ILLUSTRATIONS (5) PHOSPHORESCENCE OF THE OCEAN. 247 



of nature have learnt to employ powerful microscopes, the 

 more our zoological systems have been enriched by new groups 

 of mollusca and infusoria, whose property of emitting light 

 either at will or from external stimulus has been recognised. 



The luminosity of the sea, as far as it depends on living 

 organisms, is principally owing, among zoophytes, to the 

 AcalephaB (the families of MedusaB and Cyanera), to some 

 Mollusca, and to an innumerable host of Infusoria. Among 

 the small Acalephaj (Sea-nettles), the Mammaria scintillans 

 presents us, as it were, with the glorious image of the starry 

 firmament reflected in the surface of the sea. When full- 

 grown this little creature scarcely equals in size the head of a 

 pin. The existence of siliceous-shelled luminous infusoria 

 was first shown by Michaelis at Kiel. He observed the 

 coruscation of the Peridinium, (a ciliated animalcule,) of the 

 Cuirass-monad (Prorocentrum micans], and of a rotifer, 

 which he named Synchata baltica,* the same that Focke 

 subsequently found in the lagoons of Venice. My distin- 

 guished friend and fellow traveller in Siberia, Ehrenberg, 

 succeeded in keeping two luminous Infusoria of the Baltic 

 alive for nearly two months at Berlin. I examined them 

 with him in 1832; and saw them coruscate in a drop of 

 sea- water on the darkened field of the microscope. When 

 these luminous Infusoria (the largest of which was only \ 

 and the smallest from -% to -$ of a Parisian line in length) 

 were exhausted, and ceased to emit sparks, they would 

 renew their flashing on being stimulated by the addition of 

 acids or by the application of a little alcohol to the sea- water. 



By repeatedly filtering fresh sea-water, Ehrenberg suc- 

 ceeded in procuring a fluid in which a large number of these 

 light-emitting animalcules were accumulated.! This acute 

 observer has found in the organs of the Photocharis 

 which give off flashes of light (either voluntarily or when 

 stimulated), a cellular structure of a gelatinous character 

 in the interior, and which manifests some similarity with 

 the electric organ of the Gymnotus and the Torpedo. 

 "When the Photocharis is irritated, in each cirrus a 

 kindling and a gleaming of separate sparks may be observed, 

 which gradually increase and at length illuminate the 



* Michaelis, Ueberdas Ltitchten der Ostsee bei Kiel, 1830, s. 17. 

 t Abhandlungen der Akad. der Wiss. zu Berlin aus dem J. 183S, 

 e, 307, 1834, s. 537-575, 1838, s. 45, 258 



