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- 
