To B. D. Walsh   19 December [1865]

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

Dec. 19.

My dear Sir

I am much obliged for your interesting letter of Nov. 12—1 I hope you will meet with the success which you well deserve in solving the very curious problem of the Cynips.2

I presume that you expect that the sexual brood, whenever it appears, would be more locomotive, & thus spread the species. On the other hand, the new gall which has appeared in England recently has spread very rapidly, & yet only females have been found.3 I received your paper on the potatoe bug & it seems to me uncommonly well done.4

Sir J. Lubbock & Mr Busk called here the other day5 & neither knew or believed in the male Daphnia laying eggs.6 The former would be almost sure to have heard of it. He believes in Wagner’s case of the breeding larva of the fly.7 I shd not be very much astonished at the Daphnia case, for certain male & female Medusæ whilst sexually mature throw off reproductive buds & if these buds were encased in a shell, they might be as undistinguishable from true eggs as the ovules & buds in Aphis.8

It is curious about the post office that I some months ago was expressing much indignation at your government being so particular about writing in, & sending, single pamphlets. There are no such rules within England & it seems that they apply only to the transit from one country to the other.9

I have done no work since April owing to my health, but have just begun some easy jobs, such as counting seeds of experimental Primulas; amongst others of seedlings from John Scott’s Primulas, & these afford widely different results from what he gives.10 I mention this because I see that you quote him.11

With every good wish pray believe me my dear Sir | yours very sincerely | Ch. Darwin

LS

Postmark: DE 20 65

2
In his paper on dimorphism in Cynips, Walsh had argued that there were two female forms of Cynips quercus spongifica, one agamous, the other sexual (Walsh 1864a). In his letter of 12 November 1865, he discussed his ongoing experiments at length, and suggested that the sexual or brood form was produced from the agamous form only at intervals of four, five, eight, or ten years. Walsh also remarked that Cynips species rarely fly, and breed from year to year on the same tree. Walsh planned to complete a second paper on Cynips in the autumn of 1866 (see Correspondence vol. 14, letter from B. D. Walsh, 17 July 1866).
3
In later correspondence, CD and Walsh discussed an unspecified form of oak-gall that had spread rapidly in England (Correspondence vol. 14, letter to B. D. Walsh, 20 August [1866], and letter to B. D. Walsh, 9 August [1867], Calendar no. 5603). The steady increase of ‘the oak gall’ is also mentioned in letters to The Times, 17 August 1866, p. 10, and 18 August 1866, p. 12, and in the letter from Alfred Newton, 15 March 1874, Calendar no. 9364.
4
CD refers to Walsh 1865. See letter from B. D. Walsh, 12 November 1865 and n. 8.
5
According to Emma Darwin’s diary (DAR 242), John Lubbock and George Busk came to lunch at Down on 17 December. Lubbock had succeeded to the baronetcy on the death of his father, John William Lubbock, in June 1865 (DNB).
7
In his letter to CD of 1 March 1865, Walsh had expressed doubts about Nikolai Petrovich Wagner’s description of paedogenesis in the larvae of the gall-midge, Miastor metraloas. CD suggested that such cases be regarded as forms of gemmation (see letter to B. D. Walsh, 27 March [1865]; see also letter from B. D. Walsh, 29 May 1865). In the concluding paragraph to his 1866 paper on willow-galls, Walsh cited subsequent research that confirmed Wagner’s description, adding: ‘Mr. Darwin writes me word that [Wagner’s observations] are believed by the distinguished English naturalist, Sir J. Lubbock’ (Walsh 1866, p. 288).
8
In Variation 2: 384 n., CD referred to a paper by Ernst Haeckel on a species of medusa that, while sexually mature, produced a different form by budding (Haeckel 1865b; see letter to Ernst Haeckel, 6 December [1865] and n. 9).
10
On John Scott’s research on Primula, and CD’s efforts to corroborate Scott’s findings, see the letter from John Scott, 20 January 1865 and n. 3, and the letter to Asa Gray, 19 October [1865] and n. 7. On CD’s differing results, see the letter from B. D. Walsh, 29 May 1865, n. 3. CD’s research on intra-specific and hybrid sterility is also discussed in the letter to M. E. Wichura, 3 February [1865].
11
CD had sent Walsh a copy of Scott 1864b; Walsh praised the paper in his letter of 29 May 1865, noting the ‘remarkable fact’ of intra-specific sterility in Primula as demonstrated by Scott.

Please cite as “DCP-LETT-4952,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-4952