566 
GENETICS: HARRIS, BLAKESLEE AND KIRKPATRICK 
relation is determined in each instance between the yield of an indi- 
vidual month and the yield of the entire year, whiclji is made up of the 
yields of all the individual months. If the source of the partial spurious- 
ness of these constants be removed by correlating between the records 
of the individual months and the total production of the remaining 
eleven months of the year, a better biological measure of the inter- 
dependence of egg laying activity in two periods is. obtained. These 
are the results represented by the position of the circles on the ordi- 
nates for the individual months in figure 1. There is, as shown by the 
shaded area, a material reduction from twelve to eleven months by 
excluding the month used as the first variable in determining the 
correlation. 
FIG. 1 
The correlation between the production of single months and the 
production of the remaining eleven months of the year has, however, 
in every instance a substantial value. The coefficients range from 
0.295 to 0.567 in the several months of 1913-1914 and from 0.240 to 
0.567 in 1914-1915. The average reduction from the corresponding 
coefficients for 12 month periods is 20.45% in each year. Thus one 
must conclude that the birds are permanently, at least during the 
period of the first egg laying year, differentiated in respect of capacity 
for egg production. 
The magnitude of the correlation coefficients measures on the uni- 
versally applicable scale of — 1 to +1 the closeness of interdependence 
of the egg production of the two periods. For purposes of prediction 
the correlation coefficients may be thrown into the form of linear 
