Abstract
SUMMARY: When mouse ova were grafted under the renal capsule, the proportion of mice showing evidence of implantation was the same for normal and hypophysectomized animals. The injection of oestradiol dipropionate into pregnant lactating mice, on the 5th day post partum, produced macroscopic evidence of uterine implantation 26 hr later. This was not seen until 28 hr after an injection of serum gonadotrophin. The physiological significance of these findings is discussed.