STATES OF INSECTS. (Ligg.) 5% 
pillar, and grow and are successively developed by the 
action of the nutritive fluid? In the pupa of many Di- 
ptera the inclosed animal, even under the microscope, 
appears without parts or organs, like a mere pulp; but 
Bonnet telis us, that if boiled, all the parts of the pupa 
appear?, which proves the preexistence of these parts 
even when not to be discerned, and that nothing but the 
evaporation of the fluids in which they swim is wanted 
to render them visible. 
Mr. William MacLeay has with great truth observed : 
‘‘ The true criterion of animal as well as vegetable per- 
fection is the ability to continue the species?;” and in 
their progress to this state certain changes take place in 
the parts and organs of ali animals and vegetables: 
there is, therefore, an analogy in this respect between 
them ; and this analogy also furnishes another argument 
against Dr. Herold’s hypothesis, as we shall presently 
see. ‘These changes are of three kinds: In the vegeta- 
ble kingdom, at least in the pheenogamous classes, there 
is a succession of developments terminating in the ap- 
pearance of the generative organs, inclosed in the flower ; 
in this kind the integuments, or most of them, are usually 
persistent. In insects and other annulose and some ver- 
tebrate animals, there is a succession of spoliations, or 
simultaneous changes of the whole integument, till the 
animal appears in its perfect form with powers of repro- 
duction ; in this kind the integuments are caducous.—In 
man and most of the vertebrate animals there is a gra- 
dual action of the vital forces in different organs till they 
are fitted for reproduction; accompanied, as progress is 
made to the adult state, by the acquisition of certain or- 
* uvr, vii. 315, » Hor. Entomolog. 446. 
