158 THE NATURE OF ANIMAL LIGHT 



factors, such as time of heating, salt content, acidity, etc., 

 so the luciferases of different animals coagulate at different 

 temperatures depending on these conditions. Some of the 

 more reliable observations on these critical temperatures 

 are collected in Table 14. 



We are thus led to the conclusion that intensity of 

 luminescence is dependent on the velocity of oxidation of 

 lucif erin and that with lowered reaction velocity the spec- 

 tral composition of the light changes. The maximum 

 emission shifts toward the yellow. I believe, however, 

 that in Cypridina also, the luminescence intensity depends 

 not only on reaction velocity but on the particular manner 

 in which luciferin is oxidized. Cyp^^idina luciferin will 

 luminesce only in presence of Cypridina luciferase and no 

 light can be obtained from Cypridina luciferin and a 

 host of different oxidizers (with or without HoOo) such 

 as are able to oxidize pyrogallol. Luciferin will also 

 oxidize in the air spontaneously but no light is pro- 

 duced. It is easy to show that this spontaneous oxi- 

 dation may be much more rapid than an oxidation with 

 luciferase and yet light appear only in presence of the 

 latter. If a concentrated solution of luciferin is kept 

 near the boiling point it will be completely oxidized to 

 oxylucif erin in four or five minutes. No light appears if 

 air or even if pure oxygen is bubbled through it. The 

 same solution kept at 20° with a small amount of luciferase 

 will luminesce continuously and not be completely oxidized 

 to oxylucif erin in a half hour. We can, however, cause the 

 luciferin to oxidize as rapidly at 20° by adding concen- 

 trated luciferase as does the luciferiji near the boiling 

 point without luciferase. A bright light is produced in the 

 former case, none in the latter case. The oxyluciferin 



