原肠胚形成
Gastrulation \Gas`tru*la"tion\ (g[a^]s`tr[.u]*l[=a]"sh[u^]n), n. (Biol.) The process of invagination, in embryonic development, by which a gastrula is formed.
gastrulation n : the process in which a gastrula develops from a blastula by the inward migration of cells