194 



TECHNICAL BULLETIN 9 



The division of tlie population into high and low persistency groups in the 

 above table rests on a possible genetic foundation as already stated. The 

 mean persistency of the entire 2179 birds was found to be about 300 days as 

 section 1 shows. AVhen the point of division between high and low persist- 

 ency birds is taken between 314 and 315 days, there are 1136 individuals 

 classifying as high and 1043 as low in persistency. The low persistency class 

 ranges from 67 to 314 days while the high persistency class ranges from 315 

 to 366 days. The wide range for the low class enables them to bring the mean 

 persistency of the population down to 300 days even tiiough there are more 

 high-persistency birds than low-persistency birds in the above classification. 



A positive coefficient of correlation .3771 ±.0124 signifies that early hatch- 

 ing is associated with high persistency. Possibly early hatching better equips 

 the pullet for a long laying year because she begins to lay earlier in the fall 

 and is also able to finish her laying year under more favorable weather con- 

 ditions than is her late-hatched sister. These data signifiy, therefore, that 

 hatching before the middle of April tends to increase persistency for the 

 pullet year. 



(B) Relation Between Inherited Characteristics Concerned 

 WITH Fecundity and Annual Persistency. 



In the class of inherited characteristics concerned with fecundity the fol- 

 lowing will be considered in relation to annual persistency: Age at first egg, 

 weight at first egg, winter rate, length of winter pause, and total days broody, 

 all records being based on the pullet year. 



3. Correlation Between Age at First Egg and Annual Persistency. 



Both age at first egg and annual persistency have been found by Goodale 

 and Sanborn (loc. cit.) and by the writers to be of appreciable significance 

 in breeding for egg production. Both early maturity and high persistency 

 are essential in the high producer and for this reason their relation to each 

 other should be known. The identical group of birds studied in section 1 is 

 used to determine the following constants: 



Number of birds 

 Mean age at first egg 

 Age standard deviation . 

 Mean annual persistency 

 Persistency standard deviation 

 Coefficient of correlation 

 Regression age on persistency 

 Regression persistency on age 



Mean age at first egg is about 209 days, which is a figure falling within the 

 limits of genetic early maturity. Age at first egg is a characteristic that 

 fluctuates widely, and in this particular population the extremes are 140 and 

 379 days, respectively. Class intervals of ten days for age have been used in 

 these correlation studies. 



The mean annual persistency of the population is about 300 days. The 



