300 



Aquatic Societies 



water are few. If we leave aside the chlorophyl- 

 bearing flagellates already mentioned (often considered 

 to be protozoa) the commoner forms among them are 

 such other flagellates as Mallomonas (see fig. 185 on 

 page 309), such sessile forms as Vorticella (fig. 179) 



FIG. 182. Plancton Cladocerans from Cayuga Lake, 

 larger, Acroperus harpa; the smaller, Chydorus sp. 



The 



and such shell-bearing forms as Arcella and Difflugia 

 (see fig. 69 on p. 159). 



The rotifers of the plancton are many. The most 

 strictly limnetic of these are little loricate forms such 

 as Anuraea and Notholca, two or three species of each 

 genus. When one looks at his catch through a micro- 

 scope nothing is commoner than to see these little thin- 



