ELEDONE. 553 
where most of the characteristic dark brown retinal 
pigment is collected (fig. 86, P7g.); and (3) the basal 
region, which is external to the basal membrane, and 
is continued outwards into fine nerve fibres continuous 
with the nerve cells of the optic ganglion. The nucleus 
also is found in this region (fig. 85, Opi. V. f.; Ret. N.). 
There are two long slender cuticular rods in each 
retinal cell. ‘These are crescentic in cross section, and 
enclose between them the cytoplasm of the cell. By 
making a cross section of the retina, 1.e., at right angles 
to the length of the cells, it will be seen that the rods 
are arranged in groups of four, all four belonging to 
adjacent but separate cells. Hence the two rods of any 
cell belong to adjacent groups of four rhabdomes. 
The limiting cells he between the visual or retinal 
cells. They are broadest at the base, and the roundish 
nucleus is situated here. Also in this region there is an 
accumulation of pigment granules, corresponding to that 
meeaensrermal cell (Pl. X, fig. 86, Lum.N.).. The 
limiting cells are shorter than the visual cells, and end 
just internal to the basal membrane (fig. 86, B,J/,). 
This is a membrane of connective tissue, external to the 
hmiting cells therefore, but pierced by the retinal cells. 
The region below this membrane and between the basal 
part of the visual cells is occupied by connective tissue 
and blood vessels (fig. 86, C.7.). In the region where 
the rods are found the limiting cells extend forward only 
as very fine protoplasmic processes (fig. 86, Lim, C,), 
which are continued as far as, and secrete, the membrane 
limitans, which covers the internal surface of the retina 
(ie, 36, 1. L.). ; 
Hesse has observed in /. moschata a fine, somewhat 
sinuous fibre which runs centrally down each retinal cell, 
from the basal region, and ends in a minute knob at the 
