[24] Thus Kirchenoff has said (Prorectoratsrede, Heidelberg, 1865), “The highest object at which the natural sciences are constrained to aim is the reduction of all the phenomena of nature to mechanics;” and Helmholtz has declared (Populaer Wissenschaft liche Vorträge, 1869), “The aim of the natural sciences is to resolve themselves into mechanics.” Wundt observes (Lehrbuch der Physiologie des Menschen), “The problem of physiology is a reduction of vital phenomena to general physical laws, and ultimately to the fundamental laws of mechanics;” while Haëckel tells us (Freie Wissenschaft und freie Lehre) that “all natural phenomena without exception, from the motions of the celestial bodies to the growth of plants and the consciousness of men ... are ultimately to be reduced to atomic mechanics.”
[25] In his work on The Unconscious, a translation of which has been lately published by Messrs. Trübner & Co.
[26] Mr. Darwin tells us that two topknotted canaries produce bald offspring, due probably to some conflicting actions analogous to the interference of light.
[27] See The Cat (John Murray, 1881), p. 7.
[28] See Archives de Zool. expér. vol. ii. p. 414 vol. v. p. 174, vol. vi. p. 31; also Ann. des Sci. Nat. 4 séries, Zoologie, vol. iii. p. 119, vol. xv. p. 1, vol. xvii. p. 243; and his work Recherches sur la production artificielle des Monstruositées ou essais de Tératogénie expérimentale.
[29] See Quarterly Journal of Micros. Soc., New Series, (1873), vol. xiii. p. 408, and vol. xvi. (1876) p. 27.
[30] Tropical Nature, pp. 254-259.
[31] Nature, 1576, June 8, p. 133. Schmankevitsch at Odessa.
[32] In the mathematical sense of the word.
[33] The existence of internal force must be allowed. We cannot conceive of a universe consisting of atoms acted on indeed by external forces, but having no internal power of response to such actions. Even in such conceptions as those of “physiological units” and “gemmules” we have (as the late Mr. G. H. Lewes remarked) given as an explanation that very power the existence of which in larger organisms had itself to be explained.