AbstractTactile and proprioceptive stimulation designed to approximate natural sources of stimulation was administered to chick embryos from the 5th to the 16th day of incubation in the first 3 of 5 separate experiments. Such stimulation produced few modifications in the frequency, periodicity or qualitative aspects of embryos' movements at any age. In experiment IV, stimulation, considered to be atypical with regard to the frequency and intensity of administration, was found to modify the periodic but not the frequency aspects of embryonic behavior on Day 10 of incubation. The final experiment (V) provided partial support for the hypothesis that the general lack of effect of tactile‐proprioceptive stimulation in undisturbed chick embryos is due to a rather rapid cessation of responding. It was concluded that these 5 experiments support the contention that spontaneous activity is an important aspect of the normal embryonic behavior of the chic