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 VII. CBITICAL NOTICES. fa! Erotution 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 bv 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 Aninwl 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 Medusae. 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 con- fluence 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 " differentia- tions 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 morpho- logical 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).