I hope that you will permit me to return my sincere thanks to “Eques,” of Argyllshire, for his information.² I have talked to many persons, but have never found any one who knew nearly so much about the inheritance of colours in horses. “Eques” asks me to define what is meant by dun—I wish I could. It seems that almost any colour that is not bay, chesnut, black, grey, or one of the roans, is sometimes called dun. Even in mouse-duns I have seen two very distinct tints. The commonest colour which, in my limited experience, I have heard called dun, is a bay or chesnut, more or less diluted with cream or clay tint. In India, the Kattywar breed, which is more striped than any other breed, is called dun; but, as I am informed by Col. Poole, the colour is generally between brown and black.³ I now see that I should have put my question thus—Are horses, of any of the many indefinite tints commonly called duns, with a stripe along the spine, or with stripes across the legs, ever produced from parents neither of which are striped? for the first appearance or origin of the stripes is chiefly interesting for my purpose. I put the case—Are duns ever produced from parents neither of which are duns, because horses thus coloured are so frequently striped? and I thought I should more easily find out the parentage merely of the dun colour. What “Eques” says about the dirty mark on the withers, representing a single or double stripe, is exactly what I have observed. If “Eques” could find out, without much trouble, the colour of the dam and sire of his dun mare with the list and stripes, which was bred in Argyllshire, I should be very glad to hear it;⁴ but I have already caused “Eques” very much trouble, and I beg permission again to thank him.—

Charles Darwin (Down, Bromley, Kent).