OSTREA. b7 



as to throw it four or five inches at a time. In the 

 water, an equal dexterity is evinced by the animal, 

 in raising himself to the surface, directing his 

 course ad libitum, and suddenly, by the shutting 

 of his valves, dropping to the bottom. 



His less active relative, the rough Oyster, in the 

 mean while, is contented to remain fixed to his 

 first station, surrounded by an innumerable pro- 

 geny, continually increasing with wonderful fecun- 

 dity. His motions consist only in turning from 

 one side to the other, which he accomplishes more 

 by sagacity than any natural agility or inherent 

 strength. He contrives to bolster up one side, by 

 a gradual deposition of soft mud, till he stands 

 nearly upright ; then, availing himself of the flow- 

 ing or ebbing of the tide, he opens his shell, and 

 is tumbled over by the pressure of the water. As 

 expedition is not his object, this mode may answer 

 well. 



It has, however, been observed that the young 

 fry possess the power of swimming very swiftly by 

 means of an undulatory motion of the branchiae. 



It is from the words o<rrgs/a or Ur^a, terms ap- 

 plied generally to Bivalves by the Greek naturalists, 

 that the Latin Ostrea and our Oyster are derived. 



