76 Laboratory Guide in Zoology 



The class Arachnida includes the spiders, scorpions, 

 and mites. In these there are two chief divisions of the 

 body, — the cephalothorax and abdomen, eight legs, no 

 antennae, and generally no distinct transformations. With 

 unimportant exceptions they breathe air either by means 

 of tracheae or of book-lungs, and have a varying number 

 of simple eyes upon the cephalothorax. 



