As an embryo in the mobility of the cell to get a space in this space that the embryo called BLASTOCOEL and surrounding cells, called the gap that the appearance of the BLASTODERM embryo similar effects now twist.
The larval stage is the movement of cells in the embryo to get a gap to gap that BLASTOCOEL and the cells that surround the space BLASTODERM characteristics of the embryo now resembles the custard.