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Darwin Correspondence Project

To A. R. Wallace   23 September [1868]1

Down Bromley Kent

Sept. 23d

My dear Wallace

I am very much obliged for all your trouble in writing me your long letter, which I will keep by me & ponder over.2 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.3 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. 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;4 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.5 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.—6 But I cannot yet persuade myself 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.—7 I cannot think so; anymore than I can that the considerable differences between ♀ & ♂ House Sparrow—or much greater brightness of ♂ Parus cæruleus (both of which build under cover) than of ♀ Parus, are related to protection.—8 I even misdoubt much whether less blackness of ♀ Blackbird is for protection.—

Again can you give me reason for believing that the modest differences between female Pheasants, the female Gallus bankiva, female of Black-Grouse—the PeaHen—female Partridge, have all special reference to protection under slightly different conditions.—9 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 partial transference of colour from the male; & by other means too long to specify; but I earnestly wish to see 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 fishes10—& 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 the other sex was checked by selection.—11

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

Believe me | My dear Wallace | Yours very sincerely | Ch Darwin

XXX addendum

It is not enough that females shd be produced from the males with red feathers, which 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.12 Such latent tendency wd be shown by their producing the red feathers when old or diseased in their ovaria.—

Footnotes

The year is established by the relationship between this letter and the letter from A. R. Wallace, 18 September [1868].
Letter from A. R. Wallace, 18 September [1868].
CD was writing the portion of Descent on sexual selection and birds (see CD’s ‘Journal’ (Correspondence vol. 16, Appendix II), and letter to A. R. Wallace, 19 August [1868]).
For CD’s and Wallace’s differing opinions on coloration in birds and insects, see the letter to A. R. Wallace, 16 September [1868] and n. 4. On the transmission of characters to one sex alone, see the letter from A. R. Wallace, 18 September [1868] and n. 4. In Descent 2: 155–8, CD began what he called ‘a tedious discussion’ as to whether a character inherited at first by both sexes could later be transmitted to one sex alone. CD’s notes on the differences in colour in male and female birds are in DAR 84; see especially DAR 84.2: 2–22, 174–81, 215–16.
See Descent 1: 284–5, 2: 158–60. CD’s notes on the question are in DAR 84.2: 16.
CD refers especially to A. R. Wallace 1864 (‘On the phenomena of variation and geographical distribution as illustrated by the Papilionidæ of the Malayan region’), [A. R. Wallace] 1867b (‘Mimicry and other protective resemblances among animals’), and A. R. Wallace 1868 (‘A theory of birds’ nests: shewing the relation of certain sexual differences of colour in birds to their mode of nidification’). In the portion of Descent on sexual selection, CD often referred to and evaluated Wallace’s notions of the role of protection in the derivation of secondary sexual characteristics (see especially Descent 1: 403–14, and 2: 154–80 ).
The golden-crest wren is sometimes called the goldcrest or kinglet (Regulus regulus or R. cristatus), and is not a true wren; like the other birds mentioned, it does not build a concealed nest.
CD referred to Parus caeruleus (now Cyanistes caeruleus), the ‘blue tomtit’, or blue tit, in Descent 2: 174, as one of several species that built concealed nests, yet in which the females were less conspicuous than the males.
These birds are in the order Galliformes, and some authors place them all in the family Phasianidae. CD referred to some of these birds when considering the origin of the less vivid colours of females; see Descent 2: 187–200. Gallus bankiva is now G. gallus, the red junglefowl.
See letter from Louis Agassiz, 22 July 1868. Notes in DAR 82 indicate that CD also acquired information on male incubating fish from Albert Günther; see also Descent 2: 19–23. See DAR 82: B6 for CD’s notes on his and Wallace’s views on fish colours.
Wallace had referred to butterflies where only the female mimicked the bright colours of another genus (see letter from A. R. Wallace, 18 September [1868] and n. 7).
CD discussed the transmission of latent characters in both the female and male in Variation 2: 51–4. See also Descent 2: 156–7.

Summary

On their differences concerning sexual selection and protection.

Letter details

Letter no.
DCP-LETT-6386
From
Charles Robert Darwin
To
Alfred Russel Wallace
Sent from
Down
Source of text
British Library (Add 46434: 153–6)
Physical description
7pp

Please cite as

Darwin Correspondence Project, “Letter no. 6386,” accessed on 19 April 2019, http://www.darwinproject.ac.uk/DCP-LETT-6386

Also published in The Correspondence of Charles Darwin, vol. 16

letter