| ↑ 3 blocks not present in 1859 1860 1861 1866 1869; present in 1872 |
| It should be observed that the process of imitation probably never commenced between forms widely dissimilar in colour.
But starting with species already somewhat like each other, the closest resemblance, if beneficial, could readily be gained by the above means; and if the imitated form was subsequently and gradually modified through any agency, the imitating form would be led along the same track, and thus be altered to almost any extent, so that it might ultimately assume an appearance or colouring wholly unlike that of the other members of the family to which it belonged.
There is, however, some difficulty on this head, for it is necessary to suppose in some cases that ancient members belonging to several distinct groups, before they had diverged to their present extent, accidentally resembled a member of another and protected group in a sufficient degree to afford some slight protection, this having given the basis for the subsequent acquisition of the most perfect resemblance.
|
|
| ←Subtitle not present 1859 1860 1861
On
the
Nature
of
the
Affinities
connecting
Organic
Beings
.— 1872 |
| → within each class thus 1861 1866 1869 1872 |
| thus 1859 1860 |
|
| → spread they are 1859 1860 1861 1866 |
| they are spread 1869 1872 |
|
|
As members of distinct classes have often been adapted by successive slight modifications to live under nearly similar circumstances,— to
for
the three elements of land, air, and water,— we can perhaps understand how it is that a numerical
has sometimes been observed between the sub-groups in distinct classes. A naturalist, struck by a parallelism of this nature in any one class, by arbitrarily raising or sinking the value of the groups in other classes (and all our experience shows that this valuation has hitherto been arbitrary), could easily extend the parallelism over a wide range; and thus the septenary, quinary, quaternary, and ternary classifications have probably arisen. ↑ →
|
| As the modified descendants of dominant
belonging to the larger genera, tend to inherit the
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,
still fewer
As showing how few the higher groups are in number, and how widely
→spread they are
throughout the world, the fact is
that the discovery of Australia has not added
insect belonging to a new
and that in the vegetable kingdom, as I learn from Dr. Hooker, it has added only two or three
of small size. |
|
| In the chapter on
I attempted to show, on the principle of each group having generally diverged much in character during the long-continued
|
