XIII 



life and shows itself to us as evolution, but the origin and nature of which 

 are still unknown to us. 



This matter is a phenomenon of great biological importance, the study of 

 which, however, has been neglected until now. Nearest to a just understanding 

 in this respect comes, as far as I know, J. T. Cunningha^m M. A. in his 

 important work " Sexua/ dimorphism in the Anitnal Kingdotn ", published in 

 1900. At page 243 we read: "It must be remembered that, according to the 

 views I am maintaining, external influences only excite variation and deter- 

 mine its direction; the result of the variation, the coloration and marking 

 produced, may depend very largely on the physiological processes of grohwt 

 and the development of tissues ". The author certainly shows himself far above 

 the prevailing ideas ; it is, indeed, a matter of an internal factor, but he did 

 not solve the question which one, as he was not acquainted with the pheno- 

 menon of colour-evolution. As to the knowledge of the coloration of the 

 Lepidoptera and probably of animals in general, the study of this phenomenon 

 is even of such direct importance that I fully maintain what I have said about 

 this subject in my last work, that nowadays no actual scientific significance 

 should be attributed to any considerations about animal coloration in which 

 the phenomenon of colour-evolution is not taken into account. The alteration 

 of the coloration, here mentioned, is, as Prof. Weismann already observed 

 long ago, an alteration of the bodily form as to its coloration and, there- 

 fore, its importance also includes every evolutional corporal alteration. It 

 extends thus to the signification of the real nature of evolutional processes in 

 general. Since Darwin the word evolution may be met with everywhere, but 

 a right understanding of the nature of the organic change that is meant by 

 it, is not at all common. Especially to the totally independent evolutional 

 change of separate organs or physiological units of any being, without these 

 changes seeming to be in its general interest, no due attention has heen paid. 



Like all evolutionary changes the two mentioned here also advance une- 

 qually, occurring irregularly according to species, races, sexes and even some- 

 times in individuals, revealing itself now on one, then on another part of the 

 wings; in every stage of evolution also occurs every now and then the 

 cessation of development, already mentioned, by which the colour ot some 

 part of the wing, or of the whole wing, remains unchanged during many 

 generations, while in the first mentioned case the alteration goes on in the 

 meantime on the other parts of the wings. Herewith appear also the structural 

 colours, and by these different things, arise those numerous varieties in colour 

 and pattern which render the Lepidoptera such a beautiful group of animals. 



The afore-said change of the pigmental colours I first of all observed and 



