106 



OHAS. B. WILSON. 



body contractions must be of great service to the worm in 

 escaping from its enemies and in obtaining its food. In 

 locomotion the proboscis seems to be of use chiefly as an 

 organ of feeling or touchy being thrust forward to determine 

 the direction in which the burrow is to be made. Whenever 

 it strikes an obstacle^ such as a small stone, it feels around 

 itj sometimes on several sides^ and selects apparently the 

 place that offers least resistance. 



In doing this it often happens that the proboscis will be 

 thrust up into the water. It is then quickly withdrawn only 

 to be thrust up again^ perhaps in a very few seconds. 



The only idea of direction, therefore, seems to be to keep 

 beneath the surface of the mud. It is also evident that when 

 the proboscis is thrust forward forcibly into the mud or 

 sand, it makes an opening for the subsequent passage of the 

 head. 



The worm may often be seen to withdraw its proboscis 

 and push its head along in the opening thus left. It is also 

 possible that the proboscis may have some tractile power in 

 helping to pull the body forward. That it is actually used 

 as an organ of prehension was witnessed several times. 



The Nemerteans were fed with common clam-worms (Ne- 

 reis). When a Nereis in wriggling about came in contact 

 with a Nemertean, or crossed the mouth of a burrow when a 

 Nemertean was inside, the latter suddenly darted out its 

 proboscis and coiled it spirally around the Nereis. The spiral 

 coil covered an inch or more of the Nereis's body, and the 

 proboscis was then slowly withdrawn, bringing the Nereis 

 up to the Nemertean's mouth, where it was finally swallowed. 

 This corresponds exactly with the graphic description given 

 by Kingsley (cf. 34) of a specimen of the species Polia 

 mandilla (Amphiporus lactif loreus, Mcintosh) in the 

 act of devouring a fish. Mcintosh, however, questioned 

 Kingsley's accuracy (34), because the latter says that the 

 proboscis assists in prehension, but Cerebratulus certainly 

 uses it sometimes for that purpose. 



When withdrawn the proboscis is coiled up in that portion 



