499 



and flagellate Protozoa of the Chlaniydomonas type, still living and 

 in process of multiplication, — a fact easily understood, in view of 

 the recent origin of the water in the lake and its undisturbed flow 

 and relatively low temperature in the deep canal. 



The Des Plaines River at this point w^as heavily loaded with 

 sewage wastes derived partly from the sanitary canal, which sends 

 into it an overflow through the turbine waste ditch of the controlling 

 works, and at times also through the sluice and over the bear-trap 

 dam at the same point. This stream was heavily contaminated also, 

 in 191 1, by sewage from several suburbs of Chicago on the Des 

 Plaines above Lockport. As it was very low and the water spread 

 in a thin sheet over a rocky bottom, its temperature was much higher 

 than that of the canal, and septic organisms were at their maximum. 

 The most conspicuous of these was the well-known "fungo-bacte- 

 rium," Sphccrotiliis natans, a filamentous form which grows in long, 

 loose, hanging tufts and branches in septic and polluted waters. The 

 stony bottom of the Des Plaines between Lockport and Dresden 

 Heights was carpeted with this plant, and with it were associated 

 a considerable variety of Protozoa (Carchcsiuui lachmanni, Vorti- 

 ccUa luicrostouia, Bpistylis pJicatilis, Oikomonas tcrmo, Bodo saltans, 

 and Paraincciinn pittriiunii,) all characteristic foul-water species. 

 These were continually being torn loose by the swift current of the 

 lower Des Plaines and mixed with the free plankton, with which 

 they were carried far down the stream, feeding and multiplying as 

 they went, until a gradual purification of the water made it unfit 

 for their maintenance. 



The Illinois from Dresden Heights to Marseilles was, in July to 

 September, 191 1, an especially saprobic or septic section of the 

 river, this condition culminating at Morris, if we may judge by the 

 numbers of septic organisms in the plankton. The most abundant 

 of these were Splurrotiliis uataiis, detached filaments of which made 

 about 90 per cent, of the number of the plankton organisms in this 

 and the following section. These were most abundant at Dresden 

 Heights, and were much more so at Morris than at any point below. 

 Several of the larger species of saprobic bacteria, not essentially 

 different in food requirements from Sphccrotilus natans, were notably 

 abundant in this section: Bacterium rulgarc, SpiriUuni volutans, and 

 species of Streptococcus were common examples. The largest col- 

 lections of detached heads of the J'orticellidce [Carchesium lachmanni 

 and Bpistylis plicatilis) were made at Dresden Heights and Morris. 

 FlagellateJ colorless Protozoa which feed, upon bacteria, were also 

 extremelv abundant in this section. The largest numbers n^ Oiko- 



