scarce complete set of the first editions of leeuwenhoek's letters in dutch describing his groundbreaking microscopic observations. He published his findings in 2 series of letters addressed mostly to the Royal Society, numbered 28-146 and 1-XLVI, which are only infrequently found together complete; numbers 1-27 remained unpublished in Dutch, though abstracts of some appeared in Latin or English. "His most important contributions were made in the fields of microbiology, sexual reproduction, hematology, and plant anatomy. He was the first to recognize the true nature of microorganisms" (Norman). Garrison-Morton 67, 265; Dobell 20 (describing his own set, the only complete one known to him); Norman 1301-1315; Krivatsy 6778 (both incomplete).

For convenience and clarity the contents of the first volume are described below giving their paginations as originally published, but the internal parts of the individual works are bound in the numerical order of the letters instead, and the set is being sold as is.

Volume 1

Ondervindingen en Beschouwingen der onsigtbare geschapene Waarheden, vervat in verscheydene Brieven. [8], 8; 32 pages. Scattered foxing. Leiden: Daniel van Gaesbeeck, 1684. Dobell 1, containing letters 32 and 33.

Ontledingen en Ontdekkingen van levende Dierkens. 3 engraved plates. [2] (of [4]), [5]-40; 35 pages, including etched additional title by Romeyn de Hooghe dated 1685; lacks the letterpress title. Dampstaining in upper outer corners. Leiden: Cornelis Boutesteyn, 1686. Dobell 8, containing letters 28-31 and 34-36.

Ondervindingen en Beschouwingen . . . waar in gehandeld werd, vande Eyerstok [etc.]. [2], 21, [1]; 19 pages. First part dampstained, second part browned. Leiden: Daniel van Gaesbeeck, 1684. Dobell 2, containing letters 37 and 39.

Ontledingen en Ontdekkingen van de onsigtbare Verborgentheden. 94 [i. e., 88] pages. Dark stains in upper margins. Leiden: Cornelis Boutesteyn, 1685. Dobell 5, containing letters 38, 42, and 43.

Ondervindingen en Beschouwingen . . . waar in gehandelt wert vande Schobbens inde Mond [etc.]. [4], 24 pages. Contents relatively clean. Leiden: Daniel van Gaesbeeck, 1684. Dobell 3, containing letter 40.

Ondervindingen en Beschouwingen . . . waar in gehandelt werd over het Maaksel van't Humor Cristallinus. [2], 26 pages. Leiden: Daniel van Gaesbeeck, 1684. Contents clean apart from crudely obliterated stamp on title. Dobell 4, containing letter 41.

Ontdekkingen en Ontledingen van Sout-Figuren [etc.]. Folding engraved plate. 76 pages. Plate discolored, contents otherwise clean. Leiden: Cornelis Boutesteyn, 1685. Dobell 6, containing letters 44 and 45.

Ontledingen en Ontdekkingen van het Begin der Planten in de Zaden van Boomen. Folding engraved plate. 78 pages. Contents dampstained. Leiden: Cornelis Boutesteyn, 1685. Dobell 7, containing letters 46 and 47.

Volume 2

Ontledingen en Ontdekkingen van de Cinnaber naturalis, en Bus-Poeder [etc.]. Folding engraved plate. 109, [1] pages. Contents relatively clean. Leiden: Cornelis Boutesteyn, 1686. Dobell 9, containing letters 48-52.

Vervolg der Brieven. 8 engraved plates. [8], 155 pages. Few stains in outer margin of title. Leiden: Cornelis Boutsteyn, 1687. Dobell 10, containing letters 53-60. Without the portrait called for by Dobell, apparently in error (see Natuurs Verborgentheden Ontdekt below).

Den Waaragtigen Omloop des Bloeds . . . klaar voor de Oogen gestelt. Folding engraved plate. [2], 30 pages. Lower margin of plate cropped slightly entering image. Delft: Andries Voorstad, 1688. Dobell 11, containing letter 65, on the circulation of the blood.

Natuurs Verborgentheden Ontdekt: zijnde een Tweede Vervolg der Brieven. 6 engraved plates. [4], 157-260, 269-298, [2], 299-350 pages, including portrait of Leeuwenhoek (conjugate with the title), and blank between letters 65 and 66. Contents relatively clean. Delft: Andries Voorstad, 1689. Dobell 12 (portrait not noted), containing letters 60-66.

Volume 3

Derde Vervolg der Brieven. 6 engraved plates. [8], 351-531 pages. Some light marginal foxing. Delft: Henrik van Kroonevelt, 1693. Dobell 13, containing letters 68-75.

Vierde Vervolg der Brieven. 6 engraved plates. [2], 533-730 pages. Scattered light foxing, partial discoloration on a few plates. Delft, Henrik van Kroonevelt, 1694. Dobell 14, containing letters 76-83.

Register . . . van alle de Werken van Heer Antoni van Leeuwenhoek . . . in twee Deelen. 34; 29 pages. Spotting throughout. Leiden: Cornelis Boutesteyn, 1695. unknown to dobell.

Volume 4

Vijfde Vervolg der Brieven. 7 engraved plates. [8], 172, [10] pages, including engraved additional title. Clean tear and oxidized old stamp in lower outer corner of letterpress title, offsetting onto verso of additional title and showing through on recto, scattered foxing. Delft: Henrik van Krooneveld, 1696. Dobell 15, containing letters 84-96.

Sesde Vervolg der Brieven. 5 engraved plates. [4], 173-342, [10] pages. Light dampstaining in upper margins, scattered foxing. Delft: Henrik van Krooneveld, 1697. Dobell 16, containg letters 97-107.

Sevende Vervolg der Brieven. 25 engraved plates. [6], 452, [22] pages. Light dampstaining in upper margins. Delft: Henrik van Krooneveld, 1702. Dobell 18, containing letters 108-146.

Volume 5

Send-Brieven . . . over verscheyde Verborgentheden der Natuure. 31 engraved plates. [16], 460, [28] pages, including engraved additional title with inset portrait. Old stamp in lower outer corner of letterpress title, contents generally clean. Delft: Adriaan Beman, 1718. Dobell 19, containing letters I-XLVI.