Phylum Nemathelminthes and Related Phyla 427 



The Anatomy of Chiloplacus. — Externally the sexes are easily 

 separated by the appearance of the posterior portion of the body: the 

 female is straight and pointed, while the male is abruptly curved. Also 

 the male often has projecting spicules. The digestive tract is essen- 

 tially a straight tube leading from the mouth to the anus. The an- 

 terior portion is somewhat modified in relation to the feeding habits 



Fig. 139. — The anatomy of the nematode, Chiloplacus sp. A, Female; B, male. 



of this worm. Directly behind the mouth is the buccal cavity which 

 leads into the muscular pharynx. The posterior portion of the pharynx 

 is enlarged to form the pharyngeal bulb. The muscles of the pharyn- 

 geal bulb act as a suction pump to draw food into the mouth. It is 

 possible that this bulb also acts as a valve to control the passage of 

 materials into the long straight intestine. At the posterior end of the 



