446 POPULAR SCIENCE MONTHLY. 



ception that adaptations are due to eztemal causes only as environment 

 may influence the direction of the normal and necessary movement of 

 the species. 



That evolution is thus an active, universal and truly physiological 

 process is not considered in current theories, largely because thought 

 and language have continued to follow the bias of the original con- 

 troversy in seeking in evolution an explanation of the origin of species 

 and in expecting, conversely, that an explanation of the origin of species 

 would also explain evolution. It is, therefore, a matter of literary as 

 well as of scientific difficulty to present an alternative view, that the 

 multiplication of species is in no proper sense a result of evolution, but 

 is due to entirely distinct causes more often antagonistic than favorable 

 to evolutionary progress. 



Evolution versiLS Taxonomy. 



The early evolutionists were all systematists deeply impressed by 

 the vast complexity of organic nature, a sentiment which we may still 

 indulge, since two centuries of labor have but made a beginning in the 

 task of describing and assigning names to the millions of groups of 

 organisms. Nevertheless, it is to be regretted that biological evolution 

 was viewed and expounded so exclusively from the standpoint of the 

 taxonomist, since his interests are greatly at variance with those of the 

 evolutionist, and the confusion of the two distinct lines of investigation 

 has done much to perpetuate the erroneous identification of the origin 

 of species with the process of evolution. 



The evolution best appreciated by the taxonomist is one which has 

 produced species separable by definite and easily definable characters. 

 He finds such species on islands and in other circimascribed regions and 

 thereupon decides that isolation is an important evolutionary factor, 

 failing at the same time to perceive that the 'constancy' which he 

 ascribes to insular species is merely a uniformity made possible by the 

 limited area of distribution, and hence often absent in species of more 

 extensive range. Small segregations of individuals acquire uniformity 

 of characters more promptly than if they were larger, and the sooner 

 afford diagnostic differences of use to the systematist. This does not, 

 however, decrease the probability that evolutionary change is slower in 

 small groups than in those which the systematist abominates — large 

 assemblages of individuals, offering great variety of characters, but 

 without uniformity of combinations. 



The systematist is prone to believe that there has been more evolu- 

 tion in a genus of ten definable species than in another occupying the 

 same geographical region, but consisting of only one species. For the 

 evolutionist, however, the segregation of the numerous species means 

 that the conditions are less uniformly favorable for the subdivided 



