MULTIPLE ALLELOMORPHS 217 
possible in a given locus. But if more than one 
kind of change did take place in a locus, a series of 
multiple allelomorphs would result. 
The ability of the theory of multiple allelomorphs 
(identical loci) to explain the peculiarities of so 
many cases in such widely separated fields proves the 
usefulness of the hypothesis. Although the theory 
of complete linkage also will cover the numerical 
results in these cases (and some of the simpler cases 
cited may prove to fall under this head) there is the 
very strong first-hand evidence that has just been 
given that makes the theory of multiple allelomorphs 
more probable than the former theory. It is im- 
portant to recognize that there is this strong evidence 
In favor of multiple allelomorphs, quite aside from 
special cases of complete linkage, for, as will be shown 
in the next chapter, there are some far-reaching 
consequences of the theory of multiple allelomorphs. 
A word may not be out of place here concerning 
the relation of the theory of multiple allelomorphs to 
the question of the variability of factors. The fact 
that more than one change may take place in the 
material at a given locus must not be taken to 
mean that. the material is undergoing continuous 
fluctuation, for such mutations occur rarely and 
afterward behave as do other mutations. In only 
one well established case, that of variegated corn, 
do mutations appear frequently at a given locus. 
But even in such a case the change can not properly 
be said to be fluctuating, but is of a fixed nature, 
and when it has once occurred the new factor 
