( ( The embryo ) ( ( develops ( in ( ( the fluid ) ( of ( ( an ( amniotic sac ) ) ( within ( the egg ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN embryo)) (VP (VBZ develops) (PP (IN in) (NP (NP (DT the) (NN fluid)) (PP (IN of) (NP (NP (DT an) (JJ amniotic) (NN sac)) (PP (IN within) (NP (DT the) (NN egg)))))))) (. .)))
The embryo develops in the fluid of an amniotic sac within the egg.
(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))))) (. .)))