XV 



other species, including those in Allotinus Nivalis Druce to the same origin, 

 from which it must follow that in this last species of Allotinus the dark 

 pigment is in a decreasing condition. For although at first sight it may appear 

 arbitrary to attribute the same origin to spots which appear in different species, 

 merely because they are of the same shape, yet as a matter of fact there are 

 good grounds for this. If, as I hope to demonstrate later on, we are brought 

 to the conclusion that all the forms in which colour-evolution displays itself, 

 follow fixed evolutionary laws, although being exposed to and influenced by 

 countless disturbances, they express themselves in a great variety of ways, then 

 we must also assume that, where the same very characteristic forms appear, 

 they point to a similar development of the process of colour evolution. The 

 influences to which I refer are extremely numerous and variable, and it is there- 

 fore hardly probable that they should display themselves in different species in the 

 same very characteristic way, during the course of the process of development. 



Moreover such an intensely black circular spot must undoubtedly be the 

 product of a massing of dark pigment, which can hardly occur where it is 

 still in a condition of gradual increase, but which indicates that an accumulation 

 of it has taken place ; these accumulations will only disappear after the pigment 

 has vanished from those places, where it was not so thick. In many Lycaenidae 

 there are other black spots of larger or smaller size, but they are not of this 

 peculiar circular form, but of a more irregular shape. These must certainly be 

 regarded also as accumulations of pigment, and presumably they do not differ 

 in nature from those described above. On the other hand it is difficult to 

 determine whether in L. Rosimon (PI. XX 3T,ad) F. the dark pigment is in the 

 increasing or decreasing stage. This pigment shows itself in a peculiar way 

 in this species; in Taraka Hamada Druce (PL XX 28) it is about the same. 

 But in the first mentioned species, especially in the female, this characteristic 

 accumulation of dark pigment along the costal margin, the outer margin and 

 the apex of the upperside is unmistakably recognisable, which, as will be 

 explained later, is found in so many Lycaenidae, especially in the females. 

 And in these it certainly suggests that the pigment is extending. But this may 

 be deceptive, the contrary is also possible. 



In L. Plinius F. (PI. XX, 3^aff) the female, as also the underside of 

 the male, is marked very similarly to the species mentioned above, but the 

 upperside of the male is completely darkened, and displays a structural colour. 

 This makes the explanation again difficult. As has already been remarked, it 

 is in many cases difficult to make out, whether the dark pigment is increasing 

 or decreasing, as well as, when the increase has begun, what stage the 

 other process of colour-evolution, namely that of fading, had attained, when 



