GLOSSARY 247 



Minimum, Law of the (Liebig). — ^This well-established 

 agricultural law is applicable also to the ocean. 

 A plant requires a certain number of food-stuffs 

 if it is to continue to live and grow, and each of 

 these food-substances must be present in a certain 

 proportion. If one of them be absent, the plant will 

 die ; if it be present in minimal proportion, the growth 

 will also be minimal. This will be the case no matter 

 how abundant the other food-stuffs may be. Thus 

 the growth of a plant is dependent on the amount 

 of the food-stuff which is presented to it in minimum 

 quantity. 



Mud-Line. — ^The depth at which fine mud forms on the 

 sea-floor ; along coasts facing the great oceans this 

 depth is about 100 fathoms. 



Nekton. — A term introduced by Haeckel to designate all 

 pelagic animals that are able to swim against currents 

 (c/. Plankton). 



Neritic. — Belonging to coastal waters and bays, as 

 opposed to " oceanic," found only in the open sea ; 

 the term was introduced by Haeckel, and is applied 

 to both plankton and benthos. See also Pelagic. 



Oceanic. — See Neritic. 



Pelagic (Greek " pelagos," the open sea). — A term 

 applied to deposits forming at abyssal depths of the 

 ocean at a great distance from land, and also to organ- 

 isms inhabiting the surface waters of the ocean far 

 from coasts. 



Photic Zone. — ^The surface waters down to the limit of 

 penetration of sunlight, i.e., 600 or 700 fathoms, 



Phytoplankton. — Plant plankton. See Plankton. 



Plankton. — A term introduced by Hensen and now used 



for all aquatic organisms passively carried along 



by currents (c/. Nekton). 



Salinity. — The amount of total dissolved solids in unit 

 volume of a liquid which holds salts and little or 

 nothing else in solution ; especially applicable to 



