STRUCTURE OF PUP.E. 299 



which escapes by what is termed insensible perspi- 

 ration, is not so great as might have been supposed. 

 To ascertain what it was, Reaumur enclosed several 

 chrysalides, whose envelope seemed very dry, in se- 

 parate glass tubes, terminating at one end in a bulb, 

 and at the other hermetically sealed. He kept these 

 in a temperature of from 14 to 15 of his own 

 thermometer, corresponding to 63 65 Fahr. ; and 

 in a few days minute drops of water appeared on the 

 sides of the tube, which rolled down into the bulb 

 in form of a large drop not * eight or ten large 

 drops,' as Kirby and Spence, by some oversight, 

 have stated.* 



It would certainly be considered a strange and 

 untenable doctrine to maintain that it is the evapo- 

 ration produced from the egg by the heat of the in- 

 cubating mother, which causes the development of 

 the chick in the egg ; yet this is precisely similar to 

 what is maintained by Swammerdam, Kirby, and 

 Spence, the chief difference being, as Reaumur ob- 

 seves, that the chick has obvious organs for appro- 

 priating the nutriment contained in the egg, while the 

 insect in the pupa is surrounded, and, as it were, 

 bathed by the fluid, whose passage into the interior 

 vessels we cannot trace by the eye.j" That they do 

 find their way thither, the experiments above recorded 

 unanswerably demonstrate. 



The pupaB of insects, though they, in most in- 

 stances, cease from locomotion, and appear torpid, 

 are by no means really so; for it would be no less 

 incorrect to look upon them in such a light, than to 

 consider an ox torpid when reclining in a meadow to 

 ruminate and digest the grass he had just been de- 



* R/aumur, vol. i, p. 373, * Unegouttc beaucoup plus gros- 

 se ;' and Kirby and Spence, Intro, lii, 262. 

 f Mem. vol. i, p. 362, &c. 



