264 



CCELHELMINTHES 



unpaired pore to the exterior. They are related to the coelom by two 

 giant cells on eitlier side which send processes into the body cavity. 

 These lateral and median lines chvide the muscles (here only longitudinal) 

 into four fields. These muscles are parts of tlie somatic epithelium, a 

 laver of vesicular cells wlrich by their size (fig. 240) so encroach upon the 

 caMom that scarce space is left for the alimentary canal and reproductive 

 ortrans. 



^" 



Fio 



Fig. 244. Fig. 245. 



J44. — Structure of vount; female Asciiris (based on a drawinp; by Lcuckarl). 



</, intestine; n, ovar\-; /), pharynx; i, lateral lino; ■:', ventral line; I'u, va,^ina. 



I'"n-.. 245. — Hiagram of nervous system of a nematode (after Biilsehli). r, com- 

 missures; (/, dorsal nerve; /, infracesophageal, .?, supracesophageal part of nerve ring; 

 V, ventral nerve. 



The alimentary canal begins with a terminal mouth and ends with 

 the ventral anus in front of the end of the body. The mouth connects 

 with the muscular sucking oesophagus, which is expantled posteriorly to a 

 pliaryiii^cal bulb and is lined througliout with a cuticle. From this point to 

 the anus the stomach-intestine is usually uniform (fig. 244). The crsoph- 

 agus is surrounded by a nervous ring wlrich sends forward and back a large 



