262 PHYSIOGNOMY OP PLANTS. 



appearance of the sea is due partly to living animals, such as are 

 spoken of above, and partly to organic fibres and membranes derived 

 from the destruction of these living torch-bearers. The first of 

 these causes is undoubtedly the most usual and most extensive. In 

 proportion as travellers engaged in the investigation of natural phe- 

 nomena have become more zealous in their researches, and more 

 experienced in the use of excellent microscopes, we have seen in 

 our zoological systems the groups of Mollusca and Infusoria, which 

 become luminous either at pleasure or when excited by external 

 stimulus, increase more and more. 



The luminosity of the sea, so far as it is produced by living organic 

 beings, is principally due, in the class of Zoophytes, to the Acalephae 

 (the families of Medusa and Cyanea), to some Mollusca, and to a 

 countless host of Infusoria. Among the small Acalephae, the Mam- 

 maria scintillans offers the beautiful spectacle of, as it were, the 

 starry firmament reflected by the surface of the sea. this little 

 creature, when full grown, hardly equals in size the head of a pin. 

 Michaelis, at Kiel, was the first to show that there are luminous, 

 silicious-shelled Infusoria: he observed the flashing light of the 

 Peridinium (a ciliated animalcule), of the cuirassed monad the Pro- 

 rocentrum micans, and of a Rotifera to which he gave the name of 

 Synchata baltica, (Michaelis iiber das Leuchten der Ostsee bei 

 Kiel, 1830, s. 17.) The same Synchata baltica was subsequently 

 discovered by Focke in the Lagunes of Yenice. My distinguished 

 friend and Siberian travelling companion, Ehrenberg, has succeeded 

 in keeping luminous infusoria from the Baltic alive for almost two 

 months in Berlin. He showed them to me in 1832 with a micro- 

 scope in a drop of sea-water : placed in the dark, I saw their flashes 

 of light. The largest of these little infusoria were 1-8 th, and the 

 smallest from 148th to 1-9 6th of a Paris line in length (a Paris 

 line is about nine-hundredths of an English inch) : after they were 

 exhausted, and had ceased to send forth sparkles of light, the flashing 

 was renewed on their being stimulated by the addition of acids or 

 of a little alcohol to the sea-water. 



By repeatedly filtering water taken up fresh from the sea, Ehren- 

 berg succeeded in obtaining a fluid in which a greater number of 

 these luminous creatures were concentrated. (Abhandlungen der 



