MULTIPLE ALLELOMORPHS 213 
might be interpreted to mean that a mutation in eye 
color had appeared in the white-eyed stock in a 
factor located near the factor for white (‘‘completely 
linked” with it) and that the effect of this new factor, 
combined with that of the factor for white, which 
was already there, gave the color that we call eosin. 
EKosin from this point of view would be due to two 
consecutive mutations of completely linked, neigh- 
boring loci. This interpretation of two consecutive 
mutations can not be made in the case of cherry, 
however, for cherry arose from red by one step, just 
as did white; yet cherry, like eosin, when mated to 
white, does not give rise to offspring that are red. 
It would follow on the complete linkage view that 
cherry and white differ from red by the same factor, 
but since they are not alike, that one of them must differ 
from red by still another factor. Since each arose 
from red immediately, it would follow that one of 
them must have arisen by a simultaneous mutation 
in two factors completely linked and affecting the 
same character. All these assumptions must be 
made on the theory of complete linkage, but are 
avoided on the alternative theory of multiple 
allelomorphs. 
Exactly the same argument applies to many of the 
other multiple allelomorph systems of Drosophila. 
The recessive mutants pink and peach-colored eyes 
each arose independently from red eyed flies, yet 
when crossed do not give red, but a color intermedi- 
ate between pink and peach. Secondly, sooty body 
color arose in wild stock, although it was found only 
