SOME AQUATIC WORMS, ETC. 209 



rather less than an inch long, one-twelfth of an inch 

 wide, and .presenting the peculiar color mentioned in 

 the Key. Its movements are very slow. 



The podal spines are slightly curved, but not forked 

 at the ends. They are arranged in clusters of four 

 spines each, the clusters forming two rows, one on 

 each side of the body. 



The oesophagus is long and remarkably muscular. 

 It is surrounded and somewhat obscured by a pair of 

 large glands, and has near its posterior extremity two 

 large appendages similar in structure to the oesophagus 

 itself. 



The blood is yellowish-red. The dorsal vessel, at 

 some distance behind the front end of the body, 

 divides into three branches, which pass forward, and 

 near the anterior border unite by means of a network 

 of fine tubules. The worm has four hearts, two on 

 each side of the dorsal vessel, one pair being near the 

 eighth, and one pair near the ninth cluster of podal 

 spines. The dorsal vessel divides in front of the first 

 pair of hearts. The ventral blood-vessel is forked, 

 but with only two branches. 



10. . TtJBIFEX. 



A common and, in some places, very abundant little 

 worm, measuring from one-half to one and one-half 

 inches in length. The body is thread-like in its 

 narrowness, transparent and colorless, although the 

 bright crimson blood gives it a hue so vivid to the 

 naked eye that, where the worms are numerous, it 

 often seems to tinge the mud in which they live. 

 They- are seldom found free-swimming, but live a 

 comparatively sedentary life, with about one-half of 



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