STUDIES ON GERM CELLS 501 
oocytes. (3) Those cells of the rosette which reach the zone of 
differentiation first are stimulated to become oocytes and by 
their growth and differentiation prevent the other cells of the 
rosette from similar changes. It would be futile to argue on 
the basis of known facts in favor of any of these hypotheses. 
The arrangement of the oocytes and nurse cells within the 
ovariole resulting in a linear series of oocytes which alternate 
with groups of nurse cells takes place a short distance back of the 
zone of differentiation (fig. 1,). Paulcke (’01) has satisfactor- 
ily described and figured the formation of the epithelium around 
the oocytes and the structure of the nurse chamber, but, as stated 
above, he failed to see the intercellular rings which indicate 
the descent of the cells concerned. A group of nurse cells about 
an oocyte is shown in figure 8. This oocyte is connected with 
at least three nurse cells. One of the nurse cells (a) lies below 
the oocyte in the ovariole; since this is never true in later stages 
it is probable that such a cell would either degenerate or become 
separated from the oocyte and forced over to one side. This 
has evidently happened in the case of the oocyte illustrated in 
figure 9, since a ring is present here at the lower end (a), but 
it does not connect the oocyte with a nurse cell. The relation 
between the oocyte and its accompanying nurse cells is shown in 
figure 10. All of the nurse cells are not included, since this is a 
camera drawing of a section. It illustrates, however, the way in 
which the nurse cells form into rows converging toward the oocyte. 
The descent of the cells within the zone of differentiation would 
-be impossible to determine if it were not for the presence of the 
rings between them. These rings continue to connect the nurse 
cells with the oocyte, even in late stages in the growth of the 
latter (fig. 11) and many of them may also persist between the 
nurse cells after the nurse chamber is fully formed, as in the stage 
illustrated in figure 12. Kern (’12) also finds these rings con- 
necting the nurse cells with the oocytes of Carabus, and claims 
that nutritive material passes through them during the growth of 
the egg. 
As soon as the oocytes are differentiated, numerous granules 
of various sizes appear within their cytoplasm; in the earlier 
