THE INFLUENCE OF SURFACE EVAPORATION. I 19 



CONCLUSIONS. 



1. That whereas, under ordinary circumstances, infusoria tend 

 to collect near the center of a film under a cover-glass, when 

 methyl alcohol, ethyl alcohol, ethyl acetate, CaCl.,, KOH or 

 NaOH are added in sufficient concentration to the culture- 

 medium, this tendency is reversed and the organisms now gather 

 at the edges of the film. 



2. That this lends support to Jensen's explanation of the nor- 

 mal tendency of the infusoria to gather near the center of the 

 film, namely, that it is a special case of osmotaxis brought about 

 by surface- evaporation. 



