ˈgastrələ noun
( plural gastrulas -ləz ; or gastru·lae -ˌlē, -ˌlī)
Etymology: New Latin, from gastr + Latin -ula (feminine diminutive suffix)
: an early metazoan embryo consisting of a hollow 2-layered cellular cup made up of an outer epiblast and an inner hypoblast that meet along the marginal line of a blastopore and jointly enclose the archenteron, forming typically by invagination of part of the blastula wall or in many yolk-filled eggs by overgrowth of cells formed about the animal pole and epiboly, and in eggs producing discoblastulas and in mammalian eggs being greatly modified in both organization and course of formation — see delamination , involution ; compare blastula , morula
• gas·tru·lar -lə(r) adjective