My dear Sir,

Along with this I have taken the liberty of sending an essay on Bos longifrons that contains a very interesting letter of Lord Selkirks on the breeding out of horns in the Galloway Breed of cattle—p 177 note,¹ thinking that you might be interested in the clear proof of the disappearance of so pronounced a character under the selection of man in so short a time as 80 years.

There is one important fact bearing on development, which I hope to publish in the winter—the lineal descent of the recent species of Rhinoceros from the Palæo- and Paloplotheria.² I have taken the dentition as the standard of comparison, and I find nearly all the intermediate forms that connect the two extremes. The characters scattered among, and as I believe inherited by, the more recent species converge in the older, and the whole form a finely graduated series. My method of work has been to take the elements of form in the most differentiated teeth and express them by symbols a, b, and the like, and thus I find I can express the measure of differentiation from the Palæotherium, or Paloplotherium of the Eocene.

The carnivores approached in a similar way lead to similar results. Would you be kind enough to tell me whether you consider this method a safe one? Its practical working I find of the utmost value in determining Pleistocene, Pliocene, and Eocene mammals.

Apologising for this intrusion | I am | My dear Sir | Yours truly | W. Boyd Dawkins

Charles Darwin Esq. F.R.S.