206 MULTIPLE ALLELOMORPHS 



and yellow), and yellow form a triple system. 

 Emerson's case for pod and leaves in beans — green 

 pods, green leaves; yellow pods, yellow leaves; 

 yellow pods, green leaves — also fulfill the conditions 

 of a triple allelomorph system. Shull has reported a 

 case in Lychnis which he interprets as due to triple 

 allelomorphs for sex-determining factors. Two of 

 them give reversible mutations as have white and 

 eosin in Drosophila. 



Cases in which more than three allelomorphs have 

 been found may next be considered. The cases seem 

 to show that here also the same character is affected 

 by each of the mutant factors that form the multiple 

 system. In a few instances the characters have been 

 recognized as due to multiple allelomorphs, but in 

 most of them no sufficient interpretation has been 

 offered or else the explanation of complete linkage 

 has been advanced. 



Tanaka has reported a case in the silkworm moth 

 which seems best interpreted as one of quadruple 

 allelomorphs. The four larval patterns called striped, 

 moricaud, normal, and plain (Fig. 51), are the char- 

 acters involved. Besides showing the ordinary be- 

 havior of multiple allelomorphs when mated together 

 these characters show linkage to another pair of 

 factors (for yellow and white cocoon color). So far 

 as the data go, the strength of this linkage seems to 

 be the same in all combinations tested. 



In mice it has been shown (Cuenot, Morgan, 

 Sturtevant, and Little) that yellow, black, gray with 

 gray belly (wild type), and gray with white belly 



