( xxxvii ) 



another have a different standing in classification from the non-geographical 

 entities. 



(2) If a small projiortion of tlie specimens of A' and A- are the same, 

 and A' and A- (or one of them) are brought under conditions which favour 

 the appearance of the characters of this small proportion in each case, 

 bionomics teach us that A' and A- will in the course of time become more and 

 more similar, overlap wider and wider, and become finally identical. That is 

 to say, A^ and A= cannot live together without fusion. However, if A^ and 

 A2, which differ, say, in 99-9 per cent, of the individuals, cannot exist together 

 as separate entities, A= and A^, which are connected by intergradation in the 

 intermediate countries, or A^ and A^, of which the ranges of variation are 

 contiguous, or A^ and A^ which are separated by a small gap, have no chance 

 of remaining separate entities, if by accident brought under the same con- 

 ditions of life. As tiiere is a gradation in the morphological difference between 

 geographical representatives (see Fig. 2, in which the curves D', D=, D^ etc., are 



^ 







A^^AA f\r< 



00 



Fig. 2. 



the geographical representatives), some being slightly, others more distinctly, 

 and others again widely different, it is obvious that the chance of the 

 representatives mot overlapping in characters, under those altered conditions 

 of life above referred to, becomes larger and larger, the wider the morphological 

 gap is between them. From this point of view it depends, therefore, entirely 

 upon the characters of the geographical representatives whether these can 

 exist together or not, i.e. whether there is a similar gap between A' and A- 

 to that between A' and B'. In other words, considering the gradation in 

 the morphological differences, there are morphologically different geographical 

 representatives which can certainly not exist togetlier without fn.sing to one 

 entity, and there are otliers which may be so far settled in their characters 

 that a fusion will not take ]ilace. 



From what we liavc said it follows tliat it is wrong to treat all 

 geographical corporeally different forms indiscriminately as lieing separated by 

 that same barrier which i)revents synoecic animals from fusing. As science 

 does not knowingly perj)etuate errors, the contention which we have 

 demonstrated to be erroneous slumld !»■ aliaucidued \i\ those who claim their 



