The temperature characteristics for frequency of pulsation in isolated cloacal ends of Holothuria tubulosa are µ = 20,400 from 10 to 20°, 8,000 from 20 to 30°. The critical temperatures 10°, 20°, 30° are related to thermal conditions in the environment.

In sea water with doubled NaCl content µ = 8,000 from 10 to 30°. This is consistent with the specific nature of the temperature characteristics.

The primary effect of increased NaCl is to alter the temperature characteristic curve. At low temperatures the frequency is increased, at higher temperatures diminished. The effect upon frequency is thus of less significance. It is pointed out that such relationships must be taken into account in analyzing the action of reagents upon organisms.

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