MENDEL1SM IN DOMESTIC ANIMALS 



469 



indistinctly striped. Indistinct striping and other types of marking 

 occasionally occur in horses, but the hereditary relations concerned in 

 their appearance are not well understood. 



J. Wilson has advanced a formulation which is fundamentally different 

 from the one which has been outlined above. He assumes that gray, dun, 

 bay, black, and chestnut form a series of polygamous factors as he calls 

 them, multiple allelomorphs according to our terminology, in which each 



0* 0* 0* g d G 



FIG. 187. The genotypes of gray, dun, bay, black, .and chestnut coat colors in the 

 horse according to the formulation of Wilson. The way in which animals of a particular 

 genotype behave in a subsequent generation when mated together is shown in each square. 



member of the series in the order named is dominant to succeeding 

 members and recessive to the preceding ones. In Fig. 187 we have out- 

 lined the possible combinations which could occur within such a series of 

 multiple allelomorphs, and the consequences of such combinations. In 

 addition to this pentuple series of multiple allelomorphs, Wilson assumes 

 that there is an independent dominant roan factor for the roan pattern, 

 and that there are modifying factors which affect the shade and distribu- 

 tion of pigment. Brown he considers a modified bay. Although this 

 formulation is undeniably simpler than the one which was discussed first, 

 it is highly probable that this simplicity is very misleading. The series 

 of colors evidently does not well conform to the general rule of multiple 

 allelomorphism of exhibiting a graded series with a diminishing in- 

 tensity; but, so far as the stud book records of Table LXI are concerned, 

 about the only place where this formulation fails to meet all the ob- 



