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Chapter VI. 



THE EARTHWOEM. Lumbricus terrestris. 



The earthworm lives in burrows in moist earth, through 

 which it makes its way by alternate elongation and contrac- 

 tion of its body, aided by small stiff setae projecting from its 

 surface. That part of the body most exposed to light is 

 dark ; the rest is almost colourless. 



It is a pinkish worm about six inches long, cylindrical in 

 front, flattened posteriorly. Its food consists of organic 

 matter derived chiefly from the soil, which it swallows in 

 enormous quantities. The worm is hermaphrodite, and lays 

 its eggs in a chitinous cocoon, which also contains packets of 

 spermatozoa and an albuminous fluid. 



The body is marked by transverse grooves dividing it into 

 annuli, of which there are about one hundred and fifty. This 

 external annulation corresponds with an internal segmenta- 

 tion, the body-cavity being divided into chambers by trans- 

 verse septa, which are placed opposite the external grooves. 

 Nearly all the organs exhibit a corresponding segmental 

 arrangement, there being one pair of nephridia and one 

 nerve-ganglion in each segment or somite throughout the 

 greater part of the animal's length, the blood-vessels, muscles 

 and setae being also disposed segmentally. 



Two closely allied genera of large earthworms, Lumbricus 

 and Allolobophora, occur commonly in this country, each 

 represented by several species. 



The several species differ from each other in the position 

 and arrangement of certain of the reproductive organs, and 

 in other minor points. The following description, taken from 



