Short reply to ARW’s long letter. Reaffirms belief in sexual selection.

Postscript on M.-J.-P. Flourens’ "little dull book against me" [Examen du livre de M. Darwin (1864)].

His distress that his engagement has been broken off.

Sends copies of two papers ["On the parrots of the Malayan region", Proc. Zool. Soc. Lond. (1864): 279–97;

"On the physical geography of the Malay Archipelago", J. R. Geogr. Soc. 33 (1863): 217–34].

Commends ARW’s papers on parrots

and on the theory of geographical distribution [see 4750].

Wild pigs in Aru Islands must have been introduced and later ran wild. Does ARW have an opinion on the subject?

Sends papers with comments. Convinced that the Aru pig is a species peculiar to New Guinea fauna, not a domestic animal that ran wild.

Admires CD’s paper ["Three forms of Lythrum", Collected papers 2: 106–31].

Exchange of photographs.

Aru pigs present perplexing case, whether wild or domesticated.

Thanks CD for paper ["Climbing plants"].

Reports case of variation becoming at once hereditary – a crested blackbird with crested young.

Crests as inherited variations; domesticated birds.

Belief in value of travel journals.

Current reading.

Information concerning improvements in the Reader under new sponsorship.

Current reading and work [on pigeons for Ibis 1 (1865): 365–400, and catalogue of his collection of birds].

Book of travels postponed indefinitely.

Welcomes ARW’s paper on pigeons ["On the pigeons of the Malay Archipelago", Ibis 1 (1865): 365–400].

Influence of monkeys on distribution of pigeons and parrots.

Asks ARW to explain a passage in his paper on Malayan Papilionidae [Trans. Linn. Soc. Lond. 25 (1866): 1–71] on how dimorphic forms are produced. CD knows of varieties "that will not blend or intermix", but which produce offspring quite like either parent.

ARW’s remarks on geographical distribution in Celebes "will give a cold shudder to the immutable naturalists".

Presses ARW to work on his travel journal.

Looks forward to reading Variation.

Explains how two or more female forms occur in one species through selection. The physiological problem remains of how each produces offspring like the other without intermediates. Is not CD’s case of varieties that will not blend the physiological test of a species needed for "complete proof of the origin of species"?

"Travels" postponed.

ARW’s simple explanation of dimorphic forms is satisfactory.

On "non-blending" of certain varieties, CD thinks ARW has not understood him. He does not refer to fertility. He crossed two differently coloured varieties of peas and "got both varieties perfect, but none intermediate". Something like this must occur in ARW’s butterflies.

Lengthy analysis of sources of misunderstanding of natural selection. Advocacy of Spencer’s term "survival of the fittest" instead of "Natural Selection". ARW urges CD to stress frequency of variations.

CD considers "the survival of the fittest" as alternative term to "Natural Selection". Reflections upon misunderstanding and his own ambiguity.

Health improved; can now work "some hours daily".

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.