THE PHOTOKINETIC REACTIONS OF FROG 

 TADPOLES 



WILLIAM H. COLE AND CARLETON F. DEAN 



Department of Zoology, Pennsijlvania State College 



While one of us (Cole) was studying the problem of functional 

 regulation following grafts over the eyes of frog tadpoles (to be 

 reported later), it was noticed that the animals became more 

 active when being examined under strong illumination. The 

 increase of light intensity seemed to cause an increase in the 

 rate of swimming. A review of the literature, however, revealed 

 no evidence that the frog tadpole is sensitive to light. In fact 

 Franz ('10 and '13), and Laurens ('14) state that it is indifferent, 

 showing no reaction whatever. Since the adult frog is posi- 

 tively phototropic (Parker, '03), and since the young stages of 

 other Amphibians are either positive or negative to light, (Banta 

 and McAtee, '06, for Sperlerpes; Eycleshymer, '08, for Necturus; 

 and Lam'ens, '14, for Amblystoma), it is natural to .suppose that 

 the tadpole of the frog would be sensitive to light, at least dur- 

 ing some stages of its development. We therefore undertook 

 the experiments reported here to determine this question. 



The reactions of adult frogs and other Amphibians to light 

 have been studied by several investigators, and a review of the 

 literature is given by Pearse ('10). Suffice it to say here that 

 most Amphibians are either positively or negatively photo- 

 tropic, some of them, especially Cryptobranchus (Pearse, '10), 

 being also photokinetic. The larval stages have been studied 

 by Banta and McAtee ('06), who reported that Sperlerpes 

 larvae are much more sensitive to light than the adults; by 

 Eycleshymer ('08), who demonstrated a negative phototropism 

 for Necturus larvae; by Franz ('10 and '13), and Laurens ('14), 

 who stated that frog tadpoles are not sensitive at all. . In 1905 

 Parker reported the 'photodynamic' reactions of ammocoetes, 



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