Erratum
In the reply by J. W. Holaday and B. H. Natelson to the technical comment entitled "Ultradian cortisol rhythms in monkeys: Synchronized or not synchronized?" (1 Dec. 1978, page 1001), the second sentence of the last paragraph should have read: "Tannenbaum and Martin (6) have reported a light-entrained, synchronized ultradian growth hormone rhythm in rats."