Color inheritance in the Horse. I3 



The dims. 



Duns are little known. Their numbers are few and they may 

 be grouped into at least three kinds. The ordinary buckskin with 

 black extremities is probably a dilute bay, the yellowish dun a dilute 

 chestnut and the cream colored with light mane and tail, a dilute 

 sorrel with the yellow extremities, factor m. 



Since the records do not separate them they will not be dealt 

 with further. Factor i, the dilution factor is probably epistatic to 

 all but gray and roan. 



The grays. 



Gray is recognized as a separate factor by all writers. There 

 seems some question as to whether it can operate in the absence of 

 H, black pigment, but Sturtevant presents evidence to show that 

 it does. It is dominant to all factors previously named, dappliirg d 

 and restriction b excepted, and varies from a deep iron gray in young 

 stock to the white or flea-bitten gray of the older animal. 



It is a simple factor since animals heterozygous for it produce 

 50% grays and 50% other colors. Dr. L. J. Cole of the University 

 of Wisconsin has told the writer in private communication that one 

 of his students has totalled the offspring of grays in the Clydesdale 

 studbook and has obtained exactly 50% of each of grays and other 

 colors. The Clydesdale breeders have objected to grays and have 

 always bred their gray mares to other stock in order to reduce the 

 chances of its appearance. Gray stallions since 1831 have nearly all 

 been castrated. This has resulted in all the grays being heterozygous. 



Sturtevant shows 400 gray to 428 not gray for the heterozygous 

 condition in one sex while he exhibits 45 gray to 15 not gray where 

 both parents are heterozygous. 



Gray is characterized by an intermingling of pigmented with 

 non-pigmented hairs, usually associated with dappling. It seems 

 possible that gray may be a combination of dappling and the roan 

 factor although the above evidence indicates that it is a unit in action. 



The roan pattern. 



Roan seems dominant to all the other colors and is apparently 

 a pattern entirely independent of the kind of pigment. Two kinds 

 of roans exist visually, strawberry or red roan, and blue roan. These 

 probably correspond to bays and blacks plus the roan pattern. It 



