62 



ZOOLOGY. 



Our commonest sea-worm, sometimes called the "clam- 

 worm" is Nereis virens (Fig. 68). It lives between tide- 

 marks in holes in the mud, and can be readily obtained. 

 The body, after the head, eyes, tentacles, and bristle-bear- 



Fia. 67 — Clymenella torquata, natural size. 



ing feet have been carefully studied, can be opened along 

 the back by a pair of fine scissors and the dorsal and ven- 

 tral red blood-vessels with their connecting branches ob- 

 served, as well as the alimentary canal and the nervous 

 system. 



This worm is very voracious, thrusting out its pharynx 



Fig. 68.— Transverse section through the body of a Nereis, d, dorsal vessel or 

 heart; c', circular blood-vessel; h, ventral vessel; n, nervous cord or ganglia; 

 /, artery to swimming foot s"\ i, intestine; s, setse or bristles. After Turn- 

 bull, from Emerton. 



and seizing its prey with its two large pharyngeal teeth. 

 It secretes a viscid fluid lining its hole, up which it moves, 

 pushing itself along by its bristles. At night it leaves 

 its hole, swimming on the surface of the water. 



