27 

 Pearl ('09) reix)rts a correlation coefficient of only .031 ±.072 between mothers 

 and daughters in hatchahility, but only 87 indi\iduals were studied. Dunn ('23) 

 states that he was unable to separate high and low hatching lines by two genera- 

 tions of selection. He did find, however, that families tend to become different 

 in hatching power and to retain this ditTerence. 



Table 5 clearly indicates that hatching power is transmitted from mother to 

 daughter, even though rigitl control of the many environmental factors that modify 

 the liatching power is very difficult. These varying conditions often obscure the 

 tiiie hatching ability of the pullet as an individual. The use of t)re('ding females 

 of liigh hatching power is the first stej) toward improving the flock in this par- 

 ticular characteristic. We have shown in section 3 that the hatching power 

 of a pullet is sensibly correlated with her later hatching power. Follow this by 

 using breeding hens that transmit high hatchability to all of their daughters. The 

 male 's part in heredity of hatchability will next be considered. 



PART II. 



The Male's Role in Inheritance op Fertility and Hatchability. 



Section 6. The Constancy of Fertility in Males. 



In studying the question of the inheritance of fertility and hatchability, much 

 importance should be attached to the male side of the flock, for the male is more 

 than half the flock from a genetic standpoint because each male furnishes half the 

 inheritance to the progeny of several hens. 



The measure of the male's fertilizing ability is the mean degree of fertility from 

 his different matings. The accuracy of such a measure will of course depend upon 

 whether or not high fertility is governed in inheritance by dominant or recessive 

 factors, or whether it is independent of Mendelian factors. If high fertility depends 

 upon recessive factors, we should expect less variation in the daughters from a hen 

 that carries these factors pure, so that she herself is genetically highly fertile, than 

 would be the case if high fertiUty is dependent on dominant factors and these were 

 not in homozygous condition. The fact that manifestation of fertility in the eggs is 

 probably dependent on both miile and female makes the classification of either 

 males or females with regard to this characteristic a hazardous undertaking. A 

 careful analysis of the results from mating specific males to a number of females 

 in successive years with conditions kept uniform would help much to explain this 

 confusing problem. 



The problem of the constancy of a male's ability to transmit a certain degree of 

 fertility to his daughters may be elucidated by correlating the fertility of his 

 daughters sired during his first breeding year with that of his daughters sired during 

 the second breeding year, using pullet records in all cases. In other words, if males 

 transmit a certain degree of fertility to their daughters in successive years, a posi- 

 tive correlation will exist. Such a tabulation is made from data available in table 

 6. Unfortunate!}'', records on only 51 pairs of daughters are obtainable for study. 

 The number is small because few males are used as breeders after their cockerel 

 year. 



