| | | | | Mnemiopsis Leidyi | Peters, 1905 | 9° | 21° | 37° | | | | | | Noctiluca miliaris | Quatrefages, 1850 | 1° | ... | 40° | | | | | | Noctiluca miliaris | Harvey, E. B., 1917 | <0° | ... | 48° | | | | | | Cavernularia haberi | Harvey, E. N., 1915 | <0° | ... | 52° | | | | | | Watasenia scintillans | Shoji, R, 1919 | ... | 16-31°| 49° | -------------------------+---------------------+-------+-------+-------+ We are thus led to the conclusion that intensity of luminescence is dependent on the velocity of oxidation of luciferin and that with lowered reaction velocity the spectral composition of the light changes. The maximum emission shifts toward the yellow. I believe, however, that in _Cypridina_ also, the luminescence intensity depends not only on reaction velocity but on the particular manner in which luciferin is oxidized. _Cypridina_ luciferin will luminesce only in presence of _Cypridina_ luciferase and no light can be obtained from _Cypridina_ luciferin and a host of different oxidizers (with or without H_{2}O_{2}) such as are able to oxidize pyrogallol. Luciferin will also oxidize in the air spontaneously but no light is produced. It is easy to show that this spontaneous oxidation may be much more rapid than an oxidation with luciferase and yet light appears only in presence of the latter. If a concentrated solution of luciferin is kept near the boiling point it will be completely oxidized to oxyluciferin in four or five minutes. No light appears if air or even if pure oxygen is bubbled through it. The same solution kept at 20° with a small amount of luciferase will luminesce continuously and not be completely oxidized to oxyluciferin in a half hour. We can, however, cause the luciferin to oxidize as rapidly at 20° by adding concentrated luciferase as does the luciferin near the boiling point without luciferase. A bright light is produced in the former case, none in the latter case. The oxyluciferin formed from spontaneous oxidation of luciferin appears to be the same as that formed with luciferase present. Both give luciferin again on reduction. Perhaps the reaction takes place in two stages, similar to those supposed to occur in other enzyme actions: luciferin + luciferase = luciferinluciferase luciferinluciferase + O (or minus H_{2}) = oxyluciferin + luciferase. We may then assume as a tentative hypothesis that luminescence only occurs during oxidation (addition of O or removal of H) of the luciferinluciferase compound.