le diversity of influential circumstances, organic
beings of all the orders have been successively formed.

"Considerations so extraordinary, relatively to the ideas that the
vulgar have generally formed on the nature and origin of living
bodies, will be naturally regarded by you as stretches of the
imagination unless I hasten to lay before you some observations and
facts which supply the most complete evidence.

"From the point of view of knowledge based on observation the
philosophic naturalist feels convinced that it is in that which is
called the lowest classes of the two organic kingdoms--_i.e._, in
those which comprise the most simply organized beings--that we can
collect facts the most luminous and observations the most decisive
on the _production_ and the reproduction of the living beings in
question; on the causes of the formation of the organs of these
wonderful beings; and on those of their developments, of their
diversity and their multiplicity, which increase with the concourse
of generations, of times, and of influential circumstances.

"Hence we may be assured that it is only among the singular beings
of these lowest classes, and especially in the lowest orders of
these classes, that it is possible to find on both sides the
primitive germs of life, and consequently the germs of the most
important faculties of animality and vegetality."

_Modification of the organization from one end to the other of the
animal chain._

"One is forced," he says, "to recognize that the totality of existing
animals constitute _a series of groups_ forming a true chain, and that
there exists from one end to the other of this chain a gradual
modification in the structure of the animals composing it, as also a
proportionate diminution in the number of faculties of these animals
from the highest to the lowest (the first germs), these being without
doubt the form with which nature began, with the aid of much time and
favorable circumstances, to form all the others."

He then begins with the mammals and descends to molluscs, annelids, and
insects, down to the polyps, "as it is better to proceed from the known
to the unknown;" but farther on (p. 38) he finally remarks:

"Ascend from the most simple to the most compound, depart from the
most imperfect animalcule and ascend along the scale up to the
animal richest in structure and faculties; constantly preserve the
order of re