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See page in:
1859
1860
1861
1866
1869
1872

Compare with:
1859
1860
1861
1866
1872

→ Crossed, 1866 1869
crossed, 1859
crossed , 1860 1861
Crossed , 1872
→ Offspring . 1866 1869
offspring .— 1859 1860 1861
Offspring , not universal . 1872
→ an overwhelming 1869 1872
a most forcible 1859 1860 1861 1866
→ OMIT 1869 1872
and that there must be some error in all the foregoing remarks, 1859 1860 1861 1866
→ the 1866 1869 1872
very generally the 1861
→ But the subject is surrounded by difficulties, for, looking to varieties, produced under nature, if two forms hitherto reputed to be varieties be found in any degree sterile together, they are at once ranked by most naturalists as species. 1869
I fully admit that this is almost invariably the case. 1859 1860
↑ 1 blocks not present in 1869; present in 1859 1860 1861 1866 1872
But if we look to varieties produced under nature, we are immediately involved in hopeless difficulties; for if two hitherto reputed varieties be found in any degree sterile together, they are at once ranked by most naturalists as species.
→ OMIT 1866 1869 1872
the primrose and cowslip, 1859 1860 1861
→ most 1866 1869 1872
many of our best 1859 1860 1861
→ the German Spitz dog crosses more easily with the fox than do other dogs, or that 1866 1869
the German Spitz dog unites more easily than other dogs with foxes, or that 1859 1860 1861
OMIT 1872
→ these dogs are 1869
these dogs have 1859 1860 1861 1866
they are 1872
Fertility
Fertility
of
of
Varieties
Varieties
when
when
→ Crossed,
and
and
of
of
their
their
Mongrel
Mongrel
→ Offspring .
It may be urged, as →an overwhelming
argu- ment,
argument,
that there must be some essential distinction between species and varieties, →OMIT inasmuch as
varieties,
the latter,
however much they may differ from each other in external appearance, cross with perfect facility, and yield perfectly fertile offspring. With some exceptions, presently to be given, I fully admit that this is →the rule. →But the subject is surrounded by difficulties, for, looking to varieties, produced under nature, if two forms hitherto reputed to be varieties be found in any degree sterile together, they are at once ranked by most naturalists as species. ↑ For instance, the blue and red pimpernel, →OMIT which are considered by →most botanists as varieties, are said by Gärtner
not
not
to be quite
sterile
fertile
when crossed, and he consequently ranks them as undoubted species. If we thus argue in a circle, the fertility of all varieties produced under nature will assuredly have to be granted.
If we turn to varieties, produced, or supposed to have been produced, under domestication, we are still
in- volved
involved
in
some doubt.
doubt.
For when it is stated, for instance, that →the German Spitz dog crosses more easily with the fox than do other dogs, or that certain South American indigenous domestic dogs do not readily
cross
unite
with European dogs, the explanation which will occur to every one, and probably the true one, is that →these dogs are descended from
several
....
aboriginally distinct species. Nevertheless the perfect fertility of so many domestic
races,
varieties,
differing widely from each other in appearance, for instance
of
those of
the
pigeon
pigeon,
or
of
of
the cabbage, is a remarkable fact; more especially when we reflect how many species there are, which, though resembling each