12 Wentworth. 



held by them. It fits the writer's hypothesis perfectly. The factors 

 so far considered may be lettered as Sturtevant has done, c for 

 the chestnut ground pigment and H for the black pigment, (Hurst's 

 factor). 



Bays and Browns. 



Bay and brown are distinguished with difficulty by each of the in- 

 vestigators and by most practical men. On this account the writer has 

 made no attempt to separate them but has lumped such records together. 



Bay is a restriction factor, which will be called b, that limits 

 the development of the black pigment to the eye, mane, tail, lower 

 limbs and the extremities in general (i). It can operate only in the 

 presence of factor h, black pigment. Brown probably differs from 

 bay in having the dapple pattern combined with the restriction 

 factor B. This permits some black to appear where the dapples are 

 located and gives a darker appearance. This idea would suit the 

 microscopic as well as visual evidence since brown differs from bay 

 in the presence of black hairs. Most writers have considered brown 

 dominant to bay, a condition which would suit the above theory 

 since the dapphng pattern is apparently dominant. 



Bay to bay gives 5723 bay, 274 black and 672 chestnut. This 

 varies quite a little from the expected 9:3:4 ratio. However the 

 bays are very largely, (all but about 500), from the American Saddle 

 Horse and Standard Bred records, and bay has been the dominating 

 color among them for seventy five years. The deficiency in blacks 

 may be accounted for by their lack of popularity(2). Bay to black 

 and to chestnut give qualitatively similar results as would be expected, 

 but there is a lower percentage of bays and a higher percentage of 

 blacks in one case and chestnuts in the other than would be expected. 



The high percent of bays in the offspring of blacks to chestnuts 

 has been non-conformable to previous theories. The restriction factor 

 B does not appear somatically except in the presence of H, black 

 pigment. Theoretically three-fourths of the chestnuts ought to carry 

 this restriction factor, so that the mating of these to blacks should 

 always supply bays. From this standpoint there is a deficiency 

 rather than an excess of bays. 



(^) Black pigment is also present in the skin of the bay horse. It furnishes one 

 basis for the superficial distinction of bay and chestnut coats, claimed possible by some. 

 (-) This would prevent recording of black animals. 



