102 
PROFESSOR K. PEARSON AND DR. A. LEE ON 
Table V.—Collateral Heredity. 
Man. 
Dog. 
■ 
Horse. 
Coat-colour. 
Pair. 
Stature.* * * § 
Cephalic 
Index.! 
Eye-colour. 1 
Coat-colour.§ 
Whole 
Siblings. 
Half 
Siblings. 
Brother-Brother. 
•3913 
•3790 
•5169 
1 f 
•6232 
•3551 
Sister-Sister . 
•4436 
•4890 
•4463 
> ’5257 < 
•6928 
•4265 
Brother-Sister . 
•3754 
•3400 
•4615 
J L 
•5827 
•2834 
It will be noted that, with the single exception of eye-colour in man, sister and 
sister are more alike than brother and brother. 
The mean value of the fraternal correlation for stature is ‘4034, and for cephalic 
index ‘4027. These results are in excellent accordance with the '4 required by the 
Galtonian theory of blended inheritance. The mean values for eye-colour in man, 
coat-colour in dogs, and coat-colour in horses are : ‘4749, ‘5257, and ’6329. These 
are quite incompatible with that theory. I venture accordingly to suggest that we 
have here cases of an inheritance which does not blend, and that it is an inheritance 
which is far more closely described by the numbers we have obtained on the theory 
before developed of exclusive inheritance than by the law of ancestral heredity. 
Taking in conjunction with these results for collateral heredity, those for parental 
and grandparental inheritance, we see that coat-colour in horses diverges widely from 
the laws which have been found sufficient in the cases of stature and cephalic index 
in man. The latter characters are really based on a complex system of parts, while 
the determination of coat-cc-lour may depend on a simple or even single factor in the 
plasmic mechanism. Here Mr. Galton’s suggestion of an exclusive inheritance of 
separate parts (‘Natural Inheritance,’p. 139) may enable us to understand why 
stature and cephalic index differ so widely in their laws of inheritance from coat- and 
eye-colours. 
Part III.—On the Inheritance of Eye-Colour in Man. 
(10.) On the Extraction and Reduction of the Data .—The eye-colour data used in 
this memoir were most generously placed at my disposal by Mr. Francis GAlton. 
They are contained in a manuscript wherein, by a simple notation, we can see at a 
* Pearson, ‘Phil. Trans.,’ A, vol. 187, p. 253 et seq. See Note I. at the end of this paper, 
t Fawcett and Pearson, ‘ Roy. Soc. Proc.,’ vol. G2, p. 413 et seq. 
t Present memoir, p. 113 et seq. 
§ Pearson, ‘Roy. Soc. Proc.,’ vol. 66, p. 140 et seq . 
