Schopenhauer, Arthur. _Le Monde comme Volonté et comme Representation_ 298
Sterrett, J. Macbride. _Studies in Hegel's Philosophy of Religion_ 133
Sterne, Carus. _Die allgemeine Weltanschauung_ 456
Taylor, Isaac. _The Origin of the Aryans_ 435
Ufer, Christian. _Geistesstörungen in der Schule_ 619
Wolff, Joh. _Das Bewusstsein und sein Object_ 147
PERIODICALS 157-160; 307-320; 459-480; 621-640
MR. A. R. WALLACE ON PHYSIOLOGICAL SELECTION.[1]
[1] In a private letter to the editor of this magazine Professor Geo. J. Romanes writes: "The article refers to a completely new departure in the theory of evolution, striking in the principle of homogamy, the root-principle of the whole, and in physiological selection, one of the main branches. Yet neither principle has so far been perceived except by Mr. Gulick.... The theory of physiological selection has been better understood in America than in this country; and I should like the naturalists there, who have taken such a warm and appreciative interest in it, to see my reply to Mr. Wallace published in an American periodical."
In 1886 I published a paper entitled "Physiological Selection: an additional suggestion on the origin of species," (Zoölogical Journal of the Linnean Society, Vol. XIX, p. 337). The view there expressed is, briefly, as follows.
Given the facts of heredity and variability, the whole theory of organic evolution becomes neither more nor less than a theory of the causes which determine the breeding of like with like, to the exclusion of unlike. For the more firmly that we believe in heredity with variability as the fundamental principle of organic evolution, the stronger must become our persuasion that segregate breeding (or exclusive mating of like with like) must lead to divergence, while indiscriminate breeding (or free intercrossing of all varieties) must lead to uniformity. So long as there is free intercrossing, heredity makes in favor of fixity of type—or, at most, can permit change only in a single line, where successive generations undergo a continuous improvement, which may give rise to a ladder-like series of species in time. But in order that there should be a tree-like multiplication of species in space, or a simultaneous divergence of type, it is essential that free intercrossing be prevented at the origin, and throughout the development, of each branch. In other words, it is only when assisted by some form of segregation—which determines exclusive breeding of like with like—that heredity can effect arborescent or polytypic, as distinguished from catenated or monotypic, evolution. For the sake of greater clearness, I will call segregation in this sense _homogamy_, or the exclusive mating of individuals which belong to the same variety.