22 



almost complete independence between degree of fertility and hatchability. 



From the genetic standpoint, the results in table 1 are significant. The table 

 shows that a flock of pullets may carry the factors that are conducive to high fer- 

 tility and yet lack the ability to be good hatchers. Stated simply, these results 

 mean that the degree of fertiUty in a hen's eggs is an entity independent from the 

 hatchability of her eggs. 



The mean fertility shown in table 1 is .6883, while the mean hatchability is .6379. 

 Of the total eggs laid by these pullets during the hatching season, 68.83 per cent 

 were fertile, and 63.79 per cent of these fertile eggs hatched. Two possible avenues 

 are open for increasing the number of chicks per pullet. First, Increase the per- 

 centage of total eggs that are fertile. Second, Increase the percentage of fertile 

 eggs that hatch. Selection for high fertihtj^ and high hatchability is possible only 

 where hens are used as breeders. Hens have been used to only a very minor extent 

 in this flock. Hence there has not been much progress in fertility and only moder- 

 ate progress in hatchabilitj^, as will be shown in section 17 of this bulletin. The 

 general deduction must be made, therefore, from the study of table 1, that fer- 

 tility and hatchability are independent of each other. The stability of each char- 

 acteristic may next be considered. 



Section 2. The Constancy of Fertility in Hens. 

 In order to test the constanc}^ of fertiUtj'' in hens, the records of 253 

 female breeders that were used first as pullets and again as yearlings have been 

 placed in table 2. In practicall3^ all cases a different male was mated to these 

 females the second year. If there is a sensible correlation in fertihty between the 

 pullet-year record and the yeai-hng record from the same hens, the natural assump- 

 tion must be that degree of fertilitj^ is more or less constant in the female, regard- 

 less of the male to which she is mated. 



Table 2. — Correlation Between First and Second-Year Fertility. 



