1383 
data of the columns 31—40°/, and 41—50°/,, their number being 
too small. Lastly we annexed the percentages of the total increase 
of the number of mistakes in the five years. 
The data of tables IX and X confirm in every respect the results 
hitherto obtained. For boys and girls a constant increase is to be 
observed of the number of cases in which from 0 to 10°/, of the 
total number of possible mistakes was made; on the contrary a 
constant decrease of the number of cases with 11-—20°/, of the 
total number of possible mistakes. Here also the downward progress 
among the boys from 9—10 years and the girls from 10-11 years 
is remarkable. The increase and the decrease for boys is most 
marked from 10 —11 years; whereas the girls present the best 
results before the transition from 9—10 years, certainly with respect 
to the decrease but to some extent also as regards the increase. 
Let it finally be observed that, taking the five years together, the 
increase and the decrease are invariably greater among the boys 
than among the girls. This experience, of course, does not conflict 
with the fact shown in table II, that the number of mistakes for 
the boys from 8—12 years diminishes on an average with 45 °/,, 
for the girls, however with 57 °/,. 
In that table we recorded the absolute decrease of the mistakes; 
here, however, the decrease of a certain group — the cases of 
11—20 °/, of the total of the possible number of mistakes — to the 
benefit of another group, viz. that of cases of 1—10°/, of the total 
of the possible mistakes. 
CONCLUSIONS. 
1. The time, required for the work, decreases on an average 
with 30°/, from the 8 to the 12‘ year. 
2. The working times of the girls are invariably longer than 
those of the boys. As regards speed of working the boys are 
generally in advance of the girls by 2 years. 
3. The accuracy of working increases from the 8 to the 12th 
year for the boys with 46°/,, for the girls with 51°/,. Boys of 8, 
9 and 10 years generally make more mistakes than girls of the 
same age; after the eleventh year, however, the boys surpass 
the girls. 
4. By adding up to the mean number of mistakes, made by 
children of a certain age and a definite sex, the mean number of 
mistakes made in the minutes, by which the working time of the 
category of children under consideration surpassed the smallest 
