SWA-FISILERIES LABORATORY. 437 
not the case, it passes directly to the base of each rod, 
where it terminates. Both Patten (35) and Rawitz (36) 
have followed this structure through the rod cells. Lawitz 
stated in addition that there was a fine canal running 
through the middle of the rod cell, in which lay the fibre. 
Schreiner (37), after making a careful series of pre- 
paratlions, came to the conclusion that there was no axial 
fibre in the rod cell, and that the appearance of one was 
due to the contours of adjacent cells, or an optical eftect 
formed owing to the rod cells being shehtly angular in 
transverse section and not perfectly cylindrical. Ilesse 
($2) acknowledges that it is often extremely difficult to 
find the fibre in the rod cells, even when it is perfectly 
obvious in the rods, but confirms Patten, and states that 
in Pecten aratus the fibre is easily followed in the rod cells. 
The eye of Pecten maatimus is not suited for this 
histological work, but transverse sections made through 
the retina (figs. 52 and 33), and cutting both rods and rod 
cells, show how distinctly the fibre is to be seen in the 
former whereas it is absent in the latter, and here both 
rods and rod cells have been subjected to exactly the same 
conditions of fixation and staining. In the Gold Chloride 
preparations, however, the fibre was seen in some rod 
cells to extend very slightly above the base, and not to 
end abruptly but rather to thin out. Apathy’s (27) and 
Bethe’s (28) work on the nervous system has thrown much 
hght on the structure, and if we regard the nerve cell as 
simply a cable, the conducting wires of which are the 
neural fibrillae and the perifibrillar substance the pro- 
tective and insulating material, we can apply this to the 
rod cells. The axial fibre in the rods is a nerve fibril 
lying in its nerve cell. It is so obvious because it is in 
all probability the product of the fusion or very close 
apposition of several primitive fibrillae. 
