INHERITANCE OF FECUNDITY 175 



(1) An anatomical factor. This is basic. It consists in the 

 presence of a normal ovary, the primary organ of the female 

 sex. In the following analysis a separate letter will not be used 

 for the designation of this factor but instead it will be understood 

 to be included in the letter denoting the presence of the female sex. 

 That is, F will denote the presence of the female sex or its deter- 

 miner, and the presence of the ovary. The letter / will denote 

 presence of the male sex (the absence of the female sex deter- 

 miner from the symbolic standpoint) and the absence of an 

 ovary. Obviously a separate letter is not needed for this 'ana- 

 tomical factor' since the presence of an ovary is the objective 

 criteron of the existence of the female sex, and its absence of the 

 existence of the male sex. 



(2) The first production factor. This is the primary physio- 

 logical factor which in coexistence with F makes the bird lay eggs 

 during the winter period. Quantitatively it may be taken as 

 determining a winter production of more than zero eggs and less 

 than 30. The presence of this factor will be denoted by Li and 

 its absence by h. 



(3) The second production factor. This is a second physio- 

 logical factor, which in coexistence with F and Li leads to high 

 fecundity. The presence of this factor will be denoted by Li 

 and its absence by U. When F and Li are present the addition 

 of Li makes a winter production of over 30 eggs. If F is present 

 and Li absent (Zi) the presence of Lo leads to a winter production 

 of under 30 eggs. Thus either Li or L^ alone makes a record of 

 30 eggs. They are independent determiners of this degree of 

 production. It should be pointed out, however, that in spite of 

 their equivalence in this regard, the factors Li and L^ are not 

 qualitatively the same. That is, the increased production when 

 Li and L2 are both present, is not because there are present two 

 ' doses' of the same determiner. The proof of this is found in the 

 fact that when there are two 'doses' of Li present in a bird it 

 does not make her a high producer. L2 may be considered an 

 excess production factor, which erects a superstructure on the 

 foundation furnished by Li. In the absence of Li L2 lacks the 

 foundation from which to start and hence only can build about as 



