iind. 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 diaOTam embodies the

results of my analysis throughout, 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
^ave 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 e\^erywhere
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 furnisli upon the subject ; and
although it is no doubt true that the progress of science may
affect the diagi-am 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 suthciently coherent

64 MENTAL EVOLUTION IN ANIMALS.

to render it higlily 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.

From 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, on]y
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 DIAGRAM. 65

_ce£tion, 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 exJnbit 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 branches 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 sundr}^ 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 ages 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 colunnis, 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
liigher 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 EVOLUTIOX IX 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 outline 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 which 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, l^ranches, and the
two parallel columns 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 tlie faculties of nutrition,
excitability, 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 DIAGRAM. 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 develoj^ment — 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 !'■
have either a j^'^^iori reasons or actual evidence to conclude >
that they first definitely appear in the growing structure of'
Mind ; 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 h}^o-

E 2

68 MENTAL EVOLUTION IN ANIMALS.

thesis ; aad, 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 ciccept 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 his 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 \h.Q 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
Xeurility, or the stem of Mind ; in these levels occur the

EXPLANATION OF THE DIAGRAM. 69

Non-nervous Adjustments, Unicellular Organisms, and 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 Coelenterata, 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 wdiether 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. Schafer on Nervous System of Atirelia Aurita, Phil.
Trans., 1878, and Profs. O. and R. Hertwig on Das Nervensystem und die
Sinnesorgane der Medusen.

cyr^

70 MENTAL EVOLUTION IN xVNIMALS.

CHAPTEK 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 promicent
attention to the fact that fram 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
processes, it is impossible to avoid a certain amount of over-
lapping with 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 their probable evohition, it may often appear
chat 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, liave 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 througli-
out — viz., that all mental processes must be regarded as pre-\U
senting physical counterparts.* 1\»

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 tliis 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
" Xervous 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 the impossibility of entirely sepa-
rating psycliology from pliysiology for the purposes of exposition will, mutafist
ynufandis, 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
I 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
I 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
j 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 anaesthetic, will remember the peculiar experience of feeling
consciousness becoming obliterated by stages.

CONSCIOUSNESS. 73

For in our own orc^anisms we know that 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 witli 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 sul)sequently 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
"takincf in" the situation. And anv 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 MEXTAL EVOLUTION IX ANIMALS.

response (liowever complex this may be), it has to give rise
in the nerve-centre to a play of stimuli before the appropriate
response is yielded. In the higher planes of conscious 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
I 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 inanv stimuli without some s^andion
through which they are all brought into relation. In the pro-
cess of bringing them into relation, this ganglion 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 perj)etual 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 Psychology, voL i, p. 435. I think, 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 liave anything to do with the
rise of consciousness, except in so far as it may be conducive to what we may
term the ganglionic friction, which is expressed by delay of response.

CONSCIOUSNESS. 7o

them 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 chanires into con-
centrated serial changes. AVhether 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 all 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 MENTAL EVOLUTION IX ANIMALS.

the 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
brieiiy 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 sufficiently 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 Coelenterata 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 refiex 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 F/iil. Trans., Croonian Lecture, 1881.

CONSCIOUSNESS. 7V

place -upon a still higjher 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-lDorn 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 Mollusca — 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 unrpies-
tionably intelligent.

* See his work on Earthicorms, 1S81.

78 MENTAL EVOLUTION IN ANIMALS.

CHAPTER VIL

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 Eeflex 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. AVhen 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

iaculties ; it only 1ms to do with tlie 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 witli 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; w^e 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
somew^here 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 Ccelenterata. In doing
this, it is needless to observe, I am drawing the line quite
arbitrarily. On the one hand, for anything tliat is known to
the contrary, not only the sensitive plant which responds to
a mechanical stimulus, but even tlie 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 wdiether 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 vaHdity of such
inference clearly diminishes wdth 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 LewcF, 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 Eitgleiia viridis. After
precautions had been taken to eliminate causes 1 and 2, it
w^as 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 w^hether 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
'viriclis prefers the blue.*

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

* For fall account of these experiments, see PJliiger^s Arckiv.f. d. ges.
Fhijsiologie, 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 are some that love light,
and some tliat 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 yV 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 Medusse, it is among them also that we first
meet with organs of special sense. I have myself observed
that several species of Medusae seek tlie 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 polydiadcmata, 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 lio^ht
requires to fall in order to constitute an adequate stimulus ;
just as a pliotographic plate requires 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-
ori^jan. 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 Medusae 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 Medusae 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 Medusae, 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 otlier species of Medusae,
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 manubrium 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 lon.fjer able to
localize the seat of contact. Nevertheless it feels that con-
tact is taking place somewhere, 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
tlie 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 Actinite Mr. Walter Pollock and myself have ob- 5'
tained conclusive evidence of the sense of ^mell. For 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.

F 2

84 MENTAL EVOLUTION IN ANIMALS.

with unmistakeable evidence of the occurrence of all the five
senses — or, more correctly, with nnmistakeable 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

h 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 coiTesponding 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 smell 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 this 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 sec things, not in the position
in wdiich they ai'e 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, wdiile 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
HcTeckelf — "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 Alcipidse, which are highly organized Annelidas
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." Fnrther, 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 w411 suddenly Avithdraw
their expanded tufts when a shadow falls upon them ; but the
shadow must be that of an object moving with some rapidity. -|-
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.J 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 his position, upon
which the female approached him.|| I have myself published
observations proving the occurrence of a sense of hearing
among the Lepidoptera.^ Turning to the morphological side
of the subject, it is remarkable that in the Articulata the

* See EartJiioorms^ pp. 19-45. f Ber thierisohe Wille, s. 194.

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

§ Hseekel, 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.

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

SENSATION. 87

auditory orojans occur among different members of the group
in widely different parts of the body. Thus in tlie 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 tibit^ 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 \P
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 smell 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 means of their antennse. 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 Eye among
Yermes, and also, as we shall presently see, among Moliusca.
f Darwin, loc. cit.^ 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 tiie 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 Mollusca, 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 supplementary 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-

SENS ATI ox. 89

gous 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. For 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 species {e.g., the Skate)
being of enormous size in relation to the other parts of the
brain. Tlie sense of touch is provided for in many species
by tentacular 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 tliere 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 j)art of the animal. I say over any other
part of the animal (and not only in the nasal fosscc), 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. H?eckel, 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

* Marshall, Outlines of Physiology ^ vol. i, p. 603.

SENSATIOX. 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
deprli of many fathoms in tlie water ; or the eye of a Swift,
which is able so suddenly to form its adj ustments ; 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 ^'isual 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 jDrotection at the present
day. In other w^ords, the evolution of the eyes of birds and
of the protective coloration of their 23rey must be supposed
to have progressed ;pari j^ctssic, 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^ sig'lit,
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 EYOLUTIOX 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
Eeptiles, 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 reaches its
greatest supremacy in Birds, aU 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, wliere also see in more detail my
observations on the feeding habits of the curlew,
t See Animal Intelligence, pp. 286-7.

SENSATION. 93

tory sense ; and it is not until lie ]ias himself seen tlie 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 Regent'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, tlien 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 tliat 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 degree 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. AVith the exception of the singing monkey {Hylohates
agilis), there is no evidence of any mammal other tlian man

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 mastiff " 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 Mustelid?e 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 with cotton-
wool, it is still 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

SEXSATIOX. 95

sense-organs as it occurs in the sight of the vulture or the
smell of the dog. Indeed, Haeckel 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 Haeckel in
his view that the " homing " faculty of certain animals is due
to some additional and inexplical3le sense, and therefore I
shall reserve my treatment of this topic for my chapters on
Instinct.

After this rapid survey of the powders 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-tibres 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 tlie 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

CT-

96 MENTAL EVOLUTION IN ANIMALS.

extent of the receiving surface, the greater is the impression ;
so that if tlie 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 wdth w^hich the special
mechanism we are considering is not concerned) ; and there-

Ifore we have to contemplate the probable cause of its origin

land 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

SEXSATIOX. 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 batlis. 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 astonishing 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. IMoreover, 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.
iBut 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 wliich
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-
j 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, a ad 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 evidence 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 cha-
meleo) is known to cliange 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

J^ analogous facts occur among the Cephalopoda {e.g., odojy^is),
Batrachia (e.g., Common Frog), Pteptilia (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 Pleuronectidse 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.
M. Fredericq afterwards found the same thing to be true of
the Octopus, and in conjunction with Professors Burdon-

* Joiirn. Linn. Soc, 1881. These observations have been adversely criti-
cized by Merejkowsky {Comj)tes Hendus, xciii, pp. 160-1), but his criticisms
have been fully met by further experiments recently pubhshed by Sir John
{Journ. 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 further proof that a well-developed sense of colour
occurs in some of the Arfciculata, 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. I^. Moseley to the effect
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 attain 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 Ants, Bees, and Wasps, and in Animal Intelliqenee.
t Quarterly Journ. Micro. Science^ New Series, vol. xyii, pp. 19-22.

G 2

100 MENTAL EYOLUTIOX 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
5^ 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 H^eckel
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 greeiu 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 enquire, by means of a table of questions
addressed to educated Europeans in all parts of the world,
whetlier 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 wliich is at once trust-
worthy and available. But in saying this I do not intend to

* Colour-sense^ Chapter X.

SENSATION. 101

dispute the 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 a?stlietic 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 liarmony 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 way 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
some 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-efi'ect of warming or cooling a portion of the skin
remains, the temperature-sense of that portion is altered in

102 MEXTAL EVOLUTION IN ANIMALS.

such 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 colours, and vice versd. So, too, it is
with simultaneous contrasts. It is well known that if a
small colovnless 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 fceinperature,
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 diiferent
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
l)lind 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 tliis 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 havincj the lowest and not the hi^diest 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 grow^th 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 w^alls. 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, a gam, the earliest sign
of commencement consists in a similar pitting of the general
integnment, bnt 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
I Hseckel, " the general conclusion has been reached that in
' man, and in all other animals, the sense-organs as a whole
ari^e in essentially the same way, viz., as parts of the external
integument or epidermis. The external integument is the
origiual 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 chfferentiations
of the general sense of toucli.

* Science and Culture^ &c., p. 271.

PLEASURES AND PAINS. 105

CHAPTEE YIIL

Pleasures and Patns, Memory, and Association of Ideas.

In the diagram I have represented Pleasures and Pains as
occupying in their hrst 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 ot
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 u
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 stimulatioQ. 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 Psycholoqy and Physiological ^Esthetics, in both
cases the chapter on " Pleasures and Pains."

106 MEXTAL 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
oi'ganism," 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 wdierein
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

PLEASUEES 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 hurtfulness, as
well as between the amount of pleasure and tlie degree of
tvJwlcsomeness* As Mr. Allen observes, " nothing can more
thoroughly militate against the etticiency 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 j)ainfulness 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
th'ose 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 cravings
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 j^ut it in a simple form,

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

108 MENTAL EVOLUTION IN ANIMALS.

"^ tlie 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 taste 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 tlien being actually disintegrated by the
direct or indirect action of the irritant."

Now if the doctrine before us is found to apply generally
f; 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 the 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 j)leasure,
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 guidance."

PLEASURES AND TAIXS. 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 tliis adjustment or corre-
spondence, the zoological principle of the survival of the
littest 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 liarmful
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, wlien 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 lono-
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 the 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 disagjreeable to consciousness, althouc^h
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 rationale 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. The latter consideration disarms any criti-
cism Avliich 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 cTetre
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 diagram 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 A^Titten, M. Ptibot has published his excel-

* On " tlie Physical Basis of Mind."

112 MENTAL EVOLUTION IN ANIMALS.

lent work on the " Diseases of Memory," wliicli has now
been translated, and forms a member of the International
Scientific Series. In this work M. Eibot deals fully Avith 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 should 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
my chapter above alluded to with the first chapter of M. Eibot's work.

MEMORY AND ASSOCIATION OF IDEAS. 113

curious fact to hold in the case of muscular tissues of various
animals, from the Medusa? upwards.*

Again, I concur with M. Eibot in his opinion that the iy
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, hut the formation among them of determi-
nate associatio7is 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."

Erofound, however, as our ignorance unquestionably is
concerning the physical substratum of memory, I think w^e
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 gans^lionic friction. And
this view is confirmed by the large and general fact noted in

* See " Coneludiug Obserrations on tlie Locomotor System of Medusa?,"
Fhil. Trans., Pt. I, 1880; and on "Modification of "^Excitability," &e.,
Froc. Foy. Soc, Nos. 171 and 211. Also, Journal of Anatomy and Physio-
logy, Tol. X. Another equally good instance of what may be termed proto-
plasmic memory 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., -nherever
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 memorj of its occurrence.

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-effect 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 the 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, Qrundziige der philosophischen Psychologie, 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 Eeaumur, ' Entomology,'
vol. i, p. 391) that larv?e 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
tlie 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 filled
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

H 2

116 MEXTAL 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 difticulty 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 takes its place, this emerges into
consciousness as a feeling that is not familiar. And whether
such feelings of familiarity or unfamiliarity arise in the
experience of the individual or in that of the species, makes,
as I have said, no essential difference either in the physiolo-
gical or in the psychological aspect of the case.

As showing how close is the connection between here-
ditary memory, or instinct, and memory individually acquired,
I shall briefly state some very interesting experiments which
were made by Professor Preyer on newly-hatched chickens.
He laid before a newly-hatched 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 tlie

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 tln^ee substances, and after the lapse of an
hour replaced them. The cliick 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 ]\Iemory —
for the chickens which first pecked at inedible objects in tlie
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, wliether 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.

118 MEXTAL 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 shaU do so now, notwithstanding^ the disadvantao-e
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 difficulty in dealing with the faculties of Mind in the
probable order of their evohition, 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 shall 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 convenient adjectives, 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 ]\Iiricl) 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 coliere 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 tlie 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 iMrceived ; 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 be 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 being 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
bave been written backwards by the left hand, and even tbe hand-writing can
be recognized on holding the paper before a mirror. As the left hand may
never have performed this feat before, and cannot perform it unless the right
hand is working simultaneously, the case looks like 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 rnind 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 o& 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 Intellect, 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 frord 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, w^ould
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 classily 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 wdien 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.! 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, J we must conclude that a dim power

* Loc. cit., p. 42.

t Animal Intelligence, pp. 28-9. t -Z'5?(/., p. 25.

122 l^IEXTAL EVOLUTION IN ANIMALS.

of memory is also present in the division of the Mollusca.
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 Mollusca 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. J

Seeing that memory in various stages of development thus
unquestionably occurs among the Mollusca, 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 shell 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 th«
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 Ibid., p. 27. % 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. Nevertheless, 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 wdiere 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- w^ asps carefully teach-
ing themselves (by taking mental notes of landmarks) the
localities to w^hich 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 w^ork — viz., for Beetles,
pp. 227 — 9, for Earwigs, p. 229, and for the common House-
^y, 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 " Memory," 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 Eeptiles 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,ir and the sound of a clinking collar after an interval of
three years ;1 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. f Ibid., pp. 254-62.

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

II Ibid., p. 330. IT Ibid., p. 438. ** Ihid., p. 387.

ft Ibid., pp. 485-98.

PERCEPTION. 125

CHAPTER IX.

Perception.

At the level marked 18 I represent the rise from Sensa-
tion to Perception. By this term I mean, in accordancef
with general usage, the faculty of cognition. " The contrast'
between Sensation and Perception is the contrast l)etween
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 distinguished 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, wliich 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 Percej)tion, 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 uu 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.
All 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, the 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 |7/?6S 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 tliat 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 sufiiciently 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 aUude.

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 morphological 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 j|
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 ;f
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, whetlier 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 1
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

128 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 percej)tive 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 develojDment 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 filled 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 this, 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

PERCEPTION. 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 j)ast sen-
sation. Again, the power of discerning a change of milk
implies 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 w^e have seen the next phase
of memory to depend. And, lastly, from this 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 that 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
memories as this become so blended with our perceptions of
tlie 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 liigher 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 changesj are completely auto-
matic, they are on this account precluded from being regai'ded
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 recognition as distinguished from reflex 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
which heredity has played in forming the perceptive faculty

PERCEPTION. 131

of the individual prior to its own experience. We have
abeady 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. Tliis 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 wliich 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 " putf and
spit."*

Birds come into the world with better endowments of
perception than animals of any other class. For they are in
full 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,! 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. t See Animal Intelligence, pp. 256-7.

I 2

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 signalling the perception. That is to say, an electrical
shock being administered to one hand, and as quickly 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 x^^rt in a reflex action.-f-

Acts of perception in which different senses are concerned
occupy difterent 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 ^,

* Arcli.f. d. ges. Physiol., xliii, 526 (1874).

t Ibid., vii, p. 610.

X See Herman, Sandh. d. Fhysiol, Bel. II, Tli. 2, s. 264.

PERCEPTION. 133

and for sight y of a second.* The observations of Von Wit-
tichf, Vintscligau, and Honig-Schnied:|: show that the reaction-
time for taste varies between 0'1598^' to 0*2 3 51'' 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 0'16 V. 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 sii>-ht, 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 . . , . 0*1139''

Electrical shock on left hand . . . . . . 0"1276

Sudden sound 0-1360

Electric shock on forehead. . .. .. .. 0"1370

Electric shock on right hand . . . . . . 0'1390

Visual impression from electric spark . . . . 01 506

Electric shock on toe of left foot . . . . . . 0'1749§

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 tc 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 sliows, 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 PhijsioL, 1^68, p. 657.

t qt. Ret. Med. (3), xxxi, p. 113.

X Arch.f. Anat. und PhifftioL, x, p. 1.

§ Pfiiiger'sArchiv., Bd.'VII, p. 620.

134 MENTAL EVOLUTION IN ANIMALS.

ception.* The last-named author found j that an exposure of
§L- 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 tlie skin, rigM or left foot
stimulated by an electric shock ; signal to be made in one
case only 0'066"

Dilemma of visual perceptions between two coloui's, 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 tlie 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 tlius be seen that the time
required for the act of meeting a dilemma is from -J- to ^ 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. Fhysiol., Bd. TV, p. 329 ; Monatsher. d. JSer. Acad.,
June, 1871.

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

X Archiv. f, d. ges. Physiol., 187^, pp. 298-380.

PEECEPTION. 135

Localization by sight . . . . . . « . 0*011''

Distinguishing colour . . . . . . . . 0"012

Localization by licaring (least interval) .. 0*015

Distinguishing pitch (high notes) . . . . 0'019

Localization by touch . . . . . . . . 0021

Distinguishing pitch (low notes) . . . . 0'034

Localization by hearing (greatest interval) . . 0062

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.

Eeaction-time.

Kemarks.

0 1337

Rough, lively labouring-man.

0-3311

Lively in movements, but rather slow in apprehen-
sion.

0-9952

Infirm and not intelligent.

0-1751

Slow and deliberate in movements.

0 -2562

Slow and somewhat uncertain in movements.

0-1295

Slow and very precise in movements.

0-1381

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 shooting 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 Loc. cif., 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 the 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 sheet of paper what part of the underlying page
the marked paragraph occupied, I suddenly removed the
sheet 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 befoi^e. Meanwhile the first reader, the
moment after the book had been removed, wrote down all
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 1 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 b,etween
slowness of reading and power of assimilation ; on the con-
trary, when aU the efforts are directed to assimilatiu'^

PEECEPTION. 137

much as possible in a given time, the 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 sliows that tlie 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 reducino- the reaction-time. The deo'ree of
reduction which might thus be produced was itself made the
subject of experiment by Exner, who chose tlie old man
already mentioned in one of tlie above quoted tables as having
the unusually long reaction-time of 0-99o2''. 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 mnltitudinous and complex kind, is proved in
every-day life by the acquired rapidity with which bankers'
clerks are able to add np 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 fasliion 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.J 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 Hohert Soudin, voL ii, p. 9. Professor Preyer lias also
published some observations on this subject. f Ihid., p. 7.

X La durata del discernimento e della determinazione volition, Rivisti di
Fllos. Scientif., I, p. 2. § Mind, No. XXX.

PERCEPTION. 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 jj

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

140 MENTAL EVOLUTION IN ANIMALS.

Perception arises out of Eeflex Action, Eeflex Action out of
Perception, or whether tliere 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 opei^ation 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

* Frinciples of Psychology ^ voL i, p. 446.

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
lio^ht which is mven out when such heat rises to redness.
Presumably, tlierefore, 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 Bonders 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
sjeneral fact, that throuo-hout the animal kinodom 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 dehning 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-
l 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 which 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 Chapters II and III.

IMAGINATION. 143

Bain, and others, who 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 sensation.*

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 11 '
comes in. Later on there arises association by similarity, V**
and from this point onwards Ideation advances by abstrac- /"
tion, generalization, and symbolic 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 ll
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 higlier phases
of the idea-forming powers which we may conveniently in-
clude under the general term Imagination.

Now, 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

* Tlius, Mr. Spencer says, " The idea is an imperfect and feeble repetition
of the original impression . . . There is first a presented manifestation of the
riyid 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 occtipies 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 n-hich I disagree with
him touching the earliest stages of memory — or those before the advt nt of
the association of ideas. Only I may point out tliat 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.

144 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 hai^e 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 runs
on in a continuous stream when all tlie 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 tlie diagram wliich 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 Keflectio]!. 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 w4th
another, and there can be no harm in adopting it if we
remember, what I desire ahvays 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 f¥infln[rtimi1imTi J^L^
Such, however, is not the case. For, althoucrh it is true that,
if we were able to imagine every abstraction, Conceptualism
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 \\A^
Eeflection, I am careful to keep well within the lines of
Xominalism.

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

146 MENTAL EVOLUTION IN ANIMALS.

the octopus which followed a lobster with which it had been
fighting into an adjacent tank, by laboriously climbing up
the perpendicular partition between tlie 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 Intelligence " 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 p)late, 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 tune 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 Intelligence, pp. 122-40, and 181-19.

IMACxIXATIOX. 147

appetite ; the animal tlien becomes bold by necessity. He j
even runs to meet danger, knowing [i.e., forecasting by j
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 sufficient number of objects, he becomes the sport of an
illusory system, which may lead him into infinite mistakes,
although perfectly consistent with the princijdes which have
taken root in his mind. He ^^'ill 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 awaitino- 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 tlie fox and wolf in eluding the hounds is also evi-
dence of a rivid imagination. In addition to the cases of this given in
Aniynal 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 : —
" jS'ear the south coast of San Francisco a farmer had been much annoyed by
the loss of his chickens. His hounds had succeeded 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 obliterated by the swell. When, finally,
lie had gone far enough, as he supposed, to destroy the scent, he turned
inland."

K 2

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 hut still more deadly pain which it
fears at the hands of the man.

Coming now to Imagination of the third degree, or that
which 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 liigher animals.
h 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 Loioer 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 Cu^der, Jerdon,
Houzeau, Bechstein, Bennet, Thompson, Lindsay, and Dar-
win.* Thompson 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 MammaHa 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
s\vdmming ; 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 tliat occur in other animals as in man, in
canine rabies, for instance, as in human hydrophobia." J On
tliis subject Fleming writes : — "It {i.e., a rabid dog) aj)peared -
as if it was haunted by some horrid pliantoms. ... 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 ;
Facidtes-Mentales des Animav^, Sfc., tome ii, p. 183 ; Mind in the Loicer
Animals, vol. ii, p. 96 ; Passions of Animals, p. 60 ; and Descent of Man,
p. 74.

f According to Pierguin, Guer, Elam, and Lindsar, dreaming in animals
may be so vivid as to lead to somnambulism (see Lindsay, loc. cit., p. 97,
ef seq.). Thus Guer 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 EVOLUTIOX IN ANIMALS.

at the vacant air, as if pursuing something against which it
had an enmity." And, indeed, this peculiarity of heing
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 eflect 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."

Pierc|uin 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 she 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 animals present Imagination of what I
have called the third order. This class of facts consists of

* See Youat, On the Dag, tinder Eabies.

t Traite de la Folie des Animavix^ Sfc, tome i, p. 93.

IMAGINATION. 151

animals showing by their actions tliat they have in tlieir
" 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 with the sluggislniess and lack of
energy on tlieir 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, tlie 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 dano-ers and fatigues of
hundreds of miles of travel for the sole purpose of returning
to the scenes which occupy tlieir 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 ihe 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
which the animal is strongly attached. I have myself
known a case in which a terrier of my own household, on the

* Thompson, Fassions of Animals, pp. 64-5.

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 ca^^se
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
t'lrouoh what I have called the first three stages, so as to
arrive 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
jDroved 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 aljsurd to accredit a moUusk
with imaginatiun, 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 habitual 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 wdiich 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 imao-e, 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.) AVith a stiU 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 Keptiles, 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
third degree — it being I think highly 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 tliat in the soul
Are many lesser faculties tliat 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.

I Before taking leave of Imagination there are two branches

I of the subject which I should like briefly to consider. One
I 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, et seq.

IMAGIXATIOX. 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 tlie 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
in 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 ob\dously
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
giinning, 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 oliject, and
w^ould bring it with renewed manifestations of friendliness.
Some kindred state of mind it is wdiich, 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. Tlie 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
w^orrying 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.

" N"ow in this and all my other experiments I have no
doubt that the behaviour of the terrier arose from his sense 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 tlie same oppressive and alarming sense of the
mysterious which unciilturecl 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 tliat the sense of the mysterious
in this animal was sufiiciently 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 was 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 wdiich 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 wdth 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 alter 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 w^ith 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 wdiining 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, wdien 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 behaviouj-,

158 MENTAL EVOLUTION IN ANIMALS.

i.e., by the violation of liis 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 w^as at a distance from home. But the keeper,
who had a large experience in the training of dogs, assured
me if I allowed this one to be taken to the 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 the 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 sucli -would hare been the case, however, I have little doubt, for
on one occasion when a number of apples were being shot out of bags upon
the wooden floor of an apple-room, the sound in the house as each bag was
shot closely resembled that of distant thunder. 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 him, and on again returning
to the house he listened to the rumbling with all cheerfulness.

IXSTIXCT. 159

CHAPTER XI.

Instinct.

Definition.

I 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 1 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
circumstances by all the individuals of the same species."

Eef erring 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-] 7.

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

160 MENTAL EVOLUTION IX ANIMALS.

stimulus to an action apparently instinctive, ex liypotlusi the
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, aud 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. Eeflex 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. 161

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 l)y 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 grasp 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 which 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 betw^een 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
sinsjle 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
wdthin 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 tw^elve days old one of my little proteges,
while running about beside me, gave the peculiar chirr
wheieby they announce tlie approach of danger. I looked

PERFECTION OF INSTINCT. 163

up, and Leliokl 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,
wdiich, if anything, might be acquired by imitation — for a hen
wdth 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 wdien 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.E.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 dexterity, I may mention
that on placing four ducklings a day old in the open air for

L 2

164 MENTAL ETOLmOX IX AXIMALS.

the first time, one of them almost immediately snapped at
and e^^nght a fly on the Tring, More interesting, however, is
the deliberate art of catching flies practised by the tiirkey.
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 them. In doing
this, its head could be seen to shake like a hand that is
attempted to be held steady by a visible eflbrL 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 sufliciently 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 manrmals. He found, for
instance, that new-K">m pigs seek to suck almost immediately
alter birth. If removed twenty feet from the mother, they
wri^le 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 distinguishable 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 kinens 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 " Xature."

*•■ ApropiiS to what Mr. Spalding says about the early age
at which the instinctive antipathy of the cat to the dog
tecomes ajiparent, 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-

* Sature, toL si. p. 507.

FEKFECnOS or ISSTISCT. l&^t

house which contained a doe rabbit with arefj jonng Uasdij,
I turned loose a ferret. The doe rabbit left her jomig ones,
and the latter, as soon as thej amdled die femt, h^m to
crawl about in so enexgedc a wiaiww»r as to leacre no doubt
that the cause of the coimnotioii was fear, and not merefy
the discomfort azisii^ from the temporsDj abBeuce ai Iht
mother."*

With reference to the instinctiTe endowmentB of tins
kind in kittens, I may also qiiote die kXkmJag, wUdi I find
amon^ ^Ir. Darwin's iiSS : —

"the many cases of inborn liear or ferocitj in joung
animals direeted towards porticidar objeets, as wdl as tlie
loss of these indiTidiialized paaaoos, seems to me extreme^'
corions. Let anj one who doubts their erjatenfle gire a
mouse to a kitten taken eazlj from its mother, and wfaieh has
never befose seen one, acd obserre how soon the kittea
growls with hair erect, in a mannfa- whc^^ diiieteiit from.
when at play or when fed with <Rdinazj food. We
suppose that the kitten has an inbnn picture of a
graven in its nmL<L But, as when an old Jimitgy smits
eagerness at the very first ssund oi. the hcHn, we most si^
pose the old assodadcms excite him afanost as inatantiy as
when a sudden noise makes him start, so I imagiiip, witli tibe
diflference that the imafflnatioa has become hoeditaij jnatiead
of being only fixed by habi^ the Vi*#p" witiioiit any definite
antidpation trembles witJi exdtonent al the smdl of die
moose.''

The only odier ebaenaliflns made by Mr: Spalding which
It is desiral^ to quote are those bf wfaidi he proied expm-
mentally that yooi^ birds do not require; as was otdimnihr
supposed, to be taught to ftj, but fly instinetivi^. This fact
was proved by keefing yoon^ swaDows csged m^diey were
fled^d, and then aDiiwiii^ than to escapa Whoi we cob-
sido- the complicated mnscalar eo-ogdination requited far fli^t,
the fatt that yov^ birds when fledged should be able to ity
at the first attempt eenstitiites anodber remarkaUi
of the perfection of instincts Of oomae it is true that
ordinary circuinstaneeB the parent birds enoonage
progeny to fly, but the ^cpezimeiit? in n--^^- n Aaw tliat
such eneouragemeiit, or tuition, is z : : z- enaUe the

young birds to piactise the art^

But it is amffl]^ insects that we ne^: -^1: _:^ r>^-

* Smimrm, -wtA, xL p. df-L

166 MENTAL EVOLUTION IN ANIMALS.

markable cases. Thus, to give only a few. Eeaumur and
Swanderdam assert that a young Bee, as soon as its wings are
dry, w^ill 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, wdiich
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 oft spring. 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 spacp
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 tinie."|

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 fuUy-

* Kirbj and Spence, loc. cif., vol. ii, p. 470. t Ibid., i, p. 357.

X Sir J. Lubbock, Address to Entemol. Soc, 1882.

nirERFECTIOX 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 Hfe as a larva and its new life as an imago, is as great
as the difference between tlie 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 (|uite as remarkaljle 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 this 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 carnarict) deposits its- eggs in the
flowers of the '' carrion plant " (Stapelicc hirsutci), the smell
of which resembles that of putrid meat, and so deceives the
fly.* Similarly, the house-fly has been observed to deposit
eggs in snuff* t

Again, the Eev. Mr. Bevan and Miss C. Shuttleworth,
write me independently that they have seen wasps and bees
visiting representations of flowei^ upon the wall-paper of
rooms ; and Trevellian saw the same mistake made by the
sphinx-moth.j 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, F.E.S., informs me that he has noticed
honey-seeking insects mistake for flowers the bright coloured
salmon flies stuck in his hat wdiile fishing ; and Mr. F. M.
Burton, ^^Titing to " ^^ature " (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 naturahst Couch observed a

* E. Darwin, Zoonomia, i, § 16, art. 11. Also Kirbv and Spence, loc. rit.,
ii, 469, who state the fact on the authority of Dr. Zinken.

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

168 MENTAL EVOLUTION IN ANIMALS.

bee mistake a sea-anemone {Tealia crassicornis), whicli was
" covered merely by a rim of water," for a flower— darting
into the centre of the disk, " and thouoh it struo-oled a o-ood
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.t " 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. riifa) carrying pupa
skins, with a great and apparently useless exj)enditure 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 flrst 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.:j:

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 in 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 Hai'vesting Ants and Trap-door Spiders, p. 37, et seq.

IMPERFECTION OF IXSTIXCT. 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 escape 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 enouo-h in the case of tamed animals
(which when again " 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, but 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 whicli 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 unhoocled
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

IMPERFECTION OF INSTI^XT. 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 connectioti^
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 hcitching, took to the
eggs, sat on them, and brought out chicks.' Says Willoughby
(in 'Piay'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 office,' says Baptista Eosa (' Magia
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.' Eeaumur (' Art de Faire Eclore,' tom. ii, p. 8)

172 MEXTAL EA^OLUTIOX 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 w^as confounded, and became mixed wdth reason or
experience : for it tried repeatedly to suck three or four other
kittens 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 Ostrich (S. Breutnall, Port
Elizabetli, 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 liad 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
sino-ular aberration of instinct had become a fixed delusion,
whenever the bottle was thrown or placed in the yard — no
matter wdiether it lay horizontally or was placed upright —
the same ridiculous scene was enacted ; at that moment the
pigeon came flying down with 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 tlie exhibitions of erotomania, infanticidal mania,
&c., which occnr 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 wliich 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 tliey 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 v/hich 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. Prol^ably this is the explanation, altliough 1 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 (cliiefly domestic work, for which they are
led by their foraging sisters) ; so it is possible tliat in the
hive-bee the drones were originally useful members of the
community, and that they have lost their primitively useful
instincts. But Avliatever 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 Hagrant 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 daring 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 efforts, 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 says 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 occut, 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. Xow 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
I'ace — 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 des Kindes, Leii>zig, 1882, pp. 166-7.
t Ibid., pp. 167-75.

ORIGIN AND DEVELOPMENT OF INSTINCTS. 17

CHAPTER XII.

Instinct (continued).

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 intelHgent, 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 for any other purpose, adopted a similar habit, tlie
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 >
efiects of habit in successive generations,, actions which Avere
originally intelligent become, as it were, stereotyped into per-

* Quoted from my own article on "Instinct," in the EncijclopcBdia Bri-
tannica.

178 MENTAL EVOLUTION IX 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
system 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 w^ay 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 a '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, then 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 ^d 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 tune,
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 rioiit within before drac^s^imy 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 agaiu 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. Kaf., 4 ser., tome vi, p. 148. "With respect to Bees, see

M 2

180 MENTAL EVOLUTION IN ANIMALS.

" In another way we perhaps see the 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
tliat 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, voL i, p. 497. For the hammock caterpillar,
see Mem. Soc. Phys. de Geneve, tome vii, p. 154.

* Zoonomia, p. 140. f 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 schooboom, 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, unless 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 weU 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 wonderfully 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 " rhythmical 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 {Mental Physiology, p. 373), "What 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.

althougli every dog adheres to his particular attitude through
life. Nearly all domestic animals exhibit slight but indi-
vidually constant differences of movement when 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 9.vidity, 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, wliicli is referred to in this
connection in Mr. Darwin's MSS.

t For example, the Nut-hatch 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
describes 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 Grolden Eagle builds in precipitous
crags of rock ; but Mr. D. E. Knox {Autumns on the S^ey, 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
sometimes 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
which 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 tlie twigs and lichens outside and the fine grasses which
invariably constitute the lining ; this has been more especially the case when
the bird has selected 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

ORIGIN AND DEVELOPMENT OF INSTINCTS. 18:^)

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, Buchner observes, " one
ant will let herself be killed ratlier than let go the pupa
whicli 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 widgeon 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 herseK down upon the ground just

observed in the text, such instances might be multipUcd indefinitelj ; 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 Ibid.

ORIGIN AND DEVELOPMENT OF INSTINCTS. 185

Tinder the same roof, and in tlie same straw bed kept each
other warm ; and when the dog was taken to the field, the
lamentations of the choose 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-
trido-es and landrails. Such unusual cases amon^:^ 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 that " bands of the G-olden-crested
Wren may frequently be observed in winter consortin;^ with bands of the
Coal-Titmouse, and in a less degree with those of the Long-tailed Titmouse ;
while parties of Eedpoles 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 ANLMALS.

same trick under the same frame of mind, and wliicli 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
Eev. 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 j)u,rely
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 differcDt words in Variation of Animals and
Plants, &c., ToL i, pp. 450-1.

t Here, however, I may remark that I have noticed several Syke terriers
perform these movements while begging, so that the action seems to be due
to some race-distinction of a psychological 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 tlioroughly sense-
less psychological peculiarity. I refer to the instance which
was communicated some years ago to Mr. Darwin by Dr.
Huggins, F.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 broucrht the doii:, 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
liim. 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. JSTicholls, 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 w^onld 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
(thougli 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 aU 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 MaUe
asserts that these different paces have been acquired since
the time of the Eoman 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.

f After giving numerous references on this point in a footnote,
Mr. Darwin concludes tlie latter thus : — " I may add that I was formerly
struck by no horse on the grassy plains of La Plata having the natural high
action of some English 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, &c., 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 few 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 cliapter, 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. Tliis
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 woidd 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 ;";[:
the biscacha, which " almost invariably collects all sorts of

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

I Some years ago the Ratels 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 probably develope a
true instinct of turning somersaults analogous to that of the tumbler-
pigeon.

J I have frequently noticed a similar 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 TV, — viz., that
such habits may vary, and that vjhen they vary the variations
may he 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 undersjoes the variation of becominsr
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.

Prom 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 w^e 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 w^ay of proof. If among a number of meaningless habits,
all more or less hereditary and more or less variable, 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 tliis instinct began in , J|r
habits adapted to the protection of the eggs, it is certain that ^ '^
it cannot have begun with any intelligent reference to hatch- jJ'*jJ\
ing them ; and it is no less certain that before the instinct Y^*^
attained its present degree of perfection, it must have passed f,J^
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 tly 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. Fabre
has observed that Bemhex inclica lays an Qg^^ in a chamber,

* A Monographic Revision and Sj/n->p.s-is of the Trichoptera of the
JiJuropean Fauna, 1881, by Robert M'Lachlan, F.R.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.

ISTumerous 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 propositions, 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,
yjlien frequently 'perfm^med hy the individual, hcconie autoynatic,
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 fir d.

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, altliough 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 oiu^ dis-
cussion, therefore, we shall now pass.f

Accepting, then. Proposition VI as beyond dispute, we
have here to substantiate Proposition VII, viz.. That cmtomatic 7
actions and conscious habits may he inherited.

Now we have already seen that this is certainly the case '

* Article " Instinct," Todd's Cijclo. of Anat., rol. iii, 1839.

t Mr. Darwin's MS points ont that persons of weak intellect are very apt
to fall into habitual or automatic actions, and 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, tliey are found to resemble automatic habits in showing 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 which 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 .... Hof acker, in Germany,
remarks on the inheritance of hand -writing; and it has been
even asserted that English boys, 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 cases of hereditary aptitude for music and painting. Also Gralton's
Hereditary Genius, for high mental qualities running in families, either in
the same or in analogous lines of activity ; and Spencer {Psychology, i, p. 422)
for race-characteristics of psychology in man. The effects of " good breeding "
or " blood " in bequeathing hereditary disposition and refinement have already

ORIGIN AND DEVELOPMENT OF INSTINCTS. 195

now to the more important case of animals, I shall give only
a few examples among almost any number tliat 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
i Qstance 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 sliow that the same applies to
the sense of modesty.

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

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

N 2

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
Sulivan, E.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 has
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 others 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
British 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. Rae, F.E.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.' "

ORIGIN AND DEVELOPMENT OF INSTINCTS. 197

played an important part, and at present we are confininfr
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- '
Gated 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. Paoes mi^ht 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
developmentof 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 wdth 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,
which dropped upon crossing the track of a Partridge, as its
male parent w^ould 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 '1 ein 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
great-grandfather w^as 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.":]: 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.

t Blaine, Rural Sports, p. 863, quoted by Darwin.

X Origin of Specie-t, 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 w^as 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.

CHAPTEE XIII.

Instinct (contimced).

Blended Origin, or Plasticity of Instinct.

From 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-
wise, 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 m 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.

BLEXDED OEIGIN, 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 furtlier 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 ujDon 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, Entomoloqif, rol. ii, p, 476. It is evident that
the -wearing of a web by a caterpillar adapted to the needs of its future 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 by experience what it is to be a crysalis.

t Loc. cit.

202 MENTAL EVOLUTION IN ANIMALS.

day ; in each 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 mouth 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 w^hich 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

* Tlie facts of tliis case have been told me by Dr. Eae, 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, hut 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 parti cidar case, the historical priority,
I may in future neglect ta entertain the question of such
priority ; without considering whether in tliis 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 under 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,
^vrite 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 bavSe : whence Huber w^as 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 wliich 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
la.rger, and those on the concave much smcdler than usual ;
the former having three or four times the diameter of the
latter. But this was 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

* Kii'bj and Spence, loc. cit., pp. 485-495.

206 MENTAL EVOLUTION IN ANIMALS.

a transition takes place from one class of cell to the other, a
complex geometrical problem arises how to imite 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 hexao'ons to larc^e hexao'ons, or vice versd, is
effected. On this subject Kirby and Spence remark :
''' Eeaumer, 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 cells, 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 everj/ 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, w^e have concerted variation in the mode of
constructing the cells of a normal and definite kind, and we

BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 207

find that in this case the variation is determined by an event
(the o\dposition 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 undeviatincr
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 iu a higher degree by some other i
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 tiiree
days, until they had built supporting pillars of wax. " Kow,"
as Mr. Darwin observes in his MSS, " such an accident as
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 MEXTAL EVOLUTION IN ANIMALS.

a fretted mass," wliich 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." t

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.J

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

* PMl. Trans., loc. cit.

f Origin of Species, p. 228. It is interesting in connection witli these
facts to note liow singularly well tliey happen to meet a criticism of Kirby
and Spence, wliicli was advanced before tbey bad been observed, with the
object of discrediting the view of instinct being modified by intelligence.
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 doixbt of their having
been guided by reason." It is curious that this demand should so soon have
been met by so apposite an obsei-vation. Doubtless mud is not so good a
material for the purposes required as propolis, but as soon as the bees are
fm*nished 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 case should serve as a warning against the use of the ques-
tion-begging argument, which where any degree of evidence is presented of
intelligence compounded with instinct, forthwith raises the standard and says
— ShoA\- us an animal doing this or that, wliich would be still more remark-
able, and then we shall be satisfied.

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

BLENDED ORIGIN, OR RLASTICITY OF INSTINCT. 209

to meet them by intelligent adjustment, wliich, if continued
sufficiently long and aided by oelection. would pass into true
instincts of building combs in new directions, of support-
ing combs during their construction, of carding tlireads 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 wliich 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.
AVe 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 wliich 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 arcliitecture : —
" The characteristic trait of the • uilding of ants," says Forel, " is the almost
complete absence of an unchanireable moiiel 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
by others when they understand its plan" (p. 129).

t Transactiuns 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
chanoe of instinct, and in America this chancre 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
otlierwise. 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 tlic Bank Swallow.

. . . Some of them, like the Purple Martin and the
Violet-green Swallow, are still surviving their apprenticeship
under the new regime, which the settlement of the country

BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 211

lias brought about. . . . Those whose acquired habits
have become thoroughly ingrained are now pretty constant in
tlieir 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,
w^hen 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 Valletf, pp. 292-4. + Comptes Rendiis, Ixx, p. 492.
X Ihid., Ixxi, p. 7*^. In the first edition of Animal Intelligence I quoted
this statement of Pouchet without knowing that it had been questioned.
§ 6ee Geol. Journ., vol. iv, p. 325.

0 2

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 phcenicohea) inhabited exclusively the palm trees
in a few districts of the island. A colony then established
themselves in tw^o cocoa-nut palms in Spanish Town, and
remained there till 1857, when one tree was blown dow^n, and
the other stripped of its foliage. Instead of now seeking out
other palm trees, the swifts drove out tlie 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."*

Turning 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 tliese 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 tlie present connection, for otherwise they
might rather be taken to exemplify non-intelligent variations
of instinct with wliich w^e 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-
eeclins: and also for other instances.

+ The yearning for progeny which arises from the parental instinct being

BLENDED ORIGIN, OR PLASTICITY OF INSTINCT. 213

" Spanisli 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 tlie 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 oft'
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 plasticity of instinct. Three years ago I gave a pea-
fowl's e<y^ 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, for, 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 pecuKar 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 other
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 accui'ate 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 birds in a state of domestication which are about to be given
in the text: —

" In July, 1878, I found a wren's nest A^-ith young birds, which were being
fed by a wren and a sparrow. I made sure that the young birds were wrens,
and 1 noticed that the sparrow continued to feed them after they had left the
nest. The behaviour of the two birds was very dissimilar, the vrren 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 four months, and had then to be forced off in order to save hei- life.

214 MENTAL EVOLUTION IN ANIMALS.

being prolonged ; for a pea-chick requires sucli care for a
very mncli 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 montlis 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 botii
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
])y 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 followincp instructive case from Jesse's

" Gleanings,' 't because it has been independently and uncon-

* Nature, Oot. 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."

^ly correspondent, Mrs. MacFarlane, also gives me another
closely similar but even more remarkable case, which was
observed by her sister. Miss IMackillar, 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 staudine^ on its maroin, 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 givins:
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 ofl"
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 tliat 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 chickens. While engaged in tliis process,
however, she used frequently to stop and look witli 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 tly off the nest
suddenly with a loud scream, an action which Avas 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, I 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 wdth the other, however, the two mammalian
mothers should have littered on the same day."

Lastly, turning to the Mammalia, a friend of the Kev.
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 displayhig
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 Nat. Hist, of Mankind, i, 102.

218 MENTAL EVOLUTION IN ANIMALS.

" Some years ago the late Hon. Marmaduke Maxwell of
Terref^les. 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, vol. xx, p. 77.

VARIATION OF INSTINCT IN DEFINITE LINES. 219

CHAPTER 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, but 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 (a^s 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 dc 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 defiect 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
{ iiidwiclual 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
their 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-

VARIATION OF INSTINCT IN DEFINITE LINES. 221

bees themselves boring holes. Tlie 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 wliich I have made,
that they were guided 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 lmml)le-l)ees cutting
the holes, and understood what they were doing, and imme-
diately profited by tlieir labour ; or that they merely imitated
the liumble-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 tliere can be little doubt that the manner of
attack of the English Bull-dog is instinctive (Rollin, ' 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. Ross, * 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 cry when a hawk

222 MENTAL EVOLUTION IX 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-finch, 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, J and Bureau 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 birds
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.1[

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.ft
Of course such facts are notorious as regards the Mocking-
bird (Turduii polyglottus), and also, at least when in a state

appears serves to alarm tlie cliiekens, tliougli tlie latter are rot aborigines
of the country." And many similar instances miglit be given.

* Illustrations of Instinct, p. 113. See also Beclistein, Siuhenvogel,
4tli ed., p. 7.

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

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

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

•[[ Bulletin of the Buffalo Society of Nat. Sc. 1881, j^p. 23-6.
** Loundoun\s Mag. Nat. Hist., vol. iv, p. 433.

tt Loc. cit., vol. i, p. 204 ; also in 4tb 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, -nhimbrel, herring-gull, quail, and corn-
crake, -while Professor Newton tells me that at Cambridge he has heard the
starhngs very perfectly imitating the quacking of ducks.

VARIATION OF INSTINCT IN DEFINITE LINES. 223

of confinement, of parrots, jays, jackdaws, and starlinp^s ; and
these facts are rendered more remarkable from the additional
fact that none of these birds have any proper son<^ 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 tliose singing-
birds which are most apt at learning tunes. For Bechstein
sa)^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 whicli these birds display is
unquestionably that of uttering articulate words. This
subject will require to be considered more fully in my next
work. Meanwiiile it is enough merely to mention it with
reference to the w^onderful 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 wliich
belonged to himself, and which from the time of its birth
was brought up with a kitten six montlis its senior. For two
years the terrier had no association with other dogs. Soon

* Anns, des Sc. Nat., 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 paws 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. Eouth,
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."J 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 tlie 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., tom. xxii, p. 388.

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

X Mis? Mitford's Life and Letters, voL ii, p. 277.

§ Nature, vol. viii, p. 79.

il See Annls. and Mag. of Nat. Hist. 2nd ser., vol. ii, p. 364; and
Stillingfleefs Tracts, p. 350. In regard to Lambs, see Youatt on
p. 404.

VARIATIOX OF INSTINCT IN DEFINITE LINES. 225

among animals, but it may be said in general that, as the
faculty 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, us 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 eigliteen
months, after which it remains stationary for a time, and is
then of much service in developing language.* With growing I
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 thino- is conspicuously observaljle 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 Preyer, loc. cit., pp. 176-182, where a number of detailed obsei'-
vatioiis 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 perform-;
this action before tlie child. [This action see ns 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 leaimt, 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 wliile awake-,
— e.g., blowing with the mouth. Later still, complicated imitative movements
are performed for mere amusement, as is apparently the case with monkeye.

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. WalLice, in his Natural Selection,
that" the nidification of birds is due to the young b rds consciously imitating
the structure of the nests in which they have themselves been reared — the
characterislic nidification of each species of bird being thus maintained. I
have advanced in Animal Intelligence sundry general considerations, which I
thought sutficient to negative this theory on a priori grounds ; but since theii
I have found among Mr. Darwin's MSS a letter which describes the results
of the test experiment which Mr. Wallai-e himself suggests. This experiment
is to rear young birds from the egg in an artificial nest or incul^ator 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 wliich 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."t

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 mnke their
nests because they have been themselves reared in one, the less inclined 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 • ox, 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 sufficient for the purpose. I feel convinced nest building is a true
instinct."

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

t jUaff. Nat. Eifit., vol. ii, p. 402.

X Descent of Man, p. 73.

VARIATION OF INSTINCT IN DEFINITE LINES. 227

laboriously given ; * and the only use it can be is that of
developini^ 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 tlieir 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."

Aijain, althousjh 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 Qroose e^i^s. Tlie 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. . . . The 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.

1 Yoitatf on Sheep, p. 404 ; and Anns, and Mag. Nat. Hist., 2nd ser.,
vol. ii. p. 3G4, &c.

p 2

228 MENTAL EVOLUTION IN ANIMALS.

being intentionally instructed by the old, but tliey 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 pareats is subsidiary.
I shall therefore give a few more instances to show that
many instincts (usually those of obviously secondary origin)
are tirst 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 pnt themselves
into a position to inflict the death wound, engage in conflict
with rats ;" yet they liad 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. Dar\\in says in his MSS that in 1840 he saw some
chickens which had been hatched without a mother, and

* Amis, and Mag. Nat. Hist., \o\. 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 1 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 gravity, would have been specially taught
by instinct ; but this is not so, for 1 was most positively
assured tliat 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, <j^
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 effects 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 dqniestication 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.

Prom the 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, w^e 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 w^e do find.

Taking first the case of the impairment or loss of natural
instincts, I have already alluded to the striking example
supplied by the hereditary tameness of domesticated animals.
More, 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 tlie aid of selection, or to primary
means unassisted by secondary. In this connection I ad-
duced the cases of the Rabbit and the Duck ; I shall now
adduce the cases in whicli artificial selection has probably
assisted mere disuse in obliteratinu; 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, oi'
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 themselves 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 sufficiently 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 founds
incurable in dogs which have been brought home as puppies

* Zoological Journal, p. 320. f Origin of Species, p. 211.

232 MENTAL EVOLUTION IN A.NIMALS.

frDm such countries as Tierra del Fuego and Australia, where
t le 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, ^o 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 whicli 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 o'enerations 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 evideiK?e on tliis point is given, from wliicli 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 poultry became quite furious.' So again Captain FitzEov says that
not one of the many dogs procured from the natives of Tieri'a del Fuego and
Patagonia which were brought to England could easily be prevented fi'om
indulgence in the most indiscriminate attack on poultry, young pigs, &c.'
(Colonel H. Smith, on Boffs, 1840, p. 214 ; and Sir J. Sebright, on Instinct,
{). 12. Also Waterton's Essai/ 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 persisted in killing poultry and ducks whenever he got loose.

t Stuorn, Ueber Racen, &c., s. 82.

DOMESTICATION. 233

T.astly, 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 w^hat 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-
iluence 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 witli selection. And
here I shall confine myself to the species of domestic animal
in which these elfects 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 tliis 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, rollino- in filth, turnino- 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.

:|: La INIalle says that it is not until dogs are ten or twelve months old
that they be^in 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 tlie instincts
of wildness, fierceness, attacking poultry, and so on, which have been so
completely eradicated by liuman apency.

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 ownersliip
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, till 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 lly 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, 1 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 tlie 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 tind that if a master consigns his dog to the care ot
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, 1
tliink, improbable that what appears to be the acquired in-
stinct of barking is, as it were, an offslioot 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. DarwiU' 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 cannot, 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 ^yell, 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 chasing 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 cliief 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 sooietimes to be the

* " With respect to the inherited tendency to back, see St. John's
Wild Sport of the Highlands, 1846, p. 116 ; Colonel Hutchinson on Bog
Breaking, 1850, p. 144 ; and Blaine, Ency. of Rural Sports, p. 791. — Besides
the tendency to point, pointers inherit a peculiar mann-r of quartering their
;iround."

DOMESTICATION. 237

case with true instincts, he often profits by tliese 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 tlie 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

* rhil. Trans., 1S37, p. 3G7.

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 sgao 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 knov/ledge 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."

I 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 by man of such
special canine instincts as we liave now considered, we have
in them only, as it were, small details of the modification
wdiich 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 tlie greyhound or the
bulldog, than that he has implanted the no less remarkable
instincts of the pointer or the retriever ; but we sliould gain
a very inadequate conception of tlie profound influence which
he has exercised in moulding the mind of tliis animal were
we to confine our attention to such special cases as these.

If we contrast the psychology of " the friend of man "
with tliat of any of the wild breeds, we see at once, not only
that the animal has liad 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 proverlual to need special exposi-
tion. We have merely to observe that these qualities, so unlike
anything with which we meet in w^olves, 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 wdld animals we do not unfrequently
find a disposition to associate wdth members of other species,
even when no actual benefit arises from the association ; and
in this accidental or useless proclivity w^e may distinguish
the germ which in the case of the dog has been cultured into
what w^e 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,

* Handhuch der Physiologie, Bd. II, Theil II, pp. 282-3.

240 MENTAL EVOLUTION IX AKIMALS.

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 distinguisljable 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, althouo-h " anions^ 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 feelings 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 collie belonged to a man named Steele, w^ho 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, T 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 Abroad, p. 182, 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 slieep 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 publislied in the " Variation
of Animals and Plants under Domestication " (vol. i
p. 43) :-

'' 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 Euglish 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 a loosteriori proof of Proposition VII is now concluded ,
and with its proof our considerations on the origin and
development of instinct are drawing to a close. For 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 combined. 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. For 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
variability 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 the formation of natural
instincts.

LOCAL AND SPECIFIC VARIETIES OF INSTINCT.

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 fully 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 \j.
drawn from the facts of domestication with further evidence
drawn 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 i
animals in a state of nature instincts undergo transformations |
which are precisely analogous to those that they undergo

Q 2

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,
6 and 2nd the similar occurrence of specific varieties.

Local 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
I — 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 baUs
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, 1 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
chapter.

Again it is stated by Lonbiere, 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, Lasiiis ace7'lorii7ii, wdiicli on the plains is never

LOCAL AND SPECIFIC VARIETIES OF INSTINCT. 245

found to build under stones, while in the 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. l^ackard, jun., records
some observationsf which were made by the liev. L. Thomp-
son, whom he designates " a careful observer," of bees {A'pis
mellifica) eating moths which were entrapped in certain
flowers. 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 Phisia to suck the
nectar contained in their bodies ? Such a deOTee 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.J

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 sprting.'§ Bechstein
says that from many years' experience he is certain that in

* Animal Intelligeyice, p. 188, where see for references to Dr. E. Darwin,
Kirbj and Spence, and later writers on this matter.

t American Naturalist, Jan. 1880.

X 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.R.S., Lewis
Bod, and W. G-. Smith.

§ W. Thompson, in Nat. Hist. Ireland, vol. ii, p. 65, says he has obseiTcd
this, and that it is well known to sportsmen,

246 ME^'TAL 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
Ring-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 tlie 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. J 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. 323; see on different powers of singing in dif-
ferent places, s. 205 and 265.

t That this is the explanation is not merely probable a 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 VAEIETIES 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,t 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, T think, tends to confirm the statement of
Mr. Edward {Zool., p. 6842) that on the coast of Banffshire the house-
swallow presents a local instinct of building in caves and on projecting rocks.

t When house-sparrows build in trees — which thej 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. § Ihid.

248 MENTAL EVOLUTION IN ANIMALS.

delphia on February 18th, 1873, by Mr. W. K. G. Gentry. A

rodent popularly known as the Chickaree (Scimis Imdsonius),

which like most of its kind is normally herbivorous, has

{ adopted in the neighbourhood of Mount Airy a habit

j common among the Mustclidce, of climbing trees for the pur-

I 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

liabit 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
notahilis) 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 killing 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
tlie 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 I
parts of South Africa the hygenas 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 Eeport 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 tlie 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 : — " AVe found the beavers in numljers of which,
when applied to beavers, I had no conception." Therefore
I infer that since the time when Dr. Newbury's Pieport was
published, the number of the beavers must have been gi'eatly
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 eitlier 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 UUoa
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 the 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 variations 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, according to Eoulin (quoted by Dr. Carpenter in
Contemp. Rev., voL xxi, p. 311), the domestic cats in South America do not
make these sounds.

LOCAL AND SPECIFIC VARIETIES OF INSTINCT. 251

inhabiting a certain restricted area exhibits a marked depar-jj
ture from the instincts elsewhere characteristic of its genus, '
we can scarcely question that the departure is indeed a
departit7'e — 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 aiuay 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 tw^o genera.

" The only non-cuculine genus of birds knowm 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 Sturnidce in the Old World; and they are nearly
akin to the troopials {Agelaius). It is remarkable that not
any of the various American Cuadidce are parasitic ; w^hereas
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 that I do not agree with
Mr. Darwin in his view, expressed in the Appendix, that cases of specific
variation of instinct are difficulties in the way of his theory of the gradual
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 tliis 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 ease of instinct would
be unreasonable, if not inconsistent with the theory that innumerable in-
stincts owe their present existence to the destruction througli natural selec-
tion of the animals wliich 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 (Cocci/stes), 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. melanoleueus), 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, often called ' dirt-birds ' (Malacocei-cus) ; and as
the latter lay a spotless blue egg, similar in colour to that of
the hedge-chanter {Accentor modularis) of Europe, the Q^g 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 oricntalis),
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 Q^g in a crow's nest,
and the Qgg 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 {Scythroj^s novce-
Iwllcinclice), 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 2^en7ice 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 birds in
Southern Asia, Africa, and Australia, are not parasitic ;
neither, we have reason to lielieve, are the extensive malkoha
series (Fhwnicophaus and kindred genera), which inhabit the
same geographical area. Among the American Cuculidce, the
species of Coccyzus are nearly akin to the crested cuckoos
{Goccystes) of the major continent; and these, like the para-
sitic Cucidiclce, 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 VAEIETIES 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 tlie united labours of a flock of
them, usually on a high tree, where 'many parents bring
forth and educate a common family.' Mr. Kichard 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 wdio would try to
assign a reason for the parasitic habits of various Cucididce, as
also those of the ' cow-buntings,' which have no other trait in
common w4th 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, w^hen they do so for the protection of their youno-.
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 thati
"the long-legged Flamingo likewise has webbed feet, yeti
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."

Tlie MS goes on to detail other and analogous cases, such
as that of the Ground-woodpecker, Ground-parrots, 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
usino" 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 already
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 which 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 w^e 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 (Melancrpes
formicivmnis), which displays the curiously distinctive instinct
of storing acorns in the crevices of the bark of the yellow
pine {Pinus pondcrosa) for future food, wdiile no otlier species
of woodpecker shows any tendency to such a habit.* JKit
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 tlieir ancestral uses.f Lastly,
we must not forget the important fact that we are far from 1
being wholly without evidence of the transmutation of instinct I
taking place under actual observation — as in the case of the \
ducks in Ceylon having quite lost their natural instincts I
with regard to w^ater (in this resembling the upland geese), '
sparrows and swallows building on houses instead of on ti-ees,
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 Kaf. Hist. Soc, vol. x,
p. 227) the acorns selected for storing are only those which are infested with
maggots, which serre 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 Katuralist in Vancouver's Island,
vol. i, Dp. 289-92, and T/ie 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 leing 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 harvesting 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, tlie Hornbills of
Africa and of India in tlieir nidification show the same peculiar instinct of
imprisoning their hens in holes of trees with plaster, &c., &c.

256 MENTAL EVOLUTION IX 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.

MilI;, 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 Baiii. Herbert Spencer, and his
expositor Eiske, 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 wiLh 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 ;
lie recognizes the principle of lapsing intelligence in individuals.

EXAMINATION OF THE THEORIES OF OTHER WRITERS. 257

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

2o8 MENTAL EVOLUTION IN ANIMALS.

denominate all actions which occur below this line (howsoever
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. Eor 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 should 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 OF THE THEORIES OF OTHEK 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 ]3erformance 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 larva3 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 j)ro-

R 2

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 philosophical 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-
(K guish the most essential feature of instinct ; moreover it does
J 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 artiflcial
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

* Frinciples of Fsychology, i, p. 423.

EXAMINATION 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 influence 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 intelUgence, by " direct
equilibration " alone ; he supposes them to arise immediately
out of reflex action. ISTow, 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 possib]e 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

262 MENTAL EVOLUTION IN ANIMALS.

between the reflex and the instinctive, this possible third
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 the fittest
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 Jiypothesi is absent, 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 oi)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 j

* See Contemporary Review, Noyember, 1880, where the Duke argues
that 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 THEORIES 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), " If
we suppose any liabitual 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
w^onderful instincts with which w^e 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 plirases " iulieritecl 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 in tlie individual.

R E F L EX

ACTION

/NTELLICENT ACTION

H-imson '^ Sons. Litij . S": Marlins L;^ne.7^' C ,

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, wdiich 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 &itmmary on Instinct.

For the sake of rendering clear the relations wdiich 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 them 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 liave played no part in
tlie 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 his 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 performs these aiitomatic 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 w^hole I'ange of instincts no more unfortunate illustration could 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 intelligent 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., betw^een the branch Primary
Instinct and the branch Intelligent 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 w^ere, 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 tlie
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 display of instinct depends. In this
connection I gave instances to prove that such derangement

EXAMINATION OF THE THEORIES OF OTHER WRITERS. 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 sucli
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 lind — as, for example, young turkeys pointing at tlies,
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 walk, to speak, &c.
]\Ioreover 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 aiise either by natural selection fixing on pur-
poseless habits which chance to be profitable, so converting
these habits into instincts without intellisjence beincr 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 pnori 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. ISText, 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 fire-arms ;

EXAMINATION OF THE THEORIES 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 intelligent 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 tlie 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,
under 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 witli the
former. Lastly, I devoted a chapter to the consideration of
local and specific variations of instinct, showing liow these
constituted a kind of pahneontological evidence of the trans-
mutation of instinct.

Such then is the a 2'>ostcriori 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, wlio attributes the
origin of all instincts to reflex action with little or no aid
from natural selection, and on the other hand with ^Ir. 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 ]\Ir. Darwin, 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 ANIxMALS.

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 tlie conditions of the environment.

SIMILAR INSTINCTS IN UNALLIED ANIMALS.

CHAPTER XVIII.

Instinct (continued).

Cases of Special Difficulty with Regard 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 it& exhibition which admit of being
reasonably cited against the views here expressed on the rise
and development of instincts generally. I shall therefore
consider sen^iatim 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 JJnallied Animals.

Mr. Darwin observes in the Appendix, " We occasionally
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, andj
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, tliat we
may not readily believe a similarity of environment should |i
have determined its development mdependently in two lines 1 '

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 subject,
and the few remarks which he makes upon it seem to me
fully to dispose of the difficulty — which, indeed, wdth 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 occurren.ce, 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 tlie 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

I 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 difiiculty can be shown 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

TRIVIAL 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 actually
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 analoo'ous 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.
iS'ow I see no reason to doubt that the same may be true of
instincts, and therefore that what we now find to be ap- ;
j)arently trivial and certainly useless exhibitions of hereditary

* See p. 189.

S 2

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 Megapodidae
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 tumuli 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 appHes 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.

IXSTIXCTS 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 known 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 which 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 wdiole 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, wliere the case of tlie rattle of the rattle-
snake, &c., is considered.

278 MENTAL EVOLUTIOX 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, who 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 tortures
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 "Nature," 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. hisects flying 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-

* Origin of SpecieSy p. 208. + Animal Intelligence, pp. 222-5.

:j: July 12, 1883.

INSTINCTS APPARENTLY DETRIMENTAL TO THE SPECIES. 2 t 9

duced as evidence of an instinct detrimental alike to the
individual and to the 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 could 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 nothing 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 the 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 curiosit)^ 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 wliich 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

* YarrelVs Brit. Birds, 4th ed., II, 235

280 MENTAL EVOLUTION IN ANIMALS.

when the moon is in the horizon ? I formerly observed that
they liy very much less at candles on a moon-light niglit.
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
oliject 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.

3. Mr. Da^rwin 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 going 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
difficulty 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 j^rospec-
tive change of environment, while they 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 DETRIMENTAL TO THE SPECIE?. 281

ing that any such modification is urgently required. Xow it
can scarcely be held probable on these principles that the
instinct of crowing on the part of the pheasant should have
been modified by natural selection during the 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 the 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, ivoulcl 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 infiuence of man — and especially of savage man —
usually is, as compared with the sum of other infiuences,
organic and inorganic ; we must remember tlie time which
in any case is required for the modification of an instinct ;
and we must have proof that the instinct which 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 in 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 wliich thus congTegate, 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 much 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, however, 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 w^est, 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
alike 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 day 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. Collett, a Norwegian
naturalist, writes that in November, 1868 (quoted by Fille-
burg, infra) y 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 i\Ir. 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. . . . Is 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
hoUow out a couch in the long 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., toL xiii, p. 30, et seq. f I^ature, voL x, p. 459.
X Lmn. Soc. Jour., voL xiii, p. 157, et ,seq.

284 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 ]ias had a very large experience in observing
these migrations, namely Mr. Eobert CoUett, 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 this 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 tlie intrinsically probable nature of his views, 1
think we may most safely lend countenance to the latter.
The most important point of difference between Mr. Crotch
and Mr. CoUett 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. CoUett 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, et seq.

MIGRATIOX. 285

sistently away from land with the view to reacliing tlie
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 wliich 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 tlie
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 all 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 Wolft' 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 Moselej, A Naturalist on the Challenger, p. 5G1.

286 MENTAL EVOLUTION IN ANIMALS.

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.*

]\Iany species of Fish are known to migrate regularly for
purposes of spawning, such as the herring, salmon, &c., and
also to And water ; t 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 baffled 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 part 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, Loundoun's Mag. Nat. Hist.,
N.S., vol. iii.

t See Animal Intelligence, 248-50.

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
^vithin 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 laade 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 NeAvton, F.R.S., Art. Birds, where see for a good rh ume oi
tlie main facts of migration as regards bii'ds.

288 MENTAL ETOLUTIOX IX ANIMALS.

pendently arrived at by Mr. Wallace. It is only now tbat
Mr. Darwin's Adews 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 -
c^enso, 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 wiU suffer, and ultimately become
extinct ; which will also be the fate of those which do not
leave the feeding area at the proper time. Now 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 species 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 depend 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 ; p^^evalent winds or rains ; or even the

* Captain Hutton also foreshadowed these Tiews in 1872 ; see Trans.
New Zealand Inst., p. 235.

MIGRATION. 289

decreased temperature of the earth and water, may all have
their influence."

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 theyoimg
of many other species.t Taking then these assumptions
separately, the first is no more than a statement of fact, un-
accountable though the fact may be. That is to say, a verv
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 have
met with which seems to me opposed to this theorr. Mr. Uurdis in his
work entitled The XaturaU-st in Bermuda, obserres that the miffratorv golden
plover (CA<7ra<f /-/«.? marmorafus) passes over the islands in countless multi-
tudes (but without ever alighting") on the journey south, while they are never
s?en passing over the islands on their return journey north. Now. if it is a
fact that the two journeys are taken by ditferent routes, a difficulty would be
encountered by the above theory ; but as MJr. Hurdis says that the birds 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
their northern journey, although at a still higher elevation, and thus escape
notice.

+ See Temminck, If an. <fOrm., 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
a "e seen to be led by those whose age and exj)erience 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 birth
which made them unable to follow their parents '' (ioc. cif.. pp. 1S3— 4>.

J I have one instance of a cat returning in four days firom 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
o-eneral rule, the animals on their return journey do not
traverse the exact route which they had taken in the out-
o-oing journey, but 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 instan^^e, 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 ."f

Huddersfield, 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 m 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 says
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 because 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. The insects under these circumstances make straight
for their hive, so that by observing the point where several " bee-lines "
intersect, the honey seekers are able to find tbe hive.

t I may here also quote an observation by Mr. Dar■^^dn to the same effect : —
** I sent a riding-horse by railway from Kent via Yarmouth, to Freshwater Bay,
in the 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

Now 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 Jfj-
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 tliat 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 that I slackened tlie reins, he turned sharply round and began to trot to
the eastward by a little north, which 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.

T 2

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
published 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 w^est 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.'

" Referring 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 a-f an Organ of Mind, p. 215, wliere see also for cases of way-
finding 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 the seizure, and is not the cause of it. Tliis
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 feelings seizing
upon, and occasionally demoralizing, old and experienced
prairie travellers. Indian chiefs all concurred in assuring
Gr. Catlin (' Life amongst the Indians,' p. 90) 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 I
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 aw^are, are those of Sir
John Lubbock, on the sense of direction in the Hymenoptera
Cto which I shall allude presently), and those which have
more recently been published by M. Faljre,* 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 i
direction, after wdiich 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 w^ere 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 ]\I. Fabre con-

* Noiiveatix Sotivenirs Entomologiqucs, 18S2, pp. 99-123.

294 MENTAL EVOLUTION IN ANIMALS.

j eludes that the sense of direction cannot depend upon any

I 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 bee ; 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 all, 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 wdiich they were taken w^as 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 w^ere 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

* See Animal Intelligence, p. 150.

MIGRATION. 295

confused.* The possibility thus suggested receives, I think,
some countenance from the following fact. In "Animal
lutelligence " 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.t 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 ns 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 dii'ection to

* See Professor Newton in Nature, vol. xi, p. 6, who says, " Dark cloiidy
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 birds 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 Jonrn. Linn. Soc, 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
[l 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
hypothesis. 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 ?
j 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 bj Canon Kingsley {Nature, Jan. 18,
18G7), 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 perliaps also
in that of certain other migrator}' birds, tlie animals know
their way histinctively, or without even one lesson. P>ut 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 migi-ation.

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.

Instincts of Neuter Insects.

Mr. Darwin has pointed out a serious difficulty lying !
against his theory of the origin of instincts by natural selection, j
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 difficulty
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. Xo 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 amonoj 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
iu 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 SPllEX. 299

which Mr. Darwin has observed, and which is of much
importance as indicating that the ditlerent 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 Sphex.

Several species of this division of the Hymenoptera dis-
play what I think may be justly deemed the most remarkable
instincts in the w^orld. 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, aud, continuing to live in
their paralyzed condition for several ^veeks, are at last avail-
able as food for the larvae w^hen 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 wdiich 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 wdiere, in the case of the spider, most of
the central nervous matter is aggregated. When the victim
is a beetle, the Sphex wdiich preys upon it — there are eight
species which prey upon two genera — tirst 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 Oricfin of Species, 231-2.

300 MENTAL EVOLUTION OF ANIMALS.

cricket, the insect is thrown, as in the previous case, "upon its
back, and while holding it down with her mandibles firmly
fastened upon the last segment of its abdomen, her feet on
the sides liolding 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 tliat 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 with the cricket
and the caterpillar ; for here — or at least in the latter case —
we encounter the extraordinary and unavoidable fact of an
insect, without any accidental guiding or mechanicall}'

* All the above facts are taken from the works of M. J. H. Fabre
{Somienirs Entomologiques, 1879 and 1883), who was the first to observe and
describe them.

INSTINCTS OF TilE SPIIEX. 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 tliat 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 whicli is
most difficult of explanation upon the principles of tlie fore-
going theory. It is, however, most desirable that tlie facts
should be more thoroughly investigated, for it might then
appear that some clue would be given as to tlie 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 subsequent
development may probably hav^e 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
w^asp-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 stingmcr
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 wdiich 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 uesessary 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 larv£e may have heen 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-
incr that the humble-bees were saving time by sucking through
the holes instead of entering the tiowers. But the point
which is of importance in the present connection is the intelli-
o-ence 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."*

Seein<J, then, that Hymenopterous insects are certainly
proved by these observations to be capable of marvellously in-
telligent appreciation of morphological structure, I think witlr
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
stincvincT 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 furtlier 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 tlie present
state of our information upon the subject, Mr. Darwin's view,
as above stated, appears to be the most proljable one that
can be taken. We are not much surprised at tlie 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 eflects
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."-f' According to Wrangle,^ the wild
geese of Siberia, if alarmed during the moulting season wlien

* See Animal Intelligence, p. 347.

t Couch, Illustrations of Instinct, p. 199, et seq.

X Travels in Siberia, p. 312, Eng. Transl.

304 MENTAL EVOLUTION IN ANIMALS.

they 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
lias 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
re<7ard 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 Expedition,
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, w^hen surprised in a
hen-house, and it has even suffered itself to be carried out
by the brush and thrown out on a dungheap, wdiereupon 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, which, when a better means of escape
did not offer itself, prompted him to the stratagem of feigning

* Loc. cit. t LoundourCs Mag, Nat. Hist., N.S., voL i, p. 5.

FEIGNING DEATH. 305

to be incapable of defence or liiglit until lie 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 tliey are observed,
and in danger, but, wlien they believe that all foes have witli-
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 lieen 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, when 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 his Natural His-
tory of Ceylon, gives the case of a wild elepliant 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 : — " 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 asserted, _/ei'^«ec^ 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 groimd, 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 abantlooied. 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 jimgle, screaming at the top of its voice,
its cries being audible lopg 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 oonduct 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 w^ainscot, 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

* Mag. Nat. Rist., New Ser., voL ii, p. 124.

FEIGNING DEATH. 307

creatures made an effort to escape, and were taken up 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 h}^othesis 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 tlie 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 tliis 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

* Illustrations of Instinct, p. 125.

u 2

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.

This 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 much assistance in
originating, and possibly also in developing, this 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, tlie cray-fish — there
would be supplied 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 ^^'ood-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-o
peculiarities of organization on which natural selection may
seize for the developing of a beneficial instinct. But I desire
it to be particularly noted 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 oul
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 C[uestion ; 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. ]\Ir.
Darwin's observations place this conclusion beyond the reach

* An objection to tliis view may liere be disposed of : Duncan, " On
Instinct," after observing that spiders while slianiming 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 hekl
on its back.

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 instinct 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.
For 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 whicli 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 pole
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. When 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 winking of the wolf's eye, mentioned by Captain 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 gratified triumph, while the
crows flew round, cawing, as if deprecating the chastisement
about to be inflicted on their captive com|)anion. 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 aninml 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 being 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. 313

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
highly imitativ^e 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
wolves 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 the 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-buU 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

ol4 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 w^ish to quit. The ruse was practised fre-
quently with the object of enjoying my excellent gTass, and
akhough 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 were favoured w^itli a visit from
our friend."

Now here we have a case of apparent simulation of death
frequently repeated wdth an intelligent purpose, and as the
narrator is a medical man, we must suppose that the simula-
tion was ^vell 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
w^hich 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 nio-ht 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
Eeynard 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 tlie facts are here correctly recorded (and in all the
points U23on 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 liave 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
trutli simply is that there is a lack of sufficient observation,
by experimental means, to determine w^hether wolves, and
more es]3ecially 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 ujion the grass with
extreme gentleness, and immediately concealed himself, he might greatly haye
furthered the solution of the question.

316 MENTAL EVOLUTION IN ANIMALS.

lias 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 unal^le 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 ohserve that on retreating
without taking wing slie 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 deface 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
IS 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.

Eeason.

1 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

REASON. 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.

While treating of the genesis of Perception I pointed out
that the faculty admits of numberless degTces 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 i

320 MENTAL EVOLUTION IN ANIMALS.

/ ratios, which are themselves more or less elaborated percepts
I 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 conventional 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 infer 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-

REASON. 321

parisou. The inference is formed out of the perception, as it
were, immediately, and does not require to pass through any
such process of retiection 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 tliat 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 i
that we have to look for the first germ of reason : for this
purpose, let us first interrogate our own perceptions. TJie
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 gTcater 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 Elusions
of Perception ;" and in most of the instances which he gives
it is apparent, as he observes, that the illusion arises through
the mental " apj)lication of a rule, valid for the majority of

* Letters on Ifatural 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
(k. 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 liere 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 shaU 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 thing 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 as we found perception to form an integral part
of Memory and of tlie Association of Ideas.

REASON. 323

cat and which was the dog, he was ashamed to ask; but
catching the cat (which he knew by feeling) he was observed
to k)ok 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 youth, 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 the
utility of all our visual perceptions to depend upon the ingre-
dient of mental inference which is supplied by liabitual
association ; and, of course, we cannot doubt that the same is
true of perceptions yielded by the other senses.!

* Human Physiology, 7tli ed., p. 103, and in more detail, Contemp. Rev.,
vol. xxi, pp. 781-2.

t As Adam Smitli observes, in his comments upon this case, " When the
young gentleman said that objects which he saw touched his eyes, he cer-

X 2

324 MENTAL EVOLUTION IN ANIMALS.

Such, tlien, I conceive to be tlie first or most rudimentarv^
stage of inference, where, in virtue of constant association,
the act is organically bound up with a sensuous 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 tlie 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 staoe 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 stasje 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 rapid to admit of its

tainlj could not mean tliat tliey pressed upon or resisted his eyes ....
He could mean no more than that thej were close upon his eyes, or to speak
more properly, perhaps, that they 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 ears."
{Essay on External Senses.)

* Principles of Psychology, toI. i, p. 458.

REASON. 325

being consciously recognized as an act of mind separate or
distinct from the perception. The difference consists in suh-
sequent retlection being able to show that the act of inference
was distinct from the act of perception, and 7mcst 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 wdiat Mr.
Mivart calls " j^ractical 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 wliether he is waiting for me ; but
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 about 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 joossible 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 wdiole 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 comj)ared 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 ]3lace 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 first come into operation. Therefore in the case of this
youth it seems highly probable that during the twelve years

* Or ratlier, I shoiold say, so well known. Houzeau liad 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
AmmatiXy torn, i, p. 52).

EEASON. 327

of his 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 tlian 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 w^orth 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 ^lemory
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.

I 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 witli 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 Reason 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
Vertebrata, it certainly has attamed to much more than a

* For the sake 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 Leiu'et, who says {Anat. Comp. du Syst. Herv., tom. i, p. 540) : —

" ' One of the Orangs, which recently died at the Menagerie of the Musee,
was accTistomed, 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 olstacle
ivMch opposed his desire, climbed up the rope, placed himself above the knots,
and untied all three, in the presence of M. Geoffroy Saint-Hilaire, 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 foimd the one
which he wanted. Another time a bar of iron was put into his hands, and he
made use of it as a lever." '

REASON. 329

proportional development in tliem ; and this whetlier 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 intellio-ent of the ^lammalia. But lookin^^
to their psychology as a whole, I think tliat 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 i
nature of ant and bee intelligence makes it most ditiicult to '
compare with the intelligence of higher animals.

Another special difticulty with reference to reason in
animals meets us in the case of the Beaver. For, as remarked
in " Animal Intellioence," " 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.

660 MENTAL EVOLUTIOX IX 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 psycliological analysis, I feel that it is
desu^able 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 w^ould be a matter of
sincere gratification 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 wluch 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-
I 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.

First 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 wdiich 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 agTee, provided I am allowed

* See Principles of Psychology, i, pp. 253-71.
t Loc. cit., pp. 453-4.

REASON. 331

to make the important addition that it must be strictly
limited to the objective aspect, as distinguished both from the
subjective and ejective 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 imexceptionable. But if we passi
from physiology to psychology, the statement ceases -to be t
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 insufticient 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,
memories of the motor changes before performed under like
circumstances, and of the concomitant impressions." Still
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 that if we adopt Mr. Spencer's definition of Instinct,
tlie breacli on the mental side is still further widened — the distinction
between Instinct and Eeason 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.

332 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
i in all such cases Eeason, as distinguished from Consciousness,
imust arise. Therefore I should say that, although there
cannot be Eeason without such ganglionic friction, there
may be such ganglionic friction wdthout Reason. 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 he 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 witli
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 T 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 i
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 my
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, "f And the divergence in question became still more
* See p. 130. t See p. liO.

334 MENTAL EVOLUTION IN ANIMALS.

pronounced when I arrived at my analysis of Instinct ; for
by 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 .eases 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 wdiich now baffle oux 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 llie 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

EEASOX. 335

be caused by the intricacy or the novelty of the nervous pro-
cess wliich is accompanied by consciousness;"* but seeing that
in ourselves, as just observed, highly intricate and very infre-
quent nervous processes may take place meclianically, I do
not think we are justified in concluding that complexity and
in frequency of ganglionic action are the only factors in deter-
mining the rise of consciousuess. But even supposing, for
the sake of argument, that they are, still it would not follow
that the only road to Eeasoii 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 j
automatic inferences whicli, 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 ]\Ian. As the most enlightened and
best informed writer who of late years has espoused this
doctrine is Mr. Miyart, I shall take him as its exponent, and
in examinmg"Tiis 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 follow-

* See p. 140.

336 MENTAL EVOLUTION IN ANIMALS.

ing account of the exliibition 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 shall, therefore, pro-
ceed to consider the very prevalent opinion to which such a
commentary introduces us, and wliich 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 kind
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
general or special, complex or simple, lolurever there is a
process of inference from them, which results in establishing
a proportional conclusion among them, there we have some-
thins^ 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. f Lessons from Nature, p. 213.

REASON. 337

registers of such inferences already made, and short formulae
for making more." Now although this doctrine is not
universally accepted by 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 by this doctrine can the syllogism be
shown to have any functions or any value. " It must be
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 reasoning 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-j
ence, considered merely as a process of conscious inference;

* Logic, Tol. i, Chap. Ill,

338 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 which 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 we 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
hetween 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 mo7'e 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 summit 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
j -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
p)roportion 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

* Lessons from Nature, pp. 230-1.

REASON. 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,i
tliat 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 versa;" but
this, again, is no more than we should expect, on the hypo-
thesis of huma-n 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 Pteason is the special prerogative of
Man ? I think the misconception arises from an erroneous U
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, *^ V Instinct chez les Insectes" in Rev. des Deux Mondes^
Peb. 1870, p. 690.

Y 2

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-
j 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 tliis distinction is. Here I
am only concerned with showing that it does not consist in
animals having no vestige of the faculty of Eeason 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
Witli various living creatures, and the air
Keplenished? .... know' st thou not
Their language and their ways ? They also know
And reason not contemptibly." — Milton.

* Lessons from Nature, p. 217.

EMOTIONS. 341

• CHAPTER XX.

Animal Emotions, and Summaey 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, l*ug-
nacity. Industry, Curiosity, Jealousy, Anger, Play, Affection,
Sympathy, Emulation, Pride, Ptesentment, Esthetic Love
of Ornament, Terror, Grief, Hate, Cruelty, Benevolence,
Eevenge, 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, we 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
thii 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 npon 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 Preyer, loe. 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 stopped 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. 343

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 particiilars. 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 ; bvit, 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 without interruption thus to wag their heads until the procession
again begins to move. I have never seen this pecuhar movement performed
except under 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 Mollusca,* 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 the
central psychological tree, and with the earliest Eecognitior.
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 wliich
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 ;t 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.

+ For remarkable instances of this see ihid., p. 205 and p. 229.

X Ibid., pp. 22rt-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

pet.t

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,t which for other
reasons I have felt obliged to assign to this comparatively
high stage of psychological development.

On the next level (25) I have given Emulation, Pride,
Eesentment, Esthetic Love of Ornament, and Terror as dis-
tinguished from Fear. 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 as
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 cat, Mr. Oswald Fitch 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 gTatefully 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.

X Ibid., pp. 48-9 and p. 156.

§ Ibid., pp. 270-82. Birds are tlie lowest animals which] 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 feehng 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
Idtchen (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 Eevenge as distinguished
from Resentment, and Rage, 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.j The
same remarks apply to Rage, as distinguished from the less
violent display of hostile feeling wliich 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
psychology, and therefore at the highest of those products

* Nature, April 19, 1883, p. 580. f Pp. 277-8.

X Animal Intelligence, pp. 387-S and 478.

EMOTIONS. 347

with which the present treatise is concerned. These are
Shame, Eemorse, Deceit, and the Emotion of the Ludicrous.
For 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 ah
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 columns 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, lookinsj to the fact that our classification of
faculties is conventional rather than natural, w^e 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 Coelenterata, 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 Coelenterata, 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. For 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 tliis 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 Larvae of Insects and
Annehda. 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 Mollusca 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 Mollusca 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.lF

On level 22 I have written the higher Crustacea. I

* See Animal Intelligence, 234-40, and 24.

t Hid., and Mr. Darwin's work on Worms.

X Ibid., pp. 25-©. § Ibid., p. 27.

II Ibid., pp. 207-222, and 226-31. H Ibid., pp. 250-1, and 255.

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 Keason (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.f 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,^ and it is possible that Fish may be able
to reason, § while, on the other hand, the Reptiles 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 tliink most sharply marks off this
stage of mental evolution, i.e., the power of communicating
ideas — a power which ants and bees undoubtedly possess.||

* See Animal Intelligence, p. 233. X Ibid., p. 255.

t Ibid., pp. 259, 260-1, and 30. § ibid., pp. 250-1.

II Ibid., pp. 49-57, and 156-60.

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,t
and although it likewise unquestionably occurs in Eumi-
nants,J 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,1[ and the wolverine.**

* Animal Intelligence, pp. 311-12. f Ihid., p. 316. % Ihid., pp. 338-9.

§ Ihid., p. 361. II Ihid., pp. 428-31. ^ Ihid., pp. 420-22.

** Ihid., pp. 348-50. — Sir James Paget lias told me of a parrot wliicli by
attentive study learned how to open a lock ; but altliougli sucli eases 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 perfonn 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 facvdties 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 trvmk 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 480-94.

THE END

APPENDIX.

A POSTHUMOUS ESSAY ON INSTINCT,

15Y

CHAELES DAEWIN, M.A., LL.D., F.E.S

APPENDIX.

[The full text of a part of Mr. Darwin's cliapter on
Instinct wiitten 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 migratoi'v
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 distino-uished 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 K.
America, however, persecution has driven the Buffalo within

* Mr. G-ould lias observed tliis fact in Malta, and in Tasmania in Ihe
soutliern liemisphere. Eeclistein {Stuhenvogel, 18-40, s. 293) says that in
Grermany 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 Kobin Island, only two leagues from the con-
tinent {Le Vaillanfs Travels, vol. 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. Hist, of Ireland, vide " Birds," vol. ii, p. 70).

Z 2

356 ]\IEXTAL EVOLUTIOX IX ANIMALS.

a late period* to cross in its migrations the Eocky ]\Ionn-
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.t

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.J 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 l^y 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, Report of JExploring Expedition, 1845, p. 144,

t See Dr. Bachman's excellent memoir on lliis subject in Sillimcni's
PMlosojph. Joxirn., vol. 30, p. 81.

X Mr. W. Thompson lias given an excellent and full account of this
whole subject (see l^at. Hist, of Ireland, " Birds," vol. ii, pp. 247-57), "where
he discusses the cause. There seems reason to believe (p. 254) that the
migratorv and non-migratorv individuals can be distinguished. For Scotland
see St. John's Wild Sports ^of the Illr/hlands, 1846, p. 220.

§ Dr. Heineken in Zoological Journal, vol. v, p. 75. See also Mr. E. V.
Harcourt's Sketch of Madeira, 1851, p. 120.

II W. Thompson, lac. cit., vol. iii, p. 63. In Dr. Bachman's paper just
referred to cases of Canada geese in confinement periodically trying to escape
northward are ffiven.

APPENDIX. 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 ibr 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. Dihicult 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 an( I
south we know not. ]^or do we know how a bird whicii
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 WrangelJ
expatiates with astonishment on the " unemng 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 trymg 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
Ahson's remarks on this head in the Ct/clopcedia of Anatomy and Physiology,
article " Instinct," p. 23.

t [I cannot refrain from drawing attention to the superiority of scientific
metliod and philosophical caution here displayed as contrasted with Professor
Hackel'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). — G-. 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.

358 !^[p:yTAL EVOLUTION IX ANIMALS.

the nmnbers of lost swallows often met with by ships in tlie
Atlantic : the migratory salmon, also, often fails in returning
to its own river, " many Tw^eed salmon being found in the
Forth." But how a small and tender bird coming froin
Africa or Si:iain, 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 sheep
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 ijropensity
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 wdiere they usually lived ; so troublesome was this in-
herited propensity, associated with the period of parturition,
that the owner was compelled to sell the lotj 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 part of the country to another
distant four hundred miles : all 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 number of birds wliieli by chance visit the Azores (Consul C. Hunt,
ill Journ. Geograph. Soc, toL xv, Pt. 2, p. 282), so distant from Evirope, is
probably in part due to lost directions during migration : W. Thompson
{Nat. Hist, of Ireland, " Birds," vol. ii, p. 172) shows that N. American birds,
which occasionally wander to Ireland, generally arrive at the period when
they are migrating in N. America. In regard to Salmon, see Scope's Days
of Salmon Fishing, p. 47.

f Gardener'' s Chronicle, 1852, p. 798 : other cases are given by Youatt on
Sheep, p. 377.

X Quoted by Youatt in Veterinary Journal, vol. v, p. 282.

§ Bourgoanne's Travels in Spain (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, gives references to tln'ee other publications with similar accounts. I
may add that von Tschudi {Sketches of Nature in the Alps, Eng. trans.,
1856, p. 160) states that annually in the spring the cattle are greatly excited,
when they hear the great bell which is carried ^vith them ; well knowing that
this is the signal for their " approaching migration " to the higher Alps.

AI'PKXDIX. 359

tioiis." " The unquietiKk'," says anotlier aiitlior, " wliicli 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 wdiere they had heen born." ]\Iany cases have
occurred of three or four sheep having started and performed
the journey by themselves, though generally tliese Avanderers
are destroyed by the wolves. It is very doubtful whether
these migratory slieep 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 acquii'ed 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
mio-rations 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 beheve that this compulsory traAclling would
become an instinctive passion, as with the sheep in Spain.
Xow 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 coiu'se, it would safely cross the
sea now covering the submerged path of its ancient land
journey.*

* I do not suppose that the line of migration of birds always marks the
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.
Harcom't, avIio has written on the birds of Madeira, informs me that there
are none in that island ; so, I am infonned by Mr. Carew Hunt, it is in the

360 MENTAL EVOLUTION IN ANLMALS.

[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 Eeindeer 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) su^^ply of food. How
could their migration have been first established ? If the
climate formerly liad 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.*]

Instmctive 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 w^ere entirely void of fear of man : I have
ascertained this in six cases in the most distant parts of the
world, and wdth birds and mammals of the most different
kinds.! At the Galapagos Islands I pushed a hawk off a

Azores, thougli lie thinks tliat perliaps tlie Quail, wliicli migrates fi'oiu
island to island, may leave the Archipelago. [In pencil it is added " Canaries
none."— a. J. R.]

In the Falkland Islands, so far as I can find, no land-bird is migratory.
From enquiries which I have made, I find there is no migratory bird in
Mam'itius or Boiirbon. Colenso asserts {Tasmanian Journal, \o\. li, p. 227)
that a cuckoo, C. lucidus, is migratory, remaining only three or four months
in New Zealand ; but IN'ew Zealand is so large an island that it may yery
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
several migratory birds (Gi-aber, Tagehuch, 1830, s. 205) ; Iceland seems to
be the strongest exception to the general ride, but it lies only miles

from the line of 100 fathoms. [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 the
Falkland and Galapagos. Mr. Cada Mosto (Kerr's Collection of Voyages-,

APPENDIX. 361

tree with tlie muzzle of my gun, and the little birds drank
water out of a vessel which I held in my hand. Ikit I have
in my " Journal " given details on tliis subject, Jind I will
here only remark that the tameness is not general, l)ut special
towards 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 well known.* At the Galapagos Islands the great
land lizards {AmUyrliynchus) were extremely tame, so that I
could pall 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 algie : 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-

A-ol. ii, p. 246) says tliat at tlie C. cle Verde Islands tlie pigeons were so tame
as readily to be caught. These, then, are the only large groups of islands,
with the exception of the oceanic (of Avhich I can find no early account)
which were uninhabited Avlien discovered. Thos. Herbert in 1626 in his
Travels (p. 349) describes the tameness of the bii'ds 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 bu'ds at Tristan d'Acunha.
* Le Roy, Letfn^s PliHosoph., p. 86.

362 :\IEXTAL EVOLUTION IX ANIMALS.

ferecl 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
1)0 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 instindivehj
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.^ Although
it cannot be douljted that the fear of man in old inhabited
countries is partly ac(tuired, yet it also certainly is instinc-
tive ; for nesting birds are generally terrified at the first sight
of man, and certainly far more so than most of the old birds
at the Falklands and Galapagos Archipelago after years of
persecution.

We have in Enoiand 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
Harrington, § all our large birds, young and old, are extremely
wild. Yet there can be no relation between size and fear ;

* E. P. Tliompson, Passions of Animals, p. 29.

t Nat. Hist, of Ireland, " Birds," toI. ii, p. 133.

X [I may here refer to tlie corroboration wliieli tliis statement has
recently received in a correspondence between Dr. Eae and Mr. Goodsir
[Xature, July 3rd, 12th, and 19th, 1883). The former says that the wild
duck, teal, &c., Avhich frequent certain districts through which the Pacific
Kailway 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
(•oncerning \he wild fowl of Australia, adding, " The constant roar of a
great passing traffic, as well as the imceasing turmoil and unearthly noises of
ii large railway station within a stone's throw of their haunts, is now quite
unnoticed by these usually most watchfid 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. Kae's remarks." — Gr. J. R.]

§ Phil. Trans., 1773, p. 264.

APPENDIX. 363

for on uiitrequeiited 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 Lacks, 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 feioiiino;, as it is said, Death — an unknown state
to each livino- creature — seemed to me a remarkable instinct.
1 agree with those authors § who think that there has l)eeii
nmch exaggeration on this subject : I do not doubt that
fainting (I have had a Eobin faint in my hands) and the
[)aralyzing 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 Botang, vol. ii, p, 311.

t G-eofFry St. Hilaire, Anns, de.s Mus., tome ix, p. 471.

X [I have already pointed out the refined degree to whicli such instinctive
di'cad of man is developed Avhen it is able accurately to discriminate what
constitutes safe distance from fire-arms. Since "VATiting the passage to wliich
I allude (see ]). 197), I have met with the folio-wing observation in the letters
recently published by Dr. Kae in Nature, which is of interest as showing how
I'apidly such refinement of discrimination is attained: — "I may perhaps bo
])crmitted to give one of many instances known to me of the qviickness of
l)irds in acquiring a knoAvledge of danger. Grolden 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 seeuT to measiu'e with great accuracy the distance
at which they are safe from harm." — Gr. J. R.]

§ Couch, Illustrations of Instinct, p. 201.

II The n^ost curious case of apparently true simidation of death is tliat
given by Wrangel {Travels in Siberia, p. 312, Eng. trans.) of the geese which
migrate to the Tundras to moult, and are then quite incapable of tlight. He
says they feigned death so well " Avith their legs and necks stretched out
quite stiff, that I passed them by, thinking they were dead." But the natives
Avere not thus taken in. This simidation Avould not save them from foxes or
woIa'cs, &c., Avhich I presume inhabit tlie Tundras : Avoidd it save tliem from
hawks? The case seems a strange one. A lizard in Patagonia (.7o«;*«y?/ oJ'
Researches, p. 97), AAhich lives on tlu^ sand near tlie coast, and is s]ieckled
like it, when frightened feigned death Avitli outstretched legs, depressed l)ody.

364 MENTAL EVOLUTIOX IX ANIMALS.

<Kis ill this respect. We have amongst them a most perfect
series, even within the same genus (as I have ol)served in
Curculio and Ohrysomela), from species which feign only for
a second and sometimes imjDerfectly, still moving their
antennae (as with some Histers), and which will not feigli a
second time however much irritated, to other species which,
according to De Geer, may be cruelly roasted at a slow lire,
without the slightest movement — to others, again, which will
long remain motionless as much as twenty-three minutes, as I
tind with Ohrysomela spartii. Some individuals of the same
species of Ptinus assumed a difterent 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,
Ijoth 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
tlie really dead were as unlike as they possibly could be.

NicUjication and Hahitation. — 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
tind 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 fiirtlier distvirbed, it buried itself quickly in the sand. If
I he Hare had been a small insignificant anhnal, and if she had closed her eyes
when on her form, shoidd we not perhaps have said that she Avas feigning
death? In regard to Insects, see Kirby and Spence, lutroductioii to Ento-
molor/i/, vol. ii, p. 234.

AITEXDIX. 365

SO on, till we arrive ;it marvellous structures, rivalling the
weavers' art.

Even in so singular a nest as that of the Hirundo {Col-
localia csculcnta), eaten by the Cliinese, 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,
\QYj like pure gum aral)ic, 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 al)Sorbs
water and softens : examined under the microscope it
exhibits no structure, except traces of lamination, and ver}-
generally joear-shaped bubbles of various sizes ; these, indeed,
are very conspicuous in small dry fragments, and some bits
looked almost like ^'esicular lava. A small pure piece put
into flame crackles, swells, does not readily burn, and smells
strongly of animal matter. The genus Collocalia, according
to ]\Ir. 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.
]\Iacgillivray 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
X. Americaf another species of Swift causes its nest to
adhere against the vertical wall of a chinniey, and builds it
of small sticks placed parallel and agglutinated together

* [In tlie MS a blank is liere intentionally left for tlie subseqnont filling-
in of an appropriate word. — Gr. J. R.]

t For Cypselus murarliifi see Macgillivray, Br!tii<h Birch, vol. iii, 1840,
]). 625. For C. pelasgiua, see Mr. Peabodv's excellent paper on the Birds of
.Massacbussetts in the Boston Journal of Xat. Hist., vol. iii, p. 187. M. E.
Robert {Compter Renduft, qiioted in Anns, and Mag. of Nat . Hist., vol. viii,
1812, p. 476) found that tlie nests of the Hirundo riparia, made in the
gravelly banks of the Volga, had tlieir upper surfaces plastered with a yellow
animal substance, which he imagined to be fishes' spawn. Could he liave
mistaken the species, for tliere is no reason to suppose our bank-martin lias
any such habit? This woidd be a very remarkable variation of instinct, if it
coidd be proved ; and the more remarkable that this bird belongs to a dif-
ferent sub-family from the Swifts and Collocalia. Yet I am inclined to
believe it, for it has been afRinned with apparent truth that the House-martin
moistens the mud, with which it builds its nest, with adhesive saliva.

;]66 MENTAL EVOLUTION IN ANHIALS.

witli cakes of a brittle mucilage which, like that of tlie
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
liaving 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
])elieve, have suspected that it is formed of a secretion from
the salivary glands of the Ijird. 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 sliould 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 ? j\Ir. ]\Iacgillivray has shown that
the salivary crypts of the Swifts are largely developed, and
he believes that the sul)stance with whicli 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 csculaita. 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 Ijirds' 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 foi-mation of North America.

If it be admitted that the nest of each bird, wherever
placed and however constructed, l)e good for that species

* [It is almost needless to observe tliat we must remember the date at
winch this was \\Titten ; biit it may be remarked that as early as 1 817 it was
pointed out by Home {Phil. Trans-., p. 332) that the proventrieulus of Collo-
calia is a peculiar glandular structure probtibly suited to secrete the substance
of which the nest consists. — Gr. 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 j^ossibly have acted ; I
refer to Mr. Gould's observation* on the Australian Mega-
podidse. The Talcgalla lathami scrapes together a great
pyramid, from two to four cart-loads in amount, of decaying
vegetable matter ; and in the middle it dejDosit 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 Levpoa
ocellata makes a pile forty -five feet in circumference and four
feet in height, of leaves thickly co^xred with sand, and in
the same way leaves its eggs to be hatched by the heat of
fermentation. The Mcgwpodius tumulus in the northern
parts of Australia makes even a much larger mound, but.
apparently including less vegetable matter ; and other species
in the ]\Ialayan Archipelago are said to j)lace 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."{ 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.,

o68 MENTAL EVOLUTIOX IX ANIMALS.

observed* that ants ceased their laborious task of daily
movincr their eo-o-s to and from the surface accordino; 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 temj^e-
rature was provided.

Now let us sup2)ose that the conditions of life favoured
the extension of a bird of this Family^ whose eggs were
] latched 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 Avould 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 j)rocess 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 wdien 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
liabit of making "cock-nests," not lined with 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 Spence, Introd. to EntomoL, voL ii, p. 519.
t Peabody in Boston Journ. Nat. Hist., rol. iii, p. 144. For oiu' Briti^li
species see Macgillivray, Brit. Birds, voL iii, p. 23.

APPENDIX. 369

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
common progenitor, but with somewhat more considerable
modifications of instinct in one or both species, from that of
their ancient and unknown ancestor.

We -nill now consider the variability of the nesting-instinct. The eases,,
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 miiformity 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
sohtary or in communities, are not due to chance, or to intelligence, but to
instinct. The Sylvia stflvlcola, 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. (" YarreU's British Bii'ds.")

Necessity or compulsion often leads birds to change the situation of their
nests : numerous instances could 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 G-ulls on an islet off Labrador, " in consequence of the perse-
cution wliich 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. dornesticus) 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 curiosity." 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 : "the nest also varies greatly according to the place" (Mon-
tague, "Ornitho. Dict.,"p. 482). The Heron (Macgillivray, " Brit. Birds,"
vol. iv, p. 446: W. Thompson, "Nat. Hist. Ireland," vol. ii, p. 146) builds
in trees, on precipitous sea-cUffs, and amongst heath on the ground. In the
United States the Ardea lierodias (Peabody in " Boston Journal Nat. Hist.,"
vol. iii, p. 209) likewise builds ia tall or low trees, or on the ground ; and^
which is more remarkable, sometimes in communities or heronries, 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 Harmon ia Rural is, vol. i, p. 492) first took wool, then cotton,
and then down, which was placed near its nest. The common Kobin
will often build imder 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. nrbica) builds against perpendicular 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 lS2o Hinmdo luni-
from (Richardson, " Fauna Boreali-Amercani,"p. 331) for the first time built
against houses ; and the nests, instead of being clustered and each having a
tubidar entrance, were biult imder the eaves in a single line and without th&

2 A

:370 MENTAL EVOLUTION IN ANBIALS.

liibular entrance, or with a mere ledge. The date of a similar change in the
habits of H.fidva is also known.

In all changes, whether from persecution or convenience, intelligence
must come into play in some degree. The Kitty-wren {T. vulgaris), which
builds in various situations, usually makes its nest to match with surrounding
objects (Macgilhvray, vol. iii, p. 21) ; but this perhaps is instinct. Yet
wljen we hear from White (Letter 14) 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 the case was one of intelligence. Keithei
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 ^
turret, and reared up a perpendicular stack of sticks ten feet in height— a
labour of seventeen days : families of this bird, I may add (White's " Sel
borne," Letter 21), liave been known regulni'ly to build in rabbit-burrow a.
Numerous analogous facts could be given. The Water-hen {G. chloropus) vs
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 thai
this was never done. Water-hens and Swans, w^hich 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 the 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 iinder the eaves of houses, as well as in ti-ees.
In a treeless part of Scotland, 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, where 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 biid 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

Although I do not doubt that intelligence and experience often come
into play 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 omitt(Kl in the MS. — Gr. J. R.]

t For Norway, see in Mag. of Zool. and JBot., 1838, vol. ii, p. 311. For

Scotland, Rev. J. Hall, Travels in Scotland, see Art. " Instinct" in Cyclop.

of Aiiat. and Phi/sioL, p. 22. For Ireland, W. Thompson, Nat. Hist, of

Ireland, vol. ii, p. 329. For Cornwall, see Couch, Illustrations of Instinct,

p. 213.

APPENDIX. 371

not sense to draw it in lengtliways : White (Letter 6) describes some mar-
tins Avliich year alter year built their nests on an exposed wall, and year after
year they were washed down. The Funiarius cunicidarhis 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 biuTOwing numerous holes
through nmd-walls, over which they were constantly flitting, without thus
perceiving that the Avails were not nearly thick enough for their nests.

Many variations cannot in any way be accounted for : the Totanus macu-
la)'k(s (Peabody, "Boston Journ. Nat. Hist.," vol. iii, p. 219) lays her eggs
sometimes on the bare groimd, sometimes in nests slightly made of grass.
Mr. Blackwall has recorded the curious case of a yellow Bunting (Emfjc-
rlza citrinella) given in " Yarrell's British Birds," which laid its eggs and
hatched them on the bare ground : this bird generally builds on or very close
to the ground, but a case is recorded of its having built at a lieight of seven
feet. A nest of a Chaffinch {FringiUa coelehs ; " Annals and Mag. of jS'at.
History," vol. viii, 1842, p. 281) has been described, which was bound by si
piece of Avhipcord passing once round a bi-anch of a pine tree, and then
lirmly interwoven with the materials of the nest : the nest of the chaffincli
can almost be recognized by the elegant manner Avith which it is coatetl
with lichen ; but Mr. Hewitson (" British Oology," p. 7) has described one
in which bits of paper AA-ere used for lichen. The Thrush {T. viusicus)
builds in bushes, but sometimes, when bushes abound, in holes of walls or
imder sbeds ; 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). Ihe
Kev. W. D. Fox informs me that an " eccentric pair of blackbirds "
{T. mernla) for three consecutive years built in iAy against a wall, and
always lined their nest with black horse-hair, though there Avas nothing to
tempt them to use this material : the eggs also Avere not spotted. The
same excellent observer has described (in "HcAvitson's British Oology") the
nests of two Kedstarts, of wliich one alone Avas 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 PhUippensis, " Proc. Zool. Soc," July 27, 1852), about
one or two in every fifty have an upper chamber, in whicli the males ne^f,
grooved by the AA'idening of the stem of the nest with a pent-house added
to it. I will conclude by adding tAvo general remarks on this head by two
good obserAers (Sheppard in " Linn. Trans.," vol. xv, p. 14, and BlackAvall
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. BlackAAall, " that birds of the same species
possess the constructive poAvers in very different degrees of perfection, for the
nests of some individuals are finished in a manner gieatly superior to those
of others."

Some of the cases above given, such as the Totanus either making a nest
or building on the bare groimd, or that of the Water-ouzel making or not
making a dome to its nest, ought, perhaps, to be called a double instinct
ratter than a variation. But the most curious case of a double instinct Avhich
I have met with, is that of the Sylvia cl.siicola 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 scaati together AA-ith spiders' Avebs
and the down of plants, and is placed in marshes ; the venial nest is placed
in tufts of grass in corn-fields, and the leaves are not sewn tocether ; but the

372 MENTAL EVOLUTION IN ANIMALS.

sides are tliicker and very different materials are used. In sucli cases, as was-
formerly remarked witli respect to corporeal structures, a great and apparently
abrupt cliange might be eil'ected in the instinct of a bird by one form alone
of the nest being retained.

In some cases, when the same species ranges into a different climate, the
nest differs ; the Artamtis sordidus in Tasmania biulds a larger, more com-
pact, and neater nest, than in Australia (Gould's "Birds of Australia"),
The Sterna minuta, according to Audubon ("Anns, of Nat. Hist.," vol. ii,
1839, p. 462), in the soiithern 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 dry moss, well matted together and nearly as large as that of the
Turdus migratoriusy Those individuals of Icterus Baltimore (Peabody in
"Boston Journ. of Nat. Hist.," voL iii, p. 97) " Avhich build 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 BeaA^er have long been cele-
brated ; but we see one step by which its wonderful instincts
might have been perfected, in the simj)ler house of an allied
animal, the Musk Piat {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 ^^arts they do.j 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|l 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 Kev. L. Jenyns in Linn. Trans., vol. xvi, p. 166.

X A case sometimes quoted of Hares having made burrows in an exposed
situation {Anns, of Nat. Hist., vol. v, p. 362), seems to me to reqmre verifica-
tion : were not the old rabbit-burrows used ?

§ Zoologii of the Voyage of the Beagle, "Mammalia," p. 90.

II Catalogue of British Hymenoptera, 1855, p. 158.

APPENDIX. 373

hold in corporeal structures, namely, that tlie parts which
differ most in allied species, are apt also to vary most in the
same species. Another Bee, the Megachilc maritirna, 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 makinj^. 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 scroijhularice), 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 verbascum, becomes a burrower, and und(;rgoes its meta-
morphosis within a leaf.| 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 Hight
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 Orifjia of Species. — Gr. J. E,.]
t Quoted on authority of Sir J. Banks in Journal Linn. Soc.
X P. Huber in Mem. Soc. Phi/s. de Geneve, tome x, p. 33.
§ West wood, in Gardeners' Chronicle, 1852, p. 261.

:^)74 MEJsTAL EVOLUTIOX IX 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.t The pup?e of a species
ol Formica are sometimesX 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, the
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
shell. The fact of the occasional regurgitation of its food by
tlie Kangarooll 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 miglit when sprung."1[ 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
intlie 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, toI. ii, p. 480.

t Duges in Anns, des Set. Nat., 2nd series, tome vi, p. 196.

X F. Smitli in Trans. Unt. Soc, vol. iii, N.S., Pt. iii, p. 97; and De Greer,
([noted by Ivirby and Spence, Entomology, yoI. iii, p. 227.

§ Dissertation on Natural Theology, vol. i, p. 117.

II W. C. Martin in 3Iag. of Nat. Hist., N.S., vol. ii, p. 323.

IT W. Thompson, in Nat. Hist. Ireland, vol. ii, p. 65, says tbat lie has
observed this, and that it is well known to sportsmen.

=** Stuhen-vogel, 1840, s. 323. See on different powers of singing in
different places, s. 205 and 265.

ArrEXDix. :-57;h

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 witliin tlie bodies
of men — a most remarkable fact considering the temperature
to which tliey 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. 1 1 We are thus reminded of those Gulls
(Lestris) which exclusively live by pursuing other gulls and
compelling them to disgorge their food.lf

In the Hive-bee actions are occasionally performed which

* Blackwall's Researches in Zoology^ 1834, p. 158. Curier long ago
remai'ked that all the passeres have apparently a similar structure in their
vocal organs; and yet only a few, and these the males, sing; sLo\nng that
fitting structure does not always give rise to corresi^onding 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 birds imitating the
sounds of other species. — G-. J. R.]

t Rev. L. Jenyns, Observations in Nat. Hist., 1846, p. 280.

X Quoted by Ueoifry St. Hilaire in Anns, des Mtis., 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 (Macgillivray, British Birds, vol. v, p. 500)
that some of the species can only digest Ibod which has been partially
digested by other bii'ds.

376 MENTAL EVOLUTION IX 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-larvas 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 larv?e, 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, t

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 pecuHarity from community
of descent. The Molothrus (a bird something like a starling)
of N. and S. America has precisely the same habits with 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 ISTeuropterous and a Dipterous larva diggmg a conical

* Kirhy and Spence, Entomology, voL ii, pp. 510-13.

t [Concerning tlie question wliy there are so many drones as to require
killing, see Animal Intelligence, p. 166, wliere I suggest that among tlie
ancestors of tlie Hive-bee the males may haA-e been of use as workers. But
possibly the drones may even now be of use as nurses to the larvse, for I am
told by an experienced bee-keeper that he believes this to be the case. —
a. J. E.]

APPENDIX. o77

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,
thouiih leadinii' 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. Ikit I have met
with no facts in support of tliis 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 oft' for ever.f
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 Joicer part of the old bag-like split
skin of the caterpillar : this skin serves as a ladder which tlie
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 Linnaeus in Amoenitates Academicce, vol. ii; and Prof. Alison on
" Instinct" in TodcVs Ci/cI. of Anat. and Physiol., p. 15.
X Kirby and Spence, Entomology, vol. iii, p. 287.

378 MENTAL EVOLUTION IN ANLMALS.

afterwards disengages and casts off the skin which had served
it for a hidder.* I am tempted to give one other analogous
case, that of the caterpillar of a Butterfly {ThcMa), which
feeds within tlie 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 w^orker of the Hive-bee arranged in files
and ventilating, by a peculiar movement of their wings, the

* Kirbj and Spence, JEntomology, voL iii, pp. 208-11.
t J. O. Westwoocl in Trans. Entomol. Soc, vol. ii, p. 1.

APPENDIX. 379

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 trutli indisj^ensable, and
we may imagine the stages — a few bees first 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 Avhich leads her, as Waterton remarked, to fiy
from her nest and so leave no track to be scented out by
beasts of prey ; but this again may well be of liigli 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
wliich immediately follow their parents, the broken eggs are
left round the nest ; but when we hear that the nests of
those birds (Halcyonidie) in which the mutings are not
enclosed by a film, and so can hardly be removed by the
parent, are thus "rendered very conspicuous ;"t 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, plimges down so as to almost touch the sports-
man, and then mounts to an inmioderate height 4 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 conmion to all the species
of the o-enus, 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
l*eruvians, w^ho use the dried dung for fuel.§ ]\Iany 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-

* Kirby and Spence, Entomology, vol. ii, p. 193.

t Blytli in Mag. of Nat. Hist., N.S., vol. ii.

+ B race's Travels, vol. v, p. 187.

§ See my Journal of Researches^ p. 167 for the 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), A\-ith 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 ANII\rALS.

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.
Kara 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, wdiere 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 Eiicli, Descript. P/u/s. des lies Canaries, 1836, p. 423, on the
excellent authority of M. Reinwardts.

t L. Lloyd, Scandinavian Adventure, 1854, \o\. 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 SioedisJi. Acts, vol. iv, 1763, of ermines
migrating and entering the sea. See Bachman's account in Mar/, of Nat. Hist.,
N.S., vol. iii, 1839, p. 229, of the migration of squirrels; they are bad
swimmers and get across great rivers.

X Mr. Spence in his Anniversary address to the Entomological Society,
1848, has some excellent remarks on the occasional migration of insects, and
shows how inexplicable the ease is. See also Kirby and Spence, Entomology,
vol. ii, p. 12; and Weissenborn in 3Iag. of Nat/ Hist., W.S., 1834, vol. iii,
p. 516, for interesting details on a great migration of Libellulse, 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 1)e 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-clifis, the foremost, accord-
ing to Lewis and Clarke(?),* are often pushed over the
precijDice 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 xerj connnon
instinct is of any service to the species ? It has l^een 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."J 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 l^y Mr. Blyth, chuckles
like her domesticated offspring, when she has laid an egg;

* [The note of interrogation is in the MS. — Gr. J. R.]

t W. Scroi3e, Art of Deer Stalking, p. 23.

X Corse, in Asiatic Researches, yol. iii, p. 272, This fact is the more
strange as an Elephant which had escaped from a pit Avas seen by many
witnesses to stop and assist witli his trunk his companion in getting* out of
the pit {Athenceam, 1840, p. 238). Capt. Suhvan, E..N., informs me that lie
Avatched 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 CaiTion 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 vigorously defending
her; yet at other timers this duck never associates witli this goose, for their
fooel and place of habitation are utterly different. I very much fear, from
Avhat we see of little birds chasing hawks, that it would be more philosophical
to attribute this conduct in the duck to hatred of the carrion hawk rather
than to benevolence for the goose.

§ Eey. L. Jenyns, Observations in Natural Kisiory, 1816, p. 100.

382 MENTAL EVOLUTION IN ANIMALS.

and tlie natives thus discover her nest. In La Plata the
Furnarius 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 ojreat
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. IsTor 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. Flies, it
has often been asserted, frequently make mistakes, and lay
their eggs in substances not fitted for the nourishment of
their larva. A Spider J 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. Foxes and other carnivorous
Ijeasts 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 Besearches, p. 95.
f Knapp, Journal of a Naturalist, p. 188.

X These facts are given by Duges in Anns, des Sc. Nat., 2nd series
tome vi, p. 196.

§ £ruce's Travels in Abyssinia, vol. v, p. 179.

APPENDIX. ;583

stances ; but " the workers themselves act as if they suffered
in their instinct i'vom the imperfect state of their queen, for
they fed these male larwe with royal jelly and treat them
as they would a real (|ueen.''* 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 liabit be of any
service to the Bee ? Seeing tlie innumerable and admiral)le
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 V Can the instinct which leads the female
spider savagely to attack and devour the male after pairing
with liimj 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 utilitarianism, 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 the simpler
ones could have been thus acquired, others are so comj)lex
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 ha\nng less time) to the
instincts of animals in a state of nature : bearing in mind
tliat 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 been acquired by successive steps ; and

* Kirby and Spence, Entomology, vol. ii, p. 161 (3rd ed.).
t Ihid., vol. i, p. 380.

X Ibid., vol. i, p. 280. A long list of several insects wliicli either in
tlicir larval or mature condition will devour eacli 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 tw^o 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 numei'ous 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.

Abercrombie, Dr., a case of apoplexy described by, 36.

Abstraction, 145, 152-3, 352.

Actinia. See Anemone.

^lian, on instincts of capon, 171.

^stbetic emotions in animals, 341, 345.

Affection in animals, 345.

AlcipidcB, eyes of, 85-6.

AJford, Lord, hounds of, 198, 241.

Alison, Professor, on sense of modesty as instinctive, 193.

AUen, Grrant, 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.

AmpMoxus, 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 j 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; slave-
making instincts of, 317 ; grade of mental evolution of, 350.

Ape, delusions of a sim-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 ;
grade of mental evolution of, 349.

Association of Ideas. See Ideas.

Ataxy, analogous to lunacy, 44.

Audouin, on puppies learning to imitate cats, 223.

2 B

386 MENTAL EVOLUTION IN ANIMALS.

Auerbacli, on dilemma-time in perception, 134-5.
Aurelia anrita, nervous system of, 69.

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.

Baines, 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 offshoot 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.

Satrachia. See Amphihia.

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.

Bechstein, 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 Eev. 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.

Bingley, 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 nest-building of, 209-12 ; variations 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, 295-7; feigning death, 303-5; feigning
injury, 316-17 ; emotions of, 345 ; grade of mental evolution of, 351.

Biscacha, instinct of, 190.

Black, WilHam, on migration of swallows, 246.

Blackbird, conveying young, 211.

Blackie, Professor, on colour-sense, 100.

INDEX. 38T

Blaine, on Lord Alford's hounds, 198 ; on inherited tendency to bark ii>

sporting dogs, 236.
Blue-bird, local variation of instinct of, 210, 216.
Blyth, on 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, 226.
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. G-., 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.
Bidl, 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 ; migration of, 285-6.

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 ; mider-
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 Grer-
many, 232 ; sucking Ijones, 247 ; sense of direction in, 290.

Causation, appreciated by animals, 155-8.

2 B 2

:388 MENTAL EVOLUTION IN ANIMALS.

CepTialopoda, intelligence of related to organs of toucli, 57 ; eyes of, 88 ;
ears of, 89 ; tactile organs of, 89 ; colour-sense in, 98 ; memoiy 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 rosfrcttus, 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 handwi'iting, 194.
Caelenterata, consciousness in, 76, 348 ; special sense of, 83-4 ; emotions of,

342 ; grade of mental evolution of, 348.
Collett, E-., on migration of the lemming, 283-5.
Colour- sense, 98-104.
Comparative Psychology in relation to comparative anatomy, 5 ; obiects of, as

a science, 6-7.
Comte, on Fetishism in animals, 154.
Conceptualism, 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 the 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 psychology 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-parasitic habits oi
the, 251-2 ; parallelism of instincts of the, with those of Molothrus,
273-4 ; migration of the young, 289.
CucuUdce. 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-

Darwin, Charles, on the relation of intelligence of ant3 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 wildness 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, 245 ; on local variations of
instinct in birds, 245-6 ; on the hyaena not burrov\'ing in South Africa,
249 ; on specific variations of instinct as difficulties against the theory of
natural selection, 251 ; on parasitic habits of Molotlu-us, 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 theoiy 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 efiects 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 ; on the incorrigibly wild instincts of sundi'y 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 artiflcially 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.

DioTKsa, discrimination shown by, 50-1.

Direction, sense of, 289-94.

Discrimination, in relation to choice, 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 ujDon 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
_sho\ving fear of water, 188 ; natural wildness 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 Odynerus, 191-2.

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, nci'vous 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.

EdAvard, 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 woimded 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
JEnglena 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 Octopus, 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.

Eabre, J., on instincts of Bembex, 166, and of Sphex, 179, 299-303 ; on sense

of direction in bees, 293-4.
Fear in animals, 341 ; in young children and low animals, 342-3.
Feeling. See Sensation.
Feelings, logic of, 325.
Feigning death, 303-16 ; injui-y, 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 fimctions 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 tlie subordinate
part played by natural selection in tbe development of instinct, 256.

Fitch, Oswald, on benevolence shown by a cat, 345-6.

ritzEoy, 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 Eev. 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-alen, on instinct of a kid, 115.

Gallus lanJciva, wildness of chickens reared from wild stock of, 232.

Gralton, Francis, on hereditary genius, 194.

Granglia, structui'e and functions of, 26-33 ; Mr. Spencer's theory of genesis
of, 32.

Grardener, J. S., on moths flying into a waterfall, 280.

G-ardner, on intelligence of a crab, 336.

Garnett, on instincts of crossed ducks, 199.,

Gasteropoda, eyes of, 88 ; memory in, 121 .. See Mollusca.

G-eneralization, 145.

Grentry, W. K. Gr., on carnivorous habits of herbivorous rodent, 248.

Grladstone, W. E., on colour-sense, 100.

Groatsucker, 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.

Hseckel, Professor, on sense - organs, 81, 85-6 ; on supposed unknown
sense possessed by Fish, 90 ; on supposed unknown senses possessed

INDEX. 393

by Mammals, 95 j 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.

Hand\^Titing, inheritance of, 194.

Hate, in animals, 341, 345.

Haust, on ducks building in trees, 211.

Hawfinch, learning the song of a blackbu'd, 222.

Hawk, eye of, 91 ; old, teaching young to capture prey, 226 ; changed in-
stincts of Swallow-tailed, 254.

Hearing, sense of, in Medusae, 82 ; in Articulata, 86-7 ; in Mollusca, 88-9 ;
in Fish, 90 ; in Amphibia and Keptiles, 90 ; in Birds, 91-2 ; in Mam-
mals, 93-4 ; reaction-time of, 132.

Selix 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 incubating and natural instincts of the, 213-17 ; drinking move-
ments of tbe, not instinctive, 229 ; loss of incubating instinct of the
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 ; t.o 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.

Meteropoda, eyes of, 88.

Hertwig, Professors O. and E., on nervous system of Medusce, 69.

Hewetson, on variation in the nest of the nuthatch, 182.

Hewett, on wildness of hybrids between fowls and pheasants, 199.

Hill, Richard, on gi-egarious habits in nidification, 253.

Hitzig, on functions of the cerebrum, 35.

Hofacker, on inheritance of handwriting, 194.

Hoffmann, Professor, on a puppy learning to imitate a cat, 224.

Hogg, on instincts of a sheep-dog, 240-1.

Hollman, 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 acqiured 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 hankiva, 232 ; on
migration, 288.

Huxley, Professor T. H., on evolution of sense-organs, 104.

Syclrozoa, nerve-tissues in, 24.

Hyaena, not burrowing in South Africa, 244.

Hylohates 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 in 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 difierent 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 ; instmcts
of, 165-8, 179, 201-2, 203-9, 220-1, 246, 277-81, 285-6, 290, 293-5,
297-309 J emotions of, 344.

INDEX. 395

Instinct, physiological aspect of, 52 ; as hereditary memory, 115-17, 131 ;
definition of, 159; involves a mental element, 160; perfection of,
160-7 ; in young birds and mammals, 161-5 ; in insects, 1G5-8, 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 fossiHzed,
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 diffi-
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; 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.

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 instmcts 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 variation 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 ANI]\L\LS.

Lamarck, his theory of evolution of nerves by use, 33.

LamelUbranchiata, 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.

Lepidoptera, 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 as
groups of components, 41 ; his definition of Sensation, 78 ; on pre-
perception, 139 ; on instincts of ducklings, 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 Cahfornian 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 Kymenoptera, 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.

MaeFarlane, 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.

Macroglossa stellatarum, 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 imitatiag the songs of other birds, 222 ; on a terrier imitating a
cat, 233-4 ; on old birds educating young, 226 ; on instinct of burying
superfluous food, 233,

INDEX. 397

Mammals, special senses of, 57; sight, 92; hearing, 93-4; taste and touch,
94; colour, 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, 14i, 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 convulsiou, 44,

Marshall, Professor John, on sense of smell in Octopus, 89 ; on sense of sight
in Surinam Sprat, 90.

Martins, nidiiication of, 210-11 ; warning chickens against hawks, 221-2.

McCready, on larvae of a Medusa sucking their parent, 259-60.

MeduscB, larvse of, sucking parent, 259-60 ; following light not instinctive,
258 ; nervous system of, 24, 28 ; special sensation in, 56, 81-83.

Melanerpes formicivarus, peculiar instinct of, 255.

Memory, of ganglia without consciousness, 35-6 ; analysis of, 111-17; of
infant, 114-16, 120-1 ; in Mollusca, 121-2 ; in Echinodermata and
Crustacea, 122 ; in Insects, 123 ; in Fish, 123 ; in other Yertebrata,
124 ; as involved in perception, 129-30.

Merejkowsky, on colour-sense of Daplinea 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. a., on reason, 325, 335-40.

M'Laclilan, E,., 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.

Mollusca, 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 bearer, 329.

Morgan, Professor Lloyd, on alleged instinct of tlie scorpion to commit
suicide, 278.

Moseley, Professor H. N., on colour-sense of marine animals, 99; on imper-
fection of instinct in lioney-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, 38-44.

My sis, ear of, 87 ; colour-sense of, 98.

Mysteriousness, sense of, in animals, 155-8.

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 Hornbills, 255.
Nightingale, midnight singing of, inherited, 246.
Noulet, on nidification of swallows, 211.
Nuthatch, variation in nest-building of the, 182.

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.
OrtJioptera, ears of, 87.
Osmia aurulenta, 208.
Osmia hicolor, 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, Su' 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 G-roimd, 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 afPected by
heredity, 130-1 ; in Mammals, Birds, Keptiles, 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 ; 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 ; 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, appreciated by birds, 91 ; by Kylohates agilis, 93 ; and by
dogs, 94.

Play, 341, 345.

Pleasures, 105-11.

PleiironectidcB, 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 actiniae, 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 prefen'ing
sweet tastes, 114, and remembering taste of milk, 115 ; on instinct of
chickens, 116-17 ; on rapidity of perception acquired by training, 138 ;
on infant learning to balance the head, &c., 175-6 ; on imitative move-
ments and dreaming shown bv the infant, 225 ; on kataplexy of animals,
308-11 ; on emotions of the'iufant, 342, 344.

Prichard, on a puppy reared bv a cat, 217, 224.

Pride, 341, 345.

Progeny, yearning for, 212-13.

400 MENTAL EVOLUTION IN AMIMALS.

Protista as affected by liglit, 80-1.

Protozoa as affected by ligbt, 80-1 ; chasing one another, 81.
Pteropoda, eyes of, 88.
Pugnacity, 341 , 344.

Pierguin on somnambulism in animals, 149 ; on delusions of an ape, 150.
Psychology, relation of Comparative to Comparative Anatomy, 5 ; distinction
between, and Philosophy, 11.

Rabbit, 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 biu'rowing in Sor, 248.

Rae, 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.

Eats, understanding of mechanisms by, 351.

Eattle-snake, tail of the, 277.

Eazor-fish, memory in the, 122.

Eeaction-time, in perception, 132-5.

Eeason, 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.

Eeaumur, on larvae remembering the taste of particular leaves, 115 ; on
instincts of bees, 166 ; on instincts of the capon, 171-2.

Eecognition of olFspring, 349.

Eecollection, 120.

Eeflection, 145.

Eeflex 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.

Eegret, in animals, 347.

Ehea, mistaken instinct of the, 168.

Eemorse, in animals, 341.

Eengger, on changed instincts of a wild cat in confinement, 172 ; on attach-
ment of a monkey to a dog, 184.

Eeptiles, sense of sight in, 90 ; hearing, smell, taste, and touch of, 90 ;
colom* 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.

Eesentment, 341, 345.

Eetriever. See Dog.

Eevenge, in animals, 341, 346.

Mhizojjoda, powers of special sense in, 80.

Eibot, on memory, 111-13.

Eing-plovers, continuing to build where sea has retired, 246.

Eomanes, Gr. J., observations on Medusce, 31-2; on sea-anemones, 48, 83;
on EcMnodermata, 84, 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 colour-sense of Octopus, 98-9 ; on

INDEX. 401

earliest age at which an infant is abk^ to associate ideas, 120-1 ; on
inability of hermit-crab to associate simple ideas, 122 3; on time-rela-
tions in perception, 136-7 ; on sense of mysterious in, and appreciation
of cause by dogs, 155-8 ; on instinctive antipathy of young rabbits to
ferrets, 164-5; on handwriting, 19-4; 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, l7l.

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.

Sainfc-Hilaire, Greoffroy, on intelligence of an orang-outang, 328.

Salmon. See Fish.

Satiety, sense of, 95.

Savages, sense of direction 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 Serpulce, 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 Austi-alian puppy, 232 ; on love of man as in-
stinctive in domestic dogs, 239.

Seebohm, on migi'ation of biixis, 289.

Scinus hudsonms, 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 ; 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 was])s, 167.

Sight, sense of, in Protista, 81 ; in Medusae, 81-2 ; in Echiuodcrmata, 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 ; reaction-
time of, 133 ; in young animals, 161-4.

Sigismund, on infants remembering the taste of milk, 114.

2 c

402 MENTAL EVOLUTION IN ANIMALS.

Signs, logic of, 325.
Skate, oliactory organs of the, 90.
Skylark, feigning death, 304.

Smith, Adam, on a case of couching for ca,taract, 323-4.
Smith, Dr. Andrew, on hysenas not burrowing in South Africa, 249.
Smith, F., on instinct of bees, 208.

Smith, Col. H., on instincts of wild dogs imder 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 Eeptiles, 90 ; in
Birds, 92 ; in Mammals, 92-3.
Snipe, sense of touch in the, 92.
Social feelings, in animals, 341, 344.
Solen Goose, 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, eje of the, 90.
Squirrel, a, dying of terror, 307.
Star-fish. See Echinodermata.
Starlings, associating with rooks, 185.
Snarling, 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 natxiral 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.
Siu'prise, 341, 344.

Swallow, plasticity and local variation of instincts of the, 210, 246-7 ; migra-
tion of the, 296.
Swallows, nidification of, 210-11.

Swainson, on mistaken instinct of the Australian j^arrot, 167.
Swanderdam, on instincts of bees, 166.

INDEX. 403

Swift, eye of the, 01. See Swallow.
Sjiiipathy, 311, 345.

Sparrow, ludification of the, 210 ; changed instincts of a, 213 ; learning song
of a linnet, 222 ; local variations of instinct of the, 21-7.

Tachornls phoenlcohea, 212.

Tailor-bird, modified instincts of the, 210,

Tait, Lawson, on hereditary transmission of begging in a cat, 195.

Tameness. See Wildness.

Taste, sense of, in Protista, 81 ; in Articulata, 88 ; in Fish, 90; in Anipliibia
and Reptiles, 90 ,- in Birds, 92 ; in Mammals, 94.

Temmick, on migration of birds, 28^^.

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 attaclied to dogs and cats, 184 ; on
effects of domestication in modifying instinct, 242 ; on a monkey feign-
ing death, 311-12.

Thompson, Rev. 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.

Tiarojjsis 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 Medusae, Echinodermata,
Mollusca, and Articulata, 56 ; in Yertebrata, 58 ; in Fish, Ampliibia,
and Reptiles, 90 ; in Birds, 92 ; in Mammals, 94 ; as origin of all
special senses, 103-4 ; reaction-time of, 132.

Trevellian, on mistaken instinct of a sphinx moth, ]67.

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.

UUoa, on dogs not barking in Juan Fernandez, 250.

Venus' Fly-trap. See Dionfpa.

Venn, on association of ideas by talking birds, 124.

Villiers, De, on instincts of the processional caterpillar, 342.

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.

Wallace, A. E., on erolution 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 crossetl

ducks, 199.
Wasps. See Insects.
Weasel, feigning death, 307.
Weber, on sense of temperature, 96.

Wedderburn, Sn* 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 Eev. Gr., 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, 12 i.
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.
Wolff, Madame de Meuron, on a migration of butterflies, 285.
Wolvei'ine, 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 G-round, 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.
Wuiidt, on analogy between conscious and unconscious memory, 114.

Yarrel, on Birds, 222, 247.

Youatt, on the Dog, 150, 198, 241 ; on the Sheep, 224, 227.

Zinken, Dr., on mistaken instinct of flies, 167.

INDEX. 405

INDEX TO Mr. DARWIN'S POSTHUMOUS ESSAY.

Alison, on instinct, 357, 367, 370, 375.

Ambli/)-hi/nc7iu.<t, tameness of, 361.

Angoumois moth, double instincts of the, 373.

Antelopes, migrations of, 381.

Ants, ceasing to more eggs when heat is supplied to them, 368; instincts of

white, 376.
Artamiis sordidus, rariations in nest-bnilding instincts of, 372.
Audubon, on nidification of G-uUs, 369, and of Sterna miniita, 372.

Bachman, on migrations of the bison and Canada geese, 356 ; on migrations

of squirrels, 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-migratorj thrushes, 355; on variations 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 ;

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.
Biackwal], on nidification, 371 ; on magpies not imitating sounds when in a

state of nature, 374-5 ; on nidification of a yellow bunting, 371.
Blytli, on instincts of removing mutings, &c., from 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.
Bucli, von, on animals dying in the Solfortara of Java, 380.
Buffalo, migration of the, 355-6.
Burrowing, instinct of, 372.
Butcher-bird, nidification of the, 382.

406 MENTAL EVOLUTION IN ANIMALS.

CarmicTiael, Capt., on tameness of birds at Tristan d'Aciinlia, 361.

Caterpillar. See Insects.

Chaffinch, nLdification of a, 371.

Chickens, instincts of, 374.

Chrysomela, feigning death, 364.

Clarke, on migi*ation 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 ; instincts of the Eee, 382.

Curculis, feigning death, 364.

Cuvier, on vocal organs of Passeres, 375.

D'Arbigny, on knowledge of time shown by a hawk, 357.

Parwin, 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 Furnarins cunicularius, 371 ; on the in-
stinct of burrowing, 372 ; on instincts of the Guanaco and Bizcacha,
379 ; on the nidification of FiirnariuSy 382.

Death, feigning of by animals, 363-4.

Deer, expelHng 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 Boiu-bon, 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.

Elephants, attacking companions escaped from captivity, 381.
Elk, migrations of the, 360.

Fischer, Professor, on a hen incubating her eggs in a hot-bed, 367.

Fly-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 cunicidarius, stupidity of, 371 ; nidification of, 381-2.

Gad fly, instincts of the, S75.

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 Erent, worn out, 350; the Siberian feigning

death, 363.
Goring, instinct of, 381.
Gould, on migration of birds, 355 ; on nidification of MegapodidcB, 367; of

Artamtis 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 woodcock, 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 Xorway, 363 ; on nidification of a

chaffinch, 371.
Mirundo, migration of, 358 ; nidification of, 365-6, 369-70.
Histers, feigning death, 364.
Hogg, on migi'atory instinct of sheep, 358.
Home, on structure of the proveutriculus of CoUocalia, 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 Mai'tin.
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 haUimore, 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, exhibited 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.

biirroTving, 372 ; variations in, of bees, 372-3 ; of chickens peeking tlioir
way out of eggs, 374 ; of gad-fly, 375 ; of parasitism, 375-6 ; of bees,
375-6 ; of Ilolothriis and white ants, 376 ; of digging pitfalls, 376-7 ;
alleged to be rletrimental to the species exhibiting it, 377; only once
exhibited, 377-8 ; differences of, in related forms, 378 ; email and
trivial, 378-9; of removing broken eggs and mutings, 379; of Abys-
sinian pigeon, Lagostomus, and Griianacoes, 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.

Jackdaw, nidification of a, 370 ; stupidity of a, 371.

Jenyns, the Eev. 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, regiu'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.

Lagostomns, instincts of, 401.

Lamarck, on co-operation of swallows, 375.

Larvae. 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 Yaillant, on migi'atory 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.

Macgillivray, on nests of swifts, 365-6, of kitty-wrens, 368 and 370, of

herons, 369 ; on cooperation in martins, 375 ; on parasitism in gulls,

375.
Magpie, fearlessness of the, in Norway, 362 ; nidification of the, 370 ; powers

of the, in imitating various sounds, 394-5.
Mammals, migi-ations of, 355-6, 358-9 ; instinctive fear shown by, 361 ;

habitations of, 372-3.

INDEX. 409

Martin, nidificatiou of (he, 3G4, 309, 370.

Martins, cooperation shown bj, 375.

Martin, W. C, on regurgitation of food by the Kangaroo, 374.

MegapodidcB, nidification of, 367-8.

Mice, "wariness of, 362.

Migration, 355-60 ; of joung birds, 355; of quail, 355; of buffalo, 355-6;
tlieory of, 359 ; of elk and reindeer, 360 ; of lemming, squirrel, and
ermine, 380 ; of insects, 380 ; of pigeons, antelopes, and bis(^ns, 381.

Molofhrus, instincts of, b76.

Montague, on nidification of sparrows, 369.

Moresby, Capt., on tameuess of birds at Providence Islands, 361.

Mosto, Cada, on tameness of C. de Yerde Island pigeons, 361.

Musk-rat, habitation of, 372.

Nidification, 364-72 ; of swallows, 365-6 ; of Mecjapodidce, 367-8 ; varia-
tions in instinct of, 369-73 ; double instinct of, 371-72.
Nightingale, variations in singing of the, 374.

Osmia, variation in instincts of, 372-3.
Ostrich, scattering her eggs, 382.

Partridge, variation in instincts of the, 373.

Peabody, on nidification of Cypelus pelasglus, 365 ; of kitty -wrens, 368; of

herons, 369 ; of Tot anus macular ius, 371 ; of Icterus baltimore, 372.
Pheasant, maternal instincts of the hen, 379 ; crowing instincts of cock, 381.
Pigeon, fearlessness of the, at C. de Yerde Islands, 361, and at Galapagos,

363 ; instincts of the Abyssinian, 379 ; migration of the Passenger, 381 ;

instinct of the, in attacking wounded companions, 380.
Ftimts, feigning death, 364.

Fulex, variations of pupa of, 374.

Quail, migration of the, 355.

Q-

Rae, Dr. J., on fearlessness shown by birds of railway trains, 362 ; and of

firearms, 363.
Rat, musk, habitation of the, 372.
Rat, wariness of the, 362.
Reaumur, on instincts of anfs, 368.
Redstarts, nidification of a pair of, 371.
Reindeer, migrations of the, 360.

410 MENTAL EVOLUTION IN ANIMALS.

Eeinwardts, on animals clyiDg in tlie Solfortara of Java, 380.
Eichardson, on nidificatiou of American swallows, 369-80.
Roberts, M. E., on nidification of Hirundo riparia, 365.
Robin, fainting from fright, 363 ; nidification of the, 369.

Salmon, migrations of the, 355, 358.

Savi, Dr. P., on the double instinct of nidification shown by Sulvia cisticola.

371.
Scope, on migration of salmon, 358.

Scrope, W., on deer expelling womided companions from herd, 381.
Sheep, homing faculty of Highland, 358; migratory instinct of Spani'^h,

3o8— 9.
Sheppard, on the nidification of a golden -crested wren, 371.
Shrew-mouse, instinct of a, in screaming when approached, 382.
Smith, Dr. Andrew, on migrations of quail, 355 ; on hya;nas 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 mmuta, variations in nest-building instincts of, 372.
St. Hilaire, Greoffry, 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.

Taylor-bird, nidification of the, 369.

Thompson, E. P., on instinct, 357 ; on wariness of rats and mice, 362.

Thompson, 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 show^l 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, migratory and non-migratory varieties of the, 355; nidification of the,
368-9, 371.

Totanus macularius, nidification of, 371.

Water-hen, nidification of the, 370.
Water-ouzel, nidification of the, 370.

IXDF.X. 411

Waforton, on instincts of the hen pheasant, 370.

Weaver-bird, nidification of the, 371.

Weissenborn, on migrations of insects, 380.

Westwood, on instincts of caterpillars, 373, 378.

White, tlie Rev. G., on the nidification of a willow-wren, and of jackdaws,

370 ; of martins, 371.
Wolf, wariness and tameness of the, 3fil.
Woodcock, migratory and non-migratory habits of the, 35fi.
Wrangel, on sense of direction shown by natives of N. Liberia, 357 ; on

Siberian geese feigning death, 363.
Wren, nidification of the, 368, 369, 370, 371.

Yarrel, on British birds, 367, 369, 370, 371.
Yellow bmiting, nidification of a, 371.
Youatt, on sheep, 358.

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