8 LESSON I. 



many mollusks have only two. The sense of 

 feeling resides in the nerves. 



Child. Oh ! then the mollusks must have 

 nerves. 



Teacher. Yes, they have nerves. Do you 

 perceive any other organs of the senses besides 

 the tentacula? 



Child. There are black specks on the horns 

 of the snail which appear like eyes. 



Teacher. These specks are the organs of 

 sight, of which mollusks have never more than 

 one pair. The sense of seeing, however, is not 

 universally possessed by this class of animals. 

 The organs of hearing and smelling have never 

 been discovered in any of them, but they are sup- 

 posed to possess the latter from the readiness 

 with which they select suitable food. This cir- 

 cumstance also proves that they possess the sense 

 of taste. You must now recapitulate all that has 

 been said concerning the mollusca. Whence is 

 the name derived ? 



Child. From mollis, the Latin for soft. 



Teacher. What kind of body have they ? 



Child. Cold, slimy, soft, and fleshy. 



Teacher. Yes ; and another quality you 

 observed when I touched the snail several 

 times. 



Child. That its body is contractile. 



Teacher. And what enabled it so quickly to 

 contract its body, and retreat into its shelter ? 



Child. Its being furnished with muscles. 



Teacher. When you compare these animals 



