11 



expression, has been subjected to much exaggeration and has, consequently, 

 degenerated into mere speculation. The attitude assumed in this connection is 

 that the form, and especially the colour pattern of the butterflies, originate, 

 chiefly if not entirely, through the influence of the environment and become 

 modified also in connection with it. The nature of this influence — cold or 

 heat, drought or moisture, light or food, or anything else — is in no way 

 thoroughly investigated but is left to the fruitful source of the imagination. It 

 is true much stress is laid, in this connection, on the results obtained from 

 experiments in which pupae of European Rhopalocera have been subjected 

 artificially to varying degrees of cold and heat, but conceived in a very super- 

 ficial manner and interpreted without knowledge of the phenomenon of colour 

 evolution, indeed without really grasping the evolutional nature of the morpho- 

 logical changes; these results, consequently, as I have already explained in 

 detail else-where, are altogether wrongly understood ; in reality the said erro- 

 neous opinion can find no support in them. Although all these factors may 

 now and again exercise some influence on the form and colour of butterflies, 

 as will be considered presently, by far the principal factor in this respect is 

 their hereditary morphological evolution and, therefore, as regards the colour, 

 the process of colour evolution. The numerous small differences in individuals 

 of the same species only represent so many different stages in this evolution 

 which, of course, in individuals living in isolated localities, may occur somewhat 

 more strongly developed but without this being the actual result of the difference 

 of locality. In an article by Krapotkin in the N'ineteenth Century for September 

 1 90 1 , entitled Recent Science, I find it stated that from a quantity of land snails 

 collected by Gulick on a mountainous island of the Sandwich Archipelago it 

 was shown that each valley possesses a peculiar form of these mollusca with 

 many varieties, and that according to the opinion of Hyait, who investigated 

 this collection, this proves conclusively that all these forms cannot possibly have 

 been caused by the climate since this is the same in all these valleys. To 

 attribute it to difference of locality is neither to be thought of. Between indi- 

 viduals of one species of one butterflies living together on the same island, 

 several instances of which 1 have already indicated amongst the Pieridae of 

 Java, such differences occur likewise; differences between the sexes are even 

 very common, known as sexual dimorphism although in reality having no 

 relation to difference in sex as such ; on the other hand the same stage of evolution 

 may be attained simultaneously by individuals living in different regions and 

 give rise to the same forms. The expression "local form", therefore, in itself 

 is not altogether correct and if it is desired to attach to this the scientific 

 meaning of forms caused principally through local influences it is not applicable 



