1. Chilling Talitrus causes a complete cessation of locomotor activity and a delay in the appearance of successive activity peaks following return to normal temperatures. Maximum delay occurs if chilling begins during inactivity and is about equal to the duration of the chill. At other times the delay is less than the duration of the chill.
2. It is postulated that an inhibitory factor is concerned in the control of the locomotor rhythm of Talitrus, and a model is proposed to describe its possible mode of action.