CHAPTER III. 



THE EARTHWORM (LUMBRICUS AND ALLOLOBOPHORA, 

 VARIOUS SPECIES). 



In dissecting the Earthworm, the beginner will often find 

 slight discrepancies between the descriptions in the book which 

 he uses as a guide and the actual facts of structure before him. 

 This is owing to the existence of a considerable number of 

 different species of earthworms which offer a certain amount 

 of structural differences among themselves. 



In this country there exist, so far as is known, some twenty 

 species. They are all of small to moderate size, and live in 

 soil, though not impatient of even prolonged immersion in 

 fresh water. They burrow through the earth, swallowing the soil 

 as they go, which is often — after extraction of some, at any 

 rate, of the nutritive substance which it contains — evacuated to 

 form the well-known castings so abundant upon lawns after 

 rain. A certain amount of moisture is necessary for the soft- 

 bodied animals to live, and in very dry weather the worms 

 penetrate deeper into the ground, and often coil themselves 

 into chambers below the surface and surround themselves with 

 a coating of exuded mucus. 



An earthworm is a soft-bodied animal, obviously segmented, 

 i.e. the body is divided by superficial furrows into a series of 

 similar rings, segments, or somites, as they are variously termed. 

 A closer examination shows that there are other external 

 features which are also arranged in the same " metameric " 

 fashion. If a worm be held in the hand and passed between 

 the finger and thumb of the other hand, it produces a sensation 

 of roughness, which is caused by the implantation of the 



