482 T. H. MORGAN 
producing) this difference should be apparent on inspection 
of the somatic cells of these individuals. In my paper I have, 
in fact, given nine plates taken from young stages of the devel- 
opment of theembryo. Some of these figures, notably fig. VLII 
UC, EL, I, show six nearly equal chromosomes, while five of them, 
notably fig. VIII A, 6, D, F, G show five larger and one smaller 
chromosomes. When these drawings were made the importance 
erro i i 
1g . 
of the size relations was not appreciated, and the number of 
cases is too small to be of great value, but it is significant, I think, 
that the two kinds of chromosome groups required by the hypoth- 
esis are actually represented in these figures. 
It appears, then, probable that after the extrusion of the polar 
body of the egg of the stem-mother a change has taken place in 
those individuals that become the male-egg-producers. One 
chromosome has become smaller. 
