SEA-FISHERIES LABORATORY. 441 
of one of the cilia-like fibres, which he illustrated as 
coming from the middle of the septal surfaces. 
Hesse, in 1900 (32), could not see any connection 
between the fibres of the optic nerve and the distal cells, 
but traced the nerve fibres between them to connections 
with the interstitial cells, which he regarded then as sense 
cells but not ganglion cells. In a later paper, however 
(1907), after a study of the very early stages, he shows 
that the optic nerve is already connected with distal cells 
before the interstitial cells are in existence. According 
1o him, the nerve fibrils of the outer optic nerve, after 
boring through the septum, pass between the distal cells 
and connect to the sides, and not the middle of the septal 
surface as stated by Schreier. The attachment of the 
outer optic nerve to the distal cells is practically certain, 
but there is still great doubt about the interstitial cells, 
and though I could trace their processes to the cilia-like 
border, there could be no certainty of connections in the 
confusing mass of fibres. 
The Interstitial Cells are irregular in shape and 
drawn out into fine branching processes. ‘The outer inter- 
stitial cells bear processes which pass between the distal 
cells to the retina surface. The inner interstitial cells are 
very much flattened, and lie in such close proximity, 
wrapping as it were round the rod cells, that their nuclei 
were first taken for the nuclei of these. The cells are 
rather small, very little larger than the prominent nucleus, 
and, in addition to processes extending amongst the rod 
cells, one from each cell penetrates the sieve membrane 
and hes between the rods. 
The nuclei of the interstitial cells stain very darkly 
with Haematein, and quite differently to the nuclei of the 
rod and distal cells. Hesse, Patten and Schreiner have 
regarded the interstitial cells as sense cells, Schneider, 
