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 effect on the life of the —— 
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. t 
