Temperature and Locomotion in Planaria

A consideration of the temperature characteristics or thermal increments for locomotion in Planaria shows that they agree essentially with those reported for certain activities of other animals (Crozier, and Glaser). A process with the lowest increment (micro = 7,000 to 8,000) assumes control of the locomotor rate at temperatures above 20-22 degrees ; that with the highest increment (micro = 18,000 to 22,000) controls below 13 degrees ; and one with an intermediate value (micro = 11,100) is in command at the intermediate temperatures (13-21 degrees ). Another reaction with increment micro = 14,600 may, under certain conditions (e.g. 2 weeks after feeding), control the series over the median range. Excepting the latter, these increments are typical of catalyzed oxidative reactions (Crozier 1924-25, b) so that when these are in control it may be assumed that respiration is the fundamental process determining the rate of locomotion. Feeding produces a modification of the increment throughout the median range of temperatures, up to 2 days afterward.