FERTILITY AND HATCHING OF EGGS. 121 



All birds, 1909 — Fertility : percentage of standard deviation 

 in mean = 145.4%. 



Pullets only, 1909 — Fertility: percentage of standard devia- 

 tion in mean ^= 140.0%. 



Hens only, 1909— Fertility : percentage of standard deviation 

 in mean = 150.2%. 



1908 — Hatching quality, percentage of standard deviation in 

 mean = 48.3%. 



All birds, 1909 — Hatching quality, percentage of standard 

 deviation in mean :=: 47.7%. 



Pullets only, 1909 — Hatching quality, percentage of standard 

 deviation in mean = 52.3%. 



Hens only, 1909 — Hatching quality, percentage of standard 

 deviation in mean = 40.2%. 



These figures show that in proportion to the mean of the 

 characteristic, hatching quality is relatively much less variable 

 than fertility. Both of the characters— fertility and hatching 

 quality- — are, so far as may be judged from the present statis- 

 tics, highly variable as compared with other characters of 

 poultry which have been studied in this connection. 



5. From the data given in the preceding paragraph it 

 appears that in proportion to the mean the fertility of eggs 

 varied much more in 1909 than in 1908, while in respect to 

 hatching quality the relative degree of variability was substan- 

 tially the same in the two years. This would suggest that the 

 difference in housing conditions of the two years had a much 

 greater effect on the variability (as distinguished from the 

 absolute average condition) of fertility than on that of hatch- 

 ing quality. This, however, can, in the light of the present 

 data, be only a suggestion, the correctness of which must be 

 tested by further work. 



6. From the data of Table VI it appears that in 1909 the 

 yearling hens were superior to the pullets in regard to both the 

 average fertility and the average hatching quality of their eggs. 

 The difference between the two groups in mean fertility is, 

 however, hardly significant. More data are needed before any 

 final conclusion as to the relative ability of pullets and yearling 

 hens as breeders may be drawn. 



