( ( ( ( The connection ) ( of ( the ( yolk sac ) ) ) ) ( to ( ( the embryo ) ( in ( amniotic vertebrates ) ) ) ) ) . )
(ROOT (NP (NP (DT The) (NN connection)) (PP (IN of) (NP (DT the) (NN yolk) (NN sac))) (PP (TO to) (NP (NP (DT the) (NN embryo)) (PP (IN in) (NP (JJ amniotic) (NNS vertebrates))))) (. .)))
The connection of the yolk sac to the embryo in amniotic vertebrates.
(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))))) (. .)))