Color iulieritance in the Horse. 1 1 



Black pigment granules rather larger, coarser and more frequently 

 clustered appear in the black horse. They are so numerous and 

 typical that they quite obscure the red ground pigment. 



Quantitative differences appear in the amount of pigment in the 

 hair, intense and dilute conditions being readily recognizable. The 

 effects of age and sun are quite noticeable also, fading usually being 

 produced, as in some cases the black hair loses its black pigment 

 almost entirely and gives the rusty black so common in Percherons 

 and general work horses. 



The inheritance of the red pigment. 



Hurst and Bunsow have shown that chestnut breeds true. The 

 figures in the table, taken from various sources (i), show that out of 

 1610 matings all but 16 are chestnut. This is a deviation from a 

 pure recessive of 1%, but since it has been shown that the average 

 stud book contains 2% of errors, this I'lo may be readily credited 

 to that. It will be noticed that the variates are 6 bays and 10 blacks. 

 Bay is the common color of a colt at birth and a rusty black is 

 nearly as frequent. Since many colts are recorded at from one to 

 three months of age and since the natal coat is not shed usually 

 until the foal is twelve weeks old errors here are not unexpected. 



The black pigment seems more complicated in nature. 406 in- 

 dividuals show it to 41 without when black is mated to black and 

 200 bear it to 108 without when black is mated to chestnut. Since 

 most of the individuals in the black by black matings are from the 

 Percheron breed in which there are a large number of homozygous 

 blacks the small ratio of chestnut segregates is not surprising. The 

 15 bays from the black by black mating are unexpected. 11 of 

 these come from Sturtevant's records. He offers the possibility of 

 error by explaining it on the ground of error in the natal coat, on the 

 difficulty in distinguishing dark browns from blacks in the parents 

 and by other means. These seem sufficient to the writer to permit 

 disregarding them since he found none in his studies on actual in- 

 dividuals, (1. c. some 100 in number). Sturtevant and the other in- 

 vestigators are disturbed by the high percent of bays from the black 

 by chestnut matings, but this is probably due to the idea of bay 



(1) The Government Gray Draft Horse Experiment at Ames, Pedigree and study 

 of actual animals by the writer, Sturtevant's, Wilson's and Anderson's papers 

 principally, with isolated cases from the agricultural press. 



