OVARY AND OVARIAN EGG OF ANOPHELES 409 
found that they all sink, so it is obvious that the buoyancy of 
the eggs is entirely due to the entrapped air. 
The micropyle apparatus consists of a very thin disk-hke 
membrane surrounded by a thick supporting ring. The central 
portion of the membrane is produced into a funnel, which 
passes through the inner wall to the interior of the egg, and the 
cavity of the funnel is the micropyle (fig. 41). 
The supporting ring is somewhat irregular on the outer side, 
but the inner edge is very regularly scalloped, and the top portion 
of the ring in each scallop is produced towards the micropyle 
so that it overhangs the rest and together with the disk forms 
a shallow pocket (figs. 40 and 41). 
Radiating out from the region of the micropyle to the point 
of junction of each ‘scallop’ is a very fine ridge. ‘These are 
thickenings of the disk corresponding to the divisions of the 
cells which give rise to the apparatus. These ridges, together 
with the ‘scallops’, mark the apparatus off into well-defined 
areas. There are normally eight of these areas, but I have 
found examples of the apparatus with from seven to ten. 
The funnel continues right through the inner wall and ends 
at the inner edge of the latter. It does not, however, com- 
municate direct with the cytoplasm of the egg, but is sealed 
up by a small globular portion of the inner wall which for 
convenience I shall term the stopper (fig. 41). 
A consideration of the structure of the micropyle apparatus 
and of the genital aperture leads me to the following theory 
as to the function of the former. 
While the egg is passing through the gynaecophoric canal 
it is no doubt considerably compressed by the muscular walls 
of this canal. This would cause the thin membranous disk 
of the micropyle apparatus to be forced outwards, and it would 
probably lie level with the top of the supporting ring. By the 
time the micropyle apparatus has reached the region where the 
spermathecal duct opens into the gynaecophoric canal, the bulk 
of the egg has left the genital aperture, and thus the pressure 
on the egg is released. The membranous disk is now able to 
resume its original position, and in so doing would probably 
