XXVIII 



the Lycaenidae of Java this resemblance is very striking, for instance, between the 

 9 of Lycaena Kerriana Dist. (Plate XXI, ^ga.6.) and of LycaenesthesTessellata 

 Moore (Plate XXII, 88) ; it is stranger still to find the peculiar white lines 

 above referred to which occur on the underside of many Lycaenae recurring 

 in Deudorix Kessuma Horsf. (PL XXV, 126a. 6.). This may be seen even in 

 butterflies inhabiting quite different districts. I have pointed this out already 

 on p. xvi of the introduction to my second monograph. For colour-evolution 

 is the same in all butterflies all over the world, where, therefore, as occasionally 

 happens, it proceeds under the same conditions in different places, it leads to 

 the same results. The great variety of colouring displayed by Lycaenidae 

 is also caused by this. 



What we are able to observe about this process may give the impression of 

 confusion, but in reality it is governed neither by accident nor caprice, but we must 

 look for the explanation in a number of disturbing influences which work upon 

 it, and which can be so numerous and drastic as to confuse, not the process 

 itself, but our observations of the phenomena by which it is revealed. That 

 is, in so far as these observations are not made in a thoroughly scientific manner. 



In what way the impetus to any evolutionary process arises, is not known, 

 in the case of colour-evolution no more than of any other, but we do know 

 that this impetus leads to actual changes in very different ways; there must 

 be susceptibility to reaction in the creature upon which it works, and it must 

 possess a fitness for it. 



Now the susceptibility to this influence and therefore to evolutionary change 

 of colour is extremely different in different individuals ; formerly when discussing 

 the supposed seasonal varieties I showed this clearly enough. This evolution 

 takes place much more rapidly in one individual than in another; where, as 

 far as we can judge, the same conditions are present, some display evolutionary 

 phenomena, while others remain quite unchanged. This explains the presence. 

 In the same district and at the same time, of butterflies of the same species, 

 which differ from one another In colour, according as this evolution Is further 

 or less far advanced. 



Seeing that the susceptibility is so different even between Individuals, It Is 

 not surprising that the sexes also should differ in this respect sometimes. As 

 there Is a physiological difference between both sexes, it appears to be probable 

 that this may bring with it a differece in susceptibility; and furthermore, 

 where the susceptibility exists, the changes brought about by evolution 

 must also be influenced by the physical peculiarities of the Individual upon 

 which it works, and when the peculiarities in different species, or at any 



