ERIK ZEUTHEN AND OTTO SCHERBAUM 



100 n 



Plate i (b) 



100 tx 



P/flfe i (c) 



Plate i. (a) Untreated Tetrahymena cells from a log-phase culture; 



(b) after 9 hours of treatment with intermittent heat shocks; (c) 90 minutes 



after return to constant optimum temperature. 



156 



