OOGENESIS AND FERTILIZATION 
IN THERMOBIA DOMESTIC A (PACKARD) 1 
By John T. Woodland 
State Teachers College, Salem, Massachusetts 
The materials and methods used in this study were the 
same as those described in an earlier paper (Woodland, 
1957). 
Oogenesis 
The primary oocytes in the vitellarium reach a length of 
about 420 microns just before yolk accumulation begins. 
They measure only about 45 microns wide. Each has a 
large central nucleus about 40 microns in diameter. It is 
a typical vesicular oocyte nucleus and usually has a visible 
nuclear membrane. A fine network is visible throughout 
the nucleus and there is a large, eccentric, irregular, granu- 
lar nucleolus which may be as long as 20 microns. Neither 
network nor nucleolus is Feulgen-positive. The finely- 
divided chromatin is so scattered throughout the large 
nucleus that it is barely visible. The cytoplasm appears very 
finely granular and contains a few inclusions. These are 10 
to 15 microns in diameter and consist of a dozen or less 
clumped globules. 
When each of the vitellaria contains four or five of these 
oocytes, yolk accumulation begins. It starts peripherally 
in all of the oocytes simultaneously and gradually proceeds 
toward the center. There appear scattered through the 
peripheral cytoplasm tiny globules which stain bright 
orange-red with Mallory’s triple stain. They greatly re- 
semble the globules of protein reserves scattered through 
the fat body surrounding the ovarioles, but are usually a 
little smaller. The negative images of small fat droplets 
also occur in the peripheral cytoplasm. The fat droplets 
and proteinaceous globules increase in size, forcing the 
diminishing cytoplasm into a network around them. By 
!Tlie research was carried out at the Harvard Biological 
Laboratories, Cambridge, Massachusetts, in partial fulfillment 
of the degree of Doctor of Philosophy. 
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