Cave fishes are all extremely sensitive to light, which affects them disagreeably, even when the optic nerve is wholly destroyed. See Armand Viré, La Faune Actuelle des Cavernes, _Revue des Idées_, March 15, 1905, and La Faune Souterraine de France, 1900. [55] A. R. Wallace, Darwinism, chapters III. and XV. [56] Origin of Species, chapter II. [57] Sexual selection—the competition of males and females for their mates—is merely a form of natural selection, and need not be specially dealt with here. [58] Origin of Species, chapter V. [59] See Eimer, Organic Evolution (Eng. trans.), pp. 173-184, for a full discussion of the question from the Lamarckian standpoint. [60] ‘Right-handedness and Left-brainedness’ by D. J. Cunningham: the Huxley Lecture for 1902. Printed in the _Journal of the Anthropological Institute_, Vol. XXXII, pp. 273-95. I may refer also to a brochure by Dr. Geo. Sigerson, F.R.U.I., Consideration of the Structural and Acquisitional Elements in Dextral Pre-eminence, Dublin, 1884. Dr. Sigerson believes that primitive man was ambidextrous, and that ‘dexterity’ is a case of specialization of function, and has supported this view by a novel and interesting line of pathological observation. [61] _Op. cit._, p. 285. [62] _Ibid._, pp. 284-5. [63] _Journal of Anatomy and Physiology_, Vol. XXXVI, p. 401. ‘On the relative weights of the right and left sides of the body in the foetus.’ [64] Origin of Species, chap. VI. [65] ‘The Inadequacy of Natural Selection,’ Herbert Spencer. _Contemporary Review_, February and March, 1893. ‘Prof. Weismann’s Theories,’ Herbert Spencer. _Contemporary Review_, May, 1893. ‘The All-Sufficiency of Natural Selection,’ Aug. Weismann. _Contemporary Review_, September, 1893. ‘A Rejoinder to Prof. Weismann,’ Herbert Spencer. _Contemporary Review_, December, 1893. The Romanes Lecture for 1894, by Aug. Weismann (Frowde). [66] ‘Lamarck et le Transformisme actuel’: Muséum d’Histoire Naturelle, Centenaire; Vol. Commemoratif, 1903, p. 508. M. Perrier adds that the metaphysical alternative “est, en effet, à quoi le professeur A. Weismann, de Fribourg, a été conduit.” This, I think, can only be M. Perrier’s way of saying that he finds Weismann unintelligible, for Weismann’s ostensible object is certainly to steer between the Scylla of Lamarckism and the Charybdis of ‘metaphysics.’ With what success he attempts this feat we shall see. [67] The Evolution Theory, II, p. 78. [68] II, p. 330 _sqq._ [69] The Evolution Theory, II., 346. [70] See p. 83. [71] The Evolution Theory, II, 264. [72] I take this from J. T. Cunningham’s Sexual Dimorphism, p. 16. [73] Useless structures and organs are regarded by Weismann, and I think with justice, as in some degree unfavourable. They make demands on the organism for nourishment, and are thus in the position of non-productive members of a working family. [74] _Op. cit._, p. 73. See Appendix B. [75] Wallace, Darwinism, p. 24. [76] Animal Coloration, p. 252.