138 FIRST BOOK OF ZOOLOGY. 



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

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

 been growing, 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. 



Fi&. 127. — A ToTTNa Lobster magntfied. — a eliows tlie Natural Size of the Creature. 

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



CHAPTEE XYIII. 



CEABS, HEEMrr-CEABS, AND OTHEE CEUSTACEAJSTS. 



128. The class of animals to whicli the crawfish and 

 lobster belong i.s 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 gi-eat lakes and other fresh 



