part of part of in taxon surrounds surrounds Eumetazoa acellular anatomical structure egg chorion The egg shell. Kimmel et al, 1995.[TAO] UBERON:0000920 chorion (egg) Wikipedia:Chorion_(egg) ZFA:0000329 A protective, noncellular membrane that surrounds the eggs of various animals including insects and fish [GO]. TAO:0000329 TGMA:0000681 FBbt:00000038 chorion chorion membrane vitelline membrane entire extraembryonic component