( and ( ( ( the ( protective ( amniotic ( ( sac and ) fluid ) ) ) ) ( surrounding ( the embryo ) ) ) . ) )
(ROOT (FRAG (CC and) (NP (NP (DT the) (JJ protective) (NN amniotic) (NN sac) (CC and) (NN fluid)) (SBAR (S (VP (VBG surrounding) (NP (DT the) (NN embryo))))) (. .))))
and the protective amniotic sac and fluid surrounding the embryo.
(ROOT (S (NP (NP (DT The) (JJ amniotic) (NN sac)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBD was) (VP (VBG sitting) (PP (IN on) (NP (NP (NN top)) (PP (IN of) (NP (DT the) (JJ flat) (NN embryo))))))))) (, ,)) (VP (VBZ envelops) (NP (DT the) (NN embryo)) (SBAR (IN as) (S (NP (PRP it)) (VP (VBZ folds))))) (. .)))