Peter, an ingenious naturalist, and member of several learned societies, was born at Maastricht, and descended from a very ancient and respectable family of Lorraine. He had scarcely attained his seventh year when 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 languages, of which he understood no less than nine, living and dead. Having entered the university of Leyden, he studied the Newtonian philosophy, geometry, and algebra; but his father, who was a clergyman, desiring that he should apply himself to divinity, he reluctantly abandoned the former studies, his passion for which was not to be easily overcome. At the same time he applied himself to anatomy, and also to music and drawing. He afterwards began to practise sculpture, and executed several pieces in wood, some of which are preserved, and have been greatly admired by the artists. He then betook himself to drawing portraits of his friends from life, in which, 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. Having arrived at the Hague, he undertook the study of deciphering, and became secretary of ciphers, translator of the Latin and French languages, and patent-master to their High Mightinesses. Meanwhile, having taken a strong liking to the study of insects, he undertook to give an historical description of such as are found about the Hague, and with that view 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 connoisseurs. In the year 1724 was printed, at the Hague, a French translation of a German work entitled the Theology of Insects, by Mr Lesser. Love of truth induced Mr Lyonet to defer the publication of his description above mentioned, and to make some observations on that work, to which he added two beautiful plates, engraved from his designs. This performance caused his merit to be universally known. The celebrated M. de Reaumur had this translation reprinted at Paris, not so much on account of the work itself, as of Mr Lyonet's observations; and bestowed upon 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 from Mr Wandelaar, engraved three or four small plates, and immediately began upon the work himself, which he executed in such a manner as attracted the highest 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 admitted a member of the Royal Society of London. In 1749 he began, by mere chance, his collection of horns and shells, which, according to the universal testimony of all travellers and amateurs who visited it, became the most beautiful, and certainly one of the most valuable, in Europe. In 1753 he was chosen a member of the Dutch Society of Sciences at Haerlem, then recently established; and in 1757, after the celebrated M. le Cat, professor of anatomy and surgery, had seen Mr Lyonet's *Traité Anatomique de la Chéneille qui rouge le Bois de Saule*, with the drawings belonging to it (a work which was afterwards published), he was elected member of the Royal Academy of Sciences of Rome, of which 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 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 plate (as he 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 had used to ascertain the degree of strength of his magnifying glasses. But notwithstanding all his labours, which were considerably increased by the extensive correspondence which he had for many years carried on with several learned persons, he still found means to set apart a large proportion of his time for the immediate service of his country; but he was not fortunate enough 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 superb cabinet of paintings, consisting of more than 560 performances, amongst which are many of the most eminent works of the first Dutch masters. His object in doing so was to procure himself some amusement during the latter part of his life, when old age and infirmities had weakened his powers, and set bounds to his activity. He had always indeed accustomed himself to employment, insomuch that he wrote some pieces of Dutch poetry; and this disposition remained with him until within a fortnight of his death, when he was attacked with an inflammation in the chest, which, though apparently cured, proved in the end the cause of his death. He died at the Hague in January 1789, aged eighty-three years, leaving behind him a most estimable character.