A. R. Galloway 
269 
6. "The lighter shades of blue, and coarser greys" are not necessarily "due 
to the greater density of age " (Hurst, p. 88). In the B family mentioned in this 
paper, II. 2, aged 9 years, has as densely grey eyes as her mother. 
With regard to the first deduction from Hurst's observations concerning the 
two surfaces of the iris, it is necessary to mention that the two layers of importance 
developmentally and anatomically are (1) the stroma, consisting mostly of 
connective tissue, about ten times as thick as (2) the posterior retinal pigment 
epithelium. The latter is epiblastic, and the former mesoblastic in origin. 
For facility of description, the area of the iris may be divided into three zones : 
1. Pupillary zone — from the pupil to the lesser circle. 
2. Median zone — from the lesser circle to the beginning of the outer or 
folded part of the ciliary zone (where there is sometimes a greater circle). 
3. Peripheral zone, consisting of the outer or folded portion of the ciliary 
zone, and the periphery of the iris as far as visible. 
As the other deductions from Hurst's observations with regard to the two 
different kinds of pigments, and their Mendelian inheritance, could not be proved 
or disproved without examining microscopically an iris, showing both, I took 
occasion to do so in the case of G. C, aged 70, whose right eye I removed 
on March 30th, 1910, for sarcoma of the choroid in the lower and inner 
equatorial region. The tumour had not advanced far enough to affect the 
globe beyond the site of the growth, there being no pain or inflammation, and 
the sight being only partially obscured. The iris was normal and healthy, with 
free movement, and was coloured in exactly the same way as that of the left 
sound eye of the patient. The colour note of the eyes made on March 22nd, 
1910, was: 
" At a short distance distinctly blue ; narrow yellow-brown pupillary zones ; 
median and peripheral zones blue." 
"The right eye has nine dark brown spots of the apparent size of \ to 1^ mm. 
dotted over all three zones, one distinct dark one (up and in) and three more hazy 
ones occur on the yellow-brown pupillary ring. There is also an irregular 
peripheral ring, consisting of separate grey spots free of anterior pigment ; the 
median and peripheral zones generally show reticulations well except where the 
dark brown pigment spots occur. 
The left eye has seven similar dark brown pigment spots varying from £ to 
2 mm. in apparent size." 
The presence of a yellow-brown pigment ring, of dark brown pigment spots, 
and of blue median and peripheral zones, apparently mostly free from anterior 
pigment, promised valuable information. The eye, on removal, was taken to the 
Pathological Department of Aberdeen University, where Professor Dean prepared 
a large number of serial sections. The globe was divided into an upper and 
