at all the others may have issued."[143]

He then establishes, on the one hand, nine species which he regarded as
isolated, and, on the other, fifteen principal genera, primitive sources
or, as we would say, ancestral forms, from which he derived all the
animals (mammals) known to him.

Hence he believed that he could derive the dog, the jackal, the wolf,
and the fox from a single one of these four species; yet he remarks,
_per contra_, in 1753:

"Although we cannot demonstrate that the production of a species by
modification is a thing impossible to nature, the number of
contrary probabilities is so enormous that, even philosophically, we
can scarcely doubt it; for if any species has been produced by the
modification of another, if the species of ass has been derived from
that of the horse, this could have been done only successively and
by gradual steps: there would have been between the horse and ass a
great number of intermediate animals, the first of which would
gradually differ from the nature of the horse, and the last would
gradually approach that of the ass; and why do we not see to-day the
representatives, the descendants of those intermediate species? Why
are only the two extremes living?" (tome iv., p. 390). "If we once
admit that the ass belongs to the horse family, and that it only
differs from it because it has been modified (_degenere_), we may
likewise say that the monkey is of the same family as man, that it
is a modified man, that man and the monkey have had a common origin
like the horse and ass, that each family has had but a single
source, and even that all the animals have come from a single
animal, which in the succession of ages has produced, while
perfecting and modifying itself, all the races of other animals"
(tome iv., p. 382). "If it were known that in the animals there had
been, I do not say several species, but a single one which had been
produced by modification from another species; if it were true that
the ass is only a modified horse, there would be no limit to the
power of nature, and we would not be wrong in supposing that from a
single being she has known how to derive, with time, all the other
organized beings" (_ibid._, p. 382).

The next sentence, however, translated, reads as follows:

"But no. It is certain from revelation that all animals have alike
been favored with the grace of an act of direct creation, and tha