HOW EACH IS FITTED FOR HIS OWN LIFE 109 



can come to be new kinds of birds, new sub- 

 species and species, springing up from time to 

 time. Wonderful and improbable as it seems, 

 there is more reason to believe than there is to 

 doubt that new kinds of animals and plants are 

 constantly in process of making ; that the laws 

 of change are constantly at work, adapting crea- 

 tures to their surroundings or crushing them 

 out of existence because they will not learn new 

 ways. And it is probable that these differences 

 which we mark in the woodpeckers have been 

 the result of efforts to adapt themselves to a 

 peculiar kind of life where food was abundant ; 

 and also that by acquired habits and by acquired 

 tastes for different kinds of foods they will be 

 subject to still further variations in the future. 



