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Darwin Correspondence Project

To Ernst Haeckel   6 December [1865]

Down Bromley | Kent

Dec 6

My dear Sir

I am much obliged for your last letter of Nov. 11., for your letters always give me pleasure.1 I am not surprized at the delay in the publication of your book, more especially as you are appointed Professor & have been doing other work.2 I shall feel much interest in seeing this book when it appears. I most sincerely wish that you could work with better spirits; but time in the long run will do something for you.3

With your lectures & various writings, no one I think will do so much as you in spreading & perfecting sound views on species in Germany.4

Every now & then I find some good young worker taking the same side in England; I have just found this is the case with one of our best rising paleontologists Dr Duncan.5 I occasionally hear from Max Müller in Desterro & he seems to be grandly in earnest on the subject.6

You tell me that you have sent me a book with plates on Medusæ & on fossil Medusæ & on some Rhizopods, but I have not received these.7

I have received only a description of new “Craspedoter medusen” from Nice, & the Monats bericht of Berlin on the generation of the Geryoniden &c8

This latter paper interested me & surprized me much for I have often speculated whether any such case did occur in Nature & thought it possible, but never expected to see it proved.9 I suppose the paper with plates is on this same subject.10

I am sorry to say I can give but a poor account of my health: since April I have been able to do no scientific work, nor do I see any probability of any near approach to such happy days.11

With the most sincere respect & good wishes believe me my dear Sir yours very sincerely | Ch. Darwin


In his letter of 11 November 1865, Haeckel wrote that completion of his book Generelle Morphologie der Organismen (Haeckel 1866) had been delayed owing to the increased responsibilities of his new position as professor at University of Jena.
Haeckel’s wife, Anne Sethe, had died on 16 February 1864 (see letter from Ernst Haeckel, 11 November 1865 and n. 13).
See letter from Ernst Haeckel, 11 November 1865 and n. 7. On Haeckel’s support for CD’s views, see also Correspondence vol. 12, letter to Ernst Haeckel, 9 March 1864 and nn. 3 and 4.
In a paper read to the Geological Society of London on 8 March 1865, Peter Martin Duncan remarked that natural selection acted ‘with varying intensity as the great excitant’ in the dispersal of both stable and variable species (Duncan 1865, p. 361), and cited passages from Origin, p. 351, which suggest that natural selection operates ‘only so far as it profits the individual in its complex struggle for life’, so that ‘the degree of modification in different species will be no uniform quantity’. Finally, Duncan referred to CD’s discussion of the geographic dispersion of species during the glacial period in chapter 11 of Origin, claiming that it testified to ‘the identity of species over vast areas of latitude and longitude with or without gaps’ (Duncan 1865, p. 362). Duncan may have corresponded with CD on British fossil corals (see Correspondence vol. 9, letter to P. M. Duncan?, 18 July [1861]). On Duncan’s support for Darwinian theory, see A. Desmond 1982, pp. 184–5.
CD wrote ‘Max’ in error; he refers to Fritz Müller, who lived in Desterro, Brazil, and who had begun to correspond with CD on climbing plants (see, for example, letter to Fritz Müller, 10 August [1865]). In his letter of 26 October 1864 (Correspondence vol. 12), Haeckel had mentioned Müller and his recent book, Für Darwin (Müller 1864), which presented facts on the development of Crustacea favourable to CD’s theory of transmutation.
CD refers to Haeckel 1865a, Haeckel 1865c, and Haeckel 1865d. See letter from Ernst Haeckel, 11 November 1865 and nn. 9 and 11.
Haeckel 1864 and Haeckel 1865b. Haeckel 1864 described new species of ‘Craspedoter medusen’ (Hydromedusae). CD’s annotated copies are in the Darwin Library–CUL. See Correspondence vol. 12, letter from Ernst Haeckel, 9 [July 1864] and n. 15.
Haeckel 1865b, p. 88, described a form of asexual reproduction in Geryonia hastata (now Geryonia proboscidalis), a six-tentacled medusa. Haeckel claimed to have observed a new eight-tentacled species, Cunina rhododactyla (now Pegantha rubiginosa), produced by budding inside the stomach cavity of the parent. Both species could also reproduce sexually. CD referred to Haeckel 1865b in his chapter on pangenesis in Variation 2: 384 n.; however, CD described the budding as producing not a new species, but ‘a widely different form of medusa’. See also letter to J. D. Hooker, 4 May [1865] and n. 10.
Haeckel 1865a was a more general study of the history, morphology, and manner of reproduction of the genera within the family Geryonidae (now Geryoniidae).


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 28 vols to date. Cambridge: Cambridge University Press. 1985–.

Desmond, Adrian. 1982. Archetypes and ancestors: palaeontology in Victorian London, 1850–1875. London: Blond & Briggs.

Duncan, Peter Martin. 1865. A description of the echinodermata from the strata on the south-eastern coast of Arabia, and at Bagh on the Nerbudda, in the collection of the Geological Society. [Read 8 March 1865.] Quarterly Journal of the Geological Society of London 21: 349–63.

Haeckel, Ernst. 1866. Generelle Morphologie der Organismen. Allgemeine Grundzüge der organischen Formen-Wissenschaft, mechanisch begründet durch die von Charles Darwin reformirte Descendenz-Theorie. 2 vols. Berlin: Georg Reimer.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Not surprised at delay of his book [Generelle Morphologie (1866)].

P. M. Duncan taking side of evolution.

Has received paper on Geryonidae ["Über eine neue Form des Generationswechsels bei den Medusen", Monatsber. K. Akad. Wiss. Berlin (1865): 85–94]. Had often speculated on whether such a case ever occurred in nature.

Letter details

Letter no.
Charles Robert Darwin
Ernst Philipp August (Ernst) Haeckel
Sent from
Source of text
Ernst-Haeckel-Haus (Bestand A–Abt. 1: 1–52/7)
Physical description
LS 4pp

Please cite as

Darwin Correspondence Project, “Letter no. 4947,” accessed on 19 May 2022,

Also published in The Correspondence of Charles Darwin, vol. 13