The Chemistry of Light-Production in Luminous Organisms. 181 



Unlike the photophelein from the luminous parts of Cypridina or 

 from non-luminous cypridinas, that of Lepas extract or of Dolabella 

 blood is perfectly stable and will give light with photogenin even after 

 standing for a period of 24 hours. 



Many extracts were found to give no light with concentrated photo- 

 genin. These included those shown in table 3, which were tried both 

 boiled and unboiled. Again it is possible that with greater concen- 

 trations even these extracts would call forth a faint light. 



The following fluids and dissolved protein substances also give no 

 light when their solutions are mixed with photogenin: 50 per cent 

 egg albumen; 50 per cent egg yolk ; Na nucleate ; Na nucleoproteinate ; 

 Witte's peptone; neutral meat peptone; dried ox-blood extract. 



TABLE 3. 



It is certain, then, that there is photophelein or something similar 

 to it in the blood or extracts of many invertebrates, but not necessarily 

 in solutions of protein substances such as egg albumen, peptone, etc. 

 In saliva there is something giving a very faint light and something in 

 urine giving a fairly bright light with photogenin. Certain fluids tried 

 were sufficiently acid to prevent the appearance of light and some 

 fortuitous characteristic, such as acidity, may explain why extracts of 

 some invertebrates give no light with photogenin. 



It is hardly worth inquiring into the nature of the substances in each 

 particular extract which may for convenience be collectively spoken 

 of as photophelein, since I have found a great many simple bodies 

 which, mixed with concentrated photogenin in powder or crystal form, 

 give rise to a bright light. With more dilute solutions (one Cypridina 

 to 10 c.c.) no light appears. These substances include sodium glyco- 

 cholate, sodium taurocholate, thymol, chloroform, hydrochinon, NaCl, 

 butyl alcohol, saponin, oleic acid, ether, benzol, atropin, pilocarpin, 

 and ortol. Chloral hydrate, pyrocatechin, FeS0 4 , MgS0 4 , (NH 4 ) 2 S0 4 , 

 esculin, dextrine, and K 4 Fe(CN) 6 gave a fainter light, while saccharose 

 gave none. 



It is difficult to see in just what way all these diverse substances act. 

 One is inclined to compare the production of light by chloroform or 

 saponin to a process of cytolysis or to a stimulus reaction like artificial 

 parthenogenesis. The photophelein of Cypridina or other extracts 

 would then be comparable to the cytolytic substance in the blood of 



