414 THE PHILOSOPHY 



teach them to refort to trees, and to infert their tongue^ in- 

 difcriminately into every hole or filTure. 



Ofthe oeconomy oiFiJJjesy as formely remarked, our know- 

 ledge is extremely limited. But, as the ocean exhibits a 

 perpetual and a general fcene of attack and defence, the 

 arts of afTault and of evafion muft, of courfe, be exceedingly 

 various. For the prefervation of fome fpecies of fiflies, Na-* 

 ture has armed them with ftrong and fharp pikes. Others, 

 as the perch-kind, are defended with ftrong bony rays in 

 their fins. Others, as the univalve fhell-fifh, retire into 

 their fhells upon the npproach of danger. The bivalves and 

 maltivalves, when attacked, inflantly fhut their fliells, which, 

 in general, is a fufficient prote(Slion to them. Some uni- 

 valves, as the limpet-kind, attach themfelves fo firmly, by 

 excluding the air, to rocks and ftones, that, unlefs quickly 

 furprifed, no force inferior to that of breaking the fliell can 

 remove them. The fiying-fifii, when purfued, darts out 

 of the water, and takes refuge in the air, in which it is for 

 fome time fupported by the operation of its large and pli- 

 able fins. The torpedo is furnilhed with a remarkable ap- 

 paratus for felf-prefervation : It repels every hoflile attempt 

 by an eledlrical flroke, which confounds and intimidates its 

 enemies. Several fifhes, and particularly the falmon kind, 

 when about to generate, leave the ocean, afcend the rivers, 

 depofit their eggs in the fand, and, after making a proper ;;/- 

 diis for their future progeny, return to the ocean from whence 

 they came. Others, as the herring-kind, though they fel- 

 dom go up rivers, afTemble in myriads from all quarters, and 

 approach the fhores, or afcend arms ofthe fea, for the pur- 

 pofe of propagating the fpecies, and cherifhing their off- 

 spring. "When that operation is performed, they leave the 

 coafts and difperfe in the ocean, till the fame inflindf ive im- 

 pulfe forces them to obferve a fimilar condudl next feafon^ 

 This migration of falmons, herrings, and many other fifhes, 

 from the ocean to the rivers or fhores, is of infinite advantage 



