Abstract
Summary. A single intraperitoneal injection of female mice with rabbit antisera against denuded mouse eggs and isolated zonae pellucidae inhibited fertilization for at least 25–30 days. Intraperitoneal injection appeared to be more effective and lasted longer than subcutaneous or intramuscular injection but oral administration had no effect. Such a passive immunization of females given after fertilization had no effect on embryonic development or the sex ratio of fetuses. The fertilizing capacity of mouse spermatozoa was suppressed by treatment of the sperm suspension with anti-egg but not with anti-zona serum. Treatment of mouse eggs with these antisera did not affect their development to blastocysts in culture but did inhibit the shedding of the zona pellucida and attachment to the dish.