MULTIPLE ALLELOMORPHS 211 
native views of identical loci and of complete linkage 
the method of origin of the mutant allelomorph is a 
matter of prime importance. Emerson has described 
one type (“variegated’’ corn) in which a mutation 
(to red) occurs frequently. This mutation is of 
such a sort, as Emerson points out, that, on the 
theory of complete linkage, it must involve the muta- 
tion of two factors at the same time. On the theory 
of multiple allelomorphs only one mutation is 
necessary each time the change occurs. Fortunately 
we have complete information concerning the origin 
of the types of Drosophila that fall into this category. 
One of these may now be given in detail before 
attempting to decide between the claims of the rival 
explanations. 
In 1911 a few males with white eyes arose in a 
culture of red eyed flies. From them the stock of 
white eyed flies was obtained by the usual procedure. 
In 1912, in a culture of white eyed flies having also 
miniature wings and black body color, a male ap- 
peared that had eosin eyes. He also had miniature 
wings and black body color, so that there could be no 
question of his origin from this particular stock. 
The eosin stock is descended from this male. 
In 1913, ina cross between vermilion eyed flies and 
wild flies several males appeared in F, whose eyes 
were quite different from vermilion. Analysis of 
~ the case showed that a mutation had taken place in 
the stock having vermilion eye color. The new color 
proved to be a double recessive, for vermilion and 
for a color called cherry. The new mutation had 
