220 



THE REPRODUCTIVE SYSTEM 



[CH. 



long axes nearly parallel to the egg-string, and increase in size 

 as they approach the oviduct. In this area, the oogonia ripen 

 into mature ova, and the latter become surrounded by large masses 

 of food-yolk. The whole mass of the egg becomes next enclosed 

 in a delicate vitelline membrane formed from the egg itself. Round 



Fig. 97. Internal reproductive, organs Fig. 98. Posterior part of fig. 97, en- 



and alimentary canal of Petalura larged (x4), and with alimentary 



gigantea Leach, $, dorsal view ( x 1J). canal removed, ng^, ng s seventh 



an anus ; as accessory sac ; b bursa ; and eighth ganglia ; ov eggs ; tr 



gz gizzard; h hind -gut; mg mid-gut; tracheae. Other references as in 



mp Malpighian tubules ; ovd oviduct; fig. 97. Original. 

 ovy ovary ; 1-10 abdominal segments. 

 Original, from a dorsal dissection. 



this, a thick chitinous outer shell or chorion is deposited by the 

 follicle cells, which imprint their faint polygonal outline upon the 

 structure. The eggs are always elongated when first formed, but 

 may become rounded in some forms, when fully completed [91]. 



