336 FUNCTIONS AND INSTINCTS. 



they swim like eels with a vermicular motion. 

 In moving on a solid body, they first fix them- 

 selves by their anal sucker, which is larger than 

 the oral, and then by means of their annular 

 structure, extend themselves forwards, when they 

 fix their mouth, detach their anal sucker, 

 and thus fixing themselves alternately by each 

 proceed with considerable rapidity. They are 

 hermaphrodites, and bring forth their young 

 alive. When in their native waters they suck 

 any animal that comes in their way, even those 

 with white blood, as the larvaB of insects, worms, 

 and the like. 



Herodotus relates that the crocodile, in con- 

 sequence of its frequenting the water so much, 

 has the inside of its mouth infested by leeches, 

 which a little bird, named the trochilus, enters 

 and devours, without receiving any injury from 

 the monster. Geoffroy St. Hilaire asserts that 

 no leeches are found in the Nile, and therefore 

 supposes the Udellce of the father of history 

 were not leeches but mosquitoes. But Savigny 

 has described a leech under the name of Bdella 

 nilotica 1 which he regards as synonymous with 

 the leech of Herodotus. Bosc mentions one 

 which was found in the stagnant waters 

 in Egypt, when not inflated as small as a 

 horse hair, which very much annoyed the 



1 PLATE VIII. FIG. 3. 



