Number 
Pigment layer from 
THE PIGMENT CELLS OF THE RETINA. 
Pigment layer from 
367 
of sides. eye of Sheep. eye of Ox. 
4 l6u X 13p 4p X 12p. 
4 lip X l5p lip X< 8°5p. 
5 194 X 16y ldp X 12p. 
6 284 xX 5p 17p X 16p. 
6 20m X 19°5p 
fi 20m X 165p : 32p X 17p. 
8 28'5u xX 19p : 32pm X 2p. 
8 B45 X 22p 
9 24u X 2p : 345m X 2p. 
9 32y X 2245p 
10 38m X 27p : 42u X 25. 
Among the mammals examined we noticed that the pigment 
cells from the rabbit’s eye were exceptionally large, the hexa- 
gonal cells measuring as much as the eight- to ten-sided cells 
from the retina of the ox and sheep. 
In our examination of the retinal epithelium our chief 
result has thus been that the term hexagonal as applied to it 
is not correct; polygonal would be better. Among minor 
points we have also observed that many of the larger cells— 
namely, those with eight, nine, and ten sides—have two nuclei. 
With regard to the shape of the pigment particles in the cells, 
most of them appear to be fusiform or rod-shaped, as described 
by Max Schultze. Many, however, are spherical or approxi- 
mately so, and certain others are spherical with a rod-like 
projection from one side of the sphere, as though the spherical 
granule were elongating to form a rod. 
Notg.—Since the above was written we have had an oppor- 
tunity of examining the retinal pigment cells from a human 
foetus (aged about seven months). ‘he cells there presented 
the same general characters as described above, but the pro- 
portion of non-hexagonal cells was smaller than in the eyes 
of the other mammals we have examined. 
We have also found, in Jabez Hogg’s book on the ‘ Micro- 
scope, a figure of the retinal pigment cells which indicates 
their polygonal rather than hexagonal shape, but in the 
descriptive letterpress no allusion is made to this fact. 
