CHAPTER XXVI 



NEMATHELMINTHES 



Nemathelminthes — Nematoda — Anguillulidae — Angiostomidae — ■ Gnatho- 

 stomidae — Physalopteridae ■ — • Filariidae ■ — ■ Dracunculidse — Mermithidse — 

 Ascaridae — Oxyuridae — Strongylidse — Metastrongylidae — Trichostrongy- 

 lidae — Ankylostomidae — Eustrongylidae - — Trichinellidae — ^Trichurineae — 

 Gordiacea — Acanthocepliala — -References. 



PHYLUM II. NEMATHELMINTHES. 



Metazoa, worm-like in form, tubular, or filiform, unsegmented, but 

 covered with a cuticle which may be ringed. Without appendages 

 or limbs, but usually with bristles, hooks, papillae, or, rarely, suckers. 

 Usually with an alimentary canal, but without any closed vascular ' 

 system, and without respiratory organs. With a complete absence 

 of cilia. Sexes are separate. Usually parasitic through some part - 

 of the life-cycle, in which the larvae develop in a different host or 

 organ from that occupied by the adult. The larvfe may be free 

 and the adult parasitic, or w'c^ y^fs^?. 



Remarks. — The Nemathelminthes are extremely important to the 

 student of tropical medicine, for they include some of the most 

 potent agents of disease — e.g., An:ylostoma duodenale and the 

 FilariidcB. Recent researches have shown that, no matter how 

 common the worm may appear to be, it is advisable to carefully 

 study it, as it has been found that several species and genera 

 have been included in an old species which was thought to be 

 so well known, that nothing new could be discovered concerning 

 it — e.g., Ascaris, in examining specimens of which Leiper has 

 separated two new genera. 



Classification. — ^The Nemathelminthes can be divided into two 

 classes: — • 



Class L — ^Anterior end not provided with an armed proboscis; 

 intestine present either complete or in part rudimentary. 

 This class includes two orders : — 



Order I. Nematoda. 

 Order n. Gordiacea. 



Class IL— Anterior end provided with an armed proboscis; 

 intestine absent. 



Order in. Acanthocephala. 

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