816 LIGHT AND LIFE 



wich structure, made up presumably of lipid-protein layers. There are also 

 indications that processes extend from the edge of each layer or plate, and 

 make contact with the base of the rod. The rhodopsin may have an important 

 structural role. The whole pattern suggests that the lamina may themselves 

 have some essential or rudimentary properties of nerve fibers. Changing the 

 configuration of the rhodopsin may easily cause changes in charge or polari- 

 zation of the corresponding plate, which may be conducted laterally along 

 the plate and finally to the base of the rod. The sensitivity of the cell to 

 light presumably absorbed randomly among pigment molecules may be 

 accounted for possibly in this way. 



Dr. MacNichol: Well, there are several things here. One is, is this 

 clearly established? There are plenty of other pictures, also by competent 

 electron microscopists, who say that these are indi\'idual discs. There is 

 another point, and that is that one can follow both in the rods and in the 

 cones the structure of the original cilia. If you cut through in the rods you 

 see very nicely the typical 9 paired fibril structure with the two in the 

 middle. It looks just identical with the ciliary structures you find in the 

 sperm tail, for example. This can he detected along most of the length of the 

 rods and also in the cones. Villegas has some very nice electron micrographs 

 v/hich indicate that these things go right down through the center of the 

 cones. Certainly, it is not inconceivable that the propagation is down 

 through the internal fiber, which would presumably not give you a large 

 charge separation that you can detect with certainty. But this is speculative: 

 we have no evidence. 



