176 



TECHNICAL BULLETIN 8 



This positive coefficient of correlation is of sufficient magnitude to establish 

 a definite relationship between early hatching and the appearance of winter 

 pause. This being the case, tiie assumption must be made that inheritance is 

 not the sole controlling force concerned in the manifestation of winter pause. 



C). Correlation Belxceen Date of First Egij and Length of Winter Pause. 



I'he date on which a pullet lays her first egg is dependent upon many 

 factors. Among the most important of these arc hatching date and age at 

 first egg. Environmental influences such as character of ration, amount of 

 free range, and weather conditions may, to some extent, hasten or retard 

 the date of first egg. Date of first egg is important economically if not 

 biologically. 



The relation between date of first egg and duration of winter pause has 

 been determined by means of the coefficient of correlation on the same group 

 of 2134 birds studied in section 7. The birds were again classified as to 

 winter pause into class intervals of ten days. The class interval used for 

 date of first egg was fifteen days. Constants calculated are as follows: 



Number of birds ........ 2134 



Mean date of Ijeginning to lay (Oct. 29) . . 5.88 



Date of beginning to lay standard deviation . . ±2.13 



Mean length of winter pause 32.26 



Winter pause standard deviation .... ±21.92 



Coefficient of correlation —.320-5 ± .0131 



Regression of date of first egg on winter pau.se . . — .031 



Regression of winter pause on date of first egg . . — 3.297 



The date on which the birds l)egan to lay ranged from August l(i to March 

 29 making 15 class intervals. Its standard deviation may be expected to be 

 of considerable magnitude in relation to the mean as is shown above. 



A negative coefficient of correlation of .3205 ±.0131 between time of be- 

 ginning to lay and pause duration stresses an important relation between 

 the two. Early laying, on the average, tends to increase the duration of the 

 pause. 



JO. Correlation Betxveen Time of Beginning to Lay Earlier Than the Mean 

 and the Presence of Winter Pause for Total Population. 



Coefficient of correlation 



-I-.3854 ± .0099 



