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SPECTROSCOPIC INVESTIGATIONS 



R4 R5 



Ar. = ring system with aromatic properties. 



Ri . . . R5 may represent other groups, not contributing materially 

 to the absorption spectrum, but required in connection with the other 

 functions of the molecule. 



If we now attempt to summarize the conclusions that can be drawn 

 from the spectroscopic investigations of bioluminescent phenomena, 

 we are forced to admit that the results have not come up to the origi- 

 nal expectations. It is not possible to draw definite conclusions as to 

 the structure of the emitting molecules from the bioluminescent emis- 

 sion spectra, and it is not likely that further theoretical developments 

 will make such a conclusion possible. On the other hand, the diver- 

 gence between the emission spectra of various organisms is a demon- 

 stration that the emitting systems are considerably different. Only in 

 the case of the three fungi examined, has the conclusion to identify the 

 bioluminescent processes seemed justified. At the same time, the study 

 of chemiluminescence spectra has led to the important observation 

 that in this case, emission spectra are closely related to fluorescence 

 spectra of molecules involved in the luminescent reactions. This makes 

 it attractive to compare bioluminescence emission spectra with fluores- 

 cence spectra of known biologically important compounds. This com- 

 parison does not point to an identity of the emitting molecules with 

 such generally occurring substances. This same conclusion follows 

 from an examination of the three absorption spectra of bioluminescent 

 compounds, obtained so far. Together, these facts seem to indicate 

 that bioluminescence is the result of certain specific and, as yet, not 

 fully known metabolic steps. Moreover, it is likely that different organ- 

 isms have fundamentally different types of luminescent systems which 

 may not be even superficially related. 



