WORMS 



73 



The Terebella glues around its body a number of 

 grains of sand and bits of shell, thus forming a 

 case; the projecting threads at the head end are 



A fc 



FlG. 12. Worms. A, a Sea-Mouse, Aphrodite aculeata; 

 Terebella littoralis ; C, Syllis ; D, Serpula vermicularts ; 

 Spirorbis nautiloides, on a piece of seaweed. 



the gill-filaments, borne by the anterior segments 

 of the body. These are plumed ; the thread-like 



