Six adult lorises (Loris tardigradus lydekkerianus) in anoestrus were selected for study. Four of the animals were pretreated with an injection of 0·5 mg oestradiol-17β, two were given FSH (2 × 50 i.u. with a 12-hr interval), while the remaining two were not treated with hormones. All of the animals were subsequently given a subcutaneous injection of 0·5 mCi [3H]thymidine and their ovaries were recovered for autoradiography 24 hr later.
It was found that the non-follicular germinal cells within `nests' in the ovarian cortex actively incorporated the radioisotope. Some of the labelled germinal cells appeared to reach the pachytene-diplotene stages of meiotic prophase, although this would not be expected to occur in such a short time after treatment. None of the labelled germinal cells appeared to enter upon the phase of follicular growth, although a few (especially in ovaries treated with oestrogen and FSH) seemed to be in primordial follicles consisting of an incomplete layer of flattened cells.