200 DARWINIANA. 



other naturalists in no wise essential to the species, 

 and may not have been the region of its origin. In 

 Agassiz's view the habitat is supposed to mark the 

 origin, and to be a part of the character of the species. 

 The habitat is not merely the place where it is, but a 

 part of what it is. 



Most naturalists recognize varieties of species; 

 and many, like De Candolle, have come to conclude 

 that varieties of the highest grade, or races, so far 

 partake of the characteristics of species, and are so far 

 governed by the same laws, that it is often very diffi- 

 cult to draw a clear and certain distinction between 

 the two. Agassiz will not allow that varieties or races 

 exist in Nature, apart from man's agency. 



Most naturalists believe that the origin of species is 

 supernatural, their dispersion or particular geographi- 

 cal area, natural, and their extinction, when they dis- 

 appear, also the result of physical causes. In the view 

 of Agassiz, if rightly understood, all three are equally 

 independent of physical cause and effect, are equally 

 supernatural. 



In comparing preceding periods with the present 

 and with each other, most naturalists and palaeontolo- 

 gists now appear to recognize a certain number of 

 species as having survived from one epoch to the next, 

 or even through more than one formation, especially 

 from the Tertiary into the post-Tertiary period, and 

 from that to the present age. Agassiz is understood 

 to believe in total extinctions and total new creations 

 at each successive epoch, and even to recognize no ex- 

 isting species as ever contemporary with extinct ones, 

 except in the case of recent exterminations. 



