108 



very iiairow space left for the iiiterHtiliuiri. Towards the lete testis 

 this space increases in width (cf. figs. 9 and 8). 



Fig. 10. Schema of the course of the testis-tubules, designated 

 in figs. 8 en 9 (X 50). 



The course of the vasa efferent ia in frogs 

 in the beginning of the second year. 



It is generalij known that in adnlt frogs the vasa etferentia, 

 which arise at the medial side of the testis, form a network, the 

 extratesticnlar network, between testis and kidney. The number 

 of these channels gi-eally varies. According to Gaupp (1904, 111, 

 p. 355) they number from 4 to 11 in Rana fusca. These differences 

 are not only individual, but occur also in tlie right and left testis 

 of one and the same animal. Channels which terminate blindly and 

 do not reach the kidney are numerous, according to Gaupp. 



Investigating a number of testes of immature frogs, I found that 

 here these particuliai-ities were also present. A conspicuous difTer- 

 ence is that the extratesticnlar network has not developed as well 

 as in adult frogs, the vasa etferentia being still situated seiially 

 close behind each other in the mesorchium. 



1 will describe six testes, derived from two frogs of 2.8 cm. and 

 one frog ot 3 cm. in length. With regard to the vasa etferentia. 



