No. 530] 



THE MENDELIAN RATIO 



in:: 



of dominance, the formula reduces to either equipotent 

 or prepotent blending inheritance. From this stand- 

 point we may consider that blending inheritance is a 

 limiting case of alternative inheritance where either 

 dominance is absent (equipotency) or is imperfect 

 (heteropotency). If this hypothesis is accepted, then 

 Mendel's law of alternative inheritance may be taken as 

 the standard, and all cases referred to it or blending in- 

 heritance (though by this some more important features 

 of inheritance are not suggested) may similarly be made 

 the standard, the Mendelian ratios then becoming a 

 special case. 



In this connection Professor Davenport's ('07) view 

 on the law of potency is of great interest. As his view of 

 potency is so important, and especially as it clearly ex- 

 plains the relation between Mendelism and cases con- 

 sidered to be non-Mendelian, I shall quote his words at 

 some length. 



After quoting various cases of inheritance, Professor 

 Davenport says: 



Taking all cases into account, it is clear that Mendel's law does not 



Can we find a more general expression for the inheritance of charac- 



may be called the law of potency. At the one extreme of the series we 



offspring show a blend, or a mosaic between them. At the other extreme 

 is allelopotency. One of the two characteristics is completely recessive 

 to the other. Between the two extremes of equipotency and allelopo- 

 tency lies the great mass of heritable characteristics which when opposed 

 in heredity, exhibit varying degrees of potency. This sort of inherit- 

 ance may be called heteropotency. 



Thus Professor Davenport shows also that Mendelian 

 dominance is a particular case of potency, allelopotency, 

 though he did not state that blending inheritance is a 

 limiting case of Mendelism. 



Whether a new expression "the law of potency" 

 should be introduced as Professor Davenport has sug- 

 gested, or whether the various potencies may be consid- 



