here these notes were meant to go.>

It is worthy of remark, that as many organic beings, when taken by man
out of their natural conditions, have their reproductive system <so>
affected as to be incapable of propagation, so, we saw in the first
chapter, that although organic beings when taken by man do propagate
freely, their offspring after some generations vary or sport to a degree
which can only be explained by their reproductive system being <in> some way
affected. Again, when species cross, their offspring are generally
sterile; but it was found by Koelreuter that when hybrids are capable of
breeding with either parent, or with other species, that their
offspring are subject after some generations to excessive
variation{258}. Agriculturists, also, affirm that the offspring from
mongrels, after the first generation, vary much. Hence we see that both
sterility and variation in the succeeding generations are consequent
both on the removal of individual species from their natural states and
on species crossing. The connection between these facts may be
accidental, but they certainly appear to elucidate and support each
other,--on the principle of the reproductive system of all organic
beings being eminently sensitive to any disturbance, whether from
removal or commixture, in their constitutional relations to the
conditions to which they are exposed.

{258} _Origin_, Ed. i. p. 272, vi. p. 404.

_Points of Resemblance between "Races" and "Species{259}."_

{259} This section seems not to correspond closely with any in the
_Origin_, Ed. i.; in some points it resembles pp. 15, 16, also the
section on analogous variation in distinct species, _Origin_, Ed.
i. p. 159, vi. p. 194.

Races and reputed species agree in some respects, although differing
from causes which, we have seen, we can in some degree understand, in
the fertility and "trueness" of their offspring. In the first place,
there is no clear sign by which to distinguish races from species, as is
evident from the great difficulty experienced by naturalists in
attempting to discriminate them. As far as external characters are
concerned, many of the races which are descended from the same stock
differ far more than true species of the same genus; look at the
willow-wrens, some of which skilful ornithologists can hardly
distinguish from each other except by their nests; look at the wild
swans, and compare the distinct species of these gen