PLANKTON 



The term plankton indicates a group of living aquatic 

 organisms which may be single-cell (protozoa and proto- 

 phyta) or multiple-cell (metazoa and metaphyta), all of very 

 small dimensions, of limited autonomy of movement and 

 therefore subject to the movement of the water. Widely 

 varying organisms make up plankton, from aquatic protozoa 

 {Foraminifera, Radiolaria, etc.) to many crustaceans among the 

 metazoa [Copepoda, Ostracoda, etc.) and Celenterata of all the 

 free forms, that is, those not fixed on the bottom (these too 

 of minute dimensions), and so on for every other biological 

 group as well as for all stages of their early development : 

 from the eggs of crustaceans and fish to the larval form of 

 the first and the young of the second ; including therefore 

 those groups which later pass on to form part of benthos 

 {Celenterata, Porifera, etc.) or necton (fish). 



Plankton also comprises many forms of vegetable life 

 which are controlled by the same rules as control the animal 

 world. This includes free algae, single-cell or multiple-cell, 

 of microscopic or slightly more than microscopic proportions. 



Not all seas are equally rich in plankton. Contrary to 

 what might be expected, the cold seas are extremely rich, 

 and because of this contain great quantities of fish. The 

 temperate seas, such as the Mediterranean, are the poorest 

 in plankton. In certain zones and environments of the warm 

 seas plankton may be present in great quantities. This is so 

 in the case of the Red Sea. 



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