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Darwin Correspondence Project

To W. H. Flower   11 July [1863]1

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

July 11th

My dear Sir

I am truly obliged for all the trouble which you have taken for me & for your very interesting note.—2 I had only vaguely heard it said that Frogs had a rudiment of a sixth toe; had I known that such great men had looked to the point, I should not have dreamed of looking myself.3 The rudiment sent to you was from a full-grown frog; so that if these bones are the two Cuneiforms they must, I shd. think, be considered to be in a rudimentary condition.— This afternoon my gardener4 brought me some tadpoles, with the hind-legs alone developed, & I looked at the rudiment. At this age it certainly looks extremely like a digit, for the extremity is enlarged like that of the adjoining real toe, & the transverse articulation seems similar— I am sorry that the case is doubtful, for if these Batrachians had six toes, I certainly think it would have thrown light on the truly extraordinary strength of inheritance in Polydactylism in so many animals, & especially on the power of regrowth in amputated supernumery digits.5

With very sincere thanks | believe me | My dear Sir | Yours very faithfully | Ch. Darwin


The year is established by the relationship between this letter and the letter to T. H. Huxley, 3 July [1863].
The letter from Flower has not been found, but see n. 3, below.
Having learned that Peter Mark Roget had stated that frogs have the rudiment of a sixth toe (Roget 1834, 1: 544), and having heard other such reports, CD had dissected a specimen, asking Thomas Henry Huxley to give his opinion of the dissection (see letters to T. H. Huxley, 16 February [1863] and 27 June [1863]). Huxley declined, but offered to ask Flower to answer CD’s questions (see letter from T. H. Huxley, 2 July 1863, and letter to T. H. Huxley, 3 July [1863]). The ‘great men’ referred to in Flower’s letter have not been identified; however, see Variation 2: 12–17.
Henry Lettington.
CD referred briefly to the possible occurrence in frogs of a rudimentary sixth toe, in his extensive discussion of polydactylism and inheritance in Variation 2: 12–17 (on p. 14).


Roget, Peter Mark. 1834. Animal and vegetable physiology considered with reference to natural theology. 2 vols. London: William Pickering. [Treatise 5 of the "Bridgewater Treatises on the power wisdom and goodness of God as manifested in the creation".]

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


Discusses rudimentary sixth toe of frogs.

Letter details

Letter no.
Charles Robert Darwin
William Henry Flower
Sent from
Source of text
John Innes Foundation Historical Collections
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 4559,” accessed on 6 August 2021,

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