COLOUR IN LKPIDOPTERA. 



whatever, nor can there be left the least idea of seasonal 

 forms. But then, what can be the cause of all those changes 

 of colour? Well, the theory of temperature does not answer 

 this question ; but my theory does. 



And the many colour-variations in American Callydrias- 

 species and in the Australian Catopsilia Gorgophone Bsd., 

 stated by Dr. Dixey, will surely have to be explained in 

 the same way. 



A great deal more important is Dr. Grafin M. von Lin- 

 den's work »Untersuchungen über die Entwicklung der 

 Zeichnung des Schmetterlingsflügels in der Puppe" ^). As 

 is said on page 117 of my paper I have always thought 

 these ontogenetical investigations the weak point of my 

 theory, because they disclosed facts, apparently not to be 

 reconciled with it, and yet in spite of all possible conside- 

 rations being of no small significance. Indeed those consi- 

 derations are rather important. Not only do we not find 

 here such well separated consecutive ontogenetical stadia 

 as are so clearly visible in caterpillars, but we also cannot 

 dispose of such a relatively long lapse of time, at hand 

 for the observation of embryological changes in many other 

 animals, thus greatly facilitating it. And time is a valuable 

 thing in this matter, as the phylogenesis, that has to be 

 traced, has not taken place constantly and regularly, but 

 now quicker then slower, with periods of genepistasy of 

 extremely unequal duration, and not at all following the 

 same course either on both the wing-surfaces or their 

 parts. Then the well-known phenomenon of some phyletical 

 stadia happening to fall away in the ontogenesis is to be 

 added. Now in the changes which the wings of the not 

 yet full grown butterfly in the pupa undergo during the 

 48 hours before coming out of the butterfly, all this has 

 to be traced as it has developed in the course of perhaps 

 many ten thousands of years. And still more this does not 



1) Zeitschrift fur wissenschaftliche Zoölogie, 6oer Bd. ler Heft, Leipzig, 1898. 

 I^otes from ttie Leyden IMuseuna, Vol. XX.II. 



