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In the first of these volumes Mr. Romanes devotes himself to an exposition and critical examination of the complicated theory, or rather to the successive theories, of Heredity and Evolution, which the biological world owes to the prolific imagination of Professor Weismann. In both respects Mr. Romanes' work is admirable, and the student of biological speculation could secure no abler or more lucid guide through the tortuous mazes of a much advertised subject. Mr. Romanes, after much patient explanation, comes to the conclusion that Weismann's latest admissions amount to an abandonment of the principle for which he fought so hard, and that his attempts in part to bolster up a defeated theory are improbable in the extreme. He shows that all that is valuable and tenable in Weismann was long ago stated in Galton's theory of "stirp." But though his criticism is crushing, it is throughout courteous in tone, more so than the disingenuousness (cf. p. 156) and logical shortcomings of his adversary would perhaps require. The book concludes with a declaration of his intention henceforth to discuss the question of the inheritance of acquired characteristics on its own merits, and without special reference to Weismann's theories.

This promise is fulfilled by the second volume, as valuable as the first, which was put into final shape, after the author's lamented decease, by Professor Lloyd Morgan. It was, he tells us, merely necessary to arrange the order of the materials in a couple of chapters. For the concluding portion are reserved the topics of Isolation and Physiological Selection. The present volume is marked by all the candor, fairness, and moderation which Mr. Romanes' readers had learnt to expect from him, and its results are summarized under the following eight heads: (1) The assertion that Natural Selection has been the sole source of species and specific characters is an a priori deduction from the theory. Hence (2) it cannot be met by an appeal to facts. The question is logical, not biological. (3) It claims, therefore, that all species (or all specific characters) are necessarily due to Natural Selection. (4) There is not, however, a necessary connection between the assertion that all species are due to Natural Selection and the assertion that all specific characteristics are useful. Moreover, Natural Selection is not primarily a theory of the origin of species, but only of adaptations, whether specific or generic. (5) It is not true that no other principle of change can operate in the presence of Natural Selection. That is only true of deleterious characters. Nor is it true that Natural Selection alone can give stability of specific characters. (6) Climate, Food, Sexual Selection, Isolation, and the Laws of Growth, somehow or other, are amply