186 



FIRST BOOK OF ZOOLOGY. 



Worms. 



Class Crustacea (lobsters, crabs, barnacles, etc.). Difficult 

 to define, but including animals which pass through a series 

 of moults in their growth, though in this respect resembhng 

 the spiders, and breathing by means of gills, and in this 

 respect differing from other arthropods. 



