FERTILITY AXD HATCHIXG OF EGGS. 155 



sive, years, indicating to what an extent it is a character innate 

 in the individual, and the other in the actual inheritance of this 

 character. But if hatching quality is inherited it means that it is 

 a character which can be improved by selective breeding. This 

 we believe to be the case and in the breeding work of the 

 Station this idea is being put into practice.* 



The fact must not be lost sight of. however, that to be effec- 

 tive this selection cannot be of the "mass" character. It has 

 been seen that in the moss there is no sensible inheritance of 

 hatching quality from parent to offspring. The point is that 

 some indknduals possess the capability of transmitting good 

 hatching quality of eggs to their progeny, or are prepotent with 

 respect to this character. Other individuals, li-hich may be 

 themselves just as good in respect to hatching quality of eggs, 

 totally lack the ability to transmit this quality to the progeny. 

 Simply selecting birds indiscriminately on the basis of their ozim 

 hatching records is as likely to get the latter kind of birds as the 

 former, and will make no permanent improvement in the straia. 

 But if a system of pedigree records is at hand an advance with 

 each generation is possible because one by one those "blood 

 lines" in which the transmitting ability or prepotency is absent 

 can be discarded in favor of those in which it is present. In 

 passing it may be said that these considerations apply with 

 exactly the same force to breeding for egg production as to 

 breeding for hatching quality. This point will be more fully 

 discussed in a future paper. 



The data presented in this paper emphasize the importance 

 in practical breeding work of (a) the selection of breeding 

 stock with reference to constitutional vigor or vitality, (b) the 

 maintenance of the breeding birds in a vigorous condition by 

 proper methods of housing and feeding, and (c) paying atten- 

 tion to the actual breeding ability (as shown by hatching per- 

 formance) of the stock and the exercise of selective breeding 

 to improve this character. 



It is. of course, obvious that the present paper covers onlv a 

 small part of the general subject of the factors which influence 



* Cf. a paper by the present writers having the title "Selection Index 

 Numbers and their Use in Breeding" appearing in Amer. Xai. Vol. 



XLIII, Xo. 511, July 1CXXI, pp. 385-400. 



i 



