| → southern tem- perate zones and 1866 |
| southern temperate zones and 1859 1860 1861 |
| south, and sometimes 1869 1872 |
|
| → mountains of the intertropical regions, are removed on the views above given. 1866 |
| mountains of the intertropical regions. 1859 1860 1861 |
| intermediate mountain-ranges, are removed on the views above given. 1869 1872 |
|
| → during the recent Glacial period 1866 |
| OMIT 1869 1872 |
|
| → nor the reason 1866 |
| >We cannot say 1872 |
| OMIT 1869 |
|
| → groups of forms, and 1866 |
| OMIT 1869 |
| forms, whilst 1872 |
|
| ↑ 1 blocks not present in 1866 1869 1872; present in 1859 1860 1861 |
| Very many difficulties remain to be solved.
|
|
|
in the
and
→southern tem- perate zones and
on the
→mountains of the intertropical regions, are removed on the views above given. It is extremely difficult to understand how a vast number of peculiar forms confined to the tropics could have been therein preserved during the coldest part of the Glacial period. The number of forms in Australia, which are related to European temperate forms, but which differ so greatly that it is impossible to believe that they could have been modified since the Glacial period, perhaps indicates some much more ancient cold period, even as far back as the miocene age, in accordance with the recent speculations of certain geologists. So again, as I am informed by Mr. Bates, the strongly marked character of several species of Carabus, inhabiting the southern parts of America, indicates that their common progenitor must have been introduced at some early period; and other analogous facts could be given. The exact lines
of migration
→during the recent Glacial period
cannot be
→nor the reason
→groups of forms, and
↑ We cannot hope to explain such facts, until we can say why one species and not another becomes naturalised by
agency in a foreign land; why one
twice or thrice as far, and is twice or thrice as common, as another species within their own homes.
|
| I have said that many difficulties remain to be solved: some of the most remarkable are stated with admirable clearness by Dr. Hooker in his botanical works on the antarctic regions. These cannot be here discussed. I will only say
as far as regards the occurrence of identical species at points so enormously remote as Kerguelen Land, New Zealand, and Fuegia, I believe
|
