102 Papers from the Department of Marine Biology. 
be found in the hot-water extract of the whole animal. The acetic-acid 
precipitate does not form readily if the luciferin solution is hot when 
acetic acid is added. A little dilute NH,OH will dissolve the precipi- 
tate and it can be reprecipitated by acetic acid. The filtrate from the 
acetic-acid precipitation gives a voluminous precipitate with phospho- 
tungstic acid, which does not carry down all the luciferin unless a little 
HCl is also added, when luciferin is completely precipitated and may 
be demonstrated in the precipitate. 
Dilute HCl alone gives a precipitate with crude luciferin solution, but 
is almost completely dissolved in an excess of dilute HCl. 
Saturation of a solution of crude luciferin in presence of some NaCl 
with carbon dioxide does not cause precipitation nor an increase in 
turbidity. 
Dilute trichloracetic acid gives a stringy precipitate with crude lucif- 
erin solution similar to that with acetic acid, but abundant luciferin is 
found in the clear filtrate, which gives no further precipitate with 
trichloracetic acid. These results are recorded in table 3. 
Hence neither luciferin nor luciferase is precipitated from crude solu- 
tion by dilute NH,OH or NaOH or by dilute acetic acid, and neither 
of them can belong to the group of histones (precipitated by dilute 
NH,OH), or mucins or nucleoproteins, or such phosphoproteins as 
caseinogen, which are precipitated by dilute acetic acid. A mucin or 
nucleoprotein is precipitated from both crude luciferase and luciferin 
solution by dilute acid and carries down some luciferase and some 
luciferin in the adsorbed state. It is easy to demonstrate that such 
an adsorption might occur. A solution of sodium caseinogenate mixed 
with either luciferin or luciferase and precipitated with acetic acid will 
carry down a considerable amount but not all of the luciferin or lucif- 
erase. Luciferin is not, but luciferase is, injured by an excess of 
dilute acetic acid. 
Dubois! reports that Pholas luciferin is not precipitated by carbonic 
acid in neutral solutions or by acetic acid, except in presence of neutral 
salts, and that it forms an insoluble alkali albuminate with NH,OH. 
The latter is possibly a Mg(OH),. formed from the magnesium in the 
luciferin solution. 
ADSORBENTS. 
Proteins are usually separated from their solutions by one or another 
of the following methods: (1) Heat coagulation (in trace of acid). (2) 
Precipitation by alcohol or acetone (in large excess). (8) Precipita- 
tion by heavy metal salts (basic lead acetate, HgCl, and acid, uranium 
acetate and acid, etc.). (4) Alkaloidal reagents (phosphotungstic, 
tannic, picric acids, etc.). (5) Salting out (by MgSO, and acid, 
1 Dubois, Ann. Soc. Linn. de Lyons, 1914, 1]xi, 161. 
