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together as a pavement epithelium ; the boundaries between 
them being pentagonal and hexagonal and very distinct (fig. 
14, c.w.). This part of each cell contains the nucleus (figs. 4 
and 14, n.p.e.c.) with a very distinct nucleolus (fig. 14, nucl.), 
and the surrounding cytoplasm is free from pigment, but 
exhibits a curious “ curdled ” appearance as if broken up into 
irregular blocks (figs. 14, bl.p.). The inner portions are 
made up of long and slender threads, each containing a great 
number of pigment granules. The latter often remain 
attached to the outer segments of the cones when the pigment 
layer has been torn away (fig. 5, p.g.). 
(9) The Supporting Structures of the Retina 
(figs. 4, 5, 6, 7, 8, 11, 12, 13). 
Muller’s fibres support the various layers of the retina and 
pass from the innermost or nerve-fibre layer to the bases of 
the cones. Inside the nerve-fibre layer they spread out into 
trumpet-shaped bases (fig. 12, m.f.b.) } which unite to form a 
definite layer over the inner surface of the retina. This is 
the membrana limitans interna (figs. 2, 4, 12, etc., m.l.i.). 
The fibres (fig. 12, etc., m.f.) pass up between the ganglion 
cells and through the inner and outer molecular and nuclear 
layers, and finally spread out again to form a membrane (fig. 
4, etc., m.Z.e.), comparable with the internal limiting mem- 
brane, which covers the outer surface of the outer nuclear 
layer, and through which the cones project. Small projec- 
tions (figs. 5, 6, p.m.f.) extend between the cones beyond the 
external limiting membrane, and these probably serve to 
support the bases of the cones. The nuclei of Muller’s fibres 
are situated in the inner nuclear layer (fig. 11, n.m.f.). They 
are large, oval in shape, and stain quite readily and darkly. 
Verhoeff (28) contends that the external limiting mem- 
brane is not formed from Muller’s fibres, but is a product of 
the embryonic cells which became converted into the rods and 
cones. His work was done on the human eye, and I am 
not in a position to state whether the same is the case in 
