62 



VEEMES. 



Hesione. 

 Castalia. 

 Psamathe. 

 Podarce. 



Eunicidce. 



Eunice = Marphysa. 

 Diopatra. Tomopterus. 



Order IV. CEPHALOBEANCHIA. 



SEDENTARIA. TUBICOL^E. POLYCIIJETA. 



Worm-like, marine animals, mostly protected by a tube. Body 

 presenting distinct regions. Eespiration by branchiae placed near 

 or on the head. Sexes distinct. A metamorphosis. 



The tubes are mostly secreted by the animal itself, and are 

 either calcareous or membranous, or they may be composed of 

 grains of sand agglutinated together. The tubes are either free 

 or adherent to some foreign body, and the animal is not organi- 

 cally attached to them. The branchiae are generally filamentous 

 and fringed with vibrating cilia, but they are sometimes absent. 

 The blood in Sabella is olive-green. There is no proboscis. The 

 embryo is a free-swimming ciliated body. 



A few fossil forms are known. Spirorbis and other tubicolar 

 annelids occur as early as the Silurian period. Some forms, as 

 Ditrupa, have been taken for shells of mollusks allied to Den- 

 talium. 



