PHYSICAL NATURE OF ANIMAL LIGHT 



53 



is similar in absorption properties to complex carbohy- 

 drates. Transparency of the integument to the ultra- 

 violet was not studied. 



Although photographs of the spectrum of firefly {Pho- 

 tinus) light show that it extends only to the beginning 

 of the blue, Forsyth (1910) reports ultra-violet radiation 

 in luminous bacteria. He exposed a. plate for 48 hours to 



50 



S 40 



.S .30 



d 

 o 



xn 



—I r- 



"T 



Wave lengths in yu. --.00! mm. 



•g 



a 



"20 



»0 





|P> X . O IX . O XI X . 



I 2345678 9>U 



Fig. 10. — Transmissivity of the integument of fireflies to infra-red radiation (after Coblentz.) 



the spectrum of bacterial light dispersed by a quartz prism 

 and got a continuous band from A = 0.50/x (the lower limit 

 of sensitivity of the plate) to A = 0.35ia. However, Mc- 

 Dermott (1911 d) was unable to observe fluorescence of 

 p-amino-ortho-sulpho-benzoic acid, which responds to the 

 ultra-violet light. Molisch (1904, book) photographed bac- 

 terial and fungus light through glass and through a piece 

 of quartz and found no difference in density on the plate. 

 As the exposure was brief, to avoid saturation, and as the 

 ultra-violet, which passes quartz but not glass, has a much 



