THE EFFECTS OF CASTRATION 



137 



shown in the picture (Fig. 70) the sons had horns — 

 the daughters lacked them. When these are inbred, 

 their offspring are of four kinds, horned males, hornless 

 males, horned females, hornless females. 



It seems probable that these four classes appear in 

 the following proportions : 



Horned S Hornless S Horned $ Hornless ? 

 3 113 



The explanation that Bateson and Punnett offer for 

 this case is as follows : The germ-cells of the horned race 





Fig. 70. — 1, Suffolk (ram), hornless in both sexes; 2, Dorset (ewe), 

 horned in both sexes ; 3, Fi ram, horned ; 4, Fi ewe, hornless ; 5-8, the four 

 types of F2 ; 5 and 6 are rams, 7 and 8 are ewes. The hornless rams are 

 pure for absence of horns, and the horned ewes are pure for the presence of 

 horns. Figs. 5 and 6 represent lambs. (Bateson, after Wood.) 



(both male and female) carry the factor for horns (H) ; 

 the germ-cells of the hornless race lack the factor for 

 horns (h). The female is assumed to be homozygous 

 for the sex factor, i.e. two sex chromosomes (X) are 

 present ; while the male has only one sex chromosome 



