170 THE HARMONIES OF NATURE. 



they chiefly subsist, but also the quadrupeds horses, cattle, wild 

 animals that come to slake their thirst or to bathe in the pools 

 which they infest. But they, in their turn, have to encounter a 

 host of enemies : the large water-beetles and their larvae destroy 

 them by myriads; several of the fishes esteem them as dainty 

 morsels, and numerous water-birds and waders rejoice in their 

 capture. 



While the land-leech besets the traveller in the rising grounds 

 of Ceylon, or on the lower slopes of the Himalaya, and is detested 

 as the greatest plague to be encountered in the humid forests, 

 the medicinal leech of Europe renders, as is well known, such 

 signal services as a remedial agent in inflammatory diseases, 

 that millions are annually used. This vast consumption has 

 already exhausted numerous lakes and ponds, in which it for- 

 merly abounded ; so that while a few years since the hospitals 

 of Germany, France, and Grreat Britain drew their chief supply 

 from the Hungarian marshes, they now receive their leeches 

 from the lagunes of the Volga and the Don. 



On the dry land the chief representatives of the annelides 

 are the earthworms, which, piercing and traversing the ground 

 in every direction, subsist on roots, woody fibres, animal matter, 

 and other organised substances. Though small and despised 

 creatures, the part they perform in the operations of Nature is 

 highly important ; for insinuating their pointed head between 

 the particles of the earth like a wedge, and then drawing for- 

 wards the hinder parts by a shortening of the body, they forcibly 

 dilate the passage into which the head has been already thrust, 

 and thus by" the united labours of myriads the earth is light- 

 ened, and vegetation thereby wonderfully assisted. 



Thus the obscure earthworm renders indirectly considerable 

 services to man, and giving a kind of under-tillage to the land, 

 performs below ground the same office that the spade performs for 

 the garden, and the plough for arable land. Compared with the 

 marine annelides, the organization of the earthworm seems but 

 rude and imperfect, as it has neither the numerous feet of the 

 elegantly-swimming nereids, nor the magnificent crown of the 

 serpulaB, and occupies about the same rank as the lob-worm, 

 so common on our coasts, where it is dug for by the fishermen 

 as bait. Along the rings of the middle part of the lob-worm's 

 body are gills of an arborescent form, corresponding with the 



