440 



LESLIE B. AREY 



TABLE 4 



Measurements from ten Uq hi -adapted retinas of Rana pipiens. The values are in 

 micrn and represent measurements taken along axes coinciding with radii of the 

 eyeball. Each value for the length of the green rod myoid is the mean obtained 

 from ten consecutively-placed elements 



The tables show that although the difference in the length 

 of the rod myoid, in darkness and in light, is small, the length 

 of the light-adapted element is quite consistently the greater 

 (figs. 1 and 2); hence it seems probable that this difference is 

 significant and the photomechanical responses of the red and 

 green rods are analogous. 



This conclusion is not in accord with the results of Angelucci 

 ('94). Angelucci believed that the red and green rod myoids 

 responded similarly to photic stimulation, yet in both cases a 

 shortening was said to take place. 



C. Influence of light on the diameter of the red rod 



From my preparations many rods were measured, yet no con- 

 stant or significant differences were found in the diameters of the 

 outer members (figs. 1 and 2, prs.dst.bac.rb.), or of the ellipsoids 

 (figs. 1 and 2, ell.bac.rb.) of the inner members, which could be 

 attributed to the influence of light and darkness. The myoid 

 of the inner member (figs. 1 and 2, my.bac.rb.) naturally becomes 

 tenuous when elongated by the action of light (p. 436). 



One is inclined to question the morphological normaUty of the 

 teased rods figured by Lederer ('08), especially since the appear- 



