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Darwin Correspondence Project

To August Weismann   22 October 1868

Down, Bromley, Kent

Oct: 22nd. 1868

Dear Sir

I am very much obliged for your kind letter, and I have waited for a week before answering it, in hopes of receiving the “Kleine Schrift” to which you allude; but I fear it is lost, which I am much surprised at, as I have seldom failed to receive any thing sent by the post.1

As I do not know the title and cannot order a copy; I should be very much obliged if you can spare another.

I am delighted that you, with whose name I am familiar, should approve of my work. I entirely agree with what you say about each species varying according to its own peculiar laws; but at the same time it must, I think, be admitted, that the variations of most species have in the lapse of ages been extremely diversified; for I do not see how it can be otherwise explained that so many forms have acquired analogous structures for the same general object, independently, of descent. I am very glad to hear that you have been arguing against Nägeli’s law of perfectibility which seems to me superfluous.2 Others hold similar views, but none of them define what this “perfection” is, which cannot be gradually attained through Natural Selection. I thought M. Wagner’s first pamphlet (for I have not yet had time to read the second) very good and interesting; but I think that he greatly overrates the necessity for emigration and isolation.3 I doubt whether he has reflected on what must occur when his forms colonize a new country, unless they vary during the very first generation; nor does he attach, I think, sufficient weight to the cases of what I have called unconscious selection by man;4 in these cases races are modified by the preservation of the best and the destruction of the worst, without any isolation.

I sympathize with you most sincerely, on the state of your eye-sight;5 it is indeed the most fearful evil which can happen to any one who like yourself is earnestly attached to the pursuit of natural knowledge.

With the most sincere respect pray believe me | dear Sir | Yours very faithfully | Charles Darwin


Weismann’s letter has not been found. CD refers to Weismann’s inaugural lecture on the justification of Darwinian theory, given at the university of Freiburg im Breisgau (Weismann 1868). CD later received the lecture; his annotated copy is in the Darwin Library–CUL (see Marginalia 1: 860–1, and letter to Friedrich Hildebrand, 14 November [1868]).
For more on Carl Wilhelm von Nägeli’s theory of perfectibility, see the letter to J. D. Hooker, 25 December [1868] and nn. 6–8. A handwritten translation of Weismann 1868, pp. 26–31, in which Weismann discusses his objections to Nägeli’s theory, is at Down House (uncatalogued).
CD refers to Moritz Wagner’s works on Migrationsgesetz (the law of migration; Wagner 1868a and 1868b). See letter to Moritz Wagner, [April–June 1868] and nn. 2 and 3.
For CD’s account of ‘unconscious selection’, see Origin, pp. 35–40.
In 1864, Weismann developed a retinal disease in one eye which seriously affected his ability to do microscopic work or even read. His vision eventually recovered and he was able to return to microscopic work in 1874 (Petrunkevitch 1963, pp. 21–2).


Fears copy of AW’s publication [Über die Berechtigung der Darwin’schen Theorie (1868)] lost in mail. Asks for another.

Glad AW approves of his work

and objects to Nägeli’s law of perfection.

Thinks Moritz Wagner overrates necessity for emigration and isolation.

Letter details

Letter no.
Charles Robert Darwin
Leopold Friedrich August (August) Weismann
Sent from
Source of text
DAR 148: 341
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 6427,” accessed on 24 April 2019,

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