THE IMPENETRABLE SEA 



force or nerve energy acting through the nerve systems 

 of the Hght-producing creatures, so that it is, under 

 speciaHzed forms of structure, transformed through the 

 secretions and general tissues into radiant energy, some- 

 times chemically, sometimes mechanically. 



Translated into more modern terms : the biochemical 

 basis of luminescence consists of the interactions of a sub- 

 stance called luciferin with an enzyme called luciferase ; 

 in most organisms the presence of oxygen being needed to 

 produce the light. It is therefore to be noted that the 

 latest "explanations" are made in chemical terms. Little 

 is known of the substances concerned. It is questionable 

 whether, after over a century's intensive research into the 

 problem, scientists are any nearer the truth of the matter. 

 Accumulation of data does not necessarily imply under- 

 standing of the way the light-producing mechanisms 

 work, or of their purposes. 



It is of course obvious that some sea creatures which 

 possess light-producing devices use them as snares to catch 

 other creatures, while others use them as sexual lures to 

 attract their mates. But such obvious explanations only 

 account for a minority of the cases where creatures have 

 the power to produce light. Recent research has revealed 

 the startling fact that when numbers of mid- water nets are 

 towed at many levels in deep oceanic waters the proba- 

 bility is that no fewer than four-fifths of the fishes taken 

 will bear light organs. It therefore seems highly probable 

 that deeper and deeper research into the oceans will con- 

 firm this fact and that the percentage may well become 

 even higher. 



Creatures near the surface which are reached by the 

 light of the sun obviously do not need such organs as 

 much as those which live lower down, where the sun's 

 light does not penetrate. Miles down in the deeps, 

 myriads of creatures may be using light-producing devices 

 in ways completely unsuspected by man. 



Of the deep-sea angler-fishes, two species have an 



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