104 



ZOOLOGY 



of sticks, like the muskrat and beaver; that build nests 

 m trees, hke the squirrel; and that rear houses of skins, 

 thatch, brick, stone, and wood, like man. 





Fig, 106. — Mygal( 



a tunnel-woa\'or, allied to the " trajj-door spider." 

 Nat. size. 



In the present chapter we shall consider a group of Arthro- 

 pods, ill which some sort of architecture is nearly universal. 

 This is the group of Spiders (Araneina). They are charac- 

 terized by the fact that the head and thorax are united in 

 one jiiece, called the cephalo-ihorax. The abdomen is con- 

 nected with the cephalo-thorax by a stalk and bears the spin- 

 ning organs (called spinnerets) at its hinder end (Fig. 106). 



