Is there a Cumulative Effect of Selection? 205 
2 
Fe 
Results of continued selection for high egg production. 
The essential data giving the results of the selection carried out in 
this experiment are shown in Table I. This table gives for each year 
of the experiment the following data: (a) the actual mean or average 
egg production, (b) the modified average production, (c) the variability 
in regard to egg production as measured by the coefficient of variation, 
and (d) the number of birds included. 
y = 39.86 (I ) 8.8636. 
Table I. 
Results of Selection Experiment |. 
Modified 
Laying Observed: se Mean Egg Een of AEE of birds 
Year Egg Production Production Variation furnishing data 
1899— 19009 136.36 + 3.55 136.36 32.29 + 2.02 70 
1900— 1901 143.44 + 3.29 143.44 31.38 # 1.78 85 
1901—190:2 155.58 + 3.79 155.58 25.03 + 1.83 48 
1902—1903 136.48 + 2.19 159.15 28.82 + 1.22 147 
1903—1904 117.87 + 1.75 129.14 35.14 + 1.17 254 
1904— 19051) 134.60 + 1.98 134.07 36.77 £1.17 283 
1905— 19061) 140.31 4 1.81 154.09 25.48 + 0.97 178 
1906—1907 1) 114.16 + 1.74 142.77 30.91 +1.18 187 
The data of Table I are shown graphically in figs. 2 and 3. 
Figure 2 shows the change in the observed and modified averages, 
and the best fitting straight lines to these data, as determined by 
the method of least squares, Figure 3 shows the change in the 
variability of the flocks (coefficient of variation), the observational 
data again being smoothed by a straight line fitted by the method 
of least squares. 
Observed means y= 148.48 —3.10 X 
Modified ,„, y=144.13--0.043 x 
Variability y= 30.56-++-0.039 x. 
where x denotes the year. 
From the data of Table I and Figures 2 and 3 we note the 
following points: 
1) Data for birds kept in flocks of 50 birds each used in these years. The 
reasons for this procedure are given in the detailed report q. v. 
