WCP4214

[1]

Parkstone, Dorset.

Jan[uar]^y 4^th. 1891

Dear Mr. Cockerell,

I return you the catalogue of Land Shells, — and am greatly obliged for the trouble you are taking in this matter.

As you seem to have made a special study of these groups perhaps you will at the same time endeavour to arrive at some conclusion on the question whether the peculiar British forms — species or varieties — have been differentiated since the glacial epoch, or whether any of them may be supposed to be survivals from pre-glacial times [2] which owe their preservation to the more favourable climatic conditions and more limited competitors & enemies than on the continent.

The number of species & varieties of land & fresh water shells ^{inhabiting Britain} seems to me to be too great to have mostly migrated into Britain during the very brief union with the Continent since the glacial epoch. They would, I apprehend, have been able to survive wherever some land ^occurred free from ice in summer. The proportion of the number of ^{British to Continental} species as compared with the same proportion in flowering [3] plants would almost settle this point, since the facilities for dispersion and migration are almost at a minimum in the former group and at a maximum in the latter. The species of France, ¹Belgium & Scandinavia might in both cases be compared with those of Britain. I am glad this question of peculiar British forms is now attracting more attention than it did 10 years ago, when botanists, entomologists, conchologists alike almost scouted the idea of any British species being really peculiar. J. Gywn Jeffreys² for shells & Dr. Sharp³for beetles both strongly expressed [4] this view, as did H.C. Watson⁴ for plants. Some of them seemed to see that some amount of differentiation was probable, on any theory but special creation.

Yours very faithfully | Alfred R. Wallace— [signature]