HUMUS 23 



are interested in the function and work of the earthworms rather 

 than in a study of the animal from a zoological standpoint. 



While many hundreds of species, including marine worms, 

 are comprised in the order Phylum annelida, our interest centers 

 in the \_Oligochaeta jand that portion known to science as the 

 "small-bristled ringed worm." They are distributed all over the 

 planet, including the islands of the sea, from the tropics to ex- 

 treme northern and southern latitudes, except in the arctic and 

 sub-arctic regions and glacial and sub-glacial regions where the 

 ground may be frozen to great depths over long periods of time. 



In size, earthworms range all the way from small worms of 

 almost microscopic dimensions to giant annelids measuring from 

 three feet to eleven feet long. The large members of the family 

 are found in certain parts of South America, Africa, Ceylon and 

 Australia. The largest of the giant worms, Megascolides Austra- 

 lis, is found in Australia, where authentic measurements of worms 

 up to eleven feet in length have been made. 



In the torrid and temperate zones more than one thousand 

 ^eciej of earthworms (some authorities say more than 1800) 

 live and procreate. Whatever the name, size, or habitat, earth- 

 worms have one important characteristic in common they swal- 

 low the earth with all that it contains, and in the process of di- 

 gestion and elimination excrete practically neutral humus top- 

 soil rich in water-soluble nutrients for plant life. 



Narrowing the field down still more to the particular pur- 

 pose of this inquiry, we are interested in the group of earthworms 

 common to the United States and known under various popular 

 and colloquial names, such as "angleworms," "dewworms," "night 

 crawlers," "night lions," "fishworms," "rainworms," etc. The 

 last name, "regenwurm," is very generally used in the extensive 

 German literature on the subject. 



For practical purposes and for reasons given later, we shall 

 eliminate from consideration all worms except the 

 (Lumbricus terrestris), illustrated in Fig. 1, and thefBranHTu 



