'29 



III. REPRESENTATIVE NEMATHELMINTHES 



REFERENCES 



In addition to the general texts already cited see, especially, Hall, '12; 

 Neveu-Lemaire, '12; Ransom. '11; Stiles, '07; Ward '03; and the special arti- 

 cles cited in discussing various species. 



Class NEMATODA 



The great majority of the Nematoda, or "thread-worms," are 

 internal parasites of animals in the whole or part of their life but 

 some infest plants and many live free either in water or damp earth. 

 The classifieation of this group is in a very unsatisfactory condition, 

 but we shall follow Neveu-Lemaire in arranging the families and 

 shall discuss a representative of each. This grouping does not 

 differ essentially from that used by Ransom, '11. 



FAMILIES OF NEMATODA 



(As defined by Neveu-Lemaire, '12) 



Ascaridae — Body relatively thick; mouth usually surrounded 

 by three lips, which are often supplied with papillae. One lip dorsal, 

 the two others touching on the median line of the ventral surface. 

 Oesophagus long, muscular, swollen posteriorly and at times followed 

 by an oesophageal bulb. Males provided with one {Oxyuris) or usu- 

 ally, two spicules. Females with a double ovary; oviparous. 

 Development direct. Ascaris, Heteralcis, Oxyuris, et al. 



Strongylidae — Body elongate, cylindrical, rarely filiform. Mouth 

 in some cases terminal, in others inclined towards the dorsal or ventral 

 surface. Oesophagus more or less swollen posteriorly but never 

 with a posterior bulb. Males with a caudal bell-shaped bursa 

 supported by thickened rays, the so-called hooks, and with two 

 equal or subequal spicules. Vulva may be in front of the middle of 

 the body but is usually behind the middle. Many species formerly 

 included under the genus Strongylus are included in this family 

 under various generic names; includes also the hookworms, gape- 

 worm, et al. 



