XI 



It is difficult, therefore, to assume otherwise than the existence of local influences 

 causing these changes of colour. When, however, one is familiar with the 

 nature of the evolutionary changes which cause the modifications of form and 

 colour, to which Lepidoptera are subject, it will be perceived that in reality 

 the changes here referred to do not go beyond the acceleration, retardation, 

 or direction in a certain channel of an evolutionary process of change already 

 existing ; they evidently agree, therefore, with those which are expressed in so 

 different a manner in the process of extinction of the horn of the Sphingidae 

 larvae, already alluded to, and are most probably, therefore, caused in like 

 manner by the attendant special influences. These are in that case, however, 

 unmistakably of a local character. Other phenomena exist which can likewise 

 be only attributed to local influences. Butterflies of the same species in Celebes 

 and from the Moluccas are frequently considerably larger than those of Java ; 

 in Flores, on the other hand, they are frequently smaller; why? 



We know that adverse surroundings are able to modify in a wrong direction 

 the hereditary course of development of a child. But although we clearly 

 discern the existence of such influences we can only demonstrate a portion of 

 them whereas others, whose presence is equally certain, are beyond our ken ; 

 these are usually classed together under the general term " antihygienic condi- 

 tions". It is also known that such influences may be due to local causes and 

 when their nature is known this may occasionally be demonstrated. To assume 

 that the hereditary course of development of the forms and colours of butter- 

 flies also may be guided in another direction by influences proceeding from 

 their environment, is consequently by no means startling. Only, in order to 

 grasp this, it should be understood that these changes of form and colour are 

 no accidental phenomena but the expression of hereditary courses of evolutionary 

 development. Of this, however, lepidopterologists have as a rule no conception 

 whatever. 



When I protested very strongly just now against the present practice of 

 attributing every little difference, especially in distribution of colour but also 

 in form between butterflies of the same species occurring in different districts, 

 in general to so-called local influences, without being able to adduce any evidence 

 concerning their nature except fanciful statements about droughts or rainy seasons, 

 it should not be assumed that I wish to doubt the existence of local influences 

 as such. With so extremely superficial and unscientific an exaggeration I do 

 not wish to associate myself; it is, moreover, not the only one of its kind 

 which may be observed in the speculative treatment of the differences in colour 

 in Lepidoptera, already alluded to. Some insular melanism, assumed indeed 

 but certainly not existing, has had to do duty in this connection in turn with 



