PLATE 2 



EXPLANATION OF FIGURES 



All drawings were made at a magnification of 1400 diameters, a Leitz j^ 

 homogeneous immersion objective being used; in the reproduction figures 8, 9, 

 and 12 are reduced to a magnification of 1150 diameters, and figures 10 and 11 

 to 950 diameters. 



8 Shows the positions assumed by the visual cells at 3° C. in the dark. 



9 Shows the position assumed by the visual cells of Ameiurus at 27" C. in the 

 dax'k. 



10 Shows the characteristic position of the visual cells of Ameiurus at room 

 temperature in the dark. 



11 Shows the characteristic position of the visual cells of Ameiurus at room 

 temperature in the light. 



12 From the retina of a dark-adapted Ameiurus the optic nerve of which 

 had been cut and the animal subjected to light. The rods remain shortened, as 

 in darkness, although in this case the cones have shortened to a great extent, 

 as is the characteristic response in light. 



244 



