i 7 8 



COLLEGE ZOOLOGY 



Nemertines feed on other animals, both dead and alive. They 

 live, as a rule, coiled up in burrows in the mud or sand, or under 

 stones, but some of them frequent patches of seaweed. Loco- 

 motion is effected by the cilia which 

 cover the surface of the body, by 

 contractions of the body muscles, 

 or by the attachment of the pro- 

 boscis and subsequent drawing 

 forward of the body. Cerebratulus 

 (Fig. 117) swims actively like a 

 leech (Chap. XI). The power of 

 regenerating lost parts is well 

 developed. 



During development a peculiar 

 larval stage called the Pilidium 

 (Fig. 118), is usually passed 

 through. This resembles a helmet 

 with cilia on the surface and a 



Fig. 117. — Cerebratulus fus- 

 cus, a Nemertine. i, cephalic 

 slits ; 2, opening leading into 

 retracted proboscis; 3, dorsal 

 commissure of nervous system; 

 4, ventral commissure; 5, brain; 



6, posterior lobe of brain; 



7, mouth; 8, proboscis; 9, lateral 

 vessel; 10, proboscis; 11, pouches 

 of alimentary canal; 12, stomach. 

 (From Shipley and MacBride, 

 after Burger.) 



Fig. 118. — Pilidium larva of a Nemer- 

 tine. D, alimentary canal; E, E', the 

 two pairs of ectodermal invaginations. 

 (From Sedgwick, after Metschnikoff.) 



