196 NATTJKAL HISTORY. 



ments, it measures a span in length, is about the size of 

 a quill in thickness, and has neither mandibles nor eyes. 

 Feeds on earth, mingled with decaying substances, comes 

 forth after midnight from holes in the ground, and is only 

 injurious as it attacks the fine roots of plants. It passes 

 the winter season deeply buried in the earth. Anglers 

 use it to bait their hooks. 



The Water Worms (gordius aquaticus) are a span 

 long and not thicker than a violin string. Live in 

 muddy places or standing water. 



The Leeches (hirudo medicinalis), plate 26, fig. 11, 

 are distinguished from other worms by the presence of 

 small teeth and in having the posterior extremity fur- 

 nished with a cup-like disk, adapted for suction. They 

 measure a finger in length, and are about two lines in 

 thickness ; black above, with eight yellow stripss, spotted 

 with the same color below. They live in ponds and 

 marshy brooks ; fastening on fish, they suck their blood. 

 Their method of moving is as follows : having stretched 

 themselves at full length upon the victim, they suck 

 themselves fast, thus having fixed their anterior extrem- 

 ity, they draw the other up to it and fix that, and then 

 readvance the first. They swim with great facility, 

 using a serpent-like motion, and are much esteemed in 

 medicine as useful instruments in local blood-letting. 

 They lay eggs, which they fasten on stones or water- 

 plants by a fibrous excretion. Those brought from Hun- 

 gary are considered the best. 



' The Horse Leech (hirudo gulo) has no stripes on the 

 back; greenish-black above, gray below. Their bite 

 causes large pustules in the skin. Several smaller spe- 

 cies are found in the East Indies, many of which are 

 dangerous, as inhabiting all the muddy ditches or stag- 



