HAPPY AS A CLAM. , l6l 



Suppose the clam is quietly resting in his burrow, 

 a foot below the surface of the mud; resting in peace 

 — "as happy as a clam." At length he feels the 

 need of communication with the outside world; so, 

 up the small hole which reaches to the light he pushes 

 his two tubes or siphons, and sets his whip-like 

 pumps in action. These cilia are so arranged that 

 they lash the water down one pipe, over the surface 

 of the gills, and then, when both food and breath 

 have been abstracted from it, and it has been loaded 

 with any refuse matter that ought to be rejected, it is 

 whipped up the other tube and mingles with the 

 water above. With such a fine arrangement for liv- 

 ing at ease, no wonder the proverb speaks of the 

 happy condition of our mollusk ! 



After the tide has turned and the surface of the mud 

 is left bare, our molluscan friend stops his pumps and 

 reposes for a time. Should any footstep excite his 

 fears, he suddenly withdraws his water-pipes, shuts 

 the doors of his house with a bang, and out comes a 

 jet of water from the hole in the mud, revealing the 

 presence of life down in those dark regions. 



If we are inclined to dig, we shall know just where 

 to commence operations. But the mollusk can dig 

 too, though his motions are usually quite slow. His 

 spade is a muscular organ called the foot, which can 

 be increased or diminished in size at the will of its 

 owner. This foot can be projected through a slit in 

 the mantle and extended down into the sand or mud, 

 and then by a strong pull the shell is drawn in 

 after it. 



It is very interesting to put a clam into a jar of sea- 

 water, with sand at the bottom, and see him instinct- 

 ively try to bury his shell. Perhaps some of my little 



(ii) 



