( ( ( ( ( ( The nucleus ) ( is ( very dark ) ) ) , ) but ) ( ( the coma ) ( ( makes ( the head ) ) ( ( the ( brightest part ) ) ( of ( the comet ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT The) (NN nucleus)) (VP (VBZ is) (ADJP (RB very) (JJ dark)))) (, ,) (CC but) (S (NP (DT the) (NN coma)) (VP (VBZ makes) (NP (DT the) (NN head)) (NP (NP (DT the) (JJS brightest) (NN part)) (PP (IN of) (NP (DT the) (NN comet)))))) (. .)))
The nucleus is very dark, but the coma makes the head the brightest part of the comet.
(ROOT (S (NP (NP (DT The) (NN head)) (PP (IN of) (NP (DT the) (NN sperm)))) (VP (VBZ contains) (NP (DT the) (NN nucleus))) (. .)))
The head of the sperm contains the nucleus.