ANNUAL PERSISTENCY AND EGG PRODUCTION 



195 



extremes are 67 and 366 days, respectively. Tlie standard deviation for per- 

 sistency is very large and indicates that a number of factors is concerned. 



The negative coefficient of correlation is of such magnitude as to suggest an 

 intimate relation between age at first egg and annual persistency. Those 

 pullets that lay at an early age ajjpear to he much more persistent layers 

 than those maturing later. Herein lies a partial explanation of the significant 

 relation between early maturing and high annual production. These studies 

 point to age at first egg as a criterion of importance for predicting per- 

 sistency. 



4. Con-elation Belween A(je at First Egg Below the Mean and High Per- 

 sistency. 



The population has again been divided into the two possible genetically dif- 

 ferent clas.ses for persistency as in section 2. These classes have been tabu- 

 lated against age below the mean and age above the mean as follows: 



Coefficient of correlation ..... -j-.6816±.0077 



A very intimate correlation is shown by the above coefficient between early 

 sexual maturity and high persistency. This relationship is very significant to 

 the breeder, disclosing possible genetic linkage between two desirable inherit- 

 ed traits that may later be cleared up on a factorial basis. 



5. Correlation Between Weight at First Egg and Annual Persistency. 



Body weight is a convenient standard to use for selection purposes. Weight 

 in poultry is inherited on a multiple factor basis according to Punnett and 

 Bailey (1914.). If weight should prove a criterion of persistency, its value 

 for culling purposes soon after pullets begin to lay is very evident. Weight 

 records are available on 212-5 of the birds being studied, and when correlated 

 with persistency give the following constants: 



Number of birds 2125 



Mean weight at first egg 5.58 



Weight standard deviation ±.75 



Mean annual persistency 302.64 



Persistency .standard deviation .... ±58.00 



Coefficient of correlation — .3225±.0131 



Regression weight on persistency .... — .004 



Regression persistency on weight .... — 25.002 



