OOGENESIS IN PHILOSAMIA 7 
culiarity in behavior of any of the chromosomes. In figure 
20 polar views of two groups in anaphase are shown; here 13 
approximately similar chromosomes appear in each. In figure 
21, a polar view of an egg group, 13 chromosomes may be counted. 
Figures 23 and 24 are two oblique sections through spindles in 
anaphase. The groups in each case have been slightly displaced. 
There are 13 chromosomes in each group. These examples, 
while not numerous, are sufficient to show that the second polar 
body receives a group of chromosomes similar in number to 
those remaining in the egg. The small size of the chromosomes, 
and the lack of early anaphase stages, make it impossible, as 
in the case of the first division, to draw any conclusions as to 
the equal or unequal division of the chromosomes. 
The first polar body was frequently observed in anaphase, 
during the stage figured above. After the second anaphase the 
ege chromosomes show a tendency to fusion (fig. 25) and it is 
impossible to distinguish separate chromosomes at either pole. 
d. Fertilization 
In sections through eggs in the first metaphase stage, several 
spermatozoa may be seen within the vitelline membrane, but 
only occasionally within the egg. In late anaphase, sections 
show that the spermatozoon has penetrated into the egg and 
is enveloped in a dark granular island of cytoplasm. Numerous 
eggs were found containing two or three spermatozoa. Thus 
in P. cynthia, as in many other insects, polyspermy appears 
to be normal. Shortly after entering the egg, the sperm appears 
as a long tapering rod. Later, it has the form of an oval, deep- 
staining vesicle surrounded by a clear area, and in contact with 
the female pronucleus, which lies nearer the surface of the egg. 
Subsequently the male pronucleus becomes spherical, the clear 
area disappearing. . The chromatin in both nuclei is in the form 
of irregular flocculent masses, at first darker in the male pro- 
nucleus. Later it has the same staining capacity in both, so 
that it is impossible to distinguish male and female except by 
position. 
