88 ILLINOIS STATE ACADEMY OF SCIENCE 



For the purpose of this particular discussion, the 

 changes in the physical and chemical factors within a 

 dying lake have particular importance biologically. The 

 student of physiology dealing with plankton, filamentous 

 algae, higher plants, higher animals, and the bacteriolo- 

 gical organisms inhabiting the waters of a lake which is 

 gradually disappearing, has an extremely mixed culture, 

 containing many varieties of organisms, all of them un- 

 dergoing seasonal and periodic change in number of any 

 one form and in the proportional numbers among all 

 forms. This great natural culture solution affords an 

 opportunity for studying permeability, osmotic pressure, 

 and the limits of adaptability of the organisms as well as 

 a study of their reactions upon the medium Avithin which 

 they are contained. An illustration of these points may 

 be had in the reaction of every organism which can live in 

 the waters of a gradually dying lake whose salinity is 

 continually advancing. The reactions of the organisms 

 which survive afford some explanation perhaps for the 

 absence of organisms which cannot survive. Professor 

 Oltmanns made some veiy interesting studies of the va- 

 rious factors involved when he undertook to transfer cer- 

 tain green algae to water of higher salt concentration. 



He says : ' '■ Spirogyra and Chara withstand a salt con- 

 centration of 0.5%. However, they are unable to with- 

 stand a 1% concentration because they cannot take in 

 sufficient salts to raise temporarily the osmotic pressure 

 of their cell sap. In other words, they are unable to 

 bring about proper osmotic alterations rapidly enough 

 to adapt themselves to the saline habitat. ' ' 



Prior to 1889 the waters of Devils Lake has been popu- 

 lated with vast numbers of great northern pike. Authen- 

 tic reports state that these fish were taken out in carload 

 lots by those who speared them through the ice. For 

 some reasons unknown to the layman, these food fishes 

 which appeared in actual shoals during the years pre- 

 ceding 1889, suddenly vanished. 



The three prevailing explanations of the pseudo-scient- 

 ists were that the water had become poisonous, that in- 

 sufficient food was present, and that some disease had 

 caused the fish to die. While any of these might have 



