39 



The fertiUty mean has fluctuated appreciably from year to year and has not 

 increased during the past six j^ears. The low fertilitj^ of 1923 can be attributed to 

 no other cause than adverse weather conditions throughout the \\'inter and spring 

 months. The majority of the males seem to have suffered from more or less frosting 

 of combs and wattles during the winter of 1922-23. The basis of selecting breed- 

 ing males for 1923 was not voluntarily changed from that of previous years. The 

 general deduction must therefore be made, as Pearl ('09) has done, that fertilit}' 

 is dependent largely upon environmental factors and that it is not an inherent char- 

 acteristic that is transmitted in inheritance. 



Table 16 indicates an increase of .1141 ±.0206 in mean hatchability from 1913 to 

 1923. This increase is mathematically significant. There has been a gradual 

 upward trend in mean hatching power since 1915. This increase has accompanied 

 the use of breeding pullets and breeding cockerels from mothers showing good 

 hatching power. The .04 drop in hatchability in 1923 is within the range of prob- 

 abilit}" and need not be considered. 



Relatiox of Male to the Hatching Power of his Mates' Eggs. 



Unmistakable evidence is available to show that the male contributes to the 

 hatching power of his mates ' eggs. For want of any more suitable term we have 

 used "male's phenotypical hatching power" to express the male's part. In table 

 9 a positive correlation coefficient of .1579±. 025856 was observed between the 

 sire's dam, and his phenotypical hatching power. A sensible correlation could not 

 exist unless the male contributes to the hatching power of his mates' eggs. 



The most conclusive evidence that the male influences the hatching power of his 

 mates ' eggs lies in the fact that the same hen shows different hatching power when 

 mated to different males in successive years or even in the same year. Such data 

 should be placed beside data showing the degree of constancy of hens in hatchability 

 when mated to the same male on successive years. No data are available on the 

 last-named question from our flock, although table 3 brings out a degree of cor- 

 relation between first and second year hatchability in hens, amounting to .4346± 

 .034409. The correlation should be much greater if the male did not play a part. 

 In section 5 a sensible correlation between mothers and daughters was discovered. 

 Reference to the constants calculated from table 5 shows that the hatching power 

 of a hen is an uncertain guide to the probable hatching power of her daughters. 

 The relative magnitude of the standard deviation of dams and daughters indicates 

 that the phenotypical hatching power of a hen is an uncertain index of her true 

 genetic constitution. This fact would seem to indicate that the male obscures the 

 true genotype of the hen. 



Data from the flock of the Massachusetts Agricultural Experiment Station on 

 the constancy of hatching power in males is very limited. In table 17 a comparison 

 is made between the first-j^ear hatching power and second-year hatching power of 



