462 
Miscellanea 
to call it 'i^erfect,' but I think the statement must be reconsidered in the light of the 
suggestion made in this note that possibly increasing racial purity marks decreasing correlation. 
The ' perfect ' correlation in the case of the white mice is really a sub-conscious transfer of the 
idea, based on experience of white and grey mice, of an interracial correlation coefficient equal 
to unity. It is one of the many points where caution is needful in passing from the old 
conception of correlation in the sense of Cuvier as an association of two attributes to the 
modern biometric notion as a relation between deviations. 
K. P. 
II. On the Correlation between Age and the Colour of 
Hair and Eyes in Man*. 
In recent work the resemblance of siblings in hair and eye colour has been used for measuring 
the intensity of collateral inheritance. In determining the correlation in pigmentation between 
siblings, allowance ought to be made for change of pigmentation with age supposing as in the 
case of man, we do not, as with greyhound puppies or thoroughbred yearlings, take the siblings 
at sensibly the same agest. It is usually stated that eye and especially hair colour are modified 
by age, but hitherto no quantitative measure of the change seems to have been published. It is 
the object of the present paper to determine measures of this kind. Prussian school children as 
given by Rudolf Virchow (" Gesammtbericht iiber die von der deutschen anthropologischen 
Gesellschaft veranlassten Erhebungen iiber die Farbe der Haut, der Haare und der Augen der 
Schulkiuder in Deutschland," Archiv fur Anthropologie, Bd. xvi. 1886, S. 468-9) provided the 
following data. See Tables I and II. In these tables the so-called "andere Combinationen " 
were omitted as no ages were given ; they are, however, very insignificant in total number. 
Using the method of mean square contingency, we have for children between 6 and 12 years 
of age : 
Correlation of Age and Hair pigmentation = -033. 
Correlation of Age and Eye pigmentation = '027. 
TABLE I. 
Age and Hair Colour, Prussian School Children. 
Hair Colour. 
Haare 
Blonde 
Biaune 
Schwarze 
Brandrothe 
Totals 
Age 6— 8 
409,830 
129,225 
5,172 
1,622 
545,849 
8—10 
1,565,036 
555,287 
25,736 
5,405 
2,151,464 
10—12 
488,938 
190,729 
8,866 
2,208 
690,741 
12—14 
131,883 
55,023 
2,443 
602 
189,951 
Totals 
2,595,687 
930,264 
42,217 
9,837 
3,578,005 
* I have put together the following results from Notes on this subject made by Dr Ginzo Uchida 
when working in my laboratory and placed by him at my disposal. K. P. 
t The allowance is easy to make, if the correlation between pigmentation and age is known. See 
Pearson : R. S. Proc. Vol. 71, pp. 289—294. 
