24 



Constants calculated from Table 3. 

 Pullets' mean hatchability . 

 Pullets' standard deviation. 

 Yearling hens ' mean hatchability 

 Yearling hens ' standard deviation 

 Coefficient of correlation 



.5678±.011313 

 .2668db .008333 

 .4791±. 012963 

 .3057±. 009166 

 .4346 ±.034409 



The mean hatchability for pullets is .5678±. 011313. The mean hatchability 

 for the same birds as yearlings is .4791 ±.012963. There is a difference of .0887± 

 .0172 in favor of using pullet breeders. This difference is significant in the light of 

 its probable error. Stewart and Atvv'ood's ('09) records with White Leghorns do 

 not agree with these results. They found both the mean fertility and mean hatch- 

 ability to be higher in hens than in pullets. Their records are scarcely comparable 

 with ours because they did not compare the same birds. Furthermore, in a yearling 

 or two-year-old flock, most of the poor hatchers will have been discarded if tliey 

 were tested as pullets. Pearl ('09) obtained a slightly higher mean fertility in the 

 pullet year and an insignificant difference in hatchability between pullets and 

 yearlings, using the same flock of Barred Phinouth Rocks. 



The range of variability measured by the standard deviation is significantly 

 greater in the j'earling hens. This difference may possibly be ascribed to vari- 

 ability in physical condition in the older birds. Hatchabihty, however, seems to be 

 a trait that behaves with a good deal of constancy in hens. This fact makes the 

 individual hatching record valuable, at least in making use of a hen for several 

 years to increase flock numbers. The ability of the hen to transmit this hatching 

 power to her daughters will be considered in section 5. 



The coefficient of correlation calculated from table 3 is .4346 ±.034409. Hatch- 

 ability is therefore more constant than fertility, for the coefficient for fertility in 

 the same flock was only .2733. In breeding for high hatchability there is ample 

 justification for discarding the poor hatchers the first j^ear and retaining the good 

 hatchers to perpetuate the flock. 



Section 4. Correlation in Fertility between Mothers and Daughters. 



In order to discover if there is any relationship between mothers and daughters 

 in degree of fertility, the average fertility of pullet breeders has been correlated 

 with each of their daughters that were used for breeding as pullets. In case only 

 one daughter was used, there was but one insertion in the table. If a pullet dam 

 had more than one daughter used as a breeder she is paired with each of these 

 daughters and an insertion made in the table. 



