Later in development the yolk syncytial layer will be important in directing cell movements of gastrulation. The second cell population is the enveloping layer which is made of superficial cells from the blastoderm that eventually form a single epithelial cell layer.[1] This layer functions in protection by allowing the embryo to develop in a hypotonic solution so the cell will not burst.[5] Finally, the third set of blastomeres are the deep cells.