174 RAYMOND PEARL 



tend to make the number of zero birds observed smaller than that 

 expected on theory. 



(3) Owing to the factors of.environmental influence and somatic 

 fluctuations it is difficult to classify birds in respect to fecundity, 

 which have winter records near the boundary point, 30 eggs. 

 Some birds bearing genes for a production of under 30 eggs will 

 actually lay 31, or 32, or 33, etc. The point considered under (2) 

 again comes into play here. A bird may bear the genes for an 

 'Under 30' record, and actually make such a record during the 

 true biological winter cycle or period. But if it begins the spring 

 cycle early (i.e., before March 1) it gets credited on its winter 

 record with the eggs which it lays in the last days of February, 

 but which biologically belong with the spring production, and in 

 this way its apparent winter record becomes something over 30, 

 while its real winter production was under 30. 



All these factors obscure and render difficult the critical classi- 

 fication and interpretation of the results. Allowance must be 

 made for their influence. 



B. Symbolic analysis. After some consideration it has seemed 

 advisable to undertake the presentation of what is at best a com- 

 plicated matter in the following order. First a symbolic analysis 

 of the inheritance of winter egg production will be given. Then 

 the actual statistics of production covering a period of four 

 years will be given, and it will be shown that these objective data 

 are in substantial accord with the symboHc account. The facts 

 can be presented in this way much more clearly and simply, than 

 if the reverse order is followed. Without the clue of the sym- 

 bolic analysis to guide one through the maze of figures, one would 

 be hopelessly lost. It scarcely needs to be said that while the 

 order suggested seems undoubtedly the best for the presentation 

 of the results, it is precisely the opposite of that by which the 

 conclusions here set down were reached. 



Let us turn to the symbolic analysis. As has been pointed 

 out already there are to be distinguished, on purely biological 

 grounds, three factors involved in fecundity in the female fowl. 

 These are : 



