26 THEPHILOSOPHY 



propagating their fpecies, the females depofit their eggs, and the 

 fa-me circle of animation and change perpetually goes round. Hence 

 the ftrufture and figure of the fame individual animals are three- 

 fold, which renders the knowledge of infeds extremely complicated, 

 as we muft be acquainted with them in the feveral forms they fuc- 

 ceffively aflume. 



There is another peculiarity in the ftrutture of infefts. They 

 are deprived of bones. But that defetSt is fupplied, in fome, by a 

 membranous or mulbular fkin, and, in others, by a cruftaceous or 

 horny covering. In this circumftance, infei5ls referable the ftiell- 

 aaimals, whole bones conftitute the external parts of their bodies. 



In general, the bodies of infects are corapofed of a head, trunk, 

 a-nd abdomen. The head is commonly attached to the trunk by a 

 pint or articulation. Befide eyes, feelers, and mouth, the heads of 

 iome infects are furniflied with palpi fixed to the mouth; and they 

 are either four or fix in number. Each of them confifts of two, 

 'three, or four joints, and are often miRaken for the antennae or 

 feelers. Thefe inftruments feem to ferve the animals inftead of 

 hands ; for they employ the palpi- to bring the food to their mouths, 

 and to keep it fteady while eating. It is aflerted by Linnaeus, and 

 other Naturalifls, that the heads of infeds are deftitute of brains, 

 noilrils, and ears. The minutenefs of the animals under confidera- 

 tion may have hitherto prevented us from diltinguifiiing thefe or- 

 gans. If they want a brain, it is certain that their fenfe of feeing is 

 acute; and we know that they are amply fupplied with nerves, 

 which produce the fame effeds as the brain in larger animals. If 

 ihey are deprived of noftrils, the flighteft attention muft convince 

 lis, that fome of them poffefs the fenfe of fmelling in a very high 

 degree. Upon any other fyppofition, how fhould the different fpe- 

 sies of flies, the moment they efcape from the chryfalis ftate, diftin- 

 I guifh, 



