22 NATURAL HISTORY- [cH. I. 



To put this supposition to the test of experiment, 

 Reaumur accurately weighed two chrysalides im- 

 mediately after their exclusion ; one of these weigh- 

 ed nearly eighteen, and the other nearly nineteen 

 grains ; at the end of sixteen days, when they were 

 ready to become butterflies, he found that the light- 

 est weighed more than seventeen, and the heaviest 

 more than eighteen grains : hence the fluid escaping 

 by insensible perspiration must be very trifling in 

 quantity. It consists of a kind of aqueous and very 

 limpid liquor, as Reaumur discovered by an experi- 

 ment recorded in his first volume, in which he 

 placed chrysalides in glass tubes hermetically seal- 

 ed, when it was found, at the end of several days, 

 that small drops of a very clear liquid were attached 

 to the inner surface of the tube, sufficient, when 

 they had rolled to the bottom, to form a much lar- 

 ger drop. In his second volume Reaumur appears 

 more decidedly to consider that it is by evaporation 

 that the inspissation of the fluids is effected, having 

 repeated the experiment, and discovered that the 

 aqueous fluid collected in the bulb of the tube had, 

 at the end of a few days, acquired a volume ex- 

 ceeding that of eight or ten large drops. Such are 

 the views of Reaumur: and Messrs. Kirby and 

 Spence observe, with respect to the subject, that 

 " the end to be accomplished during the pupa's ex- 

 istence is the gradual evaporation of the watery 

 parts of this fluid, and the development of the organs 

 of the enclosed animal by the absorption and assimi- 

 lation of the residuum." Now it will be seen that 

 this observation perfectly corresponds with the 

 views and the results of the experiments of M. 

 Reaumur, notwithstanding a recent author has at- 

 tempted to prove that Messrs. Kirby and Spence 

 misunderstood and misapplied the observations of 

 Reaumur. 



It is also to be borne in mind, with reference to 

 the solution of this question, that the chrysalis is 



