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successive generations ? If such do occur, can we doubt 

 (remembering that many more individuals are born than can 

 possibly survive) that individuals having any advantage, 

 however slight, over others, would have the best chance of 

 surviving and procreating their kind?" In this way Darwin 

 supposes " new variations to be continually taking place, but 

 the greater number of them speedily to become extinct ; 

 whilst others, becoming perpetuated, and perhaps causing 

 the extinction of the original forms, again give rise to other 

 forms, until some of them have so widely diverged that all 

 traces of their common origin is lost." " As buds give rise 

 by growth to fresh buds, and these, if vigorous, branch out 

 and overtop on all sides many a feebler branch ; so by 

 generation, I believe, it has been with the great Tree of Life, 

 which fills with its dead and broken branches the crust of 

 the earth, and covers the surface with its ever-branching and 

 beautiful ramifications." 



It would be foreign to the purpose of these papers to 

 discuss at any length this grand theory of evolution. But, 

 independently of all that might be said either in favour of 

 or against it, it should always be remembered that of all 

 possible theories of the origin of species, it is that which 

 is most in harmony with the ordinary facts of experience. 

 The origin of individual organisms is a matter of scientific 

 observation; but the origin of species must still be re- 

 garded as inferential. Bearing in mind, however, that 

 every living organism has been evolved out of a perfectly 

 simple cell, in which the microscope shows no vestige .of 

 structure, it certainly seems more consistent with this fact 

 that species have been developed by " descent with modi- 

 fication" from perfectly simple ancestral forms, than to believe 

 that they have been created all at once just as we see them. 



