298 INSECT TRANSFORMATIONS. 



' soon after its assumption of that state, you will find 

 its interior filled with a milky fluid, in the midst of 

 which the rudiments of its future limbs and organs, 

 themselves almost as fluid, swim. Now the end to 

 be accomplished during the pupa's existence 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 assimilation of the resi- 

 duum.'* The evaporation, however, is so very 

 inconsiderable, that it is evidently only of secondary 

 consequence. 



When the great quantity of fluid in the body of the 

 chrysalis is taken into consideration, we must infer 

 that if it were evaporated to any extent, the insect 

 would be reduced to a mere shadow. We are dis- 

 posed, therefore, to agree with Reaumur in thinking 

 it more probable that the fluids of pupae become 

 united to the more solid parts, in the same way 

 as the blood and lymph in our own bodies go 

 to the extension or to the repair of our bones and 

 muscles. To put this to the test of experiment, 

 Reaumur, in the month of July, accurately weighed 

 two chrysalides the instant they were disencumbered 

 of the sloughs of the larvae. The lightest weighed a 

 trifle less than 18, and the heavier a trifle less than 

 19 grains. Putting them aside separately, with a 

 note of their respective weights, he re-weighed them 

 every two or three days for sixteen days successively, 

 that is, till they were transformed into perfect insects. 

 On the last day, the lighter weighed more than 17, 

 and the heavier more than 18 grains; consequently 

 the fluid evaporated during this period did not amount 

 to a grain, perhaps not to more than ^ of a grain. On 

 weighing the insects themselves which issued from 

 these pupa, together with the cast slough, the weight 

 was . not sensibly different. The fluid, therefore, 



* Introd. iii, 262. 



