504 



parts per million in the canal, and 8.8 parts in the Des Plaines. The 

 same was true March i8, when 6.3 parts of dissolved oxygen were 

 found in the canal and 6.5 in the Des Plaines. 



August and September, ipi2. — Additional biological collections 

 were made August 9 and September 30, 1912, with water tempera- 

 tures at 67° F. on the first date and 64° on the second. The stream 

 was rather low, with much vegetation, including water milfoil 

 (Myriophylluni), Blodea, pondweed (Potamogeton), etc., the first 

 two mainly on the west side. There was, in fact, a marked contrast 

 at this time between the two sides of the river, due to the fact that 

 the water of the east side was badly contaminated by a waste ditch 

 flow from the sanitary canal, and contained there the sewage organ- 

 isms noticed the preceding year. In the Cladophora of the west 

 side were many live minnows, sunfish, etc., with Spirogyra, Vauehe- 

 ria, duckweed, and epiphytic green alg?e. Here also among the Cla- 

 dophora, on the west shore, were numerous crustaceans — Cyclops, 

 SimocepJiahiS, and Ostracoda, together with Hyalella dentata and a 

 single specimen of Asellus. On the east side there was an abundance 

 of CarcJicsiuui on the stones, together with oligoch?ete worms (Tuhi- 

 fcx) under mats of OscUlotoria. Eristalis and Odonfomyia larvre 

 were taken in the contaminated water; and Corixa and Zaitha and 

 larvae of SimnUum and caddis-flies among Cladophora on the west 

 shore. The mollusks obtained were Lymncca humilis, Physa gryina, 

 and Planorbis parvus and trivolvis; the first on the east side and the 

 others common on the opposite shore. 



Des Plaines River at Dresden Heights 



The midsummer condition of the mingled waters of the sanitary 

 canal and of the Des Plaines at the mouth of the latter was shown 

 by observations made at Dresden Heights, in July and August, 191 1, 

 where typical septic organisms predominated. From July 26 to 

 August I this water had a grayish, sloppy appearance, with a mingled 

 fish and privy odor. Sticks and stones were everywhere hung with 

 tufts of two of the most abundant septic organisms, SphcvrofUus 

 natans and Carchesiutii lachw.auni. These were being continually 

 torn loose from their attachments and carried down stream, where 

 they appeared abundantly in the plankton; and silt and other sedi- 

 mentary matter was kept churned up in the current so that there 

 was scarcely any accumulated sludge on the broken stones and 

 boulders of the bottom and dam. The temperature of the surface 

 layer of the water July 28 was 68° F. No fish could be found here 



