Butler, James Bayley (1884–1964), biologist and academic, was born 8 April 1884 at Secundrabad, India, only son among four children of Col. James William Butler and Henrietta Butler (née Bayley). His father had been an administrator in the East India Company. On his family's return from India he was educated at St George's College, Weybridge, Surrey; Clongowes Wood College, Co. Kildare; and St Mary's College, Rathmines, Dublin. He attended the Catholic University of Ireland medical school and received both science (BA, 1905) and medical degrees (MB, 1909) from the RUI. As a student he had been appointed dissector in anatomy to Professor Ambrose Bermingham (1903). When UCD was established he became the first lecturer in botany (1909), assisting the professor of biology, George Sigerson (qv), whose work largely involved lecturing on botany and zoology to first-year medical students. When for statutory reasons the botany lectureship was made a professorship in 1911, Butler was still responsible for some zoology teaching, and on Sigerson's retirement he was appointed professor of zoology (1924), a position he held till his own retirement in 1956, except for his period of service in the first world war with the RAMC, to which he was appointed as a lieutenant in 1915. He retired after the war with the rank of major, when he was awarded an MBE for oustanding service.
His research interests were largely in applied biology. Between 1922 and 1932 he carried out research on Catenaria anguillulae, a parasite of the ova of the liver fluke. One of his students, J. J. C. Buckley, became professor of helminthology at the London School of Tropical Medicine. In later years Butler became interested in the control of wood-boring beetles and the fungus Merulius lacrymans (now Serpula lacrymans) which causes dry rot in timber. He became well known internationally and in Dublin he was involved with the development of Biotox, a company manufacturing insecticides and fungicides, as applied to building construction. During the reconstruction of UCD's Newman House he gave valuable advice on dealing with the problems of dry rot infestation. He was frequently involved as an expert witness both in Irish and in English courts. A particularly remarkable example of his outstanding skill as an applied scientist was the process for waterproofing maps of which he sold the patent to the US army during the second world war. Even more remarkable, and perhaps the most tangible and enduring monument to his life's achievement, is the home that he constructed virtually by the labour of his own hands (with some help from his students) over a period of thirty years at Baily, Howth, Co. Dublin. Built to his own design as a replica of a classical Roman villa, the Bayley Butler home, Glen Lion, overlooking the sea, with its roof garden, floral sundial, moondial, and many other natural features and ingenious artefacts of his own making, delighted countless visitors, including his students, over many years. It incorporated stone salvaged after the destruction of the Custom House and the Four Courts and also fragments from Butt Bridge, the Roman forum, and the baths of Caracalla.
One of his major contributions to UCD was his promotion of field studies, organising excursions to the Dublin mountains, Glendalough, and the Burren. He initiated the first UCD marine field station at the Coal Harbour, Dún Laoghaire, and later at Coliemore Harbour, Dalkey, where field trips were undertaken by students. In his earlier years picnics were held on Dalkey Island. The Coliemore Harbour building housing the laboratory was subsequently occupied by a rowing club.
He founded the Natural History Club, later the Biological Society of UCD, and in 1962 he presented a cup to be awarded annually for best student paper. This was subsequently renamed the Bayley Butler trophy. Outside UCD he was an active member of the RDS (council member from 1930; vice-president, 1954) and he aided in the RDS science and technical exhibitions of the 1930s. He was also council member and honorary vice-president of the Royal Zoological Society. In 1915 he was elected MRIA, serving for three terms on the council (1923–4, 1936–8, 1943–4), and also serving on the flora and fauna committee.
Although his academic publications were limited (he wrote only one botanical article), he had a legendary reputation as a teacher. The relationship between student and teacher was important to him and he regularly held parties at his home at 81 Ranelagh Road, and later at Glen Lion, where garden parties with snail, cockroach, and frog races were special features.
He married first (19 December 1906) Katherine McWeeney (d. 1926) of the literary McWeeney family; they had two daughters, Katherine Butler (qv), pilot, Sister of Charity, and teacher, and Beatrice, wife of Frederick E. Dixon (qv) and first woman to serve on an Irish jury. He married secondly (1944) Alice Dromgoole, medical social worker; they had no children. He died 21 February 1964. One of his own students, Carmel Frances Humphries (qv), who succeeded him as professor of zoology, wrote his obituary in the Irish Naturalists' Journal. He left a draft autobiography with his family, which was under consideration (2004) for publication.