20 THE EVOLUTION OF 



pillars is a rule, evidently proceeding ontogenetically under 

 a hereditary stress, manifesting itself in all species of that 

 family wheresoever in the world they may live, and though 

 having indeed a very different course still bound in its 

 appearance to definite periods of the general development 

 of the animal, I do think this theory rather hard to be 

 still admitted. At all events the non-existence of colour- 

 evolution in these caterpillars will first have to be proved, 

 for where this cannot be denied, the action of this same 

 phenomenon with regard to the expansion of colour in 

 imagines has positively to be considered as a very likely one. 

 Chemical, microscopical and ontogenetical investigations 

 may be continued as to its course, though rather in a more 

 systematical way than has been done up to now, if it 

 might be of any use. First of all one should try to know 

 of all the appearing colours in any definite butterfly, whether 

 they are pigmental or structural colours. Especially this is 

 needed in regard to those butterflies whose colour-evolution 

 is investigated ontogenetically. For as only pigmental colours 

 are of importance for the study of colour-evolution it must 

 indubitably lead to confusion, if they are not properly 

 distinguished. Now though Miss Newbegin is of opinion 

 that optical colours cannot, of course, be found at an onto- 

 genetical investigation yet Dr. Grafin von Linden has posi- 

 tively found them. Even the white colour in the wing-tip 

 of Danais Plexippus L. is according to the investigation 

 of A. G. Goldsborough Mayer structural and presumably 

 it will be quite the same with the white Fawessa-spots of 

 Dr. V. Bemmelen. All such investigations should further 

 specially direct attention to the colours and their develop- 

 ment in such butterflies where the prime colour differs in 

 the same species, in sexes, races or forms, and so one colour 



Eelations between the Colour of such Larvae and that of their Food-plants. 

 Troc. Royal Society London, Vol. XXXV III, 1885; and E. B. Poulton: The 

 Experimental Proof that the Colours of certain Lepidopterous Larvae are largely 

 due to modified Plantpigments derived from Pood. Proc. Royal Society London, 

 IV, 1893. 



Notes from the Leyden M^useuui, Vol, XXII. 



