438 A. J. NICHOLSON 
pyle apparatus it will be convenient to describe its origin 
here. 
When the rosette-cells are arisimg from the epithelial cells 
and are just protruding slightly towards the nurse-cells, globules 
of matter are appearing between the epithelium and the oocyte 
over the whole follicle with the exception of this one point. 
These globules are the commencement of the inner wall. 
If the protruding group of cells is examined carefully it will 
be found that there are globules opposite the central cells of 
the group (fig. 36). These are the beginning of the stopper and 
are exactly the same as those which are giving rise to the inner 
wall. The only point in the egg, therefore, where this secretion 
is not taking place is a ring corresponding with the rosette- 
cells (fig. 37). 
As the egg grows this secretion continues till a well-formed 
inner wall and a definite mass of similar matter, the stopper, 
has appeared. 
After the extrusion of the nurse-cells the inner wall narrows 
the hole through which they have passed, only leaving sufficient 
room for the passage of the funnel, and in so doing passes 
over the stopper, so that this now takes up a position imme- 
diately beneath the micropyle (fig. 39). 
A very similar process of development is deseribed by 
Gross (9) for the micropyle apparatus of Xanthogramma 
citrofasciata. In this a special group of epithelial cells 
is detached from the anterior pole of the egg, and this travels 
between the nurse-cells and finally comes to rest immediately 
under them. The follicle epithelium grows inward and separates 
the group of nurse-cells from the oocyte except in the region 
of the detached group of cells. By the time this is completed 
the nurse-cells have passed most of their cytoplasm into the 
egg-chamber, so that a mass consisting practically only of 
nurse-cell nuclei lies over the anterior end of the egg. The 
croup of cells secretes a ‘ polsterf6rmiges Gebilde ’, and the rest 
of the follicular epithelium secretes the exo- and endo-chorion. 
This ‘ polsterf6rmiges Gebilde > comes to lie immediately under 
the micropyle apparatus, and is perforated by the micropyle. 
