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changes into impossibility, if we take further into account the characters of the 

 organs of cojiulation. ^Vp know from the researches laid down in the body of this 

 paper that the genital armature varies quite independently from the wings and 

 their markings, and that therefore the association of distinguishing cliaracters 

 relating to the wings with such found in the organs of copulation in morph- 

 ological representatives has nothing to do with correlative development; in not a 

 single case have we observed tliat a certain aberrational wing-charucter constantly 

 reapjiearing among the individuals of a certain geographical form of Papilio is 

 accompanied by an aberrational character in the organs of coptdation. As, how- 

 ever, most geographical races are distinguished by characters of the wings and 

 characters of the genital armature, it is evident that the explanation of the pecu- 

 liarities in the wing-markings of a representative form by mechanical isolation 

 of parent specimens which accidentally possessed those peculiarities (in a lower 

 degree) is not an explanation of the presence of the peculiarities in the organs of 

 copulation of the respective form. In order to account for the fact that P. sarpedon 

 Umorensis is (in the sexual armature of the male) different from all other forms of 

 sarpedon, and comes in these organs nearest to the Ceylonese, Sumbanese, and 

 Australian forms, and disagrees considerably with the representatives from 

 Adonara, Sambawa, Lombok, and the Indo-Malayan llegion, the theory of isolation 

 would have to assume that the ancestral specimens of timorensii, no matter wlicther 

 they immigrated into Timor from Australia or from the Malayan islands, must 

 have been distinguished by a rare mixture of external peculiarities combined with 

 an equally rare character in the organs of copulation. The rarity of such a combina- 

 tion in aberrations — in fact we never have found an aberrational individual in which 

 the characters of both the wings and genital armature pointed in the direction of 

 one representative form, instead of in diflf'erent directions — is directly opposed to 

 the fact that most geographical races exhibit that combination ; this contradiction 

 can only be solved by abandoning the assumption that the association of distinguish- 

 ing characters of the wings with such of the sexual organs in localised forms is due 

 to the geographical isolation of ancestral individuals which accidentally possessed 

 such a combination of characters, and by accepting as the final cause of the presence 

 of those characters the modifying action of isolated biological factors peculiar to 

 the district where the peculiar form has originated. 



If we thus attribute the existence of diflerences in the characters of the speci- 

 mens of the same species inhabiting different districts to the presence of a difference 

 in the biologiciil factors of the districts, the degree of divergency of the forms is 

 dependent on the degree of sensitiveness of the species to the action of the external 

 biological factors, as maintained by Darwin, and after him by Weismann and others, 

 in several places ; furtlier, on the intensity of the factors and the time they have 

 been active ; and thirdly, on the degree and duration of mechanical isolation as a 

 prevention of the annihilating effect of intercrossing. As a difference in the i)liysio- 

 logical constitution of various species can be proved only by rearing them under 

 exactly the same external conditions, and as we do not know in the case of species 

 found in the same small island whether they actually do exist under the same 

 external influences, it is not possible for ns to decide with any degree of certainty 

 whether the difference in the amount of divergency exhibited by the forms occurring 

 in the same district is due to the ditfereut physiological constitution of the species 

 differently affected, or to differences in the special e.xternal conditions under which 

 each species perhaps exists. Nor are we able to say whether the greater diversity- 



