CHAPTER XXV 

 THE MOTH AND THE CANDLE 



T N order to understand and interpret correctly the 

 JL operation of natural selection in producing new 

 species and maintaining them, by " the preservation 

 of favoured races in the struggle for life " (to use 

 Darwin's words), we must take a wide and, at the 

 same time, a minutely accurate survey of the living 

 world. We must seek out the evidences of this opera- 

 tion and use the imagination in forming conceptions as 

 to the varied steps of the process and the results which 

 are likely to ensue from it at different stages and in 

 different conditions. We cannot interpret the existing 

 structures and behaviour of living things by the use of 

 a simple formula, such as that set up by some writers 

 who have not properly studied Mr. Darwin's works, and 

 declare that, according to him, all structures and be- 

 haviours which we observe in living things are perfect 

 and the finished result of survival of the ideally fittest 

 variations. 



Plants and animals are so complex (as no one has 

 shown more clearly than Darwin), not only in their 

 structure but in the chemical and physical action and 

 interaction of their living parts, that in the course of 

 the ages during which the present species have been, 

 step by step, fashioned in the endless vicissitudes of a 



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