The disappearance of the decidua capsularis and Reichert's membrane in the mouse.

Starting on the eleventh day the decidua capsularis and trophoblastic giant cell layer disappear from the ends of the conceptus towards the middle. The disappearance is complete antimesometrially on the eighteenth day, but lateral remnants are still present on the nineteenth day. New uterine lumen never intervenes between undegenerate decidua capsularis and the uterine stroma. Reichert's membrane is intact on the sixteenth day, but has ruptured on the seventeenth. It is suggested that its apparently earlier disappearance in histological material is an artefact reflecting the weakening that leads to its rupture.