78 Papers from the Department of Marine Biology. 
photophelein as comparable to luciferin, two photogenic substances 
described by Dubois! in the beetle Pyrophorus noctilucans and in the 
mollusk Pholas dactylus. Dubois believes that luciferase is an oxidizing 
enzyme which oxidizes luciferin, an oxidizable substance, with light 
production. Neither luciferase nor luciferin alone in solution can pro- 
duce light, but light appears if solutions of the two are mixed and it 
continues as long as any luciferin remains unoxidized. Dubois has 
also been able to produce light by oxidizing luciferin (alone) with a 
small crystal of KMnQO,, by H.O:2 (with or without blood containing 
hemoglobin), BaO:, PbO», and other oxidizing agents. Through the 
kindness of Professor Dubois, I have received some material of Pholas 
dactylus preserved in sugar and I can confirm his results on the effect 
of KMnOQ, and other oxidizing agents in producing light with luciferin 
of Pholas. I have likewise repeated my own experiments with the 
photophelein of Cypridina, using a whole series of oxidizing agents 
applied in the same way as with the luciferin of Pholas, and, as previ- 
ously, have failed to obtain any light with this substance.? The differ- 
ence in our results is, therefore, not to be referred to a difference in 
method of experiment but to a difference in the animals themselves. 
I found also that if one takes a concentrated solution of photogenin, 
filtered through a porcelain or silicious filter candle to remove all 
granules and cell fragments, and adds to it a little saponin powder or 
amyl alcohol or NaCl or other inorganic salt crystals or tissue extracts 
of certain invertebrate non-luminous animals, that light would appear. 
Because NaCl could not possibly be oxidized by photogenin (=lucif- 
erase), or any other substance, and because of my inability to make 
photophelein (=luciferin) luminesce with oxidizing agents, I regarded 
the photophelein itself as the source of the light and the oxidizable body. 
I have compared photogenin to zymase and photophelein to the co- 
enzyme of zymase, believing that we are dealing with a system similar 
to that of the enzyme—co-enzyme system of yeast. Hence the name 
photophelein or body assisting in the production of light. 
I now believe that under the term photophelein I have previously 
included two separate substances. One of these is the thermostable 
dialyzing substance extracted from Cypridina by hot water. Although 
this substance can not be oxidized with light production by oxidizing 
1 Dubois, R., Compt. rend. Soc. Biol., 1885, xxxvii, 559. 
2 The following oxidizing agents (added, where possible, in minute crystal or powder form) all 
gave light with Pholas luciferin, but no light with Cypridina luciferin: KMnO4, K2Cr207, PbO», 
NavO2, BaOo, MnOo, KsFe(CN)¢, KeS203, NazBsOs, and H2O2. The following oxidizing agents 
gave no light with either Pholas luciferin or Cypridina luciferin: KeCrO4, CrO3, KClO3, KC104, 
FeCl;, KNOs, Cl or Br water, I in KI, Na hypochlorite, hypobromite, or hypoiodite, colloidal Ag 
or Pt, benzoyl peroxide, potato or turnip juice, or blood containing hemoglobin or hemocyanin. 
If H,O: in addition to the oxidizing agent is added to Cypridina luciferin, no light appears except a 
faint momentary flash with Na hypochlorite and hypobromite. As this faint flash also appears 
with thoroughly boiled extracts of Cypridina, lacking luciferin, it can have no significance. If 
H.O2 in addition to the oxidizing agent is added to Pholas luciferin, the light is in some cases 
brighter than with HQ, alone. 
