86 Mr. C. C. Hurst. [May 7, 
form of isolated patches situated around the margin of the pupil, or in rays 
running across the iris. 
“Tn the various shades of green eyes the yellow pigment is more uniformly 
diffused over the surface of the iris, and the green colour is due to the 
blending of the superficial yellow pigment with the blue and grey of the 
deeper structures. In the hazel and brown eyes the wvea and the fibrous 
tissues are hidden by increasing deposits of yellow and brown pigment on the 
anterior surface of the iris, and when this is very dense, black eyes are the 
result.” 
The above statement agrees well with my own observations, though I 
would add that the presence of the superficial layer of yellow pigment, when 
only slightly developed, is to be seen in blue eyes as well as in grey eyes. 
No albinos were met with in the material examined by me, and my 
observations, therefore, relate to pigmented eyes only. 
It has generally been supposed that the various types of eye-colours 
grade into each other without sensible breaks of continuity. <A critical 
examination, however, shows that there is a distinct discontinuity between :— 
(1) The eyes in which two kinds of pigments are present; the one, 
yellow-brown in colour, deposited on the outer or anterior surface of the 
iris; the other, blue-black in colour, deposited on the inner or posterior 
surface of the iris. Such eyes I propose to call duplex. 
(2) The eyes in which the posterior pigment alone is present in the iris, 
the anterior pigment being absent. Such eyes may be called simplex. The 
application of popular names to these types is uncertain and quite unreliable ; 
but, in general, eyes that would be called brown belong to the duplex 
type, while many of the blues and some of the greys belong to the simplex 
type. 
(1) Lhe Duplex Type. 
To the duplex type belong the various shades of eyes with both anterior 
and posterior pigments. 
In my observations, three distinct patterns of duplex eyes were found, viz. :— 
(a) The se/f-colowred duplex, in which the anterior pigment is distributed 
over the whole front of the iris, practically obscuring the posterior pigment 
as in ordinary brown eyes. 
(b) The ringed duplex, in which the anterior pigment is confined to a ringed 
area round the pupil, leaving the ground colour of posterior pigment clearly 
exposed round the periphery of the iris. | 
(c) The spotted duplex, in which the anterior pigment is broken up into 
distinct blotches or spots irregularly scattered over the posterior pigment 
which forms the ground colour. 
