296 Aquatic Societies 



hold it toward the light, 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 algae, such as Anabaena, fig. 179, 

 and a few flagellates, accumulate on the surface during 

 periods of calm, hot weather. Anabaena 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 mainly algae. 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 



