LEADING GROUPS OF EXISTING SYSTEMS 175 



every day the great probability of the independent origin of indi- 

 viduals of the same species in disconnected geographical areas, force 

 us to remove from the philosophic definition of species the idea of a 

 commtmity of origin, and consequently also the idea of a necessary 

 genealogical connection. The evidence that all animals have origi- 

 nated in large numbers is growing so strong, that the idea that every 

 species existed in the beginning in single pairs may be said to be 

 given up almost entirely by naturalists. Now if this is the case, sexual 

 derivation does not constitute a necessary specific character, even 

 though sexual connection be the natural process of their reproduc- 

 tion and multiplication. If we are led to admit as the beginning of 

 each species the simultaneous origin of a large number of individ- 

 uals, if the same species may originate at the same time in different 

 localities, these first representatives of each species, at least, were not 

 connected by sexual derivation; and as this applies equally to any 

 first pair, this fancied test criterion of specific identity must at all 

 events be given up, and with it goes also the pretended real existence 

 of the species, in contradistinction from the mode of existence of 

 genera, families, orders, classes, and types; for what really exists are 

 individuals, not species. We may at the utmost consider individuals 

 as representatives of species, but no one individual nor any number 

 of individuals represent its species only without representing also 

 at the same time, as we have seen above (Sect, i to v), its genus, its 

 family, its order, its class, its branch.^^ 



Before attempting to prove the whole of this proposition, I will 

 first consider the characters of the individual animals. Their exist- 

 ence is scarcely limited as to time and space within definite and 

 appreciable limits. No one nor all of them represent fully, at any par- 

 ticular time, their species; they are always only the temporary repre- 

 sentatives of the species, inasmuch as each species exists longer in 

 nature than any of its individuals. All the individuals of any or of 

 all species now existing are only the successors of other individuals 

 which have gone before, and the predecessors of the next generations; 

 they do not constitute the species, they represent it. The species is an 

 ideal entity, as much as the genus, the family, the order, the class, or 



^ [For a discussion of Agassiz's views on the species question, its relationship to the 

 origin of man, and related literature on these subjects see Edward Lurie, "Louis 

 Agassiz and the Races of Man," Isis, XLV (1954), 227-242.] 



