Worms. 



FIG. 44. 



which the lug-bait or the hairy-bait of fishermen may 

 be taken as representatives. These worms have 

 bodies made up of a succession 

 of similar segments, each of which 

 bears on each side a lateral pro- 

 cess or parapodium, divided at 

 its extremity into a dorsal and a 

 ventral bristle-bearing eminence. 

 These are the organs of locomo- 

 tion. The bristles vary much in 

 form, being sometimes shield-like 

 and always are developed in 

 pouches of the skin and capable 

 of being moved by dermal mus- 

 cles : these processes are known 

 as dorsal and ventral oars. The 

 mouth is on the second segment, 

 and is often armed with sharp 

 teeth. The intestine is usually 

 straight and very often has 

 lateral glandular pouches ap- 

 pended to it. There is a vas- 

 cular system consisting of long 

 tubes, dorsal, ventral, and late- 

 ral, generally joined by cross 

 branches in each joint, and 

 containing red, green or white 

 blood. The gills, when present, 

 are usually arranged along the 

 dorsal surface of the body, close 

 to the root of the dorsal oar, 



Arenicola piscatorum. 



Lug-bait worm. Dorsal sur- 



face showing the dorsal 



oars (notopodia) and gills. 



and in these the 



blood is purified by being exposed to the oxygen 



