406 MYTILACE.E ; LITHODOMI ; DREISSENA. 



947. The Lithodomi are endowed with the power of per- 

 forating stone and masses of coral, as well as large shells of other 

 Mollusca. In the earlier stages of life, it is stated by Cuvier, 

 the Lithodomi suspend themselves by their byssus ; but when 

 they have pierced the bodies to which they are attached, and 

 introduced themselves into the cavity, the byssus disappears. 

 The excavation does not seem to be here produced by the 

 mechanical action of the shell, which is not adapted for such an 

 office. Nor is there any reason to believe that it is occasioned 

 by a solvent fluid secreted by the animal. It is attributed by 

 Mr. Garner principally to the currents of water constantly im- 

 pelled against the rock by the vibration of the cilia ; and in this 

 supposition there is much probability. The lithodome Mussels, 

 as well as others, are used as food where they abound ; and 

 means have been taken on some parts of the coast, to cause them 

 to multiply. As with Oysters, it appears that the Mussels are 

 rendered more tender, and the quality of their flesh improved, 

 by putting them in places where the saltness of the sea- water 

 is tempered by rain or river- water. Accordingly, on the coasts of 

 France and Italy, regular breeding-places have been established, 

 where those which have been obtained from the sea are cast for 

 a time to improve their quality, and where also the spawn is 

 reared ; these are so arranged as to communicate with the sea, 

 but to #llow the intermixture of fresh water at pleasure. Like 

 all Mollusca which congregate upon the shores, Mussels serve as 

 an article of food to other animals besides Man. Many sea-birds 

 detach them from their situation by breaking the shell, and then 

 feeding on them. And there are Mollusca of higher Orders, 

 which are enabled to pierce their shells, and which then suck out 

 the soft parts by their proboscis. 



948. A Mollusk allied to the Mussel, the Mytilus polymor- 

 phus, or Dreissena polymorpha, has been recently introduced into 

 this country ; and affords an interesting example of the complete 

 naturalisation and rapid multiplication of a foreign species. This 

 is evidently due to the variety of circumstances under which it 

 can exist. It is found abundantly in the Black Sea, the Baltic, 

 and other salt inland seas ; and it lives, like the Mussel, in 



