See how different the leaves of the cabbage are, and
how extremely alike the flowers; how unlike the flowers of the
heartsease are, and how alike the leaves; how much the fruit of the
different kinds of gooseberries differ in size, colour, shape, and
hairiness, and yet the flowers present very slight differences. It is
not that the varieties which differ largely in some one point do not
differ at all in other points; this is hardly ever, perhaps never, the
case. The laws of correlation of growth, the importance of which
should never be overlooked, will ensure some differences; but, as a
general rule, I cannot doubt that the continued selection of slight
variations, either in the leaves, the flowers, or the fruit, will
produce races differing from each other chiefly in these characters.
It may be objected that the principle of selection has been reduced to
methodical practice for scarcely more than three-quarters of a
century; it has certainly been more attended to of late years, and
many treatises have been published on the subject; and the result, I
may add, has been, in a corresponding degree, rapid and important. But
it is very far from true that the principle is a modern discovery. I
could give several references to the full acknowledgment of the
importance of the principle in works of high antiquity. In rude and
barbarous periods of English history choice animals were often
imported, and laws were passed to prevent their exportation: the
destruction of horses under a certain size was ordered, and this may
be compared to the "roguing" of plants by nurserymen.
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