have abundant evidence of the existence of this group of animals during the secondary period. ↑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.
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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
down, down, 1872 | down 1859 1860 1861 1866 1869 |
according to Agassiz, in according to Agassiz, in 1872 |
in 1859 1860 1861 1866 1869 |
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
Pictet's Pictet's 1859 1860 1861 1866 1872 | Pictets 1869 |
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
fishes fishes 1872 | fish 1859 1860 1861 1866 1869 |
might formerly have had a similarly confined range, and after having been largely developed in some one sea,
....... 1872 | might 1859 1860 1861 1866 1869 |
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
Southern Southern 1872 | southern 1859 1860 1861 1866 1869 |
capes of Africa or Australia, and thus reach other and distant seas. |
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From these
considerations, considerations, 1869 1872 |
and similar considerations, but chiefly 1859 1860 1861 1866 |
from our ignorance of the geology of other countries beyond the confines of Europe and the United
States, States, 1869 1872 | States; 1859 1860 1861 1866 |
and from the revolution in our palæontological
knowledge effected by knowledge effected by 1869 1872 |
ideas on many points, which 1859 1860 1861 1866 |
the discoveries of
....... 1869 1872 | even 1859 1860 1861 1866 |
the last dozen
years, years, 1869 1872 | years 1859 1860 1861 1866 |
....... 1869 1872 | have effected, 1859 1860 1861 1866 |
it seems to me to be about as rash
....... 1869 1872 | in us 1859 1860 1861 1866 |
to dogmatize on the succession of organic
forms forms 1869 1872 | beings 1859 1860 1861 1866 |
throughout the world, as it would be for a naturalist to land for five minutes on
a a 1869 1872 | some one 1859 1860 1861 1866 |
barren point in Australia, and then to discuss the number and range of its productions. |
On
On
1866 1869 1872 |
On
1859 1860 1861 |
the
the
1866 1869 1872 |
the
1859 1860 1861 |
sudden
sudden
1866 1869 1872 |
sudden
1859 1860 1861 |
Appearance
Appearance
1866 1869 1872 |
appearance
1859 1860 1861 |
of
of
1866 1869 1872 |
of
1859 1860 1861 |
Groups
Groups
1866 1869 1872 |
groups
1859 1860 1861 |
of
of
1866 1869 1872 |
of
1859 1860 1861 |
allied
allied
1866 1869 1872 |
Allied
1859 1860 |
allied
1861 |
Species
Species
1866 1869 1872 |
Species
1859 1860 1861 |
in
in
1866 1869 1872 |
in
1859 1860 1861 |
the
the
1866 1869 1872 |
the
1859 1860 1861 |
lowest
lowest
1866 1869 1872 |
lowest
1859 1860 1861 |
known
known
1866 1869 1872 |
known
1859 1860 1861 |
Fossiliferous
Fossiliferous
1866 1869 1872 |
fossiliferous
1859 1860 1861 |
Strata
.
Strata
. 1866 1869 1872 |
strata
.—
1859 1860 1861 |
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There is another and allied difficulty, which is much
more serious. more serious. 1866 1869 1872 | graver. 1859 1860 1861 |
I allude to the manner in which
species belonging to several species belonging to several 1872 |
numbers of species 1859 1860 1861 1866 |
many species in several 1869 |
of the
main divisions of the animal kingdom main divisions of the animal kingdom 1869 1872 |
same group, 1859 1860 1861 |
same group 1866 |
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