66 ANNELIDANS. 



to some depth, and the blood thus liberated is largely sucked into the capacious sto- 

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

 animals; they attach themselves to fishes and frogs; sometimes they devour mollusks, 

 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 con- 

 tents. 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 quantities from Spain and Russia. They may be preserved for a long time by 

 placing them in moist earth or mud. On the approach of cold weather they bury them- 

 selves at the bottom of ponds, and pass the winter in lethargy, but they regain their 

 activity in spring. 



FIG. Ci. -LuLOONS OF LEF.CH. 



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 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. 



SECOND ORDER DORSIBRANCHIATE ANNELIDANS. 



In the Dorsibranchiate Armelidans the respiratory organs 

 consist of fringes or arborescent tufts, distributed in pairs along 

 the sides of the back. In some cases, every ring is thus furnished, 

 but in others, only those rings which are near the middle. These 

 worms are all free : they burrow in the mud or sand, or swim in 

 the open sea ; they are therefore supplied with organs of loco- 

 motion, which, for the most part, assume the form of moveable 

 spines or packets of retractile bristles attached to each segment 

 of the body. 



It is not, however, by mere prosy description that we can convey 

 to our readers any adequate idea of the beauty of these splendid 

 worms ; here we must let their great historian, M. de Quatrefages, 



