LETTERS 92 AND 96. 1695 207 
No doubt these animalcules were protozoa: and it should 
be mentioned that Leeuwenhoek had recorded a similar 
observation at an even earlier date. Writing to the Royal 
Society about fifteen years before, he mentioned’ that he had 
found “ divers kinds of little living animalcules”’ in the juice 
of mussels and oysters: but he gave no further account of 
them, and it is impossible to ascertain what sort of organisms 
these were. It should also be noted here, however, that in a 
much later letter* he expressed the opinion that some of the 
‘“animalcules”’ which he thought he saw formerly in the juice 
of oysters were probably not really organisms at all, but 
“particles”? set in motion by the cilia on the tissues of the 
molluse.® 
Leeuwenhoek’s last recorded observations on the “ animal- 
cules” in infusions are contained in a letter written several 
years later, and sent not to the Royal Society but to the 
Elector Palatine. This very interesting letter runs as follows’: 
In my letter of 18 September’ [1695] I ventured most 
respectfully to describe how I opened a Freshwater 
Mussel° and took out of it the unborn young mussels,’ 
* Letter 30. 5 April 1680. To Robert Hooke. MS.Roy.Soc. Published 
in Brieven, Vol. I, p.33 (1st pagination): Opera Omnia, Vol. I, p. 25 (2nd 
pagination): English abstract in Phil. Trans. (1693), Vol. XVII, No. 196, 
p. 593. 
* Letter dated 10 June 1712. To the Royal Society. MS.Roy.Soc. 
English version printed in Phil. Trans. (1712), Vol. XXVII, No. 336, p. 529. 
Not published elsewhere, and not numbered by L. himself. 
* It seems to me probable that L. was here referring to the observations 
contained in Letter 30, and not to those in Letter 92, which appears to record 
a genuine observation of protozoa. 
* Letter 96. 9 November 1695. To the Elector Palatine. Published 
in Brieven, Vijfde Vervolg, p. 156: Opera Omnia, Vol. II (Contin. Arc. Nat.), 
p.30 (2nd pagination). Not translated by Hoole. No MS., and not in 
Phil. Trans. I translate the whole letter, with the exception of a few 
immaterial words at the beginning and end. 
° Letter 95, printed immediately before the present letter in L.’s published 
works. 
* Veen-Mossel (literally ‘‘ fen-mussel’’) — Anodonta: not easily recog- 
nizable in the Latin version, where it is called “ concham ex genere earum 
quae ex fossis capiuntur.”’ Veen means not only a fen, marsh, or bog, but 
also the peat which can be dug out of such places: and consequently Hoole 
(Vol. I, p. 85 sq.) translates veen-mossel as ‘ peat-muscle.’”’ But Anodon was 
never known by this name in England—so far as I am aware. 
" i.e., the “ Glochidia ’”’ larvae—described and figured in Letter 95. 
