78 MEXDELISM chap, vii 



less ram, therefore, put to a flock of Fi ewes should give 

 rise to equal numbers of zygotes which are heterozygous 

 for the horned character, and of zygotes in which it is 



Dorset^ Suffolk Suffolk Dorset 

 Ram Ewe Ram Ewe 



4 x Q c? x f 



1 . 





i 1 i 



. - - -T7 



o x v 



---?*1 



(F) I I 1 i ' ' ' ; 



l >x<J 4 4 4 9 S ? ?-" 



--F 2 



4 6 ? 9 



Fig. i6. 



Scheme to illustrate the inheritance of horns in sheep. Heterozygous males shown 

 dark with a white spot, heterozygous females light with a dark spot in the centre. 



completely absent. And since the heterozygous males 

 are horned, while the heterozgyous females are hornless, 

 we should expect from this mating equal numbers of 

 horned and hornless rams, but only hornless ewes. The 

 result of the experiment confirmed this expectation. Of 

 the ram lambs g were horned and 8 were hornless, while 

 all the 1 1 ewe lambs were completely destitute of horns. 



