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Down, Bromley, Kent, S.E.,

January 19, 1867.

My DEAR SIR,

Will you have the kindness to give me some information on one point? Not long since I was speaking to Mr. Wallace about his mimetic butterflies, and I told him of the case of the Rhynchæa, of which the female is more beautiful than the male, with the young resembling the latter. He answered me that you at Nottingham had advanced this or some such case, and that you had simply explained it by the male being the incubator. I should be extremely obliged if you would give me any information on this head and allow me to quote you. The subject interests me greatly, as in the 4th Edition of the ''Origin" I gave the obvious explanation of female birds not being gaudily coloured, etc., on account of their incubating; | knew then of the Rhynchæa but passed over the case, from not having space and from its appearing to me quite inexplicable.

I hope that you will forgive me troubling you, and believe me, my dear Sir,

Yours sincerely,

CHARLES DARWIN.

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P.S.—As I am writing, I will ask one other question, for the chance of your being able to answer it. Does the male black Australian swan, or the black and white S. American swan, differ from the females in plumage? i.e in the intensity of the black, or in the amount of black in the black-necked species?

Down, Bromley, Kent, S.E.,

March 4, 1867.

My DEAR SIR,

Very many thanks about the Dotterel, and I am pleased to hear of this additional evidence. I have looked to Swinhoe's papers, but the case does not seem very conclusive. After writing to you I remembered that the female of the Carrion-hawk of the Falkland I's. (formerly called Polyborus N. Zealandii) is very much brighter coloured than the male, as I ascertained ("Zool. Voyage of Beagle: Birds") by dissection; I have written to the Missionaries there about its nidification and if I receive any answer, will inform you.

The other day I thought I had got a case at the Zoological Gardens in the Casuarmus galeatus, in which the female has the finest and brightest caruncles, etc., but Sclater tells me it would be rash to trust to the comparison of a single pair, and he tells me that the male Ostrich has the finest plumes.

With my best thanks,

I remain my dear Sir,

Yours very sincerely,

CHARLES DARWIN.

P.S.—Mr. Blyth tells me that according to Jerdan the natives say the male Turnix alone incubates and attends to young.

There is another consideration which might lead to the female being the most beautiful, viz., if they were the more numerous than the males and the species were not polygamous, for in this case the more beautiful females would be selected.