' o^ 

 4 GENERAL ZOOLOGY 



Probably most readers have never heard of nematode 

 worms, yet Cobb in a paper on these animals says: 



"Not the least interesting thing about nematodes is the astounding 

 variety of their habitats. They occur in arid deserts, at the bottoms 

 of lakes and rivers, in the waters of hot springs and in polar seas where 

 the temperature is constantly below the freezing point of fresh water. 

 They were thawed out alive from Antarctic ice in the far south by mem- 

 bers of the Shackleton expedition. ... A thimbleful of mud from the 

 bottom of river or ocean may contain hundreds of specimens. The 

 nematodes from a 10-acre field, if arranged in single file, would form a 



FIG. 1. A nematode worm which lives on the roots of plants. Greatly mag- 

 nified. (From Cobb, Yearbook; U. S. Department of Agriculture, 1914.) 



procession long enough to reach around the world. A lump of soil no 

 larger than the end of one's thumb may contain hundreds, even thou- 

 sands of nematodes, and yet present few points that would distinguish it 

 from a lump of soil destitute of these organisms. ... In short, if all 

 other matter in the universe except the nematodes were swept away, 

 our world would still be dimly recognizable, and if, as disembodied 

 spirits, we could then investigate it, we should find its mountains, hills, 

 vales, rivers, lakes, and oceans represented by a film of nematodes. The 

 location of towns would be decipherable, since for every massing of 

 human beings there would be corresponding massing of certain nema- 

 todes. Trees would stand in ghostly rows representing our streets and 

 highways." 



Instances of this kind might be multiplied. There are 

 animals in the soil which even exceed the nematodes in 

 numbers. 



