106 



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 F. maximus. 



Hesse (32) states thai in some cases he could see 

 several hbrillae 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. -^o) 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 " Elementar fibrillen '' 

 which form the primitive fibrillae, and the darker 

 stained primitive fibrillae are due to the union of more 

 " Elementar fibrillen." 



I believe, therefore, that in the rod cells 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 nei^ve. 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. oO. 



Hyde (34) has published an account of the structure 

 of the Pecten eye which dift'ers considerably from all the 

 previous accounts. Unfortunately, no transverse sections 



