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Darwin Correspondence Project

To Anton Dohrn   24 May 1875

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

May 24 | 1875

My dear Dr Dohrn

I am very much obliged for the present of your “Ursprung &c”.1 I have read the whole, so far as my shameful ignorance of German has permitted me. It has interested me extremely, & has astonished me not a little. Your views seem very ingenious, but I have not knowledge enough of comparative anatomy to form a judgment of any value. Should your views be even partially accepted by competent authorities, it will shew how much we have to learn about the history of every animal. May I venture to caution you not to extend too far the degradation principle.2

Nothing has surprized me so much as your belief in the changed position of the mouth of vertebrates, & of the œsophagus having aboriginally passed between the 2 main nerve-chords3   I shd be greatly pleased if your explanation of the development of our limbs from branchiæ is true, for I never dreamed of their origin being explained. I have for a long time seen the full importance of the principle of Function wechsel; though I never enunciated it as a distinct principle.4

With all good wishes | I remain my dear Sir | Yours sincerely | Charles Darwin

P.S | Please to give my thanks to Prof: Claus. for the present of his memoir on the “Arguliden”, which I hope to read immediately5


CD’s lightly annotated copy of Der Ursprung der Wirbelthiere und das Princip des Functionswechsels (The origin of vertebrates and the principle of change of function; Dohrn 1875) is in the Darwin Pamphlet Collection–CUL.
Dohrn identified homologies in the basic structure of annelids and vertebrates, from which he concluded that both had developed from a segmented ancestor. Dohrn refined his theory on the ancestry of vertebrates by proposing that similarities to vertebrates in both ascidians and Amphioxus (the lancelet; now Branchiostoma lanceolatum) were the result of degeneration from a vertebrate form (see Dohrn 1875, pp. 32–60). For more on the controversy surrounding Dohrn’s theory, see Maienschein 1994 and letter from Anton Dohrn, 7 February 1875.
See Dohrn 1875, pp. 7–9. Dohrn proposed that the original mouth (which in annelids is dorsal to the brain) was replaced in vertebrates by a new ventrally situated mouth, formed from the fusion of two gill slits (ibid., p. 9).
See Dohrn 1875, pp. 13–15. Dohrn proposed, in accordance with his principle of Functionswechsel (change of function), that posterior gills developed a secondary function of helping with movement, and that these eventually disappeared to leave only the gill arches, which would become ribs and later fins. Dohrn also devoted a section of his monograph to explaining Functionwechsel (ibid., pp. 60–76), the principle that organs tended to possess secondary functions as well as a main function; these could develop over time, leading to a shift in the main function. He saw it as a counter to St George Jackson Mivart’s objection in Genesis of species that rudimentary organs would be functionless (Mivart 1871, p. 38; Dohrn 1875, p. 61).
CD’s copy of Carl Friedrich Claus’s paper ‘Ueber die Entwickelung, Organisation und systematische Stellung der Arguliden’ (On the development, organisation, and systematic place of the Argulidae; Claus 1875) is in the Darwin Pamphlet Collection–CUL. Claus had been at Naples from 20 March until 14 April 1875 and had promised CD a copy of this paper (see letter from F. M. Balfour, [20 March – 14 April 1875]). Argulidae is the family of fish lice.


Claus, Carl Friedrich. 1875. Ueber die Entwickelung, Organisation und systematische Stellung der Arguliden. Zeitschrift für wissenschaftliche Zoologie 25: 217–84.

Dohrn, Anton. 1875. Der Ursprung der Wirbelthiere und das Princip des Functionswechsels. Genealogische Skizzen. Leipzig: Wilhelm Engelmann. [Reprinted in Theory in Biosciences 125 (2007): 181–241.]

Maienschein, Jane. 1994. ‘It’s a long way from Amphioxus’: Anton Dohrn and late nineteenth century debates about vertebrate origins. History and Philosophy of the Life Sciences 16: 465–78.


Thanks AD for his Ursprung [der Wirbelthiere (1875)], which astonished CD. AD’s views, if accepted by competent authorities, will show how much we have to learn about the history of every animal. Suggests caution on "degradation principle". Comments on other views in the work. Has long seen importance of the principle of "Functionswechsel" [transfer [change!?] of function], but never enunciated it as a distinct principle.

Letter details

Letter no.
Charles Robert Darwin
Felix Anton (Anton) Dohrn
Sent from
Source of text
Bayerische Staatsbibliothek München (Ana 525. Ba 1122)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9991,” accessed on 21 October 2021,

Also published in The Correspondence of Charles Darwin, vol. 23