f having a better
chance of leaving offspring, which will of course tend to reproduce the
peculiarities of their parents. Their offspring will, by a parity of
reasoning, tend to predominate over their contemporaries, and there
being (suppose) no room for more than one species such as A, the weaker
variety will eventually be destroyed by the new destructive influence
which is thrown into the scale, and the stronger will take its place.
Surrounding conditions remaining unchanged, the new variety (which we
may call B)--supposed, for argument's sake, to be the best adapted for
these conditions which can be got out of the original stock--will remain
unchanged, all accidental deviations from the type becoming at once
extinguished, as less fit for their post than B itself. The tendency
of B to persist will grow with its persistence through successive
generations, and it will acquire all the characters of a new species.

But, on the other hand, if the conditions of life change in any degree,
however slight, B may no longer be that form which is best adapted to
withstand their destructive, and profit by their sustaining, influence;
in which case if it should give rise to a more competent variety (C),
this will take its place and become a new species; and thus, by 'natural
selection', the species B and C will be successively derived from A.

That this most ingenious hypothesis enables us to give a reason for
many apparent anomalies in the distribution of living beings in time and
space, and that it is not contradicted by the main phenomena of life and
organization appear to us to be unquestionable; and so far it must be
admitted to have an immense advantage over any of its predecessors.
But it is quite another matter to affirm absolutely either the truth
or falsehood of Mr. Darwin's views at the present stage of the inquiry.
Goethe has an excellent aphorism defining that state of mind which he
calls 'Thatige Skepsis'--active doubt. It is doubt which so loves
truth that it neither dares rest in doubting, nor extinguish itself by
unjustified belief; and we commend this state of mind to students of
species, with respect to Mr. Darwin's or any other hypothesis, as to
their origin. The combined investigations of another 20 years may,
perhaps, enable naturalists to say whether the modifying causes and the
selective power, which Mr. Darwin has satisfactorily shown to exist in
nature, are competent to produce all the effects he ascribes