No. 530] 



THE MENDELIAN It AT 10 



terminants are related as dominant and recessive, re- 

 spective^, or whether they blend. 



Suppose p is recessive and q is dominant in the Men- 

 delian sense, we at once obtain from (2) the general 

 expression for the alternative inheritance or 



(RR + 2DR + DD)" 

 where n refers to the number of allelomorphic pairs of 

 characters, and the expansion gives a strict Mendelian 

 ratio for any number of allelomorphic pairs of char- 

 acters. 



On the other hand, if we consider that p and q determi- 

 nants blend with an equal intensity the series (2) will 

 give all grades of hybrid characters between the two pa- 

 rental types, the frequency of which is proportional to 

 the successive terms of a symmetrical point binomial 

 curve, and the maximum frequency will be associated 

 with the midparental types (case of equipotency). 

 Castle's ('09) experiments with the length of the ear of 

 rabbits illustrates this case. 



Again let us suppose that /; and q determinants blend, 

 but with unequal intensity. According as p or q is pre- 

 potent, the zygote will resemble more closely one or the 

 other parent. The frequency of each type of zygote 

 again will be represented by the symmetrical point bi- 

 nomial curve. Thus the present series (2) represents 

 both alternative and blended inheritance according to 

 the behavior of the determinants. 



The fact just mentioned, that the expressions for both 

 blended and alternative inheritance are obtained from 

 the same series which represent the gametic composition, 

 suggests that we may possibly obtain cases of blending 

 in character which normally follow the law of the alter- 

 native inheritance, and vice versa, and further we may 

 even obtain both blended and alternative inheritance in 

 the same offspring by subjecting the hybrid parents to 

 different conditions, provided by such treatment we can 

 modify the behaviors or functional activity of the de- 



