Ovariectomy during gestation in mammals usually results in abortion or death of the embryos. In some mammals, however, the embryos survive and can develop for a short time.
In ferrets, implantation occurs when ovariectomy is performed on Day 10 post coitum (p.c.) but resorption follows immediately (Buchanan, 1969). In the guinea-pig, implantation occurs if ovariectomy is performed more than 48 hr p.c. (Deanesly, 1960, 1966) but development continues normally only up to the 14th day. Ovariectomy of the nine-banded armadillo during delay results in precocious implantation (Buchanan, Enders & Talmage, 1956) which occurs 18 to 20 days after operation (Enders, 1966); embryonic and fetal development proceed normally (Enders & Buchanan, 1959). Marsupials, like armadillos, can dispense with their ovaries for the greater part of gestation. In the quokka, Setonix brachyurus, and the tammar, Macropus eugenii, the blastocysts