458 GENETICS IN RELATION TO AGRICULTURE 
against the productions of their mothers. The correlation of mothers and 
daughters with respect to winter egg production, as determined from this 
table, has the value, — 0.068 + 0.48. There is, therefore, no demonstra- 
bly significant correlation between mother and daughter with respect 
to winter egg production, and so likewise with spring and total egg pro- 
duction, the correlation coefficients do not differ sensibly from zero. 
Fortunately, however, for the efficacy of pure selection in breeding 
operations, correlation coefficients as low as this one are not usually 
reported. As an example of the more common condition, we give in 
Table LX the data of Rietz on correlation between mother and 
daughter with respect to milk production. The data are taken from the 
advanced registry records of the Holstein-Friesian cattle. They repre- 
sent, therefore, selected individuals, for both mothers and daughters have 
met the requirements for advanced registration. For that reason the 
values of the constants calculated from these data can only be regarded 
as approximately representing those which might be given in a population 
both of individuals which failed and those which succeeded in living up 
to advanced registry requirements. The value of the correlation coef- 
ficient in this case, 0.284 + 0.025, although low, indicates the existence 
of a significant degree of correlation. 
TasLe LX.—Corre.atTion oF Houstein-FReIsIAN Motruers AND DAUGHTERS 
witH Respect TO Propuction or Butrer Fat, r = 0.284 + 0.025. 
Recorps For 7 Days (Data of Rietz) 
Propuction or MoTHERS 
Produc- | | 
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WAS Ul se ll Gee hal 1 eee 1 
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