Fig. 70. Polled Durham (or short-horn) cow. Produced by a hornless sport within the short-horn 

 breed or possibly by some unrecorded cross, as with the polled red breed. 



Fig. 71. Polled Hereford heifer. A breed of English origin, ik-liornod in Aiu.rira i»y tli. .ii»i>lii-.itiuii 

 of genetic principles. Hornlessness is a dominant sport or " mutation." Compare Fig. 68. A com- 

 parison of the white spotting in Figs. 70 and 71 suggests strongly that one is only a more advanced 

 stage (quantitatively) of the other. 



