from this capacity as an almost necessary consequence. We can here consider only a few
cases. | cases. 1859 1860 1861 1866 1869 |
| cases; of these, some of the most difficult to explain are presented by fish. 1872 |
| 8 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | | It was formerly believed that the same fresh-water species never existed on two continents distant from each other.
But Dr. Günther has lately shown that the Galaxias attenuatus inhabits Tasmania, New Zealand, the Falkland Islands, and the mainland of South America.
This is a wonderful case, and probably indicates dispersal from an Antarctic centre during a former warm period.
This case, however, is rendered in some degree less surprising by the species of this genus having the power of crossing by some unknown means considerable spaces of open ocean: thus there is one species common to New Zealand and to the Auckland Islands, though separated by a distance of about 230 miles.
On the same continent fresh-water fish often range widely, and as if capriciously; for in two adjoining river-systems some of the species may be the same, and some wholly different.
It is probable that they are occasionally transported by what may be called accidental means.
Thus fishes still alive are not very rarely dropped at distant points by whirlwinds; and it is known that the ova retain their vitality for a considerable time after removal from the water.
Their dispersal may, however, be mainly attributed to changes in the level of the land within the recent period, causing rivers to flow into each other.
|
| ..... 1869 | | slight 1859 1860 1861 1866 |
| in 1869 | | within 1859 1860 1861 1866 |
| OMIT 1869 |
| recent period in the 1859 1860 1861 1866 |
| land 1869 | | land, 1859 1860 1861 1866 |
| within the recent period, having 1869 |
| having 1859 1860 1861 1866 |
| 1 blocks not present in 1869 1872; present in 1859 1860 1861 1866 | | We have evidence in the loess of the Rhine of considerable changes of level in the land within a very recent geological period, and when the surface was peopled by existing land and fresh-water shells.
|
| the opposite 1869 1872 | | opposite 1859 1860 1861 1866 |
| continuous 1859 1860 1861 1866 1869 | | most 1872 |
| from 1859 1860 1861 1866 1869 |
| are continuous, and which consequently must from 1872 |
| must 1859 1860 1861 1866 1869 | must 1872 |
| OMIT 1869 1872 |
| parted river-systems and 1859 1860 1861 1866 |
| the 1869 1872 | | their 1859 1860 1861 1866 |
| inosculation 1869 1872 | | inosculation, 1859 1860 1861 1866 |
| of the river-systems, seems to 1869 |
| seems to 1859 1860 1861 1866 |
| of the river-systems on the two sides, 1872 |
| lead 1859 1860 1861 1866 1869 | | leads 1872 |
| the 1869 1872 | | this 1859 1860 1861 1866 |
| With respect to allied 1859 1860 1861 1866 1869 |
| Some 1872 |
| occurring at very distant points of the world, no doubt there, are many cases which cannot at present be explained: but some fresh-water fish 1869 |
| occurring at very distant points of the world, no doubt there are many cases which cannot at present be explained: but some fresh-water fish 1859 1860 1861 1866 |
| OMIT 1872 |
| In the second place, 1859 1860 1861 1866 1869 |
| OMIT 1872 |
| salt-water 1859 1860 1861 1866 1869 | | Salt-water 1872 |
| which all the members are confined exclusively 1869 |
| fishes confined exclusively 1859 1860 1861 1866 |
| which all the members are confined 1872 |
| OMIT 1869 1872 |
| we may imagine that 1859 1860 1861 1866 |
| species of 1869 |
| member of 1859 1860 1861 1866 |
| species belonging to 1872 |
| subsequently become modified and adapted 1861 1866 1869 |
| subse- quently become modified and adapted 1859 1860 |
| could, it is probable, become adapted without much difficulty 1872 |
|
