68 A. E. Ortmcmn — Separation, OMd its 



1. Each species must have originated in a separate locality 

 (center of origin). 



2. It is very improbable that the same species originated 

 tvi^ice in different and separated parts of the earth. 



3. The same species existing in completely separated locali- 

 ties indicates a former connection, which, as a rule, lies not far 

 back in time. 



4. Nearly allied species in separated localities indicate a for- 

 mer connection, but in a more remote time. The degree of 

 relation may give a rough estimate of the relative time that has 

 elapsed since separation. 



5. Formerly separated parts of the earth's surface are diffi- 

 cult to locate, since a later connection destroys the differences 

 that existed formerly, and the animals peculiar to each separate 

 part cannot be recognized. 



I may add, that palseontological research may find out, and 

 indeed in some cases has already found out, examples of the 

 latter kind,* since the peculiar fauna of an isolated locality can 

 be preserved in fossil state. 



I think I have sufficiently demonstrated, that the principle 

 of separation not limited to a strictly geographic sense, but 

 enlarged, and understood generally as a bionomical principle, 

 is not only important as regards the origin of species, but also 

 as regards geographical distribution, palseontological and geo- 

 logical history of animals. Bionomic separation means that it 

 is essential for separation, that the groups of animals separated 

 from each other are subject to different conditions of life, and 

 I emphasize this point as the chief peculiarity which effects a 

 differentiation of the characters of animals inhabiting different 

 stations. We can imagine a purely geographical (topograph- 

 ical) separation with the conditions of existence remaining 

 unaltered in the separated parts : then a differentiation of 

 species does not result, and the original species continues to 

 exist without a change. We know many examples of this kind, 

 that an identical species is found in separate localities, and I 

 have called (1. c, p. 34) such species relics from a former con- 

 tinuous distribution. 



I think, everybody who has ever undertaken to study the 

 origin of species will agree with the views set forth here, at 

 least as regards the insufficiency of natural selection for the 

 differentiation of species, and everybody will concede, that 

 transformation or mutation of a species is fundamentally dif- 

 ferent from differentiation into coexisting species, and that in 

 this respect Weismann's opinion, that natural selection may 

 explain ''the mode of formation of the living world as a 



* For example : Neumayr in the Cretaceous and Jurassic periods, Mojsisovics 

 in tlie Triassic, and recently Weller in the Devonian period. 



