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Lyonet, Pierre

Lyonet, Pierre

(b. Maastricht, Netherlands, 21 July 1706; d. The Hague, Netherlands, 10 January 1789)


Lyonet’s family came originally from northeastern France. They were Calvinists, and their search for religious peace took them to Metz, the Palatinate, and finally Switzerland. Lyonet’s father, Benjamin Lyonet, migrated at the beginning of the eighteenth century to Holland, where in 1704 he married Marie le Boucher, the daughter of Huguenot refugees. He was a Presbyterian pastor and was given a parish in Heusden. Lyonet, the elder of two sons (four other children died in infancy), was a frail child. He later wrote: “I was always so quiet that I was thought to be deprived of reason; it was thus with no mild joy that my parents heard me, at two years of age, cry for the first time.”

Little is known about Lyonet’s early education, but it is likely that he studied Latin, Greek, and Hebrew under the tutelage of his father, who intended his son for the clergy. Lyonet entered Leiden University (1724), accordingly, as a student of theology. In view of the congeniality that existed in those years between science and theology (at least in Protestant countries), it is not surprising that Lyonet studied mathematics, Newtonian physics, military architecture, and anatomy during his first two years at Leiden. In 1728, a year after completing his course, he was admitted to the pastorate. He soon found, however, that he did not have a real vocation, and he persuaded his reluctant father to allow him to return to Leiden to study law (1730). He graduated after a year’s work, with a thesis entitled De justo quaestionis usu (on the just use of torture), and in the same year set himself up as an avocat in The Hague.

Although Lyonet was apparently successful at the bar, he discovered his life’s work elsewhere, through two discrete but probably related activities. He began to study insects and became a translator (1738) and then a cipher clerk for the government. As a clerk, working on his own initiative, he broke the code used by the Prussian ambassador to the United Provinces (cracking it took him eighteen months), then other codes used by diplomats in the country, and even those of diplomats in London whose letters passed through The Hague. After convincing his initially skeptical government of the usefulness of decoding, he was allowed to continue the secret work, and did so until his death. He fought for nearly ten years (from 1753) for recognition of his services in the only form acceptable to him: the title of Secretary of Ciphers, which was granted him in 1762.

Lyonet, like Bonnet, first became interested in the study of insects through reading Pluche’s Natural History, but he was inspired to study them seriously le first volume (on “chenilles et papillons”) of Réaumur’s Mémoires, which appeared in 1734. Réaumur’s influence on Lyonet was decisive, as it had been on Bonnet and Trembley. The magisterial volumes of Mémoires served as models to emulate and bases to build upon. Lyonet, who had respect for few naturalists, praised only Swammerdam and Reaumur. From Reaumur he learned method and the importance of being exceedingly careful.

Lyonet began systematic observation on insects in 1736. In 1738 he undertook to correct and expand a translation of F. C. Lesser’s Insectotheologia. Lyonet’s annotations to the translation indicate that he was familiar with the subject and that his ideas on the general biological problems of his time were already formed; his ideas on classification and generation found in the notes to Lesser also appear in the Traité anatomique of 1760 and in the posthumously published Recherches.

The Traité anatomique de la chenille qui rouge le bois de saule was begun in 1745. Lyonet had originally planned a treatise on all the insects in the vicinity of The Hague (and indeed the Recherches consist of that part of this project which he was able to complete). When he saw the fame that Trembley and Bonnet had achieved, however (Trembley had created a stir with the demonstration of regeneration of hydras in his Mémoir es pour servir à l’histoire d’un genre de polypes d eau douce, largely illustrated by Lyonet, while Bonnet had observed the parthenogenesis of aphids), he decided to establish his own reputation in micro-anatomy. He examined the common goat moth caterpillar (Cossuts ligniperda) and the anatomy of its chrysalis and imago. He intended to delineate the metamorphosis of the insect in subsequent volumes, but was prevented from doing so by an affliction of the eyes, which after 1767 made it impossible for him to do close work. Traité anatomique is devoted wholly to the anatomy of the caterpillar (except for a short initial chapter on its lifecycle), and the plates, drawn and engraved by Lyonet, portray the muscles, nerves, bronchia, heart, viscera, silk vessels, and the internal parts of the head with astonishing precision.

For Lyonet the principal enemies of sound thinking in natural history were l’esprite de systéme and mechanistic ideas,both exemplified by Buffon. Lyonet rejected both animalculist and ovist preformation theories of generation and believed that spontaneous (“equivocal”) generation was an illusion fostered by sloppy experimental technique. All animals come from eggs, he said, echoing Harvey (by way of Swammer-dam), except those few which reproduce by budding (Trembley’s polyps). Lyonet did not formulate a theory of generation, but the logic of his position would have led him to a theory of epigenesis, if he had pursued it. His declarations on generation could have been approved by Aristotle: in reproduction, both the female and male “principles” play a role.

Lyonet considered himself an empiricist, like Swarnmerdam and Réaumur, who examined insects, to be sure, but who saw only what any unbiased and respectful observer would see. In a way, it was so: the Traité anatomique is a triumph of the eye. But his empiricism was less than pure, since two assumptions controlled every line he wrote or drew. He believed, first, that the world and all its creatures are a vast cipher and, second, that the duty of man is to decode it. He found the natural world to be as intricately, precisely, and richly designed as a work by a Dutch artist; and he believed that the more this great design was elucidated, the greater would be man’s reverence for the Designer. The tasks of breaking the code by tracing the design to its last perfect detail was therefore perhaps the one supremely worthwhile thing to do.

Beginning about 1767 Lyonet, whose eyesight was still sufficient for everyday purposes, began to collect paintings, including those of Vermeer (widely thought to have been neglected in the eighteenth century). He spent his later years in preparing his notes on insects in the vicinity of The Hague for publication. Although he had a manuscript ready for the printer by 1787, various delays kept it from the presses until 1832, when W. de Haan published it as the Recherches.


I. Orginial Works. A complete list of Lyonef’s writings and drawings, published and unpublished, may be found in W. H. Van Seters, Lyonet(see below), 185–199. A sketchbook of Lyonet’s which turned up after the biography was published is described by Van Seters, “Lyonef s Kunstboek,“inMedical and Biological Illustration,13 (1963), 255–264. Lyonet’s works referred to in the text are Théologie des insectes on démonstration des perfections de Dieu dans ee que concerne les insectes, traduit de Voile mand de Mr Lesser avec des remarques de Mr P. Lyonet,2 vols. (The Hague, 1742); Traité anatomique de la chenille qui rouge le bois de saule (The Hague, 1760); and Recherches sur l’anatomie et les metamorphoses de différentes espéces d’ insectes, ouvrage posthume de Pierre Lyonet, publié par M. W. de Haan … (Paris, 1832).

II. Secondary Literture. A complete biographical source is W. H. Van Seters, Pierre Lyonet, 1706–1789, sa vie. ses collections de coquuillages et de tableaux, ses recherches entomologiques (The Hague, 1962); but see also Émile Hublard, “Le naturaliste hollandais Pierre Lyonet. Sa vie et ses oeuvres 1706—1789,” in Mérnoires et publications de la Société des sciences, des arts, et des letters du Hainaut,61 (1910), 1–159, also published separately (Mons, 1910), especially for a number of Lyonet’s letters. For the miheu, see J. R. Baker, Abraham Tremble of Geneva (London, 1952); R. S. Clay and T. H. Court,The History of the Microscope (London, 1932); F. J. Cole, Early Theories of Sexual Generation (Oxford, 1930); L. C. Miall, The Early Naturalists, Their Lives and Work (1530–1789) (London, 1912); Jean Torlais, Réaumur (Paris, 1936; new ed., 1961); Maurice Trembley, ed., Correspondance inédite cut re Réaumur et Abraham Trembley (Geneva, 1943); Aram Vartanian, “Trembley’s Polyp, La Mettrie, and Eighteenth-Century French Materialism, “in Journal of the History of Ideas,11 (1950), 259–286, repr. in P. P. Wiener and Aaron Noland, eds., Roots of Scientific Thought (New York, 1957), 497–516.

Stuart Pierson

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