138 FIRST BOOK OF ZOOLOGY. 



which some one of the legs will be much smaller than its 

 mate on the other side. This shows where a new leg has 

 grown, to replace one previously lost. 



127. The young passes through a remarkable series of 

 moults, or shedding of the shell, and each moult brings it 

 nearer in appearance to the general form of a lobster. The 

 following figure presents the appearance of a young lobster 

 which has undergone several such moults. 



a 



FIG. 127. A YOUNG LOBSTER MAGNIFIED. a shows the Natural Size of the Creature. 

 (Reduced from a Figure drawn by Sidney I. Smith.) 



CHAPTER XVIII. 



CKABS, HERMIT-CRABS, AND OTHER CRUSTACEANS. 



128. THE class of animals to which the crawfish and 

 lobster belong is called Crustacea, a name derived from a 

 Latin word, crusta, meaning a crust, or the shell with which 

 the animals of this class are covered. 



To this class belong the crabs, hermit-crabs, shrimps, 

 and an infinite variety of forms found in salt-water, certain 

 little creatures found in the great lakes and other fresh 



