INHERITANCE OF EGG CHARACTERS 5 



Objects of This Investigation 



In planning this experiment several definite objects were kept constantly in 

 mind, the most important of which are the following: 



1. A determination of the possible genetic factors that act directly on egg 

 size up to January first, during the normal breeding season, and through 

 the entire first laying year. 



2. Genetic factors affecting external shell texture. 



3. Possible genes governing the shell character of the ends of the eggs. 



4. Genetic factors affecting the porosity of the egg shell. 



5. A genetic analysis of egg-shell color inheritance. 



6. Determination of possible genetic factors governing egg shape. 



Data Available 



Three lines were established during the hatching season of 1928 and carried 

 through nine generations, the last being hatched in the spring of 1936. Data 

 on egg weight for the last generation were completed only through the hatching 

 season. 



Line A was a small-egg line from pullet mothers. The first three generations 

 were produced by mothers with a mean December egg weight of 52 grams (22 

 ounces to the dozen). The fourth generation was from mothers selected from 

 the three different lines on the basis of a December egg weight of 52 grams. To 

 produce the fifth and sixth generations, mothers of line A were selected with a 

 52-gram egg weight in November. Generations seven, eight, and nine were 

 from mothers selected on the ability to attain an egg weight of 56.7 grams be- 

 tween 61 and 90 days after the first pullet egg. Generation four was the only 

 generation produced by some mothers outside of line A. 



Line B was developed for medium egg size. The first three generations of 

 pullet mothers were selected on the basis of a mean December egg weight of 

 57 grams (24.1 ounces to the dozen). The fourth generation was from pullet 

 mothers from the three different lines selected on the basis of a December egg 

 weight of 57 grams. The fifth and sixth generations were produced from pullet 

 mothers of line B laying 57-gram eggs in November. Generations seven, 

 eight, and nine were from pullet mothers showing a mean egg weight of 56.7 

 grams between 31 and 60 days from first egg. The fourth generation alone was 

 produced from females outside of line B. 



Line C was considered a large-egg line. The basis for selecting the mothers 

 to produce the first three generations was a mean December egg weight of 59 

 grams (25 ounces to the dozen). The fourth generation was from pullet 

 mothers from the three different lines showing the ability to lay 59-gram eggs 

 in December. The fifth and sixth generations were from pullet mothers of 

 line C laying 59-gram eggs in November. Generations seven, eight, and nine 

 were out of mothers laying 56.7-gram eggs within 30 days after the first egg. 

 Only generation four came in part from mothers outside of line C. 



The males siring each generation were cockerels. Three full brothers were 

 chosen, one to head each line each year. In order to avoid close breeding 

 these males were taken from another experiment. An effort was made each 

 year to secure males with large-egg ancestry. The object in using full brothers 

 throughout the experiment was to retain the greatest possible uniformity in 

 the male ancestry. 



The first five generations were hatched in eight weekly hatches from March 

 25 to May 15, and the last four generations three weeks earlier. 



