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Darwin Correspondence Project

To J. D. Hooker   8 August [1866]

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

Aug 8

My dear Hooker

It wd be a very great pleasure to me if I cd think that my letters were of the least use to you. I must have expressed myself badly for you to suppose that I look at islands being stocked by occasional transport as a well established hypothesis:1 we both give up creation & therefore have to account for the inhabitants of islands either by continental extensions or by occasional transport; now all that I maintain is that of these two alternatives, one of which must be admitted notwithstanding very many difficulties, that occasional transport is by far the most probable. 2

I go thus far further that I maintain, knowing what we do, that it wd. be inexplicable if unstocked islds were not stocked to certain extent at least, by these occasional means.—3

European birds are occasionally driven to America but far more rarely than in the reverse direction: they arrive viâ Greenland (Baird): yet a European lark has been caught in Bermuda.4 By the way you might like to hear that European birds regularly migrate, viâ the Northern Islands, to Greenland.5

About the erratics in the Azores see Origin p. 393: Hartung cd hardly be mistaken about granite blocks on a volcanic island.6

You must understand that I do not know, only suppose, that Beatson’s bird was a Wader.7

I do not think it a mystery that birds have not been modified in Madeira. Pray look at p. 422 of Origin.8 You wd not think it a mystery if you had seen the long lists which I have (somewhere) of the birds annually blown, even in flocks, to Madeira. The crossed stock would be the more vigorous.—9

Remember if you do not come here before Nottingham, if you do not come afterwards I shall think myself diabolically ill-used.10

yours affectionately | Ch. Darwin

P.S. Ought you not to measure from the Azores, not to Newfoundland, but to the more Southern & temperate States?11


On occasional transport, see the letter to J. D. Hooker, 30 July [1866], n. 7. For CD’s earlier evaluation of the hypotheses of occasional transport and continental extension, see Origin, pp. 357–65. See also CD’s arguments in favour of occasional transport in his letter to Hooker of 3 and 4 August [1866]. For CD’s earlier rejection of the hypothesis of continental extension, see, for example, Correspondence vol. 6, letter to Charles Lyell, 25 June [1856].
Spencer Fullerton Baird thought that prevailing winds accounted for the greater movement of birds from America to Europe, rather than in the reverse direction (Baird 1865–6, pp. 344–5). He also noted that Alauda arvensis, the European skylark, had been observed in Bermuda (ibid., p. 342).
European birds that had been seen in Greenland and Iceland are listed in Baird 1865–6, pp. 337–9. In his lecture, among the arguments made by CD in favour of trans-oceanic migration, Hooker mentioned American birds that were transported annually to Europe and European birds that flew to Greenland (J. D. Hooker 1866a, p. 51).
The reference is to the third edition of Origin. Georg Hartung had observed erratic boulders in the Azores (see Correspondence vol. 7, letter to Charles Lyell, 26 April [1858]). See also letter to J. D. Hooker, 5 August [1866] and n. 6.
The references are to Alexander Beatson and to what he called the wire bird (now the St Helena plover). See letter to J. D. Hooker, 5 August [1866] and n. 2.
CD’s discussion of the birds of Madeira and their lack of modification is in Origin, p. 391. The reference in this letter is to the third edition of Origin, which preserved the sentence added in the second edition on the lack of modification of the bird species of Bermuda: ‘Any tendency to modification will also have been checked by intercrossing with the unmodified immigrants from the mother-country.’ See also Peckham ed. 1959, p. 621.
CD probably refers to the lists of birds identified in Madeira in Harcourt 1855 and in the letter from E. W. V. Harcourt, 31 May 1856 (Correspondence vol. 6). CD’s annotated presentation copy of Harcourt 1855 is in DAR 196.4. In the section on oceanic islands in the second and later editions of Origin, CD argued that species of Madeiran birds gained increased vigour by occasionally crossing with continental members of the same species (see, for example, Origin 3d ed., pp. 421–2).
Hooker was to attend the meeting of the British Association for the Advancement of Science at Nottingham later in August 1866; he visited Down on 18 August (see letters from J. D. Hooker, [17 August 1866] and 18 August 1866).


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Harcourt, Edward Vernon. 1855. Notes on the ornithology of Madeira. Annals and Magazine of Natural History 2d ser. 15: 430–8.

Origin 3d ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 3d edition, with additions and corrections. By Charles Darwin. London: John Murray. 1861.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.


Admits that occasional transport is not a well-established hypothesis but believes it more probable than continental extension as an explanation for the stocking of islands.

Letter details

Letter no.
Charles Robert Darwin
Joseph Dalton Hooker
Sent from
Source of text
DAR 115: 297
Physical description
LS(A) 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 5185,” accessed on 19 April 2024,

Also published in The Correspondence of Charles Darwin, vol. 14