CH. II.] METAMORPHOSES OF INSECTS. 31 



from what he denominates the blood or chyle," 

 agreeing with other naturalists in the supposition 

 that the epiploon or corps graisseux (a mass of thick- 

 ish mucilage contained in floating membranes appa- 

 rently analogous to the fat in the larger animals) is 

 stored up in the larva, in order that, in the pupa 

 state, it may serve for the development of the 

 imago. 



Now it appears to us, that although the first-men- 

 tioned theory seems at first sight to be completely 

 at variance with the second, yet, on a more careful 

 consideration, the differences will not be found to be 

 very great. 



It is to be observed in the first place, as giving 

 much weight to the views of Herold, that in the 

 dissections of Lyonnet and others who have studied 

 the anatomy of caterpillars in their natural state, 

 no traces of an enclosed animal or of any succes- 

 sion of skins have been observed, except the mu- 

 cous network and fatty mucilage noticed above. 



It is further to be observed, that in the works of 

 Swammerdam, Reaumur, &c., who have by unnat- 

 ural means succeeded in discovering in the body of 

 the caterpillar the germe of the butterfly, no traces 

 of the successive skins of the caterpillar or of the 

 chrysalis have been observed. Indeed, as we have 

 seen in the preceding chapter, the outer skin of the 

 chrysalis is not formed until the insect has become 

 a pupa, although it may be said that the gummy 

 fluid which is employed by the pupa to form a coat- 

 ing, which upon exposure to the air immediately 

 becomes hardened, must exist in its fluid state in the 

 body of the caterpillar. And the same remark will 

 appi'y to the other successive skins of the insect. 



Herold's theory is formed in reference to the 

 manner in which the development of the various 

 organs becomes observable in a state of nature. It 

 is not, however, to be supposed, that the period 

 when thi'ise organs are first observable is necessa- 



