Almost every side of zoology has contributed to the theory of evolution, but of special importance are the facts and theories associated with the names of Gregor Mendel, A. Weismann and Hugo de Vries. These are discussed under the headings [Heredity]; [Mendelism]; and [Variation and Selection]. It has been a feature of great promise in recent contributions to the theory of evolution, that such contributions have received attention almost directly in proportion to the new methods of observation and the new series of facts with which they have come. Those have found little favour who brought to the debate only formal criticisms or amplifications of the Darwinian arguments, or re-marshallings of the Darwinian facts, however ably conducted. The time has not yet come for the attempt to synthesize the results of the many different and often apparently antagonistic groups of workers. The great work that is going on is the simplification of the facts to be explained by grouping them under empirical laws; and the most general statement relating to these that can yet be made is that no single one of these laws has as yet shown signs of taking rank as a vera causa comparable with the Darwinian principle of natural selection.
For evolution in relation to society see [Sociology].
References.—Practically, every botanical and zoological publication of recent date has its bearing on evolution. The following are a few of the more general works: Bateson, Materials for the Study of Variation; Bunge, Vitalismus und Mechanismus; Cope, Origin of the Fittest, Primary Factors of Organic Evolution, Darwin’s Life and Letters; H. de Vries, Species and Varieties and their Origin by Mutation; Eimer, Organic Evolution; Gulick, “Divergent Evolution through Cumulative Segregation,” Jour. Linn. Soc. xx.; Haacke, Schöpfung des Menschen; Mitchell, “Valuation of Zoological Characters,” Trans. Linn. Soc. viii. pt. 7; Pearson, Grammar of Science; Romanes, Darwin and after Darwin; Sedgwick, Presidential Address to Section Zoology, Brit. Ass. Rep. 1899; Wallace, Darwinism; Weismann, The Germ-Plasm. Further references of great value will be found in the works of Bateson and Pearson referred to above, and in the annual volumes of the Zoological Record, particularly under the head “General Subject.”
(P. C. M.)
[1] This is brought out by F. Lassalle, Die Philosophie Herakleitos, p. 126.
[2] Zeller says that through this distinction Aristotle first made possible the idea of development.
[3] See this well brought out in G.H. Lewes’s Aristotle, p. 187.
[4] Grote calls attention to the contrast between Plato’s and Aristotle’s way of conceiving the gradations of mind (Aristotle, ii. 171).
[5] Zeller observes that this scale of decreasing perfection is a necessary consequence of the idea of a transcendent deity.