REACTIONS OF AMPHIBIAN LARVAE TO LIGHT 203 



Babak ('10 and '13) has recently pointed out that normal and 

 eyeless Amblystoma larvae show differences in pigmentation ac- 

 cording to the illumination and background. The dark condi- 

 tion of the larvae, in which the pigment cells are expanded, can 

 be produced in three ways, namely, (1) by placing normal larvae in 

 diffuse light on a black background, (2) by placing normal larvae 

 in darkness, and (3) by placing blinded larvae in diffuse light. 

 The light, or pale condition of the larvae in which the pigments 

 cells are contracted, can be produced (1) by placing normal larvae 

 in diffuse light, on a white background, (2) by placing blinded 

 larvae in darkness. It occurred to me that perhaps the condition 

 of the pigment might affect the sensitiveness of the larvae to 

 light, in that in an individual in which the pigment was con- 

 tracted, the nerve terminations in the skin might be more easily 

 stimulated than in one in which the pigment was expanded. A 

 series of comparative tests were, therefore, carried out with the 

 object of finding out whether there was any difference in the sen- 

 sitiveness of dark and pale animals, and also whether adapting 

 the larvae to darkness or to light affected their photic reactions. 

 Two groups of normal and two groups of blinded larvae consist- 

 ing of ten each were selected, and were exposed in turn to the 

 several conditions of illumination and background mentioned 

 above. Battery jars entirely covered with white paper were used 

 to obtain a white background. Babak's results were verified. 

 Flemming ('97) obtained somewhat similar results with normal 

 salamander larvae. He found that if they are placed in dark- 

 ness the}^ become dark, and that if they are placed in bright light 

 in white porcelain dishes, they become pale and transparent. 

 Fischel ('96) obtained exactly opposite results with the larvae of 

 Salamandra maculata, which he found to become pale when kept 

 in darkness, and dark when kept in the light. Fischel's results 

 agree with those of Hermann ('86) on frog larvae, a condition 

 exactly opposite to what is found to take place in the adults. 



In my experiments the dark-adapted larvae were kept in the 

 dark five to seven days before they were tested. The larvae 

 which were light-adapted were allowed to remain three to five 

 days in bright diffuse daylight, and were tested only in the after- 



