ANNULATA. 



201 



biting jaws for the holding of prey. They also have 

 special outgrowths of the body wall, in the form of thin 

 gill-like structures, for the purpose of respiration. There 

 are two main types of the marine worms the free-swim- 

 ming forms such as the sand worms (Nereis) , and the tube 

 worms ( as Amphitrite, Fig. 59) . The latter may burrow 



FIG. 59. Amphitrite ornata, from Verrill. A tube-dwelling annelid. 



Questions on the Figure. What is the nature of the outgrowths 

 at the anterior end? What functions might they have? Consult 

 reference texts. 



in the sand and make their tubes there, or may form solid 

 tubes -of limy matter (as Serpula) . In the fixed forms 

 the head region is even more highly specialized. The 

 tentacle ana gills are located here, 'and sometimes they 

 come to have an enormous length and number. 



218. Leeches. These animals live in water, have no 

 seta?, are usually temporary parasites in habit, and have 



