( ( Chameleon eyes ) ( ( ( ( feature ( a ( negative lens ) ) ) , ) ( meaning ( that ( ( the lens ) ( is concave ) ) ) ) ) . ) )
(ROOT (S (NP (NN Chameleon) (NNS eyes)) (VP (VBP feature) (NP (DT a) (JJ negative) (NN lens)) (, ,) (S (VP (VBG meaning) (SBAR (IN that) (S (NP (DT the) (NN lens)) (VP (VBZ is) (ADJP (JJ concave)))))))) (. .)))
Chameleon eyes feature a negative lens, meaning that the lens is concave.
(ROOT (S (NP (DT A) (JJ concave) (NN lens)) (VP (VBZ is) (NP (NP (JJR thicker)) (PP (IN at) (NP (DT the) (NNS edges)))) (SBAR (IN than) (S (NP (PRP it)) (VP (VBZ is) (PP (IN in) (NP (DT the) (NN middle))))))) (. .)))
A concave lens is thicker at the edges than it is in the middle.