Summary

Thanks for Variation.

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

Summary

Responds to CD’s queries on polygamy in birds and orang.

Discusses sexual selection and secondary characters; colours and sexual preference.

Expresses his admiration for Pangenesis; it is superior to Herbert Spencer’s theory.

ARW differs somewhat with CD’s chapter on causes of variability [ch. 22 in Variation]. Thinks several of CD’s arguments are unsound.

Briefly discusses how natural selection might aid in producing sterility between allied species.

Summary

Offers enclosure demonstrating that natural selection could produce sterility of hybrids.

More on Pangenesis and the inadequacy of H. Spencer’s approach.

Summary

On critical exchanges at the Linnean Society on natural selection and mimicry.

Roland Trimen’s paper on South African mimetic butterflies ["On some remarkable mimetic resemblances among African butterflies", Trans. Linn. Soc. Lond. 26 (1870): 497–523; read 5 Mar 1868].

Summary

Coloration of butterflies; brilliantly coloured females.

Commends CD on his paper on specific differences in Primula [J. Proc. Linn. Soc. Lond. (Bot.) 10 (1869): 437–54; reprinted and revised in Forms of flowers] as a test-case proving origin of real species.

Summary

On sterility of natural species and natural selection. Closely allied forms from adjacent islands offer best chance of finding good species fertile inter se.

Problem of minute variations and sexual selection.

Summary

Returns George Darwin’s criticisms of his notes on sterility and sends further notes in reply. Since there are degrees of sterility between varieties, "is it not probable that natural selection can accumulate these variations?" Varieties that are adapted to new conditions could then survive and form new species without being isolated.

Summary

If CD is not convinced by his notes on sterility, ARW has little doubt that he is wrong. In fact he was only half-convinced by his own arguments.

Modifies his first proposition [a species varies occasionally in two directions, but owing to free inter-crossing the variations never increase] and further discusses the subject.

Encloses Berthold Seemann’s notes on flora of the Hawaiian Islands. Presence of European alpine species in Hawaiian volcanoes is a "hard nut" for geographical distribution [but see ARW’s Island life (1880), p. 323].

Summary

Various topics related to sexual selection: sexual differences, sexual preferences, coloration.

Summary

Answers CD’s objection [see 6121 and 6146] about sexual differences and protective colouring. Summarises his theory of colour in nature.

Summary

The problem of sterility, and its relation to natural selection.

George Bentham’s support of Darwinism.

Summary

On triumph of "Darwinianism".

Discussion of their differences on subject of protection.

Summary

Accepts invitation.

Summary

ARW’s wife will accompany him to Down.

Summary

On sounds produced by Euchirus longimanus beetle. Sends a pair by post.

Summary

Submits a 15–point argument against CD’s views on the coloration of female birds and insects.

Summary

Sexual differences in coloration. Sexual selection versus natural selection as explanations. ARW continues to argue against sexual selection, saying that natural selection, in keeping the female dull for protection, would account for differences in sexual colouring more effectively than inheritance and partial transmission of sexually selected male colours. Colours of female birds of paradise. Protective coloration. Disagrees with CD on coincidence of hidden nests and bright colours of females.