438 ‘TRANSACTIONS LIVERPOOL BLOLOGICAL SOCTETY. 
Now, it is very difficult to consider this ending 
abruptly at the base of the rod cell, especially if it be 
regarded as the conducting element, It is also certain 
that it is always seen only with great difficulty in the rod 
cells, and I could not demonstrate its appearance in the 
eyes of P. maaimus. 
Hesse (82) states that in some cases he could see 
several fibrillae in the rod cell, and in any case the neuro 
fibril was always thinner there. 
Furthermore, the appearance in transverse sections 
shows that the cell contents which seem equally 
distributed in the rod cells (fig. 55) are condensed, and 
with the prominent axial fibril run down the centre of the 
rods (fig. 32). Bethe (28), in his work on the nerve 
elements of Carcinus, states that after using Toluidin and 
Methylene blue methods the primitive fibrillae appear 
with different intensity, and says there is in places a more 
or less stronger apposition of the ‘ Klementar fibrillen ” 
which form the primitive fibrillae, and the darker 
stained primitive fibrillae are due to the union of more 
“ Hlementar fibrillen.” 
I believe, therefore, that in the rod ceils there are a 
number of very thin primitive fibrillae which at the 
periphery of the retina become connected with the neuro 
fibrillae of the optic nerve. ‘These are only with difficulty 
to be made out, but have been seen on some occasions, and 
also by Hesse and Schneider (44). At the base of the rod 
cell there is, however, a fusion or an apposition of these 
neuro fibrillae, and the resultant obvious axial fibre of the 
rods is produced. I have reproduced this somewhat 
diagrammatically in fig. 50. 
Hyde (34) has published an account of the structure 
of the Pecten eye which differs considerably from all the 
previous accounts. Unfortunately, no transverse sections 
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