{ 446 ) 



Characters like these, common to a mnltitnde of racial forms living in one isolated 

 district, cannot be accounted for by a direct effect of isolation : it would be almost 

 ridiculous to assume that the first specimens of a great number of species which 

 came to Celebes had all long and falcate wings, while the specimens dispersed over 

 the neighbouring groups of islands had short wings ; or that the first specimens 

 which came to Sumatra and Borneo were dark, while the individuals of the same 

 species which migrated to Java were in so many cases less black. 



We now have seen that the geographical isolation of aberrant specimens has not 

 been and is not the means of the divarication of species, and that the effect of the 

 transmuting factors acting upon the sjiecimens of a sjjecies within the same locality 

 is at the liighest marked polymorphism ; therefore there is only one way possible 

 by which the divarication of a species into two or more can come about — that is, the 

 combination of isolation and transmuting factors. The isolation of one or more 

 (Neo-Darwiuiau and Neo-Lamarckian) /ac^ora is the means by which the specimens 

 of a species which are subjected to these isolated factors, whichever they may be, 

 become different from those specimens which stand under other influences, no matter 

 whether the first specimens which became isolated as to the transmuting factors 

 were normal or alierrational. This assnmirtion corresponds completely with the 

 resuU of experiments, and explains all the peculiarities in the characters of geo- 

 graphical races and representative species. And we shall see in the third part of 

 this paper that there are instances in which the geographical isolation can be very 

 incomplete, and in which, nevertheless, the divergent development will lead to specific 

 distinctness of the biologically isolated specimens. 



The geographical races thus produced we must assume to be first inconstant, to 

 become more and more constant and divergent by the incessant influence of the 

 transmuting factors, and to develop finally into a form which is so modified that it 

 never will fuse either with the parent-form or the sister-forms, and that it therefore 

 agrees with the definition of the term " species." 



As this kind of divarication of species is the only possible * one, and hence 

 geographical jiolymorphism of a species the beginning of the ramification into more 

 species, the study of localised varieties is of the greatest importance in respect to 

 the theory of evolution ; the study of geographical races, or subspecies, or incipient 

 species, is a study of the origin of species. The meaning of the term " sub- 

 si3ecies,"f nowadays generally apjilied to geographical or localised forms, is 

 evolutiouistic, and, in fact, the only evolutionistic idea wliicli has penetrated 

 into that work of systematists which is purely diagnostic. Every scientist 

 who pretends to be an evolutionist must perceive the importance of subspecies. 

 Whoever persistently ignores the existence of subspecific characters ought to 

 have the courage which I admire in Charles Oberthiir— great courage it certainly 

 requires to defend a standpoint against the bulk of naturalists— to define the 

 species as a created entity. 



Eimer, Artbildung iind Verwandtschaft bei Schmetterlingen, gives beautiful 

 examples of the various degrees of divergency of localised varieties. Whether only 

 one or a few specimens exhibit in a given locality a character not found elsewhere ; 

 whether a greater number of individuals in a certain district are characterised by a 



• It is scarcely necessary to add that the area to wliich a certain transmuting factor is restricted 

 need not be a political or physiographical district. 



t This teim had alrcaily been applied to geographical races before the appearance of Darwins Onym 

 (/ Spi'cirx. 



