52 



ZOOLOGY. 



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

 worm" is Nereis virens (Fig. 5C). 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- 



FiQ. 55. —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, 5G.— Transverse section throug:h tlie liiody of a Nereis, d, dorsal vessel or 

 lieart; c', circular hi ood- vessel ; /(, ventral vessel; ?i. nervous cord or tranf^Iia; 

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

 bull, from Emertou. 



and seizing its prey witli its two hirge 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. 



