388 LESLIE B. AKEY 



PLATE 1 



EXPLANATION OF FIGURES 



eps.opt., optic capsule rtn.ex., peripheral zone of retina 



pig., pigment rtn.i., central zone of retina 



The figures of this plate, taken from axial sections of the Planorbis eye, are 

 photographs at a uniform magnification of 540 diameters and show the distribu- 

 tion of retinal pigment at various temperatures in light and in darkness. 



1 At 3°C. in the light. 



2 At room temperature (21°C. ±) in the light. 



3 At 30°C. in the light. 



4 At 30°C. in the dark. 



5 At room temperature (21°C. ±) in the dark. 



6 At 32°C. in the dark. 



