EXPERIMENTS ON INSECTS. 313 



the envelope, taking care to leave the respiratory spi- 

 racles unobstructed. But it is most obvious, that the 

 greater part of all the evaporation which occurs must 

 be through the spiracles, in the same way as a large 

 proportion of the moisture of the human body passes 

 off by the breath. The result, however, of Reau- 

 mur's experiments with the varnished chrysalides was, 

 that they were developed several weeks later than 

 when placed in their natural circumstances, which 

 proves, we think, that the envelope has considerable 

 influence on the transforrnatory process going on in 

 the interior, even were we to leave the transpiration of 

 moisture out of the question.* 



We may remark, that the results of these experi- 

 ments afford interesting illustrations of the torpidity of 

 both the larger animals and of plants. In the United 

 States of America, for example, many species of ani- 

 mals which become torpid in Pennsylvania, and other 

 more northern parts of the country, remain lively in 

 the Carolinas, and other southern parts of the conti- 

 nent. | Mr Gough found that the dormouse may be 

 prevented from becoming torpid by supplying it plen- 

 tifully with food; and Dr Reeve, of Norwich, ob- 

 served the same circumstance in a hedge-hog, which 

 being kept warm and well fed, showed no disposition 

 to become torpid even during severe weather. J Pal- 

 las had a tame marmot, also, which having become 

 very fat during the summer, showed no disposition to 

 torpidity, though exposed to a temperature which 

 threw the whole species into a torpid state in that part 

 of Siberia. In the vegetable kingdom, again, it is a 

 very common phenomenon to see plants revive after 

 exposure to severe frosts. Mr Gough made some in- 



* Reaumur, Mem. vol. ii. p. 56. 

 t Barton, in Amer. Phil, Trans, vol. iv. 

 $ Reeve on Torpidity, p. 73. 

 TOL. vi. 27 



