406 



Mr. F. Galton. 



[May 27, 



have taken a later limit than eight years, but could not spare the data 

 that would in that case have been lost to me. 



A great variety of terms are used by the various compilers of the 

 " Family Records " to express eye-colours. I began by classifying 

 them under the following eight heads : — 1, light blue; 2, blue, dark 

 blue ; 3, grey, blue-green ; 4, dark grey, hazel ; 5, light brown ; 

 6, brown ; 7, dark brown ; 8, black. Then I constructed Table I. 



The accompanying diagram will best convey the significance of the 

 figures in Table I. Considering that the headings for different eye- 

 colours are eight in number, the observations are far from being 

 sufficiently numerous to justify us in expecting clean results ; never- 

 theless the curves come out surprisingly well, and in accordance with 

 one another. There can be little doubt that the change, if any, during 

 four successive generations is very small, and much smaller than mere 

 memory is competent to take note of. I therefore disregard a current 

 popular belief in the existence of a gradual darkening of the popula- 

 tion, and shall treat the eye-colours of those classes of the English 

 race who have contributed the records, as statistically persistent 

 during the period under discussion. 



The concurrence of the four curves for the four several generations 

 affords some internal evidence of the trustworthiness of the data. For 

 supposing we had curves that exactly represented the true eye-colours 

 for the four generations, they would either be concurrent or they 

 would not. If concurrent, the errors in the R.F.F. curves must have 

 been so curiously distributed as to preserve the concurrence. If not, 

 the errors must have been so curiously distributed as to neutralise the 

 non- concurrence. Both of these suppositions are improbable, and we 

 must conclude that the curves really agree, and that the R.F.F. errors 

 are not large enough to spoil the agreement. The much closer con- 

 currence of the two curves, derived respectively from the whole of the 

 male and the whole of the female data, and the still more perfect 

 form of the curve derived from the aggregate of all the cases, are 

 additional evidences in favour of the goodness of the data on the whole. 



Fundamental JEye-colours. — It is agreed among most writers on the 

 subject (c/. A. de Candolle) that the one important division of eye- 

 colours is into the light and the dark. The medium tints are not 

 numerous, and they may have four distinct origins. They may be 

 hereditary with no notable variation, they may be varieties of light 

 parentage, they may be varieties of dark parentage, or they may be 

 blends. These medium tints are classed in my list under the heading 

 "4. Dark grey, hazel," and they form only 12*7 per cent, of all the 

 observed cases. It is common in them to find the outer portion of 

 the iris to be of a dark grey colour, and the inner of a hazel. The 

 proportion between the grey and the hazel varies in different cases, 

 and the eye- colour is then described as dark grey or as hazel, accord- 



