xiii.] 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 portat] entering the kidney at 

 its posterior outer border. 



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

 the kidneys arid 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 testes: a pair of yellowish bodies lying 

 in front of the ariterior ends of the kidneys; 

 their form. 



(3. The ducts of each testicle (vasa efferentid] 

 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 7?. 

 esculenta: in R. temporaria the oval head is 

 absent : their movements. 



b. In the female. 



a. The ovary : an organ varying much in size 



