Abstract
E. affinis was tested for its ability to recover from short exposures to high temperature (temperature tolerance). Animals kept at a warm temperature for several hours or days before the test increased in tolerance (acclimation). Females showed higher tolerance and acclimation than males. Temperature tolerance was greater at a higher salinity (13.permill. vs. 0.permill.), but acclimation was not. Analogous tests were done at low temperatures. Acclimation to cold temperature occurred, but more slowly, and sex differences were less marked than for heat tolerance. When tested on the same animals, heat and cold tolerances seemed to be positively related traits.