This is a long awaited update of a much loved text, first produced in 1976. Bentley has retained a very successful format considering structures, actions and physiological roles of hormones across the vertebrate series. The evolution and origins of hormones and their receptors is discussed in the context of their contribution to major body systems and the ecology and evolutionary development of key vertebrate groups. In this way the integrative functions of hormones are examined in major body systems including nutrition, reproduction, osmoregulation, calcium homeostasis and in relation to animal colouration, moulting and development. Species considered range from representatives of lower chordates through the major fish groups to tetrapods including mammals.