BIOLOGICAL BESULTS OP THE "ABGO" CBUISE. 183 



precision to our ideas, and in enabling us to dispense with 

 a good deal of circumlocution. He says if we apply the 

 term " Halobios " to the entire assemblage of living 

 organisms inhabiting the waters, we may divide these 

 into two primary groups, " Benthos," or those that 

 live on the ground at the bottom, and "Plankton,"! 

 or those that move free in the water. Benthos may be 

 divided conveniently into the " Littoral Benthos " and 

 the "Abyssal Benthos," terms which require no explana- 

 tion, and each of these again comprises " Sessile " and 

 " Vagile " forms. Then Plankton in this wide sense can 

 be divided into " Nekton," or those forms which can swim 

 actively, and " Plankton " in the more restricted sense, 

 comprising those that swim feebly or not at all, and so 

 are liable to be carried about by currents. This Plankton 

 again can be divided according as it belongs to fresh waters 

 or to the sea into " Limnoplankton " and "Haliplankton," 

 and the former of these assemblages may be sub-divided 

 into Autolimnetic, Zonolimnetic, and Bathylimnetic 

 groups, according as the organisms live on the surface, 

 at a certain definite depth, or in deep-water close to the 

 bottom. Then the Haliplankton may be divided into 

 " Oceanic " and " Neritic." The former is what we find 

 away from land in the open sea and may be conveniently 

 grouped under the five great oceanic basins, (1) Arctic, (2) 

 Atlantic, (3) Indian, (4) Pacific, and (5) Antarctic. The 

 Neritic Haliplankton is what we find round the coasts of 

 continents and islands, and it might be termed Littoral 

 Plankton. Then the Oceanic Plankton of the great ocean 

 basins may be further sub-divided into Pelagic, Zonary, 

 and Bathybic, according as the organisms are found on the 

 surface of the sea, at a particular depth or zone, or finally 

 only in deep-water near the bottom. Then further, the 



t A term introduced by Prof. V. Hensen, of Kiel, a few years ago. 



