FERTILITY AND HATCHING OF EGGS. I43 



m = correlation between mothers and (laughters in the 

 absence of (or preceding) any selection of mothers. 



We have the following observed values for these quantities. 



Fertility of Eggs. Hatching Quality of Eggs. 



R12 = .035 i?i: = O . 03 I 



5, = 20.61 s, = 17.00 



o-^= 15.00 0-, = 17.99 



It is at once apparent that in the case of fertility of eggs there 

 was no effective selection of the mothers. The variability of 

 the mothers is actually greater than that of general population 

 from which they were drawn. In the case of the hatching 

 quality of eggs the selection was far from stringent, as meas- 

 ured by the variabilities. We get in this case 



r... = 0.034 

 This indicates that the small observed value of the parental 

 correlation is not to be accounted for, except in an insignificant 

 degree, by the selection of mothers. This is the result which 

 was to be expected since the selection was so slight. 



So far we have discussed the inheritance of the characters 

 fertility and hatching quality of eggs in the female line only, 

 i. e., from mother to daughter. It is a pertinent question to 

 ask whether these characters may not be transmitted through 

 the male line. It is quite conceivable that this might be the 

 case just as in dairy cattle milking qualities are transmitted 

 through the male line. Unfortunately it is a very difficult 

 matter to determine whether any character which only reaches 

 its objective expression in the female is transmitted through the 

 male line. The reason for this is obvious. It is not possible 

 to get any good measure of the innate germinal constitution 

 of a male individual with reference to any such female char- 

 acter. Thus a male bird may bear within its germ cells the 

 tendency to produce good hatching quality in the eggs of its 

 daughters and yet this fact cannot be distinguished except 

 through the performance of the daughters themselves. These 

 considerations make it necessary to adopt a somewhat different 

 method of study than that which is used in the investigation of 

 inheritance in the female line. 



The only practical measurement which can be obtained 

 regarding male birds and which is pertinent in the present con- 

 nection is the average fertility and hatching quality of the eggs 



