458 Studies in the Theory of Descent. 



Among the Alpine species many other such 

 cases may occur, but these could only be dis- 

 covered by making investigations having special 

 reference to this point. Of the Alpine butterflies, 

 for example, not a single species can have been 

 reared from the caterpillar ; for this reason but few 

 observations have on the whole been given by 

 entomologists respecting the Alpine larvae, which 

 are not known sufficiently well to enable such a 

 question to be decided. 



The investigation of the form-relationships 

 existing between larvae on the one hand and 

 imagines on the other has thus led to the follow- 

 ing results : 



We learn on comparison that incongruences or 

 inequalities of form-relationship occur in all sys- 

 tematic groups from varieties to families. These 

 incongruences are of two kinds, in some cases 

 being disclosed by the fact that the larvae of two 

 systematic groups, e. g. two species,- are more 

 closely related in form than their imagines (or 

 inversely), whilst in other cases the larvae form 

 different systematic groups to those formed by the 

 imagines. 



The results of the investigation into the occur- 

 rence of incongruences among the various sys- 

 tematic groups may be thus briefly summarised : 



Incongruences appear to occur most frequently 

 among varieties, since it very frequently happens 

 that it is only the larva or only the imago which 



