58 THE SCIENTIFIC EVIDENCES OF 



raised sufficiently to unite all the islands on 

 each side of the deep water into two great 

 tracts of land, separated from one another by 

 the deep strait of water. Each of these great 

 tracts of land would then have had their own 

 distinctive kinds of quadrupeds — just as the 

 American quadrupeds are now distinct from the 

 European ; for the ' comparatively narrow strait 

 between the then Malay continents would have 

 offered as effectual a barrier, to the migration of 

 quadrupeds as does the Atlantic Ocean at the 

 present day. Hence, when all the land slowly 

 subsided so as to leave only its mountain chains 

 and table lands standing above the surface in 

 the form of islands, we now have the state of 

 things which Mr. Wallace describes — viz., two 

 large groups of islands with the quadrupeds on 

 the one group differing widely from the quad- 

 rupeds on the other, while within the limits 

 of the same group the quadrupeds inhabiting 



