110 WORMS, MOSS-POLrPS, SPONGES, ETC. 



resemble flattened snails. They are the circular 

 tubes of a worm, Spirorbis, whose relationship is 

 immediately with the Serpulse. 



Of the group of worms in which the body is not 

 distinctly annulated, known as false annelids, may 

 be mentioned the earthworm-like Sipunculus (PI. 8, 

 Fig. 2), which can be easily recognized by its thick, 

 fleshy, and irregularly constricted body, and by the 

 long attenuated anterior extremity, designated the 

 proboscis. It burrows in the sand and mud-bot- 

 toms, like the majority of the marine worms. 



The free surface of the wide ocean, no less than 

 the sheltered bays of the seaboard, harbors a very 

 interesting worm-like animal, about an inch in 

 length, and shaped somewhat like a lance, which 

 disports itself in rather characteristic fashion, mov- 

 ing by rapid jerks through the water. It has long 

 been familiar to naturalists as the Sagitta, or dart 

 (PI. 8, Fig. 5), but to this day nothing positive is 

 known concerning its relationships. The body is 

 white, translucent, and permits the alimentary canal 

 to be distinctly seen in the interior. Laterally it is ex- 

 panded into a sort of fin-like membrane, and a some- 

 what similar fin rounds oflF the tail region. Two dark 

 pigment specks, the eyes, can be readily detected on 

 the head. 



MOSS-POLYPS. 



Much of the sea-wrack that is drifted to our 

 shores shows on its surface peculiar pitted incrus- 

 tations which sometimes occur only in scattered 

 patches, at other times in more or less continu- 

 ous ramifications. The same structure can fre- 



