4-2 



Colour Iiiliiritance in Horses 



The nexrt factor, that for black, H, was discovered and correctly 

 interpreted by Hurst'. Wilson's statistics show that this factor is 

 carried by bays, browns, and blacks, though he gives no factorial 

 interpretation of his results. The figures for matings of chestnuts, 

 i.e., of li h individuals, are as follows: — 



Hurst also gives five other authorities for the statement that 

 chestnut breeds true, in various other breeds of horse.s. 



Hurst, Wilson, and I all found a good many sires producing no 

 chestnut foals, i.e., homozygous for H. These are blacks, bays, browns, 

 grays, and roans. The total foals from heterozygous sires and chestnut 

 mares is as follows : — 



Breed 

 Thoroughbred 

 Clydesdale ... 

 Trotter 



Total 



415 



413 



My next factor was B, or bay, and I considered brown as being 

 usually a heterozygous form {GHBh), although I also realised that 

 horses with the above constitution are often bays. I found what I 

 thought was a brown stallion with the formula GHBB, but this horse 

 (Prodigal) as I have since found, is recorded in the later volumes of 

 WalUices Year Book (my principal authority) as a bay. The change 

 was made after he had become famous as a sire, and is therefore 

 probably correct. I was inclined to explain the four browns recorded 

 as produced by two black parents by supposing that some GHbb horses 

 are browns. I now believe these four cases to be errors in the record, 

 this opinion being based on Wilson's and Harper's figures for matings 

 of blacks to blacks (see below). 



Wilson reached a quite different conclusion. He regards bay and 

 brown as dominant to black. His idea as to the relation between bay 

 and brown is shown by the following passage. " The relative positions 



' Pror. Hoi/iil Sof. 77 B, I'.HJIl, p. 388. 



