212 THE BIOLOGY OF THE FROG CHAP. 



CHAPTER XI 

 THE REPRODUCTIVE ORGANS AND THE FAT BODIES 



THE reproductive system has the functions of producing 

 the sex cells and transporting them outside of the body. 

 The first function is discharged by the gonads, which are 

 known in the female as ovaries, and in the male as testes, 

 or spermaries. While the ovaries and testes are homologous 

 organs, the sexual products are carried to the outside in the 

 two sexes by very different methods. 



Organs of the Female. Each ovary of the frog is in the 

 form of a sac which is more or less lobulated. Its internal 

 cavity is divided by several partitions into chambers which 

 are filled by fluid. Externally, the ovary is covered by 

 peritoneum, which is continued on the dorsal side to form 

 a double membrane, the mesovarium, which suspends the 

 ovary from the dorsal body wall. The blood vessels and 

 nerves which supply the ovary run between the two mem- 

 branes of this supporting structure. The inner surface of 

 the ovary is lined by a single layer of flattened epithelial 

 cells, the origin of which may be traced to outgrowths from 

 the kidney in early development. The stratum medium, 

 or middle portion of the wall of the ovary, varies greatly in 

 thickness in different parts and at different times. It is 

 composed mainly of ova and follicle cells in various stages 

 of development. The eggs lie within small chambers or 

 follicles ; these consist of a layer of cells (membrana granu- 

 losa) lying next to the vitelline membrane, and outside of 

 this a very vascular network, the theca folliculi. After the 



