SIZE INHERITANCE IN DUCKS 



133 



TABLE 2 



Summary of measurements of 1912 ducks in centim>eters 



103, for the first three clutches of eggs, with Fi male 105 for the 

 last two clutches (see former paper). Female 83 died after the 

 first few eggs had been taken from the pen, so that nearly the 

 entire F2 lot was raised from only two mothers. Is is thus evident 

 that as regards the number of the parent individuals in each lot 

 there is fully as great a chance for variability among the F: ducks 

 as among the F2 ducks. Both generations ran together in the 

 rearing yard and in the maturing yard in exactly the same way as 

 in 1910-1911. The weights of the birds reared in 1912 are given 

 in tables 4 to 7. In table 1 are given the means and certain 

 other statistical constants for each lot of birds together with the 

 results obtained in the two previous years, thus summarizing 

 the entire experiment. 



The standard deviation in weight of the 1912 birds is greater 

 than that of the 1910 and 1911 birds. The mean weight of the 

 1912 birds is somewhat less than that of the 1910-1911 birds, 

 especially the F2 birds. 



It is plain that, in spite of the greater variabihty of the 1912 

 Fi birds, induced no doubt mostly by their greater number (57 

 animals instead of 13), there is still a small excess of variability 

 of the Fo over that of the Fi generation (at least among the males) . 



Finally, the combination of the three years' work gives a very 

 satisfactory basis for comparison, the Fi lot comprising 70 animals 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 16, NO. 1 



