86 Papers from the Department of Marine Biology. 
color, but I do not believe that either luciferin or oxyluciferin are 
yellow in color, because an ether or benzine extract of Cypridina is 
also yellow, although luciferase, luciferin, and oxyluciferin are all 
insoluble in ether and benzine. The yellow pigment which can be 
observed to make up part of the luminous gland of Cypridina is not 
luciferin or luciferase. It may be a pigment related to urochrome. 
When tests are applied and precipitating reagents are added to crude 
luciferin and crude oxyluciferin solution they give identical results in 
each case. A complete account of the chemistry of luciferin will be 
found on pages 87 to 110, but a few of its more important properties 
are emphasized here.' If crude luciferin is saturated with (NH4).50O. 
or MgSO, a floceulent precipitate forms which may be demonstrated 
to contain most of the luciferin (see page 93). Oxyluciferin solution 
also gives flocculent precipitates on saturation with (NH,).SO,4 and 
MgSO, and these contain most of the oxyluciferin. To demonstrate 
this the precipitates, after washing, are dissolved in a small amount of 
water, mixed with fresh milk (or frog-muscle suspension) and allowed 
to stand in a stoppered tube for 24 hours. If any oxyluciferin is present 
it will be reduced to luciferin and give light when luciferase is added. 
One-half saturation with (NH,4).8O4 or MgSO, or saturation with 
NaCl salts out no material from either crude luciferin or oxyluciferin 
solution. Picric acid gives no precipitate, but only an opalescence in 
both cases. In a similar manner it may be shown that most of the 
oxyluciferin is precipitated by phosphotungstic acid but not by acetic 
acid or COs, in this respect also agreeing with the behavior of luciferin. 
Like luciferin, the oxyluciferin will pass porcelain filters, dialyze through 
parchment or collodion membranes, is soluble in absolute alcohol, but 
not in ether or benzine, and is undigested by salivary diastase, pepsin, 
HCl, Merck’s pancreatin in neutral solution, and erepsin. The salivary 
diastase and the pancreatin (containing amylopsin, trypsin, and lipase) 
were allowed to digest for 4 days at 38° C. without showing any evi- 
dence of digestive action. It is partially but not completely precipi- 
tated by basic lead acetate and by tannic acid. 
As luciferin is so easily oxidizable a substance, we should expect to 
find that it will reduce just as glucose will reduce. However, a concen- 
trated solution of luciferase has no reducing action on Fehling’s (alka- 
[ine Cu), Barfoed’s (acid Cu), Nylander’s (alkaline Bi), or Knapp’s 
(alkaline Hg) reagent. Glucose will reduce methylene blue in alka- 
line (not in neutral) solution, but luciferin will not reduce methylene 
blue in alkaline or neutral solution. It would seem, then, that luciferin 
must contain no aldehyde group. If so, we should expect to obtain 
reduction of some of the above reagents. Just what group is concerned 
in the oxidation is unknown at the present time, and in the absence of 
more experimental data speculation regarding it can be of little value. 
1 Dubois regards Pholas luciferin as a natural albumin and luciferase as an oxidizing enzyme 
made up of iron associated with a protein. ‘‘La Vie et la Lumieére,’”’ Paris, 1914. 
