284 Our Food Mollusks 



tunity presents itself the larger ones may be seized by 

 herring gulls, carried into the air, and dropped on rocks, 

 in order to break the shells. 



As soon as the water conies, all the uninjured ones be- 

 come active and attempt to burrow into the bottom. 

 This is accomplished by the fleshy foot, which is thrust 

 out from between the shell' valves near their anterior 

 ends. Because the foot is relatively very large and ex- 

 tensible in smaller individuals, those between one-eighth 

 and half an inch long cover themselves in a very few 

 minutes. With a foot relatively smaller, clams from 

 one to two inches long require from half to three-quar- 

 ters of an hour to effect a lodgment, but they reach the 

 usual depth of several inches only after long-continued 

 effort. Very large clams are able to project the foot so 

 short a distance that they are often not able even to 

 touch the ground with it. and after a brief effort to do so, 

 close the shell and lie helpless until destroyed by crabs 

 and fishes, or by birds and mammals, that pick up a liv- 

 ing on the shore at low tide. 



When the human factor is left out of the account, the 

 life of the adult clam appears to be as monotonous and 

 uneventful — " happy," most commenters have it — as pos- 

 sible. After reaching maturity, the creature, if undis- 

 turbed, never leaves its burrow, being quite unable to 

 do so. Its early life, however, like that of the oyster, 

 is so full of adventure that not one in millions attains the 

 safety of the bottom. 



Like all other organisms, Mya requires for its ex- 

 istence many conditions of a precise and definite sort. By 

 long experience and observation the oyster culturist has 

 learned that the oyster will grow and reproduce itself 

 only in water of a certain density and temperature, and 



