Oct., I92I] EMERSON ABERRANT CHROMOSOME BEHAVIOR 
la 
wx 
lb 
wx 
c wx y c wx 
c 
Wx 
c 
Wx 
Diagram 2 
Obviously nucleus "5" and all its descendants would lack both C and Wx 
so that the resulting aleurone would be colorless and its underlying endo- 
sperm waxy, while the aleurone and endosperm cells resulting from the 
further division of nucleus "yl " would be colored and corneous. The same 
results would follow if chromosome 3 failed to divide, going entire to one 
pole, or if after equational division one of the halves were left behind, faiHng 
to reach either pole. 
If, on the other hand, the colorless part of an aberrant seed be due to a 
somatic mutation of C to c, there is no reason to suppose that the same 
mutation would change Wx to wx. From what is known of the origin of 
factor ("point") mutations, there is little if any more warrant for the 
assumption that a single mutation will ordinarily involve simultaneously 
two loci of one chromosome than that it will affect loci of non-homologous 
chromosomes. If, therefore, in the case under consideration, the colorless 
part of an aberrant seed be due to a somatic mutation, the endosperm 
underlying it should be. corneous, c c c wx wx Wx, like that underlying the 
colored part of the aleurone, c c C wx wx Wx. 
It now remains to examine the evidence derived from crosses of colorless 
waxy individuals, c Wx, with pollen of colored corneous ones, C Wx, and to 
determine whether the colorless parts of aberrant seeds resulting from such 
crosses are underlaid with waxy or with corneous endosperm. The data 
available from the writer's cultures are presented in table i. Of the 65 
aberrant seeds there recorded, the part with colorless aleurone was underlaid 
by waxy endosperm in 55 cases, by corneous endosperm in 3 cases, and in 
the remaining 7 cases the endosperm texture could not be determined either 
because of the extremely small size of the colorless spots or because of the 
immaturity of the seeds. 
The aberrant parts of these seeds varied- in area from not much more than 
a square millimeter to about two thirds of the entire surface of the seed, 
32 of the 65 seeds having one sixth or more and only 4 having more than 
one half of the surface colorless. Eight of the 65 seeds had numerous 
colorless spots of varied sizes but mostly small, and all the others had only 
a single spot each. The line of demarcation between the colored and color- 
