PROF. DORIS L. MACKINNON, who retires from the chair of zoology as King's College, London, at the end of the present session, has held the post since 1927, when she succeeded Dr. Julian Huxley. She joined the staff of King's in 1919 when the late Prof, A Dendy was head of the Department, and endeared herself to generations of students by her professional competence and her sympathetic, wise and helpful guidance. Prof. Mackinnon has published many noteworthy papers on her work, which deals almost entirely with parasitic Protozoa (especially flagellates and Sporozoa). During the First World War she joined the team of workers engaged in the diagnosis of amœbic dysentery and intestinal protozoal infections for the War Office and Medical Research Committee (now Council). When she went to London after the War, she soon established a centre of research in protozoology--for years the only zoological (that is, non-medical) centre of the kind in Britain. By her teaching and research and the work of her pupils, she has thereby done much to advance the subject ; and her publications include many solid and permanent contributions to protozoology. As too frequently in academic appointments, the responsibility of administration tends to make inroads on time for research ; but Prof. Mackinnon kept up a constant flow of publication and gave intercollegiate lectures of characteristic lucidity and thoroughness. In paying tribute to her gifts as a teacher, it would not be out of place to mention the admirable series of broadcast talks on natural history given to schools. Her services on the University and College Boards and Faculties were particularly appreciated, as she brought to them a breadth of outlook, sound judgment, scrupulous thoroughness and an altruistic approach not invariably observed on such bodies. Fortunately her retirement does not mean that she will cease her zoological work, and her colleagues and friends will still be able to enjoy her urbane and delightful companionship.