( ( Each ( normal ( mature sperm ) ) ) ( ( consists ( of ( ( ( ( a head ) ( that ( contains ( ( ( ( ( the ( man 's ) ) ( genetic material ) ) -- ) ( his DNA ) ) -- ) ) ) ) and ) ( ( a tail ) ( that ( ( ( lashes ( ( back and ) forth ) ) ( at ( great speed ) ) ) ( to ( ( ( ( propel ( the head ) ) forward ) ( at ( ( about ( four times ) ) ( its ( own length ) ) ) ) ) ( every second ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT Each) (JJ normal) (JJ mature) (NN sperm)) (VP (VBZ consists) (PP (IN of) (NP (NP (NP (DT a) (NN head)) (SBAR (WHNP (WDT that)) (S (VP (VBZ contains) (NP (NP (NP (DT the) (NN man) (POS 's)) (JJ genetic) (NN material)) (: --) (NP (PRP$ his) (NN DNA)) (: --)))))) (CC and) (NP (NP (DT a) (NN tail)) (SBAR (WHNP (WDT that)) (S (VP (VBZ lashes) (ADVP (RB back) (CC and) (RB forth)) (PP (IN at) (NP (JJ great) (NN speed))) (S (VP (TO to) (VP (VB propel) (NP (DT the) (NN head)) (ADVP (RB forward)) (PP (IN at) (NP (QP (RB about) (CD four) (NNS times)) (PRP$ its) (JJ own) (NN length))) (NP (DT every) (NN second)))))))))))) (. .)))
Each normal mature sperm consists of a  head that contains the man's genetic material -- his DNA -- and a tail that lashes back and forth at great speed to propel the head forward at about four times its own length every second.
(ROOT (S (NP (NP (DT The) (`` ``) (NN head) ('' '')) (PP (IN of) (NP (DT the) (NN sperm)))) (VP (VBZ contains) (NP (DT the) (JJ genetic) (NN material))) (. .)))