226 ANIMALS OF THE PAST 



cataclysms of such appalling magnitude that 

 the whole face of nature was changed, and en- 

 tire races of living beings swept out of exist- 

 ence at once. But it is now generally conceded 

 that while catastrophes have occurred, yet, vast 

 as they may have been, their effects were com- 

 paratively local, and, while the life of a limited 

 region may have been ruthlessly blotted out, 

 life as a whole was but little affected. The 

 eruption of Krakatoa shook the earth to its cen- 

 tre and was felt for hundreds of miles around, 

 yet, while it caused the death of thousands of 

 living beings, it remains to be shown that it 

 produced any efi'ect on the life of the region 

 taken in its entirety. 



Changes in the life of the globe have been in 

 the main slow and gradual, and in response to 

 correspondingly slow changes in the level of 

 portions of the earth's crust, with their far- 

 reaching effects on temperature, climate, and 

 vegetation. Animals that were what is termed 

 plastic kept pace with the altering conditions 

 about them and became modified, too, while 

 those that could not adapt themselves to their 

 surroundings died out. 



