STATES OF INSECTS. 53 



detail the states of insects, I should again call your atten- 

 tion to this subject, and endeavour to ascertain whether 

 Dr. Herold's hypothesis rests upon a solid foundation ; 

 or whether that adopted from Swammerdam by all the 

 most eminent Entomologists and Physiologists since his 

 time can be maintained against it. 



I shall first give you a short abstract of the new hy- 

 pothesis. 



According to Dr. Herold — The successive skins of the 

 catetpillar, the pupa-case, the future butterfly, and its 

 parts and organs, except those of sex which he discovered 

 in the newly excluded larva, do not preexist as germes, but 

 are formed successively from the rete mucosum, which it- 

 self is formed anew upon every change of shin from what 

 he denominates the blood, or the chyle after it has passed 

 through the pores of the intestinal canal into the general 

 cavity of the body, where, being oxygenated by the air- 

 vessels, it performs the nutritive functions of blood. He 

 attributes these formations to a vis formatrix (Bildende 

 Kraft). 



The caul or epiploon (Fett-masse), the corps graisseux 

 of Reaumur, fyc, which he supposes to be formed from the 

 superfluous blood, he allows, with most physiologists, to be 

 stored up in the larva, that in the pupa state it may serve 

 for the development of the imago. But he differs from 

 them in asserting that in this state it is destined to two 

 distinct purposes— first, for the production of the muscles 

 of the butterfly, which he affirms are generated from it in 

 the shape of slender bundles of fibres ; —and secondly, for 

 the development and nutrition of the organs formed in the 

 larva, to effect which, he says, it is dissolved again into 

 the mass of blood, and being oxygenated by the air-vessels,. 



