Thanks RM for information on case of hexadactyly [see RM’s paper, "Hexadactylism", Land and Water, 11 March 1871, p. 179.

Mentions the difficulties in explaining the separation of sexes and Carl Nägeli’s view that the sexes of plants were primordially distinct.

Has been experimenting for five or six years to demonstrate that the benefits of crossing are the same as those derived from a slight change of conditions.

Cannot accept JJW’s invitation to a party. His health has been worse than usual for some months – can see no one nor can he go anywhere.

Is preparing a cheap edition of the Origin [6th] and will answer Mivart’s objections.

CD is pleased JJW likes C. Wright’s "Darwinism" [see 7940]. Huxley will publish a splendid review of it in Contemporary Review [Nov 1871].

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.

Thanks RM for note on ocelli.

Forwards photograph, sent by [J. L. G.] Krefft, of a chrysalis attached to its food-plant; the chrysalis has adjusted its colour remarkably.

Thanks RM for his paper on mimicry.

Cannot answer RM’s query because he believes it impossible to define large variations.

Believes monstrosities are generally injurious and are not often, if ever, taken advantage of in nature.