[CW]"Darwinism," p. 172.
[CX]See "Animals and Plants under Domestication," vol. ii. p. 80.
[CY]"Darwinism," p. 332.
[CZ]"The Colour-Sense," by Grant Allen, p. 95.
[DA]That on "The Emotions of Animals" (X.).
[DB]"Darwinism," p. 318.
[DC]Natural History Society of Wisconsin, vol. i. (1889).
[DD]"Darwinism," p. 286.
[DE]On the negative character of disuse, see p. 196.
[DF]Cope, "Origin of the Fittest," p. 374.