John Zachary Young, universally known as JZ, was born in Bristol on 18 March 1907 and died on 4 July 1997. The Zachary in his name was said to be of Cornish origin. His ancestor Thomas Young achieved fame through his modulus and through the Young–Helmholtz theory of colour vision. JZ was educated at Marlborough, which school also produced another notable scientist, student of and early collaborator with JZ, Peter Medawar. Having acquired an interest in zoology at school, JZ read zoology at Magdalen College, Oxford, and then obtained a scholarship to work at the Zoological Section in Naples. There he began to investigate the autonomic innervation of the gut of fish. While in Naples he rediscovered the giant axons of the squid but, unlike L. W. Williams in 1909, he immediately recognised their importance. His observations led to the fundamental studies on the generation of the membrane potential and conduction of the action potential of axons by Hodgkin and Huxley. During his time in Naples before the War, JZ began his lifelong interest in the brain and behaviour of cephalopods.