The Development of the Frog 87 



5. The Vasa Efferentia 



" In both sexes at an early stage, as the Malpighian 

 bodies are forming in the Wolffian body, those nearest to 

 the genital ridges give off tubular branches from their 

 capsules into the ridges. 



" In the female frog these tubules are said to expand 

 very greatly, and to give rise to the chambers or cavities 

 in the adult ovary ; but the point is not established with 

 certainty. 



" In the male frog these tubules become the vasa effer- 

 entia; they become connected with the spermatic tubules, 

 and, as at the other ends they open into the Wolffian 

 tubules, they form passages along which the spermatozoa 

 can get from the testis to the Wolffian duct or ureter, 

 and so out." 



THE GENITAL ORGANS 



The reproductive organs begin to develop 

 in young tadpoles shortly after the opening of 

 the mouth, as longitudinal ridges or thicken- 

 ings of the peritoneal epithelium, lying near 

 the mesentery and close to the inner bor- 

 ders of the kidneys. These thickenings are 

 known as the genital ridges, and are found in 

 all tadpoles, there being as yet no sexual 

 distinctions. 



From the posterior two thirds of the genital 

 ridges the ovaries, or testes, as the case may 



