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Darwin Correspondence Project

CD memorandum1   24 April 1859


Is the common mule often but faintly barred or striped transversely on the legs, like a zebra?2 Whether more on front or hind legs? Would it be possible to say that out of 100 mules, so many were barred on the legs? What is colour of body of barred mules?

(2) Is the shoulder-stripe (like that on ass) generally present in mules? If so in what coloured mules is it generally present or absent.

(3) Is the shoulder stripe ever double or treble on each shoulder? This is a very interesting point:—

(4) In any mule, which is much striped or barred, do a few faint stripes ever occur on side of face.

(5) Are stripes or bars plainer or less plain in the mule foal before the first hair is shed? This, however, could be ascertained only when number are bred.

These questions may appear trivial; but they possess more interest than is at first apparent; & I shd. be infinitely obliged for any information on the subject.—3


Down Bromley Kent

Ap. 24. 1859.—4


The memorandum evidently served as the basis for queries to a number of correspondents. For CD’s correspondence about the coloration of horses and donkeys, see particularly the letters to W. D. Fox, 13 November [1858], to Walter Elliot, 12 December [1858], and to James Egan, 8 November [1858].
CD discussed the existence of stripes on the legs of horse--donkey hybrids (mules) in Origin, p. 165, where he gave the source of his information as ‘Rollin’, a mistake for François Désiré Roulin’s work on domestic animals (Roulin 1835). CD had been unsure of his citation in Natural selection, p. 330; he evidently sought to confirm these observations before publishing Origin. However, there is no indication in Origin that he received any information on the subject in 1859. By the time he came to write Variation, he had gathered further data on mules from correspondents in India and from Philip Henry Gosse’s book Letters from Alabama (1859). See Variation 2: 41--2.
CD was interested in stripes occurring in mules as possible evidence of reversion to an ancestral equine type that was striped like a zebra (Origin, pp. 163--7).
CD added a further note in pencil at the bottom of the page: ‘Shape of stripe on shoulder’.


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.

Origin: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. By Charles Darwin. London: John Murray. 1859.

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


Questions about stripes on mules.

Letter details

Letter no.
Charles Robert Darwin
Sent from
Source of text
DAR 206 (Letters)
Physical description
AmemS 2pp

Please cite as

Darwin Correspondence Project, “Letter no. 2454,” accessed on 12 August 2022,

Also published in The Correspondence of Charles Darwin, vol. 7