192 EVOLUTION OF TO-DAY. 



continents. Their offspring would develop varieties, 

 and by continued modification these varieties would 

 become species, and the whole would thus form a 

 new genus. Still later even greater would be the 

 differences. All of the new species thus developed 

 would, of course, be well enough adapted to the 

 conditions of the island, but utterly unfit to con- 

 tend in a struggle for existence on the mainland. 

 Nor, indeed, could they contend with the species of 

 the mainland should they be introduced into the 

 island, since the continental species have developed 

 under severer competition and are consequently the 

 best of the many varieties which have appeared, all 

 inferior varieties being exterminated on the main- 

 land ; but this has not occurred in islands. 



The explanation of island life as here given has 

 been the result of long study. It has been given 

 here, however, in order to make more intelligible a 

 few examples. I have selected three groups of 

 islands to serve as illustrations of the principles here 

 involved, which form a series showing very prettily 

 that the above explanations are correct. The first is 

 the group of Bermudas, situated some five hundred 

 miles off the coast of North America. These islands 

 are in the stormy Atlantic, and are subjected to 

 frequent winds, making every thing favorable for 

 the visiting of the islands by birds and insects and 

 the consequent arrival of various plants for birds 

 carry many seeds in their toes and crops. Direct 

 observation proves that these islands are thus fre- 

 quently visited. No less than one hundred and 

 sixty-eight species of birds are found ; all of them 



