blastula
Concise Oxford English Dictionary © 2008 Oxford University Press:
blastula /ˈblastjʊlə/
▶noun (pl. blastulae /-liː/ or blastulas) Embryology an animal embryo at the early stage of development when it is a hollow ball of cells.
– origin C19: mod. L., from Gk blastos ‘sprout’.
'blastula' also found in these Oxford entries:

