CHAPTER V 



ANNELIDA 



Phylum TROCHOZOA 



Sub-Phylum ARTICULATA 

 Division ANNELIDA 



Types 



Class OLIGOCHAETA . . Lumbricus 

 HIRUDINEA 

 POLYCHAETA . . Nereis 



THE Annelida include the earthworms (Oligochaeta), the 

 leeches (Himdinea), and the bristle worms of the sea (Poly- 

 chaeta). 



The Oligochaeta occur everywhere on land, many are 

 found in fresh water, and a few have obtained a lodgment 

 in the sea near the shore. 



Lumbricus. The common earthworm is Lumbricus terrestris. 

 It is common in England and Europe, and nearly allied species 

 and genera are found everywhere. The quantity to be obtained 

 varies with the nature and condition of the soil, but in the soil 

 of lawns, pastures and the like, they are usually present in 

 large numbers. A rough count has shown that over fifty may 

 be found in an area of a square yard. They are therefore of 

 interest to the agriculturist as to the geologist for the share 

 they take in soil formation. The soil is eaten and passed 

 through the alimentary canal, the decaying vegetable matter 

 serving as food, and the residue treated in this way is discharged 

 either below or above ground, above as ' worm casts.' The 

 underlying soil is thus gradually channelled, stirred up, aerated, 

 and brought to the surface ; and when the large numbers of the 

 worms are considered and their long history taken into account 



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