766 



YVETTE KUNZ 



appear clearly stained also, whereas in the dark adapted eye they are not visible. 

 This may be because the rods are superimposed. The inner segments of the rods 

 show very faint LDH activity in the dark adapted eye; 

 they cannot be recognized in the light adapted eye since| 

 they are covered by pigment. The outer segments of the 

 rods in both dark and light adapted eye show a weak pink 

 staining reaction in the inner half and blue granules in the 

 outer half (figs. 9 and 10). The cytoplasm in the outer 

 nuclear layer and the outer plexiform layer, stains uni-| 

 formly but moderately (figs. 9 and 10). 



The effectiveness of nitroblue tetrazolium in loca- 

 lizing LDH at the subcellular level in the light adapted 

 eye has been checked by varying the température, the pH 

 and the constituents of the incubating médium and by 

 pretreating the sections with acétone. The pink preci- 

 pitate in the outer segments of the rods proves to 

 be " nothing dehydrogenase and enzymic in nature, 

 whereas the blue droplets seem to be due to the accumu- 

 lation of formazan deposits by lipid granules (fig. 12). 

 The outer and inner segments of ail three types of cônes 

 stain under ail conditions, except when incubated at 

 4°C (normal temp. 37 : C), and when lactate is omitted. 



Fig. 6. 



Diagram of generalized 



photoreceptor 

 el = ellipsoid, m = mito- 

 chondria, my = myoid, 

 n = nucleus, lp = lipo- 

 protein lamellae (sacs). 



Fig. 7. 



Diagram of dark adapted retina of Lebistes (outer and inner segments (ellipsoids) only). 



Fig. 8. 



Diagram of light adapted retina (outer and inner segments (ellipsoids) only). 



Fig. 9. 



Kryostat section of dark adapted adult retina, stained for lactate dehydrogenase activity 



(viewed with oil immersion). 



Fig. 10. 



Kryostat section of light adapted adult retina, stained for lactate dehydrogenase activity. 



Détail of fig. 4. 



Fig. 11. 



Kryostat section of light adapted adult retina, stained for E-isozymes. 

 Détail of fig. 5. 



