byn-expressing caudal visceral mesoderm cells appear at internal, mesoderm-typical positions in the tail region. They begin to express caudal visceral mesoderm markers and exhibit caudal visceral mesoderm behavior, begin migration, but since the trunk visceral muscle fibres are absent migration fails and they spread over the posterior midgut.

In spite of normal AMG and PMG invagination, neither anterior nor posterior midgut primordia shows any sign of extension towards each other, but remain as large mesenchymal cell masses immersed in yolk at the ends of the embryo. The cells of these primordia fail to arrange into an epithelium.

Embryos partially dorsalized, gastrulation normal but fail to differentiate a mesoderm.