Ultrastructural observations of delayed implantation in the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus.

Embryonic development in Japanese long-fingered bats proceeded very slowly during and after the delayed implantation period (mid-October to mid-December). The primitive amniotic cavity and endoderm were formed before implantation. At the preimplantation stage (before hibernation) the corpus luteum cells appeared active, but became less active at the implantation stage (in hibernation). Activity was again apparent at the early placentation stage (after arousal).