498 



sides of the body they have a long series of hairs in bundles, 

 supported on fleshy tubercles, taking the place of feet (Fig. 

 524). Frequently we find two of these organs placed one 

 above the other, on either side the different rings of the 

 body (Fig. 413) ; at other times these 

 bristle-carrying tubercles are reunited, 

 and there is found at the base of each 

 a long, soft cylindrical appendix called 

 cirrhus (c, Fig. 525) ; sometimes the 

 place of the feet is marked by merely 

 a few stiff hairs, whilst in others all 

 traces of limbs have disappeared. 

 These hairs or bristles serve as instru- 

 ments of defence and of locomotion; 

 they are in general sharp, and calcu- 

 lated to attach the animals to any soft 

 body with which they come in contact. In the annelides, 

 which have no bristles, there exist at the extremities of the 

 body, suckers which answer the purpose. 



584. Their nervous system consists of a chain, single or 

 double, of very small ganglions, extending from one extremity 

 of the body to the other. Most have a few dark spots, which 



Fig. 525.* 



Fig. 526. Head and Proboscis 

 of a Glycera.f 



Fig. 527. Head, &c., 

 of a Nereis. 



seem to be the eyes, and the head is usually provided with a 

 number of filaments analogous to the cirrhi of the feet, and 

 called antenna? and tentacular cirrhi (Fig. 527), which seem to 

 be organs of touch. The mouth is on the inferior aspect of 



* Feet of an Annelid of the genus Eunice : t, setigerous tubercle ; e, 

 dorsal cirrhus ; ci, inferior or ventral cirrhus ; b, branchia. 



t e, anterior part of the body j t, the head ; tr, proboscis ; b, buccal 

 opening ; m, jaws. 



