STUDIES ON BIOLOGY OF FRESHWATER MUSSELS. 211 



methods, and approaches the study of the crystalline style from 

 the physiological standpoint. In subsequent papers I hope to 

 present further studies along the lines of reactions to stimuli and 

 distribution. 



For the study of the smaller glacial lakes and their inhabitants 

 the region is especially favorable. Winona Lake has a maximum 

 length of two miles, and being of the kettle-hole type, is deep. 

 Its greatest depth is eighty feet. The bivalve population is 

 limited to a shelf about its margin. Three small creeks drain into 

 the lake. Their course follows the flat, marshy land between 

 moraines, and their volume is small and comparatively constant. 

 The Unionids have not extended up into the creeks. The lake 

 forms the upper limit of their distribution in the Winona drain- 

 age system. 



Eight species of mussels have been recorded from this lake : 

 Lampsilis lutcolus, Anodonta grandis, A. cdentula, Quadrula 

 rubiginosa, and Lampsilis subrostratus are common, the first two 

 being very abundant. Lampsilis glans, Micromya fabalis, and 

 Margaritana marginata are rare. I have found a single specimen 

 of a ninth species, Quadrula undulata. All these mussels are of 

 the " lake " type, as contrasted with " river " mussels. 



For most of the following experimental studies Lampsilis luteo- 

 lus and Anodonta grandis have been employed. For work during 

 the winter, and for comparison with the above mentioned lacus- 

 trine forms, mussels from White River were used. These in- 

 clude Quadrula hcros, 0. pustulosa, Lampsilis anodontoides, L. 

 ligamentimis, etc. They were collected from the east fork of 

 White River, near Shoals, Indiana, and from the west fork of 

 the same river near, Gosport, Indiana. 



2. CONSTANCY OF THE FEEDING ACTIVITY. 



In a previous paper I stated that the lake mussel continues 

 feeding at nearly all times, when under normal conditions (Allen, 

 '14). Virtually all the observations made since the publication 

 of that paper have been of a confirmatory nature. Rarely is a 

 freshly collected mussel found to be without food material in its 

 alimentary tract, often much of it wholly undigested. When 



