CLASS VEKMES: OKDER NEMATELMINTHES. 239 



the alimentary canal of the hog. Its proboscis is retractile 

 and is armed with four circlets of sharp, recurved spines sur- 

 rounding a simple suctorial mouth. (Fig. 408.) Koleops 

 is another genus found in the eel. 



ORDER NEMATELMINTHES. 



General Characteristics. The Nematelminthes 

 (thread-like worms) are parasitic during a portion of their 

 lives in the interior of various animals. The head is without 

 a circle of hooks and the sexes are separate. 



G-ordiidae. The Hair- 

 snake is so called from the r ^ n 

 erroneous notion that it 

 originates from horse- 

 hairs soaked in water. 



Probably, by the eggs Gor(fms aq ^^ } Hai^ke. a. Tail. 

 being eaten, the larvae 

 obtain access to the bodies of grasshoppers, etc., and, coiling 

 up within the cavity, reach a length oftentimes tenfold that 

 of their host. At maturity, they desert the insects at whose 

 expense they have been nourished, and seek the water to lay 

 their eggs and die. 



Trichina spiralis, Muscle-worm. 

 I. Migrating in muscles; 2. Encysted; 3. Free state. 



Trichinidse (hair-worms). The Trichina is parasitic in 



