SELECTION 155- 



have changed. They cannot have been useful to- 

 ancestors, because they have only lately been de- 

 veloped. And we cannot suppose that they give 

 any special advantage in each island, because all 

 the islands have practically the same climate and 

 the same flora and fauna. This exhausts the re- 

 sources of the principle of utility ; and we are driven 

 to the conclusion that these specific characters have 

 a non-utilitarian origin. And, if the colours have 

 not had a utilitarian origin in these isolated species,, 

 it is quite probable that they may not have had a 

 utilitarian origin in other cases., where two or more 

 species of the genus are found together. Therefore 

 it follows that recognition-marks and other specific 

 characters do not necessarily arise through natural 

 selection. To form these non-utilitarian characters- 

 something else must have been at work. 



A second objection is sometimes made, that inci- 

 pient variations, even if they are useful, cannot be 

 of any importance in the struggle for existence, and 

 that natural selection could not develop them until 

 they had made a considerable advance. This is 

 quite true ; but it is only another form of the first 

 difficulty ; for until the variations have attained to 

 what is called " Selection Value " they are merely 

 useless characters. 



The third difficulty is that natural selection r 

 although a powerful cause of divergence between 

 different species and genera, cannot by itself, initiate- 

 divergent evolution. This will come as a surprise to 

 those who have learnt from the writings of Dr. 

 Wallace that natural selection is the one great cause 



