ISO THE PHILOSOPHY 



with organs of refpiration, and a£lually refpire air, yet M. de 

 Reaumur difcoverered that fome of them could live more 

 than twenty-four hours without refpiration. 



So anxious is Nature to provide animals, in* every ftate of 

 their exiftence, with air, that, after the transformation of 

 many infe^ls into chryfalids, fhe creates inftruments for that 

 purpofe, which did not exill previous to their transforma- 

 tion. The rat-tailed worms, formerly mentioned, foon after 

 they are transformed into chryfalids, inflead of a foft pliable 

 Ikin, are covered with a hard cruftaceous fubftance, feeming- 

 ly impervious to the air ; and the tail, which was the wind- 

 pipe of the animal in its firft ftate, gradually vanifhes. In a 

 few hours, however, four hollow horns fhoot out, two from 

 the fore, and two from the hind, part of what was the head 

 of the animal. Thefe horns, which are hard and tubular, 

 M. de Reaumur difcovered to be real wind-pipes, deftlned 

 for the introdudlion of air into the cbryfulis, a llate in which 

 the animals have the appearance of being almoft totally dead, 

 and, of courfe, fhould feem to have little ufe for refpira- 

 tion. He likewife difcovered that thefe horns, which hrid 

 pierced the hard exterior covering, terminated in as many 

 tracheae in the body of the animal. This faft affords a 

 ftrong example of the neceility of air for fuftaining the prin- 

 ciple of life, even in its loweft condition. After thefe ani- 

 mals pafs from the chryfalis ftate to that of flies, they are 

 deprived both of their tails and horns. But Nature, in this 

 laft ftage of their exiftence, has not left them without proper 

 refources for the introduction of air into their bodies. In- 

 ftead of protuberant tracheae in the form of tails or horns, 

 they now, like other flies, receive air by means of ftigmata, 

 or holes, varioufly difpofed over different parts of the body. 



The nymph of the libella, or dragon-fly, refpires water, 

 in the fame manner as men and quadrupeds refpire air. Wo 

 r?c9iye and throw out the air hy the mouth and noftrils^ 



