RETINA OF LATERAL EYES OF SPHENODON PUNCTATE S. 313 
decreases again at the central fovea to about 30 ji , and here 
there is a proportionately larger number of multipolar nerve- 
cells. 
(5) Outer Molecular Layer (numbered 5 in figs. 2 and 4). 
This is similar in appearance to the inner molecular layer, 
being made up of a network of fibrils. In this case, however, 
the fibrils come from the visual cells, and interlace with pro- 
cesses from the bipolar and multipolar nerve-cells of the 
inner nuclear layer. The outer molecular layer, though very 
definite, is much less thick than the inner molecular (measur- 
ing about 15 fx), and unlike the latter does not vary appreciably 
in thickness over the whole retina up to the ora serrata, 
including the macula lutea and fovea centralis (fig. 2). 
(6) Outer Nuclear Layer (numbered 0 in figs. 2, 4). 
The cells here are much more definitely arranged than 
those of the inner nuclear layer. The whole thickness is from 
one half to one third that of the latter, and only two kinds of 
nuclei are present. The chief of these are those of the visual 
cells (figs. 4, nuc.) y which form a more or less regular single 
layer towards the outer limit. They are somewhat larger 
than any of the nuclei of the inner nuclear layer, distinctly 
oval in shape, and in most of my preparations have very 
distinct chromatin granules, and sometimes show a definite 
nucleolus. In many cases (fig. 7, c.n.) the cytoplasm is 
seen to be continued from the inner segment of the cone as a 
thin investment over the nucleus, and from this a distinct 
fibril (fig. 7, c.c.f.) passes through the thickness of the whole 
layer to ramify in the outer molecular layer (fig. 7, r.c.f.). The 
shape and position of these nuclei vary somewhat according to 
the size of the cones, those (fig. 8, nucJ 2 ) of the extremely 
small cones, with which we shall deal presently, being 
more pointed at their outer ends and further away from 
the membrana limitans externa than those of the ordinary 
single and double cones, which almost or quite touch the 
