Wrote Letter 33 of 1680-11-12 (AB 65) 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

November 12, 1680
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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 manuscript on seventeen quarto pages, written and signed by Leeuwenhoek, is preserved along with both figures at the Royal Society (MS. 1881. L 1. 62). It had eight drawings.


The original drawings are preserved by the Royal Society. Two of these figures were drawn in ink, Fig. 6 the common fly and Fig. 8 the sphere to show proportion. The rest were drawn in red chalk. The Dutch and Latin editions that Leeuwenhoek published used the same plates.

In their first appearance, Onsigtbare geschapene waarheden, was published by Gaesbeeck in 1684. All eight figures were placed in the text where Leeuwenhoek discussed them, even Figs. 1 and 8, which could easily have filled a page themselves. However, for the 1695 first edition of Arcana Naturae Detecta, published by Kroonevelt, Figs. 4 and 5 were combined on one plate inserted on a separate unnumbered page between pages 18 and 19.

In the text, Leeuwenhoek noted that he drew the first two, Figs. 1 and 2.

I also slanted the glass tube at least as much as I have figured here.

I have drawn these vessels the size I observed them in my microscope.

The next two figures required drawing skills beyond Leeuwenhoek's.

Not knowing whether these insects are known in your country I ordered a drawing to be made of them, and on the other hand also because the copulation of these animals seemed strange to me, for while one during the copulation moved onward on its legs the other was dragged along on its back. In fig. 3 ABCD is the male during copulation, D being the genitals, which ought to have been drawn in somewhat closer union. EDFG is the outline of the female.

And because I do not know whether these animals are found in your country I have had a drawing made of them, fig. 4 ABC being the female and CDE the male, sticking together while they flew.

He drew the next one, Fig. 5:

I have also drawn one of them in fig. 5 AB, which, being dead, had kept the curves which it had used in its progress.

If Figs. 3 and 4 were beyond his skills, so was Fig. 6, though he did not say explicitly that he had it drawn. He did not say anything about Figs. 7 and 8 either, though neither was beyond his skills.