Other journals

In the introductory section for every letter, Alle de Brieven / Collected Letters has a list -- "Published in:" -- of other publications in which that letter was re-printed. Except for Leeuwenhoek's self-published volumes, all of these re-printings had less than the complete letter. Most were translations of extracts of translations. Some were summaries. The two noted below seem even less than that, more references to Leeuwenhoek's work in the context of a broader topic. They seem out of place in a bibliography of his published work.

Alle de Brieven / Collected Letters, vol. 2, p. 61 for Letter 18 of October 9, 1676 written to Henry Oldenburg lists under Published in: "S. Blankaart, Collectanea medico-physica. Amsterdam, 1680. Cent. 2. LXXIV. pp. 144-146 and LXXIX. pp. 150-151. (Dutch extract.)"

It's not an extract. Blankaart's (image on right; click to enlarge) summarizes only one of the dozen series of observations that Leeuwenhoek made of little animals in various infusions, this one of pepper in snow water.

Alle de Brieven / Collected Letters, vol. 2, p. 277 for Letter 22 of November 1677 written to William Brouncker lists under Published in: "Chr. Wolff, Experimentaal-philosophie. III. Amsterdam, 1747; pp. 389-390. (Dutch extract.)"

It's not an extract. It's more a reference to Leeuwenhoek's letter with a brief description of the contents, especially the sperm of various animals. The page references Philosophical Transactions number 142, where this letter was published, and number 143, which had no article by Leeuwenhoek.

One more:

Giornale de Letterati was published in Modena by Benedetto Bacchini from 1692 until 1698. One of the early monthly issues had the last part of Letter 26 of September 27, 1678 translated into Italian. This letter, about sweat and saliva, was not published in Philosophical Transactions. Being one of the first 27 letters, it was not included in Leeuwenhoek's own publications, which began with Letter 28. The original manuscript is still in London, so it's not clear how or why it made its way to Modena. It had no figures.

In WorldCat, this journal is held by only one library and it has not been scanned. If the editors of Alle de Brieven / Collected Letters found it, there may well be other publications that re-printed a Leeuwenhoek letter, as a letter, as opposed to mentioning his work in the context of a discussion. That list of publications referring to Leeuwenhoek would be much longer than the dozen or so publications on the right sidebar menu.