CHAPTER XIII 

 PLANKTON : ITS NATURE AND INVESTIGATION 



The animals and plants that live in the sea have been 

 divided, according to their habits and the regions they 

 inhabit, into the following three sets : — 



1. Benthos — those that live attached to or crawling over 



the sea-bottom. 



2. Nekton — Those that swim freely in the water. 



3. Plankton — those that float or drift in the water with 



little or no powers of independent locomotion. 



'x:-^ 



Surface of Sea 



J^sritic Oceanic 



7y/////y9d\Mero-p lankton Holo-plan kton 



-'y^'^ Zoo-plankton 



\%K and 



^/^iP\^ Phyto- plankton 



Epi-plankton 

 Meso-plankton 

 Bathy- plankton 



The term " Plankton " was introduced by Victor Hensen 

 in 1887, and was popularized by Ernst Haeckel a few years 

 later {Plankton-Studien, 1890), and classified under various 

 subdivisions such as Phyto- and Zoo-plankton, Neritic and 

 Oceanic, Macro- and Micro-plankton, Epi-, Meso- and Bathy- 

 plankton, and other convenient groups according to the 

 nature and habitat of the organisms (see Fig. 15). Holo- 



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