[15] See Nineteenth Century, January, 1887, pp. 61, 62.
[16] Nicaragua, p. 207.
[17] Nature, vol. xxxi. p. 4.
[18] Zool. Journal, Lin. Soc., vol. xix. pp. 337-411 (1886); and for Mr. Gulick's papers, ibid., vol. xx. pp. 189-274 (1887), vol. xxiii. pp. 312-380 (1889). Mr. Gulick has recently drawn my attention, in a private letter, to the fact that as early as 1872 a paper of his was read at the British Association, bearing the title Diversity of Evolution under one set of External Conditions, and that here the principle of physiological segregation is stated. Although it does not appear that Mr. Gulick then appreciated the great importance of this principle, it entitles him to claim priority.
[19] Darwinism, p. 169.
[20] Origin of Species, p. 136.
[21] Darwinism, p. 152.
[22] Origin of Species, pp. 44, 45.
[23] Origin of Species, ed. 6, pp. 134, 135.
[24] Archives des Sciences physiques et naturelles (Genève), vol. liii. (1875), pp. 211-236.