The firefly light by the above method of calculating efficiency is not 100 per cent. efficient because its maximum (λ = 0.567µ) does not correspond with the maximum sensibility of the eye (λ = 0.565µ), but taking into consideration also other effects of color, the firefly light would be a still more inefficient and trying one for artificial illumination, as all objects would appear a nearly uniform green hue. Indeed the distortion would be even greater than with the mercury arc, whose objectionable green hue is so well known. "We may say, therefore, that the firefly has carried the striving for efficiency too far to be acceptable to human use; it has produced the most efficient light known, as far as amount of light for expenditure of energy is concerned, but has produced it at the (inevitable) expense of range of color. The most efficient light for human use, taking into account both color and energy-light relationships, would be a light similar to the firefly light containing no radiation beyond the visible spectrum, but differing from it by being white." (Ives, 1910.) Although the spectral energy curve for _Cypridina_ light has not been worked out, it will be noted that the _Cypridina_ spectrum is much longer than that of the firefly, more nearly approaching the spectrum of an incandescent solid giving white light. It approaches, but does not attain the ideal. Although Muraoka (1896) and Singh and Maulik (1911) have described radiations coming from fireflies which would pass opaque objects and affect a photographic plate, and Dubois reports the same from bacteria, the existence of such radiation has been denied by Suchsland (1898), Schurig (1901) and Molisch (1904 book). The experiments of Molisch on luminous bacteria are of greatest interest, for they are very carefully controlled and show without a doubt that black paper or Zn, Al, or Cu sheet will allow no rays from these organisms to pass that will affect a photographic plate, even after several days' exposure. The _visible_ light of luminous bacteria will affect the plate after one second exposure. Moreover, Molisch has pointed out the errors of those who claim to have found penetrating radiation in luminous forms. It seems that certain kinds of cardboard, especially yellow varieties, or wood, will give off vapors that affect the photographic plate. The action is especially marked with damp cardboard at a temperature of 25°-35° C., and Dubois and Muraoka must have used such cardboard to cover their plates. A piece of old dry section of beech or oak trunk, placed on a photographic plate for 15 hours in a totally dark place, will register a beautiful picture of the annual rings of growth, medullary rays, junction of bark and wood, etc. Russell (1897) had previously found that many bodies, both metals and substances of organic origin (gums, wood, paper, etc.), placed in contact with photographic plates, would affect them, and concluded that vapors and not rays were the active agents. As