16 



MASS. EXPERIMENT STATION BULLETIN 344 



26.6 ounces to the dozen); the small-egg type ranged from 56.9 grams (24.1 

 ounces to the dozen) downward during the hatching season. Minimum weight 

 for the medium- and large-egg types has been placed high so as to prevent as 

 far as possible overlapping with the upper extremes of the class below. 



Table 5 gives the summarized breeding results from the three phenotypes 

 of dams in each line through nine generations. 



Table 5. Hatching-Season Egg Weight 



Dams Classified by Hatching-Season 

 Egg Weight 



Number 



of 



Dams 



Number 



of 



Daughters 



Daughters Classified by 

 Hatching-Season Egg Weight 



Large 



Medium Small 



Large-egg dams produced about the same proportions of large, medium and 

 small-egg daughters in lines B and C. The medium-egg dams of line A gave 

 a lower percentage of large-egg daughters than occurred in either line B or line 

 C. The most notable fact with the small-egg dams was the greater proportion 

 of medium and large daughters in line C. This last observation indicates that 

 the line-A dams were more likely to be homozygous for small-egg genes and 

 further points to the epistatic nature of these small-egg genes. In the fourth 

 generation, hatched in 1931, the dams came from the different lines and not 

 exclusively from within each line. The daughters produced in this year in 

 line A slightly excelled those in line B for egg weight. This instance again 

 suggests that small-egg dams from lines B and C were less likely to be homozy- 

 gous for small-egg genes than were .the dams from line A. 



The data show that small-egg daughters came almost entirely from medium- 

 and small -egg mothers. The class of daughters laying large eggs were from all 

 three types of dams but largely from medium- and large-egg dams. Large-egg 

 daughters were produced in considerable numbers by medium dams, suggesting 

 that the gene reducing egg size of the dams segregates from the gene for large 

 size so that the large-egg phenotype of daughters appears. In nine generations 

 the percentages of large- and small-egg daughters were as follows: 



