i34t THE PHILOSOPHY 



reach the furface, and that, during thefe efForts, bubbles oi 

 air ifTued from the anterior, but not from the pofterior ftig- 

 mata. He Hkewife remarked, that, on the fmalleft motion 

 of the animal, thefe bubbles were difcharged, but that they 

 were augmented both in quantity and fize, in proportion to 

 the agitations of the body. M. Bonnet immediately raifed 

 the water till it covered the two laft ftigmata ; the caterpil- 

 lar was violently agitated j but no bubbles of air, the com- 

 munication being cut off, appeared, and all motion ceafed. 

 He inftantly lowered the water, and expofed the two pofte- 

 rior ftigmata to the air ; the animal refumed its movements j 

 but in a moment after it expired. By another experiment, 

 M. Bonnet difcovered that a caterpillar lived eight days fuf- 

 pended in water, during all which time it breathed folely by 

 the two pofterior ftigmata. 



After thefe, and many other facts of a ftmilar kind, which 

 demonftrate that air is neceflary for the fupport and contiua- 

 tion of animal life, it fhall only be remarked, that, when cat- 

 erpillars undergo their laft change, and appear in the form 

 of flies of every denomination. Nature has ftill furnilhed them 

 with ftigmata, or refpiratory organs. 



Reptiles of all kinds are hkewife furnifhed with organs of 

 fefpiration. Land-fnails, at the approach of winter, bury 

 themfelves in the earth, or retire into holes of rocks, or of 

 old buildings, where they remain in a torpid ftate during the 

 feverity of the feafon. For protection and warmth, thefe 

 animals, when they go into their Winter habitations, form, by 

 means of a flime or faliva that iflues from every pore of theii* 

 bodies, a membranous cover which ftops up the moiiths of 

 their fhells. But this pellicle or cover, though apparently 

 pretty hard and folid, is fo thin and porous as not entirely to 

 exclude the entrance of air, without which the principle of 

 life could not be continued. Accordingly, when, by acci- 

 dent the pellicle is made too thick, and prevents a communi- 



