436 A. J. NICHOLSON 
The thin membrane of the outer wall does not appear to 
increase appreciably in thickness, but the processes grow far 
into the cytoplasm of the epithelial cells till they reach their 
final size and form. ‘The bosses, in spite of their large size, 
arise in exactly the same manner as the rest of the processes. 
The epithelial layer now undergoes degeneration and becomes 
separated from the processes till it forms a layer lying over the 
top of these. Degeneration proceeds till only irregular masses 
of flattened nuclei can be seen attached to the inner side of the 
tunica propria (fig. 41), which forms a thin sheath round the 
whole egg. 
V. Development of the Micropyle Apparatus. 
The first indication of a special structure being produced 
for the formation of the micropyle apparatus appears when 
the egg is about a third of its full size, at the period when the 
inner wall is beginning to form as a definite layer. At this 
stage the epithelial cells immediately surrounding the point 
where the funicle of the secondary follicle joins the primary 
ovarian follicle become somewhat larger than their neighbours 
and protrude slightly inwards towards the nurse-cells (fig. 36). 
As the egg increases in size this inward protrusion becomes 
more marked, particularly in the case of the peripheral cells of 
the group. Finally, the latter are pushed completely inside 
the epithelial layer and lie between the nurse-cells and the 
epithelium (fig. 87). 
If examined from a surface view these extruded cells are seen 
to radiate from a common centre, in the form of a rosette, 
and for that reason I propose to refer to them as rosette-cells 
(fig. 38). 
At this period the cytoplasm of the nurse-cells is seen to be 
rapidly breaking down and disappearing, and also the contents 
of the nuclei are degenerating. The chromatin strands lose 
their definite structure and gradually become a shapeless 
mass and the nucleoli undergo fragmentation (fig. 37). 
The cytoplasm of the rosette-cells becomes very closely 
