It is not the purpose of this book to deal with every phase of bioluminescence.
"The Nature of Animal Light"
E. Newton Harvey
Indeed, it is now possible to go much further than this and describe the properties of the photogen, but we must not lose sight of the fact that it was recognized very early in the history of bioluminescence, that water, oxygen, and a photogenic substance were necessary for light production.
"The Nature of Animal Light"
E. Newton Harvey