PHOSPHORESCENT APPEARANCE OF THE SEA. 



By C. Dubois, F. G. S. 



At certain seasons of the year particularly, the sea presents, at night, a lumi- 

 nous appearance — small sparks being, as it were, constantly emitted in quick suc- 

 cession, similar to an electrical series. Naturalists have long been undetermined 

 as to the precise cause of this pleasing phenomenon ; but their explanations are 

 sometimes contradictory, and often doubtful. By some it was ascribed to electri- 

 city or magnetism ; by others to the putrescent state of vegetable or animal matter 

 floating on the surface of the water ; others, much nearer the truth, attributed the 

 phosphorescent appearance of the sea to myriads of luminous animalculae ; and 

 there is nothing to prevent the conclusion that these different opinions have, when 

 united, explained the principal features of the phenomenon ; but the error lies in 

 exclusively ascribing it to either. 



The luminosity of the sea is evidently due, in many instances, to the presence 

 of excessively numerous animalculae, possessing the property of throwing out small 

 bright sparks while they are alive and in a state of activity : it may, also, occur 

 that the vegetable and animal rejectimenta exhibit a phosphorescent light ; other 

 simple mucous substances, incapable of definition, may do the like ; and various 

 mysterious chemical combinations may also contribute to the same effect : but, 

 generally speaking, the luminous brilliancy of the sea is most frequently occasioned 

 by marine animalia. Animal phosphorescence is either general or particular : in 

 the latter case, it is produced by animals of a greater or smaller structure, and not 

 numerous in a circumscribed space : these are polypi, radiata, medusae, pyrsomae, 

 biphorae, and some species of fishes, &c. The general phosphorescence of the 

 sea: — which always extends over a far greater limit — must, therefore, be attributed 

 to myriads of microscopic animals. Peron, Eschscholtz, Quoy, Gaimard, Mer- 

 tens, Surriray, Lesson, and many other distinguished Naturalists, have described 

 these animals, and observed that they lose their luminous property after death, or 

 in consequence of a loss of activity. In hot and tempestuous weather, these ani- 

 mals are most abundantly seen, and their phosphorescence more considerable. It 

 is easy to convince ourselves that to their existence the luminous appearance of 

 the sea, in certain situations, can alone be attributed ; since a quantity of water 

 exhibits light in a receptacle, so long as it contains living animals of that species, 

 and it ceases to be so if they are deprived of life by the insertion of a tin wire 

 into the water. 



In the ocean, and on the French coasts, the animal producing this phenome- 

 non is named, by M. Surriray, Noctiluca miliaris ; and we here give its portrait, 

 immensely magnified, since its natural size does not exceed 1 -1000th of an inch. 



