296 Aquatic Societies 



hold it toward the hght, he will see it diffuse through 

 the water, imparting a dilution of its own color; and in 

 the midst of the flocculence, he will see numbers of 

 minute animals swimming actively about. Little can 

 be seen in this way, however. But if he will examine a 

 drop of the stuff" from the net bottom under the micro- 

 scope, almost a new world of life will then stand 

 revealed. 



It is a world of little things ; most of them too small 

 to be seen unless magnified; most of them so trans- 

 parent that they escape the unaided eye. Here are both 

 plants and animals; producers and consumers; plants 

 with chlorophyl, and plants that lack it; also, parasites 

 and scavengers. And it is all adrift in the open waters 

 of the lake. 



Tho plancton-organisms are so transparent and 

 individually so small, they sometimes accumulate in 

 masses upon the surface of the water and thus become 

 conspicuous as "water bloom." A number of the 

 filamentous blue-green alg^, such as Anabaena, fig. 179, 

 and a few flagellates, accumulate on the surface during 

 periods of calm, hot weather. Anabsena rises in August 

 in Cayuga Lake, and Euglena rises in June in the back- 

 waters adjacent to the Lake (see fig. i , on page 15). 



The plants of the plancton are itiainly algse. Bacteria 

 and parasitic fungi are ever present, though of little 

 quantitative importance. They are, of course, import- 

 ant to the sanitarian. Of the higher plants there are 

 none fitted for life in the open water ; but such of their 

 products as spores and pollen grains occur adventi- 

 tiously in the plancton. It is the simply organized 

 algae that are best able to meet the conditions of open- 

 water life. These constitute the producing class. 

 These build up living substance from the raw materials 

 offered by the inorganic world, and on these the life of 



