VARIATION AND DISTRIBUTION OF SPECIES. 147 



Among the leading naturalists, indeed, sucli views — takers 

 in the widest sense — have one and, so far as we are now 

 aware, only one thorough-going and thoroughly consistent 

 opponent, namely, Mr. Agassiz. 



Most naturalists take into their very conception of a species, 

 explicitly or by implication, the notion of a material connec- 

 tion resulting from the descent of the individuals comjiosing 

 it from a common stock, of local origin. Mr. Agassiz wholly 

 eliminates community of descent from his idea of species, and 

 even conceives a species to have been as numerous in individ- 

 uals, and as widespread over space, or as segregated in dis- 

 continuous spaces, from the first as at a later period. 



The station which it inhabits, therefore, is with other natu- 

 ralists in nowise essential to the species, and may not have 

 been the region of its origin. In Mr. Agassiz's view the hab- 

 itat is supposed to mark the origin, and to be a part of the 

 character of the species. The habitat is not merely the 2)lace 

 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 difficult to draw a clear and certain distinction be- 

 tween the two. Mr. 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 super- 

 natural, their dispersion or particular geographical area, nat- 

 ural, and their extinction, when they disappear, also the result 

 of physical causes. In the view of Mr. 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 palaeontologists now apj^ear 

 to recognize a certain number of species as having survived 

 from one epoch to the next, or even through more tlian one 

 formation, especially from the Tertiary into the Post-tertiary 

 period, and from that to the present age. ]Mr. Agassiz is 

 understood to believe in total extinctions and total new crea- 



