250 



cially the phosphorescence of the latter I have minutely examined, no character being 

 better qualified to show the process of mutability and to enable us more quickly and 

 precisely to judge of the vital energy of the culture material. Errors in the nutrition 

 are in this way prevented, which so easily occur in microbiological experiments, in 

 particular by too strong concentration and too alcaline reaction. Besides, the function 

 of phosphorescence is not only found in certain luminous bacteria, but it is widely 

 spread throughout the natural system and a remarkable similarity exists everywhere 1 ), 

 notwithstanding the enormous differences in the respective phosphorescent organs. 



Another consideration which induced me to study with particular care the pro- 

 duction of light by living microbes was the following. 



I saw the great difficulty of explaining by the enzyme theory a function so 

 obviously the attribute of the living protoplasm. Yet I had the conviction that if it 

 were possible to account for this exceptional character by that theory, the same would 

 be the case for any other character, physiological or morphological. Presently we sha'l 

 see that facts are in accordance with the expectation. 



Not all luminous bacteria are equally well qualified for this investigation. Photo- 

 bacter splendidum, common in the North Sea at the end of summer'), and Ph. phos- 

 phoreum C o h n, always present on sea-fish, whose properties are very different and 

 in many respects complementary, are recommendable. Ph. splendidum produces tryp- 

 sin, urease, diastase and invertase, and assimilates mannite with light production. Ph. 

 phosphoreum has none of these enzymes and does not attack mannite 3 ). 



The chief result of this study is that the function of phosphorescence may 

 be ascribed as well to living protoplasm as to one or more enzymes. 



I chose this function to elucidate the theory with regard to a physiological 

 character; the production of the cell-wall shall be treated to test it from a morpho- 

 logical point of view, and also in the latter case it can be shown that the protoplasm 

 as well as one or more enzymes may be regarded with the same right as the cause of 

 its formation. 



The subsequent considerations must be given in a short and somewhat aphoristic 

 but I think not unclear form. 



Enzymes considered as the bearers of phosphorescence. Irritability. 



Already in 1898 Rafael Dubois endeavoured to demonstrate that phos- 

 phorescence should be considered as caused by an enzyme-action 4 ). He experimented 

 particularly with the luminous sipho-slime of Pholas dactylus and calls the enzyme, 

 he thinks he has found luciferase and the unknown matter it acts upon luciferine. 



') Perhaps with exception of the higher Fungi, where the luminosity seems to he 

 in correlation with a state of collabescence. 



*) Die Leuchtbakterien der Nordsee im August und September. Folia microbio- 

 logica, Bd. 4 pag. i, 1915. 



8 ) Aliment photogene et aliment plastique des bacteries lumineuses. Archives Neer- 

 landaises T. 24, P. 369, 1891 (Feeding of Ph. phosphoreum Cohn). 



4 ) R. Dubois, Lemons de Physiologic generale, pag. 450 und 524. Paris 1898, Drawings 

 of the phosphorescing organ of Pholas by Ulric Dahlgren: The production of light 

 by animals. Franklin Institute, February 1916, pag. 38. 



