Gartner, whose strong wish was to draw a marked line
of distinction between species and varieties, could find very 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
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 Gartner 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. Gartner 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 an extreme amount of variability in their
offspring is notorious; but some few cases both of hybrids and
mongrels long retaining uniformity of character could be given. The
variability, however, in the successive generations of mongrels is,
perhaps, greater than in hybrids.
This greater variability of mongrels than of hybrids does not seem to
me at all surprising. For the parents of mongrels are varieties, and
mostly domestic varieties (very few experiments having been tried on
natural varieties), and this implies in most cases that there has been
recent variability; and therefore we might expect that such
variability would often continue and be super-added to that arising
from the mere act of crossing.
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