456 FRANCIS B. SUMNER 



most cases, a return to a more nearly normal state, and presup- 

 poses a previous (commonly recent) change from an original dark 

 condition. 



Condition in total darkness 



The fishes were examined at night, after three hours or more of 

 darkness, by means of an electric flash-light. This was done on 

 two different occasions, and with a considerable number of fishes 

 in various conditions. With one or two possible exceptions, these 

 fishes were of nearly or quite the same shade as when last observed 

 in the daytime. "^^ Even specimens which had but recently as- 

 sumed the pale condition were found to have retained this after 

 the withdrawal of the visual stimulus. Certain observers have 

 reported among fishes characteristic differences of color during 

 'sleep' or at least at night." I have found no evidence of such 

 in the case of Lophopsetta. 



Experiments were tried in which fishes of different shades were 

 shut up in a light-proof box. In the first of these, two specimens 

 which had become very pale and two of maximum darkness were 

 put into the box together. After five days the two dark ones were 

 found to be dead. The other two, though much darker than when 

 put in, still remained distinctly paler than those kept in neighbor- 

 ing black boxes. They assumed the darkest condition after a few 

 hours' exposure to light in such a box. 



In the next experiment, one pale and one dark fish were kept in 

 the light-proof box for a period of seven days. The pale specimen 

 had previously passed 6 days in an all-white box. When the fishes 

 were examined at the end of their stay in darkness, the dark speci- 

 men was found to be as dark as before; the other, though now 

 fairly dark, was distinctly paler than the former. It acquired the 

 darkest shade, however, after a few hours' exposure to light in a 

 black box. 



^^ In making such comparisons, I could only refer to my own notes describing 

 the condition of these fishes in the daytime, and to my recollection of this. Differ- 

 ences may have appeared which escaped me. 



*' E. g. Verrill (American Journal of Science, 1897, p. 136). Verrill's observa- 

 tions were made by dim gas-light, mainly between midnight and 2 a.m. 



