VII. 



ANALOGY. 



A NALOGICAL reasoning plays a very im- 

 <L portant part in all scientific work; and 

 Darwin frequently availed himself of its help 

 in making discoveries and establishing conclu- 

 sions. He used every logical device to estab- 

 lish and extend his theories, and there is no 

 lack of material from which to choose exam- 

 ples. But analogy, when used on a large scale, 

 proves so treacherous, that it is useful for the 

 most part only in giving clues to discoveries. 

 There are but few examples of analogical rea- 

 soning on a large scale in Darwin's works. 

 The most important, perhaps, is his work on 

 Insectivorous Plants. 



It has already been told how, while resting 

 at Hartfield after years of labor on the Origin 

 of Species, he was struck by the number of 

 insects caught by the leaves of the common 

 sundew. It soon became evident to him that 

 " Droseraw&s excellently adapted for the special 

 purpose of catching insects, so that the subject 



