skip to content

Darwin Correspondence Project

To G. H. K. Thwaites   26 March 1877

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

Mar 26. 1877

Dear Thwaites,

I have just been looking with very great interest at the specimens which you have been so kind as to send me. The difference between the male & female is wonderful, & almost reminds me of my old friends the complemental males of certain cirripedes.1 I hope Westwood will make a very interesting paper on the subject. I wonder whether they play any part in the fertilisation of the fig,—a subject Dr Crüger in the W. Indies was beginning to attend just before his death.2

The day before yesterday I was pleased to hear some account of you in a letter from Miss North which was sent me to read by a mutual friend, & in which she speaks with having many pleasant walks with you in the evenings.3 Do you remember sending me several years ago flowers of Oxalis sensitiva in spirits? I have only just examined them, & find them beautifully trimorphic, & in addition bearing cleistogamic flowers, which to my great surprise are long-styled, mid-styled, & short-styled like the perfect flowers; & this was quite a new fact to me.4

With all good wishes for your health & with many thanks | I remain, dear Thwaites | Yours sincerely | Charles Darwin


Thwaites’s letter has not been found, but he sent CD insects that were parasitic on fig fruit; see letter from G. H. K. Thwaites, 28 August 1877. CD discovered ‘complemental males’ in several species of Cirripedia; he observed minute males attached to the bodies of hermaphrodites, and differing greatly from them in size and structure (see Living Cirripedia (1851), pp. 231–2 and 281–93, Living Cirripedia (1854), pp. 23–30, and Newman 1993, pp. 377–81).
John Obadiah Westwood published on specimens of fig wasps sent to him by Thwaites in Westwood 1882, pp. 39–44, and Westwood 1883, pp. 375–8. Hermann Crüger published on figs’ requiring insects for fertilisation in Crüger 1851. Shortly before his death in 1864, Crüger was performing experiments suggested by CD to verify this (see Correspondence vol. 12, letter from Hermann Crüger, 21 January 1864).
In 1877, Marianne North visited Ceylon (now Sri Lanka) where Thwaites lived (ODNB); the ‘mutual friend’ was probably Joseph Dalton Hooker.
CD had mentioned Oxalis (the genus of woodsorrels) to Thwaites in his letter of 20 June [1862] (Correspondence vol. 10). He described specimens of Oxalis sensitiva (a synonym of Biophytum sensitivum) sent by Thwaites in Forms of flowers, p. 181, and on pp. 322–3, suggested that the three cleistogamic forms could be accounted for by the principle of correlated growth.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Crüger, Hermann. 1851. Ueber Befruchtung bei den Orangen. Botanische Zeitung 9: 57–63, 73–80.

Forms of flowers: The different forms of flowers on plants of the same species. By Charles Darwin. London: John Murray. 1877.

Living Cirripedia (1851): A monograph of the sub-class Cirripedia, with figures of all the species. The Lepadidæ; or, pedunculated cirripedes. By Charles Darwin. London: Ray Society. 1851.

Living Cirripedia (1854): A monograph of the sub-class Cirripedia, with figures of all the species. The Balanidæ (or sessile cirripedes); the Verrucidæ, etc. By Charles Darwin. London: Ray Society. 1854.

Newman, William A. 1993. Darwin and cirripedology. History of Carcinology. Crustacean Issues 8: 349–434.

ODNB: Oxford dictionary of national biography: from the earliest times to the year 2000. (Revised edition.) Edited by H. C. G. Matthew and Brian Harrison. 60 vols. and index. Oxford: Oxford University Press. 2004.

Westwood, John Obadiah. 1882. Further descriptions of insects infesting figs. [Read 4 October 1882.] Transactions of the Royal Entomological Society of London (1883): 29–47.

Westwood, John Obadiah. 1883. Further notice concerning the fig-insects of Ceylon. [Read 4 July 1883.] Transactions of the Royal Entomological Society of London 31: 375–81.


Thanks for specimens [of insects].

Wonders whether difference between male and female plays part in fertilisation of fig.

Flowers of Oxalis sensitiva, sent long ago, are trimorphic and cleistogamic.

Letter details

Letter no.
Charles Robert Darwin
George Henry Kendrick Thwaites
Sent from
Source of text
American Philosophical Society (Mss.B.D25.508)
Physical description
LS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 10913,” accessed on 25 March 2023,