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Darwin Correspondence Project

To C. G. Semper   26 November [1878]1

Down, | Beckenham, Kent. | (Railway Station | Orpington. S.E.R.) [4 Bryanston Street, London]

Nov. 26th

My dear Professor Semper

When I published the 6th. Edit. of the Origin I thought a good deal on the subject to which you refer, & the opinion therein expressed was my deliberate conviction.— I went as far as I could, perhaps too far, in agreement with Wagner.2 Since that time I have seen no reason to change my mind, but then I must add that my [every] attention has been absorbed on other subjects.— There are two different classes of cases, as it appears to me, viz those in which a species becomes slowly modified in the same country (of which I cannot doubt there are innumerable instances) & those cases in which a species splits into 2 or 3 or more new species, & in these latter cases, I shd. think nearly perfect separation would greatly aid in their “specification,”—to coin a new word.—

I am very glad that you are taking up this subject, for you will be sure to throw much light on it.—3 I remember well long ago oscillating much; when I thought of the Fauna & Flora of the Galapagos Isld, I was all for isolation,— when I thought of S. America I doubted much.—4

Pray believe me | Yours very sincerely | Ch. Darwin

P.S. I hope that this letter will not be quite illegible, but I have no amanuensis at present.


The year is established by the relationship between this letter and the letter to C. G. Semper, 30 November 1878.
Moritz Wagner had argued that a population had to be isolated geographically in order to form new species (Wagner 1868a, 1868b, and 1870). CD discussed Wagner’s views in Origin 6th ed., pp. 81–2.
No previous letter from Semper on the subject of geographical isolation has been found; see, however, the letter from C. G. Semper, 6 December 1878.
On CD’s changing views on the role of geographical isolation, see Sulloway 1979.


Origin 6th ed.: The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 6th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1872.

Sulloway, Frank J. 1979. Geographic isolation in Darwin’s thinking: the vicissitudes of a crucial idea. In vol. 3 of Studies in history of biology, edited by William Coleman and Camille Limoges. Baltimore, Md., and London: Johns Hopkins University Press.


Discusses views of Moritz Wagner on modification of species. Two different cases: one in which a species is modified in the same country and cases in which a species splits. Glad CGS is taking up subject.

Letter details

Letter no.
Charles Robert Darwin
Carl Gottfried Semper
Sent from
London, Bryanston St, 4 Down letterhead
Source of text
Universitäts- und Landesbibliothek Düsseldorf (slg 60/Dok/59)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 11760,” accessed on 23 June 2021,