Specific Gravity and Luminescence in Noctiluca, etc. 



243 



that the constant glow is more faint and of shorter duration; n/125 to 

 n/250 NaOH and n/250 to n/1000 NH4OH (the first two solutions 

 were made up in Mg-free sea-water, all the others in artificial sea- 

 water) cause a constant glow lasting from 30 seconds to 4 minutes, and 

 no normal response is given (table 4). In slightly weaker solutions, 

 n/500 NaOH and n/2000 NH4OH, a normal response is given for a 

 short period, owing doubtless to a delay in penetration, followed by a 

 constant glow. 



In one series of experiments comparison was made of the penetration 

 time of the alkaU and its effect on luminescence. The comparison 

 was made on the same lot of animals stained with neutral red, which is 

 not harmful to them. One set was observed in the dark for the effect 

 on luminescence, while the other set was watched simultaneously by an 

 assistant for color-change. In the case of NaOH the color-change from 

 red to yellow takes place only after all light-response has stopped, 

 whether this be a steady glow or a nonnal response; NaOH, therefore, 

 does not penetrate the cell until after luminescence has ceased. On the 

 other hand, with NH4OH the color-change takes place before the effect 

 on luminescence has stopped— that is, the alkali penetrates the cell 

 while it is still giving a luminous response. For example, in n/500 

 NH4OH the color-change takes place in .30 seconds, while the constant 

 glow lasts 75 seconds. These results tally with those of E. N. Harvey 

 (1914), who found that in certain plant and animal cells NaOH pene- 

 trates the cell only after its death, while NH4OH penetrates before the 

 death of the cell. The effect of alkalies on hght-production is therefore 

 brought in hne with its effect on muscle-contraction, protoplasmic 

 rotation, and other physiological processes. 



POTASSIUM CYANIDE. 



In strong KCN solutions, m/10 to m/250, a normal response is 

 given at first, lasting from less than a minute to 30 minutes, and this 

 is followed by a constant glow lasting for 7 minutes in m/10 and for 

 35 minutes in m/250 KCN (table 5). The normal response at the 

 start is probably due to the delay in the KCN taking effect. In a 

 concentration of m/500 the normal response lasts for several hours, 



Table .5. — Effect of potassium cyanide. 



Solution in sea-water. 



m/lO (precipitate forms) 



m/60 



m/125 



m/250 



m/500 to m/2000 



m/4000 tom/16000 



Luminous response.' 



Normal response i minute, then constant glow 7 minutes. 

 Normal response 4* minutes, then constant glow 15 minutes. 

 Normal response 10 minutes, then constant glow .35 minutes 

 Normal response .SO minutes, then constant glow .35 minutes 

 Normal response > 1 1 hours, < 12 hours. 

 Normal response >6 days (experiment discontinued). 



'The normal response at the start is doubtless due to the delay in taking effect. 



