CHAPTER VI 



Nemathelminthes. Nemas 



The Nemathelminthes (Gr. nema, thread; helmins, an intestinal 

 worm) or Nemas live in fresh and salt water, damp earth and moss, 

 and among decaying substances; many are parasitic. They are 

 often minute in size and some may remain viable when dried. They 

 vary in size from o.oi to i meter or more in length. 



Classification. (Modified) 



Class Nematoda 



Fam. I. Ascaridae. 



1. Anguillulidae 



3. Strongylidae. 



4. Trichuridae. 



5. Filaridae. 



6. Trichinellidae. 



Characteristics 



I. Elongate worms, many parasitic. 



1. Body usually cylindroid and unsegmented. 



3. A nerve ring with associated ganglia. 



4. Single and paired excretory organs, and tubular gonads. 



Natural History 

 Dr. N. A. Cobb states (Nematodes and their Relationships): 



"The number of species of nematodes must be enormously greater than 

 is commonly supposed. It may be estimated that more than 80,000 

 nematode species infest the 40,000 species of vertebrates. Insects, 

 much infested, will add many thousands of other species. The mollusks, 

 crustaceans and various groups of worms are also infested and investiga- 

 tions continue from these species also to augment the number of known 

 species of parasitic nematodes. 



" Numerous as the parasitic species are, it is certain that the nematodes 

 living free in soil and in water far out-number them; they probably con- 



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