166 UTILIZATION OF MINUTE LIFE. 



Professor Kickx (that Van Beneden calls Dreissena 

 polymorpha, and which has been honoured with a 

 host of other names besides), are probably carried 

 about the world on the keels of ships, and very 

 widely diffused. 



The species just mentioned, M. area, is found 

 inhabiting seas, lakes, rivers, marshes, etc., ex- 

 tending over nearly the whole surface of Europe, 

 from lat. 43 N. to lat. 56 N. It is, moreover, 

 found in the earth in a fossil state.* 



A highly-nutritious mussel, Mytilus lithophagus, 

 L. (or Modiola litliopliaga, Lam.), common enough 

 in the Mediterranean and at the Antilles, has the 

 fuculty of burying itself alive, as it were, by pene- 

 trating into wood, stones, and rocks, as the Teredo 

 and Plwlas bore into ships. 



The M. lithophagus form, even in the hardest 

 rocks, cavities which they can never leave, in con- 

 sequence of their increasing in size as they grow 

 older. 



The common oyster (Ostrea edulis), a bivalve 

 mollusca, too well known to need description here, 

 is subject to great variation. Many different varie- 

 ties have been observed in nature, or artificially 

 produced by culture. A single oyster brings forth 

 from one to two million of young, of which the 



* On this curious mussel, see Van Beneden in " Ann. des Sc. 

 Nat., 1835." 



