86 



VISION 



430 



500 550 600 



STIMULUS WAVELENGTH (nm) 



650 



Figure 23 Comparison of light- and dark-adapted spectral sensi- 

 tivity in Negaprion brevirostris . These psychophysical results, con- 

 firmed electrophysiologically, show that the sensitivity of this 

 animal shifts upon light adaptation, providing evidence for duplex 

 visual function. (From Gruber 1969. Unpublished dissertation.) 



