'52 



MANUAL OF ZOOLOGY 



SECT. 



ph.), with very muscular walls. Posteriorly the pharynx 

 opens into the intestine (int.), a thin 

 walled tube, flattened from above 

 downwards. Posteriorly the intes- 

 tine narrows considerably to form 

 the short rectum, which opens ex- 

 ternally by the anus (an.). The 

 food, consisting of the semi-fluid 

 contents of the intestine of the 



"Ut/l 



host, is sucked in by movements of 

 the pharynx, and is then absorbed 

 into the system through the walls 

 <#n o f tne intestine. The food being 

 already digested by the host, there 

 is no need of digestive gland-cells 

 \ such as occur in animals which pre- 



pare their own food for absorption. 



Between the enteric canal and 

 the body-wall is a distinct space, 

 fan tne ccelome or body-cavity, contain- 

 ing a clear fluid. 



The excretory system presents a 

 certain resemblance to that of Platy- 

 helminthes. It consists of two 

 longitudinal canals (ex.v.), one in 

 each lateral line. Anteriorly they 

 pass to the ventral surface, unite 

 with one another, and open by the 

 minute excretory pore (ex.p.) al- 

 ready noticed. 



The nervous system consists of a 



FIG. 77. Diagram of Nervous 

 system of Nematoda. c . com- 

 missures ; din. dorsal nerve ; 

 hsn. posterior lateral nerve ; 

 on. upper and . under 

 portion of nerve-ring ; sg. / \ , . , , 



lateral swellings \yin. ventral ring (nv.r. ) surrounding the pharynx 

 and giving off six nerves forwards 



nerve. (From Lang, after 

 Biitschli.) 



