646 Cf. Osborn, H. F., On the Origin of Single Characters, as observed in fossil and living Animals and Plants, Amer. Nat. XLIX, pp. 193ã239, 1915 (and other papers); ibid. p. 194, ãEach individual is composed of a vast number of somewhat similar new or old characters, each character has its independent and separate history, each character is in a certain stage of evolution, each character is correlated with the other characters of the individualã....ãThe real problem has always been that of the origin and development of characters. Since the Origin of Species appeared, the terms variation and variability have always referred to single characters; if a species is said to be variable, we mean that a considerable number of the single characters or groups of characters of which it is composed are variable,ã etc.
647 Cf. Sorby, Quart. Journ. Geol. Soc. (Proc.), 1879, p. 88.