eties from the same stock,
adapted to two climates or to other different external conditions,
and confines each rigidly for one or several thousand years to such
conditions, always selecting the individuals best adapted to them,
he cannot be said to have even commenced the experiment." That is,
the attempt to produce mutually sterile domestic breeds.

{81} This passage is to some extent a repetition of a previous one
and may have been intended to replace an earlier sentence. I have
thought it best to give both. In the _Origin_, Ed. i. p. 141, vi.
p. 176, the author gives his opinion that the power of resisting
diverse conditions, seen in man and his domestic animals, is an
example "of a very common flexibility of constitution."

Before leaving this subject well to observe that it was shown that a
certain amount of variation is consequent on mere act of reproduction,
both by buds and sexually,--is vastly increased when parents exposed for
some generations to new conditions{82}, and we now find that many
animals when exposed for first time to very new conditions, are <as>
incapable of breeding as hybrids. It [probably] bears also on supposed
fact of crossed animals when not infertile, as in mongrels, tending to
vary much, as likewise seems to be the case, when true hybrids possess
just sufficient fertility to propagate with the parent breeds and _inter
se_ for some generations. This is Koelreuter's belief. These facts throw
light on each other and support the truth of each other, we see
throughout a connection between the reproductive faculties and exposure
to changed conditions of life whether by crossing or exposure of the
individuals{83}.

{82} In the _Origin_, Ed. i. Chs. I. and V., the author does not
admit reproduction, apart from environment, as being a cause of
variation. With regard to the cumulative effect of new conditions
there are many passages in the _Origin_, Ed. i. e.g. pp. 7, 12, vi.
pp. 8, 14.

{83} As already pointed out, this is the important principle
investigated in the author's _Cross and Self-Fertilisation_.
Professor Bateson has suggested to me that the experiments should
be repeated with gametically pure individuals.

_Difficulties on theory of selection_{84}. It may be objected such
perfect organs as eye and ear, could never be formed, in latter less
difficulty as gradations more perfect; at