OF THE ANNELIDES. 



455 



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

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

 body (Fig. 335) ; 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. 439); 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 con- 

 tact. In the annelides, which have 

 no bristles, there exist at the extre- 

 mities 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 

 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 antennae and tentacular cirrhi (Fig. 441), which seem to 



Fig. 439.' 



Fig. 440. Head and Proboscis 

 of a Glycera.f 



Fig. 441. Head, &e., 

 of a Nereis. 



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

 the head, or the anterior extremity of the body, when the^e 

 is no distinct head ; it is often armed with a protractile pro- 

 boscis (Fig. 440), and with jaws having the form of hornv 

 hooks. The intestine is straight, simple, or furnished with 



ibercle; e, 

 buccal 



* Feet of an Annelid of the genus Eunice: t, setigerous tub* 

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



t c, anterior part of the body ; t, the head ; tr, proboscis ; b, 

 onpnina : in. iaws. 



opening ; m, jaws. 



