503 



organic contents being evidently in a far more advanced stage of 

 decomposition. The stream was very low, flowing, at a depth of six 

 inches to a foot, over stones and pebljles which were completely cov- 

 ered with a septic growth of Sf^Jicrrotilus and algcT, mainly blue-green 

 species. The water had a grayish look, and a filthy smell, which 

 may perhaps be best described as a mixture of fishy and privy odors. 

 The current was too swift to permit the deposit of much sediment; 

 and it was frequently dislodging and carrying away fragments of 

 the incrusting growth from the bottom. A comparison of the con- 

 tents of the stream with those of the sanitary canal beside it pointed 

 to the conclusion that the septic organisms of the upper Illinois were 

 at this time being derived mainly from the Des Plaines and not from 

 the canal, although the putrescible matter carried by the latter fur- 

 nished an abundant nourishment for their growth and multiplication 

 far down the course of the main river. The Des Plaines was a seed- 

 bed, in short, and the canal water the soil, for the culture of sewage 

 organisms in the Illinois. 



Our collections from the river at Lockport were made opposite 

 the Ninth Street Bridge, three miles and a half above the lower gates 

 of the canal. SpJi<Trotiliis nafaiis and Authophysa lecjctans were 

 very abundant, with Carchcsium lachinanni, Bpistylis plicatilis, Vor- 

 ticclla jiiicrostoiim, and Paranicciuni caudatum intermixed. Less dis- 

 tinctly septic forms were Oscillatoria liinosa and Stigcoclouium tcnue, 

 with some Ulothrix zonata. Among tangles of dirty Spharotihis 

 were found large numbers of Chironouuis larv?e, together with oli- 

 goch?ete and nematode worms. No fish were seen here in Septem- 

 ber, the water being evidently much too foul for even the most in- 

 different species. 



Noveuihcr, ipii. — November i, iQii, the stream was six to eight 

 inches deeper, and the water temperature was 57° F., but conditions 

 generally were not unlike those of September, except that the odor 

 was less offensive. No snails or higher crustaceans could be found, 

 although there were now great numbers of mosquito larvae in the 

 water. There were also many shiners (Nofropis atlicriiioides), 

 nearly all alive but mostly in a dying state, as if they had been car- 

 ried down by the current from above, and overpowered by the toxic 

 contents of the stream. 



The content of dissolved oxygen was higher in the Des Plaines 

 than in the sanitary canal — 22 per cent, of saturation in the canal 

 and 44 per cent, in the Des Plaines; and virtually the same rela- 

 tions were found again in November, 191 2. February 2, 191 2, on 

 the other hand, the oxygen was nearly the same in both waters — 9.3 



