184 Illinois State Laboratory of Natural History. 



of species and aa abundance of individuals might be expected. 

 In the river thej were very rare. In the deeper water of the 

 bay they were not as common as at its edges, among the wood 

 rafts and the barges. They were most common in the stagnant 

 water of the lakes. Such genera as Amoeba, Difflugia, Cen- 

 tropyxis, Actinosphaerium, Yorticella, and Euglena were 

 abundantly represented. In Lily Lake a species of Pyxicola 

 attracted attention from its abundance. It was noticed in the 

 alimentary canal of the singular Dero mentioned above. 



Two protozoans are especially deserving of mention here. 

 The elongated green Eiujlena viridis was always to be found 

 in water dipped up at any place in the bay. When the wind 

 blew toward the west shore for a number of hours together a 

 dense coherent green scum was observed to collect in the inlets 

 and mouths of sloughs, and under the microscope this was 

 found to consist largely of the contracted, spherical Euglenae. 

 When placed under the cover glass of the slide they soon be- 

 come active again. Fishes and other animals could, and prob- 

 ably do, at such times collect them in quantities for food. The 

 second protozoan is Arcella discoides^ which occurred in num- 

 bers with the Euglense. 



