PLUS SELECTION SERIES. 



11 



ceding generations it is 0.141, for the three which precede those it is 

 0.185, while for the first four generations it is 0.253. In every case the 

 correlation is positive — that is, the higher-grade parents have higher- 

 grade offspring and vice versa. 



(4) The offspring as a group average lower in grade than their 

 parents — that is, their mean regresses on that of the selected parents, 

 but because of the higher mode about which variation occurs in each 

 generation certain of the offspring are of higher grade than their parents. 

 Thus an elevation of the grade of the parents in the next generation is 

 made possible. 



(5) With the selection of more extreme parents, the absolute regres- 

 sion of the offspring has not increased, but on the contrary has slightly 

 diminished — that is, the advance made by the parents is retained by 

 their offspring. 



In Table 15 have been brought together for comparison the means of 

 the several horizontal rows of Tables 1 to 13. By examining the vertical 

 columns of Table 15 the mean grade of the offspring of parents of a 

 particular grade in any generation may be compared at a glance with 

 that of parents of the same grade in any other generation. By running 

 the eye down the columns, it will be observed that the mean grade of 

 the offspring tends to increase upon repeated selection. Thus parents 

 of grade 3.75 appear first in generation 4, the grade of their offspring 

 being 2.75; the offspring of such parents in subsequent generations 

 grade in order, 3.07, 3.22, 3.35, 3.49, 3.50, 3.69, 3.75, and 3.83 (twelfth 

 generation not complete) . The difference between parents and offspring 

 in this series grows less and less and finally disappears altogether. If 

 the grade of 3.75 parents in this series is compared with the grade of all 

 offspring in the corresponding generations we have the following : 



Table A. 



In generation 4 the 3.75 parents represented the most advanced indi- 

 viduals of the series, a whole grade in advance of the general average 

 of the race. Their offspring showed a correspondingly large regression. 

 The general average of the race steadily advanced in later generations 

 until in generation 11 it equaled that of the 3.75 parents; then the 

 regression vanished. In the following generation, 12 (which is still 

 incomplete, but in which the average of the offspring thus far is 3.94), 

 the 3.75 group of parents, which are now helow the average of the race. 



