AN ANALYSIS OF THE EFFECT OF SELECTION. 11 
to weight the results from different parents according to the number 
(and therefore reliability) of their offspring. In the present case, 
also, it gives an extremely large probable error, and probably gives a 
less accurate value for the coefficient itself. The usual method has 
accordingly been followed, but little reliance is to be placed on the 
biological significance of the results obtained. Hence in the follow- 
ing discussion the correlation coefficients will be largely ignored. 
7 
1 2 3 4 5 6 7 8 9 10 11 12 18 14 
Fic. 3.—Means and standard deviations for 864 inbred plus line. The gener- 
ation number is given on the abscissa; bristle number on the ordinate. 
The dotted lines represent reverse selection. 
The values for M and o in the 864 line are plotted in figure 3. 
Selection has apparently affected this line hardly at all. This is per- 
haps because in the early generations so few individuals were bred 
from. Reversed selection (dotted line in curve) was ineffective in 
the eleventh to thirteenth generations, thus indicating again that at 
that stage at least the line was not capable of modification through 
selection.! 
1002 Ling. 
The second inbred plus line is descended from culture 1002. The 
, 
female in this culture was of the constitution aha. and the four 
males were from the peach, spineless, kidney, sooty, rough stock. 
1The fact that the signs of the differences between the means are reversed when selection is 
reversed is due simply to the fact that the parents selected are now below the mean of the line, 
instead of above it. The difference between the means, like the correlation coefficient, is of 
slight significance when the number of parent individuals is as small as in these experiments, and 
for the same reasons. 
