STATES OF INSECTS. (Lgg.) 53 
most eminent Entomologists and Physiologists since his 
time can be maintained against it. 
I shall first give you a short abstract o the new hy- 
pothesis. 
According to Dr. Herold— The successive skins of the 
caterpillar, 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 zt- 
self is formed anew upon every change of skin 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, &c., 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 
Jor 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, 
becomes fit for nutrition, whence the epiploon appears to 
be a kind of concrete chyle*. 
Need I repeat to you the hypothesis to which this 
stands opposed— That every caterpillar at its first exclu- 
* Entwickelungsgeschichte der Schmetterlinge, 12—27. 105—. 
