790 Fluctuations 



strosities have been dealt with as instances of 

 such ever-sporting varieties. 



Now the question may be put, what would be 

 the effect of selection if in long series of years 

 one of the two characters of such a double race 

 were preferred continuously, to the complete 

 exclusion of the other. Would the race become 

 changed thereby? Could it be affected to such 

 a degree as to gradually lose the inactive qual- 

 ity, and cease to be a double race? 



Here manifestly we have a means by which 

 to determine what selection is able to ac- 

 complish. Physiologic experiments may be 

 said to be too short to give any definite 

 evidence. But cases may be cited where 

 nature has selected during long centuries 

 and with absolute constancy in her choice. 

 Moreover unconscious selections by man have 

 often worked in an analogous manner, and 

 many cultivated plants may be put to the 

 test concerning the evidence they might give 

 on this point. Stating beforehand the result of 

 this inquiry, we may assert that long-continued 

 selection has absolutely no appreciable effect. 

 Of course I do not deny the splendid results of 

 selection during the first few years, nor the ne- 

 cessity of continued selection to keep the im- 

 proved races to the height of their ameliorated 

 qualities. I only wish to state that the work 



