STUDIES ON GERM CELLS 52S 
of the cloud of granules mentioned above. It gradually increases 
in size, reaching its maximum dimensions about the time the egg 
reaches its full size. Then it becomes vacuolated and loses some 
of its affinity for stains. When the first cleavage division occurs, 
it passes entire into one of the two blastomeres. This blasto- 
mere does not divide as quickly as the other and a three-cell 
stage thus results, one cell containing the ‘nucleolus’ and the other 
two lacking this body. At this point the ‘nucleolus’ breaks 
down and can not be traced further. Regarding the origin of 
the ‘nucleolus’ Martin is not certain. He agrees with me that 
it is not derived from the nucleolus of the germinal vesicle, since, 
when it first appears, it is at the opposite end of the oocyte. 
Apparently it is built up by the aggregation of the deeply stain- 
ing granules among which it lies, but where these granules 
originate was not determined. 
The history of the oocyte nucleus. The ovaries of Copidosoma 
consist of a number of ovarioles, each of which contains a row 
of oocytes in various stages of growth, the oldest being situated 
near the posterior end. It is thus possiblé to find without 
much difficulty all stages in the growth period. We shall begin 
our account with an oocyte (Stage A, fig. 46) which has already 
acquired an epithelium and is accompanied by a nurse chamber. 
A close examination of such an oocyte (fig. 55) reveals a very 
large nucleus, containing an irregular, homogeneous mass of 
chromatin. A very thin layer of cytoplasm surrounds the 
nucleus. 
The nucleus does not increase much in size during the growth 
period, but the oocyte enlarges rapidly because of the accumu- 
lation of cytoplasm. During the interval between Stages A and 
B (figs. 46, 47) both the oocyte and the oocyte nucleus become 
larger and oval. The chromatin now consists of what appears 
to be a long much coiled thread (fig. 56) and one is led to believe 
that the homogeneous mass in Stage A is really the same thread 
much more compactly coiled; in other words, in the condition 
as synezesis. By the time Stage C (fig. 48) is reached the 
nucleus has again regained a spherical shape and the chromatic 
spireme has become spread out as shown in figure 57. Up to 
