PHOTIC REACTIONS OF TADPOLES 



263 



phenomenon that the actual sensitization period is extremely 

 brief, while the time occupied by secondary processes may vary 

 between one and four seconds, depending upon the duration of 

 illumination and temperature. Henri et Henri ('12), in study- 

 ing the excitability of Cyclops by ultraviolet light, find that 

 the animal responds in 0.2 to 0.1 second after cessation of illumi- 



J" 



o 



0.009 



8 



pooe 



CC. 



Sritensily - Candle meters 



Fig. 6 Curve A represents the relation of the reciprocals of the average 

 reaction-times plotted as function of intensity when eye and skin are illuminated 

 from above. Curve B shows the relation of the reciprocals of the reaction- 

 times plotted as function of intensity when blind tadpoles are illuminated from 

 the side. 



nation. Since only the duration of illumination represents the 

 actual time occupied for the necessary photochemical processes 

 in the peripheral organs, the deviation in the reciprocal curves in 

 figure 6 may be regarded as indicative of a secondary process in 

 the sense organs, nervous system, and muscles, which as yet has 

 not been analyzed in the study of the light reactions of tadpoles. 



