246 EVOLUTION OF TO-DAY. 



than to improve them or make new and better ones. 

 No writer has had any difficulty in objecting to nat- 

 ural selection, but very few have been able to sug- 

 gest any valuable supplement, or still less to advance 

 any new theory better suited to the facts. Most 

 scientists, while declining to accept the selection 

 principle, acknowledge their inability to offer any 

 other. Not a few, however, have offered sugges- 

 tions and hypotheses as to the workings of nature 

 in producing species, suggestions sometimes of value 

 but sometimes worthless. To-day hardly two scien- 

 tists would exactly agree in their belief in the method 

 by which the evolution of species is brought about. 

 It is our purpose now to consider several of the 

 most important additions which have been sug- 

 gested as aiding natural selection in producing the 

 present species, or as acting by themselves inde- 

 pendently of Darwin's law. 



It may perhaps seem like a hopeless task to at- 

 tempt to answer these questions. Science has little 

 expectation of being able to explain life. It is quite 

 probable, therefore, that after having investigated 

 this question of the origin of species to the utmost, 

 it will be eventually necessary to fall back upon 

 some unexplored land, just as has been found neces- 

 sary in all other departments of science. But this 

 should not hinder us from following the problem as 

 far as the ability of human reason permits. 



It is first necessary to notice that there are still a 

 few scientists who accept natural selection to its 

 fullest extent. They refuse to admit that the diffi- 

 culties are more than superficial, and they carry the 



