On the Chemistry of Light Production in Luminous Organisms. 93 
in the filtrate. The (NH,).SO, precipitate dissolves completely in 
water and gives a brilliant light if mixed with luciferin. 
If a crude solution of luciferin is saturated with NaCl or half-satu- 
rated with MgSO, or half-saturated with (NH,)25Ou,, no precipitate 
forms. The luciferin remains in solution. With saturated MgSO, 
the luciferin is partially precipitated; with saturated (NH,4)2SO, it is 
almost completely precipitated, but a small amount of luciferin still 
remains in the filtrate. The addition of acetic acid to the point where 
precipitation of the crude luciferin solution is complete (probably a 
nucleoprotein or mucin is precipitated) and subsequent careful satura- 
tion with MgSO, or (NH,).SO, do not completely precipitate the 
luciferin. 
The above results can be confirmed by adding saturated solutions of 
NaCl or MgSO, or (NH,).SO, to dry, powdered Cypridine. The 
powder glows strongly in saturated NaCl, which dissolves both lucif- 
erin and luciferase; weakly in saturated MgSO,, which dissolves some 
luciferin but very little luciferase; and not atallin saturated (NH,)2SO,, 
which dissolves no luciferase. On filtering the saturated (NH4).SO,4 
extract of dry Cypridine and pouring this into water no light appears, 
but if luciferase is now added a faint light appears, showing that a 
small amount of luciferin has gone into solution. These results are 
summarized in table 2 (page 109). 
In order to determine if luciferin and luciferase are adsorbed on 
proteins or carbohydrates salted out of solution, the following experi- 
ments were performed: 
Egg white was thoroughly mixed with about 3 volumes of dilute 
NaCl solution, a fairly dilute luciferase added, and then an equal 
volume of saturated (NHj,).SO, solution. The precipitate of ‘‘ovo- 
globulin” (ovomucin) which formed was allowed to stand for 10 
minutes and then filtered off. The filtrate gave a good light with 
luciferin, whereas the mixture containing suspended precipitate gave 
a bright light. As luciferase is very slightly if at all precipitated from 
Cypridina extract with half-saturated (NH,).S8O., a certain amount 
must have been adsorbed on the ovomucin precipitate. 
A similar experiment with egg white containing luciferase salted 
out by saturation with NaCl indicated that some luciferase was ad- 
sorbed by the fine precipitate of ovomucin salted out with NaCl. 
A neutral solution of sodium caseinogenate is completely salted out 
by half-saturation with (NHj4).SO,. If luciferase is also present most 
of it but not all goes down with the caseinogen precipitate. The 
precipitate redissolves in water and the luciferase again becomes 
active. 
Gelatin solution (1 per cent) containing luciferase is also completely 
precipitated with (NH,).SO, and the gelatin precipitate carries down 
most of the luciferase. The gelatin precipitate containing adsorbed 
