Discusses his paper on mimicry and natural selection [Land and Water 9 (1871): 321]. Believes natural selection tends to fix mimetic characters rigidly.

Discusses the problems of mimicry as related to natural selection; the general variability of colour as a character; and the conditions necessary for natural selection to fix firmly a character.

Encloses a Fritz Müller letter speculating that organisms respond to certain colours because of the prevalence of those colours in their environment.

Discusses the roles of natural and sexual selection in producing mimicry, and the problem of explaining the cause of the first mimetic variation; considers the ideas of A. R. Wallace and Fritz Müller on this problem.

Invites RM to keep some specimens as long as he wishes.

Recalls vaguely the mention of a butterfly species in which the male alone is mimetic.