113] FAUNA OF BJG VERMIUON RIVER— BAKER 15 



GENERAL BIOLOGY OF THE BIG VERMILION RIVER 



Although the chief purpose of the study of this stream was to ascertain 

 the general conditions and distribution of the fresh water MoUusca, 

 especially the Naiades or river mussels, such attention was given to other 

 groups as came easily under observation. At least one of these groups 

 bears an intimate relation to the Naiades in the matter of distribution 

 as restricted by pollution, e.g., the crayfishes, and another, the fish, is 

 closely related to the breeding habits of the mussels. Others, as some of 

 the oligochaete worms, are especially characteristic of polluted waters. 

 A few notes are given under each group. 



The Protozoa and other microscopic groups are omitted because given 

 little or no attention, except in the polluted part of Salt Fork. These 

 are mentioned in the section on sewage pollution. The Big Vermilion and 

 its tributaries present a wide field for the study of other kinds of aquatic 

 life that are especially characteristic of the upper reaches of a river system 



PLANTS 



The larger aquatic plants were notably scarce in most parts of the 

 Salt Fork. In several places in Salt Fork, especially near Sidney, between 

 the cement and railroad bridges, the shores are lined with the spatterdock, 

 Nymphaea advena Ait (see Fig. 11). The cat-tail, Typha latifolia, Linn., 

 is common in various stretches of the stream, bordering the shore. The 

 arrow-head, Sagittaria latifolia Willd., and the larger blue flag. Iris versi- 

 color, Linn., were observed along the shore in many places. The water 

 willow, Dianthera americana Linn., is abundant in the shallows in many 

 parts of the Salt Fork below Homer Park. Elodea canadensis Michx., 

 was abundant at Homer Park. 



Filamentous algae occurs in many places, attached to submerged 

 objects. Among these Cladophora and Spirogyra were noted. Septic 

 algae growing in the polluted portion of Salt Fork are noted under the 

 section on pollution of the stream. 



WORMS 



Nematoda. Gordius robustus Leidy, was collected in several places in 

 Salt Fork between the first bridge below St. Joseph and the bridge above 

 Sidney. It was found in mud bordering the shore, in shallow water. A 

 number of minute nematodes were observed in the sludges of the bottom 

 in Salt Fork between Urbana and St. Joseph. These were not identified. 



