DIVISION OR TYPE IV. : WORMS (VERMES). 



BILATEEALLY symmetrical animals without articulated limbs, and with 

 the body invested by a dermo-muscular tube (see earth-worm). 



CLASS I. SEGMENTED WORMS (ANNELIDA). 



BODY divided into a large number of similar rings, or segments. 



ORDER I. : BRISTLE- WORMS (CH^ETOPODA). 



The Earth- Worm (Lumbricus terrestris).* 

 (Length up to 12 inches.) 



A. Body Covering. 



THE body of the earth-worm is invested in a soft and naked skin, 

 which therefore, like that of the vineyard snail (see p. 429), is always 

 covered with a slimy fluid. Hence, like the snail, the earth-worm can 

 only exist in a damp atmosphere. For this reason, in the daytime it 

 only cdmes to the surface when the weather is dull, and at night when 

 there is dew ; but it is specially abundant during rainy weather. At 

 other times the animal remains in concealment in the damp soil, and 

 hence it is never met with in a dry, sandy soil (see also Section F). 



B. Respiration. 



If, while a garden is being dug up, an earth-worm happens to get 

 upon a firmly trodden path, so that it is unable to burrow its way into 

 the soil again, it soon perishes, for, owing to the great loss of moisture, 

 its respiration, which is carried on by the whole delicate and moist 

 surface of the body (see Part II., p. 274, Section D) is soon arrested. 



C. Form of Body. 



The body of the earth-worm is much elongated. Hence the tubular, 

 mostly vertical passages which it burrows underground are of no great 



* This Linnsean species is now subdivided into several separate species. 



