INTRODUCTION. XKXV 
of those organs which are destined to form their 
future corporeal condition, they become an aurelia, 
during which state they are quite inert, and without 
any cravings of hunger. Thereafter they assume 
the imago, or perfect condition, when, in general, 
their stomachs are contracted to a tenth of their 
former capacity; and they frequently exist without 
food at all, or only sip the nectar of flowers. After 
this period, the chief aim the animal seems to have 
in view, is to propagate its kind, and no other object 
can divert it from its purpose. 
The new relations which this singular arrange- 
ment introduces into nature, are not less wonderful 
than striking; for one individual animal combines 
in itself three animals, in all respects specifically 
different, whose manner of existing, and alimentary 
nourishment, are diametrically opposite. 
Several of the vertebrate animals, such as frogs, 
toads, and water newts, undergo metamorphoses in 
some respects analogous to those of the insect tribes ; 
the first form of these being a tadpole, which is 
widely different from that which they afterwards 
assume. These reptiles, too, as well as snakes, cast 
their skins by an operation somewhat similar to the 
larvee of insects. There is nothing, however, in 
