113] FAUNA OF BIG VERMILION 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 Mollusca, 
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 /atifolia, 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. 
