( ( 8 ( ( ( weeks of ) development ) -RRB- ) ) . )
(ROOT (NP (NP (NP (CD 8)) (SBAR (S (NP (NP (NNS weeks)) (PP (IN of)) (NP (NN development)) (-RRB- -RRB-))))) (. .)))
8 weeks of development).
(ROOT (S (PP (IN By) (NP (CD 8) (NNS weeks))) (, ,) (NP (DT all) (JJ major) (NNS organs)) (VP (VBP start) (S (VP (VBG developing)))) (. .)))