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maintain with Eimei- that abnormal varieties show distinctly the directions in which a 

 species is able to develop. We give an illustration. For certain reasons which we cannot 

 explain here, as they concern details of structure, we must consider Papilio sarpedon 

 to be derived from a form which had green spots within the cell of the forewing and 

 a submarginal row of green markings, and that P. sarpedon is now on the way to lose 

 the green markings altogether. The specimens of P. siirpiedon from the Solomon 

 Islands have preserved some of the additional spots, while in the forms from other 

 localities the forewing has only a median macular band ; in South India and Ceylon 

 the first spot of this band disappears very often, and in China the band of the hind- 

 wing is often reduced to a costal patch. Now, Mr. de Nic(^\ille figures a " sport " from 

 Sumatra* in which the median band of both wings has disappeared, except a small 

 spot, and which therefore has an almost entirely black upperside. The specimen is now 

 in the Tring jNIuseum, which contains also another individual of P. sarpedon (from 

 Sikkim) that has the median band of the forewing dusted over with black scales, 

 which conceal jiartly the green ground-colour of the wing-membrane. The direction 

 of development indicated by these two " spoi'ts " coincides with that which we are led 

 by structural characters to consider the real direction of development of P. sarpedon, 

 and the importance of this coincidence is obvious. 



Apart from polymorphism among the individuals in the same locality, we 

 observe very commonly a polvmorphism in which the various forms are sejiarated 

 geographically. This geographical polymorphism we shall have to deal with later 

 on, and therefore we restrict ourselves here to the remark that the various geographical 

 varieties are, just like the forms of ordinary polymorphism, often not connected by 

 intergradations, and thus are likely to mislead us species-makers to treat them as 

 "distinct species"; in the latter respect geographical and non-geograpliical poly- 

 morphism have much in common, because they are homologous phenomena, as we 

 shall soon see ; and we may add that geographical separation of different forms 

 cannot be an a pjriori criterion of specific distinctness, though this has often enough 

 been alleged. 



The individual variation including non-geographical and geographical polymor- 

 phism, as dealt with in the preceding lines, concerns especially the individuals which 

 exist as contemporaries ; now let us liriefly consider the historical side of the 

 variation. According to the theory of evolution, the descendants have in the course 

 of time (gradually or per saltum, in respect to the distinguishing characters as well 

 as to time) become dissimilar to their ancestors; we assume generally that a long 

 period was necessary to bring a considerable change in an animal or plant about. A 

 period of one or two hundred years is by many systematists considered quite in- 

 sufficient to alter in nature a form of animal or plant so far that the change is 

 obvious, or that any transformation has taken place at all within the same localilv. 

 Though we accept the theory of the transmutation of the species in the course of time 

 as the base of scientific work in Natural History, we nevertheless identify the forms 

 found in our days with the forms which our forefathers in science had before them ; 

 without hesitation we treat the forms, whether they be species or variety, captured 

 in 1896, as identical with those which Linne received a hundred and fifty years ago, or 

 which Merian or Seba obtained aliont two hundred years back. And when we observe 

 a difference between our recent specimens and the old pictures, differences which are 

 by no means always explainable by the assumption of incorrectness of the drawings, 



• Joiim. Bomhay N. II Soc. 18!i:!. ji. r,l. t. I., f^ 11 1,0- 



