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MENTAL EVOLUTION IN ANIMALS. By GEORGE J. ROMANES.

The readers of Professor Romanes's excellent work "Animal Intelligence" have been led to look forwardto this book with not a little interest. Indeed both volumes may be regarded as one work. They are separated into two distinct parts mainly as a matter of convenience, since the plan of the International Science Series for which the earlier book was primarily intended would not admit of so voluminous a work as both volumes would form "Animal Intelligence," it will be remembered, was in reality a compendium of facts gathered with the most conscientious care and diligence. The present volume is a treatise on the facts already stated, while at the same time it deals with a wider range of subject matter, taking up as it does the involved question of evolution in the lower animals. The psychology of man, the author tells us he has not touched upon reserving this for a subsequent exhaustive study. In the present essay he is content to trace in as scientific a manner as possible the probable history of mental evolution and to inquire into the causes which have determined it. When experimental or historical verification is not possible deductive reasoning is resorted to, but as sparingly as possible and chiefly to carry on the thread of the argument. In working out this plan, Professor Romanes has brought together a great array of facts, not only from books, but largely also from his personal experiments. A large section is devoted to the development of instinct, and in these pages will be found a notable contribution to science particularly valuable because this branch of psychology in the writings of leading authorities has been too frequently slighted or obscured.

A book on such a subject as this could hardly be written without constant reference to Darwin's works, and Professor Romanes draws freely from his published writings. He has been able also to add, through his access to some unpublished MSS., much that is entirely new. In an appendix is printed the full text of a posthumous essay on instinct which Mr. Darwin wrote for the "Origin of Species," but afterward suppressed for the sake of condensation.

[New York: D. Appleton & Co. I vol., 12mo, $2.]