what should have formed 'around the yolk' formed in the yolk at cleavage?
At the pole containing less yolk, the ovum divides and subdivides, forming the blastoderm, which gradually spreads around the yolk and forms the embryo.
At the pole containing less yolk, the ovum divides and subdivides, forming the blastoderm, which gradually spreads around the yolk and forms the embryo.