XLV 



like Mycaiesis, occur some whose wings show a fair amount of yellow and 

 even orange; in Java, indeed, this is the case only in a couple of species but 

 in others, not occurring in that island, it is found in a much greater degree. 

 Whence this difference? Since we have already traced the course of the 

 process of colour evolution in many other butterflies it is easily assumed that 

 the original Satyridae were also red and that subsequently the red of these 

 butterflies turned to orange and yellow in the usual course; that, moreover, at the 

 same time a great increase of the black pigment occurred causing the colour 

 of the wings of many species to become darker in varying degrees of intensity 

 while in others, which in consequence of the inequality, invariably characterizing 

 the appearance of evolutionary processes, not having advanced to the same 

 extent, much yellow or orange has been retained, so that, therefore, these colours, 

 where they are present, must be regarded as relics of an older condition and 

 the butterflies in which they occur exhibit a less advanced stage in the evo- 

 lutional extension of black. This is, indeed, in complete agreement with the 

 theory of colour evolution and with what may be observed in this respect also 

 in other butterflies. But here we find an instance where from a comparison 

 with some closely allied butterflies the course of this process may be observed 

 in a particularly striking manner. The orange spot near the apex on the upper 

 side of the fore-wings in Cyllo Leda L. (PI. XV fig. 30^), wich in some 

 specimens, however, is larger and clearer than shown in the figure, is nothing 

 but a vestige of a much greater amount of orange such as still occurs in many 

 races or species of Cyllo (PL XV fig. 307, ;-). In some this appears in the 

 form of a fairly broad streak running transversely across the wing surface and 

 it may be observed here how first in some individuals this streak is invaded 

 and covered at its lower end by the black pigment, exactly in the manner as 

 we have observed that it was correctly noted by Alfred Goldborough Mayer ; 

 it then (PI. XV fig. 3or) encroaches on the remainder which becomes covered 

 bit by bit until but little is left, as is frequently the case in Cyllo Leda L. 

 (PI. XV fig. 30c), which, moreover, also gradually becomes covered completely 

 by the black pigment in the individuals of this species further advanced in the 

 evolution (PI. XV fig. ^oe). If, in fact, the various stages, as they occur in 

 these butterflies, were to be reproduced cinematographically in succession, a 

 correct idea could be formed of the course taken by the process of colour 

 evolution here being enacted. Of the various stages in this process instances 

 have been retained in the various species, races, or individuals. 



We have here a specially apposite illustration of the course adopted by 

 the process of colour evolution which, like that of the "streak on the edge 

 between the red which has remained there and the white which has become 



