Np. 496] ASPECTS OF THE SPECIES QUESTION 



2<M 



plants were shown to be capable of being developed into 

 well-known lowland species in a single generation, illus- 

 trate a phenomenon similar to that exhibited by Poly- 

 gonum. It is likely that our manuals contain many so- 

 called species, such as these, which await reference to 

 ecological varieties. 



Having eliminated habitat forms from the rank of 

 species, and having disposed of the influence of natural 

 selection as a destroyer of many incipient species, it 

 remains to discuss the varied ideas concerning the real 

 or supposed species that remain. In the main it may 

 be said that there are two opposing conceptions of 

 species that are to-day struggling for mastery in the 

 realm of biologic thought. The more prevalent idea, 

 dating in its essence from the time of Darwin, has been 

 that species* are artificial creations, mere matters of con- 

 venience in the classification of the organic world, arbi- 

 trary concepts that have no great and enduring reality. 

 Partisans of this view hold to the doctrine of continuity, 

 maintaining that all species have been connected with 

 other species by a series of intergrades, and that there is 

 no vital distinction between variation and mutation. If, 

 indeed, many species, such as the sassafras, differ widely 

 from all other known species, this is because of the elimi- 

 nation of intergrading forms. In the case of Sassafras, 

 this idea is strengthened by the evidence furnished by 

 fossil forms. In somewhat striking contrast to this con- 

 cept of species stands the idea that species are entities, 

 which arise by discontinuous variation or mutation, and 

 which have their full specific value from the start. Xor 

 does time change specific form by any slow gradations; 

 the species at its death shows no essential difference 

 from the species at its birth. In many instances, at least, 

 these species are of lower rank than the Linnean species, 

 and have been known as small or elementary species. As 

 a rule those who hold to the latter species conception are 

 more prone to appeal to hidden " internal" causes in 

 explaining the origin of new species, while environmental 



