ANNUL03A ANNELIDA. 75 



the first and last. These rings are often very numerous, 

 amounting in some groups to several hundreds. A ring 

 or segment, in the higher groups, consists of two arches, 

 a dorsal and ventral; and each of these bears two pro- 

 tuberances, placed on the sides of the animal, which have 

 been called "foot tubercles.' 7 These tubercles support 



A 



FIG. 31. GROUP OF ANNELIBES. 

 A, Myrianida; B, Serpula; C, Lob-worm; D, Spirorbis. 



bundles of bristles which surround a soft jointed filament, 

 called the cirrhus. These bristles, by pressing against 

 the ground, assist in locomotion. Jointed limbs are 

 never met with in any animal of this class, nor are the 

 organs of locomotion ever transformed into foot-jaws. 



100. Digestion. There is a mouth, sometimes fur- 

 nished with horny jaws, a gullet, stomach, and intestine, 



