TIMOTHY H. GOLDSMITH 



787 



2.0 - 



'> 



c 

 in 



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0.5 - 



300 



400 



700 



500 600 



wave length — rru/ 



Fig. .5. Tlie spectral sensitivity of the compound eye of the blow-fly, CaUiphnra. 

 Open circles and dotted curve, from .\utrum and Stimipf (2). Half-filled circles 

 and dashed cur\e, from Walther and Dodt (58). Filled circles and solid curve, 

 from \Valther and Dodt (59). The height of the 630 m^ peak increases (relative 

 to the maximum in the green) with increasing intensity. The height of the idtra- 

 violet maximum varies in different preparations, but it does not vary in a con- 

 sistent fashion as a function of intensity. 



was always a response — the oscillation could be varied in height but 

 could not be totally abolished by altering the relative intensities of 

 the test lights. The size of this "flicker potential" was a minimum 

 when the test lights were the same relative intensities as was required 

 to produce equal-size responses from the dark-adapted eye. The size of 

 the flicker potential was used by Antrum and Stumpf as a measure 

 of the ability of CalUphora to discriminate pairs of wavelengths. 



The salient results of these experiments are briefly as follows. Yel- 

 low light (ca. 580 m^i) was not distinguished from the light of an in- 



