GENERAL CHARACTERS OF DISCOPIIORA LUMINOSITY. 531 



forming the two followiLg Orders, is derived from a Greek word 

 signifying Nettles, and was employed to designate them by the 

 ancient Greeks. The name of " Stang-fishes," by which they 

 are also known in some localities, evidently alludes to their 

 urticating powers. 



1183. They almost always float near the surface of the water, 

 advancing slowly by the flapping of their umbrella-like disc. 

 They are seen both in the open sea and at the mouths of rivers, 

 usually in vast numbers together, all moving in the same direction ; 

 but none of them can endure a rough sea, and at the slightest 

 disturbance they sink into the depths of the ocean. They are 

 often driven by the winds and currents, which they cannot resist, 

 against the hard shore, and there they are soon beaten to pieces 

 by the waves ; or they are left dry by the tide, which they have 

 not the power of following, and speedily melt like the spangled 

 hoar-frost beneath the sunbeam. 



1184. The voyager in the open sea, however, often encount- 

 ers whole fleets of these and the allied animals of the next Order, 

 extending as far as the eye can reach, basking as it were in the 

 sunshine that illumines the surface, and reflecting its rays with 

 all the gorgeousness of the most brilliant iridescent hues. Most 

 of the Acalephae seem inclined thus to associate ; and in tropical 

 regions, where they exist in the greatest abundance, the voyager, 

 after passing through a fleet of one species, will in a short time 

 encounter an equally extensive collection of another kind. It 

 is not by day only, however, that these animals delight the eye of 

 the mariner. It is chiefly to them that the phosphorescence of the 

 sea is due, which is occasionally observed on our own coasts, but 

 only in a degree which affords a faint idea of the extraordinary na- 

 ture of this phenomenon as it presents itself in warmer latitudes. 

 The whole surface of the ocean displays a diffused luminosity, 

 like that of the Milky-way on a clear night. The path of the 

 ship is marked by a brilliant line of glowing light. The waves, 

 as they gently curl over one another (this phenomenon is never 

 seen with a rough sea), break into brilliant spangles. The oars 

 of a boat rowing over them, seem dripping with pearls when 

 raised from the water ; and every stroke is marked with a new 



