as largely
modified.

As man has considered only utility to himself, or the satisfaction of
his love of beauty, of novelty, or merely of something strange or
amusing, the variations he has thus produced have something of the
character of monstrosities. Not only are they often of no use to the
animals or plants themselves, but they are not unfrequently injurious to
them. In the Tumbler pigeons, for instance, the habit of tumbling is
sometimes so excessive as to injure or kill the bird; and many of our
highly-bred animals have such delicate constitutions that they are very
liable to disease, while their extreme peculiarities of form or
structure would often render them quite unfit to live in a wild state.
In plants, many of our double flowers, and some fruits, have lost the
power of producing seed, and the race can thus be continued only by
means of cuttings or grafts. This peculiar character of domestic
productions distinguishes them broadly from wild species and varieties,
which, as will be seen by and by, are necessarily adapted in every part
of their organisation to the conditions under which they have to live.
Their importance for our present inquiry depends on their demonstrating
the occurrence of incessant slight variations in all parts of an
organism, with the transmission to the offspring of the special
characteristics of the parents; and also, that all such slight
variations are capable of being accumulated by selection till they
present very large and important divergencies from the ancestral stock.

We thus see, that the evidence as to variation afforded by animals and
plants under domestication strikingly accords with that which we have
proved to exist in a state of nature. And it is not at all surprising
that it should be so, since all the species were in a state of nature
when first domesticated or cultivated by man, and whatever variations
occur must be due to purely natural causes. Moreover, on comparing the
variations which occur in any one generation of domesticated animals
with those which we know to occur in wild animals, we find no evidence
of greater individual variation in the former than in the latter. The
results of man's selection are more striking to us because we have
always considered the varieties of each domestic animal to be
essentially identical, while those which we observe in a wild state are
held to be essentially diverse. The greyhound and the spaniel seem
wonderful, as varieties of