80 Papers from the Department of Marine Biology. 
ferase and then the mixture glows for a considerable time. It is 
obvious that for this experiment to succeed there must be more 
luciferin present than can be completely adsorbed by Fe(OH); and 
so little luciferase present that it is completely adsorbed by the 
Fe(OH);. Suppose we have a mixture of Fe(OH)s, luciferase, and 
luciferin complying with the above conditions. Can we in any way 
remove the luciferase from its adsorbed condition on the colloidal 
Fe(OH);? This might theoretically be done in two ways, and we 
actually find in practice that both methods are possible. Anything 
which precipitates the colloidal Fe(OH); will decrease the surface 
available for adsorption of luciferase, and if the surface area is suffi- 
ciently decreased some luciferase may be forced into solution again, 
where it is able to oxidize the luciferin. If we add NaCl crystals to 
the colloidal Fe(OH);—dilute luciferase—more concentrated luciferin 
mixture, the Fe(OH); is precipitated and light appears. If, in place 
of NaCl crystals, we add a trace of saponin, the colloidal Fe(OH), 
is not precipitated, but light also appears. This is an example of 
the second method of removing luciferase from an adsorbed condi- 
tion—namely, by using a material (saponin) which is more strongly 
adsorbed than the luciferase and which is able to replace it as adsorbed 
body. I believe these to be the explanations of the effect of NaCl 
crystals, saponin, etc., in giving light with luciferase solutions, except 
that the luciferase is in excess and a small amount of adsorbed (or 
combined) luciferin is present which is liberated by NaCl or saponin 
and gives light with luciferase. Photophelein probably acts in a 
manner analogous to the saponin. 
I have considered the thermostable, dialyzing substance as similar 
to the luciferin of Pholas, despite the fact that Dubois finds Pholas 
luciferin destroyed at 70° C., whereas Cypridina luciferin is destroyed 
only by boiling for several minutes in an open beaker. I find that this 
destruction of Cypridina luciferin on short boiling is due to the in- 
creased rate of oxidation at the boiling-point and that no destruction 
of Cypridina luciferin will occur if boiled in an atmosphere of hydrogen. 
Cypridina luciferin is truly thermostable, but is oxidized to oxyluciferin 
on boiling in the air. We may say that Pholas luciferin is similar but 
certainly not identical with Cypridina luciferin. If so, we should expect 
to obtain light on mixing Pholas luciferin and Cypridina luciferase, yet 
no light appears. Neither is there light on mixing Cypridina luciferin 
and Pholas luciferase, although the Pholas luciferase I was able to pre- 
1T have endeavored to repeat this experiment with the luciferin of Pholas sent me by Professor 
Dubois, but without success. Pholas luciferin boiled in a current of hydrogen for 15 minutes 
would give no light when a crystal of KMnOQ, was added. The hydrogen was produced in a 
Kipp generator and may have contained a little air. In my experience short (20 to 40 seconds) 
boiling of Pholas luciferin does not completely destroy its power of producing light when a crystal 
of KMnQ, is added. 
