154 



A COURSE ON ZOOLOGY. 



FIG. 87. 



CHAPTER XVII. 



Worms Parasites General Character of Anar- 

 thropoda. 



UNDER the name worms or annelides are designated 

 creatures of a class that resembles the articulates, be- 

 cause the bodies of its members are composed of rings 

 joined end to end and movable one on the other; but 

 the anarthropoda differ from the articulates in that they 



never have limbs composed 

 of articulated joints. Many 

 of them have no limbs 

 whatever, and when such 

 appendages are present, 

 they are reduced to simple 

 rounded prominences car- 

 rying stiff hairs, called 

 cirri. 



The order of anarthro- 

 poda includes two impor- 

 tant classes, the worms and 

 the parasites or entozoa. 



WORMS. 



Most species of worms 

 have red blood ; their res- 

 piration is either branchial 

 or cutaneous. Their appa- 

 ratus of locomotion consists 

 sometimes of cirri variously grouped on fleshy tubercles, 

 sometimes of short ventral hairs, sometimes of suckers. 



SERPULA CONTORTUPLICATA (with 

 expanded gills) on the back of an 

 oyster-shell. 



