SECT. rx. POLYZOA. 221 



have organs also called vibracula, which are bristle- 

 shaped, as on A, fig. 158; these sweep over the surface 

 of the Polyzoon to remove anything that might injure 

 the polypes. 



It is believed that the polypes of the Polyzoa are 

 male and female, and that the ciliated locomotive larvae 

 which appear in spring are developed from eggs. The 

 fresh- water Polyzoa are as worthy of microscopic exami- 

 nation as the marine. 



