CLASSIFICATION OF THE NEMATODA 375 



Development often requires an intermediate host. This family is at present 

 ill-defined, but has been already subdivided into several sub-families, Filariince, 

 OnchocercincE, Arduennince. 



Family. Trichinellidae, Stiles and Crane, 1910. 



(Esophagus consisting of a chain of single cells, the lumen of the oesophagus 

 passing through their centre. Ovary single. Vulva at junction of anterior and 

 posterior portions. Sub-families : (i) Trichutina^ (2) Trichinellincc . 



Family. Dioctophymidae. 



Body anteriorly armed with spines or unarmed ; mouth without lips, with 

 six, twelve, or eighteen papillae in one or two circles ; oesophagus very long 

 without a bulb ; anus terminal in female ; one ovary ; vagina very long ; spicule 

 in male very long ; bursa cup-shaped without rays (Dioctophyme, Hystrichis, 

 Eustrongylides). 



Family. Strongylidae, Cobbold, 1864. 



Bursa, supported by rays, always present. Oviparous. 



Family. Physalopteridae. 



Mouth with two large lips. Bursa with supporting papillae in form of a 

 lanceolate cuticular expansion, with genus Physaloptera. 



Family. Ascaridae, Cobbold, 1864. 



Rather thick Nematodes. Mouth with three lips one dorsal, two latero- 

 ventral. Sub-families : (i) Ascarince, (2) Heterakince^ etc. 



Family. Oxyuridae. 



Smallish forms, 4 to 45 mm., with cuticle thickened on each side for the 

 whole length of body in the form of a lateral flange or wing. (Esophagus long 

 with a well-marked bulb containing a valvular apparatus. Tail end of female 

 drawn out into a long point. Eggs asymmetrical. Males very srriall (about 

 2 mm.). One spicule. Genera : Oxyuris, Passalurus, Ozolaimus, Atractis, etc. 



MermithidcE, greatly elongated " Nematodes," which, in the larval stage, are 

 parasitic in insects, but in their adult condition are free living. Cuticle with 

 diagonal striation. Without an open mouth or anus. Oral papillae present. 

 Characteristic eggs with two processes, ending in a tuft of filaments. Larvae 

 with a movable boring spine at the head end. 



Gordiidce. Long, thread-like " Nematodes." Mouth and anterior portion of 

 gut atrophied in adult. Oral papillae absent. 



