PETER, an ingenious naturalist, and member of several learned societies, was born at Maestricht, and was descended from a very ancient and respectable family of Lorrain. He had scarcely attained his seventh year before he displayed an uncommon strength and agility in all bodily exercises; but he was not less diligent in the improvement of his mind. Being placed at the Latin school, he learned chronology, and exercised himself in Latin, Greek, and French poetry, as also in Hebrew, logic, and the Cartesian physics. He was particularly fond of the study of lan- guages, whereof he understood no less than nine, living and dead. Having entered the university of Leyden, he studied the Newtonian philosophy, geometry, algebra, &c.; but his father (who was a clergyman), desiring he should attach himself to divinity, he reluctantly abandoned the former studies, as his passion for them was not easily to be overcome. He at the same time applied himself to anatomy, and also to music and drawing. He began afterwards to practice sculpture; and performed several pieces in wood, some of which are preserved, and have been greatly admired by the artists. After this, he betook himself to drawing portraits of his friends from life; wherein, after three or four months practice, he became a great proficient. Having attained the degree of candidate in divinity, he resolved to study law, to which he applied himself with so much zeal, that he was promoted at the end of the first year. Arrived at the Hague, he undertook the study of deciphering; and became secretary of the cyphers, translator of the Latin and French languages, and patent-matter to their High Mightinesses. Meanwhile, having taken a strong liking to the study of insects, he undertook an historical description of such as are found about the Hague, and to that end collected materials for several volumes; and having invented a method of drawing adapted thereto, he enriched this work with a great number of plates, universally admired by all the connoisseurs who had seen them. In the year 1724 was printed at the Hague a French translation of a German work, the 'Theology of Insects,' by Mr Leifer. Love of truth engaged Mr Lyonet to defer the publication of his above-mentioned description, and to make some observations on that work, to which he has added two most beautiful plates, engraved from his designs. This performance caused his merit to be universally known and admired. The celebrated M. de Reaumur had the above translation reprinted at Paris, not so much on account of the work itself, as of Mr Lyonet's observations; and bestowed on it, as did also many other authors, the highest encomiums. He afterwards executed drawings of the fresh water polypus for Mr Trembley's beautiful work, 1744. The ingenious Wandelaar had engraved the first five plates; when Mr Lyonet, who had never witnessed this operation, concerned at the difficulties he experienced in getting the remaining eight finished in the superior style he required, resolved to perform the task himself. He accordingly took a lesson of one hour of Mr Wandelaar, engraved three or four small plates, and immediately began upon the work himself, which he performed in such a manner as drew on him the highest degree of praise, both from Mr Trembley and from many other artists, particularly the celebrated Van Gool; who declared that the performance astonished not only the amateurs, but also the most experienced artists. In 1748 he was chosen member of the Royal Society of London. In 1749 he began (by mere chance) his amazing collection of horns and shells, which, according to the universal testimony of all travellers and amateurs who have visited it, is at present the most beautiful, and certainly one of the most valuable, in Europe. In 1753 he became member of the newly-established Dutch Society of Sciences at Haerlem; and in 1757, after the celebrated M. le Cat, professor in anatomy and surgery, and member of almost all the principal societies in Europe, had seen Mr Lyonet's incomparable Traité Anatomique de la Cheville qui roule le Bois de Saule, with the drawings belonging to it (which work was afterwards published), he was elected member of the Royal Academy of Sciences of Rome, whereof M. le Cat was perpetual secretary. After the publication of this treatise, he became, in 1760, member of the Royal Academy of Sciences of Berlin; in 1761, of the Imperial Academy of Naturalists; and, in 1762, of the Imperial Academy of Sciences at St Petersburg. In order to enable such as might be desirous of following him in his intricate and most astonishing discoveries respecting the structure of this animal, Mr Lyonet published, in the Transactions of the Dutch Society of Sciences at Haerlem, a description and a plate (as he also afterwards did in French at the beginning of his Traité Anatomique) of the instrument and tools he had invented for the purpose of dissection, and likewise of the method he used to ascertain the degree of strength of his magnifying glases. Notwithstanding all this labour, which was considerably increased by the extensive correspondence which he for many years carried on with several learned and respectable personages, he still found means to set apart a large proportion of his time (as he himself mentions it in his preface) for the immediate service of his country; but was not fortunate enough (as appears by his writings) to get any other recompense for his exertions than sorrow and disappointment.—During the last fifteen or twenty years of his life, Mr Lyonet added to the valuable treasure he had already collected of natural curiosities, a most superb cabinet of paintings, consisting of more than 560 performances; among which are many of the most eminent works of the first Dutch masters. He did this with a view to procure himself some amusement during the latter part of his life, when old age and infirmities must weaken his powers, and fet bounds to his activity. He had always indeed accustomed himself to employment, in so much that he has written some pieces of Dutch poetry; and this disposition remained with him till within a fortnight of his death, when he was attacked with an inflammation in his breast, which, though apparently cured, was, in the end, the cause of his dissolution. He died at the Hague in January 1789, aged 83 years, leaving behind him a most estimable character.