124 THE HAUNTS OF LIFE 



mains the same. It is interesting to find that 

 the bones of some deep-sea fishes are so lightly 

 built that one can run a needle through them 

 without breaking the point. 



It is not asserted that substantial skeletons 

 do not likewise occur in the deep waters. 

 That is another way of solving the problem, 

 which some of the deep-sea corals illustrate. 

 But the usual way out of the difficulty is what 

 we have tried to explain: the pressure is cir- 

 cumvented by making the whole body very 

 permeable. 



PUZZLE OF PHOSPHORESCENCE 



While there are many features of deep-sea 

 animals which we can interpret as well fitted 

 to the peculiar conditions, there are others 

 which are puzzling. One of these is the com- 

 mon occurrence of light-production. It is diffi- 

 cult to get rid of the word " phosphorescence " 

 as a name for the light given out by some liv- 

 ing creatures both plants and animals. But 

 whatever be the nature of the light given out 

 by fire-flies and glow-worms, fire-flames and 

 sea-pens, it is not phosphorescence. It might 

 be called chemi-luminescence, for it is a by- 



