250 Studies in the Theory of Descent. 



varieties of Stellatarum have already become 

 so far removed from one another that they must 

 be regarded as intermediate fixed forms, the colours 

 of which no longer become fused together when 

 they occur in one individual, but are developed 

 in adjacent regions. Other facts agree with this 

 conclusion. Thus, among the 140 adult larvae 

 which I bred from the batch of eggs above 

 mentioned, the transition forms were much in 

 the minority. There were forty-nine green and 

 sixty-three brown caterpillars, whilst only twenty- 

 eight were more or less transitional. 



On these grounds I designate the phenomenon 

 as " polymorphism," although it may not yet have 

 reached, as such, its sharpest limits. This would 

 be brought about by the elimination of the inter- 

 mediate forms. 39 



89 [I have long held the opinion that the di- and trimorphism 

 displayed by certain butterflies has originated through poly- 

 morphism from ordinary variability. I will not here enter into 

 details, but will only cite a few instances indicating the general 

 direction of the arguments. The phenomenon to which I 

 refer is that so ably treated of by Mr. A. R. Wallace (see Part I., 

 p. 32, note 1 8) and others. One male has often two or more 

 distinctly coloured females, and in such cases one form of the 

 female generally resembles the male in colour. Cases of 

 polymorphic mimetic females may for the present be excluded, 

 in order to reduce the argument to its greatest simplicity. Thus, 

 in the case of native species, Colias Edusa has two females, one 

 having the orange ground-colour of the male, and the other 

 the well-known light form, var. Hdice. So, also, Argynnis 

 Paphia has a normal female and the dark melanic form 

 var. Valezina. Numerous other cases might be mentioned 



