THE BRISTLE-WORMS. 



99 



//t 



relatively little movement. In the leaf-worms the plates 



are attached by one end only, so as to be freely movable. 



Both the dorsal and ventral cirri are modified to form these 



plates, but the dorsal are the larger. 



Besides serving as locomotor organs, the 



cirri have another function. When the 



worms are irritated or attacked, they 



pour out an abundant jelly-like secretion, 



which examination shows to be produced 



by glands on the plates. It is probable 



that this mucus protects them from some 



enemies. It is poured out in special 



abundance when one employs any of the 



ordinary reagents to kill the worms, and 



in consequence spoils them very much as 



specimens. Inrsome species the plates fall 



off almost as readily as do the scales of 



Polynoids. 



Of the type genus Phyllodoce we shall 

 consider two species only, which differ 

 from one another in appearance very 

 markedly. These are the small brown 

 Phyllodoce maculata, and the large green 

 P. lamelligera. The former, or spotted 

 leaf-worm, occurs freely among the shore 

 rocks, especially among sand. It reaches 

 a length of from three to four inches, but 

 is very slender in proportion to its length, 

 a worm of about three and a half inches 

 long being not more than about one-tenth 

 of an inch broad. It is an active little 

 creature, wriggling over the surface of the 

 sand, or swimming through the water 

 with all its plates in active movement. 

 The colour is not unlike that of sand, 

 being a pale brown with three very dis- 

 tinct dark brown spots on each ring. As in all species of 

 Phyllodoce^ the head (see Fig. 34) bears four small tentacles 

 near its anterior end, and a pair of distinct dark eyes near 

 its posterior margin. Behind the head proper are three 

 segments more or less fused, and bearing in all four pairs 



or Phyllodoce lamel- 

 llgera. 



