finally return to one or the other stem-form of the originally
crossed species. Nor can we oppose to these facts the consideration that
the period of time during which mankind has observed the organisms is too
short. For the permanence of very many {103} species can be traced through
thousands of years, and the shortness of the period of our observations is
amply counterbalanced on the one hand by the multitude of species from all
parts of the organic systems which come under our notice, on the other by
the immense alterations in the conditions of existence to which man submits
plants and animals. How great, for instance, are the alterations in the
conditions of existence which tropical plants undergo in our hot-houses and
gardens! And the only alteration they show is that they are stunted and
only bear blossoms with difficulty and fruits with still greater
difficulty.[6] Now, if the ever-active selection principle does not produce
in thousands of years even minimum alterations which can be observed,
science certainly is justified in doubting for the present the asserted
effect of that principle.

Thus not only are the _facts_ directly opposed to the autocracy of the
selection principle; but _logic_ is also none the less so. For, under the
most favorable circumstances, selection would only explain the
_preservation_ and perhaps also the _increase_ of useful qualities and
organs, _if_ the same are already in existence and have shown themselves
useful to the individual; but would not explain their _origination_. This
would rather most emphatically be left to _chance_. According to the strict
selection theory, it would be _pure chance_ that among the thousands and
thousands of individual qualities of the individuals of a species, such
qualities are always existing as offer advantages to the individual in his
struggle for existence. And it would be a second series of chances, which
from generation to generation would {104} have to coincide with the first,
that among the individual qualities advantageous to the individual and
making it victorious in the struggle for existence, there should be found
always just those qualities which develop the species and raise it to a
higher rank and order in the zooelogical and botanical systems. But the
total of improbabilities which would have to be overcome continually in
this theatre of chance, would in the course of generations necessarily
amount to infinity. Thus, in the very beginnin