10 AN ANALYSIS OF THE EFFECT OF SELECTION. 
according to number of offspring, and is also recorded in the offspring 
generation. In the calculation of 7, the parental grades are taken as 
the average grades of the two parents. When r is not given, it is not 
capable of calculation, for the reason that all parental pairs in that 
generation were of the same average grade. The correlation coeffi- 
cients given here are of doubtful significance, though many of them 
are several times their probable errors. These probable errors, like 
TaBLe 8.—864, Inbred Plus Line. 
Generation. n M o r Diff. M. 
A 3 earn 113 | 5.672+0.048 | 0.762+0.034 | .............. —0.828 
Fis neeak e403 121 | 5.331+ .049 (80425 5.035: || eeceas saan ae —1.179 
Baeitacdiewase 73 | 5.822 .031 §896 Es 1022 | iia mie bautgee as — .178 
Mei ronan mates 260 | 4.904+ .036 -868 .026 | ..........08.. —1.016 
Eg aeiace eat 149 | 5.228 .043 LSE: | OBO accra reeninatrrics — .772 
Figs iseeciteine 120 | 5.450+ .044 eMQOSF: OBL | ses cgwiesa ei actin, « — .550 
ae shegiade ses 510 | 5.190 .025 (B00 018) | as neneees serene — .810 
Pes aeiexnt 461 | 5.475= .023 .738+ .016 | +0.105+0.031 | — .514 
Wigs cs csoud ss 154 | 5.643 .034 -621+ .024 | + .002+ .054 | — .458 
Fio... 2.00. 159 | 4.956 .051 960+ .0386 | ............0. —1.044 
Bins Bi a teraisees 232 | 5.224+ .039 .867+ .027 | — .011= .044 | — .901 
Fr... ee... 624 | 5.272 .025 987+ .018 | oo... 2. eee — .728 
Bag icing winch 353 | 5.787 .024 667+ .017 | — .070= .036 | — .762 
Pde osgsenn 175 | 6.080 .026 506+ .018 | + .133+ .050 | — .300 
3,504 
REVERSED SELECTION. 
Bigitaete- Geese ae 33 | 5.152+0.102 | 0.869+0.072 | .............. +0.652 
Bis. sasdaasis 49 | 5.3274 .092 956+ .065 | .............. +1.329 
Pigiwansa ss 62 | 5.7104 .052 G06 08% | vicies sanicce es vow +1.710 
144 
others of their kind, are intended only to give the magnitude of the 
error likely to arise from the fact that one is dealing with a sample of 
limited size—the error of random sampling. But in the present case 
the correlation coefficient is intended to measure the similarity be- 
tween the somatic appearance and the genetic possibilities of the 
parent individuals. It is known that this similarity does not amount 
to identity, and that it may be modified in individual cases bv en- 
vironmental causes. Since in any given case we are dealing with a 
rather small number of parent individuals, but a large number of off- 
spring individuals, the selection of one or two parents whose somatic 
appearance differs widely from their genetic possibility will throw 
the resulting correlation coefficient far off; but the large number of 
offspring will keep the probable error down. If, instead of entering 
each offspring individual in the correlation table separately, we enter 
only the mean grade of the offspring of each parent pair, we get what 
is perhaps a more reasonable probable error. But this method fails 
