428 THE INHABITANTS OF THE SEA. 



Polar Seas are illuminated by its fairy light. " The nature 

 of its luminosity," says Dr. Carpenter, " is found by microscopic 

 examination to be very peculiar ; for what appears to the eye to 

 be a uniform glow is resolvable under a sufficient magnifying 

 power into a multitude of evanescent scintillations, and these 

 are given forth with increased intensity whenever the body of 

 the animal receives any mechanical shock." 



The power of emitting a phosphorescent light is widely dif- 

 fused both among the free-swimming and the sessile Ccelenterata. 

 Many of the Physophoridse are remarkable for its manifestation, 

 and a great number of the jelly-fishes are luminous. Our own 

 Thaumantias lucifera, a small and by no means rare medusid, 

 displays the phenomenon in a very beautiful manner, for, when 

 irritated by contact of fresh water, it marks its position by a 

 vivid circlet of tiny stars, each shining from the base of a 

 tentacle. A remarkable greenish light, like that of burning 

 silver, may also be seen to glow from many of our Sertularians, 

 becoming much brighter under various modes of excitation. 



Among the Ctenophora the large Gestum Veneris of the 

 Mediterranean is specially distinguished for its luminosity, and 

 while moving beneath the surface of the water gleams at night 

 like a brilliant band of flame. 



The Sea-pens are eminently phosphorescent, shining at night 

 with a golden-green light of a most wonderful softness. When 

 touched, every branchlet above the shock emits a phosphoric 

 glow, while all the polyps beneath remain in darkness. When 

 thrown into fresh water or alcohol, they scatter sparks about in 

 all directions, a most beautiful sight; dying, as it were, in a 

 halo of glory. 



But of all the marine animals the Pyrosomas, doing full 

 justice to their name (fire-bodies) seem to emit the most vivid 

 coruscations. Bibra relates in his "Travels to Chili " that he once 

 caught half a dozen of these remarkable light-bearers, by whose 

 phosphorescence he could distinctly read their own description 

 in a naturalist's vade-mecum. Although completely dark when 

 at rest the slightest touch sufficed to elicit their clear blue-green 

 light. During a voyage to India, Mr. Bennett had occasion to 

 admire the magnificent spectacle afforded by whole shoals of 

 Pyrosomas. The ship, proceeding at a rapid rate, continued 

 during an entire night to pass through distinct but extensive 



