THE CLAM. 29 



the fresh-water mussel, or river-clam, "the mussel's 

 brain is at the base of the understanding, that is, ex- 

 actly under the foot." 



To understand the clam animal, we must look 

 within its shell. This is opened by running a knife- 

 blade between the valves. How monkeys and apes 

 on the wild coast open them without knives, we are 

 not informed. The ancients tell a story of monkeys 

 watching the clam or oyster until it opened itself, and 

 then inserting a little stone to prevent its closing. 



The knife, when used for this purpose, must pass 

 within, and along the back, and cut two tough straps 

 that hold the valves together. Then the shell will 

 open on its hinge, and the two valves will lie back like 

 the two covers of a book. Now we have the book 

 opened, (page 31), and we must see what it contains. 



Laying aside the right cover or valve, here is the 

 soft animal lying on its bed of pearl in the left valve. 

 The first thing to notice is a slippery, filmy cloak 

 which wraps the animal as a water-proof sometimes 

 wraps a school-girl. This leathery cloak is called the 

 mantle. In its edge (e) is the sense of feeling; quite 

 likely, also, the sense of sight. 



Lay back the mantle, and there is exposed the foot 

 (/) now drawn in. At the rear end is the long, ex- 

 tended neck which includes two tubes, or siphons. 

 The siphons of the fresh-water clam are not joined, 

 and extend at different points in the shell. Through 

 the lower tube (Y) the water flows in to feed the clam. 

 Through the upper tube (<?) the same water passes out 

 after the animal has used the food it contains. 



Those who dig for clams on the sea coast, find out 



