STUDIES ON GERM CELLS 509 
those accompanying the upper oocyte with those of the lower 
oocyte. Surrounding the oocytes, nurse cells, and epithelial 
cell nuclei are the groups of bacteria-like bodies. 
The transition of the oocyte from Stage C (fig. 14, C; fig. 25, 
C.) to Stage D (fig. 14, D, fig. 26) is accompanied by an invasion 
of the oocyte cytoplasm by the bacteria-like rods. Some of 
these rods form almost perfect circles, resulting in what at first 
sight appear to be vacuoles. Some of the epithelial-cell nuclei 
are in very close contact with the oocyte but these were not 
observed actually within the oocyte cytoplasm. 
The principal difference between an oocyte in Stage D (fig. 26) 
and one in Stage E (fig. 14, #; fig. 27) is the sudden appearance 
of nuclear-like bodies around the nucleus, which I shall call 
secondary nuclei. The nucleus itself is about equal in size to 
that of the preceding stage (fig. 26). The chromatin, which in 
younger oocytes (figs. 24-26) has gradually migrated from the 
periphery toward the center of the nucleus where it formed an 
irregular clump, has again become scattered, being represented 
by a few smaller and widely separated masses. In the illustra- 
tion (fig. 27) three secondary nuclei are shown lying below but 
in contact with the oocyte nucleus. These likewise contain a 
delicate reticulum and from one to three chromatin masses. 
No intermediate stages between the nucleus of Stage D (fig. 26) 
and that of Stage E (fig. 27) were discovered, and it was thus 
impossible to determine with certainty the origin of these second- 
‘ary nuclei. If, however, the oocyte nucleus continued to in- 
crease in size at the same rate as indicated in Stage C (fig. 25) 
and in Stage D (fig. 26) it would be about the size of that in 
figure 27 after having given rise to the secondary nuclei by the 
method of budding or in some other way. This subject will be 
discussed more in detail later. 
During the interval between Stage E (fig. 14, E#; fig. 27) and 
Stage F (fig. 14, F, fig. 28) the oocyte enlarges until it extends 
almost across the ovariole, and the epithelial cell nuclei become 
arranged in a single layer around it, forming a follicle. At this 
time (fig. 28) the cytoplasm of the oocyte and that surrounding 
the nurse cells and epithelial-cell nuclei is crowded full of the 
