40 LIVING CREATURES. 



the lower part of the shell lie the -four gill-plates with 

 which the animal breathes, or takes air from the water. 

 Above the gills is the adductor muscle. Try your 

 fork in it and see how hard it is. The oysterman 

 must cut this muscle before he can pry the valves 

 apart. He calls it the heart, but it is not a heart. 

 This latter organ, however, lies near by. It beats like 

 a human heart, only much slower from one to fifteen 

 throbs in a minute. At the front end of the gills is 

 the mouth of this headless animal. It is surrounded 

 by minute hairs, or cilia. When the oyster is open and 

 breathing, the cilia all along the gills and about the 

 mouth are in motion, pushing the water into the 

 mouth. 



The oyster has a small friend which, until recently, 

 was thought to be an enemy. It is the oyster crab, a 

 greenish little creature when alive, but becoming red 

 when cooked. It is a dainty morsel, and was so re- 

 garded by George Washington.. This little visitor, 

 about a half inch in diameter, walks in and out of 

 the oyster's house at pleasure ; for strangely enough, 

 the door seems to be always open to her. Why 

 should the oyster, usually so 

 shy, admit this intruder? 



It is found that the crab is a 

 messmate of the oyster, and 

 comes in to take her meals with 

 oyster crab. her hostess, Mrs. Oyster. The 



inflowing water which feeds the 



oyster feeds the crab. Then it is a very nice thing for 

 Crab to be inclosed in oyster castle, when hunted by 

 her fierce enemies. 



