MUSSELS OF WINONA, PIKE, AND CENTER LAKES. 309 



In order to test the ability of the mussel to withstand these 

 bottom conditions we made three wire clam baskets. One we 

 lowered in twenty-five feet of water, another in thirty-five feet, 

 and the other in eighty-five feet. The basket in twenty-five 

 feet was placed on August fifth on a dark mud bottom. It 

 contained thirteen U. lutcolns and one A. gnindis. On the 

 tenth two of U. Intcolns, dark variety, were dead ; on the fif- 

 teenth one of U. luteolus, dark variety, was dead ; on the 

 seventeenth two of U. luteolus, dark variety, were dead and four 

 were missing. The basket in thirty-five feet was placed on a 

 sandy gray marl bottom on August ninth. It contained five U. 

 luteolus of the light variety and one of the dark, and one A. 

 edcntula. On the fifteenth one A. grandis and one U. rubigi- 

 nosus were added. On the twentieth one U. Inteolm of the dark 

 variety was dead ; on the twenty-fourth five U. luteolus and one 

 U, rubiginosus were found to have the gills badly choked with 

 sediment, while the Anodontas were missing. The eighty-five 

 feet basket was lowered on pure dark mud on the fifteenth of 

 August. It contained seven U. lutcolns of light and one of dark 

 variety, two A. edcntula and one A. grandis. On the twenty- 

 first one U. lutcolns of dark variety was dead ; on the twenty- 

 fourth seven U. luteolus and one A. graudis showed gills badly 

 choked with sediment, while the two A. edentula were in better 

 condition, showing very few patches of mud in their gills. 



This experiment, incomplete as it is, serves to show two im- 

 portant facts that the dark variety of U. luteolus resists the con- 

 ditions of the gray marl far better than those of the fine black 

 mud bottom, regardless of depth of water, for in the twenty- 

 five feet basket on dark mud in five days two specimens, and in 

 the eighty-five feet basket on dark mud in six days one speci- 

 men, were killed, while eleven days were required in the thirty- 

 five feet basket on gray marl to destroy a single specimen ; that 

 the dark variety of U. luteolus is least resistant to these bottom 

 conditions. It also indicates that the Anodontas, especially A. 

 edentula, resist better than any other kind experimented with. 



Naturally one should expect to find some difference in struc- 

 ture by which the mud is more thoroughly excluded in the more 

 resistant species than in those which suffer more severely. There 



