OF THE ANNELIDES. 497 



THE SECOND SUB-DIVISION. 

 OF THE ANNELIDES, OR ANNULATED ANIMALS. 



THE YEBMES, OR WORMS. 



582. In these animals the annulated division of the 

 body becomes less and less marked ; every structure becomes 

 as it were degraded in proportion as we leave those most re- 

 sembling the articulated to those approaching the zoophytes ; 

 the limbs disappear, and the nervous system becomes less and 

 less distinct, or loses its importance, and the structures sim- 

 plify more and more. Their most remarkable feature is the 

 elongation of their bodies, and they form five distinct classes ; 

 namely, the annelides, rotatoria, turbellaria, helminthides or 

 intestinal worms,* and cestoids. 



OF THE ANNELIDES. 



583. The class is composed of worms having a multi- 

 gangular nervous system, and a vascular apparatus for the 

 circulation of the blood. 



Fig. 524. Nereis ; Mudworm.* 



Their bodies are always elongated, soft, and divided by cir- 

 cular folds into a great number of rings ; sometimes the head 

 is distinct, sometimes it is wanting ; and generally along the 



* Entozoa. 



t Called mudworm by the fishermen of Dover, who use them as bait for 

 the white mullet, numbers of which are taken by angling at the mouth of the 

 harbour. E. K. 



K K 



