THE DISTRIBUTION OF ANIMALS AND PLANTS 411 



are extinct. Thus we can prove that many of the peculiar 

 species of these islands have remained unchanged since Plio- 

 cene times. While differing from modern European shells, 

 several of these species are very near to European Miocene 

 species. Thus we seem to have evidence in the Madeira 

 group, not of modification, but of unchanged survival of Ter- 

 tiary species long since extinct in Europe. May we not infer 

 that the same was the case in the Azores ? These results are 

 certainly very striking when we consider how long the Azores 

 must have existed as islands, how very rarely animals, and es- 

 pecially pairs of animals, must have reached them, and how- 

 complete has been the isolation of these animals, and how 

 peculiar the conditions to which they have been subjected in 

 their island retreat. 



Other oceanic islands present great varieties of conditions, 

 but leading to similar conclusions. Some, as the Bermudas, 

 seem to have been settled in very modern times with animals 

 and plants nearly all identical with those of neighbouring coun- 

 tries, though even here it would appear that there are some 

 indigenous species which would indicate a greater age or more 

 extended lands, now submerged. 1 Others, like St. Helena, 

 are occupied apparently with old settlers, which may have come 

 to them in early Tertiary, or even in Secondary periods, which 

 have long since become extinct on the continents, and whose 

 nearest analogues are now widely scattered over the world. 

 Islands are therefore places of survival of old species special 

 preserves for forms of life lost to the continents. One of the 

 most curious of these is Celebes, which seems to be a surviving 

 fragment of Miocene Asia, which, though so near to that con- 

 tinent, has been sufficiently isolated to preserve its old popula- 



1 Heilprin mentions eleven marine mollusks supposed to be peculiar to the 

 islands, and eight species of land shells, as well as a few Crustaceans hither- 

 to found only in the Pacific. The comparisons are, however, admitted to 

 be incomplete. 



