22 THE EVOLUTION OF 



some use. I do not attach any value to investigations of 

 temperature or of cross-breeding in this matter. 



Meanwhile there has been announced as prize-ques- 

 tion by Czar Nicholas II for the International Congress 

 of Zoology in 1901 to be held in Germany, an investiga- 

 tion as to the influence of light on the development of 

 the colours in Lepidoptera, and into the causes of such 

 deviations in colour, form and structure, appearing in those 

 parts of these insects that are covered in their state of 

 rest. Now such an investigation, shall it be of any value, 

 will have to reckon with my theory of colour-evolution. 

 In fact according to that, the difference in colour is — at 

 least in the imagines and caterpillars of Lepidoptera — 

 principally the consequence of a hereditary evolution, which 

 though perhaps not wholly excluding the influence of light, 

 does indeed reduce it to a thing of little significance; and 

 SO if that influence shall be proved, my theory must also 

 be proved to be erroneous, these two being inconsistent 

 with each other. Only in a very secondary way some of 

 that influence still remains possible, as for instance was 

 stated by Prof. Poulton and Meldola regarding some Sphin- 

 ^i(7aé-caterpillars, though these too are subject to colour- 

 evolution. I do not think it quite impossible that light 

 can indeed act a part among the still unknown local 

 influences — I call them geographical ones — that will alter 

 the colour of imagines now and then, as well as that some 

 abnormal chemical changes can be occasioned in the wings 

 of butterflies by letting rays of light of any definite colour 

 act on the pupae. When judging the answers to this prize- 

 question it will be wise not to overlook the warning words 

 on pages 80 — 85 of my paper on <Sp/«'?7^^(/ae-caterpillars 

 and also what I wrote about the (in their state of rest) 

 partly covered wings of Lepidoptera, on pages 245 — 249 

 of my study on the Pieridae. 



It must not be forgotten that of a great many Lepi- 

 doptera, resting with their wings folded up, the whole 



Notes from the Leyclen üMuseum, Vol. XXII, 



