HEREDITY 



in F 2 , namely, eight. A cross between a short- 

 haired, dark, smooth guinea-pig (compare Fig. 

 22) and one which was long-haired, white, and 

 rough (Fig. 32) produced offspring in F x which 

 were short-haired, dark, and rough (compare 

 Fig. 24), these being the three dominant char- 

 acters, two derived from one parent, one from 

 the other. The F 2 offspring were of eight dis- 

 tinct types, two like the respective grandpar- 

 ents, one like the Fj individuals (parents), and 

 the other five new, shown in Fig. 33. They are 

 short white rough, short white smooth, long 

 white smooth, long dark rough, and long dark 

 smooth. The largest of the eight apparent 

 classes (phenotypes) was the one which mani- 

 fested the three dominant characters, short, 

 dark, and rough, which had been the exclusive 

 Fj type; the smallest class was the one which 

 manifested the three recessive characters, long, 

 white, and smooth. Theoretically these two 

 classes should be to each other as 27 : 1. Of 

 the twenty-seven triple-dominants, twenty-six 

 should be heterozygous. 



A comparison of this case with the one just 

 previously described shows what an increas- 



48 



