326 Animal Biology 



Fig. 138. — Representatives of the class Arachnoidea, phylum Arthropoda. A, 

 Scorpion; B, jumping spider {Attus sp.) ; C, human itch mite {Sarcoptes scabiei) , 

 male, much enlarged; D, hair follicle mite {Demodex jolliculorum) , much en- 

 larged; E, daddy-long-legs or harvestman {Phalangium sp.). 



Proboscis / /V/oafeK 

 Noiochord 



Ventral ve'sse) t^ nerve 



Fig. 139. — Balanaglossus, a. marine chordate of the subphylum Hemichordata. 

 Observe in the chordate characters, the gill slits, dorsal notochord, and dorsal nerv- 

 ous system in the section below. 



