LOTIC 

 DCIETIES 



CCORDING to the 

 grouping outlined on 

 page 315, we designate 

 by this name those as- 

 semblages of organisms 

 that are fitted for life 

 in rapidly moving water 

 — that are washed by 

 currents, as the name 

 signifies. Whether the 

 water flow steadily in 

 one direction as in 

 streams, or back and 

 forth with frequent shifts of direction as on wave- 

 washed shores, the organisms present in it will be much 

 the same sorts. The plants will be mainly such algae 

 as Cladophora, and slime-coat diatoms: the animals 

 will be mainly net-spinning caddis-worms and a variety 

 of more or less limpet-shaped invertebrates. 



The animals of lotic societies are mainly small inver- 

 tebrates. There are fishes, indeed, like the darters that 

 live in the beds of rapid streams. These lie on the 

 bottom where the current slackens, lightly poised on 

 their large pectoral fins, or rest in the lee of stones, 

 darting from one shelter to another. It is only a few 



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