32 



The average hatching abilitv of the sires' dams is .6977rt.005115, while that of 

 the sires' mates is .6488±. 005229. There is a difference of .0489 ±.0073 14, which 

 means that the males used as breeders came from dams of higher hatching power 

 than was inherent in the pullets to which they were mated. The almost identical 

 standard deviation for the two groups points to a similar variability in hatching 

 power for the two. 



The coefficient of correlation between the sires' mothers and their mates is .1579 

 rt .025856, a small but sensible correlation. Possibly this can be interpreted as 

 meaning that males tend to show a phenotypical hatching power comparable with 

 that of their dams. In selecting cockerels for breeders, hatching power of their 

 dams is something of a guide to their ability to contribute hatching power to the 

 eggs they fertilize. There is considerable probability that the male does influence 

 the hatching power of his mates' eggs. 



Section 10. Relation of Sire's Average to his Daughters' Individual Fertility. 



In considering the fertilizing and hatching power of males, it is necessary to use 

 some measure of their phenot3^pical character. This fact has been pointed out by 

 Pearl ('09) and, as he states, the average fertility and hatching power of hens 

 mated to a male may be used as his index. In table 10 the average fertility of 

 each sire from his different mates is tabulated against the fertility of each of his 

 daughters. This average figure for each sire is thus inserted a number of times to 

 correspond with the number of his daughters that were used as breeders. 



