PHYSICAL NATURE OF ANIMAL LIGHT 61 



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 fire- 

 fly 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 ditfering from it by being white." (Ives, 1910.) Al- 

 though 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 great- 

 est 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 alfect 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 



