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Darwin Correspondence Project

To J. J. S. Steenstrup   20 May [1850]

Down Farnborough Kent

May 20th

My dear Sir

I thank you very sincerely for your last letter which answered all my long list of questions quite fully & satisfactorily.1 Mr. J. Sowerby (the author of Min: Conch:)2 is now drawing your specimens; but from having his hands very full of work he is, I am sorry to say, much delayed: for my own sake I do all I can to urge on his progress. I wait with eargerness to receive your northern Cirripedes & remarks: I am now at work on the Genus Balanus & very difficult I find it, as many species are quite undistinguishable by any one external character. I thank you much for the drawing of Lithotrya: I think I may have the same species from Timor: but the manner of boring here indicated is quite new to me.3

I have heard of your work on Hermaphroditism,4 but have not seen it, though I have long wished to do so; for on merely hypothetical grounds I have always thought Hermaphroditism improbable.5 Alas I cannot read Danish at all, & German with extreme difficulty. How much shame does your perfect English cause me!— You will perhaps be interested by hearing that I once found a Balanus which had had its probosciform organ cut off & healed absolutely imperforate, & yet the ova had been impregnated & contained larvæ; some of the neighbouring individuals in the cluster having certainly impregnated these ova.6 I have two cases of bisexual cirripedes, the male differing considerably from the female & being parasitic within the sack of the female.7

Pray believe me With feelings of much respect & gratitude, | Your’s sincerely | C. Darwin


Lithotrya nicobarica. For its manner of boring, see Living Cirripedia (1851): 336–47.
Steenstrup 1845a. In Living Cirripedia (1851): 55 n., CD referred to Steenstrup 1846 and thanked George Busk for providing him with an English translation from the German. He recorded having read this work on 28 November 1850 (DAR 119; Correspondence vol. 4, Appendix IV).
Living Cirripedia (1854): 271. CD doubted that animal hermaphrodites fertilised themselves; he believed cross-fertilisation was necessary between two such organisms (see Natural selection, pp. 42–6). His work on the sexual relationships of cirripedes was critical in establishing this belief (ibid., pp. 44–5).
See the description of specimens of Balanus balanoides from Tenby, South Wales (Living Cirripedia (1854): 101–2).
Ibla cumingii and Scalpellum ornatum (Living Cirripedia (1851): 189–203, 248–53).


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

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.

Natural selection: Charles Darwin’s Natural selection: being the second part of his big species book written from 1856 to 1858. Edited by R. C. Stauffer. Cambridge: Cambridge University Press. 1975.

Steenstrup, Johannes Japetus Smith. 1846. Untersuchungen über das Vorkommen des Hermaphroditismus in der Natur. Ein naturhistorischer Versuch. Translated from the Danish by Dr C. F. Hornschuch. Greifswald.


Describes progress in illustration of fossil cirripede specimens. Thanks for answers to questions. Comments on hermaphroditism. Describes his discovery of parasitic male cirripedes.

Letter details

Letter no.
Charles Robert Darwin
Johannes Japetus Smith (Japetus) Steenstrup
Sent from
Source of text
Det Kongelige Bibliotek, Copenhagen (NKS 3460 4to)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 1330,” accessed on 1 April 2020,

Also published in The Correspondence of Charles Darwin, vol. 4