CHAPTEE VII 

 ANNELIDA {continued) 



Class I. : CHAETOPODA {continued) 



The Bristle -worms of the Sea. 



These sea-worms differ from earthworms in several points, 

 but resemble them in having the same type of segmented 

 body, bearing bristles. Unlike earthworms, they have usually 

 a distinct head, with eyes and feelers on it, and also well- 

 marked breathing organs or giUs, which project freely from 

 their bodies, and which, in those genera which build round 

 their bodies a hard tubular case, often form a conspicuous 

 and beautiful frill, projecting at the free end of the tube. 

 Further the chaetae or bristles are in clusters, situated on 

 definite stump-like projections of the body (parapodia) and 

 forming, in the free-swimming worms, eflScient little paddles. 

 Because of this arrangement of the chaetae in clusters, these 

 marine worms are called Polychaets. 



Free-swim- Many of the free-swimming sea-worms (Errantia) 

 ming forms are common in rock pools or on the rocks left un- 

 (Errantia). covered by the tide. These forms are predatory and 

 have sharp jaw-like structures in their mouths. The Paddle- 

 worm {Phyllodoce lamelligera) is one of these (Fig. 38). It is a 

 beautiful iridescent green form, with a body usually 8 to 1 2 

 inches long, though it may be as much as 2 feet in length, 

 and ^ an inch across. It is commonly to be found lying under 

 stones near low tide mark. These worms are often called 

 " leaf worms," because of the leaf-like paddles which develop 

 on the bristle-stumps (parapodia), and form an overlapping 

 row down each side of the body. 



Aphrodite, the Sea Mouse, is another of the free forms, 

 though it has too clumsy a shape to swim freely, but crawls 



83 



