THE CLAM. 



Lesson I. 



The oommon soft-shelled clam of the New England ooaat (Fig. 

 1) is the one chosen for these lessons, bnt the fresh-vater clam 

 fonnd everyvhere inland can be used equally well. Large ones 

 should be obtained, and if kept alive in the Bchoolroom iu a jar of 

 sea- water for a few days before the lesson, the children's observa- 

 tions will form an e&cellent preparation for class stady. The long, 

 dark siphon, often incorrectly called the head, will be extended 

 with the two fringed openings plainly showing, bat will be at once 

 drawn in if the shell is tonched. If some very finely powdered in- 



Fig. 1. 



digo is dropped into the water, the particles will enter at the lower 

 opening and pass oat at the upper one. It will be seen that the 

 valves of the shell are connected by a dark skin that passes from 

 one to the other, and is nnbroken except by an opening near the 

 broad end of the shell, where the foot is piotmded. If a living 

 fresh-water clam is kept in a jar with two or three inohes'of sand 

 in the bottom, it will assome its natural position, with its foot ex- 

 tended and its body partly baried in the sand (Fig. 2). With 

 this form particles of indigo can be even more plainly seen passing 

 in and ont of the large siphonal openings. 



If the clams are killed by pntting them into warm water the day 

 before the lesson, the soft parts can easily be removed without 

 breaking the ligament at the hinge, while the two valves are still 



