THE FACTORS OF ORGANIC EVOLUTION. 



such factor, recognized as in operation by here and there 

 an observer (as pointed out by Mr. Darwin in his intro 

 duction to the second edition), was by him for the first time 

 seen to have played so immense a part in the genesis of 

 plants and animals. 



Though laying myself open to the charge of telling a 

 thrice-told tale, I feel obliged here to indicate briefly the 

 several great classes of facts which Mr. Darwin s hypothesis 

 explains; because otherwise that which follows would 

 scarcely be understood. And I feel the less hesitation in 

 doing this because the hypothesis which it replaced, not 

 very widely known at any time, has of late so completely 

 dropped into the background, that the majority of readers 

 are scarcely aware of its existence, and do not therefore 

 understand the relation between Mr. Darwin s successful 

 interpretation and the preceding unsuccessful attempt at 

 interpretation. Of these classes of facts, four chief ones 

 may be here distinguished. 



(j) In the first place, such adjustments as those exemplified 

 above are made comprehensible^ Though it is inconceiv 

 able that a structure like that of the pitcher-plant could 

 have been produced by accumulated effects of function 

 on structure ; yet it is conceivable that successive selections 

 of favourable variations might have produced it; and the 

 like holds of the no less remarkable appliance of the 

 Venus s Fly-trap, or the still more astonishing one of that 

 water-plant by which infant-fish are captured. Though it is 

 impossible to imagine how, by direct influence of increased 

 use, such dermal appendages as a porcupine s quills could 

 have been developed ; yet, profiting as the members of a 

 species otherwise defenceless might do by the stiffness of 

 their hairs, rendering them unpleasant morsels to eat, it is 

 a feasible supposition that from successive survivals of 

 individuals thus defended in the greatest degrees, and the 

 consequent growth in successive generations of hairs into 

 bristles, bristles into spines, spines into quills (for all these 



