Menstrual cycle characteristics and side of ovulation in the rhesus monkey

Menstrual cycle characteristics and side of ovulation were studied in the rhesus monkey in 183 cycles. Side of ovulation was consistently related to cycle length. In cycles with a preovulatory phase approximating 14 days in length, ovulation tended to occur in the ovary opposite to that which provided the ovulation in the previous cycle. With a long preovulatory phase, ovulation tended to occur at random either from the same or from the contralateral ovary. The suggestion is raised that the corpus luteum of the previous cycle provides sufficient residual local activity to designate which ovary will provide the follicle for ovulation in the subsequent cycle.