Raymond Peakl 
45 
here to the general uniformity of the correlations for the same characters in 
different series. All the brain-weight and stature correlations are seen to be 
positive, while with a single exception (Bavarian female " young " series) all the 
correlations of brain-weight with age are negative. The coefficients are generally 
lower for the "young" than for the "total" series, as is to be expected. In the 
case of the correlation of brain-weight with age, some of the coefficients for the 
"young" series are evidently insignificant in comparison with their probable errors. 
The correlations between stature and age arc negative with the exception of the 
Hessian male series. The positive sign in these series arises from the fact that in 
this material the age class 15 to 20 was included. All growth in stature has not 
stopped at age 20, and as a consequence there are included in the tables (21 and 
23) five individuals of unusually small stature and low age. These serve to change 
the sign of the coefficients. Their greater effect in the " young " series is apparent. 
The detailed discussion of the various brain-weight correlations and the regressions 
based on them I propose to take up in separate sections of the paper now to follow. 
8. Brain-weight and Sex. 
All brain-weight statistics show that the brain of the male is absolutely heavier 
than that of the female. In the series here discussed the absolute differences in 
mean brain-weight between males and females are as follows : 
Male mean — Female mean 
" Total" series 
"Young" series 
Swedes 
Bohemians 
Bavarians 
Hessians 
147-8 
143-9 
142-8 
131-9 
14.5-8 
146-2 
133-6 
125-6 
From this table the following points are to be noted : 
(a) Considering the size of the probable errors involved it is evident at 
once that the absolute difference is sensibly the same for all four races. Taking 
the extremes of the " total " column the difference between the Swede and Hessian 
sex differences is 15-9 with a probable error of + 7-9, or in other words the difference 
is almost exactly twice its probable error and cannot be considered certainly 
significant. The "young" series points to the same conclusion. So then, 
Weisbach's law for stature that the greatest sex differences occur in those races 
having the highest mean stature, does not appear to hold for brain-weight, so far 
as absolute differences are concerned. 
