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Darwin Correspondence Project

To Moritz Wagner   [April–June 1868]1

Dear and Respected Sir,—

I thank you sincerely for sending me your ‘Migrationsgesetz, &c,’ and for the very kind and most honourable notice which you have taken of my works.2 That a naturalist who has travelled into so many and such distant regions, and who has studied animals of so many classes, should, to a considerable extent, agree with me, is, I can assure you, the highest gratification of which I am capable.... Although I saw the effects of isolation in the case of islands and mountain-ranges, and knew of a few instances of rivers, yet the greater number of your facts were quite unknown to me. I now see that from the want of knowledge I did not make nearly sufficient use of the views which you advocate; and I almost wish I could believe in its importance to the same extent with you; for you well show, in a manner which never occurred to me, that it removes many difficulties and objections.3 But I must still believe that in many large areas all the individuals of the same species have been slowly modified, in the same manner, for instance, as the English race-horse has been improved, that is by the continued selection of the fleetest individuals, without any separation. But I admit that by this process two or more new species could hardly be found within the same limited area; some degree of separation, if not indispensable, would be highly advantageous; and here your facts and views will be of great value.4

With sincere thanks & respect | I remain dear Sir Charles Darwin

Down Bromley Kent


The date range is established by the publication dates of Wagner 1868a and 1868b (see nn. 2 and 3, below).
CD refers to Wagner’s paper ‘Die Darwin’sche Theorie und das Migrationsgesetz der Organismen’ (The Darwinian theory and the law of migration of organisms; Wagner 1868a). The paper appeared in the third issue of the first part of Sitzungsberichte der königlichen bayerischen Akademie der Wissenschaften zu München 1868, published after 28 March 1868. CD’s annotated copy is in the Darwin Pamphlet Collection–CUL.
In the expanded version of the paper that was completed in June 1868 (Wagner 1868b, p. viii), Wagner quoted the last part of this sentence in German translation (see Wagner 1868b, p. 50). CD’s annotated copy of Wagner 1868b is in the Darwin Pamphlet Collection–CUL.
In Origin 5th ed., p. 120, CD referred to Wagner’s essay, noting that while geographical isolation was important for preventing crosses between new varieties, it was not necessary for formation of new species.


Origin 5th ed.: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 5th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1869.


Thanks MW for his essay [Die Darwin’sche Theorie und das Migrationsgesetz der Organismen (1868)]. Is highly gratified that MW agrees with him to a considerable extent.

Almost wishes that he could believe in the importance of isolation to the same extent as MW.

Letter details

Letter no.
Charles Robert Darwin
Moritz Friedrich (Moritz) Wagner
Sent from
Source of text
LL 3: 157; DAR 148: 198

Please cite as

Darwin Correspondence Project, “Letter no. 5760,” accessed on 28 November 2021,

Also published in The Correspondence of Charles Darwin, vol. 16