ANNELIDA. 



The tribe of leeches is very numerous ; they all feed at the expense 

 of other animals ; they attach themselves to fishes and frogs ; some- 

 times they devour molluscs, worms, or the larvae of insects. Few 

 animal substances are rejected ; all kinds of fish, dead or alive, 

 seem acceptable. Entering the larger fresh-water shells, the leech 

 takes up its abode, an uninvited visitor, and remains until it has 

 emptied them of their contents. They even devour other leeches. 

 Sir J. Dalyell saw one half swallowed by a horse-leech scarcely 

 double its size, and still struggling for liberty; but its ferocious 

 enemy, adhering firmly by its sucker, 

 and undulating its body in the water 

 as if to aid deglutition, occupied 

 three hours in finishing its meal. 

 The use of the medicinal leeches is 

 so general that they have become 

 an important article of commerce, 

 and are procured in great quan- 

 tities from Spain and Eussia. They 

 may be preserved for a long time 

 by placing them in moist earth or 

 mud. On the approach of cold 



weather they bury themselves at the 60 ^ TOOTH OF LEECH MAGXIFIED . 

 bottom of ponds, and pass the winter 

 in lethargy, but they regain their activity in spring. 



When kept in large reservoirs with clay-banks fringed with 

 rushes and aquatic plants, the leech will propagate its kind. It 

 lays about a dozen eggs, enclosed in a mucous cocoon of an oval 

 form, about a quarter of an inch long. In the month of August 

 holes may be observed in the mud or clay of the banks, each of 



FlG. 61. COCOOXS OF LEECH. 



which contains a cocoon. The eggs are hatched in about a week, 

 but it is three weeks before the young leave their slimy cradle ; during 

 the interval the cocoon has become considerably distended, and the 

 little animals are continually pushing its walls with their heads as if 

 trying to find a weak point and escape. When at last their 

 increasing strength enables them to burst forth, they are about a 

 quarter of an inch long, and no thicker than a thread. 



