256 T. H. Morgan 
as big as the medium-sized ones, and one smallest, much smaller 
than the medium ones. Evidently some change has occurred 
which, without altering the number of the chromosomes, has given 
them different sizes. “The meaning of this change will be apparent 
later. 
A single polar body is given off from the female and from the 
male eggs. I have studied the polar body formation in this species 
with great care and have tried for a long time to obtain demon- 
strative telophase stages. [he accumulative evidence is con- 
vincing, I think, although despite the long labor that the search has 
involved I have not yet found a case in which in the telophase both 
daughter plates could be counted except for one female egg. 
In this female egg, as shown in Fig. X, f, the chromosomes 
divided equally, six going into the polar body and six remaining 
in the egg. 
In the male egg I have found no case in which both daughter 
plates can be counted, but in one case the outer plate showed six 
distinct chromosomes. Polar bodies show in the best cases at least 
six chromosomes as seen in Fig. X, C-J. 
The number of chromosomes left in the egg can be determined 
by the number found in the embryonic cells. Here a curious fact 
comes to light. In some male embryos all the cells contain five 
chromosomes of nearly equal sizes—one can often be seen to be 
larger than the rest—and the others can be sorted into two pairs 
(Fig. XI). In other male eggs there are six chromosomes—one 
of them being much smaller than the others, and generally, though 
not always, connected with one end of another chromosome (Fig. 
XII). A comparison of size-relations shows that the smallest 
chromosome here corresponds to the smallest in the polar spindle 
of the male egg. [t would seem to be absent in the other—the five- 
type—but facts to be developed later show beyond doubt that it is 
not absent, but united to one of the other chromosomes. ‘Thus 
in the cells of the male embryo the chromosomal number is six, 
the same number counted in the females. ‘The result seems at first 
incompatible with that for the other species in which the male con- 
tains two less chromosomes than the female. In reality the results 
agree; for, here the true female number will be shown to be eight, 
