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RAYMOND PEARL AND H. M. PARSHLEY. 



returns has been examined with the results shown in Tables III. 

 and IV. Table III. gives the actual frequency distribution, 

 and Table IV. the constants calculated therefrom. It should be 

 said that in these distributions the parents are weighted with 

 their fertility. That is, each individual appears once for each 

 offspring. This seems the fairest manner in which to deal with 

 the problem, for comparisons such as are here indicated. 



TABLE III. 



SHOWING THE AGE DISTRIBUTION OF THE ANIMALS IN THE SEVERAL GROUPS. 



From these distributions the constants of Table IV. have 

 been calculated by the ordinary biometric methods. 



TABLE IV. 



SHOWING THE VARIATION CONSTANTS FOR THE AGE OF BREEDING CATTLE. 



1 The differences between these and the offspring totals are due in the main 

 to failures in individual cases to record the age of an animal in the schedules. In 

 small part they are due to multiple gestation. 



