pose
that all the breeds were suddenly produced as perfect and as useful as
we now see them; indeed, in many cases, we know that this has not been
their history. The key is man's power of accumulative selection. Nature
gives successive variations; man adds them up in certain directions
useful to him. In this sense he may be said to have made for himself
useful breeds.

The great power of this principle of selection is not hypothetical. It
is certain that several of our eminent breeders have, even within a
single lifetime, modified to a large extent their breeds of cattle and
sheep. What English breeders have actually effected is proved by the
enormous prices given for animals with a good pedigree; and these have
been exported to almost every quarter of the world. The same principles
are followed by horticulturists, and we see an astonishing improvement
in many florists' flowers, when the flowers of the present day are
compared with drawings made only twenty or thirty years ago.

The practice of selection is far from being a modern discovery. The
principle of selection I find distinctly given in an ancient Chinese
encyclopaedia. Explicit rules are laid down by some of the Roman
classical writers. It is clear that the breeding of domestic animals was
carefully attended to in ancient times, and is now attended to by the
lowest savages. It would, indeed, have been a strange fact had attention
not been paid to breeding, for the inheritance of good and bad qualities
is so obvious.

Study of the origin of our domestic races of animals and plants leads to
the following conclusions. Changed conditions of life are of the highest
possible importance in causing variability, both by acting directly on
the organisation, and indirectly by affecting the reproductive system.
Spontaneous variation of unknown origin plays its part. Some, perhaps a
great, effect may be attributed to the increased use or disuse of parts.

The final result is thus rendered infinitely complex. In some cases the
intercrossing of aboriginally distinct species appears to have played
an important part in the origin of our breeds. When several breeds have
once been formed in any country, their occasional intercrossing, with
the aid of selection, has, no doubt, largely aided in the formation of
new sub-breeds; but the importance of crossing has been much
exaggerated, both in regard to animals and to those plants which are
propagated by seed. Over all these caus