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Darwin Correspondence Project

To John Gould   6 October [1861]1

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

Oct. 6th.

Dear Gould

I am extremely much obliged to you for your present of the Trochilidæ, of which I have read every word (except the Synonyms) from your pleasant Introduction to the end.—2 It certainly is a grand case of local distribution; & likewise of diversified adaptation. I was particularly glad to see one sentence, which I shall some day use, on the close alliance of the Species in the large genera.—3 I see that you allude to the crossing of Birds in a state of nature; I, for one, repudiate this notion.—4 One of the points which has interested me most (which you will not approve of) is the number of “races” or doubtful species. I think I shall extract all these cases; as it will show those persons who are quite ignorant of Nat History, that the determination of Species is not a simple affair.—5

I congratulate you on the completion of your magnificent work; & fully believe that your release from this labour will merely “enable you to go on with something else not less interesting”.

With many thanks for your valuable gift, which has interested me much, pray believe me Dear Gould | Yours sincerely | Charles Darwin


Dated by the reference to the presentation copy of Gould 1861 (see n. 2, below).
Gould sent CD a presentation copy of An introduction to the Trochilidæ, or family of humming-birds (Gould 1861); an annotated copy, dated ‘4th. October 1861.’, is in the Darwin Library–CUL. CD is mentioned in the preface as one of the naturalists who had ‘paid especial attention to the Humming-Birds’ (Gould 1861, p. ii).
Gould 1861, p. 19: ‘Apart from development, I observe that in the Humming-Birds, as in some other groups to which I have paid particular attention, the species of one genus are much more numerous than those of others, and that, whenever this is the case, the genus usually comprises many closely allied species.’ This related to CD’s conclusions about variation in large and small plant genera, discussed in Origin, pp. 55–9. CD does not appear to have quoted Gould’s sentence in any subsequent work. For a discussion of the importance in CD’s work of variation in large genera, see Kohn 1985.
Gould referred to the three humming-bird species found on the island of Juan Fernandez, stating that ‘nothing like a cross or intermixture’ had ever been observed; describing the humming-birds of Jamaica, he stated: ‘Nothing like interbreeding between two species appears to occur in this island’ (Gould 1861, pp. 8, 9).
Gould held that all the humming-bird species he described had ‘really distinctive and constant characters’ and claimed: ‘I have never observed an instance of any variation which would lead me to suppose that it was the result of a union of two species’ (Gould 1861, p. 5). Inside the back cover of his copy of Gould 1861, CD wrote in pencil: ‘Mr G. *says he has [above del ’seems‘] never noticed vars; but then he admits some slight individual variation, & if he find 2 forms from 2 districts ever so slightly different, they are called species.— In the same district at same time, sure to be similar   variation hardly can occur’. An arrow points to the facing page, where CD gave a listing of page numbers under the heading: ‘All references seen here abstracted. Those not struck out, all refer to slight variations & doubtful species.—’


Kohn, David. 1985. Darwin’s principle of divergence as internal dialogue. In The Darwinian heritage, edited by David Kohn. Princeton: Princeton University Press in association with Nova Pacifica (Wellington, NZ).

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.


Thanks for JG’s book [An introduction to the Trochilidae, or family of humming-birds (1861)], which he has read carefully. Hopes someday to use the information on the close alliance of species in large genera.

CD repudiates hybridity of birds in nature.

Intends to extract the cases of "races" or doubtful species. They show that "determination of species is not a simple affair".

Letter details

Letter no.
Charles Robert Darwin
John Gould
Sent from
Source of text
Cambridge University Library (Add 4251/330)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 3278,” accessed on 18 June 2021,

Also published in The Correspondence of Charles Darwin, vol. 9