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THE AMEBIC AN NATURALIST [Vol. XLV 



on which they feed, but this argument would not hold for 

 the imagos, which are much more active. 



Most of the above statements apply with equal force 

 to the Pyrophorini, the luminous Elateridse of the tropics ; 

 these insects are herbivorous, however, and the aggres- 

 sive significance does not hold for them. 



It would seem, then, very probable that similar condi- 

 tions obtain in the abyssal region, with its dim weird, 

 phosphorescent light. The light produced by the Lam- 

 pyridae has recently been shown by Ives and Coblentz 3 to 

 have the extremely high radiant efficiency of 96.5 per 

 cent., against 4 per cent, for the best artificial illuminant. 

 The spectrum of this light is a continuous band extending 

 from the upper red to the lower blue with a maximum 

 intensity in the yellow-green. This spectrum is of wider 

 range than that of the sea-forms cited by Nutting, 4 but 

 can hardly be of less efficiency. The light of the Lam- 

 pyridae is generally stated to be yellow, or greenish ; there 

 are some slight variations among different species, but in 

 the main the lights are similar ; it seems that a great many 

 of the marine organisms also give a light of similar 

 tone. Therefore colors whose wave-lengths are within 

 the limits of those of the emitted lights of these forms, 

 would be distinguishable in such a biophotogenic light. 

 Although we do not yet know the full details of the 

 process of the production of light by living forms, it is 

 not too much to assume that Nature has developed it to 

 a point very near to the maximum possible efficiency, and 

 if such is the case, the luminous oceanic forms could emit 

 a very penetrating illuminating radiation with very little 

 expenditure of energy, and though this light might not be 

 of any considerable intensity, as judged by our eyes, it 

 could undoubtedly serve as quite a useful light to the 

 large-eyed denizens of the deep. 



The photogenicity of Salpa, Noctiluca and other such 

 simple forms, which are without definite organs of sight, 



3 Bulletin of the U. 8. Bureau of Standards, 1910, Vol. 6, pp. 321-336. 



4 Supra b, page 10. 



