520 THE AMERICAN NATURALIST [Vol. XL V 



son Eye, while w represents the same cell organ, or 

 rather the corresponding organ, in another variety, 

 which does not perform this same function in the same 

 way under similar conditions. The symbol w need not 

 imply that the power of performing any function is lost. 

 It is here meant to imply only that the function is not 

 performed in such manner as to produce the effect that 

 W would have produced had it been present. Another 

 way of putting it is that W represents a function per- 

 formed, while w represents that the function is not per- 

 formed. With this understanding of what is meant by 

 a Mendelian " factor," we may proceed to examine the 

 hypotheses which explain the statistical results given 

 above. 



The behavior of the cross : small eye X solid color in- 

 dicated that these two types differ in two factors which 

 are transmitted independently of each other. Let us 

 represent these factors as they appear in fully pig- 

 mented peas by W and H, and in small-eyed peas as w 

 and h. This implies, according to my conception of 

 Mendelian factors, that some cell organ (W), probably 

 a chromosome, performs a certain function in certain 

 races of peas that is either not performed, or is per- 

 formed differently, by the corresponding organ (w) in 

 another race of peas. A similar remark applies to H 

 and h. With reference to these two factors, the formula 

 of fully pigmented peas may be written WWHH, and of 

 small-eyed peas wwhh. We have already seen that the 

 Hoi stein type differs from the type with small eye in 

 one factor; also from fully pigmented in one factor. 

 Hence it must have either the formula WWhh or wwHH. 

 That is, in one of the two factors concerned it is like 

 Solid Color, in the other, like Small Eye. We may 

 therefore take wwHH as the formula of the Holstein 

 type. In an exactly similar manner we arrive at the 

 formula WWhh for the Watson type. We may bring 

 these formulae together for purposes of comparison. 



(1) Solid Color : WWHH. 



(3) Holstein : wwHH. " 



