e
variation{242}. How incomparably "truer" then would a race produced by
the above rigid, steady, natural means of selection, excellently trained
and perfectly adapted to its conditions, free from stains of blood or
crosses, and continued during thousands of years, be compared with one
produced by the feeble, capricious, misdirected and ill-adapted
selection of man. Those races of domestic animals produced by savages,
partly by the inevitable conditions of their life, and partly
unintentionally by their greater care of the individuals most valuable
to them, would probably approach closest to the character of a species;
and I believe this is the case. Now the characteristic mark of a
species, next, if not equal in importance to its sterility when crossed
with another species, and indeed almost the only other character
(without we beg the question and affirm the essence of a species, is its
not having descended from a parent common to any other form), is the
similarity of the individuals composing the species, or in the language
of agriculturalists their "trueness."

{242} See _Var. under Dom._, Ed. ii. vol. II. p. 230.

_Difference between "Races" and "Species" in fertility when crossed._

The sterility of species, or of their offspring, when crossed has,
however, received more attention than the uniformity in character of the
individuals composing the species. It is exceedingly natural that such
sterility{243} should have been long thought the certain characteristic
of species. For it is obvious that if the allied different forms which
we meet with in the same country could cross together, instead of
finding a number of distinct species, we should have a confused and
blending series. The fact however of a perfect gradation in the degree
of sterility between species, and the circumstance of some species most
closely allied (for instance many species of crocus and European heaths)
refusing to breed together, whereas other species, widely different,
and even belonging to distinct genera, as the fowl and the peacock,
pheasant and grouse{244}, Azalea and Rhododendron, Thuja and Juniperus,
breeding together ought to have caused a doubt whether the sterility did
not depend on other causes, distinct from a law, coincident with their
creation. I may here remark that the fact whether one species will or
will not breed with another is far less important than the sterility of
the offspring when produced; for even some dome