CHAPTEE V. 

 THE BEISTLE-WOKMS. 



Different kinds of worms Nematodes Polychaetes External appear- 

 ance of Nereis Structure of the fisherman's lob-worm Habits 

 of worms Common shore worms The scale-worms, or Polynoids 

 The leaf-worms, or Phyllodocids. 



fT^HE group of " worms " is an exceedingly large one, and 

 _L includes a great number of forms not closely related to 

 one another. Many of these are, however, small or rare, 

 and need not trouble us here, so that we shall consider in 

 detail two sets only the ribbon-worms (Nemertea) and the 

 bristle-worms (Chaetopoda). Two other sets the round- 

 worms (Nematoda) and the sea-mats (Polyzoa) are almost 

 certain to be also encountered on the shore, and should be 

 briefly referred to. The Polyzoa will be discussed after 

 we have studied some more representative forms, but the 

 Nematodes may be dismissed in a few words. 



In turning over stones on the shore, in search of nobler 

 prey, one not infrequently comes across little white or 

 almost transparent worms, which move with an active 

 wriggling motion, and are rounded in cross section. They 

 are especially abundant in pools containing decaying organic 

 matter or odoriferous mud. These are round worms, or 

 Nematodes, harmless enough in this case, but nearly related 

 to some of the most dangerous parasites of man. Almost 

 always of this dead white tint, there is s- mething in their 

 very appearance which suggests their degraded and repulsive 

 mode of life. In spite, therefore, of the fact that they 

 exhibit many points of zoological interest, we may allow 

 our instincts to guide us in passing them by, especially as 

 their small size unfits them for our purposes. As these 



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