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