Living Lights that Never Die 281 



plied to light-producing animals owes its reason to the 

 fact that the illumination resembles the glow of phos- 

 phorus, but, in reality, it has nothing to do with that 

 element. Phosphorus, in its free and luminous state, 

 is highly poisonous to all living animal substance. 



Contrary to popular opinion, the peculiar property 

 of phosphorescence is by no means a rare one or con- 

 fined to a narrow range of animals. The fact is, in the 

 animal kingdom, in groups extending from the proto- 

 zoans to the vertebrates, there are more than three 

 hundred genera containing one or more species which 

 are known to emit light. The majority live in the sea. 

 Of these, Noctiluca is the best known, but it is not the 

 most intensely luminous. That distinction goes to a 

 little ostracod crustacean bearing only the Latin name 

 Cypridena hilgendorfii, because it is known to few 

 others than naturalists. So powerful is the light from 

 this creature that one part of its luminous gland in 

 nearly two billion parts of water will give a visible glow 

 to that medium. If a person possessed an organ that 

 gave the same proportionate volume and intensity of 

 illumination, it w^ould be sufficient to light up the area 

 of a fair-sized city. 



In the light of Noctiluca, experimenters have discov- 

 ered two very interesting properties. It has no heat, 

 and It has no light rays that are invisible to the eye. 

 The bolometer, a heat-measuring instrument so sensi- 

 tive that it can register the heat from the stars, has 

 revealed — as, in truth, it has revealed in the case of all 

 light-producing animals — that the phosphorescence is 

 utterly without warmth, that it is what is called "cold 

 light." My statement about the light rays may need 



