110 WORMS, MOSS-POLYPS, SPONGES, ETC. 
resemble flattened snails. They are the circular 
tubes of a worm, Spirorbis, whose relationship is 
immediately with the Serpule. 
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 
(Pl. 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 asort of fin-like membrane, and a some- 
what similar fin rounds off 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- 
