To T. H. Huxley   5 July [1857]1

Down Bromley Kent

July 5th

My dear Huxley

Will you be so kind as to read the two enclosed pages as you said you would & consider the little point therein referred to.—2 I have not thought it worth troubling you with how far & in which way the case concerns my work,—the point being how far there is any truth in M.M. Brullé & Barneoud.3 My plan of work is just to compare partial generalisations of various authors & see how far they corroborate each other. Especially I want your opinion how far you think I am right in bringing in Milne Edwards’ view of classification.4 I was long ago much struck with the principle referred to; but I could then see no rational explanation why affinities shd. go with the more or less early branching off from a common embryonic form. But if MM. Brullé & Barneoud are true, it seems to me we get some light on Milne Edwards’ views of classification; & this particularly interests me.5 I wish I could anyhow test M. Brullé’s doctrine: as in Vertebrata the head consists of greatly altered vertebræ, according to this rule, in an early part of the embryonic development of a Vertebrate animal, the head ought to have arrived more nearly to its perfect state, than a dorsal or cervical vertebra to its perfect state: How is this?6

I have been reading Goodsir, but have found no light on my particular point.7 The paper impresses me with a high idea of his judgment & knowledge, though, of course, I can form no independent judgment of the truth of his doctrines. But by Jove it wd. require a wonderful amount of evidence to make one believe that the head of an Elephant or Tapir had more vertebræ in it, than the head of a Horse or Ox.8

Many thanks for your last Lecture. How curious the development of Mysis!9

Yours very sincerely | Ch. Darwin

Do you know whether the embryology of a Bat has ever been worked out?

1
Dated by the relationship to the letter from T. H. Huxley, 7 July 1857.
2
CD sent Huxley a fair copy of folios 41–4 of his chapter on ‘Laws of variation: varieties and species compared’ (Natural selection, pp. 303–4). Huxley returned them to CD with his letter of 7 July 1857, and both the letter and these pages are interleaved with the folios of the original manuscript in DAR 11.1: 41–5. They were the concluding pages to the section entitled ‘Correlation of growth’ and discuss the connection between embryonic development and genealogical relationship.
3
CD refers to the memoirs by Gaspard Auguste Brullé on the development of appendages in the Articulata (Brullé 1844) and that by François Marius Barnéoud on the development of ovules, embryos, and anomalous corollas in plants (Barnéoud 1846). Brullé proposed that it was a general rule in zoology that the most complex or highly developed organs of the adult animal were the first to appear in the embryo. Barnéoud noted that abnormally developed flower parts tended to appear early and develop quickly.
4
Milne-Edwards 1844, which CD read in December 1846 (Correspondence vol. 4, Appendix IV, 119: 17a). CD’s notes on the paper are in DAR 72: 117–22. See also Correspondence vol. 4, Appendix II, pp. 392–3, and Ospovat 1981.
5
CD hoped that if Brullé’s law held it would help explain Henri Milne-Edwards’s generalisation that the greater the differences between adults, the earlier in development their embryos diverged from a common path. For a transcription of portions of CD’s notes on Milne-Edwards 1844 and on Brullé 1844, see Correspondence vol. 4, Appendix II, pp. 392–4. CD also noted in his abstract of Brullé 1844: ‘This is most remarkable & accords with M. Edwards … statement respect to whole animals in same great class, ie the more changed from each other, earlier they separate in embryonic characters.—’ (DAR 72: 123). In a note keyed to this passage, CD further commented: ‘states that in Crust, antennæ & parts of mouth appear before legs— the mouth-parts appearing before antennæ— The former have assumed their form, when the legs begin to appear.’ Later, CD added in pencil: ‘V. Rathke’s paper & M. Edwards Treatise on Crustaceæ— It wd. be important to show that in diff. families, parts did appear in different order, even if no rule cd. be established. (Ask Huxley)’ (DAR 72: 123v.).’
7
Goodsir 1857. Huxley praised this paper in one of his lectures on Crustacea (see n. 9, below).
8
In Goodsir 1857, John Goodsir challenged the view ‘that the number of segments in the vertebrate head is the same in all its forms’. Goodsir maintained that in most fish, amphibia, reptiles, and birds there were six ‘sclerotomes’, while there were seven in all mammals excluding the proboscidians, which ‘present indications of a great number’ (Goodsir 1857, p. 136).
9
Huxley discussed the development of the crustacean Mysis in his eleventh lecture in the Medical Times & Gazette (T. H. Huxley 1856–7). In Mysis, ‘the larva is inactive, and its changes are undergone within the incubating pouch of the parent.’ (T. H. Huxley 1856–7, 14: 639).

Manuscript Alterations and Comments

1.3 & in which way] interl
1.8 then] interl
1.13 consists of greatly] above del ‘is only’
1.13 early] before del ‘or middle’
2.5 an Elephant or] ‘an’ altered from ‘a’; ‘Elephant or’ interl

Please cite as “DCP-LETT-2118,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-2118