472 GENETICS IN RELATION TO AGRICULTURE 



shades, but on the whole our knowledge of the relations of the different 

 shades to one another is very imperfect. In Shorthorn cattle red appears 

 to breed true, at least records of white calves from red X red matings are 

 so .rare as to lead one to suspect they were due to error of registration. 

 Compared with white in this breed red represents a condition of extended 

 pigmentation, dependent upon the dominant factor, E. Here a difficulty 

 is introduced by the fact that red X white matings ordinarily produce 

 roan rather than red and white offspring. 



FIG. 188. A white polled heifer with black ears and muzzle; an Ft individual from the 

 cross Galloway X white Shorthorn. (After Lloyd-Jones and Evvard.) 



The roan color in cattle, like roan in horses, appears to depend upon a 

 definite dominant factor, R. Strictly of course roan is not a color, but a 

 pattern effect due to admixture of white hairs in a pigmented coat, and it 

 may affect black as well as red. This roan type of coloration is character- 

 istic of Shorthorn cattle. The predominance of roan animals in this breed 

 probably accounts for the fact that white mated to red usually gives roan 

 offspring, for the whites are derived almost wholly from roan matings 

 and they should therefore of necessity often bear the roan factor. There 

 are also some apparently authentic accounts of red and white animals, 

 the progeny of matings of red X white, such as the case of the noted white 

 Shorthorn bull, Whitehall Sultan, which sired fifteen red calves out of 

 various red cows. Were it not for this, J. Wilson's assumption that roan 



