COLE. — IMAGE-FORMING POWERS OF VARIOUS TYPES OF EYES. 395 



lower intensities used by him (in the neighborhood of 1 CM.) "the 

 animals often did not react for from five to ten minutes or even longer." 

 It was only an exceptional specimen of Acris that did not react within 

 less than about a minute, and as the intensity of light employed was 

 not far from the lower intensities used by Parker, it is obvious that, 



TABLE IX. 



Reactions of Acris gryllus to Botfi Lights at Half the Custojiary 



Distance. 



as judged by the time required for response, Acris is much more 

 sensitive to this form of photic stimulation than the leopard frog. 



An inspection of Table VIII will .show that out of 200 trials 130 (65 per 

 cent) were toward the larger light, an excess of 3< ) per cent in that di- 

 rection over those in the opposite direction. The proportion of turn- 

 ings to the large light is undoubtedly considerably lowered by the 

 inclusion of several individuals which appeared to be indifferent or 



