No abstract

TWO PLATES (TWELVE FIGURES)Since the early work ('00) of von Winiwarter describing postfetal ovogenesis in rabbit and man, several methods have been employed to test the validity of the concept.By selection of closely graded series of stages, numerous investigators httve introduced evidence of the postpartum formation of ova. These reports have been critically reviewed by Kingsbury ( '38). One of these, Arai ('20), after making extensive counts of the total number of ova present at different ages in rats, concluded that ovogenesis was a continuous process. Allen ( '231, using mouse ovaries produced evidence of the cyclic nature of the process, initiated by mitoses in the germinal epithelium. Bagg and Papanicolaou ( '24) were able to accelerate ovarian activity in guinea pigs by irradiation of the thyroid gland, and found ova, follicle cells, interstitial and lutein cells all were derived from the germinal epithelium. Allen and Creadick ('37) and Allen, Smith and Gardner ('37) by using colchicine in mice more clearly demonstrated mitosis in the germinal epithelium and found convincing evidence of cyclic proliferation of ova from the germinal epithelium, the peak appearing at estrus. Schmidt and Hoffman ( '41) using this technique demonstrated such activity in guinea pig ovaries, only part of which was thought to be concerned in ovogenesis.In another approach Long ('40) reported abundant growth of germinal epithelium in tissue cultures of bits of mouse ovaries. He further demonstrated the formation of ova and follicles from this cultured epithelium.Marx ('41) using rats' ovaries stimulated by injection of gonadotropic extracts, found no evidence of proliferation of ova from the germinal 'A preliminary report of this investigation appeared as an abstract read by title at the meet-