Peter Simon, a distinguished naturalist and geographer, born on the 22d of September 1711, was the son of Simon Pallas, a surgeon in the Prussian army, and professor of surgery at Berlin. He received the early part of his education in his father's house, and his instructors bore ample testimony to the rapidity of his progress. At the age of fifteen he began to attend medical lectures; and he applied himself so closely to practical anatomy, that in 1758 he was found qualified to deliver a course of public lectures on that science. In the same year he went to Halle, and became the pupil of Segner, continuing also his studies of zoology, and, in particular, of entomology, with great assiduity. In 1759 he removed to Göttingen, where he made a variety of experiments on poisons, and on other active medical substances, and commenced his observations on parasitical animals. In July 1760 he went on to Leyden, in order to attend the lectures of Albinus, Gaubius, and Muschenbroek; and at the end of the same year he took his degree of Doctor of Physic. The following summer he proceeded to England, principally with the view of completing his medical education, although he devoted the greater part of his time to the active pursuit of natural history, being assisted and encouraged by the friendship of Peter Collinson and of some other British naturalists, which procured for him, a few years afterwards, the distinction of having his name inserted in the list of the foreign members of the Royal Society, at the early age of twenty-three. He visited several parts of the coast of England, in order to examine its marine productions; and his love of natural history enabled him to profit in a similar manner. by an accident which detained him for some time at Harwich, on his return to the Continent, in the spring of 1762.

Having paid a visit to his native city, he went again to the Hague, and established himself as a resident there under the patronage of Gaubius. On occasion of the publication of a miscellaneous work on zoology, which he dedicated to the Prince of Orange, he proposed a plan for an expedition to the Cape of Good Hope, and to the Dutch East Indies, which he offered to conduct in person; but although the project was encouraged by Gaubius, and approved by the prince, his father's interference prevented its execution, and obliged him to return to Berlin. His filial affection, however, was not strong enough to induce him to refuse the invitation of the Empress Catharine to St Petersburg, where he accepted, in the year 1767, the appointment of professor of natural history in the Imperial Academy of Sciences.

The first few months of his residence at St Petersburg were employed in preparing his Zoological Gleanings for publication, and in making catalogues of some collections of natural history. It was now that the more active career of his public life was about to commence; and in 1768 he undertook, in common with Falk, Lepechin, and Guldenstäd, the conduct of an expedition sent out by the empress, for the joint purposes of observing the transit of Venus, and of investigating the natural history and geography of Siberia and the neighbouring countries. The object of their researches for the first summer was the province of Kasan, and the winter was passed at Simbirsk; the next year they examined the shores of the Caspian and the borders of Calmuck Tartary; after which they returned through Orenburg, and passed the winter at Ufa. In 1770 Pallas crossed the Urals Mountains to Catharinenburg, and, after examining the mines in that neighbourhood, proceeded to Tobolsk. The next year he went to the Altai Mountains, traced the course of the Irtysch to Kolyvan, went on to Tomsk, and observed the natural freezing of quicksilver at Krasnoyarsk, on the Yenisei, in Lat. 56° 30' N. He proceeded in March 1772 by Irkutsk across the Lake Baikal, as far as Kiatka, and returned to Krasnoyarsk. In 1773 he visited Tara, Astracan, and Tzaritzin, on the Volga, and returned to St Petersburg in 1774, after an absence of six years. About ten years later he was made a member of the Board of Mines, with an additional salary of L200 a year; and he was complimented with the title of a Knight of St Vladimir. The empress purchased his collection of natural history for a price one-third greater than his demand, and allowed him, at the same time, to keep it in his possession for the remainder of his life.

In 1794 he took a journey into the Crimea, and was captivated with the beauty of the country and its productions; the climate also appearing to be such as his health was supposed to require, he obtained from his munificent patroness not only permission to establish himself there, but a grant of a large and fertile estate, and a sum of 10,000 rubles to assist him in his outfit. He was thus enabled to build a little palace rather than a country house, in which a traveller from the north of Europe was sure to receive the most obliging hospitality, as Dr Clarke has made well known to the English reader. It appears, however, that the air was not altogether exempt from the miasmas, which are the causes of paludal fevers; and some other circumstances, besides the distance from all civilized society, seem to have made the old age of Pallas more cheerless than he had anticipated to find it, in the independence and tranquillity of his patriarchal establishment at Akmetchet (Simpheropol.) About ten years after the period of Dr Clarke's travels, he undertook a journey to Berlin to pay a visit to his brother, and died there in September 1811.

Linnaé the younger has given him a genus, Pallasia, in his Supplementum Plantarum; a compliment to which his unremitting labours in every department of natural history had amply entitled him. His collection of dried plants was purchased by Dr Clarke's fellow-traveller, Mr Cripps, and passed into the possession of Aylmer Bourke Lambert. The general character of Professor Pallas's acquirements appear to have been that of extent and variety, together with fidelity. He was not the author of any new theories or improved systems; and it has sometimes been observed, as by Murray in his System of Vegetables, that his descriptions were somewhat defective, from the omission of correct specific distinctions; but this omission is of such a nature as to affect a compiler or a book-maker much more than an actual student of natural history, who is studying for his own improvement only, and who is capable of entering into a detailed examination of the objects concerned. To such a detail the principal part of Professor Pallas's works have relation; and it is impossible to enumerate the whole of his memoirs without making a pretty extensive catalogue of the productions of the various kingdoms of nature.

1. His Dissertatio Inauguralis de Insectis viventibus intra Viventia, 4to, Leyden, 1760, containing a systematic account of intestinal worms, is said to have been previously published in another form at Göttingen a short time before he went to Leyden. 2. We find in the Philosophical Transactions for 1763, p. 65, a short note on the Cold observed at Berlin in the previous winter. 3. In the volume for 1776, p. 263, a description of the Jaculator Fish, or Scomus jaculator, of the Indian Ocean, which catches insects by darting jets of water at them. This description is repeated in the Speciologia Zoologica, fasc. 8, 4. Etrenhus Zoophytorum, 8vo, Hague, 1766; containing nearly 300 species; Dutch by Hoddart, with figures, 8vo, Utrecht, 1768. 5. Miscellanea Zoologicae, 4to, Hague, 1766; consisting of descriptions and dissections. 6. Speciologia Zoologica, 4to, Berl. 1767-1780. Of this valuable collection of memoirs, intended for the description and illustration of new or little-known species of animals, there appeared in the whole fourteen fasciculi; some of them were published by Professor Martin during the author's absence in Siberia. We find amongst other articles, an interesting account of the musk-deer of various species of the antelope, and the different varieties of sheep, both wild and tame; the latter has been published in English, On Russian and Tartar Sheep, 8vo, Edinburgh, 1794. 7. In the Nov. Act. Acad. Nat. Cur., vol. iii., p. 430, Phalaromus biga; an account of two species of moth, of which the females are without wings, and spontaneously fertile. 8. A variety of miscellaneous papers, by Pallas, appeared in the Stremlow Magazine, which began to be published at Berlin in 1767. They chiefly relate to the Winter Residence of Swallows, vol. i., p. 20; to Hyalidiae found in the abdomen of ruminant animals, and supposed to be a species of Taenia, p. 64; to the Birds of Passage of Siberia, p. 145, from Hottentot Notes; to Tartar's supposed discovery of the Origin of the Boletus, p. 197; to Scopulae, or butterflies of insects, p. 262; to a Dolphin supposed to be preserved in Siberia from the Sitta or nut-hatch, p. 311; to the Elk or Moose-Deer, p. 382, from Heller's papers; and to the use of the Sphecodium in Kamtschatka, p. 411. 9. Collections relating to the Mongol Tribes, published in 1776, and showing that they are distinct from the Tartars. 10. Professor Pallas's contributions to the Memoirs of the Imperial Academy of St Petersburg are also very numerous, and on miscellaneous subjects. In the Novi Commentarii we find an account of the Tubularia Fungosa, vol. ii., observed near Wolodimer; Lepas punctilus, and Fossil Bones of Siberia, vol. xviii.; Quadrupeds and Birds observed in 1769, vol. xiv.; 1; Observations of Exotic Animals in Northern Asia, vol. xviii., especially the skulls of the animals of the buffalo, Tragelaphus niloticus, Equus hemionus, and Loxorua apoda, vol. xix.; the last also in Geestek. Jornbæk, ii. In the Acts for 1777, ii., An Account of the Teeth of an Unknown Animal, like those which have been found in Canada; Observations from Camper's Letters, on a Myrmecophaga and a Didelphis, and Equus asinus in the wild state. In the volume for 1779, ii., a Description of Plants peculiar to Siberia; Corpus Canescens, also in Lichtenberg's Magazine, ii. For 1780, part i., Quadrupedes visus, part ii., On the Variations of Animals, and Didelphis brachyura. For 1781, part i., Felis manul, a new Asiatic species of Felis; ii., on some species of Sorax. In the volume for 1783, New Species of Fishes; and 1784, On some New Marine Productions. II. The Observations sur la Formation des Montagnes, et les Changements arrivés au Globe, particulièrement à l'égard