LWING LAMPS 237 



swiftly in and out, backwards and forwards, could be distinctly 

 made out till the light became exhausted. After a period of 

 rest the process was repeated. 



Of the curious arrow-worms or chaetognaths a few are phos- 

 phorescent, as are some of the sea planarians and rotifers. 



Of the echinoderms very few are phosphorescent, only a few 

 brittle-stars and those strange star-hshes called Brisingas. But 

 these are often very bright. On the coast of Europe the com- 

 mon brittle-star ipphiothrix) as it occurs between the tide- 

 marks, is never luminous, at least when large. But the same 

 sort from deeper water glows with a pale greenish light. 



On our coasts and elsewhere there live buried in the mud 

 curious brittle-stars remarkable for the great length of their 

 arms. These are luminous on the under side, showing a double 

 row of lights on each of the long rays. Some of the other 

 kinds that live along the shores hidden under stones or buried 

 in the mud are also luminous. One dredged by Mr. Agassiz 

 in the Caribbean, like one of the Mediterranean kinds, was 

 exceedingly phosphorescent, emitting at the joints along the 

 whole length of its arms a bright bluish green light. 



Our two most conspicuous jelly-lishes on the New England 

 coast, the translucent whitish Aurellia so common in late 

 summer and the red Cyanca, are never luminous. But many 

 other jelly-fishes, large and small, are remarkable for their 

 bright and usually whitish flashes. Looking over a steamer's 

 stern watching for Pyrosomas you often see bright flashes 

 quickly fading. These come from jelly-fishes, usually from 

 one known as Pelagia. 



Most of the ctenophores give out a brilliant flash, greenish 

 to almost white. In some even the very youngest and the 

 eggs are luminous. Exposure to sunlight or to any other light 

 if sufficiently prolonged diminishes or completely destroys the 

 power of emitting light among the ctenophores, just as in the 

 case of the West Indian fire-flies. 



Siphonophores are often luminous, like most of the other 

 jelly-fishes usually only in special regions. 



