HA1"K OF LAYING AXD KGCI PRODUCTION 193 



broodiness is in a incasuro positively forrelated witli winter clutch size. 

 From the standpoint of annual fecundity, however, the broody trait should 

 he eliminated as Hays and Sanborn (loc. cit.) show. 



GENERAL SUMMARY. 



Four measures of intensity have been considered in relation to fecund- 

 ity; namely, first sixty-day egg record, mean size of winter clutch, net 

 winter rate, and annual rate. The data have been secured over a ten-year 

 l)eriod on succeeding flocks from the same foundation with reasonably 

 constant environmental conditions. From the standpoint of tlio breeder, 

 mean size of winter clutch is the ujost satisfactory criterion of intensity 

 because it can be accurately determined and because it is inherited in 

 Mendelian fashion. 



In studying the correlation between these four measures of intensity 

 ;ind different environmental conditions and inherited traits affecting fecund- 

 itj- as well as their correlation to winter and annual egg production, the 

 following facts appear: 



1. There is a positive correlation between first sixty-day egg record 

 and subsequent winter record of .3445 ±.0100. Such a correlation shows 

 something of a tendency of production for the first sixty days to be asso- 

 ciated with a somewhat similar production for the next two months. But 

 production for both the first and last half of the winter period is often 

 reduced by the onset of inherited winter pause, making the absolute num- 

 ber of eggs laid during any part of the winter season an unreliable cri- 

 terion of intensity. 



2. The number of eggs that a pullet lays during the first sixty days 

 of laying is correlated with the number she lays for the remainder of the 

 year; yet the degree of correlation is less than with some other measures 

 of intensity. 



3. Size of winter clutch is inherited on a two-factor Mendelian basis. 



4. Size of winter clutch is not affected by hatching date. 



5. Factors for early sexual maturity indicated by age at first egg arc 

 linked with factors for large clutch size. 



6. Body weight at first egg and mean winter clutch size are negatively 

 correlated to a moderate degree. 



7. Winter egg production is intimately correlated with mean winter 

 clutch size making clutch size a valuable criterion of winter intensity. 



8. The correlation between annual egg record and mean winter clutch 

 size is positive and of sufficient magnitude to establish winter clutch size 

 as a good measure of intensity. 



9. Net winter rate is very similar to mean winter clutch size in rela- 

 tion to hatching date, age at first egg, and weight at first egg. 



10. Net winter rate is somewhat more intimately correlated with win- 

 ter egg yield than is mean winter clutch size, but the former is a less 

 specific measure of intensity alone because of winter pause. 



11. Net winter rate shows a coefficient of correlation of +.4769 ±.0104 

 with annual egg record compared with a coefficient of -f-.3544 ±.0117 be- 

 tween mean winter clutch size and annual record; but the former is not 

 as valuable a criterion of intensity as the latter because of winter pause 

 disturbance^. 



