Specimens: Sperm

Leeuwenhoek observed sperm in various animals for forty years in about thirty letters, around a fifth of the 165 letters that he published himself. The two letters in 1711 and 1712 that were not published by him were excerpted in Philosophical Transactions.

Leeuwenhoek was among the leading spermists (also called animalculists), who theorized that reproduction occurred through the sperm. Other prominent spermists included Nicolaas Hartsoeker and Gottfried Leibniz. The role of the ovaries and eggs was not clear to them. The ovists, who theorized that reproduction occurred through the female egg, far out-numbered the spermists.

Links to letters below under Learn more.

1677 November (Letter 35 [22]) to William Brouckner: human sperm

1678 March 18 (Letter 38 [24]) to Nehemiah Grew: dog, rabbit, stallion and bull, theory of impregnation

1678 May 31 (Letter 39 [25]) to Nehemiah Grew: rabbit, dog

1679 February 21 (Letter 42 [27]) to Nehemiah Grew: cod

1679 April 25 (Letter 43 [28]) to Nehemiah Grew: cod, pike, more than 10,000 little animals in every small sand-grain of matter, hare, cock, estimated 50,000 sperm in a sand grain of matter, calculated 13,385,000,000 human beings on earth and 150,000,000,000 sperm in cod milt

1680 January 12 (Letter 54 [29]) to Robert Hooke: perch, bream, roach and tench

1680 April 5 (Letter 57 [30]) to Robert Hooke: rat, origin of sperm

1680 November 12 (Letter 65 [33]) to Robert Hooke: horse, may-bug, dragon-fly, grasshopper, fly, flea and gnat

1683 January 22 (Letter 70 [37]) to Christopher Wren: number of sperm repeated from Letter 43 [28]

1683 July 16 (Letter 72 [38]) to Christopher Wren: frog, rabbit and dog

1685 March 30 (Letter 84 [45]) to Members of the Royal Society: most detailed theory of impregnation

1685 July 13 (Letter 85 [46]) to Members of the Royal Society: similarities of plant and animal generation

1686 May 14 (Letter 92 [50]) to Antonio Magliabechi: included a passage from Letter 85 [46] about the germination of plants

1687 August 6 (Letter 102 [57]) to Members of the Royal Society: calandar

1688 August 24 (Letter 109 [64]) to Members of the Royal Society: calculated number of sperm in cod roe

1694 March 2 (Letter 134 [80] to to Members of the Royal Society: no sperm found in any eggs

1695 September 18 (Letter 157 [95]) to Johann Wilhelm von Pfalz-Neuburg: mussels

1696 July 6 (Letter 170 [103]) to Nicolaas Witsen: oysters

1700 July 9 (Letter 214 [128]) to Hans Sloane: cock

1700 October 26 (Letter 219 [134]) to Hans Sloane: aphids

1700 December 25 (Letter 220 [135] to Hans Sloane: ram, man, cock, objections to Hartsoeker

1701 April 15 (Letter 224 [137]) to Members of the Royal Society: cod, pike, ram

1701 December 6 (Letter 231 [142] to Hans Sloane: cock

1701 December 20 (Letter 232 [143]) to Members of the Royal Society: spiders

1702 April 20 (Letter 236 [146]) Karl von Hessen-Kassel: silk moth

1711 August 18 (Letter 287) to James Petiver: ram

1712 March 1 (Letter 292) of to Members of the Royal Society: whale

1715 September 28 (Letter 317 [XVIII]) to Gottfried Leibniz: public acceptance of his theory of procreation, perch, cod

1716 May 19 (Letter 326 [XXIII]) to Gottfried Leibniz: impregnation

In three letters, Leeuwenhoek defended his ideas.

1698 December 17 (Letter 196 [113]) to Harmen van Zoelen
He defended the priority of his ideas about reproduction against Hartsoeker, quoting extensively from Letter 35 [22] of November 1677 and Letter 38 [24] of 18 March 1678 (see above)

1699 June 9 (Letter 200 [116]) to Members of the Royal Society
He defended his idea of sperm against Dalenpatius.

1699 June 23 (Letter 201 [117]) to Members of the Royal Society
He defended his idea of generation and reproduction of sperm against Lister.

Sources

Year	Author	Title
1930	Cole, F. J.	Early theories of sexual generation
1937	Cole, F. J.	Leeuwenhoek's zoological researches. Part I.
1950	Schierbeek, A.	Antoni van Leeuwenhoek. Zijn leven en zijn werken (2 vols.)
1959	Schierbeek, A.	Measuring The Invisible World
1965	Belloni, L.	Leeuwenhoek, Boerhaave und Bleyswyk über Spermatozoën
1977	Kremer, J.	Antoni van Leeuwenhoek, grondlegger van de spermatologie
1982	Lindeboom, G. A.	Leeuwenhoek and the problem of sexual reproduction
1983	Ruestow, E. G.	Images and ideas: Leeuwenhoek's perception of the spermatozoa
1996	Ruestow, E. G.	The Microscope in the Dutch Republic: The Shaping of Discovery

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Specimens: Ovaries

Related letters:

What Leeuwenhoek wrote ...
Wrote Letter L-060 of 1677-11-09 to William Brouncker about sperm and their movements in fresh human semen
Wrote Letter L-070 of 1678-03-18 to Nehemiah Grew about sperm in other animals and what Harvey and de Graaf got wrong about reproduction
Wrote Letter L-073 of 1678-05-31 to Nehemiah Grew about teeth, bone, hair, and sperm and what de Graaf got wrong about ovulation
Wrote Letter L-078 of 1679-02-21 to Nehemiah Grew about cod sperm and about not finding any little animals in blood or saliva
Wrote Letter L-080 of 1679-04-25 to Nehemiah Grew about living little animals in fish, hare, and dogs and his calculation that more than ten times as many living animals come from the milt of a cod as there are people living on the Earth
Wrote Letter L-097 of 1680-01-12 to Robert Hooke about the structure of wood and sperm in fish
Wrote Letter L-102 of 1680-04-05 to Robert Hooke about the testicles and sperm of a rat and organisms in the gills of oysters and in the sap of vines
Wrote Letter L-111 of 1680-11-12 to Robert Hooke about blood globules, lees of wine, globules in rain water, milk vessels, reproduction, little animals in the male seed of animals, and their incomprehensible smallness
Wrote Letter L-122 of 1683-01-22 to Christopher Wren about the function of the ovary, muscles of insects, drinking tea and mild beer, erythrocytes, and a theory on the formation of blood
Wrote Letter L-128 of 1683-07-16 to Christopher Wren about the procreation of frogs, sperm in fowl's egg, reproduction of rabbits, little animals in frog intestines, a theory about digestion in humans and fish, and blood
Wrote Letter L-157 of 1685-03-30 to Members of the Royal Society about sperm, the uterus of a bitch, sheep embryos, ovaries in young animals and apples, and his claims that sperm are the life-carriers and that there are male and female sperm
Wrote Letter L-159 of 1685-07-13 to members of the Royal Society about reproduction of trees, transfer of nutrients, male and female trees, hazelnut, comparing reproduction of mammals with reproduction of plants, cross-breeding, and germination
Wrote Letter L-175 of 1686-05-14 to members of the Royal Society about gall-nuts found on oak trees and the germination of plants
Wrote Letter L-190 of 1687-08-06 to members of the Royal Society about the calander and the louse and against spontaneous generation
Wrote Letter L-199 of 1688-08-24 to the members of the Royal Society about gnats, horseflies; growth of branches, germination of wheat plants, the soft and hard roe of cod, and the number of sperm in a cod's soft roe
Wrote Letter L-239 of 1694-03-02 to the members of the Royal Society about ear wax and hair, body hair, the amount of sweat secreted from the human body, and the possibility that sperm might penetrate the ovum
Wrote Letter L-271 of 1695-09-18 to Johann Wilhelm von Pfalz-Neuburg about swan mussel sperm, eggs, embryos, and locomotion, small animals as food for larger ones and oysters and their larvae; he again refutes spontaneous generation
Wrote Letter L-296 of 1696-07-16 to Frederik Adriaan van Reede about the male and female sexual organs of oysters and their larvae
Wrote Letter L-349 of 1698-12-17 to Harmen van Zoelen to defend himself against Hartsoeker's claim to have been the first to discover sperm
Wrote Letter L-356 of 1699-06-09 to the members of the Royal Society to dispute Dalenpatius's 'Nouvelles de la Republique des lettres', in which sperm are described as having the shape of the human body
Wrote Letter L-357 of 1699-06-23 to the members of the Royal Society in response to Martin Lister's objections against his theory of generation; his opposition to the theory of spontaneous generation; the assumption of male and female spermatozoa
Wrote Letter L-372 of 1700-07-09 to Hans Sloane about red blood cells in flounder and salmon, how their oval form changes shape to pass through capillaries, and the sperm of a young cock
Wrote Letter L-378 of 1700-10-26 to Hans Sloane about black flies on fruit trees, aphids, comparing the parthenogenetic procreation of aphids with sperm, and the development of the pupae of moths
Wrote Letter L-380 of 1700-12-25 to Hans Sloane about the sperm of a ram and his objections to Nicolaas Hartsoeker's claim to have discovered sperm first in 1678 when Leeuwenhoek had written to the Royal Society about sperm in 1677
Wrote Letter L-385 of 1701-04-15 to the members of the Royal Society about sperm from cod, a calculation of its size, and ram and pike sperm
Wrote Letter L-398 of 1701-12-06 to John Somers about the sperm of young cocks living for days outside the cock and whether that was long enough to fertilise a hen's egg
Wrote Letter L-399 of 1701-12-20 to the members of the Royal Society about the sperm of spiders and how they copulate
Wrote Letter L-403 of 1702-04-20 to Karl von Hessen-Kassel as a cover letter for Letter L-404
Wrote Letter L-480 of 1711-08-18 to James Petiver about the sperm of young rams and to explain what happened when Petiver tried to visited
Wrote Letter L-485 of 1712-03-01 to the members of the Royal Society about the skin and flesh of a whale, its seminal vessels, and its blood with comparisons to the blood of other fish
Wrote Letter L-521 of 1715-09-28 to Gottfried Leibniz about scholars who do not agree with Leeuwenhoek; sperm the same size in different animals; the pulse; posthumous letters; muscle fibers, tendons, and nerves; Hartsoeker; why he won't train students
Wrote Letter L-532 of 1716-05-19 to Gottfried Leibniz about muscle and tendon fibers, mammal teats, sperm; did not find eggs in ovaries, Fallopian tube, or womb; cannot imagine how the Fallopian tube could suck sperm; does not know the ovary's function