80 ILUNOIS BIOLOGICAL MONOGRAPHS (178 



RECENT EXAMINATION OF THE POLLUTED PORTION OF SALT FORK 



Figures 21, 36 to 45 



During the fall, winter, and spring of 1919 and 1920 Salt Fork was 

 carefully examined from Urbana to St, Joseph. All parts of the stream 

 were searched for macroscopic life and samples of the bottom and of the 

 water were taken for microscopic study, to determine the character and 

 abundance of the foul-water organisms present. Examinations were made 

 during the months of May, September, October, November, and December. 



During the spring months the water is so high in the stream that collec- 

 tions can not be made and examination of the water is difficult. The 

 great volume of water, laden with both sewage and silt, is of a dark lead 

 color and polluted conditions are not apparent, although some putrescent 

 matter was observed on several occasions. In the fall months conditions 

 are much more favorable for critical examination, the water being so low 

 that one may wade over any part of the stream. It is at this time, which 

 extends from July through the fall and winter to the rainy period in March 

 or April, that the polluted conditions are very apparent and the most 

 satisfactory studies can be made. The general conditions of the stream at 

 this period are summarized below. 



The water in the Boneyard near the Big Four shops, below the Urbana 

 sewage outlet is usually shallow, from a foot or less to two feet in places. 

 The bottom is a mass of sludge with putrescent material covering all 

 objects in the water and floating down the stream, which has an estimated 

 flow of about half a mOe an hour. Several large sludge banks are exposed 

 and the odor is usually nauseating (Fig. 39). At the junction of the 

 Boneyard with the Salt Fork the water varies from six inches to a foot 

 in depth, there are several sludge banks and the putrescent matter covers 

 all objects and lines the shores to a height of several feet, indicating former 

 high water marks (Fig. 36). Samples of the sludge and green putrescent 

 material from one of these sludge banks were examined by Professors 

 Smith and Transeau and the following algae, Protozoa and other animals 

 observed: 



Blue-green algae Animals 



Pediastrum simplex, common. Paramoecium, not common. 



Senedestnus abundans, rare. Euglena geniculata, very abundant. 



Phormidium inundatum, abimdant Limnodrilus (sludge worm) , very abiin- 



Diatoms danL 



Namcula cryptocephala, common. Tubifex (sludge worm), one specimen. 



Synedea pulchella, not common. Nematode worms, several. 



Ciliate Protozoa were numerous, including Colpodium and a few 

 hypotrichous and peritrichous species. 



