See page in:
1859
1860
1861
1866
1869
1872

Compare with:
1860
1861
1866
1869
1872

species. 1859 1860 1861 1866
species when crossed. 1869 1872

varieties does not seem to me sufficient to overthrow the view which I have taken with respect to the very general, but not invariable, sterility of first crosses and of hybrids, namely, that it is not 1859 1860
varieties, considering how entirely ignorant we are on the causes of both fertility and sterility, does not seem to me sufficient to overthrow the view taken with respect to the very general, but not invariable, sterility of first crosses between species and of their hybrids, namely, that it is not 1861 1866
crossed species may safely be looked at not as 1869
crossed species may safely be looked at, not as 1872

endowment, but is 1859 1860 1861 1866
acquirement or endowment, but as 1869 1872

slowly acquired modifications, more especially in the reproductive systems of the forms which are crossed. 1859 1860 1861
modifications, slowly impressed, by unknown means, on the reproductive systems of the parent-forms. 1866
changes of an unknown nature in their sexual elements. 1869 1872

compared, 1859 1860
compared , 1861
compared, 1866 1869
compared , 1872

is 1859 1860 1861 1866
in both cases is 1869 1872

a fundamental distinction between
them
varieties
and species. The general
sterility
fertility
of varieties does not seem to me sufficient to overthrow the view which I have taken with respect to the very general, but not invariable, sterility of first crosses and of hybrids, namely, that it is not a special endowment, but is incidental on slowly acquired modifications, more especially in the reproductive systems of the forms which are crossed.
Hybrids
Hybrids
and
and
Mongrels
Mongrels
compared,
independently
independently
of
of
their
their
fertility .
fertility .
fertility .
fertility .—
Independently of the question of fertility, the offspring of species
when crossed
when crossed
and of varieties when crossed may be compared in several other respects. Gärtner, whose strong wish
it was
was
to draw a
distinct
marked
line
of distinction
of distinction
between species and varieties, could find very
few,
few
and, as it seems to me, quite unimportant differences between the so-called hybrid offspring of species, and the so-called mongrel offspring of varieties. And, on the other hand, they agree most closely in
very
very
many important respects.
I shall here discuss this subject with extreme brevity. The most important distinction is, that in the first generation mongrels are more variable than hybrids; but Gärtner admits that hybrids from species which have long been cultivated are often variable in the first generation; and I have myself seen striking instances of this fact. Gärtner further admits that hybrids between very closely allied species are more variable than those from very distinct species; and this shows that the difference in the degree of variability graduates away. When mongrels and the more fertile hybrids are propagated for several
generations,
generations
an extreme amount of variability in
the
their
offspring is
notorious;
notori- ous;