CLASSES AND SUB-KINGDOMS. 185 



Class Arachnida (spiders). Animals whose bodies are 

 segmented. The segments grouped together into two re- 

 gions, the cephalo-thorax and the abdomen. Having four 

 pairs of legs, and breathing air through openings in the body. 



The word arachnida is derived from a Greek word, 

 arachne, spider. 



ARACHNIDS- 



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 resembling 



