MENDELIAN HEREDITY 



283 



Trihybrids. As shown in Figure 1G3, a hybrid between indi- 

 viduals bearing the allelomorphs of three different characters 



sPR 



SPr 



sp R 



Spr 



sPr spr 



Fig. 162. — The eight guinea-pig phenotypes in the F2 generation of a trihy- 

 brid. S, short hair; s, long hair or angora; P, pigmented coat; p, aIi)ino; 

 R, rough or rosetted coat; r, smooth coat. (From Walter, after drawings 

 from Castle's photographs by C. J. Fish.) 



affords possibilities for eight different com])inations in the gametes 

 of the Fi generation. The same number of combinations is 

 present in the gametes of each parent (Fig. 163), so that sixty-four 



