SHORTER ARTICLES AND CORRESPONDENCE 



EVOLUTION WITHOUT ISOLATION 



Is isolation a factor of evolution ? The answer must depend, 

 obviously, on what we mean by evolution, as well as upon the 

 relations of the facts. Every difference of opinion regarding the 

 nature and causes of evolution involves the use of the word in 

 a different sense, unless the process is to he renamed with each 

 change of interpretation. The choice of words is worthy of care- 

 ful consideration, hut words should not lead us away from the 

 broader issue of biological farts. The practical question is nol 

 whether the words or their senses are new or unusual, but 

 whether the facts are correctly represented. 



Being convinced that changes in the characters of species are 



those who believe that changes in species are brought about by 

 external influences working upon normally stationary groups, 



process, inherent in the species. 



From one point of view evolution appears as a complex of 



a process of growth in the species, somewhat analogous to the 



posed. In the one case the species are thought of^as being 



advancing by motions of their own, often in spite of environ- 

 mental obstacles and deflections. 



Belief in isolation as a factor of evolution marks an inter- 

 mediate stage of ojuTrpw' between those who hold that natural 

 selection causes evolution, and those who reject selection as a 

 cause. The effort is to maintain the doctrine of environmental 



ontogeny, etc. Nevertheless, this course has its logical dangers 

 for the theory of selection, for the placing of much emphasis 

 on isolation is practically equivalent to saying that evolutionary 



