F. T. HAXO AND BEATRICE M. SWEENEY 417 



flow for one minute, rose sharply to a maximum in less than 7 seconds 

 (less than a second when measured with a faster recording device) 

 and decreased to a low steady state. 



Cell suspensions taken directly from the lighted incubator lumi- 

 nesced only slightly on stimulation. When such cells were placed in 



f \\ 



O 2-6-S4 SERIES 

 X 2-IS-64 SERIES 



20 30 40 50 



DARK PERIOD IN HOURS 



Fig. 1. Variation in luminescence of Gonyaulax polyedra cell suspensions with 

 time in darkness, after gro\\th in white hght at 700 ft-c. Each measurement 

 represents the integrated light emission during mechanical stimulation of 

 one minute duration by different aliquots, not otherwise agitated until the 

 indicated time. 



darkness, the capacity for luminescence increased with time in dark- 

 ness and reached a peak after 6-8 hours, as shown in Fig. 1. With 

 the time in darkness further increased, luminescence decreased pro- 

 gressively, reaching a low value after 15-18 hours. This decline was 

 followed by a second increase in light emission, which reached a peak 

 after 28-30 hours in darkness. The second peak was lower than the 

 first and was followed bv a second decrease in luminescence. This 



