R'ETINAL PHOTOPIGMENTS 



137 



Figures 91 to 100 inclusive are photomicrographs of the frog visual ceils 

 and epithelial pigment layer under various experimental conditions as indi- 

 cated. X 515. All are reproduced from an article by Johnson and Detwiler, 

 1942, /. Exp. Zool., V. 89. 



Fig. 91 (Left). Frog, dark-adapted over night at room temperature. Retina 

 shows presence of numerous droplets and incomplete contraction of the epi- 

 thelial pigment. 



Fig. 92 (Right). Frog, dark-adapted over night at room temperature and 

 then for two additional hours at 0°C in the dark. Retina shows presence of 

 numerous droplets and almost complete contraction of the epithelial pigment. 



Fig. 93 (Left). Frog, light-adapted for one hour at room temperature, 

 followed by dark-adaptation at room temperature. Retina shows fully con- 

 tracted pigment and presence of numeroiis droplets. 



Fig. 94 (Right). Frog, light-adapted at room temperature. Retina shows 

 sparsity of droplets and marked migration of the epithelial pigment. 



with iron hematoxylin and erythrosin. Some sections from 

 each eye were depigmented with 10 per cent oxahc acid 

 and 1 per cent potassium permanganate. Eyes from animals 

 which were dark-adapted at room temperature, then cooled 



