110 



THE AMERICAN NATURALIST 



[Vol. LI 



^rpretation already 



Table 144 sho^ 

 obtained from ci 

 grandparent, ^9660, 



grandson, on t 



- 3|, was a grandson of ? 6 

 •ents. The hooded grandpai 



the other parent, of $ 6955, + 4, generat 



711, + ^, waa J 

 ration 10, and oi 

 (See table 141.] 



In two eases females could not be mated with brothers and so 

 mates were taken from other families. Thus "mixed matings " 

 were made between children of 5513 and 6600 and children of 5513 and 

 6955. (See table 141.) The former mating produced 3 hooded and 12 

 non-hooded "first" F^ young; the latter produced 2 hooded and 5 non- 

 hooded "first" Fj young. The grade of the hooded young produced 

 by these mixed matings was not different from that of brother-sister 

 matings, so far as the small numbers permit one to judge. One of 

 these mixed matings was carried into a second F, generation. The 

 first F, hooded ^ 9711, -f 314, was mated with a wild female, and the 

 young were bred, brother with sister, producing 16 hooded and 33 non- 

 hooded young. (See table 144.) The mean grade of the 16 hooded 

 young was 3.28, substantially the same as that of the first F, hooded 

 grandparent. No additional regression through loss of modifiers (or 

 other agency) is here in evidence. The result is the same as that ob- 

 served in families wholly unmixed. The attention of my pure-line 

 critics, who think that in our mass selection experiments insufficient 

 attention has been given to individual pedigrees, is particularly di- 

 rected to the foregoing case. 



Having now discussed each family history separately, we may com- 

 bine all the second F, families in one table, in order to get a clearer 

 impression of the results as a whole. (See table 145.) The second F, 

 generation thus combined includes 256 hooded and 749 non-hooded 

 individuals, a ratio of 1 : 2.9, an unmistakable mono-hybrid Mendelian 

 ratio. The mean grade of the hooded individuals is 3.34. The weighted 

 mean grade of their hooded grandparents was 3.02, which indicates a 

 reversed regression of 0.32 for the entire second F, group of hooded 



