I20 ANNELIDA OR ANNUL AT A 



three Inches deep In twenty years. Eighteen tons of earth were 

 brought to the surface In one acre. 



{b) Earthworms have been and probably are still used by some 

 savages as food. 



{c) Earthworms and marine annelids are used as fish bait. 



Negative. — {a) Earthworms may be of slight injury in green- 

 house soils. 



{b) Earthworms are accidentally Intermediate hosts in the trans- 

 mission of the gape-worm, Syngaynus trachealis. It is not necessary 

 to the life of the parasite that it be taken in by the earthworm. 



{c) Certain medical men have from time to time suggested that 

 the earthworm may be important in transmitting cancer through 

 the deposition of the organism in feces transferred to vegetables by 

 the earthworm. This is purely conjectural. 



Economic Importance of the Leech 



Positive. — (a) In cases of hemophilia (persistent bleeding) and 

 after contusions, physicians and veterinarians still use leeches to 

 extract blood. Some drug stores keep a supply of leeches on hand 

 In the spring to serve the needs of those foreigners who get black 

 eyes at weddings and other celebrations. The doctor of the Middle 

 Ages was called the " leech." 



(b) Leeches are said to have been used for food by some savages. 



Negative. — Leeches parasitize some aquatic and amphibious 

 forms. 



