Thompson, John Vaughan (1779–1847), army surgeon and zoologist, was born 19 November 1779 in Berwick-upon-Tweed, England, son of John Thompson and his wife Jane (née Hall). He studied medicine and surgery in Edinburgh (1797–8), and in March 1799 was appointed assistant surgeon to the Prince of Wales's Fencible Regiment, a regiment raised by Sir William Johnston in 1798. In 1799 he transferred to the 37th Foot and served in Gibraltar and later in the West Indies and Guiana. He was present at the storming of Demerara and Berbice, and in June 1803 was promoted to surgeon.
Throughout his military service he occupied his spare time in botanical and zoological studies. Returning to England in 1807 on a period of leave, he published Catalogue of plants growing in the vicinity of Berwick-upon-Tweed and was elected as an associate of the Linnean Society of London. He then spent a further period in the West Indies before returning to England (1809). A series of lectures at the Linnean Society followed, describing the flora and fauna of the islands and also his own travels, and in February 1810 he was elected a fellow of the society.
Promoted to staff surgeon (December 1812), he was posted to the Mascarene Islands, serving at Madagascar and Mauritius, where he carried out medical duties and also served as a government agent. He continued to devote his time to the study of natural history, making a record of the botany of Mauritius and also a study of the extinct birds of the islands. In 1816 he published (anonymously) Catalogue of the exotic plants cultivated in the Mauritius. Shortly afterwards he sailed for England, and during the journey home fashioned a trawl from some fine-meshed cloth and began to collect samples of marine organisms from the sea. He had developed what would later be termed a plankton net. A similar device had been made and used by John Cranch during the Congo expedition of James Hingston Tuckey (qv) earlier in 1816, but Cranch had not lived to tell anyone of his invention. Thompson, therefore, is credited with independently developing the plankton net, and used it to gather samples during future researches.
In 1816 he was appointed medical inspector for the Cork military district, where he carried out his most important zoological researches. He became a familiar figure in Cobh harbour, sailing around the bay collecting samples of marine invertebrates. During the course of these researches he made three important discoveries: firstly, that some forms of planktonic crustacean, then known by the collective name of Zoea, were actually the commensal form of the Cancer pagurus – the European edible crab. He confirmed these findings with his work on the mysidacean crustacean, showing that these minuscule forms of life metamorphosed into larger crustaceans. These finds confirmed Rathke's work on the natural history of the crayfish. Thompson's second major discovery was that cirripeds were actually crustacea. In Cuvier's system they were classed as part of the Mollusca genus. Thompson caught some small translucent larvae in his plankton net and observed them in his laboratory as they gradually metamorphosed into acorn barnacles. His third discovery was a class of invertebrates that he named Polyzoa, usually referred to latterly as Bryozoi. These were already known, but were categorised as part of a heterogeneous collection of invertebrates known as Zoophytes. Thompson confirmed that they were a separate form of invertebrate, totally distinct from other hydroids and ascidians. Alongside these important discoveries, he also preserved samples of shallow-water crinoid echinoderms collected in Cobh harbour. These crinoids, such as feather-stars and sea lilies, were previously only known from samples collected in the West Indies. He published these findings on the crinoids in Memoir on the Pentacrinus Europaeus, a recent species discovered in the Cove of Cork (Cork, 1827).
His most important discoveries were published in a series of five pamphlets entitled Zoological researches and illustrations (Cork, 1828–34). They were greeted with opposition, if not contempt, by other zoologists, who found it impossible to believe that minute marine invertebrates could metamorphose into larger crustaceous life. His most notable opponent was the zoologist John Obadiah Westwood (1805–93); but gradually most of the scientific community came to accept Thompson's claims, owing to his meticulous methods of research. Promoted to deputy inspector of army hospitals (July 1830), he left Cork in 1835 and was appointed medical officer to convict settlements in New South Wales. While stationed in Australia he promoted the introduction of useful plants such as cotton and sugarcane. He died in Sydney 21 January 1847.
During the course of his career he published numerous other articles in journals such as the Entomological Magazine, the Transactions of the Linnean Society, and the Edinburgh New Philosophical Journal, including his observations of the natural history of the dodo, which were published in the Magazine of Natural History in 1829. He only published one medical tract, The pestilential cholera unmasked, brought out during the cholera outbreak of 1832. Like most publications on cholera during that period, it concentrated on the diagnosis and treatment of the disease rather than investigating its causes.
Considering he was not trained as a zoologist, Thompson's achievements were remarkable. He was of a practical frame of mind, carefully collecting samples and then monitoring their development in his laboratory. It was not until the twentieth century that the significance of his discoveries was fully recognised. In 1968 the Society for the Bibliography of Natural History republished his Zoological Researches in facsimile form. The naturalists Robert Brown and S. Moore also named marine species in his honour as Thompsonia and Vaughania. Other distinguished naturalists, including Charles Darwin, Sir Sidney Harmer, and T. R. R. Stebbing, also later referred to the importance of his work.