54 The Produciion of Light by the 



Cypridina and fireflies, which again give fight on mixing with luci- 

 ferin. Neither Anomalops nor Photohlepharon gives the luciferin- 

 kicif erase reaction. If fresh water is added to a sea-water extract 

 of the organ of these fish, the fight grows rapidly dimmer and dis- 

 appears. There is no sudden increase in intensity, such as one gets 

 on adding fresh water to extracts of pennatufids and jefiy-fish. Afi 

 these pecufiarities are identical with those of an emulsion of luminous 

 bacteria, and again serve to strengthen the evidence that light is 

 due to symbiotic bacterial organisms. 



LUCIFERIN AIND LUC1FERA8E. 



In Cypridina, Odontosyllis, Pholas, and fireflies, the presence of 

 luciferin and luciferase can be demonstrated. In Noctiluca, penna- 

 tufids, jelly-fish, luminous bacteria, and Chcetnpterus it is not possible 

 to demonstrate them; it is also impossible in these fish. Luciferin, if 

 present in the organ, should be prepared by some one of the following 

 methods: (1) Adding boifing water to the excised luminous organs 

 and extracting them in a mortar; (2) heating the concentrated 

 luminous sea-water extract of the organ to (a) boiling or (6) to a 

 temperature (55° C.) which permanentlj'' extinguishes the light. 



Luciferase, if present in the organ, should be prepared by some 

 one of the following methods: (1) Extracting with sea-water and 

 allowing the extract to stand for 8 hours till the light disappears; 

 (2) extracting with fresh ^vater; (3) extracting with sea-water and 

 adding such substances as saponin or sodium glycocholate, which 

 causes the light to disappear quickly. Dark solutions which should 

 contain luciferin and luciferase have been obtained by these various 

 methods, but on mixing no light whatever has appeared. The luci- 

 ferin^ of these fish also gave no fight wdth Cypridina luciferase, nor 

 the luciferase^ of these fish with Cypridina luciferin. In the impos- 

 sibility of demonstrating a luciferin-luciferase reaction, despite an 

 apparent abundance and persistence of luminous material, Anomalops 

 and Photohlepharon again agree with luminous bacteria. The luci- 

 ferin-luciferase experiments may be summed up as follows : 



* Using these words for solutions which, according to the method of preparation, should 

 have contained luciferin and luciferase. 



