358 Studies in the Theory of Descent. 



POSSIBLE GENEALOGICAL-TREE OF THE GENUS DEILEPHILA. 



The circles indicate the phyletic stages IV. VIII. ; the eighth 

 is only reached by Niccza, and is distinguished from the seventh 

 chiefly by the ontogeny, in the third stage of which the seventh 

 phyletic stage is reached, whilst in RufihorbicE and Dahlii this 

 stage is reached in the fourth ontogenetic stage. The phyletic 

 stages indicated by queries are extinct, and only known through the 

 ontogeny of existing species. It must be understood that this 

 pedigree expresses only the ideal and not the actual relations of 

 the species to one another. Thus, it is possible that Hippophaes 

 is not the parent-form, but an unknown or extinct species, which 

 must, however, have possessed the same marking, and so on. 



