There is a marked alternation of ovarian activity in _T. ornata_, one ovary being more active than its partner in a given season. The less active ovary is more active than its partner in the following season. For example, a specimen killed in July had four corpora lutea on the right ovary and two on the left and there were five enlarged follicles (of the medium size group), representing the next set of eggs to be ovulated, four on the left ovary and one on the right. Similar alternation of ovarian activity was observed, to a greater or lesser extent, in nearly all of the females examined. Many subadult females that were approaching their first breeding season (as evidenced by the presence of large ovarian follicles but no indication of former ovulation) had but one active ovary. This may account in part for the tendency of small, young females to lay clutches smaller than average. One ovary may become senile in old females before its partner does; this may explain the occasional absence or atrophy of one ovary in large females that I have examined. In all the specimens examined, it was evident that ovulation had occurred or would occur in two successive seasons. Senile or young females might, however, be expected to skip a laying season if only one ovary was functioning. After ovulation, the collapsed follicle assumes a cuplike shape and becomes a glandular corpus luteum (Pl. 20, Fig. 2). Corpora lutea are approximately eight millimeters in diameter and are easily discernible at least until the eggs are laid; they are somewhat less distinct after preservation. Corpora lutea undergo rapid involution following oviposition and, after two to three weeks, are little more than small puckerings on the ovarian epithelium. At this stage they are properly referred to as corpora albicantia and are discernible only after careful examination of the ovary under low magnification. Corpora albicantia remain on the ovary until April of the year following ovulation but disappear in May and are never present after the new set of eggs is ovulated. Ovaries of some subadults (that would have laid first in the season following capture) contained enlarged follicles and, but for their lack of corpora lutea and corpora albicantia, were indistinguishable from those of older, fully mature females. Altland (1951:605-610) gave a histological description of the corpus luteum of _Terrapene carolina_. Corpora lutea were glandular and filled with lipoidal material until the eggs were laid. Atresia of corpora lutea began when eggs were laid, was completed by mid-August, and was coincident with atresia of large follicles that did not undergo ovulation. Altland did not describe the gross external appearance of the corpus albicans.