Chapter IV — 51— Origin of Areas 



refined, the more do we reveal small, ecologically more specialized spe- 

 cies, formerly included in broader categories. 



This process of the breaking up of collective species does not, how- 

 ever, show that a contraction of initial areas is the natural direction of 

 development of present-day areas. Such an unceasing retrogression 

 would not be in accord with the evolutionary development of organ- 

 isms and actually does not take place, since the newly arisen vicarious 

 species, from the centers of their origin, initiate anew a progressive 

 extension of range. Coming upon favorable conditions, such species 

 create secondary centers of development of the genus. As a result of 

 the destruction of vegetation over considerable territories, as during the 

 Ice Age, there penetrated, subsequently, into these territories numerous 

 species, the areas of which reached enormous size. In many cases these 

 species have not yet attained their limit of possible distribution. 



Periods of great climatic changes have occurred on our globe many 

 times (the above-mentioned uniformity of climatic conditions in the 

 northern hemisphere in former geological epochs did not always pre- 

 vail), and during such earlier periods of chmatic changes the differenti- 

 ation of genera and species must have been just as markedly expressed 

 as at present. Subsequently, with the coming of more uniform cli- 

 matic conditions, small species made place for large species, which 

 embraced ever larger and larger territories during the course of their 

 dispersal. These ancient extensive areas, with the disappearance of 

 uniform climatic conditions, again entered into a period of contraction, 

 partly as a result of the dying out of species over a portion of their 

 areas and partly as a result of the breaking up of these areas into a 

 number of smaller areas of new, vicarious species. These vicarious 

 species, in their turn, begin to extend their range. As the territory 

 they occupy increases, they become differentiated into subspecies, 

 which may subsequently be converted into independent species. Thus, 

 there is steadily going on a process of contraction and breaking up of 

 old areas and the appearance in their place of new areas, which un- 

 dergo the same processes of development and disintegration, making 

 way, in their turn, to yet new species. The evolution of areas proceeds 

 unceasingly, in conformity with the uninterrupted process of differenti- 

 ation, specialization, and evolution of species. 



Only the areas of relic species steadily decrease in size, as these 

 for the most part decadent species gradually become extinct. 



The theory of the origin of areas advanced by Pachosky (1910, 

 1925) may, in its basic features, be accepted, though, in our opinion, a 

 different explanation should be given to the data presented by him. 

 Pachosky, who is an opponent of the migrational origin of an area, 

 considers that the ability to change in a certain direction is inherent 

 to an entire genetic group, that it is equally inherent to all its repre- 

 sentatives throughout its entire area, and that it manifests itself not 

 in a single locality of the latter but throughout its entire territory. 

 Hence, a race, long before it becomes an established independent unit, 

 already occupies a definite area, this area being the result of in silu 

 changes and not of migration. Such a process of area-formation 

 Pachosky calls "pantopic". 



To the foregoing we must take exception to the extent that we 



