CHAPTER XXI. 



THE FISHES OF THE DEEP SEA. 



The knowledge of the existence of deep-sea fishes is one 

 of the recent discoveries of ichthyology. It is only about 

 twenty years ago that, from the evidence afforded by the 

 anatomical structure of a few singular fishes obtained in the 

 North Atlantic, an opinion was expressed that these fishes 

 inhabited great depths of the ocean, and that their organisa- 

 tion was specially adapted for living under the physical 

 abyssal conditions. These fishes agreed in the character of 

 their connective tissue, which was so extremely weak as to 

 yield to, and to break under, the slightest pressure, so that the 

 greatest difficulty is experienced to preserve their body in 

 its continuity. Another singular circumstance was, that some 

 of the specimens were picked up floating on the surface of the 

 water, having met their deaths whilst engaged in swallowing 

 or digesting another fish not much inferior or even superior 

 in size to themselves. 



The first peculiarity was accounted for by the fact that, 

 if those fishes really inhabited the great depths supposed, 

 their removal from the enormous pressure under which 

 they lived would be accompanied by such an expansion of 

 gases within their tissues as to rupture them, and to cause 

 a separation of the parts which had been held together by the 

 pressure. The second circumstance was explained thus : — 

 A raptatorial fish organised to live at a depth of between 500 

 and 800 fathoms seizes another usually inhabiting a depth of 

 between 300 and 500 fathoms. In its struggles to escape. 



