OVARY AND OVARIAN EGG OF ANOPHELES 417 
may be seen in the nuclear sap surrounding the large nucleolus, 
or even inside the central cavity of the latter. The smallest 
examples of these appear homogeneous, but the larger fragments 
show a similar vacuolation to that of the large nucleolus, and 
are evidently produced by the fragmentation of the cortical 
layer. In one ovary examined all the oocyte nuclei contained 
numbers of small nucleoli. In some cases, however, the large 
nucleolus was indicated by a sort of phantom, as if it had given 
up practically all its substance, but the very small quantity of 
material remaining still traced its original form. In the cases 
where the original nucleolus had completely disappeared it 
is obvious that the fluid which was in its central cavity must 
have mixed with the surrounding nuclear sap, but there was 
no indication of two different fluids inside the nucleus. It 
therefore seems probable that the nucleolus is merely a hollow 
sphere, with nuclear sap both inside and surrounding it. 
The nucleus is surrounded by a thick nuclear membrane 
which is stained black by iron haematoxylin and frequently 
shows numerous local thickenings. 
When the oocyte has reached the resting stage it has a thick 
layer of cytoplasm round the nucleus. This usually stains the 
same as the cytoplasm of the nurse-cells, but sometimes it 
appears slightly more granular. 
Siconp Periop or GrowtH oF THE HEGG-FOLLICLES. 
The second period of growth extends from the time when 
the egg-follicle leaves the resting stage up to the formation of 
the mature egg. During this period several different processes 
take place and it will be convenient to consider these separately. 
These processes may be divided primarily into the nutrition 
of the egg and the formation of the egg-walls. The complexity 
of the changes of the oocyte nucleus renders it advisable 
first to treat with these thoroughly and then to deal with yolk 
formation and the nutrition of the oocyte in general. The 
subject of the formation of the egg-walls will be divided into 
the production of the inner wall, of the outer wall, and of the 
micropyle apparatus. 
