xvni 



has operated in like manner on the two species arrived thither from other 

 parts, without influencing others in which this susceptibiHty has not yet been 

 developed. 



On these grounds we must, therefore, admit the existence of such local 

 influences operating on the evolutionary processes to which the Rhopalocera 

 are subject although we may be unable as yet to indicate their nature. When, 

 however, empty phrases or the forementioned erroneous conception fail to satisfy 

 us, this conviction, as clearly follows from what has here been formulated, can 

 only be based on the phenomena revealed by a ^tudy of the evolution both 

 of the forms and of the colours of butterflies, a study which must, therefore, 

 reveal the existence of the phenomenon of colour evolution also. It is, more- 

 over, not the only fact in this connection which can only thereby be explained. 

 In my monograph of the Pieridae of Java, on page 50, I explained in this 

 way the presence of the red dots on the wings of the European GoNOFrERVX 

 Rhamni L, which are doubtless well known but whose cause nobody has 

 hitherto been able to indicate, and on pages 41 and 50 1. c. the equally 

 known and equally mysterious 8 shaped metal- coloured spots on the hind-wings 

 ot some species of Colias. On page jj I pointed out how clearly this pheno- 

 menon manifests itself in the various colour forms and the remarkable colour 

 relics, connected with them, of the genus Hebomoia, such as the streak on the 

 upper side of the fore-wings retained in the specimens of a species from the 

 Philippines, Flores, Sumba, and in a lesser degree in those from Java and 

 how completely it explains this but only in accordance with my conception of 

 the problem. In many other places besides I have clearly indicated this process. 

 What is the reason that this theory of mine of colour evolution, for which I 

 have striven so many years, not with hollow phrases indeed, but with the 

 adduction of large quantities of material in support thereof, has received so 

 litde credence? Can it be because, unlike so many present day biological 

 theories which receive much support, it is not based on superficial reasoning 

 and hollow propositions supposed to be confirmed subsequently by isolated 

 observations insufficiently controlled but strongly biassed by preconceived 

 notions, but is the result of the unprejudiced observation of a number of 

 mutually corroborative facts? Because its examination requires a method in 

 which those are not versed who have been brought up in the present day 

 experimental methods — /. e. of investigating what has already a priori been 

 assumed — but are not accustomed to explain logically by means of extended 

 comparison facts obtained by unprejudiced observation? Perhaps so, for no 



