SAND DUNES AND SALT MARSHES 



ined enough material to throw any light on 

 the subject. 



One can easily see how important the ele- 

 ment of clannishness is, for without that, in- 

 terbreeding might for a long time, if not 

 indefinitely, delay the birth of a new species. 

 The importance of this factor in the evolution 

 of races and species, has, I believe, never been 

 given due weight. 



As among men so among birds there are 

 striking differences in ambition and ability 

 to succeed. Some men, some families, some 

 nations are progressive, — they are always 

 reaching out for new opportunities and taking 

 advantage of them. Others are retiring, un- 

 ambitious and contented to remain where they 

 are. One of the most markedly progressive 

 birds is the horned lark found on this coast 

 so abundantly in the migrations. The horned 

 lark has spread to nearly every part of the 

 continent and has made each part so much 

 its home that it has adapted itself to the 

 environment to the extent of changing its 

 own form and plumage. There are now rec- 

 ognized fourteen different North American 

 races, or sub-species, as they are called, of 

 the horned lark. The pushing character of 



296 



