198 ELEMENTARY BIOLOGY. [XIIT. 



9. The Mdneys. These organs are now exposed as two 

 elongated deep red bodies lying in the posterior 

 part of the perivisceral space close to the verte- 

 bral column ; clear away any bits of mesentery, &c. 

 which may cover them ; note — 



The duct — ureter (female) or genito-urinary canal 

 (male) — running from the outer side of the pos- 

 terior part of each kidney to the cloaca. Open 

 the cloaca and pass a bristle into the opening of 

 one of the ureters. 



h. In R. esculenta each duct is somewhat dilated 

 after leaving the kidney : it then narrows again 

 and opens on the posterior surface of the cloaca 

 by an oblique slit with sharply defined edges. 

 In R. temporaria the duct does not dilate, or 

 only very slightly ; but on its outer side lies, in 

 the male, a glandular mass (vesicula seminalis), 

 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. 



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 testes: a pair of 'yellowish bodies lying 



