203 



age reaches our plankton station, so that its fertilizing effect 

 upon the water has been operative for some time. The second 

 reason lies in the fact that large industrial plants with private 

 water supplies — such as the distilleries and cattle-feeding yards 

 connected therewith and the glucose factory — discharge im- 

 mense amounts of organic wastes directly into the river. As 

 many as thirty thousand head of cattle are often on hand at 

 one time in these feeding-yards, and the refuse from the feed- 

 ing-pens is flushed into the stream or piled at the river's edge 

 till a rising flood carries it away in huge floating islands. The 

 contributions from these sources at Peoria and Pekin are con- 

 siderable. The comminuted vegetable debris of the silt owes 

 its origin to this source in some degree, and it shares also in 

 producing a wave of bacterial development (Jordan, '00), of 

 putrefaction (Palmer, '97), and of the rapidly developing plank- 

 ton organisms whose crest lies between Peoria and Havana. 



The contributions of sewage from the smaller cities in the 

 drainage basin above Havana are relatively so small, so scat- 

 tered, and so mingled with tributary waters in many cases be- 

 fore they enter the river, that no localized effect upon the 

 plankton of the stream can be traced. 



The direct conveyance into drainage channels of so large 

 an amount of animal wastes as occurs in sewage diverts from 

 the soil and adds to the water an unusual, and, owing to the 

 narrow confines of our streams, a proportionately great, source 

 of fertility. In these particulars, together with its unusual ex- 

 tent of impounding backwaters, its low gradient, and its im- 

 mediate access to markets, the Illinois River offers a magnifi- 

 cent field for the development of a scientific aquiculture. 



CHEMICAL CONDITIONS AND PLANKTON PRODUCTION. 



A summary of the chemical conditions as related to the 

 production of plankton in the four localities, Illinois and Spoon 

 rivers and Quiver and Thompson's lakes, yields some evidence 

 of correlation, and also some points of difference which indi- 

 cate the operation of other factors than nutrition in determin- 

 ing the production of plankton. The following table — giving 



