208 MULTIPLE ALLELOMORPHS 
colors, although the others may to some extent 
appear, especially in old mice. The third allelo- 
morph produces only black or at least the chocolate 
pigment, if present, is obscured by the darker color. 
Finally, the fourth allelomorph produces gray on 
the back and sides while the belly is pure white 
(the under hair is black). This series illustrates 
how allelomorphs of the same locus may not only 
determine the color, but also act to determine where 
a color is to develop. The allelomorphs differ there- 
fore in regard to what part of the body they affect, 
or the time in ontogeny when they act, as in the 
banded hair of the gray mouse. 
This case serves, therefore, as an excellent intro- 
duction to the cases that Emerson has described in 
corn (maize), in which the red color of the grain 
(pericarp), cob, silk, and husk furnish a wonderful 
series of character combinations that ‘can be ex- 
plained on the multiple allelomorph hypothesis. 
Emerson adopted the hypothesis of complete linkage, 
but the same arguments as used in other cases lead us 
to prefer the alternative of multiple allelomorphs. In 
some varieties of corn the grain, cob, silk, and husk 
are all red; in others all white; in others the grain is 
red or variegated, the cob, silk, and husk white; in 
others the grain is white or variegated, and the rest 
red. Many different combinations are known,-and 
so far as tested the combinations that go in through 
the two parents come out in F, according to expecta- 
tion, 7.e., they give no new gametic recombinations. 
If we assume that there is a system of allelomorphs, 
