Habituation of the Crayfish Escape Response during Release from Inhibition induced by Picrotoxin

IF the more posterior segments of the crayfish body are disturbed, it will often escape by darting backwards. This escape manoeuvre, in which the appendages are thrust forward and the tail is flexed, is mediated by two lateral giant axons which lie dorsolaterally in the nerve cord 1 . A most intriguing aspect of the reflex is its extreme lability; it invariably fails if an attempt is made to elicit it repeatedly (unpublished results of Krasne and Wood-small). It is this phenomenon, so reminiscent of habituation in higher forms, which concerns us here.