Metalimnlon 



See Thermocline. 



Metamorphosis 



The change of an animal from one form to another in its 

 postembryonic development, e. g., larva of an insect to a 

 pupa. 



Metaxenia 



The differential effect of pollen from different varieties 

 on the development of the fruit. 



Metazoan 



An animal in the group Metazoa which includes all mul- 

 ticellular animals as opposed to the unicellular Protozoan 

 (q.v.). 



Meteorograph 



An apparatus for automatically recording simultaneously 

 two or more meteorological elements. 



Meteorology 



The study that deals with physical processes occurring in 

 the atmosphere such as precipitation, winds, and tempera- 

 ture. 



Methane 



CH 4 , often called marsh gas, an odorless, inflammable 

 gas, and explosive when mixed with air. Develops from de- 

 composing organic matter in marshes and in coal-mines. 



Micelle (Micella, Micell) 



A particle composed of complex molecules that forms the 

 units of structure in many organic substances such as cellu- 

 lose and starch. 



Microassociotion 



The abstract class or type of community in which similar 

 Microstands are grouped, e. g., microstands of certain kinds 



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