126 PHOTOGENIC BACTERIA 



held in the main by Quatrefages, Owsjannikow, Ludwig, and Dubois, tlie 

 observer last mentioned designating the assumed phosphorescents luciferin. 

 The most important effect of the photobacteria, viz., marine phosphorescence, 

 stands, however in the way of the general applicability of this interpretation, 

 the external conditions under which this phenomenon is produced being still 

 unknown. It is consequently uncertain whether the food stuffs (aldehydes and 

 ammonia bases) necessary for the production of the phosphorescents are at siu-h 

 times exceptionally prasent in sufficient quantity in the waves. 



The spectrum of the bluish-green light emitted by Micrococcus Pj'Hyri is, 

 according to Ludwig, a continuous one, and excends from the line b (green) into 

 the violet. Equally continuous and more extensive occupying the entire breadth 

 from D to G are the spectra of two European species discovered by B. Fischer, 

 and a luminous bacterium described by J. FORSTEK (I.). Here the blue and violet 

 rays predominate, and, consequently, these organisms can be photographed by 

 their own light, a result first successfully attained by Forster iu conjunction 

 with Van Haren Noman. One year later B. Fischer also demonstrated that the 

 liirht from streak cultures of these microbes is strong enough to illuminate and 

 photograph other adjacent objects, such, for example, as a watch. 



Marine phosphorescence can be caused not only by photobacteria, but also 

 by a variety of low forms of animal life. When these latter come into play, then 

 the illumination of the water only becomes well developed provided the latter is 

 in motion and the necessary supply of oxygen is thereby copiously supplied to 

 the photogenic animals. If, on the other hand, photobacteria are in question, 

 the entire surface of the water glistens uniformly and continuously with a soft 

 lustre. Ludwig was the first to successfully produce marine phosphorescence 

 artificially and on a small scale, and the experiment was then repeated on 

 a larger scale by B. Fischer in the Berlin Aquarium. The demonstration 

 well repays the slight trouble involved. Cultures of photobacteria are prepared 

 on salt-water fish, on which they grow and form a mucinous coating, which, on 

 being stripped oft' in salt water and dispersed through it, immediately produces 

 marine phosphorescence capable of prolonged duration. 



A beautiful observation made by A. GIARD (I. and II.) must be recorded 

 here, viz., his cultivation from the luminous Talitrus of a bacterium which is 

 both pathogenic and luminous, inhabiting the abdominal cavity of the aforesaid 

 aquatic animal, fully permeating all its organs, and, finally, causing its death. 

 During the prevalence of this malady the victim shines with a green light, 

 vi-ible nearly a dozen yards oft', and persisting for a few hours after the death 

 of the animal. This fact, established as it has been by successful inoculation 

 experiments, induces the supposition that the luminosity of other small marine 

 animals (infusoria, polyps, and medusae) may also be due to photobacterial 

 infection. 



