WCP1908

Down Bromley Kent

Sept. 23^d [1868]¹

My dear Wallace

I am very much obliged for all your trouble in writing me your long letter,² which I will keep by me & ponder over. To answer it would require at least 200 folio pages! If you could see how often I have rewritten some pages, you would know how anxious I am to arrive as near as I can to the truth. We differ, I think, chiefly from fixing our minds ^{perhaps too closely} on different points, on which we agree: I lay great stress on what I know takes place under domestication.. I think we start with different fundamental notions on inheritance. [2] I find it most difficult ^{but not, I think, impossible} to see how, for instance, a few red feathers appearing on the head of a male bird, & which are at first transmitted to both sexes, could come to be transmitted to males alone; ^XXX but I have no difficulty ^{in making the whole head red} if the few red feathers ^{in the males} from the first tended to be sexually transmitted. I am quite willing to admit that the female may have been modified, either at the same time or subsequently, ^{for protection} by the accumulation of variations limited in ^{their transmission} to the female sex. — I owe to your writings the consideration of this latter point. — But I cannot yet persuade myself myself [3] that females alone have often been modified for protection. — Should you grudge the trouble briefly to tell me, whether you believe that the plainer head & less bright colours of ♀ chaffinch, — the less red on the head & less clean colours of ♀ gold-finch — the much less red on breast of ♀ Bull-finch — the paler crest of Golden-crest Wren — &c — have been acquired by them for protection. — I cannot think so; anymore than I can ^that the considerable differences between ♀ & ♂ House Sparrow — or much greater brightness of ♂ Parus caeruleus (both of which build in nest under cover) than of ♀ Parus, are related to protection. — I even misdoubt [4] much whether less blackness of ♀ Blackbird is for protection. —

Again can you give me reason for believing that the modest differences between the female Pheasants, the female Gallus bankiva, female of Black-Grouse — of the Peacock the PeaHen — female Partridge, have all special reference to protection under slightly different conditions. — I of course admit that they are all protected by dull colours, derived, as I think, from some dull-ground progenitor; & I account partly for their difference by some partial transference of colour from the male; & ^by other means too long to specify; but I earnestly wish to see [5] reason to believe that each is specially adapted for concealment to its environment.

I grieve to differ from you, & it actually terrifies me & makes me constantly distrust myself. —

I fear we shall never quite understand each other. I value the cases of bright-coloured, incubating male fishes — & brilliant female butterflies, solely as showing that one sex may be made brilliant without any necessary transference of beauty to the other sex; for in these cases I cannot suppose that beauty in [6] the other sex was checked by selection. —

I fear this letter will trouble you to read it. — A very short answer about your belief in regard to the ♀ finches & gallinaceae would suffice. —

Believe me | My dear Wallace | Yours very sincerely | Ch Darwin [signature]

[7] XXX addendum

It is not enough that females sh[oul]^d be produced from the males with red feathers, & which are ^{should be} destitute of red feathers; but these females must have a latent tendency to produce such feathers, otherwise they would cause deterioration in the red head feathers of their male offspring. Such latent tendency w[oul]^d be shown if by their producing the red feathers when old or diseased in their ovaria. —