BY CRAB-LIGHT. 73 



been known ; Viviani observing it in a number of species in 

 the beginning of the present century. 39 There is one pecul- 

 iarity about many of these small animals ; that is, the light 

 has a more decided red tint than that of any other group of 

 animals. This is especially true of many of the water-fleas, 

 or Entomostracans, and the extremely transparent, ten-footed 

 kinds. The light is often intense, but fitful and shortlived. 

 It seems to start from the locality where the legs join the 

 body, and rapidly spreads beneath the skin until the entire 

 body appears to be suffused with light, and the little animal 

 consumed with an internal fire. Yet if a bushelful of these 

 gleaming living lights were confined, and a thermometer 

 placed among them, it would not show the slightest variation 

 or evidence of heat. The little Cyclops is very common 

 in our fresh-water ponds, and forms a beautiful object under 

 the microscope. 



Along our sea-shores we may often see, under the rocks, 

 clinging to the eel-grass, or among the thickly growing stems 

 of Carolina officinalis, in some pool left by the tide, gleaming 

 spots that move about in an erratic manner; now many 

 collecting together, then breaking up into small patches of 

 light, which in turn separate again. They are curious Crus- 

 taceans, known scientifically as the Idotea phosphorea. By 

 day we shall find that they are usually spotted or entirely 

 a bright yellow; at night emitting fitful gleams, perhaps 

 as signals or as means of communication to their fellows. 



In the Arctic regions beautiful lights have often been seen, 

 due to a minute crustacean. Lieut. Bellot first observed it 

 in the North-American polar regions, and Nordenskiold 

 refers to it in his " Voyage of the Vega." The most brilliant 

 displays have been seen at Mussel Bay. Nordenskiold says, 



