68 



their sides. Several small bluegills, that were still alive, were picked up 

 stranded at the edge of the water. 



Nothing is known of the summer conditions of this lake. The 

 autumnal overturn in Eagle Lake (Winona) takes place the latter part 

 of November. It seemed possible that there might be a deficiency in 

 oxygen in the lower levels of the lake that was killing the fish as their 

 actions simulated those of fish suffering from dyspnea. 



An examination of the water for dissolved gases and carbonates 

 demonstrated that the lake is a hard water lake and that there was an 

 abundance of oxygen. (See table. 4cc. O. per liter. Temperature 6°C.) 

 The fall overturn had taken place but the water was only about half sat- 

 urated. It is barely possible that the first fish to die may have died 

 from dyspnea, although this is not likely on account of the shallowness 

 of the lake, the contour of its bottom, and its exposure to the wind. It is 

 certain that the fish that were dying in November were not suffering 

 from the lack of oxygen. 



TABLE OF TEMPERATURES AND DISSOLVED GASES. 



Air temperature 10°C. 



Secchi's disc reading .9 M. 



Gases expressed in co. per liter. Cb. is COj, as carbonate. 



The fish were examined very carefully for infections, sporozoan and 

 bacterial, but the tissues showed no lesions or postules. The anus, nares, 

 mouth, and gills were examined with especial care. There was no indica- 

 tion of gas disease. 



It has been suggested that the lake might have been dynamited. 

 There were no ruptured blood-vessels to indicate that the fish had suffered 

 from concussion. Moreover, the fish were dying during a period of more 

 than six weeks, a fact that would preclude their having been killed by a 

 single charge of explosive. 



The only prenomenon that could be associated with the death of the 

 fishes as a causal factor was a tremendous growth of blue gi-een alga 

 Oscillatoria prolifica (Grenville) Dumont. This alga occurred near 



