130 
Transactions of the Society. 
(of). The oocytes arise from undifferentiated germinal epithelial 
cells, two of which are drawn in fig. 1, Pl. III. The nuclei of these 
cells contain masses of chromatin (CE), and in most cases no 
nucleolus is visible. As soon as one of these germinal epithelial 
cells begins to grow and acquires the nature of an oocyte, a large 
oxyphil staining nucleolus becomes apparent. A young oocyte 
growing out, away from the trabecular wall of the ovatestis, is 
shown in fig. 2, PL III. 
The nucleus contains a large spherical nucleolus (NL), with 
pseudopodia-like processes (NP). When the process HP in the 
figure was brought into focus under the microscope, the oxyphil 
staining substance NE was also in focus. This latter substance 
was apparently partly within and partly outside the nuclear mem- 
brane (N). It would seem, therefore, that it is a part of the 
nucleolus in the act of passing out of the nucleus. From the 
appearance of the nucleolus in this cell, it appears that at this 
stage it performs the same curious amoeboid movements as have 
been observed in somatic cells growing in tissue cultures. 
When the oocyte has attained a certain stage of development, 
the nucleolus becomes differentiated into two parts, as occurs in 
Patella — one part continues to stain oxyphil ; the other stains baso- 
phil. An oocyte in which the nucleolus has become altered in 
this manner is shown in fig. 3. Here again extrusion of oxyphil 
nucleolar matter (NE) is taking place. 
After the differentiation stage of the nucleolus is reached the 
two parts behave differently. A series of changes occur, the result 
of which is, that the oxyphil part of the nucleolus breaks up and is 
extruded from the nucleus, while the basophil substance also 
breaks up, but instead of being extruded is distributed evenly 
throughout the nucleus. At fig. 4 is shown the beginning 
O O o o 
of the disintegration of the nucleolus. The oxyphil staining 
part (OP) is considerably vacuolated ; it is breaking up into 
fragments (FO) which are passing out from the nucleus into the 
cytoplasm. 
The basophil part (BP) is also breaking up, and this is spread- 
ing out upon the nuclear network. In the later stage, shown in 
fig. 5, nearly the whole of the basophil part of the nucleolus has 
become scattered through the nucleus, leaving only the membrane 
(B) within which it was previously contained. 
In the same cell fragments of the oxyphil nucleolar substance 
are seen in the process of extrusion into the cytoplasm. 
At fig. 6 is shown an oocyte towards the end of oogenesis. The 
basophil part of the nucleolus (FB) is scattered upon the nuclear 
network, while the remnants of the oxyphil material (FO) are 
passing out of the nucleus. The cytoplasm, it will be seen, con- 
tains numerous yolk granules (Y). The extruded oxyphil material 
undergoes a change in staining properties, becoming amphophil. 
