OVARY AND OVARIAN EGG OF ANOPHELES 493 
grows, and more small granules or ‘ young yolk ’ appear in the 
cytoplasm till this is completely filled with yolk. As the 
oocyte grows, therefore, it is natural that the young yolk 
should appear at the point where the cytoplasm is increasing 
most rapidly, that is round the periphery and more particularly 
at the proximal end of the oocyte. This actually is the case, as 
will be seen from fig. 27, in which the small granules of young 
yolk can be plainly seen around the periphery of the oocyte 
and a much larger mass is visible at its proximal end. Young 
yolk may also be observed amongst the larger and older 
granules in the central mass of the oocyte, and no doubt 
growth is by no means confined to the peripheral portion of the 
cytoplasm. 
At the same time that this coarse yolk is appearing fine yolk 
is also being laid down in the cytoplasm, the production of the 
two substances thus taking place simultaneously. 
As the oocyte is growing rapidly and large quantities of yolk 
are being laid down, the question arises as to how the nutrition 
of the oocyte takes place. The fact that most of the young 
yolk is laid down in a peripheral position might lead one to 
suppose that nutritive material passed by diffusion through 
the folheular epithelium. This probably does take place to 
some extent, but only in the earliest stages, as later the follicular 
epithelium begins to secrete the inner wall and then no doubt 
requires all the nutritive material which passes into it. 
The greater part of the nutritive material undoubtedly 
reaches the egg through the medium of the nurse-cells, and 
these in their turn must receive it from the ‘ rosette cells ’ as 
these are the only portion of the epithelium which is not 
secreting the inner wall. The inpushing of the rosette-cells 
and their close application to the nurse-cells (figs. 836 and 87) 
may assist in the transference of the nutritive material. 
That the nurse-cells are in a state of activity during this 
period is indicated by the fact that the cytoplasm stains 
irregularly, more deeply on one side than the other (fig. 27), 
an appearance which seems to be characteristic of cells which 
are secreting. 
