CHAPTER XVI 

 THE EARTHWORM 



I guess the pussy-willows now 

 Are creeping out on every bough 



Along the brook ; and robins look 

 For early worms behind the plough. 



HENRY VAN DYKE, An Angler's Wish. 



Habitat and Distribution. The animal which is the subject 

 of this chapter is distributed widely throughout the world. 

 The more familiar species live in the soil, where their burrows 

 extend obliquely downward, sometimes many feet. One rather 

 common species, Alloloboph' ora fce'tida, marked by red and 

 dark bands of color, lives in manure heaps. When irritated 

 it gives off an offensive odor, whence its specific name. The 

 species best known in America is Lumbri'cus terres'tris. It is 

 found in small cylindrical burrows, which it makes in the soil 

 wherever it is not too dry or too sandy. In spite of the usual 

 habit of living in the earth, these animals can live for many 

 days in a body of water without great discomfort. Repre- 

 sentatives of the many species and the few genera of earth- 

 worms are found in practically all places from Arctic to 

 Antarctic regions, including isolated oceanic islands. 



External Structure. T - external structure the body of the 

 earthworm is very simple. The anterior end is slender and 

 pointed when extended in life, and the posterior region is 

 flattened above as well as below. The somites of the anterior 

 region differ also from those in the posterior region in being 

 longer. There is no head, no thorax, and no abdomen. There 

 are no appendages except bristles, almost microscopic in size, 

 which occur in rows on the ventral surface of every somite 



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