tropism, n., the turning of all or part of an organism in a particular direction in response to an external stimulus.
lacuna, n., unfilled space or interval; a gap.
skerries, pl. n., rocky islands.
portmanteau, n., 1. A large trunk or suitcase, usually made of leather that opens into equal parts. 2. A word blending sounds and meaning of two others, e.g., motel (motor hotel) or brunch (breakfast and lunch).
ontogeny, n., a branch of biology that studies the development of an organism or anatomical or behavioral feature from its earliest stage to maturity.
Thank you, writers and editors of WSJ.