| Comparison with 1859 |
|
|
with slightly different grades of difference, have been subsequently discovered. |
|
| All the foregoing rules and aids and difficulties in classification are
explained, if I do not greatly deceive myself, on the view that the natural
system
is founded on descent with modification;
that the characters which naturalists consider as showing true affinity between any two or more species, are those which have been inherited from a common parent, and, in so far,
all true classification is
genealogical;
that community of descent is the hidden bond which naturalists have been unconsciously seeking, and not some unknown plan of creation, or the enunciation of general propositions, and the mere putting together and separating objects more or less alike. |
|
| But I must explain my meaning more fully. I believe that the
arrangement
of the groups within each class, in due subordination and relation to the
other
groups,
must be strictly genealogical in order to be natural; but that the
amount
of difference in the several branches or groups, though allied in the same degree in blood to their common progenitor, may differ greatly, being due to the different degrees of modification which they have undergone; and this is expressed by the forms being ranked under different genera, families, sections, or orders. The reader will best understand what is meant, if he will take the trouble of referring
to the diagram in the fourth chapter. We will suppose the letters A to L to represent allied genera, which lived
during the Silurian epoch,
and these have
descended from a species which existed at an unknown anterior period.
Species of
three of these genera (A, F, and I) have
transmitted modified descendants to the present day, represented by the fifteen genera
(
a
14 |
|
with slightly different grades of difference, have been subsequently discovered. |
|
All the foregoing rules and aids and difficulties in classification
are | are 1859 1860 1861 1866 1869 | | may be 1872 |
| natural 1859 1860 1861 1866 | | Natural 1869 1872 |
| system 1859 1860 1861 1866 | | System 1869 1872 |
| modification; 1859 1860 1861 | | modification;— 1866 1869 1872 |
| and, in so far, 1859 1860 1861 |
| and in so far, 1866 |
| OMIT 1869 1872 |
| is 1859 1860 1861 1866 | | being 1869 1872 |
| genealogical; 1859 1860 1861 | | genealogical;— 1866 1869 1872 |
|
|
But I must explain my meaning more fully. I believe that the
arrangement
of the groups within each class, in due subordination and relation to
the | the 1859 1860 1861 1866 | | each 1869 1872 |
| other 1859 1860 1861 1866 | | other, 1869 1872 |
| groups, 1859 1860 1861 1866 | groups, 1869 1872 |
| of referring 1859 1860 1861 | | to refer 1866 1869 1872 |
| allied genera, which lived 1859 1860 1861 1866 |
| allied genera existing 1872 |
| OMIT 1869 |
| epoch, 1859 1860 1861 1866 1872 | | epoch 1869 |
| and these have 1859 1860 1861 1866 |
| allied genera, 1869 |
| and 1872 |
| a species which existed at an unknown anterior period. 1859 1860 1861 1866 |
| some still earlier forms. 1869 |
| some still earlier form. 1872 |
| Species of 1859 1860 1861 1866 | | In 1869 1872 |
| I) have 1859 1860 1861 1866 |
| I) the species have 1869 |
| I), a species has 1872 |
|
