730 



THE AMERICAN NATURALIST [Vol. XLIX 



and are not in the least like heterozygous 4 * self s ' ' of any 

 recorded type. When crossed together they give three so- 

 matically distinct classes of young, "self," "piebald" or 

 like class "A," and black-eyed white. The numbers ob- 

 tained are 15 "self," 31 spotted (piebald or like class 

 "A") and 11 black-eyed whites. 



3. Type "A" X Piebald 



To test them further type "A," animals of this class 

 were crossed with homozygous piebald mice extracted 

 from the black-eyed white crosses. Again three general 

 classes of young were obtained as follows: 45 "self," 

 54 spotted (piebald or like type "A") and 29 black-eyed 

 whites. 



4. Type "B" X Piebald 



To compare the behavior of types "A" and "B" this 

 cross was made. Only two classes of young resulted as 

 follows: 82 class "B" and 78 piebald. No black-eyed 

 whites were obtained. 



Discussion 



The question now arising is whether the factors for 

 self, black-eyed white, and piebald are allelomorphic or 

 independent in inheritance. 



From the nature of the F 1 generation it is certain that 

 the black-eyed white animals are forming two kinds of 

 gametes in respect to their spotting factors. 



If now the conditions "self" coat, "black-eyed white" 

 and "piebald" are all related as members of a system of 

 triple allelomorphs, we can express the cross as follows : 

 S = self factor. 

 W= black-eyed white factor. 

 sp = piebald factor. 



Then 



S S = self X Wsp = black-eyed white 

 gametes S W 

 sp 



Fj Generation S W = Tvpe A, Fig. 5 

 S sp = Type B, Fig. 6 



