GENERAL ZOOLOGY 



Fig. 14.4. Representative Polychaeta. A. Chaetoplerus as it lies in its parchment-litcc tube; 

 the fan-shaped parapodia maintain currents of water from which small particles of food are 

 sieved by sheets of mucus. B. Peclinana oouldii: the strong; anterior setae are used in burrow- 

 ing;. Note the tube composed of sand strains cemented tog;ether. (.4, redrawn with modifica- 

 tions from A. S. Pearse, 1913, Biological Bulletin, vol. 24; B, photograph by Charles Walcott.) 



head region are modified in a variety of ways, in adaptation to the special 

 requirements of their mode of Hfe. In the errant forms Hke Nereis, however, 

 the parapodia are usually essentially similar in structure and function 

 throughout the length of the body. 



The Class Oligochaeta 



The name Oligochaeta ("few bristles") refers to the fact that the bristles 

 of members of this class are scanty and often inconspicuous. In contrast to 

 the polychaetes, which are predominantly marine forms, the oligochaetes are 

 found almost exclusively in fresh water and in moist terrestrial environments. 

 With the exception of the earthworms, most oligochaetes are small to minute 

 in size. 



The Earthworm: Habitat and General Activities. Earthworms are 

 widely used in studies of the Oligochaeta because they are large enough for 

 gross dissection and are abundant in most localities (Fig. 14.5). They are 



402 



