Ɛpsilon

From George Brettingham Sowerby   17 February 1868

164 Euston Road, N.W.

Feb. 17. 1868

Chas. Darwin Esq.

Dear Sir

My Son, who is now married & lives at our place in Great Russell Street, forgot to give me your letter till three days after receipt.1 Then, before replying, I wanted to see Mr. Jeffreys & when I called he was out of town, and I could not see him till this morning. In the work which he is publishing on British Mollusca he enters largely into the subjects of embryology, sex &c—and tells me that he has ascertained by anatomical investigations & by observation of acts of living animals in a great number of specimens, that in several species the different sexes are represented by different forms (not colours) in the shells.2 The two best ascertained instances of this are the common winkle—Littorina littorea, & the Lammellaria.

The shell of the male winkle is narrower & has a more produced spine, while that of the female has the body whorl larger & more ventricose. The shell of the Lamellaria is ear-shaped— authors make two British species—one flat, named L. tentaculata, the other round & inflated, named L. perspicua— They are the male & female of the same species.3

In the cases of the British Museum there are specimens of many species of N. American Univs & Anodons which have been labelled “male” & “female” by Lea the American conchologist—4 That author, I believe, holds that the sexes are separate—and that the shells of the females are shorter & thicker, and have the lower or opening margin of the valves more swelled than those of the males. (no difference in colour). Mr. Jeffreys, on the other hand, believes that the Bivalves are hermaphrodite—and that the differences in the shells are only local variations.5 I believe, oysters are now prooved Hermaphrodites— In the other cases, in the absence of coition, (which cannot take place)—the only communication would be by chance transmission through the waters. Still, I cannot pretend to decide the question.

I shall be happy to make any enquiries you may wish for & remain Dear Sir | Yours truly | G B Sowerby.

P.S. Allow me to offer my congratulations to you on the University achievements of my well-remembered friend George.6

CD annotations

1.1 My Son, … specimens, 1.7] crossed pencil
1.3 Mr. Jeffreys] underl red crayon
1.7 that in … shells. 1.8] scored red crayon
1.8 The two … conchologist— 3.3] crossed pencil
1.9 Littorina littorea] underl red crayon
2.1 The shell … same species. 2.5] ‘But these differences have no relation to secondary sexual characters’7 added ink
2.2 female] underl red crayon
2.2 body whorl … ventricose.] underl red crayon
Top of letter: ‘Used’ pencil circled pencil
1
CD’s letter has not been found. Sowerby’s son was George Brettingham Sowerby (1843–1921).
2
Sowerby refers to the conchologist John Gwyn Jeffreys and to Jeffreys 1862–9.
3
CD cited information from Jeffreys on the gastropod mollusc Littorina littorea (family Littorinidae, the common periwinkle) in Descent 1: 324. Lamellaria tentaculata is now L. latens (family Lamellariidae). Lamellaria perspicua is a distinct species.
4
Isaac Lea was a specialist in freshwater molluscs. He identified specimens of the bivalve mollusc family Unionidae (which includes the genus Anodonta) in the British Museum, and in other European collections (DSB).
5
CD noted that hermaphroditism was ‘not rare’ in bivalve shells in Descent 1: 324.
6
George Howard Darwin had attained second place in the final examination of the mathematical tripos at Cambridge (Cambridge University calendar 1868).
7
CD concluded that the differences between male and female molluscs described by Jeffreys were not a product of sexual selection in Descent 1: 324.

Please cite as “DCP-LETT-5887,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-5887