title: Commentary on Nicholas Mrosovsky's letter.
authors.affiliation: Institute of Cell, Animal, and Population Biology, University of Edinburgh, Scotland, U.K.
authors.forename: D S
authors.initials: DS
authors.lastname: Saunders
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D003624:Darkness; D008027:Light; D010507:Periodicity; D017440:Photoperiod; D012107:Research Design