has taken centuries or thousands of years to
improve or modify most of our plants up to their present standard of
usefulness to man, we can understand how it is that neither Australia,
the Cape of Good Hope, nor any other region inhabited by quite
uncivilised man, has afforded us a single plant worth culture. It is
not that these countries, so rich in species, do not by a strange chance
possess the aboriginal stocks of any useful plants, but that the native
plants have not been improved by continued selection up to a standard
of perfection comparable with that acquired by the plants in countries
anciently civilised.

In regard to the domestic animals kept by uncivilised man, it should
not be overlooked that they almost always have to struggle for their
own food, at least during certain seasons. And in two countries very
differently circumstanced, individuals of the same species, having
slightly different constitutions or structure, would often succeed
better in the one country than in the other, and thus by a process of
"natural selection," as will hereafter be more fully explained, two
sub-breeds might be formed. This, perhaps, partly explains why the
varieties kept by savages, as has been remarked by some authors,
have more of the character of true species than the varieties kept in
civilised countries.

On the view here given of the important part which selection by man has
played, it becomes at once obvious, how it is that our domestic races
show adaptation in their structure or in their habits to man's wants
or fancies. We can, I think, further understand the frequently abnormal
character of our domestic races, and likewise their differences being so
great in external characters, and relatively so slight in internal parts
or organs. Man can hardly select, or only with much difficulty, any
deviation of structure excepting such as is externally visible; and
indeed he rarely cares for what is internal. He can never act by
selection, excepting on variations which are first given to him in some
slight degree by nature. No man would ever try to make a fantail till he
saw a pigeon with a tail developed in some slight degree in an unusual
manner, or a pouter till he saw a pigeon with a crop of somewhat unusual
size; and the more abnormal or unusual any character was when it first
appeared, the more likely it would be to catch his attention. But to use
such an expression as trying to make a fantail is, I have no doubt, in