CHAPTER XIV 

 THE NEMERTEANS 



BY WESLEY R. COE 



Sheffield Scientific School of Yale University 



AMONG the fresh-water animals of the northern half of the 

 United States occurs a slender little worm of a beautiful reddish 

 color belonging to the group of Nemerteans. These worms can be 

 easily distinguished from the other flatworms (Platyhelminthes) 

 by the slenderness of the body, and from the other groups of worms 

 by their perfectly smooth, ciliated bodies and their leisurely creep- 

 ing movements. The presence of the proboscis armed with a 

 formidable calcareous stylet which can be thrust out of the opening 

 at the anterior end of the body is proof that the worm is a ne- 

 mertean. 



These nemerteans live along the shores of lakes and streams, 

 as well as in pools and artificial basins of water and aquaria. Quiet, 

 shallow areas of water with a dense growth of water plants are 

 particularly favorable. The worms may be found creeping over 

 the stems and leaves of the water plants, among the dead 

 leaves and debris at the bottom, on stones and objects in the 

 water, and oftentimes beneath the stones along the shore. The 

 under sides of floating leaves, as lily pads, particularly those par- 

 tially decayed, often harbor numbers of these tiny worms. They 

 are, however, local in distribution and are seldom found in abun- 

 dance over a very wide area. When common in a shallow inlet a 

 few yards wide, a further search for a mile along the shore of a 

 lake or stream may fail to reveal a single specimen. 



The worms are usually from 10 to 18 mm. in length when fully 

 extended, but may contract to a small fraction of their former 

 length. They rarely exceed i mm. in diameter. The color varies 

 considerably, shades of red, orange, or vermilion being most com- 

 mon, while the smaller specimens are often pale yellowish or flesh 

 colored. The anterior half of the body is more brightly colored 



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