More on the "terrible problem" of natural selection and sterility. CD’s reasons for disagreeing with ARW. CD analyses and answers ARW in detail in defence of his conclusion that sterility cannot be increased through natural selection.

If CD is not convinced by his notes on sterility, ARW has little doubt that he is wrong. In fact he was only half-convinced by his own arguments.

Modifies his first proposition [a species varies occasionally in two directions, but owing to free inter-crossing the variations never increase] and further discusses the subject.

Encloses Berthold Seemann’s notes on flora of the Hawaiian Islands. Presence of European alpine species in Hawaiian volcanoes is a "hard nut" for geographical distribution [but see ARW’s Island life (1880), p. 323].

Warns ARW of dubious character of list of European alpine genera and species in volcanoes of Hawaii. Problems of geographical distribution in oceanic islands.

Admires ARW’s "Theory of birds’ nests" [J. Travel & Nat. Hist. 1 (1868): 73].

Discusses their respective views on birds’ nests, sexual selection, and protection.

Asks why, if brilliant colours of female butterflies are result of protective mimicry, do not males become equally brilliant? CD believes variation in females alone accounts for it, rather than protection.

Various topics related to sexual selection: sexual differences, sexual preferences, coloration.

More on CD’s objections to ARW’s views on protection and natural selection.

Sexual selection.