Effects of temperature of poikilotherms may be different at two time periods after alteration of the temperature: (1) the short-term effects which are manifested within minutes or hours of exposure, and
( 2 ) the long-term effects occurring after days of exposure during which various compensatory adjustments take place in the organism.
The oxygen consumption of most fish acclimated to high temperatures is higher than that of fish acclimated to lower temperatures when measured at the temperature of acclimation (Precht et al., '55; Bullock, '55), but at a given intermediate temperature, the cold-acclimated fish have a higher oxygen consumption than the warm-acclimated fish (Fundulus, Wells, '35; goldfish, Fry and Hart, '48).
Fry and Hart ('48) reported that the standard metabolism of goldfish, Carassius auratus, when measured at their tempera- tures of acclimation increased with the temperature of acclimation up to 30"C, the rise being steeper at lower temperatures. The active metabolic rate in relation to temperature does not necessarily follow a course parallel to the standard metabolic rate in fish (Fry, '57). The standard metabolism of goldfish increased with acclimation temperature up to 35"C, while active metabolism reached an optimum at 25"C, and declined steeply beyond it (Fry and Hart, '48).
This paper deals with the measurements at various temperatures of the standard and active oxygen consumptions of goldfish acclimated to 10" and 30ยฐC; that is, shortterm effects of temperature alteration were studied after long-term acclimation.