1 64 PHOTOGENIC BACTERIA. 



phorescence, 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 such 

 times exceptionally present in sufficient quantity in the waves. 



The spectrum of the bluish-green light emitted by Micrococcm 

 Pflugeri is, according to Ludwig, a continuous one, and extends- 

 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. FORSTER (I.). Here the 

 blue and violet rays predominate, and, consequently, these organ- 

 isms can be photographed by their own light, a result first success- 

 fully attained by Forster in conjunction with Van Haren Noman. 

 One year later B. Fischer also demonstrated that the light 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 photo- 

 bacteria, 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 success- 

 fully 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 re- 

 pays 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 off 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 Tali- 

 trus of a bacterium which is both pathogenic and luminous, in- 

 habiting 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, visible nearly a dozen yards off, 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. 



