10 MASS. EXPERIMENT STATION BULLETIN 298 



two upper classes with respect to duration of iiiological year. The egg records of 

 (laughters from dams with short biological year did not increase up to 1927, and 

 the last two yearly means are not significant because of small numbers. The 

 superiority of the egg records of daughters from dams with a biological year ex- 

 ceeding 365 days appears to warrant the selection of such birds for breeding to 

 increase fecundity. 



Chart 2. Annual Egg Production of Daughters by Years. 



Summary 



A study is made on 911 Rhode Island Red females of twelve generations that 

 were trapnested for two full laying years and on a total of 2311 of their daughters 

 representing twelve generations. 



1. Duration of biological \-ear is intimateh' associated with early sexual 

 maturit>'. 



2. There is no significant relation between duration of winter pause and length 

 of biological year. 



3. Large winter clutch size or high intensity' shows a small but significant 

 positive correlation with length of biological year. 



4. Degree of broodiness shown by the number of nonproductive broody days 

 gives a negative correlation with duration of biological year. 



5. Annual persistency shows an intimate correlation with annual egg record. 



6. The egg record for the biological year is intimately correlated with the dura- 

 tion of the biological year. 



7. First- and second-year hatchability are indeiiendent of duration ol biologi- 

 cal \ear. 



S. Small body weight at first egg is associated with great length of biological 

 year. 



9. Heavy body weight at the close of the 365-day laying year is associated with 

 greater duration of biological year. 



10. Second-year egg production tends to be higher in birds show ing a biological 

 laying year greater than 365 days. 



