XIIL] THE FROG. 207 



from the inner side of which a number of minute 

 ducts open into the genito-urinary canal. The 

 aperture of the latter in the cloaca is round 

 and has tumid edges. In the female of both 

 species the ureters are very slender. 



c. The vein (renal portal} entering the kidney at 

 its posterior outer border. 



d. The great vein (vena cava inferior) lying between 

 the kidneys and chiefly formed by their efferent 

 (renal) veins. 



Now that the cloaca is open, trace the open- 

 ing of the urinary bladder (B. 6. h) into it. 



10. The generative organs. 



a. In the male. 



a. The testcs: a pair of yellowish bodies lying 

 in front of the anterior ends of the kidneys; 

 their form. 



p. The ducts of each testicle (vasa efferent ia} 

 entering the inner border of the kidney of the 

 same side in order to communicate with the 

 genito-urinary canal (9. a}. 



y. Remove the testes : open one and press out 

 some of its contents upon a slide and mount 

 in common water: examine with -| objective. 



The spermatozoa: bodies provided with a 

 small oval head and a long vibratile tail in J?. 

 esculenta: in R. temporaria the oval head is 

 absent : their movements. 



b. In the female. 



a. The ovary : an organ varying much in size 



