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Darwin Correspondence Project

To B. D. Walsh   21 October [1864]

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

Oct 21.

My dear Sir

Ill health has prevented me from sooner thanking you for your very kind letter, & several Memoirs.1

I have been very much pleased to see how boldly & clearly you speak out on the modification of species. I thank you for giving me the pages of reference; but they were superfluous, for I found so many original & profound remarks, that I have carefully looked through all the papers.2 I hope that your discovery about the Cynips will hold good for it is a remarkable one,3 & I for one have often marvelled what could be the meaning of the case.4 I will lend your paper to my neighbour Mr Lubbock who I know is much interested in the subject.5 Incidentally I shall profit by your remarks on galls: if you have time I think a rather hopeless experiment would be worth trying; any how I should have tried it had my health permitted— it is to insert a minute grain of some organic substance together with the poison from bees, sand wasps, ichneumons, adders, & even alkaloid poisons into the tissues of fitting plants, for the chance of monstrous growths being produced.6

My health has long been poor & I have lately suffered from a long illness, which has interrupted all work, but I am now re-commencing a volume in connection with the “Origin7

With sincere thanks for your letter & kind present | Pray believe me | my dear Sir yours sincerely | Charles Darwin

P.S. If you write again I should very much like to hear what your life in your new country is. What can be the meaning or use of the great diversity of the external generative organs in your cases, in Bombus, & the Phytophagous Coleoptera? What can there be in the act of copulation necessitating such complex & diversified apparatus.—8


See letter from B. D. Walsh, 29 April – 19 May 1864 and n. 4. Walsh may also have recently sent CD a copy of Walsh 1864c, which had been published in August 1864; there is a presentation copy of this paper in the Darwin Pamphlet Collection–CUL.
See letter from B. D. Walsh, 29 April – 19 May 1864 and n. 7.
CD refers to Walsh 1864a, ‘On dimorphism in the hymenopterous genus Cynips’. See letter from B. D. Walsh, 29 April – 19 May 1864 and n. 8.
CD had been interested in the fact that in certain species of the Cynipidae, a family of gall-wasps, males were rarely if ever observed (see Correspondence vol. 7, Supplement, letter to John Lubbock, [March? 1856] and n. 3, and Descent 2: 314). Walsh had concluded that Cynips quercus aciculata was a form of C. q. spongifica occurring exclusively in the female sex (Walsh 1864a, pp. 447–8).
CD refers to John Lubbock. Lubbock had been interested in Cynips since 1856. See Correspondence vol. 7, Supplement, letter to John Lubbock, [March? 1856] and nn. 2 and 3. See also this volume, letter from John Lubbock, 3 November 1864.
It is not known whether Walsh acted on this suggestion. CD was interested in whether the nature of the poison secreted by gall-making insects was a more important determinant of the form of the gall produced than the specific character of the tree affected (see Correspondence vol. 13, letter to B. D. Walsh, 27 March [1865], letter to B. D. Walsh, 3 April [1869] (Calendar no. 5482), and Variation 2: 283–4). CD conducted experiments with poisons injected into plant tissues in 1880 (see LL 3: 346).
CD refers to Variation, the first part of a planned three-part work on species enlarging on the arguments and evidence presented in Origin (see Variation 1: 3–10). CD’s health had been particularly poor between September 1863 and mid-April 1864; he had recommenced work on Variation on 14 September 1864 (see Correspondence vol. 11, Appendix II, and this volume, letter to J. D. Hooker, 13 April [1864] and n. 5).
These questions are answered in the letter from B. D. Walsh, 7 November 1864.


Thanks for letter and memoirs.

Suggests a "rather hopeless experiment" of introducing poisons into tissues of plants on the chance that monstrous growths may be produced.

Letter details

Letter no.
Charles Robert Darwin
Benjamin Dann Walsh
Sent from
Source of text
Field Museum of Natural History, Chicago (Walsh)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 4640,” accessed on 25 September 2017,

Also published in The Correspondence of Charles Darwin, vol. 12