VI 



PHYLUM NEMATHELMINTHES 



301 



chamber with muscular walls, the gizzard (Fig. 251, gz.). The only 

 specially interesting variation in the structure of the intestine 

 is that occurring in Trichinella (Fig. 253), one of the Nematodes 

 parasitic in Man, in which this part of the enteric canal consists of 

 a single row of perforated cells (zh): the lumen is therefore not 

 wter-cellular but wZra-cellular, like the gullet of an Infusor. In the 

 sexual stage of Gordius and in Nectonema the enteric canal under- 

 goes more or less complete degeneration, and in several other genera 

 there is no anus. The alimentary canal in some rare cases has 

 hollow appendages in the form of cesophageal glands or intestinal 



FIG. 250. Transverse section of Gordius (female) in the posterior region, cut. cuticle ; d. c. 

 dorsal canal ; div. diverticulum of lateral canal ; ep. deric epithelium ; int. intestine ; 

 I. c. lateral canal ; m. 1. muscle layer ; m. v. c. median ventral canal ; n. c. nerve-cord ; 

 par. parenchyma ; sp. th. spermatheca. (After Rauther.) 



caeca. In Dochmius a pair of pear-shaped bodies of unknown 

 function, the cervical glands (Fig. 249, B, cv. gl.), lie one on each side 

 of the pharynx and probably open externally near the mouth. 



In the Nematoidea the body-cavity is always a single continu- 

 ous chamber crossed in various directions by delicate fibres and 

 without epithelial lining. In Gordius the body is solid in the 

 larva, filled with polygonal cells (parenchyma), but fissures appear, 

 and, increasing in extent, eventually give rise to extensive canal- 

 like cavities a median ventral and two lateral, with, in the female, 

 a narrow median dorsal, separated from one another for the most 



