[21]

I quote from the second edition, as issued in 1881.

[22]

This is the theory which by many has alone been seen in Darwin's Descent of Man. Thus even his friend Wallace states unconditionally (Tropical Nature, p. 193) that Darwin accepted a "voluntary or conscious sexual selection," and seems to repeat the same statement in Darwinism (1889), p. 283. Lloyd Morgan, in his discussion of the pairing instinct in Habit and Instinct (1896), seems also only to see this side of Darwin's statement.

[23]

In his Variation of Animals and Plants under Domestication, Darwin was puzzled by the fact that, in captivity, animals often copulate without conceiving and failed to connect that fact with the processes behind his own theory of sexual selection.