PHOTIC REACTIONS OF TADPOLES 277 



X. CONCLUSIONS 



1. There is an optimum intensity for the responses in Rana 

 clamitans tadpoles to light. 



2. At and below 0.3 candle-meter intensity, the light ceases 

 to have a physiological effect, regardless of the time of exposure. 



3. With effective light intensities below 20 candle-meters, 

 the changes in the receptors during illumination proceed accord- 

 ing to the Bunsen-Roscoe law. 



4. With intensities higher than 20 candle-meters, a deviation 

 occurs in the intensity-time products which seem to proceed 

 with a definite constancy. 



5. Nearly the whole of the reaction-time in Rana clamitans 

 represents a sensitization period. 



6. The eyes are not necessary for the responses of tadpoles 

 to light of the kind used in these experiments. 



7. Tadpoles subjected to continuous illumination of definite 

 duration become no longer sensitive to light. 



8. In the process of fatigue, the reaction-time at any moment 

 has a definite relation to previous illumination. 



9. Photosensory recovery after complete exhaustion occurs 

 in the dark in about fifty minutes. 



