MOLLUSCA. 19 



LESSON III. 



(Repetition of ike preceding summary as usual.) 



Teacher. What organs in mollusks have we 

 considered ? 



Child. The organs of sense and of motion. 



Teacher. And what other organs are essential 

 to animal existence ? 



Child. All animals must have organs by 

 which they feed themselves. 



Teacher. Have you ever observed snails eat- 

 ing? 



Child. Yes : I have seen them devour a leaf 

 and I should think they must have teeth. 



Teacher. They have two jaws which are fur- 

 nished with small teeth, fitted for cutting vege- 

 table substances. 



Child. Have all mollusks mouths like that of 

 the snail? 



Teacher. No, the mouths of the different 

 species of mollusks, as well as their other organs, 

 are adapted to their peculiar wants and habits. 

 Some have only a simple opening to receive the 

 little animalcula brought to them by the waves, 

 and which do not require mastication.* Most of 

 those which live upon the produce of the vege- 

 table kingdom have a muzzle with jaws which 

 are either horny or armed with teeth.f The 

 * The Oyster. t The SnaiL 



C 2 



