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Darwin Correspondence Project

To T. H. Huxley   8 July [1856]1

Down Bromley Kent

July 8th

My dear Huxley

I will use the Boltenia case, if I use it, cautiously.2 I am very sorry to trouble you but I cannot read the word scored in your first page, (which please return) & therefore cannot understand the sentence. The case is really important to me & it strikes me as in itself a singular physiological fact I presume you do not think that much water is taken in by the mouth: my impression had been that much was so taken in for respiratory & digestive processes.— But I suspect that I am forgetting & that ova & spermatozoa are in a closed receptacle.3

The fact which you give about the Polyzoa & Mr Hincks4 is very curious:5 I fancy Nordmanns case of bisexual Flustra with channel from male to female cell tells also against extraneous fertilisation.6 Do the bisexual compound Ascidians throw any light on the point? I presume there is no such a thing as a unisexual ciliograde acalephe? Does the position of ova & spermatozoa in the unisexual pulmonogrades throw any light on the possibility of crossing?7

With very many thanks | Yours very truly | C. Darwin


Dated by the relationship to the letter to T. H. Huxley, 1 July [1856].
Probably a reference to the reproductive mechanisms of some of the jellyfish (Beroidae) which, CD recorded, ‘seem to offer the greatest difficulty’ to occasional cross-fertilisation. In Natural selection, p. 46, CD gave Huxley’s opinion that ‘it is not positively known whether or not the eggs are discharged fertilised; & that as these animals derive their food from indrawn currents of water, which bathe the ovaria, it is certainly quite possible that the spermatozoa of other individuals might come into action.’
CD refers to Thomas Hincks’s paper on Bryozoa (Hincks 1852), which included a discussion of Flustra.
CD discussed this in Natural selection, p. 46, in a passage immediately following the remarks quoted in n. 3, above. CD wrote: ‘Again Prof. Huxley informs me that he should have thought that the hermaphrodite Bryozoa or Polyzoa (certain corallines) would have offered insuperable difficulties to an occasional cross, had it not been for Mr. Hinck’s observations’.
In the manuscript of Natural selection, CD pencilled a memorandum after the passage on jellyfish spermatozoa (see n. 3, above) referring to the work of Alexander von Nordmann: ‘Nordmann & Owen on sexes separate in Flustra. L’Institut 1839, p. 95—on sexes in coralline allied to Flustra & on zoospermatic animalcules!’ (Natural selection, p. 46 n. 1). The reference is to Nordmann 1839, which was cited in Richard Owen’s discussion of Bryozoa in Owen 1855b, pp. 151–3. These pages in CD’s copy of Owen 1855b (Darwin Library–CUL) were marked by CD.
Huxley’s reply has not been found. CD discussed the pairing of hermaphrodite organisms in Natural selection, pp. 43–6, but he made no mention of acalephs or pulmonigrades, both of which are types of jellyfish.


Hincks, Thomas. 1852. On a peculiar organ which occurs on some of the marine Bryozoa and which appears to indicate a difference of sex. Report of the 22nd meeting of the British Association for the Advancement of Science held at Belfast, Transactions of the sections, pp. 75–6.

Natural selection: Charles Darwin’s Natural selection: being the second part of his big species book written from 1856 to 1858. Edited by R. C. Stauffer. Cambridge: Cambridge University Press. 1975.

Nordmann, Alexander von. 1839. Polype nouveau de la Mer-Noire (extrait abrégé). L’Institut 7: 95.


Will use Boltenia case cautiously, if at all.


Bisexualism in Flustra and Ascidia.

Letter details

Letter no.
Charles Robert Darwin
Thomas Henry Huxley
Sent from
Source of text
Imperial College of Science, Technology, and Medicine Archives (Huxley 5: 40)
Physical description
ALS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 1922,” accessed on 28 May 2024,

Also published in The Correspondence of Charles Darwin, vol. 6