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ON DUN HORSES, AND ON THE EFFECT OF CROSSING DIFFERENTLY COLOURED BREEDS.—I am very much obliged to Mr Bennett for his information about Norwegian dun ponies;¹ but I received some years ago, through the Consul-General, Mr Crowe,² the same account, which probably came from Mr Bennett. The point on which I am anxious for information is, whether a cross between two coloured horses (neither of which are dun) ever produce duns. I believe that we could thus obtain some insight into the aboriginal colour of the horse. I have as yet only a single case of the parentage of a dun—namely, a bay horse and black mare. A German writer (Hofacker) on the breeding of horses gives the case of two chesnuts producing a "goldfalb", which, I believe, is a dun; and of a chesnut and brown producing a mouse-dun (mausrapp).³ I hope "Eques" will fulfil his kind offer of giving more information on the subject.⁴ I have collected a considerable body of evidence on the remarkable tendency of the offspring of a cross between differently-coloured breeds reverting to the colour of the aboriginal parent. With pigeons, I made numerous crosses for this express purpose, and frequently got a near approach to the marks and colour of the wild rock-pigeon. Again, I crossed a Spanish cock and white silk-hen; and one of the cockerels, although at first coal-black, in the autumn assumed the splendid red plumage of the wild jungle-cock (Gallus bankiva). Two young Cocks from the black Spanish and white game-hen assumed red neck and saddle hackles, so as partly to resemble a pile game cock. Mr Brent crossed two varieties of duck, and some of the ducklings assumed the plumage of the wild duck.⁵ I could give other facts. For instance, it is asserted in works on poultry that hens raised from a cross between two breeds of fowls neither of which sit, are good sitters; and here we see a cross has brought back the proper aboriginal instinct of incubation. In my own experience, however, the crossed offspring from the Spanish cock and a Poland hen did not incubate. If anyone has any analogous facts to those above given, and would communicate them, I should be much obliged. The whole subject of the results of crossing distinct breeds is an interesting one under many points of view.— CHARLES DARWIN (Down, Bromley, Kent).

¹ Bennett 1861. Darwin cited Bennett in Variation 1: 58. See Correspondence vol. 9, p. 139.

² John Rice Crowe (1792–1877), British consul-general in Norway, 1843-1875.

³ Hofacker 1828.

⁴ 'Eques' 1861. 'Eques (Argyllshire)' responded with further details in the 8 June issue of The Field pp. 494-5.

⁵ Bernard Peirce Brent (1822-1867), shipbuilder and pigeon breeder. Darwin acknowleged Brent's assistance numerous times in Origin, Descent and Variation.