Comparison with 1872 |
|
often, in some degree, intermediate in character between existing groups; and we can understand this fact, for the extinct species lived at
various remote various remote 1872 | very ancient 1859 1860 1861 1866 1869 |
epochs when the branching lines of descent had diverged less. |
|
I see no reason to limit the process of modification, as now explained, to the formation of genera alone. If, in
the the 1869 1872 | our 1859 1860 1861 1866 |
diagram, we suppose the amount of change represented by each successive group of diverging dotted lines to be
....... 1869 1872 | very 1859 1860 1861 1866 |
great, the forms marked
a
14
to
p
14
, those
marked
b
14
and
f
14
, and
those marked
o
14
to
m
14
, will
form three very distinct genera. We shall also have two very distinct genera descended from
(I), (I), 1869 1872 | (I); 1859 1860 1861 1866 |
differing differing 1869 1872 |
and as these latter two genera, both from continued divergence of character and from inheritance from a different parent, will differ 1859 1860 1861 1866 |
widely from the
descendants of (A). These two descendants of (A). These two 1869 1872 |
three genera descended from (A), the two little 1859 1860 1861 1866 |
groups of genera will
thus form thus form 1869 1872 | form 1859 1860 1861 1866 |
two distinct families, or
....... 1869 1872 | even 1859 1860 1861 1866 |
orders, according to the amount of divergent modification supposed to be represented in the diagram. And the two new families, or orders,
are are 1869 1872 | will have 1859 1860 1861 1866 |
descended from two species of the original
genus, genus, 1869 1872 | genus; 1859 1860 1861 1866 |
and these
....... 1869 1872 | two species 1859 1860 1861 1866 |
are supposed to
be be 1869 1872 | have 1859 1860 1861 1866 |
descended from
some some 1869 1872 |
one species of a 1859 1860 1861 1866 |
still more ancient and unknown
form. form. 1869 1872 | genus. 1859 1860 1861 1866 |
|
|
We have seen that in each country it is the species
belonging to belonging to 1869 1872 | of 1859 1860 1861 1866 |
the larger genera which oftenest present varieties or incipient species. This, indeed, might have been expected;
for, for, 1872 | for 1859 1860 1861 1866 1869 |
as natural selection acts through one form having some advantage over other forms in the struggle for existence, it will chiefly act on those which already have some advantage; and the largeness of any group shows that its species have inherited from a common ancestor some advantage in common. Hence, the struggle for the production of new and modified descendants,
will mainly lie between the larger groups,
which are all trying to increase in number. One large group will slowly conquer another large group,
|
often, in some degree, intermediate in character between existing groups; and we can understand this fact, for the extinct species lived at
very ancient very ancient 1859 1860 1861 1866 1869 | various remote 1872 |
epochs when the branching lines of descent had diverged less. |
|
I see no reason to limit the process of modification, as now explained, to the formation of genera alone. If, in
our our 1859 1860 1861 1866 | the 1869 1872 |
diagram, we suppose the amount of change represented by each successive group of diverging dotted lines to be
very very 1859 1860 1861 1866 | very 1869 1872 |
great, the forms marked
a
14
to
p
14
,
p
14
,
1859 1861 1866 1869 1872 |
p
14
1860 |
those those 1859 1861 1866 1869 1872 | , those 1860 |
marked
b
14
and
f
14
,
f
14
,
1859 1861 1866 1869 1872 |
f
14
1860 |
and and 1859 1861 1866 1869 1872 | , and 1860 |
those marked
o
14
to
m
14
,
m
14
,
1859 1861 1866 1869 1872 |
m
14
1860 |
will will 1859 1861 1866 1869 1872 | , will 1860 |
form three very distinct genera. We shall also have two very distinct genera descended from
(I); (I); 1859 1860 1861 1866 | (I), 1869 1872 |
and as these latter two genera, both from continued divergence of character and from inheritance from a different parent, will differ and as these latter two genera, both from continued divergence of character and from inheritance from a different parent, will differ 1859 1860 1861 1866 |
differing 1869 1872 |
widely from the
three genera descended from (A), the two little three genera descended from (A), the two little 1859 1860 1861 1866 |
descendants of (A). These two 1869 1872 |
groups of genera will
form form 1859 1860 1861 1866 | thus form 1869 1872 |
two distinct families, or
even even 1859 1860 1861 1866 | even 1869 1872 |
orders, according to the amount of divergent modification supposed to be represented in the diagram. And the two new families, or orders,
will have will have 1859 1860 1861 1866 | are 1869 1872 |
descended from two species of the original
genus; genus; 1859 1860 1861 1866 | genus, 1869 1872 |
and these
two species two species 1859 1860 1861 1866 | two species 1869 1872 |
are supposed to
have have 1859 1860 1861 1866 | be 1869 1872 |
descended from
one species of a one species of a 1859 1860 1861 1866 |
some 1869 1872 |
still more ancient and unknown
genus. genus. 1859 1860 1861 1866 | form. 1869 1872 |
|
|
We have seen that in each country it is the species
of of 1859 1860 1861 1866 | belonging to 1869 1872 |
the larger genera which oftenest present varieties or incipient species. This, indeed, might have been expected;
for for 1859 1860 1861 1866 1869 | for, 1872 |
as natural selection acts through one form having some advantage over other forms in the struggle for existence, it will chiefly act on those which already have some advantage; and the largeness of any group shows that its species have inherited from a common ancestor some advantage in common. ↑1 blocks not present in 1861; present in 1859 1860 1866 1869 1872 | Hence, the struggle for the production of new and modified descendants,
will mainly lie between the larger groups,
which are all trying to increase in number.
|
One large group will slowly conquer another large group,
|