RETINA OF LATERAL EYES OF SPHENODON PUNCTATUS. 311 
at the blind spot. It ramifies over the retina, gradually 
diminishes in size, and disappears as it gives off its branches. 
In sections cut through and parallel with the optic axis this 
main trunk is seen to be from two to four times the thickness 
of the nerve-fibre layer over the rest of the retina. The 
aggregation of the nerve-fibres in bundles is very distinct 
throughout the retina (fig. 12, n.f.b.). In all parts of the 
retina, so far as I could ascertain, the nerve-fibres are 
non-medullated. 
(2) Ganglionic Layer (numbered 2 in figs. 2, 4, 12). 
Though forming a definite and fairly regular layer, the 
actual ganglion cells are of various sizes and shapes, and 
some of their nuclei stain much more deeply than others. In 
a few cases only were the branches of the cells seen passing 
into the inner molecular layer, and the nerve-fibre passing 
out from the ganglion cell was also seen onlv occasionally. 
This was due again to the method of staining, which was 
adapted more to the cytological investigation of the visual 
cells, and was not suitable for the nerve-fibres. 
The distribution of the ganglion cells over the retina is 
easily determined by the position of the well-stained nuclei. 
They are scattered very irregularly round the entrance of 
the optic nerve in a single layer only. In all directions 
round this irregular part they are placed side by side 
together, but still in a single layer (figs. 4 and 12, n.g.c.). 
This becomes irregular again towards the ora serrata (fig. 13, 
n.g.c.), and then ceases altogether in the pars ciliaris (fig. 13, 
'p.c.r.). A special arrangement of the ganglion cells is found 
over the macula lutea where the layer becomes double (fig. 2, 
m.l. 2). In one or two sections there appear to be even 
four layers in this neighbourhood, but the latter appearance 
is, I think, due to the sections being somewhat oblique. 
Towards the centre of the yellow spot the double layer 
becomes single (fig. 2, 2), and in the central fovea itself 
(fig. 2, f.c.) the ganglion cells are very much scattered, only 
