14 LESSON II. 



shells clustered together on the rocks and 

 stones ? 



Child. Yes, barnacles ; are they the animals 

 which never move from the spot to which they 

 are attached ? 



Teacher. Yes, the barnacles and many other 

 mollusks live and die on the spot where their ex- 

 istence first commenced. 



Child. How are they fixed to the spot ? 



Teacher. Some of them, as the barnacles, 

 are cemented to the rocks by the same substance 

 of which their shells are formed ; others have a 

 less permanent mode of adhesion, and fasten 

 themselves by means of a viscid liquid which 

 they discharge from glands in their bodies ; some 

 produce silky filaments, one extremity of which 

 remains in connexion with themselves, while the 

 other is fixed to marine substances, and thus 

 anchored, they float secure in the ocean. The 

 bundle of filaments which the animal draws from 

 his body for this purpose is called a byssus.* 

 Do you know any other shells that are with 

 difficulty removed from the rocks ? 



Child. Yes, the limpet. 



Teacher. The manner in which this mollusk 

 fixes itself upon the rocks, is very simple, 

 though very curious. It forms within its 



* The children should see and examine for themselves these 

 contrivances. A pinna with its byssus, and barnacles on a 

 stone are easily procured. The web of the spider would give 

 them a good idea of the byssus of the pinna, being produced 

 in a very similar manner. 



