THE COURSE OF BIOLOGIC EVOLUTION. 51 



than that of natural selection, since its influence when fully 

 understood will be found to be as great, and to Darwin alone 

 is due the entire credit of making it known. Strangely enough 

 Dr. Alfred Russel Wallace, who simultaneously and indepen- 

 dently worked out the law of natural selection, is disposed, as 

 shown by his recent work on Darwinism, to reject sexual selec- 

 tion altogether as a factor in biology ; yet to my mind, it re- 

 mains debatable which of these two great laws has exerted the 

 more profound effects in modifying the course of organic devel- 

 opment. It certainly cannot be said of natural selection that 

 it has produced a eonrolete revolution in that course, or has, so 

 to speak, reversed the wheels of biologic progress, as sexual 

 selection has done : not in the sense of producing a retrograde 

 movement, but in that of shifting the axis of evolution, if I 

 may be allowed the expression, from its normal position to a 

 wholly abnormal one, and raising to a prime factor what was 

 originally a mere incident in the history of organic life. 



Female Selection. — But by sexual selection Darwin meant 

 only female selection, which would be the more accurate ex- 

 pression. It was not until the era of birds and mammals that 

 the female really began to exercise a choice, or if, as is proved 

 in a few cases, the females of lower creatures did exercise a 

 choice, the result was the same as in the higher, the superiority 

 of the males. 



You all understand this law too well to make any explana- 

 tion of its operation necessary, and I only desire to bring it 

 forward as one of the most important of all the abnormal or 

 illegitimate influences that have brought about the present 

 state of things. I also wish to point out its analogy to the 

 other two influences which I have considered. For here again, 

 size, strength, and beauty, as displayed in the males of so 

 many animals and birds, are the products of a dawning and 



