PEARL— SEX RATIO IX DOMESTIC FOWL. 425 



It is to be regretted that more of those who have used poultry as 

 experimental material have not kept and published accurate and 

 complete figures of sex production. 



In any case the immediate problem before us is clearly to at- 

 tempt by analysis of the figures to learn what influence various 

 factors may have in the production of the excess of females plainly 

 shown in the extensive statistics of the present paper. The chromo- 

 somal mechanism of sex determination in the individual case would 

 lead us to expect an equality of the sexes in statistically large num- 

 bers. But it is plain that, even with very large numbers, no such 

 equality is attained. There must be reasons, scientifically ascertain- 

 able, for this deviation. It is our problem to find what these reasons 

 are. 



In undertaking such analysis let us first see whether the excess 

 production of females is a secularly regular phenomenon in this 

 stock and under our conditions. 



The mean sex ratios for each year for families of lo and over 

 are set forth in Table VIII. 



TABLE VIIL 



Showing the Yearly Changes ix Mean Sex Ratio. Families of io and 



Over. 



Year. Mean R 



d" 



igo8 46.16 + 1.07 



1909 48.33 ± -69 



1910 49.96 + .78 



1911 47.08 + .79 



1912 49-59 + 77 



1913 49.999+ .81 



1914 49.83 + .62 



1915 46.46 + .86 



The data of this table are shown graphically in Fig. i. 



From the table and diagram it is evident that the excess of fe- 

 males is not a sporadic, but rather a regular phenomenon in our 

 stock and conditions. While at times the ratio comes very close 

 to 50 (e. g., in 1913) it never quite reaches that value. The fluctua- 

 tions of the ratio in successive years appear to be entirely random. 



