OVARY AND OVARIAN EGG OF ANOPHELES 407 
membrane surrounding the fully-formed eggs; these lie in 
the lumen of the ovary, as the follicular tubes have contracted 
and merely cover the less-developed follicles and a small 
portion of the anterior end of the fully-formed eggs. The eggs, 
however, still he in the position in which they developed (fig. 8). 
When the eggs are being deposited they appear to break 
through the remains of the follicular epithelium and then 
pass down the oviduct to the exterior, the sperms entering the 
micropyle immediately before the eggs are laid. 
ANATOMY OF THE MaturRE Eaa. 
The mature egg is more or less cigar-shaped and is provided at 
each side with a float (fig. 9). It is, however, noticeably thicker 
at one end thanthe other, and I consider the thick end as anterior, 
as it is anterior in the ovary. The portion of the egg which 
is uppermost when floating I shall refer to as the dorsal surface. 
The egg can be divided into three main parts—the outer wall 
or chorion, the inner wall, and the yolk-mass. 
The outer wall of the egg of A. maculipennis appears 
to be identical in nature to that of other insect eggs, that is, it 
is formed of chorion, which closely resembles chitin, but differs 
from it in that it is soluble in warm KOH solution, whereas 
chitin may be boiled in concentrated caustic potash for hours 
without effect. 
The structure of the chorion of the mosquito egg shows a high 
degree of specialization. It consists essentially of a thin 
envelope surrounding the whole egg, two floats placed dorso- 
laterally, and a very beautifully-formed micropyle apparatus 
situated immediately below the extreme anterior end of the egg. 
The envelope is completely covered with processes of four 
kinds. The ventral surface is thickly covered with short 
knob-like processes (fig. 41), and some of these are slightly 
larger than the remainder and are so arranged that they divide 
the whole of the ventral surface of the egg into polygonal areas 
(fig. 9). These areas probably have some connexion with the 
form of the epithelial cells, but they appear to be too large to 
be produced by individual cells. 
