208 



THE AMERICAN NATURALIST 



[Vol. XLI 



species which support the notion of common descent. Plants 

 and animals, they said, occur upon the surface of the globe just 

 as if they had originated by evolution, and in a manner unintel- 

 ligible on the assumption of special creation. Species are uni- 

 versally found in the neighborhood of other species which they 

 resemble; or to put this generalization in evolutionary phrase, 

 species arise in geographic proximity to the species from which 

 they may be supposed to have sprung. The geographic evidence 

 was an important part of the testimony accumulated by Darwin 

 ('59), to which he gives two of the fifteen chapters of the "Origin 

 of Species." Wallace ('55) had already published an essay 

 arguing for the evolutionary conception of organic history, the 

 main thesis being this: "Every species has come into existence 

 coincident both in time and space with a pre-existing closely 

 allied species." Thus the evolutionist has been under deep 

 obligation to the taxonomer from the beginning. 



The obligation is likely to be much increased with the lapse 

 of time. I do not agree with D. H. Scott, that the determination 

 of the actual course of descent is the ultimate, or chief, object 

 of the scientific systematist.' The fact of evolution being ad- 

 mitted, and the course of evolution lia\iiiu- been ascertained^ 

 there still remains the question, " Hy what methods have new 

 forms emerged from old ones?" — a subject not less interesting 

 or important than the others, from any point of view. It schmus 

 to me, furthermore, that the final i^oal of phyioncon-raphy is not 

 reached in the reconstruction of the continents and islands of 

 former epochs, and the reviving of ancient states and changes 

 of climate, through the study of the history of the vegetation of 

 the earth ; nor is its purpose satisfied in teaching us through 



fariously adapted to tiieir environments. Hioloiiieally considered, 



matic botany and zoology and with experimental morphology 

 in composing the solid basis of an a(h (|uate th(H)ry of evolution. 



'The present Position of Palseozoie Botimy. Lot^v^ I'mir.v.Mi-. liei Motan- 

 icjp, 1: 139 (1907). 



