14 



Farmers' Bulletin 1167. 



If we breed a common cow to a Hereford bull, we get a calf with a 

 white face. We say, therefore, that polled breeds are very prepotent 

 so far as " taking the horns off " is concerned, and that the Hereford 

 is prepotent in putting a white face on his calves. This may happen 

 either way ; that is, polled bull and horned cow, or horned bull and 

 polled cow, Hereford bull and plain-faced cow, or plain-faced bull 

 and Hereford cow. The temptation is to make great claims for the 

 prepotency of the breed as a whole on the evidence of one or two 

 points only. For see what happens when we mate a Hereford with 

 one of the polled breeds. Then we get a polled, white- faced calf. 



How Bad Blood " Breeds on." 



FIG. 6. A spotted stallion of nondescript breeding used extensively as a sire in the 

 community where he was owned. Note not only the bad color, which is almost 

 unmarketable, but also the curby hocks and generally mean appearance. 



These points are not prepotency at all, but manifestations of Men- 

 delian " dominance." The polled character is dominant over the 

 recessive horned character, and the white face over the recessive plain 

 face; but these cases do not necessarily indicate that the animal is 

 particularly prepotent in other characters of much more practical 

 importance. The same rule seems to apply in the inheritance of the 

 black color in sheep, black acting apparently as a recessive to the 

 usual white color. It can readily be eliminated by culling out the 

 black lambs. 



A great many data have been accumulated as to the characters 

 in animals which illustrate the operation of Mendel's law, but 



