Initiation and Control of Meiosis and Follicular Growth in Ovaries of the Mouse

14 days p. p.) were maintained in organ culture for periods ranging from 2 to 14 days. Histological sections of these gonads were compared with controls that were fixed immediately after removal from coeval animals. It was found that germ cells in fetal ovaries progress through meiotic prophase at the same rate in culture as they do in vivo, although the number of germ cells was reduced if the ovary was cultured through a critical period (days 14 8!).e.). The development of the granulosa, thecal and stromal cells was retarded such that the ovary was reduced in size and the oocytes became crowded together. The process of follicular growth was severely retarded in organ cultures devoid of gonadotrophic hormones. Neither FSH nor LH alone was capable of restoring the normal growth pro-