| ↑ 5 blocks not present in 1860 1861 1866 1869 1872; present in 1859 |
| But it may be asked, what ought we to do, if it could be proved that one species of kangaroo had been produced, by a long course of modification, from a bear?
Ought we to rank this one species with bears, and what should we do with the other species?
The supposition is of course preposterous; and I might answer by the
argumentum
ad
hominem
,
and ask what should be done if a perfect kangaroo were seen to come out of the womb of a bear?
According to all analogy, it would be ranked with bears; but then assuredly all the other species of the kangaroo family would have to be classed under the bear genus.
The whole case is preposterous; for where there has been close descent in common, there will certainly be close resemblance or affinity.
|
|
| → though in these cases the modification has been greater in degree, and has taken a longer time to complete? 1859 1860 1861 |
| though in these cases the modification has been much greater in degree, and has taken a longer time to complete? 1866 |
| all under the so-called natural system? 1869 1872 |
|
| → have to make out 1859 1860 1861 1866 1869 |
| are forced to trace 1872 |
|
| → as far as we can judge, 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
|
been ranked as three distinct genera, were known to be sometimes produced on the same spike, they were immediately included as a single species. ↑ |
|
| As descent has universally been used in classing together the individuals of the same species, though the males and females and larvæ are sometimes extremely different; and as it has been used in classing varieties which have undergone a certain, and sometimes a considerable amount of modification, may not this same element of descent have been unconsciously used in grouping species under genera, and genera under higher groups,
→though in these cases the modification has been greater in degree, and has taken a longer time to complete? I believe it has
been unconsciously used; and
can I understand the several rules and guides which have been followed by our best systematists.
have no written
we
→have to make out
community of descent by resemblances of any kind. Therefore we choose those characters
→as far as we can judge,
are the least likely to have been
in relation to the conditions of life to which each species has been recently exposed. Rudimentary structures on this view are as good as, or even sometimes better than, other parts of the organisation. We care not how trifling a character may be— let it be the mere inflection of the angle of the jaw, the manner in which an
wing is folded, whether the skin be covered by hair or feathers— if it prevail throughout many and different species, especially those having very different habits of life, it assumes high value; for we can account for its presence in so many forms with such different habits, only by
inheritance from a common parent. We may err in this respect in regard to single points of structure, but when several characters, let them be ever so trifling,
throughout a
|
