MOLLUSCA. 9 



with others, in what respect do they appear 

 deficient ? 



Child. They have no bones, the shell acting 

 as a support to their bodies, which are attached 

 to it by muscles. 



Teacher. What envelops the mollusca ? 



Child. A sac or mantle. 



Teacher. Describe the mantle. 



Child. The mantle is full of pores and glands 

 and is moistened by a slimy exudation some- 

 times it quite encloses the animal, having only 

 one opening like a purse, sometimes it has ex- 

 pansions at the sides, like fins, and sometimes it 

 spreads over the shell. 



Teacher. What are glands ? 



Child. Small lumps containing fluids, which 

 are separated from the blood. 



Teacher. Yes, in animals the glands secrete 

 fluids from the blood ; but in vegetables from 

 the sap. Have these animals any blood ? 



Child. Yes ; but it is white and cold. 



Teacher. In what respects is it similar to blood ? 



Child. It circulates through the body in 

 vessels issuing from the heart. 



Teacher. What senses are enjoyed by the 

 mollusca ? 



Child. The senses of feeling, seeing, tasting, 

 and, it is supposed smelling. 



Teacher. In what part of their frames is the 

 sense of feeling most acute ? 



Child. In the tentacula. 



Teacher. Tell me the derivation of that term ? 



