THE COURSE OF BIOLOGIC EVOLUTION. 4-\ 



monotonous and uninteresting. From the esthetic point of 

 view, therefore, this is the most important law of biology. 



What is its importance from the scientific point of view ? As 

 you probably all know, there has been going on during several 

 years past a very lively discussion of the principle of natural 

 selection, and that principle has been vigorously attacked by a 

 large and highly respectable class of working naturalists. Its 

 vulnerable points have been fearlessly exposed and its de- 

 fenders have been put to their wits' end to save it from serious 

 impairment. It has seemed to me that their mode of defense 

 was ill-chosen and that its weakness consisted in claiming too 

 much for natural selection, more than it can justly be shown to 

 accomplish. The weakest link in the chain is the first one, as 

 Darwin himself admitted, and it seems strange that he, who 

 maintained that the variations which natural selection seizes 

 upon to the advantage of the organism are fortuitous, should 

 not have conceived that these might go on as they begun for a 

 long time and result in important changes that were neither 

 beneficial nor injurious. Those who question the principle of 

 natural selection insist with apparent justice that the incipient 

 changes due to accidental variation during a single generation 

 are utterly inadequate to perpetuate and multiply themselves, 

 that their utility must be infinitesimal and practically nil ; and 

 they pertinently ask how the machinery of natural selection 

 was ever set in motion. Strange as it may seem, the de- 

 fenders of natural selection have thus far found no better 

 answer to this argument than to deny its force and to maintain 

 that every variation, however slight, if in the direction of 

 utility, begins to operate from its inception and goes on increas- 

 ing with cumulative strength. This answer is not satisfactory 

 and its inadequacy has been sufficiently proved. It should 

 be abandoned and some other substituted, and until this is 



