Case IV. Red-eyed male x F^ red-eyed female {hetero- 

 zygous ). 



The matings may be represented as follows: — 

 RX Y = male gametes 



Female 

 Gametes 



RX 



1 



IrX 



Same as the 

 F2 page 113 



Hybrids of Dorset and Suffolk Sheep 



Dorset Ram (horned) x Suffolk Ewe {hornless). 



The results are explained on the assumption of the 



following factors: — 



H = factor for horns. 



h = factor for absence of horns. 



XX = sex factors in female; X, Y in male. 



In horned ewes H & X must be duplex. 



In rams H and X are simplex. 



Following are the possible matings: 

 Case I. Fi generation. 



HX HY = male gametes 



Female 



hX 



Gametes hX 



Case II. Fi generation. 

 HX hX 



= ^{)% males horned and 

 50% females hornless. 



HY 



HY = male gametes 



Female 

 Gametes 



Giving 3 horned males, 



3 hornless females, 

 1 horned female, and 

 1 hornless male. 



(See Articles by Arkell and Davenport, Science, 1912, for 

 other results). 



114 



