s of life. Nature acts uniformly and slowly during vast periods
of time on the whole organisation, in any way which may be for each
creature's own good; and thus she may, either directly, or more probably
indirectly, through correlation, modify the reproductive system in the
several descendants from any one species. Seeing this difference in the
process of selection, as carried on by man and nature, we need not be
surprised at some difference in the result.

I have as yet spoken as if the varieties of the same species were
invariably fertile when intercrossed. But it seems to me impossible to
resist the evidence of the existence of a certain amount of sterility in
the few following cases, which I will briefly abstract. The evidence
is at least as good as that from which we believe in the sterility of
a multitude of species. The evidence is, also, derived from hostile
witnesses, who in all other cases consider fertility and sterility as
safe criterions of specific distinction. Gartner kept during several
years a dwarf kind of maize with yellow seeds, and a tall variety with
red seeds, growing near each other in his garden; and although these
plants have separated sexes, they never naturally crossed. He then
fertilised thirteen flowers of the one with the pollen of the other; but
only a single head produced any seed, and this one head produced only
five grains. Manipulation in this case could not have been injurious, as
the plants have separated sexes. No one, I believe, has suspected that
these varieties of maize are distinct species; and it is important to
notice that the hybrid plants thus raised were themselves PERFECTLY
fertile; so that even Gartner did not venture to consider the two
varieties as specifically distinct.

Girou de Buzareingues crossed three varieties of gourd, which like
the maize has separated sexes, and he asserts that their mutual
fertilisation is by so much the less easy as their differences are
greater. How far these experiments may be trusted, I know not; but the
forms experimentised on, are ranked by Sagaret, who mainly founds his
classification by the test of infertility, as varieties.

The following case is far more remarkable, and seems at first quite
incredible; but it is the result of an astonishing number of experiments
made during many years on nine species of Verbascum, by so good an
observer and so hostile a witness, as Gartner: namely, that yellow
and white varieties of the same spe