52 



advanced in the same degree in different regions. In the most common form 

 the middle part of the wings on the upper-side is sulphur-yellow and the rest 

 chalky-white. So it always is f. i. in Java and in many other regions, but in 

 other parts there is a great difference in the extension of that yellow, that is, 

 in the larger or smaller degree in which it has already paled into white, so 

 that sometimes, as f i. in Celebes the yellow is diffused over the whole surface 

 of the wings. This one has been distinguished as the form Flava Butl., here 

 and there numerous transitions occur, while in Banda, Timor and also in Celebes 

 both forms even occur besides each other. On some 9, which for the rest 

 have turned white already, the same yellow is still to be seen covering a great 

 part of the upper-side, just as in the cT, which proves that in both sexes the 

 process of bleaching has the same character, though this cannot always be 

 distinctly observed. The circumstance that the transitional forms often do not 

 exist any more may render it very difficult, while in the evolution of the ^i" 

 perhaps an acceleration may sometimes have taken place, in which transitional 

 stages evidently seem to have been skipped. Thus we have already seen that in the 

 changing of the red spot into white, as is to be observed in some 9 of Iphias, 

 the yellow stage has been passed. The fact of these accelerations in the process 

 of development has created the mutation theory ; a comparison with the process 

 of the colour-evolution in other Iphias forms clearly shows that in these the 

 yellow stage reallv exists, and that therefore this apparent mutation can only 

 be the result of an acceleration in that process, which prevents its being 

 observed. 



I shall now try to give here an enumeration of the different colour-forms 

 in which this species occurs and of the places from where those forms have 

 become known to me. For convenience sake I shall separate those forms into 

 certain groups. It must, however, be borne in mind that this is done only for 

 convenience' sake and therefore artificially : in reality all those forms are con- 

 nected with each other by transitions. And as to the localities in which they 

 have been found, in my collection, as well as in that of the Leyden museum, 

 there are a good number of specimens of this species from different regions 

 of the Indian archipelago. But the material from Java is considerably larger 

 in number than that from elsewhere, so that my observations concerning the 

 forms occurring in Java, will also be much more complete. 



I. cf G r o u p s. 



«. Upper-side : the common form described above. Continent of India, 

 Java, Bawean, Sumatra, Banka, Rio-Lingga archipelago, Borneo, Nias, Celebes, 



