124 THE HAUNTS OF LIFE 



remains 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 common 

 occurrence of light-production. It is difficult 

 to get rid of the word " phosphorescence " as 

 a name for the light given out by some living 

 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-play 



