Wrote Letter 29 of 1680-01-12 (AB 54) to Robert Hooke about the structure of wood and sperm in fish

January 12, 1680
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This letter on ten quarto pages, written and signed by Leeuwenhoek, is preserved by the Royal Society (MS. 1878. L 1. 49).

The text of the letter in the original Dutch and in English translation from Alle de Brieven / The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren.


The original drawings are preserved at the Royal Society. The Dutch and Latin editions that Leeuwenhoek published all used the same plates. This letter had so many figures, that Leeuwenhoek had them engraved on two plates (left; click to enlarge). They and the figures on the sidebars came from the 1686 first edition of Levende Dierkens. In the text, Leeuwenhoek noted that he drew the figures.

G. van Iterson discussed these figures in an essay (available online in both Dutch and English) appended to Alle de Brieven / Collected Letters vol. III (1948) and noted under Publication history above.

Plates from
Levende Dierkens

Figures 1 - 9

Figures 10 - 20

In these early letters, Leeuwenhoek was still learning how to integrate his text and the figures illustrating it. In the manuscript (and thus in Alle de Brieven / Collected Letters), this letter had a confusing numbering system that probably reflected the process by which the manuscript was written and the figures were drawn. Instead of numbering the figures consecutively, Leeuwenhoek numbered the plates and then the figures. The plates had consecutive numbers, but the figures were always Fig. 1., Fig., 2, and sometimes Fig. 3 and Fig. 4. In the text, however, he referred to it only by figure number. For example, Fig. 17 and Fig. 18 in the printed versions (right sidebar) are No. 7 Fig. 1 and Fig. 2 on the original drawing (right; click to enlarge) and explanatory text. Thus, the text is full of Fig. 1's and Fig. 2's without reference to a plate within sight of the reference to the figure.

... in the manuscript

At the end of a letter to Hooke three months before this one, October 13, 1679 (AB 51), Leeuwenhoek wrote:

I have made drawings of oak-, elm-, beech- and boxwood of deal and black Mauritius ebony, with the vertical and horizontal vessels. I will forward these to you together with some other observations if they should be of any service to you and the Learned Philosophers.

These drawings are on the sidebars. Leeuwenhoek noted in the text that he drew the most simple Figs. 1, 2, and 5. Of Fig. 2 (Fig. 1 in manuscript), he wrote:

Though not at all a great draughtsman, I have put the aspect of the wood to paper in red chalk to the best of my ability. I had a copy made in black chalk by another man, but when I tried to print it, I made the paper a little too wet and thus mostly spoiled it. Though the copy was very accurate, I yet send you enclosed my red-chalk drawing.

He probably also drew the "naked eye" pieces of wood, all of which were drawn in ink: Figures H and E and both Figures F. The other figures, all in red chalk, were well within Leeuwenhoek's limited skills.

Fig. 1 ABCD shows a piece of oak, drawn by me as well as possible through one of my microscopes.

Referring to Fig. 4, he wrote:

But in many places I have drawn them in their full length with curved divisions.

He also made a comment about his microscopes.

The second sort of vertical vessels, which are much smaller also consist of very thin films, pitted with particles, which, through an ordinary microscope, appeared to me like globules.

He did not need his most powerful lenses for most of the things he looked at. For something like these pieces of wood, an ordinary lens (een gemeen microscope) was sufficient.

... in Philosophical Transactions

The next version of this letter, in Philosophical Transactions volume 13 number 148, was published in England on June 10, 1683. The figures were all on one plate, made from these drawings. The text was extracted and translated, during which process, the numbering was made much less confusing. It is still a challenge to say exactly how many figures there are.

  • Five of the figures were labeled with letters only, not numbers. Four of them are tiny, drawn in ink probably by Leeuwenhoek.
  • Figure G, seems to be part of Figure 10, which already has a naked-eye size Figure F.
  • Figure 3 has an A, which is discussed with Figure 2, and a B, which is discussed with Figure 7. Fig. 3B is not in the manuscript but it is in all of the printed versions, including Philosophical Transactions.

Alle de Brieven / Collected Letters says that this manuscript was accompanied by 25 drawings. On Lens on Leeuwenhoek, the four naked-eye drawings accompany their enlargements -- Figures 2, 6, 8, and 10 -- to preserve the sense of scale. Figure G is separate and Figure 3A and Figure 3B are separate figures. In the manuscript, an unnumbered figure and its explanatory text came after Leeuwenhoek's signature, perhaps an afterthought.

Thus, there are 22 figures on the two sidebars from the first edition of Levende Dierkens.

... in Leeuwenhoek's Dutch and Latin editions

In 1686 and 1687, the Dutch and Latin editions of this letter used the numbering system from Philosophical Transactions, not from the manuscript. Presumably, Leeuwenhoek gave a fair copy of the Dutch manuscript to Cornelis Boutesteyn's typesetter, probably in Leiden. Whether the re-numbering was done by Leeuwenhoek or the typesetter, we do not know. As in all of Leeuwenhoek's letters for which we have manuscripts, the spelling and punctuation were changed for the printed edition, though we do not know by whom or when during the process. The timing of the Latin translation is a further mystery.


  • Plate No. 8 Fig. 1 in the manuscript was Fig. 19 in Philosophical Transactions and Levende Dierkens.
  • The unnumbered figure and text at the end of the manuscript was moved to the beginning of the printed texts and numbered Fig. 1. Leeuwenhoek's Fig. 1 then became Fig. 2, etc.
  • In the manuscript was a fraction, 1/9, that was changed to 1/4 in both Philosophical Transactions and Levende Dierkens. Alle de Brieven / Collected Letters (Vol. 3, p. 161) has a footnote: "1/9 is a slip of the pen for ¼, corrected in the printed editions." I can see how Leeuwenhoek would catch that slip and in 1686 tell Boutesteyn to change it. But how did he tell the editors in London in 1683?

So in 1680, Leeuwenhoek sent the manuscript to London. But neither printed version followed it. Was there another copy of the manuscript?