SOCIAL AND INDIVIDUAL ORIGIN OF SPECIES. 35 



varieties appear together not only in the same 

 region, but even at the same points, while the geo- 

 graphical distribution of the more marked varieties 

 and of related species offers no conclusion as to their 

 origin, but only as to the last great migration of the 

 plant world, because they arose before this period, 

 as indeed appears from their distribution. 



Just as different varieties arise simultaneously 

 from one kinship at the same place, the same variety 

 may arise in places far separated, when the analogous 

 external exciting causes occasion an identical trans- 

 formation in the idioplasm. The experimental proof 

 lies in the fact that like beginnings of varieties often 

 appear at great distances from each other. 



An apparent social origin of varieties is indicat- 

 ed, when, after having come together in migration, 

 they first develop the unlike determinants which 

 they have gained in various locations. An appar- 

 ently individual origin of the same or different 

 varieties is indicated, when the formation of the 

 determinants take place at one and the same place, 

 but their development follows only after the kindred 

 has been scattered by migration. 



19. GENERAL RELATION OF THE PHYLOGENETIC LINES IN 

 THE ORGANIC KINGDOMS. 



Since the nature of an organism is contained in 

 the sum of its idioplasmic determinants alone, the 

 evolution of a phylogeny consists in the evolution of 



