It was
impossible to behold these three plants, with their blackened, withered,
and dead brethren all around them, and not see at a glance that they
differed widely in their constitutional power of resisting frost."
The preceding sketch of the variation that occurs among domestic animals
and cultivated plants shows how wide it is in range and how great in
amount; and we have good reason to believe that similar variation
extends to all organised beings. In the class of fishes, for example, we
have one kind which has been long domesticated in the East, the gold
and silver carps; and these present great variation, not only of colour
but in the form and structure of the fins and other external organs. In
like manner, the only domesticated insects, hive bees and silkworm
moths, present numbers of remarkable varieties which have been produced
by the selection of chance variations just as in the case of plants and
the higher animals.
_Circumstances favourable to Selection by Man._
It may be supposed, that the systematic selection which has been
employed for the purpose of improving the races of animals or plants
useful to man is of comparatively recent origin, though some of the
different races are known to have been in existence in very early times.
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