A CRITICAL EXAMINATION OF RECENT STUDIES 

 ON COLOUR INHERITANCE IN HORSES. 



By a. H. STURTEVANT, 

 Columbia UnivertUy. 



About a year ago I published a paper on the iuheritance of colour 

 in the American Harness Horsed I concluded that the colour of these 

 horses is, in general, determined by five factors : C (chestnut or yellow), 

 hypostatic to the others and always present ; H (Hurst's factor or 

 black) ; B (bay), epistatic to H ; R (roan), and G (gray). There were 

 at that time two other papers on colour inheritance in horses with 

 which I was not acquainted. The first, by Dr E. H. Harper^ was 

 not written from a Mendelian standpoint, but contained confinnatory 

 evidence for my views about black and gray. The second, by Prof. 

 James Wilson', had already covered most of the points which I 

 brought out, and some others as well, although Wilson does not seem 

 to have had a very clear idea of the factors concerned, as is shown by 

 his attempt to represent the gametic constitution of his stallions by 

 only two symbols each. There is one point on which we reached 

 quite diflferent conclusions — namely, the position of brown, which I 

 shall discuss later. These three papers deal with five diflferent breeds, 

 the English Thoroughbreds and Shires and Scotch Clydesdales being 

 treated by Wilson, the French Percherons by Harper, and the American 

 Harness Horses by myself. It is my purpose in the present paper to 

 compare and combine the contents of these three contributions. 



Wilson and I agree that chestnut stands at the bottom of the scale, 

 and neither of us found any horse lacking the factor for it 



» Biol. Bull. XIX. No. 3, August 1910, p. 204. 

 « Biol. Bull. IX. No. 5, October 1905, p. 265. 

 5 Seient. Proc. Royal Dublin Soc. 12 (N. S.), No. 28, 1910. 



