270 THE WORLD OF LIFE 



movements appear to be slow creeping undulations passing over 

 continental plateaus and their immediately adjacent submarine 

 extensions. Sometimes the depressions seem to have taken the 

 form of basins; but we cannot conceive of any elevation of conti- 

 nental dimensions, or depression of oceanic character as to depth 

 and area, without the complementary movement to complete the un- 

 dulation. A continental extension between South America and 

 Australia would almost necessarily imply a subsidence of one or 

 both of those countries over an equal area and to an equal depth; 

 and, so far as I am aware, no geological evidence has been ad- 

 duced of any such vast changes having occurred at so recent a 

 period in either continent. I believe it can now be truly said that 

 no stratigraphical geologist accepts the theory of frequent inter- 

 changes of continental and oceanic areas, which are so hastily 

 claimed by palaeontologists and biologists to be necessary in order 

 to overcome each apparent difficulty in the distribution of living 

 or extinct organisms, and this notwithstanding the number of such 

 difficulties which later discoveries have shown to be non-existent. 



