The Chemistry of Light-Production in Luminous Organisms. 191 



If we try the reverse experiment, that of adding 1 c.c. of concen- 

 trated (1 Cypridina to 2 c.c.) photogenin to 1 c.c. of dilute (1 Cypridina 

 to 50 c.c.) photophelein, a bright light appears lasting 10 to 15 seconds 

 and no more light upon adding additional concentrated photogenin. 

 As might be expected, the small amount of photophelein is very rapidly 

 used up by the large amount of photogenin. 



The quantitative relations between concentration of photophelein 

 and photogenin, duration of light, and brightness of light will be con- 

 sidered in a subsequent paper. 



SUMMARY OF RESULTS FROM CYPRIDINA. 



1. The luminous secretion of Cypridina comes from several spindle- 

 shaped yellow gland-cells on the upper lip and is extruded to the sea- 

 water as a perfectly clear granule-free non-fluorescent secretion. The 

 light is homogeneous and bluish white in color. 



2. If the luminous secretion stands, the light disappears, and if we 

 now add an extract of cypridinas heated to boiling, the light again 

 returns i. e., Cypridina gives a luciferin-lucif erase reaction similar 

 to Pholas dactylus, as described by Dubois. 



3. Contrary to Dubois's theory, the luciferase is the source of the 

 light, and not an enzyme causing light-production by oxidation of 

 luciferin, because we can obtain light from luciferase by substances 

 incapable of oxidation (NaCl, chloroform, ether, etc.). The new names 

 of photogenin or light-producer for luciferase and photophelein or 

 light-assister for luciferin have therefore been proposed. 



4. Oxygen is necessary for light-production. 



5. Both photogenin and photophelein will pass a Pasteur-Chamber- 

 land or Berkefeld filter easily. 



6. Photophelein dialyzes readily through heavy parchment or collo- 

 dion, photogenin with great difficulty or not at all, even after a period 

 of 36 hours. 



7. Both photogenin and photophelein are adsorbed by boneblack 

 and Fe(OH) 3 . 



8. The light-producing substances may be dried and thoroughly 

 extracted with ether without impairing their light-giving power. 



9. Chemical tests on the natural light-secretion give negative results, 

 since a very small amount of light-substance gives a bright light and 

 at least 1 part of photogenin or photophelein in 1,700,000,000 parts 

 water will give a visible light. 



10. Photophelein occurs throughout the body of Cypridina, photo- 

 genin only in the luminous organ. Photophelein from non-luminous 

 parts disappears (apart from photogenin) on standing, but not so 

 readily if the extract has been boiled or in the absence of oxygen. In 

 the firefly and some non-luminous beetles the photophelein disappears 

 so quickly that it is best to make the extract with boiling water. In 



