138 



VERTEBRATE PHOTORECEPTORS 



Fig. 95 (Left). Frog, light-adapted at room temperature and then at 0°C 

 for one hour. Retina possesses few droplets and extensive pigment migration. 



Fig. 96 (Right). Frog, dark-adapted over night at room temperature, 

 followed by light-adaptation for one hour at room temperature. Retina shows 

 extensive pigment migration and very few droplets. 



Fig. 97 (Left). Frog, dark-adapted over night at room temperature, then 

 dark-adapted for one hour at 0°C. Retina shows partly contracted pig- 

 ment and the presence of abundant droplets. 



Fig. 98 (Right). Frog, dark-adapted over night at room temperature, 

 then dark-adapted for one hour at 0°C, and finally light-adapted for one hour 

 at 0°C. The histological picture is similar to that in experiment 4 (figure 97) 

 in showing partially migrated pigment and numerous droplets. 



to 0°C for one hour in the dark, with subsequent illumination 

 at 0°C, exhibited the conditions characteristic of dark-adap- 

 tation. The epithelial pigment was partially contracted and 

 the droplets were abundant (Table 4, Experiments 4A and 



