PHOTOMECHANICAL RESPONSES 85 



Schiipbach (1906) found no differences in the inner nuclear 

 layer or in the ganglion cells between light and dark eyes of 

 pigeons. Birch-Hirschfeld (1906), however, was able to 

 demonstrate clearly that the ganglion cells showed a distinct 

 decrease in the number of Nissl bodies and an indistinctness 

 of their boundaries in the light eye. Carlson (1904) also 

 showed the same for Phalacrocorax penicillatus, and finally 

 Sgrosso (1905) found in the frog distinct differences in the 

 staining reactions of the inner nuclear layer between light 

 and dark eyes. 



The author investigated these matters in the eyes of the 

 turtle (Chrysemys), and whereas no effect of light could be 

 found on the form and volume of the ganglion cells, it did 

 reduce or disperse the amount of chromatin and Nissl sub- 

 stance, so that the cells stained less darkly and more diffusely 

 (Detwiler, 1916; Figures 8 and 9). 



