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.

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.

Feels it would be worth while but difficult to investigate mimicked and mimicking forms for structural similarities that would indicate a closer alliance in the past.