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tions show that the mussels of the plankton-rich lakes and ponds 

 usually contain more food material than those of the rivers. The cur- 

 rent gives the river-mussels the advantage of a constant change of 

 water, which means a more abundant supply of oxygen, and doubtless 

 a more varied supply of mineral matter, from the various sorts of 

 soil through which the river flows. The current is also probably of con- 

 siderable importance in assisting in the fertilization of mussels, one of 

 its results being the conveyance of sperm from mussels in upper portions 

 of the bed to other mussels below. In places where there is no current, 

 fertilization must be more largely a matter of chance. 



Although the majority of species of mussels prefer a river where 

 there is a good current, some are more fitted to the quieter parts of 

 streams, or to ponds. These are chiefly thin-shelled species with weakly 

 developed or undeveloped hinge-teeth, best represented by the genus 

 Anodonta. In some places Anodontas are known as pond-mussels, to 

 distinguish them from the heavier sorts, or river-mussels. 



The distinction between lakes and rivers is not constant in degree; 

 we have all sorts of gradations from the extreme form of lakes — 

 isolated bodies without outlet — through lakes with relatively large, im- 

 portant outlets, to such lakes as are simply expansions of a river-bed, 

 examples of the latter type being Lake Pepin, Minn., of the upper Mis- 

 sissippi, and the former English Lake in Indiana, an expansion of the 

 Kankakee. As a usual thing, the more fluvatile a lake is, or the larger 

 and more river-like its outlet, the more river-like will be its mussel 

 fauna, both in abundance and species. In such lakes the mussels retain 

 a vital continuity with the mussel beds of the river. In the less 

 fluvatile lakes the mussels are more isolated, and there is more in- 

 breeding. The large number (24) of lake-dwelling species recorded 

 for Indiana is due to the fact that some of the lakes of Indiana are 

 more or less fluvatile, and contain several species of river shells. 



Origin and Character of the Maxinkuckee Mussels. 

 Lake Maxinkuckee, having a long, narrow, and relatively unim- 

 portant outlet, is a representative of one of the less fluvatile types of 

 lakes, forming a pretty well marked contrast to the various lakes cited 

 above, and bearing a pretty close resemblance to the neighboring lakes, 

 such as Twin Lakes, Pretty Lake, Bass Lake, etc. 



