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Darwin Correspondence Project

To Roland Trimen   16 January [1868]1

Down. | Bromley. | Kent. S.E.

Jan. 16th

My dear Mr Trimen

I really do not know how to thank you enough for all the great trouble which you have taken for me.— I never saw anything so beautiful as your drawings.2 I have examined them with the microscope!! When I asked for a sketch I never dreamed of your taking so great trouble.— Your letter & Proof-sheet give me exactly & fully the information which I wanted.3

I am very glad of the description of the ocellus in the S. African Saturnidæ: I had no idea it was so complex.—4 If you know of any case in Lepidoptera of ocelli regularly confined to the male, I shd. much like to hear of it, as it would illustrate a little better the case of the peacock, which has often been thrown in my teeth.—5 I doubt whether such cases exist, & if I do not hear I will understand that you know of no such case.

Again let me thank you cordially for your great kindness, & I remain. | Yours very sincerely | Ch. Darwin


The year is established by the relationship between this letter and the letter from Roland Trimen, 13 January 1868.
Trimen enclosed a sketch showing variation in the ocelli of the South African butterfly Cyllo leda (now Melanitis leda) with his letter of 13 January 1868.
Trimen enclosed proof-sheets from Trimen 1862–6, containing information on Cyllo leda, with his letter of 13 January 1868. See letter from Roland Trimen, 13 January 1868 and n. 2.
Trimen described the ocelli on several members of the moth family Saturniidae, including one species with nine distinct rings, in his letter of 13 January 1868.
George Douglas Campbell, the duke of Argyll, discussed the peacock’s plumage as an example of a beautiful structure that could only have arisen from God’s design (see Campbell 1867, pp. 203–4). CD used cases of gradation in males of allied gallinaceous species to argue that highly complex ornaments, such as the ocelli of the male peacock, could have been acquired by small successive steps. See Variation 2: 135–41. CD had once written to Asa Gray, with reference to the difficulties of explaining particular structures through natural selection: ‘The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!’ (Correspondence vol. 8, letter to Asa Gray, 3 April [1860]). See also Correspondence vol. 15, letter to A. R. Wallace, 29 April [1867], and letter to Charles Kingsley, 10 June [1867]. CD discussed why certain features such as the peacock’s tail might be transmitted to males of the species rather than females in Origin 4th ed., pp. 240–1. CD’s notes on the peacock’s tail are in DAR 84. See also letter from Roland Trimen, 13 January 1868, n. 11.


Campbell, George Douglas. 1867. The reign of law. London: Alexander Strahan.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Origin 4th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 4th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1866.

Trimen, Roland. 1862–6. Rhopalocera Africæ Australis; a catalogue of South African butterflies, comprising descriptions of all the known species with notices of their larvæ, pupæ, localities, habits, seasons of appearance, and geographical distribution. London: Trübner. Cape Town, South Africa: W. F. Mathew.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Thanks RT for drawings of ocelli, especially for the description of ocelli of S. African Saturniidae. Would like to know of any cases in which the ocelli are confined to the male, to illustrate better the case of the peacock.

Letter details

Letter no.
Charles Robert Darwin
Roland Trimen
Sent from
Source of text
Royal Entomological Society (Trimen papers, box 21: 63)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 5790,” accessed on 21 September 2021,

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