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within each class thus 1861 1866 1869 1872
thus 1859 1860

spread they are 1859 1860 1861 1866
they are spread 1869 1872

A few 1859 1860 1861 1866
Some few 1869
As some few of the 1872

old 1859 1860 1861 1866 1872
of these old 1869

parent-forms having occasionally 1859 1860 1861 1866
forms having 1869
forms have 1872

will give to us 1859 1860 1861 1866
constitute 1869
these constitute 1872

on my theory 1859 1860 1861 1866
OMIT 1869 1872

On the Nature of the Affinities connecting Organic Beings .—
As the modified descendants of dominant
species
species,
belonging to the larger genera, tend to inherit the
advantages,
advantages
which made the groups to which they belong large and their parents dominant, they are almost sure to spread widely, and to seize on more and more places in the economy of nature. The larger and more dominant groups within each class thus tend to go on increasing in size; and they consequently supplant many smaller and feebler groups. Thus we can account for the fact that all organisms, recent and extinct, are included under a few great orders,
and under
under
still fewer
classes.
classes,
and
and
all
all
in
in
one
one
great
great
natural
natural
system.
system.
As showing how few the higher groups are in number, and how widely spread they are throughout the world, the fact is
striking
striking,
that the discovery of Australia has not added
a single
an
insect belonging to a new
order;
class;
and that in the vegetable kingdom, as I learn from Dr. Hooker, it has added only two or three
orders
families
of small size.
In the chapter on
geological
Geological
succession
Succession
I attempted to show, on the principle of each group having generally diverged much in character during the long-continued process of modification, how it is that the more ancient forms of life often present characters in some
slight
slight
degree intermediate between existing groups. A few old and intermediate parent-forms having occasionally transmitted to the present day descendants but little modified, will give to us our so-called osculant or aberrant
species.
groups.
The more aberrant any form is, the greater must be the number of connecting forms which on my theory have been exterminated and utterly lost. And we have some evidence of aberrant
groups
forms
having suffered severely from extinction, for they are
almost always
generally
represented by extremely few species; and such species as do occur are generally very distinct from