Phylctic Parallelism in Mctamor/>hic Species. 42 1 



surrounding the base of the warts constitute inter- 

 mediate forms (Fig. 80). The last stage of the 

 German local form, unlike that of the Genoese 

 local form, is therefore very variable. 



The two forms, moreover, do not simply differ 

 in being more or less advanced in phyletic 

 development, but also in several other points. 

 As it is of great theoretical interest to show that 

 a species can develop local differences only in the 

 stage of larva, I will here subjoin the plain facts. 



The differences consist in that the Genoese 

 local form goes through five moults whilst the 

 German local form, like most caterpillars, has only 

 four moults. Further, in the Genoese form the 

 light green, which is also possessed by the German 

 form in the fourth stage, when it once appears, is 

 retained to the end of the larval development, 

 whilst in the fifth stage of the German form this 

 colour is replaced by a dull greyish-green (com- 

 pare Figs. 77 and 78). There is further a very 

 considerable difference in the earlier stages which 

 shows that the phyletic transforming process has 

 taken a quite independent course in the two forms. 

 Since the struggle between the green and black 

 retaining this idea appears to be quite finished 

 in the last stage of the Genoese form, we should 

 expect that the new colour, green, would now also 

 have encroached further upon the younger stages 

 than in the German form. Nevertheless, this is 

 not the case, but quite the reverse happens, the 



