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date: 22 February 2020

Marshall, Sheina Macalisterfree

  • Margaret Deacon

Marshall, Sheina Macalister (1896–1977), marine zoologist, was born at Stewart Hall, Rothesay, Isle of Bute, on 20 April 1896. She was the second of three daughters of John Nairn Marshall (b. 1860) and his wife, Jean Colville, née Binnie (b. 1861/2). John Nairn Marshall was a general practitioner in Rothesay and a keen amateur naturalist. He founded the Buteshire Natural History Society and encouraged his daughters' interest in the subject. Sheina Marshall, like her sisters, was educated by governesses up to the age of twelve or thirteen. She then went to Rothesay Academy, and St Margaret's School, Polmont, but her education was interrupted by attacks of rheumatic fever. Confined to bed for long periods, she read the works of Charles Darwin, and her father gave her books on geology and zoology; these determined her to become a zoologist. She entered Glasgow University in 1914, but the First World War led to a year's work (1915–16) for J. S. Macarthur, an uncle by marriage, making luminous clock-faces and instrument dials for the armed forces. Returning to university in 1916 she studied zoology, botany, and physiology and obtained a BSc with distinction in 1919. She held a university Carnegie fellowship from 1920 to 1922, working with John Graham Kerr, professor of zoology. He suggested she should take a job at the marine station at Millport on the Isle of Cumbrae in the Firth of Clyde. The laboratory, belonging to the Scottish Marine Biological Association, had just received a grant from the development fund enabling it to expand. Marshall joined the staff in 1922 and continued to work there for the rest of her life.

Following a suggestion from Kerr that she should investigate marine food chains Marshall began a seasonal study of plankton, looking in particular at the micro-organisms forming the food of Calanus finmarchicus, a copepod important in the diet of herring. The biology of copepods was to become her life's work. In this, and in the study of marine productivity, she was joined in an extremely fruitful collaboration (between 1923 and 1962) by the chemist Andrew Picken Orr. They began by looking at the relationship between physical and chemical changes and plankton distribution throughout the Clyde sea area, but the scale of the undertaking proved too large. Thus in 1926 they monitored seasonal changes in nutrients and phytoplankton in Loch Striven on a weekly basis, obtaining results since considered a 'landmark in the study of marine production' (Russell, 372).

Between 1928 and 1929 Sheina Marshall and Orr were members of the Great Barrier Reef expedition. Back at Millport, Marshall resumed her early interest in copepods as chief consumers of phytoplankton. She and Orr made an exhaustive study of the biology and physiology of Calanus, looking at aspects of its seasonal distribution, reproduction, and growth. Their joint book The Biology of a Marine Copepod appeared in 1957. Following Orr's death in 1962 Sheina Marshall worked closely with E. D. S. Corner, a biochemist from the Plymouth laboratory.

During the Second World War Marshall took part in the search of British coasts for seaweeds suitable as a source of agar, both on field surveys in the west of Scotland, and in laboratory work with Orr. She worked on methods of harvesting the selected species, Gigartina, and supervised collection by volunteers. From 1942 she also took part in a field study on the effect on marine productivity of the addition of artificial fertilizers in Loch Craiglin.

In the late 1960s the Millport laboratory moved to Dunstaffnage, near Oban, and the buildings were taken over by the University Marine Biological Station. Sheina Marshall decided to stay in Millport, and continued to work at the station in retirement. She spent 1970–71 at Scripps Institution of Oceanography in the USA and was a visiting worker at the Villefranche laboratory in 1974. In her final years when her eyesight deteriorated, making microscope work difficult, she began writing a history of the Scottish Marine Biological Association (published in 1987). She remained in vigorous health until an attack of pneumonia in 1975 undermined her constitution. She died at Lady Margaret Hospital, Millport, from a heart attack two years later, on 7 April 1977.

Marshall was elected a fellow of the Royal Society of Edinburgh in 1949 and was awarded its Neill prize. She became a fellow of the Royal Society in 1963, and was made an OBE in 1966. The University of Uppsala awarded her an honorary degree in 1977. She was a dedicated and hardworking scientist but also had many outside interests, including walking and foreign travel. She was a gifted needlewoman and enjoyed poetry and listening to music. She had a delightful personality, unassuming but shrewd, and with a keen but kindly sense of humour. She never married.


  • F. S. Russell, Memoirs FRS, 24 (1978), 369–89
  • M. Deacon, tape-recorded interview of Sheina Marshall, 9 Aug 1970
  • S. M. Marshall, An account of the marine station at Millport (1987)
  • E. L. Mills, Biological oceanography: an early history, 1870–1960 (1989)
  • b. cert. [J. Marshall]
  • m. cert. [J. C. Binnie]
  • d. cert.


  • University Marine Biological Station, Millport, Isle of Cumbrae, personal and scientific papers



  • photograph, 1923, University Marine Biological Station, Millport, Isle of Cumbrae, Marshall MSS; repro. in Mills, Biological oceanography
  • G. Outram & Co., Glasgow, photograph, 1963, RS; repro. in Memoirs FRS
  • photographs, repro. in Marshall, Account of the marine station
  • photographs, University Marine Biological Station, Millport, Isle of Cumbrae, Marshall MSS

Wealth at Death

£148,004.31: confirmation, 5 July 1977, CCI

Biographical Memoirs of Fellows of the Royal Society
private collection
Royal Society, London