NEREIS AND ITS ALLIES 



149 



they can be thrust out of the tube ; the mouth comes to lie at 

 the bottom of a funnel, which receives as food small parti- 

 cles floating in the water; even the segmentation of the 

 body becomes lost at the hinder end of the animal ; in a 

 word, all those organs which are useful for active carnivo- 

 rous life have become re- 

 duced to the bare needs of 

 a quiet herbivorous life. 



FIG. l.'JG. Amphitnte, removed from its 

 tube. Nat. size. Photo, by W.H.C.P. 



FIG. 137. Polycirrus, the blood 

 spot. Nat. size. Photo, by 

 W. H. C. P. 



The first of these sedentary worms that we have to con- 

 sider is not completely modified from the type found in 

 free-living species. 



Cirratulus 1 lives in tubes in mud or sand. It is yellow 

 1 From cirrus, curl, ringlet. 



