POLYPES. 175 



rocks, has not been ascertained. As in the case 

 of a vast variety of other marine animals, they 

 probably derive their nutriment from the contents 

 of the water absorbed by their tubes ; they may 

 contribute their part to the depuration of the 

 oceanic waters, and to the maintenance of the 

 equilibrium amongst their inhabitants, however 

 minute, which is necessary to the general welfare. 

 Doubtless, in their creation, He, who inhabiteth 

 Eternity, to whose view all time as well as all 

 space is present, had in view the benefit of his 

 creature man, to whom they form a very useful 

 present, and which he has long applied to his pur- 

 poses. Sponges were in use as early as Aristotle's 

 time, when the people that employed themselves 

 in collecting them observed, that when they 

 attempted to pluck them up they appeared to 

 resist, whence they concluded they had some 

 sensation. 1 They now form a very considerable 

 article of commerce. The fishery for them is 

 chiefly carried on in the Mediterranean, particu- 

 larly in the Grecian Archipelago. The collection 

 of them is attended with danger, as they are 

 fixed to the rocks at the depth of several 

 fathoms, so that the sponge-fishers must be excel- 

 lent divers. Tournefort says, that no youth in 

 these islands is allowed to marry, till he has 

 given proofs of his capacity in this respect. 



1 Aristot. Hist. Anim. B. i. c. 1, comp. B. v. c. 16. 



