Phosphorescence of the Sea 535 



flagellates which have been known as " animalcules " since the time 

 of Otto Frederick Miiller (1730-1784) without a suspicion of their 

 ability to luminesce. Miiller was the first to attempt a classification 

 of animalcules and figured many forms in Vermium Terrestrium et 

 Fluviatilium seu AnimaUum Infusorium, etc., published in 1773- 

 1774. His great work, published after his death, Animacula In- 

 fusoria Fluviatella et Marina (1786) contains a Ceratium, under 

 the name of Cercaria tripos, well figured in plate XIX. Franz von 

 Paula Shrank in 1793 introduced the genus Ceratium and described 

 Ceratium tetraceras from fresh water. 



Luminous marine dinoflagellates were probably observed by John 

 MacCuUoch (1773-1835) who described in 1821 luminous Cercaria, 

 Vibrio, Vorticella, and Volvox, as well as many larger forms, from 

 the Western Islands of Scotland. Cercaria was the old name for 

 Ceratium, Vorticella was a rotifer, and Volvox a ctenophore. 



Quoy and Gaimard (1825) , doctors of the royal marine and 

 naturalists on a cruise around the world in the " Uranie " attributed 

 sea light to various " animalcules et les mollusques " but could 

 not refrain from adding that the luminous forms had a smell of 

 electricity. 



Christian Heinrich PfaflE (1773-1852), professor of medicine at 

 Kiel, probably saw dinoflagellates in 1823, and also in 1828, when 

 he declared that the sea light at Kiel was due to small organisms, 

 especially " infusoria," which would luminesce on adding ammonia, 

 acid alcohol, and ether. He carried out the interesting experiment 

 of passing an electric cunent from a voltaic cell through sea water 

 in a glass vessel and noted many moving light points when the cur- 

 rent was closed. This was probably the first use of ammonia and of 

 electricity to stimulate dinoflagellates to luminescence. F. Tiede- 

 mann (1830) also recognized luminous " infusoria," in addition to 

 medusae and ctenophores, as contributing to the light of the Adriatic. 



It is thus apparent that the tiny sparkles of the sea, due to micro- 

 scopic dinoflagellates, were recognized as the cause of diffuse phos- 

 phorescence early in the nineteenth century. MacCulloch and Pfaff 

 were certainly pioneers, but it is difficult to associate such a dis- 

 covery with any one name. 



MICHAELIS AND EHRENBERG 



Hans Molisch (1912: 14) has attributed the first clear indication 

 that dinoflagellates are luminous to G. A. Michaelis in 1830. Ehren- 

 berg also, writing in 1834, described Michaelis' paper as containing 

 " die wichtigsten Beobachtungen der neueren Zeit." Michaelis de- 

 scribed in the luminous sea water of Kiel harbor a Volvox, Cercaria 



