OVARY AND OVARIAN EGG OF ANOPHELES 439 
It is interesting to note the different manner in which the 
specialized group of epithelial cells are produced, and the 
degenerating nurse-cells passed out of the egg chamber in this 
insect and in A. maculipennis. 
The * polsterformiges Gebilde’ of Xanthogramma andthe 
‘stopper’ of A. maculipennis are probably homologous, 
as they are produced in a similar manner by a specialized 
group of epithelial cells, and they are also similar in appearance 
and position. There is one noticeable difference, however: in 
Xanthogramma the structure is pierced by the micro- 
pyle, while in A. maculipennis it appears to be solid, the 
micropyle terminating immediately above it. 
VI. Development of the Inner Wall. 
When the egg-follicle has reached about a third of its ultimate 
size small globules of matter are found between the follicular 
epithehum and the oocyte. These are deeply stained by 
haematoxylin and can be readily distinguished from the yolk 
granules. The globules increase in number and size and finally 
fuse, forming a coat investing the entire oocyte, with the 
exception of a ring-shaped area under the rosette-cells, 
It has already been shown that the inner wall is gelatinous 
in nature till some time after the egg has been laid, and when 
in this state rapidly swells in the presence of acids. It is 
therefore not surprising that this structure becomes very 
much distorted during fixation. In fig. 36 the inner wall is 
shown as a fibrillar structure, the fibrils stretching across the 
space between the oocyte and the follicular epithelium. This 
is @ very common appearance of the inner wall in follicles 
of about this stage of development, and I regard the fibrils as 
being produced from globules which adhere to both the oocyte 
and follicular epithelium and become stretched into threads 
when these become separated. In eggs nearing maturity the 
inner wall appears to be a thick homogeneous layer lying under 
the follicular epithelium and in it large vacuoles are frequently 
seen, but the layer does not show any signs of fibrillar structure. 
