Between 1919 and 1922 he was a Fellow of New College, Oxford University, then moved to Cambridge University, where he accepted a Readership in Biochemistry at Trinity College and taught there until 1932. During his nine years at Cambridge, Haldane worked on enzymes and genetics, particularly the mathematical side of genetics. Haldane wrote many popular essays on science that were eventually collected and published in 1927 in a volume entitled "Possible Worlds".