1864. | The Royal Society. 301 
inner end of the body in both Rods and Cones, and may be regarded 
as an integral part of it; the number of “Outer Granules” con- 
sequently equals that of the Rods and Cones. These “Granules” are 
large circular cells, mostly containing a central nucleus in which they 
differ from the “Inner Granules.” A very delicate fibre runs inwards 
from the inner end of the Rod and Cone body, not from the Outer 
Granule enclosed in this, as some think. This Mr. Hulke has traced 
through the intermediate layers to the inner part of the Granular 
Layer in the neighbourhood of the Ganglion cells. The “Inner 
Granules” are round or polygonal cells, more numerous than the 
“Outer Granules.” The Ganglion cells are mostly multipolar; some 
of their processes join those of neighbouring cells, others join the 
bundles of optic nerve-fibres, and a third set bend outwards into the 
Granular Layer. In the Frog and Gecko Mr. Hulke has traced optic 
nerye-fibres passing outwards through Ganglionic into the Granular 
Layer. The author prefers the term Granular to that of Grey- 
nervous for the broad layer which lies between the Ganglionic Layer 
and that of the Inner Granules, as it correctly describes its appearance 
under a low power, and has no respect to the nature of the tissue, 
which he regards as connective and not nervous. A high power 
demonstrates a closely-woven web in part derived from the fibres travers- 
ing it in a radial direction discovered by Miller. The Inter-granular 
Layer he also regards as a looser web of coarser connective tissue. 
The orderly arrangement of the respective layers and of the cell- 
elements in each is maintained by a framework of connective tissue, 
which consist of a homogeneous membrane bounding the inner 
surface of the retina; of the system of fibres discovered by Miller, 
arising from the outer surface of this membrane and traversing all the 
layers in a radial direction to end upon the inner surface of a 
fenestrated homogeneous membrane, which receives the Rod and line- 
bodies ; and lastly, of a delicate web in connection with these fibres, 
which preserves the disposition of the cells when in the several layers. 
These radial fibres are not looked on by the author as the link between 
the Rods and Cones, the percipient, and the optic nerve-fibres, the 
conducting elements of the retina: the view held by Muller, Kolliker, 
and some others. The true link he considers to be the fibre passing 
inwards from the inner end of the Rod- and Cone-bedy, which also has 
a radial direction, but is to be distinguished from Mullers’ fibre. 
Another paper of mixed chemical, physiological and optical 
interest was communicated by Professor Stokes. It has been supposed 
that biliverdin, the green colouring matter of bile, and chlorophyll, the 
ereen colouring matter of plants, are identical. An optico-chemical 
analysis of these bodies, however, shows them to be perfectly distinct. 
Chlorophyll is a compound body—a mixture of four substances—two 
yellow and two green, all possessing distinctive optical properties. It is 
extremely difficult to separate these bodies by chemical means, but 
they may be obtained in approximate state of purity. |The phyllo- 
cyanine and phylloxanthine of Frémy, Professor Stokes shows to be 
what we may call products of decomposition. 
A very valuable account of some Experiments made to determine 
