arieties of any one species are the descendants of that species.
Furthermore, I am also convinced that Natural Selection has been the
most important, but not the exclusive, means of modification.

_II.--Variation and Selection_

All living beings vary more or less from one another, and though
variations which are not inherited are unimportant for us, the number
and diversity of inheritable deviations of structure, both those of
slight and those of considerable physiological importance, are endless.

No breeder doubts how strong is the tendency to inheritance; that like
produces like is his fundamental belief. Doubts have been thrown on
this principle only by theoretical writers. When any deviation of
structure often appears, and we see it in the father and child, we
cannot tell whether it may not be due to the same cause having acted on
both; but when amongst individuals, apparently exposed to the same
conditions, any very rare deviation, due to some extraordinary
combination of circumstances, appears in the parent--say, once amongst
several million individuals--and it re-appears in the child, the mere
doctrine of chances almost compels us to attribute its reappearance to
inheritance.

Everyone must have heard of cases of albinism, prickly skin, hairy
bodies, etc., appearing in members of the same family. If strange and
rare deviations of structure are really inherited, less strange and
commoner deviations may be freely admitted to be inheritable. Perhaps
the correct way of viewing the whole subject would be to look at the
inheritance of every character whatever as the rule, and non-inheritance
as the anomaly.

The laws governing inheritance are for the most part unknown. No one can
say why the same peculiarity in different individuals of the same
species, or in different species, is sometimes inherited and sometimes
not so; why the child often reverts in certain characters to its
grandfather or grandmother, or more remote ancestor; why a peculiarity
is often transmitted from one sex to both sexes, or to one sex alone,
more commonly but not exclusively to the like sex.

The fact of heredity being given, we have evidence derived from human
practice as to the influence of selection. There are large numbers of
domesticated races of animals and plants admirably suited in various
ways to man's use or fancy--adapted to the environment of which his need
and inclination are the most essential constituents. We cannot sup