464 
Proceedings of the Royal Society of Edinburgh. [Sess. 
Before quoting any examples of Dr Beddoe’s figures it will be well to 
state clearly his hair and eye categories. He recognises five types of hair 
colour. The meanings of these types seem to me as follows : — 
(1) Jet black.— This is a true single hue, and persons possessing this 
colour of hair are with few exceptions those who possess two distinct pure- 
black elements in the gametes. The exceptions, so far as I have seen, are 
a few persons who have one red and one jet-black element. In manhood 
this may resemble jet black very closely, but the colour of the hair on the 
body usually shows some trace of the ruddy pigment. These are, however, 
so few in number that they do not disturb the calculation. 
(2) Dark hair. — This is really a mixture consisting of one jet-black 
element and one element of either medium hair or fair hair. Black is 
thus imperfectly dominant. 
(3) Brown hair. — This consists of those who are true brown or medium 
and of those who possess one brown element and one fair element. 
(4) Fair hair. — This again is a pure pigment, the person possessing it 
having two fair elements. 
(5) Red hair. — In this group are included the pure reds, the mixtures 
of red and fair hair, and the mixtures of red and brown hair. 
For purposes of analysis it is necessary to combine the last three classes. 
Eyes are more difficult.* Dr Beddoe recognises three classes : — 
(1) Light eyes. — This includes, in my opinion, the pure blue, the grey 
or pale yellow, and the mixture of these. All are distinct varieties, and can 
be distinguished with fair accuracy after a certain amount of practice. 
(2) Mixed eyes. — This class contains a certain proportion of those eyes 
which are a mixture of the shades of eye just mentioned and of the 
chocolate and dark-yellow eyes. 
(3) Dark eyes. — This class contains all the pure-dark eyes and I think 
the pure-yellow eyes, as, on account of the manner in which the dark 
pigment of the back of the iris frequently shows both internally and 
externally, these may look dark except on careful inspection. It also 
contains many eyes which a moment’s careful inspection would show to be 
either mixed dark and grey or dark and blue eyes. The latter types of 
eye are much more common than the true dark or chocolate eye. That 
they have not been more definitely distinguished is somewhat surprising. 
It is obvious from what has been said that the last two classes must at 
least in the first instance be placed together. 
We thus have six equations to determine four unknown quantities. 
The success of this fitting must be the test of the truth of these statements. 
* See Appendix. 
