208 HENRY LAURENS 



passively to the bottom of the dish, always so oriented that their 

 long axis was in the direction of the rays of light. 



SUMMARY 



1. Tadpoles of R. pipiens and of R. sylvatica show no re- 

 sponse to the stimulus of light. 



2. The larvae of Amblystoma punctatum are positively pho- 

 totactic, both when normal and when deprived of their eyes. 



3. The reactions of eyeless individuals are not brought about 

 by stimulation of the central nervous system, but of the nerve 

 terminals in the skin. 



4. Normal larvae placed in light become pale, bhnded larvae 

 dark. Normal larvae placed in darkness become dark, blinded 

 larvae pale, the conditions in the normal and blinded larvae thus 

 being opposite. 



5. The condition of the pigment in the skin chromatophores 

 does not affect the sensitiveness of the larvae to light; but previ- 

 ous exposure to light, or adaptation to darkness, does, in that 

 dark-adapted larvae are more sensitive to light than are those 

 which have been kept in the light. 



6. The youngest larvae to give responses to light of 768 candle- 

 meters intensity were between 11 and 12 mm. long. 



