II THE PROBLEMS OF THE DEEP SEA 47 



he thinks, obey no such law. The Arctic and 

 Atlantic seas, he says, are as full of fishes and 

 other animals as those of the tropics. It is, there- 

 fore, clear that cold does not affect the dwellers 

 in the sea as it does land animals, and that this 

 must be the case follows from the fact that sea 

 water, "propter varias quas continet bituminis 

 spiritusque particulas," freezes with much more 

 difficulty than fresh water. On the other hand, 

 the heat of the Equatorial sun penetrates but a 

 short distance below the surface of the ocean. 

 Moreover, according to Zimmermann, the incessant 

 disturbance of the mass of the sea by winds and 

 tides, so mixes up the warm and the cold that 

 life is evenly diffused and abundant throughout 

 the ocean. 



In 1810, Risso, in his work on the Ichthyology 

 of Nice, laid the foundation of what has since been 

 termed " bathymetrical " distribution, or distribu- 

 tion in depth, by showing that regions of the sea 

 bottom of different depths could be distinguished 

 by the fishes which inhabit them. There was the 

 littoral region between tide marks with its sand- 

 eels, pipe fishes, and blennies : the seaweed region, 

 extending from lowwater-mark to a depth of 450 

 feet, with its wrasses, rays, and flat fish ; and the 

 deep-sea region, from 450 feet to 1500 feet or more, 

 with its file-fish, sharks, gurnards, cod, and sword- 

 fish. 



More than twenty years later, MM. Audouin and 



