326 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1925 



To admit known facts and yet say that selection and isolation are 

 not factors in evolution would appear to make the matter a mere 

 question of words. If by evolution we mean the theoretical progress 

 of life, due solely to forces intrinsic in organisms, then outside 

 influences are of course not factore in such evolution. If, however, 

 we mean the actual life movements of actual organisms on this 

 actual earth, then extrinsic influences and obstacles are factors in 

 continuous diverging change. 



