The brain of Acipenser. 109 
layer of fibres decussating superficially dorsal to that sac. This I 
shall call the decussatio epiphysis. It is, as I shall show, distinct 
from the dorsal decussation and is in no way related to the com- 
missura  habenularis 
(or commissura supe- 
rior), sinze the latter 
is ventral to the epi- 
physis. The fibres 
from this decussation 
(Figs. J, K) may be 
traced downward and 
forward, within and in 
front of the optic 
bundles, and are lost 
in the region of the nu- 
cleus anterior. These 
fibres are in part 
neurites arising from Fe 
the epithelial cells of } 
the epiphysial sac. Other fibres of the epiphysial decussation end 
freely among these epithelial cells. I have been unable to de- 
termine the source of the latter fibres, owing to the extreme com- 
plication of the bundles through which they approach their place of 
ending. I have demonstrated the presence of free endings of nerve 
fibres among these cells in methylene blue preparations of Teleost 
brains as well as in GOLGI preparations of Acipenser brain. Many 
of the fibres in the epiphysial decussation give off several fine 
branches wich penetrate between the epithelial cells and end in 
contact with them. The cells seem to have no dendrites, or only 
very short processes, so that they must receive impulses chiefly or 
only from the fibres ending between them. I have made a careful 
examination to determine whether this epithelium can be compared 
with that of the saccus vasculosus (page 119), and conclude that 
the total absence of anything corresponding to the tufts of cilia on 
the saccus cells makes a comparison of the two impossible. The 
groups of cells here described must be regarded as a special nucleus, 
although perhaps rudimentary or degenerated, which may have had 
some connection with the pineal eye. 
Besides the fibres which arise from or end among the epithelial 
cells, there are other fibres in the epiphysial decussation which cross 
