Fig. 7. Summary of immunohistochemical analysis of implanted embryos. Each filled circle represents one implantation that induced ectopic Wt1 expression. Open circles represent implantations in which induction was not detectable. Different colors represent different implanted tissue. Gray filled circles represent implantations in which induced expression and endogenous proepicardium (PE) expression could not be distinguished because of their close proximity. Somite level and the distance between the midline and lateral edge of the dorsal aorta were used to determine anteroposterior and mediolateral levels of the implant. Quail-derived inducer tissues were implanted into stage 10^--12^- (left), stage 12-13^- (middle) or stage 13-14 (right) chick host embryos at different sites. Induction of Wt1 expression in host tissue was examined by double immunohistochemistry using anti-Wt1 and QCPN antibodies.