[34] The term "Vertebrata" denotes that large group of animals which are characterized by the possession of a spinal column, commonly known as the "backbone." Such animals are ourselves, together with all beasts, birds, reptiles, frogs, toads, and efts, and also fishes.
[35] It is hardly necessary to observe that these "sea-snakes" have no relation to the often-talked-of "sea-serpent." They are small, venomous reptiles, which abound in the Indian seas.
[36] "Origin of Species," 5th edit., 1869, p. 179.
[37] "Origin of Species," 5th edit., p. 532.
[38] Mr. A. D. Bartlett, of the Zoological Society, informs me that at these periods female apes admit with perfect readiness the access of any males of different species. To be sure this is in confinement; but the fact is, I think, quite conclusive against any such sexual selection in a state of nature as would account for the local coloration referred to.
[39] Mr. Darwin, in the last (fifth) edition of "Natural Selection," 1869, p. 102, admits that all sexual differences are not to be attributed to the agency of sexual selection, mentioning the wattle of carrier pigeons, tuft of turkey-cock, &c. These characters, however, seem less inexplicable by sexual selection than those given in the text.
[40] I am again indebted to the kindness of Mr. A. D. Bartlett, amongst others. That gentleman informs me that, so far from any mental emotion being produced in rabbits by the presence and movements of snakes, that he has actually seen a male and female rabbit satisfy the sexual instinct in that presence, a rabbit being seized by a snake when in coitu.
[41] "Habit and Intelligence," vol. i. p. 319.
[42] The reader may consult Huxley's "Lessons in Elementary Physiology," p. 204.
[43] "Natural Selection," p. 350.