No. 383.] BASIS FOR A THEORY OF COLOR VISION. 857 
coordinating and distributing centre. The structural unit of 
this apparatus appears to be a fibril, many hundreds of which 
may be present in each rod or ganglion cell. As the retinidial 
fibrils appear to form loops in the cones by uniting axial and 
external fibrils, and their central extremities terminate freely, it 
is possible that the retinal fibrils form elongated f-shaped loops, 
which might be compared to excessively small Hertz’s resona- 
tors, the spaces between the ends of the fibrils representing the 
spark gaps. But whatever comparison may be made between 
these fibrils and any electrical device, it is not to be assumed 
that they actually vibrate, like tense strings, in harmony with 
ether waves. But while they presumably act mainly as con- 
ductors and resonators, that fact would not exclude their 
undergoing metabolic changes, resulting in central or peripheral 
fatigue or temporary exhaustion. 
DARTMOUTH COLLEGE, 
HANOVER, N. H. 
