What do dissociated embryonic cells of the starfish, Asterina pectinifera, do to reconstruct bipinnaria larvae?

The cellular events that take place during reconstruction of larval forms from dissociated embryonic cells of the starfish are investigated by thick and thin sections. Dissociated cells reaggregate, form an external epithelium (ectoderm), internal epithelial vesicles (endoderm), the blastocoel and the mesenchyme. The internal vesicles continue to fuse until there is only one large one suspended in the centre of the blastocoel. Eventually, the ectoderm invaginates at one or more sites and fuses with the endoderm to form blastopore(s). Special emphasis is placed on the differences in cell behaviour during endoderm-to-endoderm and endoderm-to-ectoderm fusion.