THE I.YTHOPHYTES AND SPONGES. 427 



that the shell of the snail grows round it ; these little reptiles 

 are each possessed of a slimy matter, which covers its body, and 

 this hardening, as in the snail, becomes a habitation exactly fitted 

 to the body of the animal that is to reside in it ; several of these 

 habitations being joined together, form at length a considerable 

 mass ; and as most animals are productive in proportion to their 

 minuteness, so these multiplying in a surprising degree, at length 

 form those extensive forests that cover the bottom of the deep. 



Thus all nature seems replete with life ; almost every plant 

 on land has its surface covered with millions of these minute 

 creatures, of whose existence we are certain, but of whose uses 

 we are entirely ignorant; while numbers of what seem plants at 

 sea, are not only the receptacles of insects, but also entirely of 

 insect formation. This might have led some late philosophers 

 into an opinion, that all nature was animated ; that every, even 

 the most inert, mass of matter was endued with life and sensa- 

 tion, but wanted organs to make those sensations perceptible to 

 the observer : those opinions, taken up at random, are difficultly 

 maintained, and as difficultly refuted ; like combatants that meet 

 in the dark, each party may deal a thousand blows without ever 

 reaching the adversary. Those, perhaps, are wiser who view 

 nature as she offers ; who, without searching too deeply into the 

 recesses into which she ultimately hides, are contented to take 

 her as she presents herself; and storing their minds with effects 

 rather than with causes, instead of the embarrassments of sys- 

 tems, about which few agree, are contented with the history 

 of appearances, concerning which all mankind have but one 

 opinion. 



