ABRANCHIATA. 371 



fermentation, and consequently sterile : and besides, 

 in favour of Worms, it should be hinted, that green 

 corn, plants, and flowers, are not so much injured by 

 them, as by many species of Beetles, and Tipulce, in 

 their larva or grub state ; and by unnoticed myriads 

 of small shell-less snails, called slugs, which silently 

 and imperceptibly make amazing havoc in the field 

 and garden."* 



In a very interesting paper, read before the Geo- 

 logical Society, by C. Darwin, Esq., it is satisfac- 

 torily shewn, that Earth-worms are most valuable 

 agents in fertilizing lands, especially in undisturbed 

 pastures, gradually covering the surface with their 

 casts, and thus forming a layer of finely pulverized 

 earth of the richest character. A field which had 

 been limed, was examined after about eighty years, 

 when the lime was found to be evenly covered to the 

 depth of thirteen inches, with this animal mould, f 



The motion of the Worm along the ground is 

 curious. It is performed thus : the head and fore 

 rings of the body are stretched forward and consider- 

 ably lengthened ; . then the bristles of these parts, 

 of which there are four pairs on the under side of 

 every ring, are thrust out, and, being strongly pressed 

 against the ground, take a firm hold, while the 

 body is forcibly contracted ; the hind parts, being 

 alone at liberty, are of course drawn forward, when 

 the bristles of these rings being in their turn pressed 

 against the ground, afford a resistance, by means of 



* Nat. Hist. Selb. p. 231. (Ed. Soc. Pr. Ch. Kn.) 

 t Proceed. Geol. Soc. vol. ii. 



