PLATE 5 



EXPLANATION OF FIGURES 



All drawing;s in this plate are at a magnification of 930 diameters, a Leitz 

 -jV homogeneous immersion objective being used. 



30 Showing the positions of the rods and cones in a typical light-adapted 

 retina of Ameiurus. 



31 Showing the positions of the rods and cones in a typical dark-adapted 

 retina of Ameiurus. 



32 Showing the effect of low temperature (3°C. ) on the position of the dnrk- 

 adapted rod- and cone-cells of Ameiurus. 



33 Showing the efTect of high temperature (27°C.) on the i)osition of the dark- 

 adapted rod- and cone-cells of Ameiurus. 



34 From the retina of a Rana pipiens that had ])een previously kept at a 

 temperature of 3°C. in the dark. The cone myoids remain elongated as at an 

 intermediate temperature. 



35 From the retina of a Rana pipiens that had previously l)een kept at 18°C. 

 in the dark. The cone myoids are elongated. 



36 From the retina of a Rana pipiens that had been kept at 33°C. in the 

 dark, showing the resulting shortening of the cone myoids. 



200 



