See page in:
1859
1860
1861
1866
1869
1872

Compare with:
1859
1860
1866
1869
1872

of an important part varying will ever be found: 1859 1860 1861
will ever be found of an important part varying: 1866 1869
will ever be found of an important part varying; 1872

is 1861 1866 1869 1872
seems to me 1859 1860

hardly 1859 1860 1861 1866
about which hardly 1869
OMIT 1872

as species and which 1859 1860 1861 1866
OMIT 1872
them as species or 1869

1 blocks not present in 1859 1860 1861 1866 1869; present in 1872
With respect to many of these forms, hardly two naturalists agree whether to rank them as species or as varieties.

and several genera of Brachiopod shells. 1859 1860 1861
several genera of Brachiopod shells, and the Ruff (Machetes pugnax) amongst birds. 1866 1869
and of Brachiopod shells. 1872

are 1861 1866 1869 1872
seem to be 1859 1860

see in 1859 1860 1861 1866
have at least in some of 1869
see, at least in some of 1872

in points of structure 1859 1860 1861 1866
OMIT 1869 1872

←Subtitle not present 1859 1860 1861 Doubtful Species. 1866 1869
I may add, has also
recently
quite recently
quite recently
shown that the muscles in the larvæ of certain insects are
very
very
far from uniform. Authors sometimes argue in a circle when they state that important organs never vary; for these same authors practically rank
those parts
that character
as important (as some few naturalists have honestly confessed) which
do
does
not vary; and, under this point of view, no instance of an important part varying will ever be found: but under any other point of view many instances assuredly can be given.
There is one point connected with individual differences, which is extremely perplexing: I refer to those genera which have
sometimes
sometimes
been called "protean" or "polymorphic," in which the species present an inordinate amount of
variation.
variation;
and
and
hardly
two
two
naturalists
naturalists
can
can
can
agree
agree
which forms
whether
which forms
to
to
rank
rank
as species and which
as
as
varieties.
varieties.
We may instance Rubus, Rosa, and Hieracium amongst plants, several genera of
insects
insects,
and several genera of Brachiopod shells. In most polymorphic genera some of the species have fixed and definite characters. Genera which are polymorphic in one country seem to be, with
a
some
few exceptions, polymorphic in other countries, and likewise, judging from Brachiopod shells, at former periods of time. These facts are very perplexing, for they seem to show that this kind of variability is independent of the conditions of life. I am inclined to suspect that we see in these polymorphic
genera,
genera
variations in points of structure which are of no service or disservice to the species, and which consequently have not been seized on and rendered definite by natural selection, as hereafter
to
will
be explained.
The
Those
forms which possess in some considerable degree the character of species, but which are so closely similar to
some
some
other forms, or are so closely linked to them by intermediate gradations, that naturalists do not