1. Pinealectomy is possible in chicken. 2. Pinealectomized cocks reveal earlier development of the comb and testes, with premature crow and more rapid growth, and give earlier evidence of sexual instinct. 3. Pinealectomized hens show premature development of the ovary and oviduct and lay eggs earlier than the controls. 4. Therefore, in the case of the pinealectomized hen, the period to reach sexual maturity is also shortened by far than in the case of the control.