puncture be made in the air bladder of a big sea- 

 horse, and a bubble of gas even as minute as a 

 match-head be allowed to escape, all equilibrium 

 is lost and the creature sinks to the floor where it 

 must remain helplessly crawling around until the 

 puncture heals and a supply of gas is regenerated 

 sufficient to maintain it once more. 



Now it is precisely these symptoms which 

 marked the close of my captives' existence in the 

 tanks. In each instance, contrary to the usual beha- 

 vior of a dying fish, the sea-horse never floated 

 near the surface; it fell to the bottom before it 

 died. Therefore, in view of these facts, it should 

 appear that the hippocampids do not thrive in cap- 

 tivity because of some abnormal condition in their 

 newer habitat to which they cannot adjust them- 

 selves. What, then, can this condition be? But one 

 conclusion can be drawn: for, after having elim- 

 inated such considerations as insufficiencies of food 

 or of oxygen, and the matter of salinity and tem- 

 perature, a single factor remains — depth. And this 

 in other terms means nothing more than pressure. 

 Consequently, it is not hard to conceive of the sea- 

 horse as being one of the hungry horde whom com- 

 petition is gradually driving away from the shore 



[293] 



