186 



SYSTEMATIC ZOOLOGY. 



constant motion drawing small food particles to the 

 mouth. As a result of this sedentary life the parapodia 

 are often greatly reduced (fig. 39). Many of the Polycha3ta3 

 are brightly colored and some are among the most beauti- 

 ful objects in nature. 



In the development of many Polychsetes there occurs 

 a larval form known as the trochophore, which bears no 



FIG. 30. A Tubicolous Polychsete (Amphitrite). At the upper end are the 

 tentacles, and just below to the left the gills. 



resemblance to the adult. The body is oval or nearly 

 spherical and bears one or more circles of cilia. The 

 mouth is at one side ; the vent terminal. This becomes 

 transformed into the worm by elongation and segmentation 

 at the hinder end. The great interest connected with the 

 trochophore is that similar larvae occur in other groups, 



