Answer: gastrulas

AnswerCrossword Clue
gastrulasmetazoan embryo in an early state of germ layer formation following the blastula stage, consisting of a cuplike body of two layers of cells, the ectoderm and endoderm, enclosing a central cavity, or archenteron, that opens to the outside by the blastopore
gastrulasGASTRULA, a metazoan embryo