CHAPTER VI 



NEMATHELMINTHES 



INTRODUCTION NEMATOD A ANATOMY EMBRYOLOGY CLASSIFI- 

 CATION ASCARIDAE STRONGYLIDAE TRICHOTRACHELIDAE 



FILARIIDAE MERMITHIDAE ANGUILLULIDAE ENOPLIDAE 



PARASITISM NEMATOMORPHA ANATOMY CLASSIFI- 

 CATION LIFE-HISTORY ACANTHOCEPHALA ANATOMY 



EMBRYOLOGY CLASSIFICATION. 



THE Nemathelminthes include three sub- Orders of very different 

 size and importance. These are 



i. The Nematoda. 



ii. The Nematomorpha (Gordiidae). 

 iii. The Acanthocephala. 



Although the members of these groups differ considerably from 

 one another, on the whole there is a closer resemblance between 

 them than between any one of them and any other group of 

 animals, and there is a certain convenience in arranging them 

 under one head. 



The following characteristics are common to all three groups 

 of the Nemathelminthes : they are worm-like in form, and with 

 few exceptions are parasitic in the bodies of other animals, either 

 Vertebrate or Invertebrate. Some of them spend their whole 

 existence within the bodies of their hosts, but more commonly 

 they are only parasitic during a certain period of their life ; a 

 few, however, lead a free life in water or in damp earth. None 

 of the Nemathelminthes are segmented that is, their bodies are 

 not divided into a number of parts which serially repeat each 

 other, and which resemble more or less closely the preceding and 



