COLOUU IN l.EPinOPTERA. 11 



ones though the average was much darker than that of 

 English examples, from which Norwegians only one or two 

 approached var. polaris Stdgr. which was not actually repre- 

 sented. This seems to tend to the necessity of revoking 

 that Northern race polaris Stdgr., and of admitting that 

 also in the North of Europe the specimens of Vanessa 

 urticae L. consist in darker and lighter-coloured ones, just 

 as in the Netherlands, differing very little in colour from these 

 latter ones, if doing at all so. If now Dr. Urech, though well- 

 aware of the difficulty, still tries to explain the facts that the 

 same diff'erence in temperature with one species can have just 

 the contrary effect with another, and that abnormal cold 

 and abnormal heat sometimes can produce Ihe same results 

 in the same species, I shall not make so bold as to com- 

 bat the scientific value of his reasoning, but I shall still 

 have to doubt its applicableness to this subject. For this 

 supposition in itself being rather hard to admit, with regard 

 to the above-named difference in such nearly related spe- 

 cies, as for instance the Polyommatus Phlaeas L. and Ilerda 

 Epicles Godt. on which I wrote in my paper on pages 204 and 

 205, this explanation will not do where one sees exactly 

 the same changes of colour manifesting themselves in races 

 living in different countries, and even in individuals living 

 next to one another in the same country, or in sexes of 

 the same species, as is obvious to any one having the 

 opportunity of indulging in a more ample contemplation 

 of butterflies, not merely restricted to European species, 

 from which even that most useful var. polaris Stdgr. now 

 also must be excluded. As surely as these changes can not 

 be explained by Dr. Urech's former theory, tending to the 

 effect that where the molecular weight is increasing by better 

 nourishment or a warmer climate the colour also darkens, 

 they can neither be accounted for in this manner. They 

 indicate a phenomenon of evolution evidently going on ortho- 

 genetically through the whole world without heeding any 

 difference of temperature. Colour-evolution of Sphingidae- 

 caterpillars is unquestionably also absolutely independent of 



Notes from the Leyden JMuseuna, "Vol. XXII. 



