Thanks CD for 4th ed. of Origin.

Discusses abnormal sexual characters produced by mimicry. ARW’s papers on the subject.

Agassiz’s "marvellous" Amazonian glacier theory.

Will call on Wallace tomorrow (Saturday) at 10.

Asks why caterpillars are sometimes beautifully coloured. It poses a problem for view that sexual selection is the explanation of colours of male butterflies.

More on mimetic butterflies.

Protective role of colours in caterpillars and butterflies. Sexual differences in colours of butterflies.

ARW’s explanation of protective value of conspicuous coloration is ingenious.

CD still holds to sexual selection with respect to beauty in male butterflies.

Sexual selection and the races of man.

Expression of emotions is another subject he plans to include in his essay [Descent].

Asks ARW to suggest an observer in Malay Archipelago to whom he might send queries [on expression].

Pleased that CD approves his idea about caterpillars.

Thinks CD is right about selection in butterflies, but still believes protective adaptation has kept down colours of females.

Cannot yet see action of natural selection in forming the races of man.

Grateful for addresses of informants, especially that of Rajah James Brooke.

Dispatch of queries on expression. Answers will make interesting appendix to his "Essay on man" [Descent].

Protective adaptation of female butterflies believed probable.

Believes in sexual selection as applied to man.

ARW responds to CD’s list of queries about expression. Suggests acquiring informants through publishing the queries in newspapers. His doubts about their importance.

Has submitted caterpillar question to Entomological Society.

Asks to be kept informed on gaudy caterpillars.

Problems of his work on man; scope and role of sexual selection.

Indulgence of interest in expression is simply a "hobby-horse". Will see whether he can get queries inserted in an Indian newspaper.

Describes his view on colour [of plumage] of males and females – i.e., that absence of brilliant colour in either sex is due to need for protection in incubation, rather than to sexual selection.

Comments on ARW’s view of colouring in relation to sexual selection and protection. It is not new to CD. Hopes to discuss subject fully in his "Essay on Man" [Descent]. As to the problem of brightly coloured females, CD is not satisfied that it is due to males taking over incubation. Admires "value and beauty" of ARW’s generalisations.

Never imagined that the facts about sexual selection could be new to CD. Thought fact that brightly coloured females build concealed nests and almost all those in which sexes differ remarkably build exposed nests might be new to him. Some problems remain. Sends his notes for CD to use if he wants.

Returns ARW’s notes. He will work up subject much better than CD.

Apologises for the note of illiberality in his letter regarding ARW’s work on the colouring and other sexual differences in mammals.

Discusses laws of inheritance based on sexual selection.

He questions the extent of applicability of principles of protection and sexual selection to lower animal forms, though Ernst Haeckel has shown how protection may account for transparency and absence of colour in lower oceanic animals.

CD is invited to see ARW’s collections at Bayswater.

ARW has written an answer to the Duke of Argyll and North British Review criticisms.

CD now acknowledges that the sometimes very great sexual, i.e., ornamental, differences in fishes offer a difficulty to the view that females are not brightly coloured on account of the danger to propagation of the species.

Acknowledgment of article on mimicry [Westminster Rev. 88 (1867): 1–43].

Informs CD of his reply to Argyll and the North British Review criticisms [in "Creation by law", Q. J. Sci. 4 (1867): 471–88]. Cites "the predicted Madagascar moth" and Angraecum sesquipedale.

Birth of Herbert Spencer Wallace.

Response to ARW’s "Creation by law", especially the Angraecum sesquipedale and the predicted Madagascar moth.

ARW’s argument on beauty strikes CD as good.

Wishes ARW had made more clear the assumption of the reviewer [in North Br. Rev.] that each variation is a strongly marked one.

The Duke of Argyll’s argument on beauty is not candid.

Response to CD’s comments on "Creation by law" [see 5637].

The limits of variation discussed.

Thanks for Variation.

Reports work on his travel book [The Malay Archipelago (1869)].