Chapter IV — 53 — Origin of Areas 



species arising from this primitive species by the indicated process of 

 dichotomy also had cosmopolitan areas. Subsequently, there began a 

 differentiation of species, the extinction of the unfit, and the localiza- 

 tion of the surviving species. There was thus created the present-day 

 geographical distribution of organisms and their division into the plant 

 and animal kingdoms. 



According to this theory, there are no centers of origin of species, 

 and areas are not formed by dispersal from these centers. A species 

 under the influence of internal causes arises simultaneously throughout 

 the entire area of the maternal species, which breaks up into daughter 

 species, regardless of whether the climate is hot or cold, humid or arid, 

 or whether or not there are present mountains or valleys, oceans, seas 

 or rivers. There is no need to study the migrations of species; dis- 

 continuous areas are explained simply, without need of assuming 

 connections between the continents. Rosa emphasizes that he does 

 not deny the existence of migrations, but he asserts that they have no 

 effect on the basic factors of the geographical distribution of species, 

 which would remain the same even if such migrations had not taken 

 place. In the light of this theory of hologenesis everything is ap- 

 parently very much simpUfied. All complicated speculations as to the 

 distribution of organisms are done away with, and at the same time 

 biogeography as a science is done away with. If we should accept this 

 author's viewpoint, we should have to draw our present treatise to an 

 abrupt close. 



Starting out from entirely correct paleontological data as to the 

 extensive areas of species of former geological periods and their subse- 

 quent contraction, Rosa derives his law of hologenesis, according to 

 which the area of a species is larger, the nearer it stands to the initial 

 species. But in this contraction of areas he incorrectly sees a process 

 of the gradual extinction of life on the globe, a "progressive reduction 

 of variation", as he expresses it (Rosa, 1903). We are not in accord 

 with this line of reasoning, since his entire theory is based on a com- 

 plete disregard of the differentiation of climatic conditions on the 

 earth, resulting in a corresponding differentiation and localization of 

 areas of species. It does not take into account the existence, in addi- 

 tion to retrogressive changes, of the progressive polymorphism of the 

 young species in present-day floras, of their expanding, not contracting, 

 areas. We are not in accord with this theory also because of its con- 

 ception of the development of organisms as a result solely of internal 

 causes and because of its scheme of a dichotomous genealogical tree of 

 species, which is in contradiction to the principles of evolution and to 

 the data of modern science which confirm that scheme of the develop- 

 ment of organisms given by Darwin in his "Origin of Species." 



Monotopic or Poljrtopic Origin of Areas: — Before we close our 

 chapter on the origin of areas, we must take up one more difficult and 

 involved problem, that as to the monotopic or polytopic origin of 

 species and areas. By monotopic origin is meant that a species origi- 

 nated in a single center, from which it subsequently spread over the 

 territory of its present area. There has also been advanced the op- 

 posite point of view, i.e., that a species may originate polytopically. 



