Heart rate response to egg rotation in the domestic fowl embryo

1. In eggs turned about 12 times daily, around the long axis of the egg and through about 180 degrees, significant increases in heart rate occurred during turning on the 15th and 17th, although not on the 16th, d of incubation. 2. On and after the 18th d heart rate increases were more marked and occurred both during and after turning. 3. When a single group of embryos was turned every day for the last 4 d of incubation there were significant increases in heart rate on the last 3 d: this repeated retesting had no effect on the response to turning.