RETURN SELECTION. 15 



The amount and persistency of the reversed regression in this series 

 show clearly that return selection is not easier or more rapid than the 

 original modification of the race by selection, but that selection in either 

 a plus or minus direction has cumulative and permanent effects. 



Further support for this conclusion is furnished by return selections 

 (one each) made from the seventh generation, from the eighth genera- 

 tion, and from the eleventh generation of the minus selection series. 

 (See Tables 37, 38, and 39.) Generation 7 (Table 22) was produced by 

 parents of average grade —2.01. Their offspring were of average 

 grade — 1.73, a regression (toward 0) amounting to 0.28. Certain pairs 

 of these offspring of grade —0.75 and —0.87 (mean —0.78) constitute 

 the return selection from generation 7 (Table 37). They had 33 off- 

 spring of average grade —1.15, a regression away from amounting to 

 0.37. 



Generation 8 of the minus-selection series (Table 23) was produced 

 by parents of mean grade —2.05. Their offspring were of mean grade 

 — 1.80, a regression (toward 0) of 0.25. Certain pairs of these offspring 

 of grades —0.50, —0.62, and —1.00 (mean —0.72), when chosen as 

 parents, produced 41 young of mean grade —1.51, a regression away 

 from amounting to 0.79. (See Table 38.) 



Generation 11 of the minus series (Table 2G) was produced by parents 

 of mean grade —2.30. The offspring were of mean grade —2.15, a 

 regression of 0.15 toward 0. A pair of the offspring of mean grade 

 — 1.62 (Table 39) produced 16 young of mean grade — 1.95, a regression 

 of 0.32 away from 0. This result shows that the selected race had now 

 passed the point represented by the grade of the parents ( — 1.62) and 

 the offspring regressed toward a racial mean as advanced as the most 

 extreme individuals obtained previous to selection. 



To show that, in the plus selection series, a return selection has a 

 result similar to that just described, two experiments may be cited: 



The sixth generation of the plus selection series was produced by 

 parents of mean grade 3.52, and their offspring were of mean grade 3.11, 

 a regression toward amounting to 0.41. Certain of these offspring 

 of mean grade 2.00, when chosen as parents, produced 17 young of 

 mean grade 2.36, a regression away from amounting to 0.36. (See 

 Table 40.) 



The eleventh generation of the plus selection series (Table 11) was 

 produced by parents of mean grade —3.97; their offspring were of mean 

 grade —3.78, a regression of 0.19 toward 0. Certain of these offspring, 

 ranging in grade from —2.62 to —3.25 (Table 41), mean —2.79, pro- 

 duced 53 young of mean grade —3.32, a regression away from amount- 

 ing to 0.53. The regression in this case, as in all those previously 

 described, was toward the racial mean of the previous generation, which, 

 however, it has in no case reached. 



