126 THE SNAIL. 



cavity. Its left side is notched to receive the 

 pericardium, which lies close against it. 



i. The reno-pericardial canal is a narrow ciliated 

 passage leading from the pericardial cavity to 

 the kidney. Its pericardial opening is about 

 the middle of the length of the cavity, oppo- 

 site the ventricle, and close to the inner or 

 ventral border of the septum between the 

 pericardial cavity and the kidney. 



The reno-pericardial passage is difficult to make out. To 

 see it, take a fresh snail, make a small hole into the pericardial 

 cavity, and inject into it carmine or other colouring matter sus- 

 pended in water. This will pass into the kidney along the 

 passage, which can then be followed. 



ii. The structure of the kidney. The kidney is a 

 sac lined by a glandular epithelium, and with 

 its walls thrown into a large number of 

 lamellar folds projecting into its cavity. 



Slit open the kidney longitudinally; wash it out with a 

 gentle stream of water, and note its structure. 



b. The ureter is a thin-walled duct which commences 

 at the proximal end of the kidney and runs back 

 along its right side to the distal end. It then 

 turns sharply forwards, and runs along the right 

 side of the mantle-cavity to its anterior end, 

 lying dorsal to the rectum, and just within the 

 prominent iidge-like fold that marks the junction 

 of the roof and right side of the mantle-cavity. 



In front it opens into the mantle-cavity imme- 

 diately above and to the right of the pulmonary 

 aperture. The opening is slit-like, and is con- 

 tinued as two divergent grooves with prominent 

 lips, which run down the right and left sides of 

 the pulmonary aperture, the right groove being 

 continuous below with the spout-like aperture of 

 the rectum. 



