XXIV 



have seen this sequence must have depended on the presence of chemical 

 reagents varying in the course of ages through vital requirements unknown to 

 us, whose action, moreover, each time affected, in an extremely unequal manner, 

 only certain groups of scales. 



Is there sufficient ground, therefore, for assuming that when an animal, in 

 the course of attaining maturity, reaches the actual state of development acquired 

 by the species all these chemical reagents and the vital influences which excited 

 them will be repeated in the same order in its ontogenesis? It is true in the 

 case of the colour of the Sphingidae larvae, just alluded to, the old colour 

 occurs ontogenetically but apart from the fact that there is only question of a single 

 colour change here, there is no comparison with the great difference in colour 

 occuring in the pigments of the Rhopalocera ; in the development of the im- 

 agines, moreover, no well-marked stages, as are caused in the larvae by the 

 moults, are to be observed but the whole formation of the colour pattern is 

 completed in a very short time, according Dr. van Bemmelen within 36 hours 

 before the emerging of the imago. In the course of the various observations 

 made in this manner with reference to the origin of the colours in the wings 

 I could find, indeed, nothing which points to a phylogenetic continuation of 

 colour development. 



As a matter of fact I can discover in the result of the investigations onl}- 

 indications concerning the manner in which the colours of the wings in certain 

 butterflies in their present stage of development have arisen and nothing which 

 points ontogenetically to an orderly change from the original to the existing 

 colour, in the manner this must have occured phylogenetically. To the alleged 

 negative result of these investigations in respect of the theory in question I can, 

 therefore, attach little value. The physiological fact that the pigmental colour 

 in the larvae of Lepidoptera can change gradually as an unmistakable mani- 

 festation of an evolutionary process has been definitely established as the result 

 of my studies in connection with colour changes in the Sphingidae larvae. Of 

 an adaptation, pure and simple, of the colour to the environment, as occurs 

 sometimes in certain larvae and pupae and which, in the usual superficial 

 manner, has in this case also been given as the explanation, there is certainly 

 no question. Now when an extensive series of interdependent and therefore 

 mutually corroborating observations, such as I have published, points to the same 

 conclusion in the imagines of Lepidoptera in general, the admission of this fact 

 is not to be made dependent on the (}uestion whether this can be established 

 ontogenetically by experiment. Insistance on this condition simply reveals a 

 pedantic narrowness of conception. 



In reality these investigations have in this respect little value in themselves. 



