37o THE POPULAR SCIENCE MONTHLY 



will denote the presence of the ovary or the $ sex determiner. Then / 

 will denote the absence of femaleness and the absence of an ovary. 

 Obviously a separate letter is not needed for this "anatomical factor," 

 since the presence of an ovary is the objective criterion of the existence 

 of the female sex, 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 L x . 



3. The "second production" factor. This is a second physiological 

 factor, which in coexistence with F and L x leads to high fecundity. 

 The presence of this factor will be denoted by L 2 and its absence by the 

 corresponding small letter. When F and L x are present the addition of 

 L 2 makes a winter production of over 30 eggs. If F is present and L x 

 absent the presence of L 2 leads to a winter production of under 30 eggs. 

 Thus either L x or L 2 alone makes a record of 30 eggs. They are inde- 

 pendent determiners of this degree of production. It should be pointed 

 out, however, that in spite of their equivalence in this regard the factors 

 L x and L 2 are not qualitatively the same. That is, the increased pro- 

 duction when L x and L 2 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 L x present in a bird it does 

 not make her a high producer. L 2 may be considered an excess produc- 

 tion factor, which erects a superstructure on the foundation furnished 

 by L x . In the absence of L x it lacks the foundation from which 

 to start, and hence only can build about as high as L x would alone. Of 

 course, it will be understood that in the presence of / (absence of female 

 sex and ovary) these physiological fecundity factors L x and L 2 are 

 simply latent. 



Using the letters in the manner defined above, and with the usual 

 Mendelian method of writing gametic and zygotic formula?, the data 

 indicate that there exist 9 different types (in respect to fecundity) of 

 Barred Plymouth Rock males, 6 types of Barred Plymouth Bock 

 females, 3 types of Cornish Indian Game males, and 3 types of Cornish 

 Indian Game females. The only point needing particular attention in 

 reference to these formulas is that the factor L 2 , the excess production 

 factor, behaves in inheritance as a sex-limited or sex-correlated char- 

 acter. It is repelled by the female determiner F. It is thus like the 

 barred pattern factor in the Barred Plymouth Bock fowl. 3 In conse- 

 quence gametes of the type FL 2 are never formed. Any gamete which 

 bears F does not, under any circumstance, ever carry L 2 . All females 



s Cf . Pearl, R., and Surface, F. M., Arch. f. Entwick. Mech., Bd. XXX., pp. 

 45-61, 1910, and Science, N. S. ; Vol. XXXII., pp. 870-874, 1910. 



