Returns MS [of "Variation of species"]; several facts were new to him, especially interested in wagtails.
Wishes he could swallow Florent Prévost on sparrows ["Du régime alimentaire des oiseaux", C. R. Hebd. Acad. Sci. 46 (1858): 136–8].
LJ's facts seem to bear out CD's conclusion that secondary sexual characters were most variable of all.
Explains how he intends to deal with variation, and general facts in natural history in the light of species theory. Can only afford one chapter on variation in nature. It seems more important to make out variation in domestic animals.
Asks for facts on birds' nests for his chapter on instincts.
Moor Park, Farnham | Surrey
My dear Jenyns.
I return by this days post your M.S. & extremely much obliged I am for the loan. Several of the facts were new to me & I was especially interested by discussion on the Wagtails. The notes you kindly said I might retain. The selection of facts & not giving too many is one of my chief difficulties— I wish I could swallow Prevost's statement about the Sparrows, which was one of the cases, which I thought of giving.— I have given a short discussion, leading to the conclusion that “secondary sexual characters” were the most variable of all (under domestication & in nature) & several of your facts seem to bear this out.—
Gould repudiates the statement about the Swallows at Malta & says it was a blunder of Wollaston.
The pied Raven of Faroe is a good case of an incipient local race, yet sometimes crossing with common form.
I can afford only one long chapter to actual cases of variation in nature; for the mere accumulation of facts becomes, I think, intolerably dull.
It seems to me more important to try & make out a little, (& but a very little) about laws of variation in domestic animals & plants, & secondly to see how far general facts in Nat History & Geology seem best explained by each species having been separately created or having descended, like varieties, from other species. At least this is the way I mean to treat my work.—
Can you give me any facts on variations of Birds nests? more especially of same species in different countries.— I have treated this subject at some little length, as being the best case for showing variation of Instincts.
With very many thanks | Yours most truly | C. Darwin
One chief reason why I have not accumulated more facts of variation in state of nature is, that naturalists so invariably turn round & say oh they are not varieties, but species.—
- f1 2264.f1The second and last Wednesday of CD's stay at Moor Park hydropathic establishment. Although CD might have written the letter earlier, this date seems the most probable since he comments on the manuscript sent to him by Jenyns (see letter to Leonard Jenyns, 18 April ). The only other possible date is 21 April 1858, which would not have given CD much time to read and comment on the manuscript after receipt.
- f2 2264.f2The manuscript of Jenyns 1856, which CD had asked to see in his letter to Leonard Jenyns, 9 April . The manuscript and other notes by Jenyns were received by 18 April (see letter to Leonard Jenyns, 18 April ). CD's notes about Jenyns 1856 are in DAR 45: 25–8.
- f3 2264.f3Jenyns 1856, p. 103. CD copied out most of Jenyns's remarks about the difficulties of classifying wagtails in his notes (see n. 2, above). The passage on wagtails, to which CD refers, concludes:
It was observed … that if two closely-allied species are found living together always, without any individuals occurring of an intermediate kind, it is a strong argument for their being really distinct.
- f4 2264.f4Letter from Leonard Jenyns, [before 18 April 1858].
- f5 2264.f5CD refers to the ornithologist Florent Prévost, who divided sparrows into three groups according to their coloration and geographical location. Jenyns had referred to this case, without citing Prévost, in Jenyns 1856, p. 103.
- f6 2264.f6See Natural selection, pp. 307–18.
- f7 2264.f7Jenyns had cited a remark by John Gould, given in Wollaston 1856, that Maltese swallows were slightly different from British ones (Jenyns 1856, p. 104).
- f8 2264.f8See Natural selection, pp. 498–506.