Fig. 6. Placentas of K18^–/–K19^–/– (–/–) and wild type (wt) mice 9.5 days post-coitum. (A and C) Placentas of wild-type mice. Note the well developed labyrinthian layer and the deeply invaded giant trophoblast cells (arrows). (B and D) Placentas of K18^–/–K19^–/– mice. Note the cleft between the trophoblast giant cells and the spongiotrophoblast (arrows in B) and the poorly developed labyrinth (arrow in D). Bar, 200 µm.