140 THE PHILOSOPHY 



enemy approaches, they inftantly fliut their ftiells, plunge to the 

 bottom, and the whole fleet difappears. By what means they ara 

 enabled to regain the furface, we are flill ignorant. 



With regard to the locomotive faculty of the oyfter, the follow- 

 ing fa(3:s are recorded in the yournal de Phyjique by the Abbe Dic- 

 quemare. Like many other bivalved fliell-fifh, the oyfter has the 

 power of fquirting out water with a confiderable force. By thus 

 fuddenly and forcibly ejeding a quantity of water, the animal re- 

 pulfes fuch enemies as endeavour to infmuate into its (hell while 

 open. By the fame operation, if not firmly attached to rocks, to 

 ftones, or to one another, the oyfter retreats backwards, or ftarts to 

 a fide in a lateral diredion. Any perfon may amufe himfelf with 

 the fquirting and motions of oyfters, by putting them in a plate fi- 

 tuated in a horizontal pofition, and which contains as much fea- 

 water as is fufficient to cover them. The oyfter has been reprefent- 

 ed by many authors as an animal deftitute not only of motion, but 

 of every fpecies of fenfation. The Abbe Dicquemare, however, 

 has fhown, that it can perform movements perfectly confonant to 

 its wants, to the dangers it apprehends, and to the enemies by which 

 it is attacked. Inftead of being deftitute of all fenfation, oyfters are 

 capable of deriving knowledge from experience. When removed 

 from fituations which are conftantly covered with the fea, devoid 

 ©f experience, they open their fliells, lofe their water, and die in a 

 few days. But, even when taken from fimilar fituations, and laid 

 down in places from which the fea occafionally retires, they feel the 

 effedls of the fun's rays, or of the cold air, or perhaps apprehend 

 the attacks of enemies, and accordingly learn to keep their ftiells clofe 

 till the tide returns. Condudl of this kind plainly indicates both, 

 fenfation and a degree of intelligence. 



The 



