INHERITANCE OF EGG CHARACTERS 



15 



Table 4. — Breeding Value of Dams, Fast, Medium, and Slow or 

 Failing to Reach Standard Egg Weight 



E. The Inheritance of Egg Weight 



In previous sections egg weight has been considered during the winter 

 period, during the normal hatching season, and for the entire first laying year. 

 As indicated in section B, hatching-season egg weight is a close approximation 

 to the maximum egg weight of the first laying year. This maximum egg weight 

 offers a convenient basis for the study of genes concerned in the inheritance of 

 egg weight. The terms size and weight are used interchangeably in this report. 



In a previous report from this Station Hays (1929) suggested that two 

 dominant genes primarily affect egg size. Gene B was indicated as a dominant 

 producing eggs weighing 56.7 grams (2-ounce eggs) or more. Gene A is also 

 a dominant producing eggs weighing under two ounces in the hatching season. 

 This latter gene is epistatic to gene B and with it gives an intermediate egg 

 size, but below 56.7 grams. In these earlier studies large eggs (63 grams or 

 heavier) were not common. In recent years, by selective breeding, egg size 

 has been built up so that many individuals now lay eggs weighing 63 grams or 

 more. In the experiment being reported, results with egg weight require a 

 modification of the AB theory. 



An examination of the frequency distribution for egg weight during the 

 hatching season suggests modal classes at about 55-56 grams (23.5 ounces to 

 the dozen) and 61-62 grams (26 ounces to the dozen) as well as the large pro- 

 portion falling near the 57-gram (24 ounces to the dozen) class. In studying 

 the inheritance of egg weight, dams and daughters have been placed in three 

 phenotypes. The large-egg type laid eggs weighing 63 grams (26.7 ounces to 

 the dozen or more); the medium type ranged from 57 to 62.9 grams (24.2 to 



