VISCEKA. 55 



large calibre and tapers gradually towards the cloaca. 

 R. temporaria has larger testes, measuring two-thirds 

 to three-fourths the length of the kidneys, nearer the 

 anterior than the posterior extremity of the latter, and 

 often more or less strongly pigmented ; the vesicula 

 seminis is large and distinct from the ureter, im- 

 mediately behind the kidney. In R. arvalis, R. grseca, 

 R. latastii, and R. agills the testes are, as a rule, 

 smaller, one-third to two-thirds the length of the 

 kidneys, and not or but feebly pigmented. In 

 R. temporaria, grseca, latastii, the veslcula seminis is 

 in contact with the kiduey, whilst in R. arvalis and 

 R. agilis it is a small sac, usually situated along the 

 ureter midway between its attachment to the kidney 

 and the cloaca. I have, however, dissected specimens 

 of Rana arvalis in which the vesicle was situated 

 very near the kidney. 



The chief differences in the male urogenital appa- 

 ratus may be expressed in the following synopsis : 



I. The spermatozoa are conveyed through the vasa 



efferentia direct to the seminal duct; the latter 

 produced forwards beyond the kidney. 



DlSCOGLOiSSIDiE. 



a. The ureter functions as seminal duct. 



A single vas efferens ; a vesicula seminis. 



Discoglossm. 



Several vasa efferentia opening into a canal along 

 the outer edge of the kidney ; no vesicula 

 seminis ..... Bombinator. 



n. The Miillerian duct functions as semiual canal 

 distinct from the ureter ; two vasa efferentia 

 close together in front of the kidney ; a 

 vesicula seminis .... Alytes. 



II. The spermatozoa are conveyed to the semiual 



duct (ureter) through the kidney, in which the 

 anterior extremity of the duct is embedded. 



