GENERAL SUMMARY. 337 



ance of man new qualities were given him by his 

 Creator. But all agree that man is radically set 

 apart from the rest of the animal kingdom by his 

 mental nature. While anatomically he is an ape, 

 mentally he is not only a new order of being, but 

 probably also the highest and the last. 



When, finally, we come to ask what has been the 

 cause or causes producing evolution, we find a great 

 many answers. No two scientists, perhaps, fully 

 agree. The theory of natural selection, advanced at 

 the outset by Darwin, has proved to be an import- 

 ant factor, but inadequate to reach many classes of 

 facts which require explanation. Not only is it 

 open to difficulty, but it has become evident that at 

 best it is only secondary. The selection of the fit- 

 test forms can only come after their appearance, 

 and the origin of variations has demanded more 

 and more attention. Darwin's explanation hardly 

 touched this question, or, at all events, only ac- 

 counted for indefinite, irregular variations, which 

 have been plainly shown to be insufficient. A num- 

 ber of other theories have attempted to avoid the 

 difficulties which natural selection meets. But none 

 of them are in themselves really satisfactory. Some 

 are more difficult to understand than the facts they 

 try to explain ; some do not meet the facts ; some 

 would, if granted, explain the facts, but have little 

 evidence in their favor. Yet all of them, probably, 

 express some truth. The fact is that the organic 

 world is not simple, and there are a great many fac- 

 tors at work. The origin of species has been the 

 result of not one but many causes. Some of them 



