OF NATURAL HISTORY. IgJJ 



two large tracheae or wind-pipes within the body of the ani-». 

 mal, and maintains the principle of life. When the tails are 

 below the furface, they occalionally emit fmall bubbles of 

 air, which are vilible to the naked eye ; and immediately re- 

 pair to the furface for frefli fupplies. Thefe rat-tailed worms 

 pafs the iirli; and longefl part of their lives under water 5 

 when near the time of their transformation, they leave the 

 water, go under the ground, and are there tranformed into 

 chryfalids ; and, laRly, from this {late they are transformed 

 hito flies, and fpend the remainder of their exiftence in the 

 air. 



Another fpecies of aquatic worms merit attention. They 

 frequent marilies, ditches, and flagnating waters. Their gen- 

 eral colour is a jrreenilh brown. Their bodies condft of 



o 



eleven rings •, and their ikin is not cruftaceous, but rather 

 refembles parchment. Though tliefe animals, before their 

 transformation into flies, live in Vv'ater, air is neceilary to fbp? 

 port their principle of life •, and the apparatus with whicl^ 

 Nature has farnillied them for that important purpofe de^ 

 ferves our notice. The b.ft ring, or termination of their 

 bodies, is open, and ferves as a conductor of air. From this 

 laft ring proceed a number of hairs, which, when examined 

 by the microfcope, are found to be real feathers with regu^ 

 lar vanes. In particular iituations, they bend the lafi ring 

 in fuch a manner as to reach the furface of the water or 

 mud in which they are placed. Thefe feathers prevent the 

 water from entering into the tube, or organ of refpiration ; 

 and, when the animal raifes the termination of its body to 

 the furface, in order to receive air, it ere£ts and fpreads the 

 feathers, and by this means expofes the end of the tube to 

 the atmofphere. When cautioufly cut open, two large \ei~ 

 fels, or tracheae, appear on each fide, and occupy almoft one 

 half of the body. Both of thefe wind-pipes terminate in the 

 ©pen tube, or lafl ring. Though thefe worms are furniflied 



