KiRSTiNE Smith 
21 
TABLE VII. 
Maternal Correlation. 
Year when 
sample 
taken 
Vert. 
Pd. 
Pigm. 
r,,±p.E. 
±P.E. 
1914 
1915 
1916 
1917 
1918 
1919 
0-3513+ -0343 
0-4375 + -0281 
0-4139 + -0355 
0-3775 + -0298 
0-4382 + -0298 
0-3674 ± -0378 
0-2409 + -0332 
0-3215 + -0.303 
0-2116 + -0387 
0-2824 + -0293 
0-2928 + -0298 
0-1851 ±-0387 
0-3762+ -0381 
0-3622 + -0373 
0-3722 + -0.332 
0-3710+ -0308 
0-3380 ± -0398 
From total 
samples 
0-4021 ±-0131 
0-2654 ±-0133 
0-,3654 + -0158 
It appears that these probable errors agree extremely well with those originally 
calculated* on the basis of the .5 or 6 values of the correlation coefficient obtained 
from 5 or 6 samples. 
Summary. 
In the first section we dealt with fraternal correlation and a formula was deduced 
for the standard deviation of the fraternal correlation coefficient for the case when 
the material of observation consists of equal numbeis of offspring from each family 
and when each available pair of siblings is introduced into the calculation. The 
formula is calculated on the supposition of normal distribution and normal fraternal 
correlation. 
It is shewn by means of the formula that forming fraternal correlation tables 
for fraternities of different numbers and giving each pair of observations the same 
weight we disturb very highly the distribution of weight which the observations 
must claim according to their nature. We find further from the formula that 
when the number of observed offspring from each family may be freely chosen 
the best determination of fraternal correlation from a given number of observations 
is obtained by taking (^1+ offspring individuals from each family (/• = frater. 
corr. coeft".). 
In the second section we deduce, also supposing normal distribution and 
normal correlation, the s.D. of the parental correlation coefficient calculated from a 
material comprising equal numbers of offspring from each family. The formula 
shews that forming parental correlation tables of a material consisting of families 
of different sizes we also in an unfortunate manner disturb the due distribution 
of weight among the pairs of observation. It is shewn that if observations of 
* Vide I.e., p. 24, Table 6. 
