Ɛpsilon

To C. G. Semper   2 October 1879

Down, | Beckenham, Kent.

Oct 2nd 1879

My dear Prof Semper,

I thank you for your extremely kind letter of the 19th, & for the proof sheets. I believe that I understand all, excepting one or two sentences where my imperfect knowledge of German has interfered.1 This is my sole & poor excuse for the mistake which I made in the second edit of my Coral book.2 Your account of the Pellew Islands is a fine addition to our knowledge on Coral reefs. I have very little to say on the subject: even if I had formerly read your account & seen your maps, but had known nothing of the proofs of recent elevation & of your belief that the Islands have not since subsided, I have no doubt that I should have considered them as formed during subsidence. But I should have been much troubled in my mind by the sea not being so deep as it usually is round atolls, and by the reef on one side sloping so gradually beneath the sea; for this latter fact, as far as my memory serves me, is a very unusual & almost unparalleled case. I always foresaw that a bank at the proper depth beneath the surface would give rise to a reef which could not be distinguished from an atoll formed during subsidence.3 I must still adhere to my opinion that the atolls & barrier-reefs in the middle of the Pacific & Indian oceans indicates subsidence;4 but I fully agree with you that such cases as that of the Pellew Islands if of at all frequent occurrence, would make my general conclusions of very little value. Future observers must decide between us. It will be a strange fact if there has not been subsidence of the beds, of the great oceans and if this has not affected the forms of the Coral reefs.5

In the 3 last pages of the last sheet sent, I am extremely glad to see that you are going to treat of the dispersion of animals.6 Your preliminary remarks seem to me quite excellent. There is nothing about M. Wagner as I expected to find.7 I suppose that you have seen Moseley last book, which contains some good observations on dispersion.8

I am glad that your ‘Biology’ will appear in English, for then I can read it with ease.9

Pray believe me | Yours very sincerely | Charles Darwin

LS(A)

1
Semper’s letter has not been found. The proof-sheets, which have not been found in the Darwin Archive–CUL, were for Semper’s Die natürlichen Existenzbedingungen der Thiere (The natural conditions of existence of animals; Semper 1880).
2
In Coral reefs 2d ed., p. 223, CD stated that the Pelew Islands (Palau) were in an area of subsidence; he added that there were some contraindications, and noted Semper’s doubts that the whole group had subsided, citing Semper 1863. In chapter 8 of Semper 1880, Semper argued that the islands were in fact in an area of upheaval.
3
See Coral reefs 2d ed., p. 162.
4
For CD’s argument that atolls and barrier reefs formed in areas of subsidence, see Coral reefs 2d ed., pp. 117–26.
5
Semper’s reply to this letter has not been found, but in a note to his chapter on the Pelew islands in the English translation of Semper 1880 (Semper 1881, pp. 455–6), he reproduced CD’s letter (omitting the last two paragraphs), and wrote that although subsidence may have been in some cases the sole cause of the formation of an atoll, subsidence was not sufficient to explain all the conditions and relations of coral-reefs.
6
Semper evidently included the first page of chapter 9, which was titled ‘Currents, viewed as a means of extending or hindering the distribution of species’ (the chapter title in the English translation, Semper 1881). The first page of chapter 9 was in the same signature as the last pages of chapter 8.
7
Semper discussed Moritz Wagner’s theory that the formation of new species was dependent upon geographical isolation later in chapter 9 (Semper 1880, 2: 109–14; see also Semper 1881, pp. 288–93). He had written that he intended to discuss Wagner’s theory in his letter of 6 December 1878 (Correspondence vol. 26).
8
Henry Nottidge Moseley’s Notes by a naturalist on the ‘Challenger’ (Moseley 1879), contains remarks on the distribution of plants and animals throughout.
9
Semper 1880 was translated as The natural conditions of existence as they affect animal life (Semper 1881). CD’s lightly annotated copy is in the Darwin Library–CUL; his copy of Semper 1880 is at the Linnean Society.

Manuscript Alterations and Comments

2.1 In … Darwin 4.1] in CD’s hand

Please cite as “DCP-LETT-12245,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-12245