264 



CCELHELMINTHES 



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

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

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

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

 layer of vesicular cells which by their size (fig. 240) so encroach upon the 

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

 organs. 



\.n 



FIG. 244. FIG. 245. 



FIG. 244. Structure of young female A scar is (based on a drawing by Leuckart). 

 d, intestine; o, ovary; p, pharynx; s, lateral line; v, ventral line; va, vagina. 



FIG. 245. Diagram of nervous system of a nematode (after Biitschli). c, com- 

 missures; ii, dorsal nerve; i, infracesophageal, s, 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 expanded posteriorly to a 

 pharyngeal bulb and is lined throughout with a cuticle. From this point to 

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

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



