60 GENERAL BIOLOGY. 



passes into tlie space between the flaps of 

 the mantle, the pallia! or mantle-cavity. 



15. Inserted into the dorsal opening it enters the 



cloacal chamber and passing forward enters 

 the mantle-cavity. 



In the mantle-cavity find the following struc- 

 tures : 



16. Inside of the mantle on each side two gills or 



branchiae. 



17. Projecting ventrally near the anterior end, 



the thick foot, continued dorsally as the 

 visceral mass. 



18. Attached to the mantle anterior to the gills 



two triangular folds on each side, the 

 labial palps. 



The gills, the foot, and the labial palps all 

 hang down in the mantle-cavity. By the 

 union of the inner gills in the posterior 

 median line a partition is formed that 

 divides the posterior part of the man tie - 

 cavity into two : 



The large ventral branchial chamber. 



The smaller dorsal suprabranchial chamber. 



The posterior end of this forms the cloacal 



chamber. 

 Pass a bristle again into the cloacal chamber, 



through the suprabranchial chamber, and into 



the branchial chamber. 



