On the Chemistry of Light Production in Luminous Organisms. 97 
typical fat solvents, as ether, chloroform, benzol, etc., the luciferin is 
insoluble. Luciferin is also soluble in glacial acetic acid but not in 
anilin. 
There is nothing in the solubility relations of luciferase to indicate 
that it is not a protein. On the other hand, the solubilities of luciferin 
are certainly unusual for a natural protein. The best-known class of 
proteins soluble in alcohol are the prolamines of plants; but the prola- 
mines are insoluble in water and absolute alcohol. Zein, the prola- 
mine of corn, is soluble in 90 per cent ethyl alcohol, methyl and propyl 
alcohols, glycerine heated to 150° C., and glacial acetic acid.'. Recently 
Osborn and Wakeman? have described a protein from milk having 
solubilities similar to those of gliadin, the prolamine of wheat. Welker? 
has described a substance (obtained from Witte’s peptone, giving the 
biuret, Millon, and Hopkins-Cole tests) which is soluble in water and 
absolute alcohol, but not in ether, and it is quite possible that others of 
the peptones are soluble in absolute alcohol. On the other hand, some 
proteins in the absence of salts form colloidal solutions in strong alcohol 
from which they may be precipitated by an appropriate salt. As the 
absolute alcohol extract of Cypridinz was made from dry material con- 
taining the salts of sea-water, some salt was present, but there is 
always the possibility of sol formation. 
If we extract dried Cypridine which have previously been thoroughly 
extracted with benzine, with 800 c.c. boiling absolute alcohol for an 
hour, filter the alcohol extract through blotting-paper and hardened 
filter-paper, quickly evaporate the filtrate to dryness on the water- 
bath, and dissolve the residue in a small quantity of water saturated 
with CO., we obtain a yellow opalescent solution which gives a bright 
light with luciferase. This solution contains some protein or protein 
derivatives, as it gives a very faint Millon reaction, a good positive 
ninhydrin test, reddish blue in color, but no biuret reaction. It pre- 
cipitates with tannic and phosphotungstic acids, but not with picric, 
acetic, trichloracetic, or chromic acids or on saturation with (NH,)2SOu. 
The phosphotungstic precipitate is not due to the presence of calcium. 
The extract gives a faint Molish reaction for carbohydrates. As the 
evidence points to the presence of some protein material in the absolute- 
alcohol extract of Cypridine, it is possible that this protein is lucif- 
erin. It should be emphasized, however, that the Millon reaction was 
very faint, although the ninhydrin was quite marked. 
ALKALOIDAL REAGENTS. 
Phosphotungstic acid, tannic acid, and picric acid were selected from 
among the alkaloidal reagents to study precipitating power. 
1 Osborn, T. B., Ergeb. Physiol., 1910, x, 47. 
2 Osborn, T. B., and A. J. Wakeman, J. Biol. Chem., 1918, xxxiii, 243. 
3 Welker, W. H., Biochem. Bull., 1912, ii, 70. 
4 Private communication from T. B. Osborn. 
