( He ( ( ( ( ( ( ( injected ( one ( of ( ( two cells ) ( of ( a ( two-cell ( starfish embryo ) ) ) ) ) ) ) ) ( with antibodies ) ) ( to myosin ) ) , ) and ) ( ( allowed ( the embryo ) ) ( to ( develop ( to ( the ( blastula stage ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP He)) (VP (VP (VBD injected) (NP (NP (CD one)) (PP (IN of) (NP (NP (CD two) (NNS cells)) (PP (IN of) (NP (DT a) (JJ two-cell) (NN starfish) (NN embryo)))))) (PP (IN with) (NP (NNS antibodies))) (PP (TO to) (NP (NN myosin)))) (, ,) (CC and) (VP (VBD allowed) (NP (DT the) (NN embryo)) (S (VP (TO to) (VP (VB develop) (PP (TO to) (NP (DT the) (NN blastula) (NN stage)))))))) (. .)))
He injected one of two cells of a two-cell starfish embryo with antibodies  to myosin, and allowed the embryo to develop to the blastula stage.
(ROOT (S (NP (NP (NNS Invertebrates)) (-LRB- -LRB-) (CC and) (NP (JJR higher) (NNS animals)) (-RRB- -RRB-)) (VP (MD can) (ADVP (RB also)) (VP (VB be) (VP (VBN placed) (PP (IN in) (NP (NP (CD one)) (PP (IN of) (NP (CD two) (NNS groups))))) (PP (VBN based) (PP (IN on) (SBAR (WHADVP (WRB how)) (S (NP (PRP they)) (VP (VBP develop) (PP (IN as) (NP (NNS embryos))))))))))) (. .)))
Invertebrates (and higher animals) can also be placed in one of two groups based on how they develop as embryos.