572 EXPERIMENT STATION RECORD. 



There was proportionately less variability among the cockerels used as 

 breeders than anions: the jinllets in respect to their inflnence in determining the 

 fertility of eggs. 



"The present statistics indicate that there is no correlation ^yhatever between 

 winter (November to March) egg prodnction and the fertility of eggs laid 

 dnring the subsequent hatching season. In other words, the eggs of the heavy 

 winter layer are not more likely on the average to be infertile than are those 

 of the light winter layer, other conditions being the same. 



"There is a distinct correlation between the winter (November to March) 

 egg production and the percentage of fertile eggs hatched during the subse- 

 quent breeding season. This correlation is of such sort as to indicate that in 

 general (he higher the winter egg production of a particular bird the lower will 

 the percentage of that bird's fertile eggs hatched probably be and vice versa. 



"The i)i'esent statistics do not show any marked superiority of hens over 

 pullets in respect to breeding performance so far as either fertility or hatching 

 quality of eggs are concerned. It must be understood that this is merely a 

 statement of fact and does not constitute any recommendation for the use of 

 either pullets or hens as breeders. That question involves more than the two 

 factors here under discussion. 



" There is no indication that the fertility of eggs in the pullet year and in the 

 second breeding year are in any way correlated. In other words, a bird whose 

 eggs run high in fertility in the pullet year is as likely as not to produce eggs 

 running low in fertility the second year, and vice versa, when mated with the 

 same male or with males of essentially equal breeding ability as shown by their 

 pen averages. 



" There is a significant positive correlation between the percentage of fertile 

 eggs hatched in the pullet year and in the second breeding year. In other words, 

 the bird whose eggs are of superior hatching quality in the pullet year will, on 

 the average, show the same characteristic in her second year." 



A study of inheritance of fertility and of hatching quality between mother and 

 daughter, between father and daughter, and between sisters showed that there 

 is no evidence that the character "fertility of eggs" is in any degree inherited. 

 The character " hatching quality of eggs " is definitely inherited in the female 

 line and apparently also in the male line. 



" Taking all the results of the paper together, it is evident that fertility and 

 hatching quality of eggs are very different characters. While there are great in- 

 dividual differences among different females in resjiect to the fertility of their 

 eggs, even when mated to the same male, it still remains the fact that this char- 

 acter, as compared with hatching quality of eggs, is to a very large degree in- 

 fluenced by external circumstances. ... On the other hand, the hatching qual- 

 ity of eggs is an innate constitutional character just as much intrinsic as anj 

 other physical character, such as shape of body or length of limb. 



" The present study has shown that high winter egg production has, on the 

 average, an adverse effect on the hatching quality of the eggs produced by the 

 same birds in the subsequent hatching season. This again can probably be re- 

 garded as the result of a reduction of constitutional vigor following heavy lay- 

 ing. Continued heavy egg production involves great metabolic activity on the 

 birds' part in the transformation of matter and energy and must fatigue the 

 organism. . . . 



" The data presented in this paper emphasize the importance in practical 

 breeding work of (a) the selection of breeding stock with reference to constitu- 

 tional vi^'or or vitality, (b) the muiuteuauce of the breeding birds in u vigorous 



