DEVELOPMENT OF THE GENERATIVE ORGANS. 699 
‘12 mm. in thickness, and towards the end of the pupa state 
this disc becomes convex on its posterior, and concave on its 
anterior, surface. Even then it scarcely measures ‘9 mm. in 
diameter. 
The convex surface of the disc corresponds with the apex of 
the pyriform ovary, and the epithelial elements of the neck 
become spread out into a thin layer several cells thick, over the 
whole surface of the ovary. Towards the middle of the pupa 
stage the capsule of the ovary apparently becomes separated 
from this surface layer, so that a cavity is formed between 
the epithelium and the capsule; this I term the ovarian’ 
cavity. 
The egg-stocks, which in the early stages are finger-like pro- 
cesses extending from the epithelial layer into the body of the 
ovary (Fig. 99), become converted into flask-shaped bodies, 
each connected with the epithelial layer by a long stalk, the 
egg-stalks. By the middle of the pupa stage these stalks are 
about ‘03 mm. long (Pl. XLIX., Fig. 1), and consist of a single 
row of small cells. The cells of the egg-stocks are precisely 
similar and are about 5 w in diameter. There is no differentia- 
tion of epithelial and yelk-cells, all the cells are precisely alike. 
A little later each egg-stock and its stalk is invested in a fine 
structureless cuticular membrane, the membrana propria of 
the future egg-tube. This membrane is very generally wrinkled 
transversely over the egg-stalk, which gives it a striated appear- 
ance. This probably led Schneider [881] to regard the ege- 
stalks as striated muscle fibres. Towards the end of the pupa 
stage and in the mature nymph many of the egg-stocks exhibit 
nipple-like processes at their anterior ends; these are the rudi- 
ments of the terminal chambers. 
The Ovarian Follicles.—During the changes above described 
the septal mesoblastic tissue of the ovary becomes converted 
into a series of follicles, one enclosing each egg-stock. These 
follicles invest the egg-stocks loosely, and are separated from 
each other by spaces, blood sinuses, which contain an abund- 
ance of pseudo-yelk, and the retiform tissue from which the 
trachez of the ovary are developed. 
