454 The Animal Kingdom 



ated posterior part of the body. During the last quarter of the October- 

 November moon, this part of the body with its contained eggs or sperm 

 breaks off and swarms to the surface for a period of two to three days. 

 At that time, the water is clouded with the masses of sperm and eggs. 

 The people of these islands go out in boats and gather this caviar in 

 great quantities. A similar species (Leodice furcata) which lives in the 

 Gulf of Mexico has similar swarming habits in June and July. 



d;^;',-rs 





Fig. 146. — Some polychaetes. a, Sabella, the peacock worm; b, Neanthes, the 

 clamworm; c, Chaetopterus, a tube dweller; d, Amphitrite; e, Eunice viridis, the 

 palolo worm; /, Bispira, the fan worm; g, Aphrodite, the sea mouse. 



One intertidal form, Chaetopterus, lives in a U-shaped tube. Its 

 parapodia are highly modified : some are fanlike to facilitate the move- 

 ment of water through the tube, others form food into food balls. This 

 latter is made possible by mucus secreted in strings from anterior glands. 

 These catch the food which is being pumped through the tube, and the 

 modified parapodia form these slimy strings into food balls which are 

 then passed forward to the mouth. 



Other tube-dwelling polychaetes have nuilticolored gills and tentacles 

 which protrude from the tube and open into flowerlike structures. 



THE CLASS OLIGOCHAETA 



The members of the class Oligochaeta are chiefly terrestrial and 

 fresh-water forms. Most species have only a few setae in place of the 

 large number found on the parapodia of the polychaetes. In the main, 

 the fresh-water forms are small, sometimes being only a few millimeters 



