312 Illinois State Laboratory of Natural History. 



On the other hand, the Protozoa play an important part in 

 the food of other organisms. Many rotifers feed freely upon 

 them, and even young fishes have been found with Difflugia 

 in their stomachs. Euglena, Volvox, Pandorina, Difflugia, 

 and Codonella are among the forms observed in the stomachs 

 of rotifers ; but so few observations on this subject have been 

 recorded, that very little information can be gathered at 

 present. 



LOCAL DISTRIBUTION. 



In the waters from which our Station collections were made 

 the Protozoa were not so abundant nor so widely distributed 

 as the rotifers. In all, ninety-three species are recorded, one 

 of which (Difflugia fragosa) is here described for the first 

 time. Species which could not be identified with certainty 

 are not included in the list. 



The most widely distributed form was Difflugia globulosa, 

 which appeared at every substation and was present in 

 nearly every month of the year. Other species of Difflugia 

 and species of Arcella were found during a considerable part 

 of the year, including the summer months. Dinobryon 

 sertularia was very abundant, occurring from December to 

 June; Euglena viridis was observed throughout the summer 

 months ; Volvox globator was found in every month except 

 February; Coleps hirtus was present from May to October ; 

 and Codonella cratera was frequently seen from April to 

 September. All through the summer months many species 

 of Vorticella, Epistylis, and Opercularia were taken in thetow- 

 ings or upon the backs of turtles and the larger Crustacea, 

 but few of them could be definitely determined. 



A number of the species here recorded were found in 

 aquaria started with dried mud from the bed of Phelps Lake. 



I have found it very difficult to make a sharp distinction 

 between the littoral or shore forms, and the so-called pelagic 

 or limnetic forms found in the open waters. These waters 

 were so shallow— the average depth at the various substations 

 ranging from two to twelve feet— and so full of vegetation, 

 that the only species that seemed entitled to be considered as 



