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. 



TABLE LX. CORRELATION OF HOLSTEIN-FREISIAN MOTHERS AND DAUGHTERS 



WITH RESPECT TO PRODUCTION OF BUTTER FAT, r = 0.284 0.025. 



RECORDS FOR 7 DAYS (Data of Rietz) 



PRODUCTION OF MOTHERS 



