PEARSE. — THE REACTIONS OF AMPHIBIANS TO LIGHT. 163 



(Cole, :07), Bufo (Graber, '84). As these are representative genera, it 

 seems evident that photic stimulation exerts an influence of wide range 

 among the amphibians. 



Many amphibians show a marked tendency to orient the body and to 

 move toward or away from the source of light. Configliachi and Rus- 

 coni ('19) observed that Proteus tended to go to the side of an enclosure 

 farther from the light and remain there. Since then a number of ob- 

 servations have been made concerning the phototropism of amphibians. 

 Thus, the following have been claimed to be positively phototropic: 

 Rana sp. ? (Holmes, :06 ; Dickerson, :06), R. temporaria (Plateau, '89), 

 R. clamata (Torelle, :03 ; Yerkes, :03, :06 ; Cole, :07), R. pipiens 

 (Parker, :03» ; Torelle, :03), Acris gryllus (Cole, :07), Bufo clamita 

 (Plateau, '89) ; and the five following negatively phototropic: Proteus 

 anguinus (Configliachi and Rusconi, '19; Dubois, '90), Necturus (Cope, 

 '89 ; Reese, :06 ; B. G. Smith, .07), Spelerpes maculicaudus (Banta and 

 McAtee, :06), Rana (Loeb, '90). It will be seen from this list that the 

 photic reactions of the Caudata are negative, while those of the Sali- 

 entia are positive, with the exception of the observations by Loeb ('90), 

 which do not agree with those of other writers. 



Some amphibians show a tendency to come to rest in the shade. We 

 would perhaps expect such a reaction in species which are normally 

 negative in their phototropism, but Torelle (:03) has shown that the 

 frog, which is strongly positive, will also go toward a shaded area and 

 come to rest in it, though the animal then faces toward the light. 

 Graber ('83, '84) had previously found that Triturus, Rana, and Bufo 

 tended to come to rest in shadow. 



The eyes are not essential for the light reactions, that is, such reactions 

 may be brought about by stimulation through the skin. Configliachi and 

 Rusconi ('19) ascribed the photic reactions of Proteus to the pain- 

 ful effect of light upon the skin, but Kohl ('95) showed that, while the 

 eyes of this species are rudimentary, they might nevertheless be effec- 

 tive photoreceptors. It remained for Dubois ('90) to show that the 

 reactions of Proteus might take place through the skin alone. He 

 blackened the eyes and obtained a reaction from an individual in 

 which only the tip of the tail was illuminated. Graber ('83, '84) ob- 

 served reactions in Triturus, which were like those of normal indi- 

 viduals, after the eyes had been removed and the orbits filled with 

 black wax. More recently Parker (:03 b ) has shown that Rana is 

 positively phototropic with and without the eyes ; and Cole (:07), 

 besides corroborating Parker's observations, has obtained like results 

 from Acris. Koranyi ('93) observed reflex leg movements in a frog, 

 which had been rendered particularly sensitive by treating the brain 



