be maintained and carried out into a system on
similar grounds? If so, however unproved, it would appear to be a
tenable hypothesis, which is all that its author ought now to claim.
Such hypotheses as from the conditions of the case can neither be proved
nor disproved by direct evidence or experiment are to be tested only
indirectly, and therefore imperfectly, by trying their power to
harmonize the known facts, and to account for what is otherwise
unaccountable. So the question comes to this:

What will an hypothesis of the derivation of species explain which the
opposing view leaves unexplained?

Questions these which ought to be entertained before we take up the
arguments which have been advanced against this theory. We can only
glance at some of the considerations which Darwin adduces, or will be
sure to adduce in the future and fuller exposition which is promised.
To display them in such wise as to indoctrinate the unscientific reader
would require a volume. Merely to refer to them in the most general
terms would suffice for those familiar with scientific matters, but
would scarcely enlighten those who are not. Wherefore let these trust
the impartial Pictet, who freely admits, that, "in the absence of
sufficient direct proofs to justify the possibility of his hypothesis,
Mr. Darwin relies upon indirect proofs, the bearing of which is real and
incontestable"; who concedes that "his theory accords very well with the
great facts of comparative anatomy and zooelogy,--comes in admirably to
explain unity of composition of organisms, also to explain rudimentary
and representative organs, and the natural series of genera and
species,--equally corresponds with many palaeontological data,--agrees
well with the specific resemblances which exist between two successive
faunas, with the parallelism which is sometimes observed between the
series of palaeontological succession and of embryonal development,"
etc.; and finally, although he does not accept the theory in these
results, he allows that "it appears to offer the best means of
explaining the manner in which organized beings were produced in epochs
anterior to our own."

What more than this could be said for such an hypothesis? Here,
probably, is its charm, and its strong hold upon the speculative mind.
Unproven though it be, and cumbered _prima facie_ with cumulative
improbabilities as it proceeds, yet it singularly accords with great
classes of facts otherwise insulate