ANATOMY OP NEREIS VlRENS. 



231 



lands, bringing the subsoil to the surface and allowing the 

 air to get to the roots of plants, they occasionally injure 

 young seedling cabbage, lettuce, beets, etc., drawing them 

 during the night into their holes, or uprooting them. 



The next and highest type of Annulata is the common 

 sea-worm of our coast, Nereis virens Sars. It lives between 

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

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

 feet have been carefully studied, can be opened along the 

 back by a pair of fine scissors and the dorsal and ventral red 

 blood-vessels with their connecting branches observed, as 

 well as the alimentary canal and the nervous system. 



The anatomy of this worm has been described by Mr. F. 

 M. Turnbull. It is very voracious, thrusting out its pharynx 

 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 and 

 liguke. At night, 

 probably during the 

 breeding season, 

 they leave their 

 holes, swimming on 

 the surface of the 

 water. 



The body consists 

 of from one hundred 

 to two hundred seg- 

 ments. The head 

 consists of two seg- 

 ments, the anterior 

 and buccal, the for- 

 mer Avith four eyes 

 and two pairs of 

 antennas. The sec- 

 ond segment bears 

 four antennae (tentacular cirri). Each of the other segments 

 bears a pair of paddle-like appendages (rami), w^hich may be 

 best studied by examining one of the middle segments which 



Fig. 152. Vertical section through the integiiment 

 of an Annelid (Spheerodorum). c, thick ctiticular 

 layer with the pore-canals ; m, muscular layer ; m', 

 muscles of the bristles, g, which retract the central 

 foot-lobe, while others pass to its dorsal glandular 

 projection, d. After Gegenbaur. 



