THE PERCEPTION OF LIGHT 



615 



Figs. 761 to 764. — Photo-mechanical Movements (Katharine Tansley). 



^ ^ Vr ■ • ' •■ 



Fig. 761. 



Fig. 76: 



FiCJS. 761 AND 762. — Pigmentary migration in a fish (the bleak 



Alburnus lucidus). 



Fig. 761. — The changes in light adaptation. Tlie rods have moved 

 outwards and the cones inwards ; while the pigment has moved inwards to 

 shield the rods and envelop the outer limbs of the cones. 



Fig. 762. — The changes in dark adaptation. The cones have moved out- 

 wards and the rods inwards ; while the pigment has migrated outwards to 

 expose the rods. 





t^uw 



Fii 



7t3o. 



Fig. 764. 



Figs. 763 and 764. — Pigmentary migi'ation in the frog, Fana temjioraria. 



Fic;. 763. — The retina in light adaptation. The pigment has migrated 

 inwards to shield the rods. 



Fig. 764. — The retina in dark adaptation. The pigment has moved 

 outwards to expose the rods. 



