108 ILLINOIS BIOLOGICAL MONOGRAPHS [206 
EXPLANATION OF PLATE 
Fic. 12. Salt Fork three and a half miles above Homer Park, Station 23. October 4, 
1918. 
Fic. 13. Salt Fork. Deep pool below dam and rapids. Professor Smith’s field laboratory 
during a period of twenty years. Station 25. November 4, 1920. 
