To T. H. Huxley   27 June [1863]¹

My dear Huxley

You will remember my telling you that Roget says a frog has a rudiment of a 6^th 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 M^r 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 sh^d. 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 M^rs. 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.