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Darwin Correspondence Project

To T. H. Huxley   27 June [1863]1

Down. | Bromley. | Kent. S.E.

June 27th

My dear Huxley

You will remember my telling you that Roget says a frog has a rudiment of a 6th toe.2 I caught one yesterday (it is rarissima avis3 here) & found (above what I suppose is the great toe) a projection clearly appearing like a rudiment of an extra digit on the hind feet. I removed skin, & removed the little projection without cutting it. It consists of transparent cartilage, of nearly (I cannot draw) form Fig. I.4 This is crossed by lines which may represent articulations & then a rounded base which may represent the basal articulation. The organ has no muscles; but some are attached round the basal articulation & go to the next digit. Within the cartilage there are clusters of odd little bodies, like Fig II,5 either cavities or hard particles (for I did not wish to cut open the specimen). Now from my entire ignorance of histology & embryology of vertebrates, I am dead stopped. Could you spare time to examine this cartilage & the enclosed little bodies; & see whether it is like what a rudiment of a bone might be expected to be, or like the first embryonic trace of a bone? Or whether it is merely thickened skin? Also whether the dark lines appear like first traces of articulations? The point is in itself, I think curious, & is to me most interesting in relation to strong inheritance & regrowth of extra digits &c &c?6 The rudiment, without skin, is not much bigger than pin’s head: I have wrapped it in tin-foil & put it, & the other hind-foot, in spirits, & could send it by Post in Box.

If you are too busy, to whom could I send it? Rolleston, I daresay, would examine it for me, or Mr Flower; but I do not know either personally?7 As it is inner toe, I suppose I am right in thinking it an extra Great toe (if toe at all) & I shd. be glad of this, as I have been puzzled at the frequent doubling of the Great toe in Fowls.—8 A newt has been seen with six toes.9

Let me hear, & tell me how Mrs. Huxley10 & self are. What are you doing now??

I have never yet got hold of Edinburgh Review, in which I hear you are well abused.11 By the way I heard lately from Asa Gray that Wyman was delighted at “Man’s Place”.—12 I wonder who it is who pitches weakly, but virulently into you, in the Anthropological Review.13 How quiet Owen seems;14 I do at last begin to believe that he will ultimately fall in public estimation. What nonsense he wrote in Athenæum on Heterogeny!15 I saw in his Aye-Aye paper (I think) that he sneers at the manner in which he supposes that we should account for the structure of its limbs; and asks how we know that certain insects had increased in the Madagascan forests.16 Would it not be a good rebuff to ask him how he knows there were trees at all on the treeless plains of La Plata for his Mylodons to tear down?17 But I must stop, for if I once begin about that Devil there will be no end. I was disappointed in the part about species in Lyell.18 You & Hooker19 are the only two bold men.—

I have had a bad Spring & summer, almost constantly very unwell; but I am crawling on in my book on Variation under Domestication.20

Farewell my dear Huxley | Yours very sincerely | C. Darwin

It has only just occurred to me that I was very foolish not to look at bone in the real toes of the frog.


The year is established by the relationship between this letter and the letter from T. H. Huxley, 2 July 1863.
Rarissima avis: ‘the rarest bird’; from ‘rara avis’, a rare bird or thing (Chambers).
The diagram has not been found.
The diagram has not been found.
CD discussed polydactylism in man and other mammals in Variation 2: 12–17, suggesting that all such cases might be instances of ‘reversion to an enormously remote, lowly-organised, and multidigitate progenitor’. In Variation 2: 16, CD noted that no ‘mammal, bird, existing reptile, or amphibian’ ordinarily possessed more than five digits, ‘unless the tubercle on the hind feet of the toad and other tailless Batrachians be viewed as a digit’.
George Rolleston was Linacre Professor of anatomy and physiology at the University of Oxford; William Henry Flower was curator of the Hunterian Museum at the Royal College of Surgeons (DNB).
See Variation 2: 14
See Variation 2: 14.
Henrietta Anne Huxley.
The reference is to Charles Carter Blake’s anonymous review of T. H. Huxley 1863b in the April 1863 number of the Edinburgh Review ([Blake] 1863a); the attribution of authorship is given by the Wellesley Index.
See letter from Asa Gray, 26 May 1863. CD refers to Jeffries Wyman and to T. H. Huxley 1863b.
The first issue of the Anthropological Review, the journal of the newly formed Anthropological Society of London, appeared in May 1863. It contained an anonymous review of T. H. Huxley 1863b that, while critical of the book, was chiefly devoted to summarising its contents (Anon. 1863b). CD apparently refers to a letter that appeared in the same number under the title ‘Man and beast’, which attacked T. H. Huxley 1863b in more virulent terms (Anthropological Review 1 (1863): 153–62). The letter was signed Ανθρωπος (Anthropos), but the contents page for this volume of the journal subsequently identified its author as Blake. See also letter from T. H. Huxley, 2 July 1863. CD’s annotated copy of the issue of the Anthropological Review containing these articles is in the Darwin Library–CUL.
Richard Owen.
CD refers to Owen’s anonymous review of Carpenter 1862, published in the Athenæum, 28 March 1863, pp. 417–19. See also letters to Athenæum, 18 April [1863] and 5 May [1863], and Appendix VII.
Owen 1862c, p. 95. There is an unannotated and unbound copy of the number of the Transactions of the Zoological Society of London in which Owen 1862c appeared in the Darwin Library–CUL.
The reference is to Owen’s monograph on the extinct giant sloth, Mylodon robustus (Owen 1842).
Joseph Dalton Hooker.
CD was drafting the chapters on selection for Variation (Variation 2: 192–249; see ‘Journal’ (Correspondence vol. 11, Appendix II)).


Has caught a frog and examined its possibly rudimentary toe. Asks THH if he will dissect it.

Has heard THH is abused in Edinburgh Review and in Anthropological Review [reviews of Man’s place in nature, Edinburgh Rev. 117 (1863): 541–69 and Anthrop. Rev. 1 (1863): 107–17].

Owen on heterogeny and the aye-aye.

Has been very ill.

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: 225)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 4223,” accessed on 22 March 2019,

Also published in The Correspondence of Charles Darwin, vol. 11