502 Studies in the Theory of Descent. 



IV. 

 SUMMARY AND CONCLUSION. 



THE question heading the second section of this 

 essay must at the conclusion of the investigation 

 be answered in the negative. The form-relation- 

 ship of the larvae does not always coincide with 

 that of the imagines, or, in other words, a system 

 based entirely on the morphology of the larvae does 

 not always coincide with that founded entirely 

 on the morphology of the imagines. 



Two kinds of incongruence here present them- 

 selves. The first arises from the different amount 

 of divergence between two systematic groups in 

 the larvae and in the imagines, these groups being 

 of equal extent. The second form of incon- 

 gruence consists essentially in that the two stages 

 form systematic groups of different extents, either 

 the one stage constituting a group of a higher 

 order than the other and therefore forming a 

 group of unequal value, or else the two stages 

 form groups of equal systematic value, these 

 groups, however, not coinciding in extent, but the 

 one overlapping the other. 



This second form of incongruence is very 



