EVOLUTION 119 



to become the progenitors of a new stock 

 bearing the favorable traits. 



The individual differences which Darwin be- 

 lieved to afford a basis for this process are 

 not the characters acquired during life, but 

 are those features with which the young or- 

 ganism is born. These differences are germinal 

 in their origin, and therefore may be handed 

 on ; in other words, Darwin's theory avoids 

 the difficulty of the inheritance of acquired 

 characters and is based upon what is known 

 to be heritable differences. 



That natural selection is a process that oc- 

 curs in nature seems to be beyond dispute. 

 A single instance may suffice to show this. 

 After a severe winter storm in Providence, 

 Rhode Island, on February 1, 1898, many of 

 the English sparrows of that region were found 

 to be much spent and exhausted. Of these 

 birds, one hundred and thirty-six were col- 

 lected and brought within doors, and of this 

 number seventy-two revived and sixty-four 

 died. A close comparison of these two sets 

 disclosed the fact that the birds that died 

 were less near the normal than those that sur- 

 vived, showing that, for instance, a heavy body 

 with small wings or a light body with large 



