98 THE FRESHWATER MUSSEL. 



The opening of the ureter is a small hole, with 



rather prominent white lips. Almost immediately 



below it is another and less conspicuous opening, 



'the aperture of the genital duct which should be 



■■ recognised at once. 



2. The ureter. 



Bemove the gills of the right side completely, cutting along 

 their lines of attachment to the body and mantle. Inflate the 

 ureter through its external opening, and slit it up along its 

 whole length. 



The ureter is a wide thin-walled passage lying 

 above and to the outer side of the kidney. Its roof 

 is continuous with, and inseparable from, the floor of 

 the pericardium ; and its floor is continuous with the 

 roof of the kidney. On its inner side it is separated 

 from the ureter of the other side by the vena cava. 

 The two ureters communicate with each other 

 through a large slit-like opening near their anterior 

 ends. 



3. The kidney appears" as an elongated black body lying 



beneath the ureter. Posteriorly it enlarges consi- 

 derably, and is in close contact with the posterior 

 adductor muscle, which it partially embraces. 

 Lay open the kidney longitudinally with scissors. 



Its walls are thrown into thick spongy folds, 

 clothed with a black glandular epithelium. The 

 enlarged posterior end opens into the hinder end of 

 the ureter. 



4. The reno-perioardial openings are a pair of crescentic 



slits at the anterior end of the pericardial cavity, in 

 the angle between the rectum and the floor of the 

 pericardium ; they lead from the pericardial cavity 

 into the anterior ends of the right and left kidneys 

 respectively. 



Find the reno-pericardial opening on the right side, and 

 pass a seeker through it, and backwards along the kidney. 

 Slit open the passage, using the seeker as a guide. 



