s to the power of nature and its course relatively to the
existence of these bodies, also as to the variations which they
undergo, we certainly have to seek for them in the lowest classes of
the two organic kingdoms (the animals and the plants). It is in the
classes which comprise the living bodies whose organization is the
least complex that we can observe and bring together facts the most
luminous, observations the most decisive on the origin of these
bodies, on their reproduction and their admirable diversification,
finally on the formation and the development of their different
organs, the whole process being aided by the concurrence of
generations, of time, and of circumstances.

"It is, indeed, among living bodies the most multiplied, the most
numerous in nature, the most prompt and easy to regenerate
themselves, that we should seek the most instructive facts bearing
on the course of nature and on the means she has employed to create
her innumerable productions. In this case we perceive that,
relatively to the animal kingdom, we should chiefly give our
attention to the invertebrate animals, because their enormous
multiplicity in nature, the singular diversity of their systems of
organization and of their means of multiplication, their increasing
simplification, and the extreme fugacity of those which compose the
lowest orders of these animals, show us much better than the others
the true course of nature, and the means which she has used and
which she is still incessantly employing to give existence to all
the living bodies of which we have knowledge.

"Her course and her means are without doubt the same for the
production of the different plants which exist. And, indeed, though
it is not believed, as some naturalists have wrongly held, but
without proof, that plants are bodies more simple in organization
than the most simple animals, it is a veritable error which
observation plainly denies.

"Truly, vegetable substance is less surcharged with constituent
principles than any animal substance whatever, or at least most of
them, but the substance of a living body and the organization of
these bodies are two very different things. But there is in plants,
as in animals, a true gradation in organization from the plant
simplest in organization and parts up to plants the most complex in
structure and with the most diversified organs.

"If th