in the Fish Gallery of the Indian Museum. 39 



50 Fahr. : at 2000 fathoms there can be no doubt about 

 the absolute darkness, and the temperature, in these 

 seas, is constant at less than 2° above freezing-point. 



As a result of the absence of sunlight, plants (except 

 perhaps microbes) do not exist. 



Again the barometric pressure at the bottom of the 

 sea is something enormous : at 200 fathoms it must be 

 over 500 lb. on the square inch, at 2000 fathoms it must 

 be considerably over 2 tons on the square inch. 



The effects of the pressure can only be inferred. 

 Deep-sea fishes when brought to the surface by the 

 dredge and released from the accustomed pressure, 

 are — only in a very highly intensified degree — somewhat 

 in the condition of a man who has been carried into the 

 uppermost regions of the atmosphere by a balloon. 

 They are dead : their bodies are distended and ruptured 

 by the expansion of their gases and by the extravasa- 

 tion of their fluids, and their eyes are blown out of their 



sockets. 



The ultimate effects of the darkness are as curious as 

 varied. Some deep-sea fishes are quite blind, their eyes 

 beino- hidden rudiments : Tauredophidium hextii shows 

 this. In others, the eyes are rudimentary and some of 

 the fin-rays have become long organs of touch — a com- 

 pensation on the principle of the blind-man's stick : 

 Bathypterois Giuitheri is a good instance. Others have 

 evolved their own means of illumination, and possess 

 organs that— like the luminous glands of fire-flies— 

 secrete a fatty substance that burns slowly with a cold 

 phosphorescent light : these have their eyes well deve- 

 loped, and several examples of them are shown in 

 Cases 15-18 in which a series of typical deep-sea fishes 

 are exhibited. 



Ravenous as most fishes are, deep-sea fishes surpass 



