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.