( ( ( 18C ( Phyletic gradualism ) ) ( versus ( punctuated equilibrium ) ) ) . )
(ROOT (NP (NP (CD 18C) (JJ Phyletic) (NN gradualism)) (PP (IN versus) (NP (JJ punctuated) (NN equilibrium))) (. .)))
18C Phyletic gradualism versus punctuated equilibrium.
(ROOT (S (NP (NNP Darwin)) (VP (VBD believed) (PP (IN in) (NP (NN gradualism)))) (. .)))