| → all kinds, 1869 1872 |
| every kind have had on distribution, 1859 1860 1861 1866 |
|
| → confined to the same country, or if they have a wide range that their range is continuous. 1866 1869 1872 |
| confined to one area. 1859 1860 |
| if they have a wide range that their range is continuous. 1861 |
|
| → be, if a directly opposite rule were to prevail, when we go down 1869 1872 |
| be, if, when coming 1859 1860 1861 |
| be if a directly opposite rule were to prevail, when we go down 1866 |
|
| → and these had not been, at least at first, confined to some one region! 1866 1869 1872 |
| a directly opposite rule prevailed; and species were not local, but had been produced in two or more distinct areas! 1859 1860 |
| a directly opposite rule prevailed; and species were not local, but had been produced in two or more quite distinct areas! 1861 |
|
|
I believe, is, that mammals have not been able to migrate, whereas some plants, from their varied means of dispersal, have migrated across the
and broken
The great and striking influence
barriers of
→all kinds,
is intelligible only on the view that the great majority of species have been produced on one
and have not been able to migrate to the
side. Some few families, many sub-families, very many genera, and a still greater number of sections of
are confined to a single region; and it has been observed by several naturalists, that the most natural genera, or those genera in which the species are most closely related to each other, are generally
→confined to the same country, or if they have a wide range that their range is continuous. What a strange anomaly it would
→be, if a directly opposite rule were to prevail, when we go down
one step lower in the series,
the individuals of the same species,
→and these had not been, at least at first, confined to some one region!
|
|
| Hence it seems to me, as it has to many other naturalists, that the view of each species having been produced in one area alone, and having subsequently migrated from that area as far as its powers of migration and subsistence under past and present conditions permitted, is the most probable. Undoubtedly many cases occur, in which we cannot explain how the same species could have passed from one point to the other. But the geographical and climatal changes, which have certainly occurred within recent geological times, must have
rendered discontinuous the
continuous range of many species. So that we are reduced to consider whether the exceptions to continuity of range are so numerous and of so grave a nature, that we ought to give up the belief, rendered probable by general considerations, that each species has been produced within one area, and has migrated thence as far as it could. It would be hopelessly tedious to discuss all the exceptional cases of the same species, now living at distant and separated
nor do I for a moment pretend that any explanation could be offered of many
after some preliminary remarks, I will discuss a few of the most striking classes of facts; namely, the existence of the same species on the summits of distant mountain-ranges, and at distant points in the arctic and antarctic regions; and secondly (in the following chapter), the wide distribution of
productions; and thirdly, the occurrence of the same terrestrial species on islands and on the
though separated by hundreds of miles of open sea. If the existence of the same species at distant and isolated points of the
surface, can in many instances be explained on the view of each species having migrated
|
