Using the patency assay for antigonadotropic activity described in earlier papers, the tissues of the ovary are shown to be devoid of antigonadotropic activity, although earlier reports had identified the ovary as the source of the antigonadotropin released by virgin females that had retained their eggs. Using both the patency assay on whole follicles, and an interference microscopy assay on isolated follicle cells, the source of the antigonadotropin has been traced to four pairs of abdominal neurosecretory organs, one pair in each of segments II, III, IV, and V.