[28] “Proceedings of the California Academy of Science,” vol. v, p. 152. 1873.
[29] For fuller discussion of this subject, see “Bulletin of the California Academy of Science,” No. 8, 1887, and “American Journal of Science,” for Dec., 1887.
[30] “Origin of Races of the Dog.” “Annals and Magazine of Natural History,” vol. xvii, p. 295. 1886.
[31] Mr. Galton (“Nature,” August 26, 1886) has used a diagram similar to the above (which I first used in 1879) to illustrate the law of sexual attraction and repugnance.
[32] This subject is more fully discussed by the author in an article entitled “Genesis of Sex,” in “The Popular Science Monthly,” vol. xvi, p. 167, 1879.
[33] For examples of this the reader is referred to Cope, “Bulletin of the National Museum,” No. 1; and to Coues’s “Key to North American Birds,” last edition.
[34] “Monatsbericht d. k. Preuss. Akademie d. Wissenschaft zu Berlin,” for July, 1866.
[35] “Genesis of Tertiary Species of Planorbis at Steinheim.” A. Hyatt, Anniversary Memoir of the Boston Society of Natural History, 1880.
[36] In a letter to the author, dated February 13, 1887, Prof. Cope says: “Such transitions of species are clearly indicated in the Oreodontidæ, where such different forms as O. gracilis and O. Culbertsoni are connected by intergradations.”
[37] “American Naturalist,” 1873; “Popular Science Monthly,” June, 1873.