C. J. p. SPRUIT A\D A. SPRUIT-VAX DER BURG 113 



nescence after the end of the irradiation, which is a first order reac- 

 tion. This recovery of luminescence also exists in those bacteria which 

 have lost their reproductive capacity by exposure to wavelengths 

 shorter than 300 mfx.. Ultimately, such "killed" bacteria emit light many 

 times more intense than a nonirradiated part of the same culture. 

 This observation is in perfect harmony with the old views of van 

 Schouwenburg that bacterial luciferin has a dual function and that 

 part of it is involved in a reaction other than the luminescent one. 

 Obviously in such damaged bacteria more luciferin is accessible to 

 the luminescent reaction after recovery is complete than in normal 

 , bacteria. This may well be due to the fact that that part of the respira- 

 tory system responsible for the reversible dehydrogenation of luciferin 

 (see van Schouwenburg, 1938) is inactivated by irradiation with light 

 of short wavelengths. Although definite proof is lacking, these facts 

 support the conclusion that van der Kerk's inactivation spectrum in- 

 deed is the absorption spectrum of the bacterial luciferin or its imme- 

 diate precursors. 



The same authors also made a few observations on the inactivation 

 spectrum of Ph. splendidum and Ph. fischeri, though only in the visi- 

 ble region. It is highly regrettable that they have not found it pos- 

 sible to include in their study the ultraviolet parts of these spectra, but 

 from what has been published it is clear that, whereas the inactiva- 

 tion spectra of Ph. splendidum and Ph. fischeri cannot be distinguished 

 on the basis of the material available, they are certainly not identical 

 with the inactivation spectrum of Pli. phosphor eum. The situation is 

 therefore somewhat similar to that of the emission specti"a. This ob- 

 servation raises the question of mirror symmetry'. As was explained 

 earlier, chemiluminescence emission spectra, being related to fluores- 

 cence spectra, should show qualitative mirror symmetry with the 

 long-wavelength bands in the absorption spectra of the compounds 

 in question. If we observe a certain amount of symmetry between the 

 emission and the inactivation spectra of a number of organisms, we 

 may therefore take this as a fair indication that both types of spectra 

 belong to the same, or at least to pairs of closely related compounds. 

 Now, this is what is really observed. Fig. 11. The form of the inactiva- 

 tion spectra really is rather different, but the important point is the 

 small overlap for all pairs of spectra. This comparison therefore is a 



