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 'g 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 (PI. XLIX., Fig. i), and consist of a single 

 row of small cells. The cells of the egg-stocks are precisely 

 similar and are about 5 ^ 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 tine 

 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 [331] to regard the egg- 

 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 

 tracheae of the ovary are developed. 



