| ↑ 1 blocks not present in 1872; present in 1859 1860 1861 1866 1869 |
| Hence we now positively know that sessile cirripedes existed during the secondary period; and these cirripedes might have been the progenitors of our many tertiary and existing species.
|
|
| → according to Agassiz, in 1872 |
| in 1859 1860 1861 1866 1869 |
|
| → considerations, 1869 1872 |
| and similar considerations, but chiefly 1859 1860 1861 1866 |
|
| → knowledge effected by 1869 1872 |
| ideas on many points, which 1859 1860 1861 1866 |
|
| → species belonging to several 1872 |
| numbers of species 1859 1860 1861 1866 |
| many species in several 1869 |
|
| → main divisions of the animal kingdom 1869 1872 |
| same group, 1859 1860 1861 |
| same group 1866 |
|
|
have abundant evidence of the existence of this group of animals during the secondary period. ↑
|
|
| The case most frequently insisted on by palæontologists of the apparently sudden appearance of a whole group of species, is that of the teleostean fishes, low
→according to Agassiz, in
the Chalk period. This group includes the large majority of existing species. But certain Jurassic and Triassic forms are now commonly admitted to be teleostean; and even some palæozoic forms have thus been classed by one high authority. If the teleosteans had really appeared suddenly in the northern hemisphere at the commencement of the chalk formation, the fact would have been highly remarkable; but it would not have formed an insuperable difficulty, unless it could likewise have been shown that at the same period the species were suddenly and simultaneously developed in other quarters of the world. It is almost superfluous to remark that hardly any fossil-fish are known from south of the equator; and by running through
Palæontology it will be seen that very few species are known from several formations in Europe. Some few families of fish now have a confined range; the teleostean
might formerly have had a similarly confined range, and after having been largely developed in some one sea,
have spread widely. Nor have we any right to suppose that the seas of the world have always been so freely open from south to north as they are at present. Even at this day, if the Malay Archipelago were converted into land, the tropical parts of the Indian Ocean would form a large and perfectly enclosed basin, in which any great group of marine animals might be multiplied; and here they would remain confined, until some of the species became adapted to a cooler climate, and were enabled to double the
capes of Africa or Australia, and thus reach other and distant seas. |
|
| From these
→considerations,
from our ignorance of the geology of other countries beyond the confines of Europe and the United
and from the revolution in our palæontological
→knowledge effected by
the discoveries of
the last dozen
it seems to me to be about as rash
to dogmatize on the succession of organic
throughout the world, as it would be for a naturalist to land for five minutes on
barren point in Australia, and then to discuss the number and range of its productions. |
|
|
| There is another and allied difficulty, which is much
I allude to the manner in which
→species belonging to several
of the
→main divisions of the animal kingdom
|
