70 CORA D. REEVES 



room. For experiments with dark-adaptation the aquarium 

 was not shifted. I have found fish more sensitive to Hght 

 after dark-adaptation although I have not worked with 

 such young fish as Hess used. It is certainly to be expected 

 that fish, whether dark-adapted or light-adapted, would 

 more readily respond to light after being quiet for 15 min- 

 utes as in the case with Hess' dark-adapted fish than after 

 the earthquake-like experience of being moved about a 

 room, as were his light-adapted fish. It therefore seems 

 to me that the relative lack of sensitiveness of Hess' light- 

 adapted fish may be due quite as much to inhibition of 

 response through mechanical disturbance as to light- 

 adaptation. Certainly dependable comparative results are 

 to be expected only when the light- and dark-adapted fish 

 are handled in the same way. 



Hess repeated some of the experiments of Zolotnitsky. 

 He fed light-adapted fish upon red Chironomus larvae. He 

 then offered them at the same time bits of red and gray 

 yarn that for his dark-adapted eye matched the larvae 

 in brightness, and he found that the fish snapped with equal 

 frequency at both the red and the gray yarn. When the 

 imitation larvae matched the background in brightness 

 but not in color, the same fish passed them without trying 

 to eat them, quite regardless of their color. Again areas 

 of red light of the size and shape of the red larvae were 

 projected against a green-lighted area and were snapped 

 at by the fish when they were darker or lighter than the 

 background, but not when they matched it in brightness 

 for his dark-adapted eye. These tests seemed to show that 

 fish are color blind. 



Bauer shows that after dark-adaptation fish go into a 

 red which they avoided when light-adapted when this 

 red is presented along with a blue. Hess shows that a 

 blue which matched a given red for dark-adapted fish must 

 be increased in brightness to match the red for the fish 

 after light-adaptation. It is probable that both men are 

 dealing with the same fact, namely that the stimulus 

 afforded by the blue is increased by dark adaptation. It 

 is not impossible that the real brightness of the red has 

 remained little changed with changed adaptation. But 



