Ɛpsilon

To William Forsell Kirby   9 July [1863]

Down. | Bromley. | Kent. S.E.

July 9th

Dear Sir

I am very much obliged for the copy of your Paper on Geographical Distribution, but which I had already read in the Ent. Transacts.1 I have been very much interested by it & it seems to me excellently done. There was of course much new to me; & I have been particularly struck by your observations on the Corsican sub- species & on those of N. America.—2 It would be interesting if you could get a set of specimens from the Shetland Isld & see if you could observe the faintest trace of differentiation.—

with my best thanks, I remain | Dear Sir | Yours very faithfully | Ch. Darwin

Postmark: JY 10 63

1
Kirby 1863. CD’s annotated copy of the volume of the Transactions of the Entomological Society of London in which this paper appeared is in the Darwin Library–Down; the part containing Kirby 1863 was issued in May 1863. In 1862, Kirby had written to CD telling him of his belief in the mutability of species; in reply, CD had expressed a hope that Kirby would some day ‘write on variation in Butterflies’ and express his beliefs ‘on the subject of species’ (see Correspondence vol. 10, letter to W. F. Kirby, 12 December [1862]). In his paper, Kirby discussed the geographical distribution of species and sub-species of butterflies in Europe on the basis of CD’s theory (see especially Kirby 1863, pp. 481–2 and 491).
2
CD refers to Kirby’s comments on the role of geographical isolation in the production of new species and sub-species of butterflies in North America and Corsica, distinct from those in continental Europe (Kirby 1863, p. 491). Kirby observed: If geologists can tell us how long Corsica has been separated from the main land, we shall have some most reliable data by which to calculate the length of time that the formation of a species requires, for a large number of Corsican insects are already good species, and many more have become sub-species, which is the last step towards the formation of a new species.

Manuscript Alterations and Comments

1.3 it seems] ‘it’ interl

Please cite as “DCP-LETT-4237,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-4237