Ɛpsilon

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

LS

1
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.
2
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.
3
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).
4
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).
5
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.

Please cite as “DCP-LETT-9991,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-9991