RETINAL PHOTOPIGMENTS 



131 



present in small quantities; and 5) the effect of pilocarpine 

 on the number of droplets — an effect similar to that reported 

 by Ayres and Kiihne (1878) upon the production of visual 

 purple. 



In the gecko (Detwiler, 1923c) which has rods only, the 

 droplets were found to be abundant on the rod outer seg- 

 ments in dark-adapted retinae and sparse on the external 

 limbs following light-adaptation (Figure 89) (v. also Fig- 

 ure 90). 



Fig. 89 (Left). Photomicrograph showing 'droplets' on and between the 

 rods of the dark-adapted retina of the gecko. X 900. 



Fig. 90 (Right). Photomicrograph showing 'droplets' on and between the 

 rods of the dark-adapted frog retina. X 630. 



It was noted also that in light-adapted eyes, where the 

 droplets were few^ in number, the rod outer segments were 

 abundantly filled with a dark staining granular material 

 which appeared to have a lamellar arrangement. In the 

 dark-adapted eyes, with abundant droplets, the rod outer 

 segments contained very little of this deeply staining material. 

 Since sections from both dark and light eyes were mounted 



