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VII.—CRITICAL NOTICES.

Mental Evolution in Animals. By GEORGE JOHN ROMANES, M.A., LL.D., F.R.S., Zoological Secretary of the Linnean Society. With a Posthumous Essay on Instinct by CHARLES DARWIN. London: Kegan Paul, Trench, 1883. Pp. 411.

This book is probably the first attempt to treat the psychology of animals systematically and as a whole. It is based on the theory of evolution, without which, indeed, such an investigation would scarcely have been possible. To the materials contained in the author's previous work on Animal Intelligence much has been added in the present volume. In the chapters on Instinct especially, new accounts are to be found of observations made or collected by the author. The chapter on "The Structure and Functions of Nerve-Tissue" contains an account of the results of his important researches on the nervous systems of the Medusæ. These researches seem to him to confirm Mr. Spencer's theory of the origin of nerve-fibres but not of nerve-cells, which he infers to be not, as Mr. Spencer argues, the result of the confluence of fibres, but of the further specialisation of cells that have already become specialised as epithelial or epidermal cells. In the chapter on "Sensation" he gives the evidences of the view now generally taken by biologists that the organs of special sense arise as modified parts of the epidermis. He agrees with Mr. Spencer in concluding that the senses are all "differentiations of the general sense of touch".

Some of the facts that are found at the beginning of the chapter on Sensation point to the conclusion, which was also suggested by the facts given in the earlier chapters of Animal Intelligence, but which is nowhere drawn by the author, that the lowest animals, although they have no organs of special sense, but only, so far as can be made out, a general sensibility resident in their protoplasm, have the beginnings not only of sensibility but also of will and intelligence. The only difficulty of admitting this seems to be that animals higher in the zoological scale would have to be placed lower in the psychological scale. And this difficulty is apparent rather than real. For in all morphological classifications parasitic animals and plants form anomalous groups. Now animals that have lost the plasticity characteristic of Protozoa, and whose nervous systems are occupied chiefly in reflex actions, might be regarded as psychologically degenerate, just as parasites and some non-parasitic animals are degenerate morphologically.

The definition of Instinct given in Animal Intelligence is repeated in the present work. Instinct is defined as "reflex action into which there is imported the element of consciousness" (p. 159).

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This is now explained to mean that, while "a stimulus which evokes a reflex action is at most a sensation," on the other hand "a stimulus which evokes an instinctive action is a perception". It might be expected from this that Dr. Romanes would agree with Lewes in speaking of unconscious sensations. But he refers to Lewes's definition of a sensation, as simply the reaction of a sense-organ, only to reject it, and goes on to say that "the difficulty of determining whether or not this or that particular low form of life has the beginnings of Sensation is one and the same as the question whether it has the beginnings of Consciousness" (p. 79). According to this statement, wherever there is sensation there is consciousness; and from this it seems to follow that some reflex actions—that is to say, those which are excited by sensations—are accompanied by consciousness. But, according to the definition, these are instincts. Instinct, therefore, by the definition (as it is now interpreted), seems indistinguishable from reflex action.

The constructive and psychological part of the present volume is less successful than the part that serves as a supplement to Animal Intelligence. Apart from all differences of opinion on purely philosophical questions,—which the author desires to avoid,—the treatment of the fundamental question of the relation of Mind and Body can hardly be described as satisfactory. It is quite possible, without implying any metaphysical doctrine, to regard mental and physical changes always as concomitants, never as causes and effects of one another. In some places Dr. Romanes seems to be unwilling to take up this position for fear of committing himself to some definite system of metaphysics. In the following passage his words imply that its evidence is that of a directly observed fact.

"We know by immediate or subjective analysis that consciousness only occurs when a nerve-centre is engaged in such a focussing of vivid 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 comparative delay in the occurrence of the eventual response. But we are totally in the dark as to the causal connexion, if any, between such a state of turmoil in the ganglion and the occurrence of consciousness" (p. 75).

Notwithstanding the statement in the last sentence, Dr. Romanes sometimes appears to think that the occurrence of consciousness is somehow explained if it can be shown to arise when there is an increase in the time taken up by the transmission of a stimulus. "Consciousness," he says, "is but and adjunct which arises when the physical processes—owing to infrequency of repetition, complexity of operation, or other causes—involve what I have before called ganglionic friction" (p. 113). When the nerve-centre has become "a seat of comparative turmoil among molecular forces" it "begins to become conscious of its own work-

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ing" (p. 319). Not only is this attempt made to explain consciousness from the objective side, but an attempt is also made to show how mental states may become factors of physical changes.

"Possibly, however—and as a mere matter of speculation, the possibility is worth stating—in whatever way the inconceivable connexion between Body and Mind came to be established, the primary cause of its establishment, or of the dawn of subjectivity, may have been this very need of inducing organisms to avoid the deleterious, and to seek the beneficial; the raison d'être of Consciousness may have been that of supplying the condition 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 Consciousness in the scheme of Evolution" (pp. 110-111).

It is difficult to infer anything from this passage except that the objective factors of the process of evolution have the power of introducing subjective factors among themselves, which in turn act upon the objective factors and change the course of events. And in other places purely physical processes are spoken of as "the raw material of consciousness". Perhaps the inconsistency in all this is only verbal; and it must be admitted that in many passages the expressions as to the relation of Mind and Body are not open to objection. But the opposition between subject and object might have been stated with more clearness and maintained with more consistency.

The selection of "the criterion of mind" is the starting-point of the investigation. The evidence of Choice having been taken as a criterion by which "the upper limit of non-mental action" may be determined, it is decided that "the physiological aspect of choice" is "the power of discriminating between stimuli, irrespective of their relative mechanical intensities". This power and "the complementary power of adaptive response" are "the root-principles of mind". There is a correlation such as might be expected a priori "between muscular and mental evolution—or, more generally, between power of discrimination and variety of adaptive movements".

"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" (p. 62).

The development of mind is figured in the diagram placed at the beginning of the book by a tree-like structure having its stem assigned to Will, and a system of branches on each side to Emotion and Intellect respectively. 'Volition' is represented as continuous with 'Reflex Action,' which is itself continuous with

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'Neurility'. 'Neurility' is formed by the confluence of 'Discrimination' and 'Conductility,' which have their root in 'Excitability'. On the side of Intellect, from a branch representing 'Sensation' (which springs from the stem) a branch representing 'Perception' is given off; from 'Perception,' 'Imagination' is represented as originating; from 'Imagination,' 'Abstraction'. on the side of Emotion, a branch representing 'Preservation of Self' and 'of Species' springs from the stem and gives off a branch the lower part of which represents the beginning of 'Social Emotion'. The names of groups of animals are placed in a column that stands for 'the Psychological Scale'. Opposite these names in two other columns we find the 'Products of Intellectual Development' and 'Products of Emotional Development' characteristic of each group of animals. The levels drawn across the diagram at equal intervals are intended to represent degrees of elaboration of faculty.

The author points out the sufficiently obvious defects of such a diagram—that it does not adequately express the transitions that there are in nature from one stage of intelligence to another, and that the division of mind into "faculties" is essentially artificial. But there is another defect which he has not pointed out. The development of mind is represented as proceeding only in a single line. For the branching structure can only represent the division of a single mind at each of its stages into faculties, not the divergence of different types of mind. Nothing is said as to the possibility that at the same level of general intelligence there may be essentially different mental types,—dependent, for example, on different degrees of acuteness of the senses, and different ratios of their degrees of acuteness to one another. For anything the diagram tells us—and the same thing may be said of the whole book—there might be no differences between minds except differences of position in serial order. But if minds have been evolved, we should expect them to fall into groups having the peculiarities pointed out by Darwin as characteristic of all groups that have originated by evolution. And the evolution of existing types of animal intelligence, as well as of existing types of animal organisation, ought to be shown by a genealogical tree, not by a structure that cannot represent the growth of more than one type, either of mind or of organisation. If the construction of such a genealogical tree is at present impossible, it might at least have been pointed to as the ideal of a science of comparative psychology.

The definitions of the "faculties" are not quite so clear as is to be desired. This is perhaps comparatively unimportant; for it might be maintained that the distinctions expressed by the terms Sensation, Perception, Imagination, Abstraction, &c., have to such an extent become part of common thought that they may be applied with at least approximate accuracy by a good observer without the aid of strict definitions. But the more special terms that are

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written above one another to express the exact degree of intelligence at which various classes of animals have arrived are sometimes the names of processes that are common to a large number of particular mental acts (as 'Memory,' 'Association by Contiguity,' 'Association by Similarity,' 'Reason'), sometimes names of special acts or of concrete products of mental activity (as 'Recognition of Offspring,' 'Dreaming,' 'Understanding of Mechanisms'). This mixture of terminologies having different values is a little incongruous. The scale of emotional development seems to have been drawn up without any attempt at a preliminary analysis of the emotions, and is so far more consistent than the scale of intellectual development, which is the result of a compromise. 'Pleasures and Pains' seem out of place among 'Products of Intellectual Development'. And although in the chapter on Emotion Dr. Romanes says that the emotions are represented as originating at the same time as perception because "as soon as an animal or a young child is able to perceive its sensations, it must be able to perceive pleasures and pains," no use is made, in his discussion of the emotions, of the theory of pleasure and pain adopted by him from Mr. Spencer and Mr. Grant Allen.

It is in his detailed treatment of Instinct, extending to eight chapters (pp.159-317), that the author makes the most decided advance. Other writers have for the most part treated some one factor in the formation of Instinct in isolation from the rest. Dr. Romanes has brought together the ideas of "Primary Instincts" that originate by natural selection, and of "Secondary Instincts" that are the result of the transmission of organised habits. He has explained how the two processes by which instincts have been formed may influence one another, and how intelligence may modify instincts formed by each process and by the combination of both. These ideas are developed with great elaboration. All the positions that are taken up as to the existence of the simple processes, as to the compounding of factors, and as to the transmission by heredity of modifications of instinct are established by evidence. A good view of the general result of this investigation is given by the diagram placed opposite p. 265.

The posthumous Essay by Darwin printed as an Appendix is chiefly a collection of facts bearing on the theory of instinct; and other notes made by the great naturalist are used by Dr. Romanes in his own treatment of the subject. No completed theory is to be found in the Essay; but it will have some interest for those who may wish to study in an earlier stage thoughts that are fully worked out in the eighth chapter of Origin of Species.

THOMAS WHITTAKER.