There is so much detail in Variation that WDF will never be able to finish it. Some chapters, like that on reversion, are "curious".

Is working on "Sexual selection"; asks WDF to send observations on birds’ finding new mates during breeding season [see Descent 2: 103–7].

Pairing habits of birds: polygamy among ducks and canaries.

Information on the proportion of sexes in fowls and other birds.

WDF’s letter gives CD the kind of facts he wants. His story about peacocks is so good that CD will quote it [Descent 2: 46].

Pleased WDF approves of his book [Variation]

– "beloved Pangenesis disagrees badly with many".

Regrets he cannot get to Down.

Reminds WDF to write about the "great magpie marriage". Sexual selection an "everlasting subject".

News of his children.

Asks for information on instances of sexual preference in animals and data on numbers of males and females born in various domesticated species.

Thanks CD for a recent letter.

Reports on his health, which has been bad for 12 months.

Sends extracts of works on domestication.

Discusses the pairing of various birds; comments on the pugnacity of partridges, pheasants, male guinea-fowl, and peacocks.

Gives proportions of sexes in pheasants.

Much interested in WDF’s letter on inheritance and courtship of birds. CD "in a great muddle" on many points.

Asks for further information on proportion of sexes in sheep.

Hybrid geese.

Proportions of sexes in sheep and cattle.

Pairing habits of crows.

Thanks WDF for information about sheep and cattle.

Mentions corrections for new edition of Origin [5th ed. (1869)].