26 EAKTHWORMS AND LEECHES [CH. I 



earthworms be held responsible for our valleys and hills 

 and all the softer features of our scenery. 



Leeches. 



Leeches are flattened worms that may be regarded as 

 more or less degenerate relatives of earthworms. The 

 body is segmented, and each segment is further divided 

 externally into smaller annuli. In the Hirudinidce there 

 are five annuli per segment except at the extremities. 

 All our British species live in fresh water and are very 

 reluctant to leave it, but in India and Ceylon and elsewhere 

 leeches are found living on land among vegetation and 

 capable of travelling at a fair rate in pursuit of animal 

 blood. 



In the United States leeches are bred for surgical pur- 

 poses. At Newton, Long Island, there is, or was, a leech 

 farm of some 13 acres extent. The farm consists of oblong 

 ponds of about 1^ acres each and 3 feet or so deep. The 

 bottom is covered with clay and the banks made of peat. 

 The eggs are deposited in the peat from June onwards 

 through the warm weather. The adults are fed once 

 every six months on fresh blood placed in linen bags 

 suspended in the water. The most destructive enemies 

 are rats, which dig the cocoons out of the peat. 



Locomotion. When in the water a leech either pro- 

 gresses by holding on to some surface by the anterior and 

 posterior suckers alternately and looping its body after 

 the fashion of a geometer caterpillar ; or casting itself free 

 from all attachment, both elongating and flattening its 



