III.] THE EARTHWORM. 24I 



at least two lesser divisions or zonites, these however are but 

 skin deep and in no way correlated with the internal parts. 

 The body is invested in a continuous uncalcified exoskeleton 

 in the form of a delicate iridescent cuticle. No limbs of 

 any sort are present, and locomotion is effected by means of 

 four longitudinal series of bristle-like set(E, which project 

 freely from all but some few of the anterior segments j a 

 powerful muscular apparatus is developed in connection 

 with each of these, and the chitinous setae themselves are 

 largely buried in tegumental sacs lined by cuticular invo- 

 lutions. The setae are replaced when cast off. 



The posterior terminal segments of the body are, during 

 life, flattened from above downwards, and when the animal 

 on removal from its burrow is observed crawling, a charac- 

 teristic spatulate appearance is imparted to that region, at 

 the upturned end of which the anus is situated. Under 

 ordinary circumstances the worm, on coming to the surface, 

 retains its hold on its burrow by means of this expanded 

 extremity. 



The Earthworm is omnivorous, living mainly upon leaves 

 (for certain kinds of which it has a decided preference), and 

 less conspicuously upon both animal and vegetable organ- 

 isms ingested with the earth passed through its alimentary 

 canal, in burrowing or otherwise. The alimentary canal is 

 a straight tube, running the entire length of the body. The 

 mouth leads into a thin-walled eversible buccal sac, which 

 opens into a spacious muscular suctorial pharynx ; this, in 

 turn, passes into a long tubular oesophagus, the terminal 

 fifth of which is enlarged to form a distensible crop. The 

 crop is, in the common earthworm, succeeded by a whitish 

 thick-walled gizzard, so called as it performs a mechanical 

 crushing action. This finally opens into a long sacculated 

 intestine, which is continued on with but slight modification 



M. 16 



