Fishes Photohlepharon and Anomalops. 



57 



of luminous extracts in general, as well as suspension of luminous 

 bacteria, it throws no light on the bacterial nature of the luminescence 

 of these fish. The effect of cytolytic agents, however, does indicate 

 a bacterial origin of the light. 



SODIUM FLUORIDE. 



Sodium fluoride is often used to determine if a process depends 

 on the integrity of the cell, on some vital peculiarity, or is of enzyme 

 nature. Sodium fluoride in 1 per cent concentration is said not to 

 affect the activity of enzymes. It is certainly true that 1 per cent 

 NaF does not affect the luminescence of Cypridium extract (Harvey) 

 or of Pliolas extract (Dubois). Sodium fluoride in 1 or 1.5 per cent 

 concentration does, however, extinguish rapidly the light of an 

 extract of Anomalops made with 3 per cent NaCl (to prevent pre- 

 cipitation of the NaF by the Mg and Ca of sea- water). 



POTASSIUM CYANIDE. 



Although potassium cyanide affects many kinds of oxidations, it has 

 very httle effect on the luminescence of extracts of luminous animals. 

 This is true for Cypridina, Cavernularia, fireflies, and Nodiluca. 

 Very small amounts will kill animals and even 0.00025 per cent KCN 

 is sufficient to cause asphyxiation and death of fresh-water fishes 

 in 24 hours. 



Table 1. — Effect of KCN on Luminous Bacteria. 



It was found that KCN extinguishes the hght of these fish more 

 readily than that of Cypridina or Cavernularia and about as readily 

 as that of luminous bacteria. A comparison can be made from two 

 tables which I append, although the times observed and concentra- 

 tions used are not exactly the same in the two cases. One gives the 

 effect on a strain of luminous bacteria which I studied in 1915, but 

 have not previously published the results. The second gives the 



