CHAPTER XIV. 



THE EARTHWORM. 



THE body of the earthworm (Lumbricus) is long and ringed. 

 The rings indicate a division into segments or somites, of which 

 there may be as many as 350. There is no distinct head or 

 neck, but the anterior end tapers off, while the posterior end 

 terminates bluntly. There are no definite limbs or appendages, 

 but nearly each segment is provided with chitinous bristles which 

 aid it in progression, which is effected by alternate elongation 

 and shortening of the body. The worm lives in moist earth, in 

 which it forms burrows. It is omnivorous, swallows much earth. 

 and normally consumes vegetal matter, such as leaves, fresh or 

 half-decayed. It will, however, eat animal food, and at a pinch 

 a dead comrade. Its power of regenerating excised parts is very 

 remarkable. It is stated but hard to believe, that a worm not 

 only survived the removal of the first five rings, including 

 the brain, sub-cesophageal ganglion, mouth, and pharynx, but, 

 within fifty-eight days, had completely regenerated these parts. 



In the young worm, not yet sexually mature, the rings 

 throughout the body are tolerably similar, those at the anterior 

 end gradually lessening in diameter, and those at the posterior 

 end becoming somewhat flattened, In the adult worm, however, 

 certain of the rings between the twenty-fourth and thirty-sixth 

 become lighter in colour, much swollen, and coalescent dor- 

 sally, and project downwards as ridges on either side of the 

 mid-ventral line, giving rise to the cingulum or ditellum. The 

 ventral aspect of segments eight to twelve also becomes swollen 

 and tumid. 



The mouth is in the anterior segment, situated beneath a 



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