10 THK MAMMALIA. 



is inexplicable. 1 Certainly all the phenomena here 



to are int. -1 liable when the supposition of 



migration does not stumble upon contradictions 



and surnioiintahle obstacles, and when the capacity 

 of tin. 1 organism to acclimatise itself using the 

 in its widest sense is taken into account as 

 a l<>ng since established fact; but the question as 

 to the origin of species in general is left as a point 

 to be considered apart. Without doubt that which 

 tends to the widest distribution of an animal form 

 and to the intercourse between the most different 

 species, is the sea. Since recent scientific investi- 

 gations have made us as intimately acquainted 

 with the ocean-currents as with the systems of 



. with the range of cold currents and ton 

 of water in the southern seas and conversely, and 

 has marked the different depths of the ocean 

 currents, and ,u r iven us charts of the bottom of 



-ea, with maps showing its elevations and 

 depressions it would seem that, with an account 

 of the animals in the sea, the possibilities and 



s of their occurrence would likewise be ex- 



The state of the matter is very diiTerent as 

 the di>trihminn of animals on land, in 



1 Wallace, Tlic Ga .bution of Animals. 



