96 Papers from the Department of Marine Biology. 
in strengths of alcohol containing over 40 per cent water and in acetone 
containing over 30 per cent water. In weaker alcohol and acetone solu- 
tions it is more soluble. Indeed, the dry Cypridina powder will glow 
faintly in 70 per cent acetone and 50 per cent alcohol, but not in 90 per 
cent acetone or 70 per cent alcohol. In this case we have the two sub- 
stances, luciferin and luciferase, in intimate contact in a concentrated 
condition. If they are present in less concentration, as in a glowing 
mixture of the two in water, the addition of aleohol or acetone to about 
20 per cent is sufficient to extinguish the light. 
Boiling absolute alcohol will extract a considerable amount of lucif- 
erin, andsuch a solution is quite stable even if exposed to air, providing 
the alcohol is not allowed to evaporate away. In alcohol-water and 
acetone-water mixtures the luciferin oxidizes rather readily and disap- 
pears in the course of a day or so. J am inclined to think that alcohol 
may also have a destructive action on luciferin, because an absolute- 
alcohol extract of luciferin sealed in a glass tube in absence of air 
showed the presence of only a very small amount of luciferin when 
tested after a period of 90 days. A very small amount of a fine 
precipitate was present. 
SOLUBILITY IN ORGANIC SOLVENTS. 
The solubility of luciferin and luciferase in a number of pure organic 
solvents was tested by extracting the dried, powdered Cypridine, fil- 
tering, and then testing the filtrate by adding luciferase and luciferin, 
respectively. Small pieces of the photogenic gland will sometimes 
pass through ordinary filter-paper, but can always be recognized as iso- 
lated, brightly luminous dots appearing when the solvent is tested for 
photogenic material. A heavy blotting-paper holds back these fine 
particles and was used for filtering,except in the case of very viscous 
solvents. The results are summarized in table 2. 
It will be noticed that luciferase is not extracted by any of the sol- 
vents tried, whereas luciferin is soluble in a considerable number of 
them. Methyl alcohol, ethyl alcohol, propyl alcohol, benzyl alcohol, 
ethyl acetate, glycerine, and glycol all dissolve a considerable amount of 
luciferin. Solvents non-miscible with water, such as benzyl alcohol or 
ethyl acetate, give up their content of luciferin to the water phase and 
it then luminesces if luciferase is present. In the case of the homolo- 
gous series of aliphatic alcohols, the higher the alcohol in the series the 
less luciferin will it dissolve. The same is true for the homologous 
series of esters. 
Luciferin is fairly stable in methyl alcohol, ethyl alcohol, propyl 
alcohol, benzyl alcohol, and glycerine if no water is present, but rather 
quickly disappears in acetone, glycol, and ethyl acetate, presumably 
because oxidation occurs more rapidly in the latter solvents. In the 
