Inheritance Studies of Dairy and Beef Breeds. 135 



the other dun colored breeds by a hereditary unit which dilutes 

 the dun color. This hereditary unit must be recessive as the cross 

 was made as a backcross of the first hybrid male Ab " deen " Angus 



J Guernsey 



onto a Guernsey cow. Furthermore, this factor cannot follow 

 sex (be sex-linked) for the way the cross was made eliminates 

 this possibility, as the Guernsey mother would have to transmit 

 all of her recessive factors to her male offspring. Consequently, 

 this factor cannot be considered in the class with that for the 

 brown of the Ayrshire coat which Went worth says is depend- 

 ent for its shade on a recessive sex-linked dilution factor. The 

 almost identical appearance of the dark dun second generation 

 heifer and her Jersey parent indicate that in the Jerseys 

 any such dilution factor as that in the Guernsey is not normally 

 present. 



';^;.~- ;:m,..;.> . . , : _ . 



Creusa's Lady. 53234. 



This Guernsey cow shows the typical white marking of the breed. 

 The presence of the star is quite characteristic. It is this marking which 

 we have studied in our crosses for the inheritance of white on the head. 



