Ɛpsilon

To W. G. Kemp   11 November [1874]

Down, | Beckenham, Kent.

Nov. 11th

Dear Sir

I am obliged by your note.1

I agree with you that the reproductive system of natural species must have been in some way modified in correlation with the variation which they have undergone. But why has not a single domestic var. of an animal or plant, many of which have been profoundly modified, been rendered mutually sterile?2

Until this can be answered, it cannot be said that we know anything definitely.

As I have said I suspect that the difference is due to organisms in a state of nature having been exposed for long periods to much more uniform conditions, than are those under domestication.—3

Dear Sir | Yours faithfully | Ch. Darwin

Postmark: NO 11 | 74

1
Kemp’s letter has not been found.
2
Sterility had long been regarded as a test of true species, and Thomas Henry Huxley had coined the term ‘physiological species’ to refer to a definition of species based on reproductive barriers between life-forms (T. H. Huxley 1863, pp. 106–8). CD had investigated cases of intra-specific sterility, especially in plants. He had come to believe that most plants were adapted to promote the intercrossing of distinct individuals (see, for example, ‘Illegitimate offspring of dimorphic and trimorphic plants’). CD had discussed differences in wild and domestic animals and plants and the fertility of domestic varieties with their wild progenitors in Variation.
3
See Variation 2: 190–1.

Manuscript Alterations and Comments

2.1 that] interl
2.1 have] interl

Please cite as “DCP-LETT-9716F,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-9716F