COSMIC PHILOSOPHY 



for food, it will not be the first case in which it 

 has happened that a structure useful in one way 

 has also become useful in another way. The 

 question is an interesting one, and valuable if 

 only because it reminds us of the danger of rea- 

 soning too confidently, from a priori premises, 

 about matters the due elucidation of which re- 

 quires careful study of the details of the every- 

 day life of animals. It is one of the great merits 

 of the theory of natural selection that it has 

 directed so many naturalists, with eyes open, 

 into this fruitful field of inquiry. 



It is because it so well illustrates the wealth 

 of suggestiveness in Mr. Darwin's theory, that 

 I have ventured upon this digression. To the 

 general validity of that theory, or even to the 

 validity of the more special hypothesis concern- 

 ing the uses of concealment or of conspicuous- 

 ness, the success of the foregoing explanation 

 is not essential, — since its possible inadequacy 

 may very well be due to the incompleteness of 

 our grasp upon all the details of this particular 

 case. But, returning from this digression to our 

 main thesis, and considering the general signi- 

 ficance of the phenomena of colour, we see that, 

 in addition to those most general phenomena 

 of organic life which demand for their explana- 

 tion the Darwinian theory, there is at least one 

 special class of phenomena which that theory 

 is competent to explain even in minute details. 



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