130 Maine Agricultural Experiment Station. 1920. 



The comparison of the accuracy with which this control 

 mechanism works with that of similar secretions on other species 

 has a good deal of direct bearing on the subject. The only data 

 available are for the egg of the domestic fowl. 



Correlations obtained by Harris and Blakeslee for the suc- 

 cessive monthly egg productions of White Leghorn pullets with 

 their first annual production range from -l-0.372i.030 to 0.695 

 ±.018 with an average of 0.556. The correlations of the suc- 

 cessive yearly productions and the total of the first five lactations 

 shown in table 4 range from -l-0.7416zt.0323 to 0.861 3 ±.0186. 

 The difference between these correlations is striking. In the 

 proper calculation of this difference it must be remembered that 

 the correlations for egg production is for the twelve month peri- 

 od where the production for the individual month correlation 

 only contributes one-twelfth to the total annual egg production 

 while that for the milk production contributes about one-fifth to 

 the total production of the five lactations. The correlation would 

 therefore be expected slightly larger for the milk production. 

 This increased size of the milk correlations over the egg correla- 

 tions is very small relative to the whole difference as the con- 

 firmatory results of table 1 shows. The correlations for the 

 milk production of the successive lactations, therefore, represent 

 in concrete terms that a greater reliance may be placed in the 

 milk records of one lactation as measuring the cow's capacity 

 than can be placed in the monthly egg records as measuring the 

 lien's capacity for annual production. Such being the case, if- we 

 generalize this conclusion in its ultimate terms, the causative 

 mechanism behind milk production works with greater fineness 

 and precision than does the mechanism for egg production. Since 

 this mechanism seems in its broadest sense to be of hereditary 

 origin in the two cases, it follows that in the cow this hereditary 

 complex is less influenced in its action by environment than is 

 the action of the material stuffs of the fowl for egg production. 



Practical Aspect of the Correlations for Milk Production 

 of One Lactation Record With Another Lactation 



Record. 



The constants deduced in table 4 have a good deal of practi- 

 cal value to the dairyman and to the student of farm manage- 



