Lastly, the
law law 1859 1860 1861 1866 | wonderful law 1869 1872 |
of the long endurance of allied forms on the same continent,— of marsupials in Australia, of edentata in America, and other such cases,— is intelligible, for
within a confined within a confined 1859 1860 1861 1866 |
generally within the same 1869 |
within the same 1872 |
country, country, 1859 1860 1861 1866 1869 | country 1872 |
the
recent recent 1859 1860 1861 1866 | existing 1869 1872 |
and the extinct will
naturally naturally 1859 1860 1861 | naturally 1866 1869 1872 |
be
allied allied 1859 1860 1861 | closely allied 1866 1869 1872 |
by descent. |
Looking to geographical distribution, if we admit that there has been during the long course of ages much migration from one part of the world to another, owing to former climatal and geographical changes and to the many occasional and unknown means of dispersal, then we can understand, on the theory of descent with modification, most of the great leading facts in Distribution. We can see why there should be so striking a parallelism in the distribution of organic beings throughout space, and in their geological succession throughout time; for in both cases the beings have been connected by the bond of ordinary generation, and the means of modification have been the same. We see the full meaning of the wonderful fact, which
must have must have 1859 1860 1861 | has 1866 1869 1872 |
struck every traveller, namely, that on the same continent, under the most diverse conditions, under heat and cold, on mountain and lowland, on deserts and marshes, most of the inhabitants within each great class are plainly related; for they
will generally be will generally be 1859 1860 1861 |
generally are the 1866 |
are the 1869 1872 |
descendants of the same progenitors and early colonists. On this same principle of former migration, combined in most cases with modification, we can understand, by the aid of the Glacial period, the identity of some few plants, and the close alliance of many others, on the most distant mountains,
under the most different climates; under the most different climates; 1859 1860 1861 |
and in the northern and southern temperate zones; 1866 1869 1872 |
and likewise the close alliance of some of the inhabitants of the sea in the northern and southern temperate
zones, zones, 1859 1860 1861 | latitudes, 1866 1869 1872 |
though separated by the whole intertropical ocean. Although two
areas areas 1859 1860 | countries 1861 1866 1869 1872 |
may present
the same the same 1859 1860 | the same 1861 1866 1869 1872 |
physical conditions
of life, of life, 1859 1860 |
as closely similar as the same species ever require, 1861 1866 1869 1872 |
we need feel no surprise at their inhabitants being widely different, if they have been for a long period completely
separated separated 1859 1860 | sundered 1861 1866 1869 1872 |
from each other; for as the relation of organism to organism is the most important of all relations, and as the two
areas areas 1859 1860 | countries 1861 1866 1869 1872 |
will have received colonists
from some third source or from each other, from some third source or from each other, 1859 1860 1861 1866 |
OMIT 1869 1872 |
at various periods and in different proportions,
the the 1859 1860 1861 1866 |
from some other country or from each other, the 1869 1872 |
course of modification in the two areas will inevitably
be be 1859 1860 | have been 1861 1866 1869 1872 |
different. |