Feline ovarian histology at each 6 different times after hCG injection for superovulation. Ovaries were collected from less 1 year old female cats after superovulation with PMSG and hCG with 80 hrs apart and stained with hematoxylin and eosin. All ovaries have Graafian follicles (↓) and some ovaries have corpus lutea (★) presumed to be formed in the previous estrous cycle. Differentiated cells of granulosa, theca interna, and externa were shown in all Graafian follicles. In the ovaries at hCG 26 hrs (d’’), many of arrested follicles surrounded with luteal cells (★) were shown.