MANTLE-CAVITY 



109' 



mass, grows forwards along the back, ending in front in a 

 thickened rim, the collar. Between the mantle-fold and the 

 back of the animal, is the large mantle-cavity, which at first 

 opens anteriorly by a wide orifice. Fusion of the collar with 

 the body-wall reduces this orifice to a small round aperture 

 placed on the right side— the respiratory or pulmonary aper- 

 ture — through which air alternately enters and leaves the- 

 cavity during respiration. 



JPiQ. 29. — Helix pomatia. Dissection from the right side to show the 

 mantle-cavity and organs in relation with it. The arrow passes 

 through the pulmonary aperture into the mantle-cavity. The shell 

 and the upper part of the spiral visceral mass have been removed. 

 (a. m.. m.) 



A, auricle. B, anuE5. C, collar. J), dorsal body-wall forming the floor of 

 the mantle-cavity. E, eye. P, foot. Q-, genital aperture. H, groove leading- 

 to genital aperture. K, kidney. L, lip. P, pulmonary vein. PA, pulmonary 

 aperture. PC, pulmonary or mantle-cavity. PV", pulmonary vessels in roof 

 of mantle-cavity, PV, cut ends of pulmonary vessels. K, rectum. S, an- 

 terior tentacle. T, posterior tentacle. , U, ureter. V, ventricle. 



In close relation with the mantle-cavity are the rectum, 

 the heart, and the kidney and ureter. 



Place the snail in a dissecting dish under water, and pin 

 it firmly down through the foot, with the dorsal surface 

 upward. Open the mantle-cavity by a transverse incision 



