Ovarian follicles during the normal process of growth and maturation are accommodated spatially by structural rearrangements within the ovary. When follicular growth is artificially induced by gonadotrophic hormones, several of the processes involved in follicular maturation, such as an increase in ovarian vascularity and the rapid growth and multiplication of follicles, are accelerated or intensified. When ovulation does not take place, cystic follicles are formed. This intense proliferation and growth of the parenchymatous elements of the ovary may be directly related to events occurring in surrounding structures, and in particular in the ground substance (with basement membranes) of the connective tissue. From a study of fibrous elements of the ovary, Duke [1947] proposed that the connective tissue may arise in response to, or be accompanied by, alterations of the parenchyma both in developmental and cyclic stages. Recent studies of the ground substance and basement membranes of a variety of normal