t ask him whether the
closely allied natural species which he has studied may not have descended
from a common progenitor, and he in his turn will perhaps reject the notion
with scorn. Thus the naturalist and breeder may mutually learn a useful
lesson from each other.

* * * * *

_Summary on Selection by Man._--There can be no doubt that {247} methodical
selection has effected and will effect wonderful results. It was
occasionally practised in ancient times, and is still practised by
semi-civilised people. Characters of the highest importance, and others of
trifling value, have been attended to, and modified. I need not here repeat
what has been so often said on the part which unconscious selection has
played: we see its power in the difference between flocks which have been
separately bred, and in the slow changes, as circumstances have slowly
changed, which many animals have undergone in the same country, or when
transported into a foreign land. We see the combined effects of methodical
and unconscious selection in the great amount of difference between
varieties in those parts or qualities which are valued by man, in
comparison with those which are not valued, and consequently have not been
attended to. Natural selection often determines man's power of selection.
We sometimes err in imagining that characters, which are considered as
unimportant by the systematic naturalist, could not be affected by the
struggle for existence, and therefore be acted on by natural selection; but
striking cases have been given, showing how great an error this is.

The possibility of selection coming into action rests on variability; and
this is mainly caused, as we shall hereafter see, by changes in the
conditions of life. Selection is sometimes rendered difficult, or even
impossible, by the conditions being opposed to the desired character or
quality. It is sometimes checked by the lessened fertility and weakened
constitution which follow from long-continued close interbreeding. That
methodical selection may be successful, the closest attention and
discernment, combined with unwearied patience, are absolutely necessary;
and these same qualities, though not indispensable, are highly serviceable
in the case of unconscious selection. It is almost necessary that a large
number of individuals should be reared; for thus there will be a fair
chance of variations of the desired nature arising, and every individu