MULTIPLE ALLELOMORPHS 215 
probable for the cases known than is that of complete 
linkage (in the sense defined). No one of the reasons 
is in itself conclusive, but taken together they weight 
the scales heavily on one side. 
1. When two mutants that depend on “multiple 
allelomorphs”’ are crossed they give in F, a type that 
is like one or the other of the two mutants, or an 
intermediate type. This type is scarcely ever like the 
original (or wild) type. In this respect they differ 
from other recessive mutant types which when 
crossed together give the wild type. We understand 
why in the latter cases the wild form is recovered. 
It is because each mutant type contains besides its 
mutant factor the normal (dominant) allelomorph 
of the other type. Hence the original type is re- 
constituted in the cross, as has been already stated. 
But when two mutant allelomorphs occupying the 
same locus are brought together neither of them 
brings in the normal allelomorph of the other; 
hence the wild type is not reconstituted. If the 
cases in which these allelomorphic factors arose 
independently are not cases of identical loci then the 
explanation involves the occurrence of two muta- 
tions at the same time, as explained in the case of 
cherry. , 
2. It is a characteristic of “multiple allelomorphs”’ 
that the same character is affected. Nearness of 
factors in the chromosome will not explain this fact 
unless nearness means the same factorial basis, for 
in the other mutants that we have obtained, nearness 
of factors is in no way related to the kind of character 
