CHAPTER XVIII 

 THE ROUND WORMS 



CLASSIFICATION OF THE NEMATHELMINTHES (ROUND WORMS) 



Class 





Nematoda 



Family 

 Angiostomidae 



Filariidae 



Trichotrachelidae 



Strongylidae 



Ascaridae 



Acanthocephali 



Hirudinei 



NOTE. The Strongyloides stercoralis was formerly described under two desig- 

 nations: (i) Anguillula inteslinalis, a parasitic generation and (2) Anguillula ster- 

 coralis, a free living generation. 



ROUND WORMS OR NEMATODES 



All nematodes are covered by a cuticle which varies in thickness, 

 and is frequently ringed. The cuticle is moulted three or four times. 



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