Differentiation potencies of the young chick blastoderm as revealed by different manipulations

Abstract

ABSTRACT Transversely folded chick blastoderms of unincubated to primitive streak stages were used in two different experimental series to check the following: (a) The effect of local damage (right corner) on the embryo-forming potencies of the blastoderm.(b) The effect of the removal of the hypoblast on the stability of the embryo-forming potencies of the primitive streak stage blastoderm. The conclusions are: (a) Intact, transversely folded, primitive streak stage blastoderms put on the culture medium with their posterior half downwards are relatively stable and the embryo forms from their posterior side.(b) Younger blastoderms are less stable and reveal the inherent asymmetry of the blastoderm by the formation of left-side embryos.(c) Partial extirpation of the right corner in such blastoderms causes a remarkable local rise in the embryo-forming potencies of the right side in both age groups, but the rise is more pronounced in the unincubated group.(d) Removal of the hypoblast from a primitive streak stage blastoderm reduces its developmental potencies to the level of those of the unincubated stage.