MOLLUSKS. 191 



again. Mollusks have, in a greater or less degree, the 

 senses of the higher animals, though they greatly 

 differ among themselves in this respect. 



The kinds of mollusk are very numerous, not less 

 th'an fifteen or twenty thousand. They abound in the 

 sea, on the marshes, in pools, streams, ponds, and lakes, 

 and on the land ; and they are full of interest when 

 we study them, and all serve some important purpose. 

 They are the food of many other animals. The Right 

 Whale feeds upon small kinds which swim freely in the 

 open sea; the Cod and Haddock and many other use- 

 ful fishes fatten upon those gathered near or on the 

 bottom ; and -sea-birds feast upon those left bare by 

 the tide. Man reckons the Oyster, Clam, and Scallop 

 among his choicest dishes ; and in seasons of scarcity 

 the poor inhabitants on many a sea-coast depend upon 

 mollusks for a large part of their daily food. These 

 animals also furnish the bait for all the extensive fish- 

 eries of the North Atlantic. Some of them yield rich 

 dyes. The celebrated Tyrian purple of the ancients 

 was obtained from shell-fish. 



The shells of mollusks are limestone, or carbonate of 

 lime. Pearly within, and even without when polished, 

 and of soft and delicate colors, they are often exceed- 

 ingly beautiful, and are eagerly sought for. The child 

 gathers them for toys, and thinks he hears the roaring 

 of the sea as he puts them to his ear; the savage 

 wears them as ornaments, and some of them as marks 

 of chieftainship ; some kinds are gathered by civilized 

 nations and used instead of money in trading with bar- 

 barous tribes ; other kinds are gathered and wrought 

 by skilful hands into almost numberless articles of use 

 and luxury; and the true naturalist, more enthusiastic- 



