]?ERTIUTY AND HATCHING OF EGGS. I25 



eggs infertile. It is difficult to see how anyone can attribute 

 the infertiUty of the eggs of No. 18 to the cockerel (No. 65) 

 when in the same pen No. 414 made such a fine record in 

 respect to fertility. To take another example, in pen 10 No. 

 707 produced no infertile eggs. Every egg which this pullet 

 produced between February and June — 30 in all — was fertile, 

 yet in this same pen and with the same cockerel, pullet No. 415 

 had 50 per cent and pullet No. 438 had 45 per cent of their eggs 

 infertile. If one attempts to account for the poor performance 

 of Nos. 415 and 438 in regard to fertility as due to some 

 inherent fault in cockerel No. 5 he is at once confronted by 

 the perfect record of fertility made by No. 707. In pen 11 

 again, there are wide extremes in regard to fertility. Pullet 

 No. 197 had but 12 per cent of her eggs infertile while with 

 the same cockerel pullet No. 20 had 73 per cent of her eggs 

 infertile. In pen 18 pullet No. 410 had but 3 per cent of her 

 eggs infertile, while pullet No. 784 had 47 per cent infertile. 

 Anyone who will take the trouble to study Table VII carefully 

 will find just as wide extremes of fertility shown by the pullets 

 in other pens. 



The same thing is apparent in the data of Table VIII show- 

 ing that this result is not something peculiar to one single season 

 or set of birds. Thus in pen ii there were four birds (1063, 

 1073, 1076, 1082) that produced no infertile eggs throughout 

 the breeding season, though the total numbers of eggs laid by 

 these birds during the season were : 23, 26, 26, 36. Yet in this 

 same pen T071 had 100 per cent, and 1078, 87 per cent, of infer- 

 tile eggs. 



The facts set forth in these tables make it absolutely certain 

 that there are wide differences in the breeding ability (meas- 

 ured by fertility of eggs) of different females, which are quite 

 independent of the relative ability of the male birds running 

 with the females as breeders. 



2. An examination of the last column of the table indicates 

 that there was proportionately much less variability among the 

 cockerels used as breeders than among the pullets, in respect 

 to their influence in determining the fertility of eggs. In iqoS 

 with the exception of three pens (Nos. 13. 17 and 21) the fer- 

 tility performance of the cockerels runs very evenly. Further- 

 more, a studv of the table shows that in two out of these three 



