( ( The amastigotes ) ( ( are ( ( smaller , ) ( ( oval-shaped cells ) ( that ( ( ( have ( only ( a ( residual flagellum ) ) ) ) and ) ( lack motility ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS amastigotes)) (VP (VBP are) (NP (NP (JJR smaller)) (, ,) (NP (NP (JJ oval-shaped) (NNS cells)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBP have) (NP (RB only) (DT a) (JJ residual) (NN flagellum))) (CC and) (VP (VBP lack) (ADVP (RB motility))))))))) (. .)))
The amastigotes are smaller, oval-shaped cells that have only a residual flagellum and lack motility.
(ROOT (S (PP (IN In) (NP (NNS humans))) (, ,) (NP (DT the) (NN sperm) (NN cell)) (VP (VBZ is) (NP (NP (DT the) (JJ only) (NN cell)) (PP (IN with) (NP (DT the) (NN flagella) (NN structure))) (SBAR (WHNP (WDT that)) (S (VP (VBZ enables) (ADVP (RB motility))))))) (. .)))