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 a ‘Catalogue of Plants growing in the vicinity of Berwick-on-Tweed.’ While in the military service he interested himself in zoological work. During his nine years' service in the West Indies he described in 1809 a new pouched-rat from Jamaica, Mus anomalus (Trans. Linn. Soc. vol. ii. 1815), while he observed and was the first to explain the habit of land-crabs in going down to the sea to spawn, and the changes of form which the young crab undergoes during development.

At the close of 1809 Thompson returned to England, and on 6 Feb. 1810 was elected to the fellowship of the Linnean Society, in whose ‘Transactions’ (1808, vol. ix.) his observations on certain British birds had already been published. In 1812 Thompson sailed for Madagascar and the Mauritius, where he spent four years. He was deputed to introduce vaccine into Madagascar for two successive years, and devoted a considerable part of the remainder of the time to an examination of the famous extinct Mascarene birds. His observations on the dodo appeared in the ‘Magazine of Natural History’ for 1829.

After his return in 1816 Thompson settled at Cork as district medical inspector, and completed those wonderful discoveries of the life-histories of the marine invertebrata of the Cove of Cork, which made his name famous. In 1830 he was appointed deputy inspector-general, and in 1835 he went to Sydney in charge of the convict medical department and as acting officer of health. He remained in New South Wales until his death at Sydney on 21 Jan. 1847.

Vaughan Thompson has secured a permanent place in zoological literature through his discoveries of the nature and life-histories of the feather-star (Antedon, belonging to the Crinoid echinodermata), the polyzoa, the cirripedes (or barnacles), and several divisions of the crustacea. Our present conceptions of the structure of these forms, of their zoological position, and of the metamorphoses which they undergo, date from Thompson's papers.

The first of these, ‘A Memoir on Pentacrinus Europæus, a recent species discovered in the Cove of Cork’ (1 July 1823, Cork, 4to, 2 plates), announced the presence of a stalked crinoid in our seas; the discovery that the crinoidea were truly ‘radiata,’ and that (as was shown more fully by a second paper in the ‘Edinburgh New Philosophical Transactions,’ 1836) this pentacrinus was really the young stage of antedon, the feather-star. These startling conclusions drew the attention of zoologists in France, Germany, and elsewhere to Thompson's work, and many of his succeeding papers were translated or abstracted into scientific journals abroad.

In September 1828 there appeared the first number of Thompson's ‘Zoological Researches,’ published at Cork, containing an account of the life-history of the shore-crab. With the exception of Slabber, who published some observations on the subject at Haarlem in 1778, Thompson was the first to point out that, contrary to the received opinion, the crab passes through such a remarkable series of changes of form and structure in attaining the adult condition as to constitute a veritable metamorphosis. The greater part of the remainder of Thompson's work, of which six numbers appeared between 1828 and 1834, consisted in the detection of the metamorphosis in other groups of the crustacea.

His third discovery was the nature and life-histories of barnacles (Zool. Researches, No. iii., 1830, and Phil. Trans. 1835). Up to 1830 these animals, chiefly owing to Cuvier's influence, had been classed with the mollusca. Thompson showed that from their structure, and the nature and fate of their larvæ, the cirripedes must be considered to form a division of the crustacea.

The last of Thompson's more important discoveries was that of ‘Polyzoa, a new Animal discovered as an Inhabitant of some zoophytes’ (Zool. Researches, No. iv., Memoir v., December 1830). This paper demonstrated ‘another form of animal not hitherto known, and which, while it must be allowed to belong to a new type of mollusca acephala, resembles exteriorly in some measure the hydra.’ ‘This discovery will remove that part of the sertularia not provided with distinct oviferous receptacles to the class mollusca acephala, as well as such other genera as may hereafter be found similarly circumstanced.’ These and other passages clearly show that Thompson used the term ‘polyzoa’ as the name of a colonial animal exhibiting a distinct type of structure and hitherto confounded with hydroid polypes (for the discussion of Thompson's meaning of polyzoa see British Marine Polyzoa, i. 131).

There is no complete list of Vaughan Thompson's works. Papers contributed by him to learned societies are to be found in the Royal Society's ‘Catalogue’ (v. 958–9). Besides an important paper (Entomol. Mag. 1836) containing a large number of observations on Sacculina, a parasite of crabs, on land crabs, and other crustacea, Thompson evidently wrote, but never published, works on the development of parasitic copepoda, since he announced several discoveries in the covers of his ‘Zoological Researches.’