472 Proceedings of the Royal Society of Edinburgh. [Sess. 
(4) A further result of the analysis made in this paper is that Dr 
Beddoe’s figures give no suggestion of the presence of any race in this 
country which had different hair and eye relationships from those pertain- 
ing to the three races generally considered to form the basis of the 
European population. This, of course, does not exclude the possibility of 
an older race surviving in sufficient numbers to form a considerable part of 
the British population ; but, so far as the survey is valid, this race must 
have had a hair and eye complex closely allied to one or other of the hair 
and eye complexes considered in this paper. 
APPENDIX. 
On the Categories of Eye Colour, with a Record of One Observation. 
Eye colour is the subject of much controversy. I am personally of the opinion that 
all categories that have been described are very imperfect. In the first place, apart 
from actual colour, the pigment of the posterior layer of the iris may be seen at 
times with more or less prominence along the inner and outer edges of the iris, often 
causing the eye to appear darker than the colour alone would permit. 
Again, mixed eyes are of two kinds — those in which the pigment is (1) diffuse and 
(2) discrete, that is, in spots ; hut as far as my observations go, I have never seen pig- 
ment in the eyes of children which was not present in the eyes of one or other of the 
parents. In mixed eyes the pigment tends to collect more markedly near the inner 
edge of the iris, so that in a mixed chocolate and grey eye we may have both the 
chocolate and the grey pigment in the inner part, and the outer edge simulating a 
blue eye. 
Of actual types of pure as distinct from mixed eyes I recognise four : — 
(1) The pure blue eye, in which there is no pigment in the iris, such grey 
as appears being due to strands of connective tissue. 
(2) The grey or pale yellow, in which there is always visible pigment present 
in little masses, quite distinct from definite strands of connective tissue. 
(3) The deep yellow eye, a more or less rare form, not much exceeding 1 per 
cent, of the adult population as seen in Glasgow. 
(4) The dark-brown or chocolate eye, of which the shades vary, but in all of 
which the iris is sensibly the same colour from the inner margin to the 
outer. 
All these types of eyes may be found mixed, and as regards eyes the population 
may be taken as given by 
m 2 (a, a) + n 2 (&, b) c) + q 2 (d, d) + 2 mn(a, b) + 2 mp(a, c) 
+ 2mq(a, d)2np(b, c) + 2 nq(b, d) + 2joq(c, d). 
