which have existed thus as anciently as nature, implies the
necessity that the individuals of one and the same species cannot
mix, in their acts of generation, with the individuals of a
different species. Unfortunately observation has proved, and still
proves every day, that this consideration has no basis; for the
hybrids, very common among plants, and the unions which are often
observed between the individuals of very different species among
animals, have made us perceive that the limits between these
species, supposed to be constant, are not so rigid as is supposed.

"In truth, nothing often results from these singular unions,
especially when they are very incongruous, as the individuals which
result from them are usually sterile; but also, when the disparities
are less great, it is known that the drawbacks (_defauts_) with
which it has to do no longer exist. However, this means alone
suffices to gradually create the varieties which have afterwards
arisen from races, and which, with time, constitute that which we
call _species_.

"To judge whether the idea which is formed of species has any real
foundation, let us return to the considerations which I have already
stated; they are, namely--

"1. That all the organic bodies of our globe are veritable
productions of nature, which she has created in succession at the
end of much time.

"2. That in her course nature has begun, and begins anew every day,
by forming the simplest organic bodies, and that she directly forms
only these--that is to say, only these first primitive germs
(_ebauches_) of organization, which have been badly characterized by
the expression of "spontaneous generations" (_qu'on a designees
mal-a-propos par l'expression de Generations spontanees_).

"3. That the first germs (_ebauches_) of the animals and plants were
formed in favorable places and circumstances. The functions of life
beginning and an organic movement established, these have
necessarily gradually developed the organs, so that after a time and
under suitable circumstances they have been differentiated, as also
the different parts (_elles les ont diversifies ainsi qui les
parties_).

"4. That the power of increase in each portion of organic bodies
being inherited at the first production (_effets_) of life, it has
given rise to different modes of multiplication and of regeneration
of individuals; and in