The Einsteck-method: position and structure of projections formed by implants of a ventral character

The behavior of colored beads and of various living tissues after implantation into the Xenopus blastocoel is investigated. It is confirmed that the location of a graft along the anteroposterior axis depends on its intrinsic anteroposterior character. Comparison with the behavior of the beads suggests that the final position can be achieved by movement of the graft around the dorsoventral circumference of the inner marginal zone during gastrulation. Ventral marginal explants, or animal caps treated with fibroblast growth factor, both form ventral vesicles if cultured in isolation, but in the implantation experiments they often yield projections containing segmented muscle blocks. This behavior does not occur when the axis of the host has been suppressed by ultraviolet irradiation and so it is concluded that it represents dorsalization of the graft by the host. The tail-like structures formed as a result of ventral-type tissue implantations do not contain neural tissue, while the mesodermal parts are typically of mixed graft and host origin.